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Battery

Heat

H2

CH4

Assessment

SyntheticFuels Hydrogen

Hotel Vatel, Martigny, Switzerland

Book of Abstracts

Heat & Electricity Storage

6th Symposium

October 25, 2017

The Mission The Swiss Competence Center for Energy Re-search (SCCER) “Heat and Electricity Stor-age” (HaE) is one of eight centers, which have been established in the research fields of mobility (SCCER Mobility), efficiency (SCCER FEEB+D, SCCER EIP), power supply (SCCER SoE), grids (SCCER FURIES), biomass (SCCER Biosweet), energy storage (SCCER HaE), as well as econo-my and environment (SCCER CREST) in light of the Swiss Government’s Energy Strategy 2050.

The declared aim of this energy strategy is the transition from nuclear power to a power supply system based on renewable sources to meet the CO2 emission targets. An important factor is to expand and strengthen the knowledge in the en-ergy field through the increase of personnel re-sources, e.g., scientists, engineers, technicians alongside with technology development. The cen-ters are organized as virtual consortia of industrial and academic institutions (cantonal universities, federal universities, federal research centers and universities of applied science) distributed all across Switzerland with the intention to maximize the outcome by combining the strongest compe-tencies in each area of expertise.

To maintain a long-lasting effect on the Swiss power supply system, the competence centers will receive financial support until 2020.

Energy storage is a key element in this venture since energy, sourced from renewable sources like wind, sun or tidal energy is only available on a stochastic basis, therefore the aim is to store the surplus energy during times of low demand and release during times of high demand.

With an increasing contribution of the aforemen-tioned renewable energy sources to the electricity mix, the significance of energy storage increases. This is clearly demonstrated by countries that have installed a lot of wind power, e.g., Germany and Denmark. Large intermittent discrepancies between electricity production and demand are being observed with the consequence of strongly fluctuating electricity prizes.

These differences are a challenge to the stability of the power supply system. In order to stabilize the grid, an increase in short term electricity stor-age capacity (hrs) with high response time is needed within the next years. In the long run, sea-sonal storage becomes important to ensure con-stant electricity supply without conventional fossil based power generation.

Heat, aside from electricity is one of the most re-quired type of energy today. About 50% of the pri-mary energy carriers are transformed to heat by modern industrialized societies required for space heating, hot water and process heat. Thus, it be-comes obvious that a sensible use of energy must not neglect the questions related to heat.

In summary it can be stated that energy storage will become increasingly important in the future.

The research and development within the Com-petence Center for Heat and Electricity Storage concentrates on five different fields with the in-volvement of more than 20 research groups from eleven public institutions as well as from the pri-vate sector.

The research includes traditional approaches like the future development of battery systems, but also on novel approaches like heat storage or power-to-gas concepts.

We would like to invite you to learn more about the different area of research on the following pages and during this symposium. For further in-formation, or if you are interested in a collabora-tion, you may contact us any time, or check our web page (www.sccer-hae.ch) for news and events.

Prof. Dr. Thomas J. Schmidt

Head SCCER Heat and Electricity Storage

SCCER Heat and Electricity Storage c/o Paul Scherrer Institut OVGA 05 5232 Villigen PSI

[email protected] www.sccer-hae.ch

Heat & Electricity Storage 6th Symposium

We thank the following industrial and cooperation partners:

09:00

10:00 Welcome Prof. Dr. Thomas J. Schmidt, Head SCCER HaE, CH

10:05 Address Speech Anne-Laure Couchepin, Ville of Martigny, CH

Prof. Dr. Andreas Züttel, EPFL, Sion, CH Dr. Noris Gallandat, GRZ Technologies, CH

10:45 Catalyst Design for the Electrochemical CO2 Conversion

11:10Powering Progress Together -Providing Energy Storage Solutions for a Changing World

Prof. Dr. Peter Broekmann, Uni Bern, CH

11:35

12:35

13:35 The All-Organic Redox Flow Battery Dr. Olaf Conrad, JenaBatteries GmbH, D

Prof. Dr. Axel Fuerst, Berner Fachhochschule, CH Dr. Pascal Häring, Renata, CH

14:25 Thermal Energy Supply and Storage in Energyhub and NEST Dr. Luca Baldini, Empa, CH

Prof. Dr. Andreas Haselbacher, ETHZ, CH

Gilles Verdan, GazNat, CHDr. Noris Gallandat, EPFL, Sion, CH

Prof. Dr. Markus Friedl, HSR, CHEnergy Storage Demonstrators within SCCER Heat and Electricity Storage

Prof. Dr. Thomas J. Schmidt, Head SCCER HaE, CH

16:10

16:20

Registration and Coffee

Fairwell Coffee

Excursion to Electromobilis

15:15

14:50

14:00 Battery Production Research for Switzerland

10:20 Hydrogen and Hydrides, Storage and Compression

Experimental and Numerical Investigation of a Pilot-Scale AA-CAES Plant

Energy Storage and Synthetic Methane

Postersession

Lunch

PhD. Joep Huijsmans, Long Range Research & New Energy Technologies, Shell, NL

16:05 Closing Remark

15:40

..... 15

Oral Presentations Hydrogen and Hydrides, Storage and Compression ............................................................................................................................................... 1 Catalyst Design for the Electrochemical CO2 Conversion ....................................................................................................................................... 2 Powering Progress Together – Providing Energy Storage Solutions for a Changing World .................................................................................... 3 The All-Organic Redox Flow Battery ....................................................................................................................................................................... 4 Battery Production Research for Switzerland .......................................................................................................................................................... 5 Thermal Energy Supply and Storage in Energyhub and NEST .................................................................................................................................. 6 Experimental and Numerical Investigation of a Pilot-Scale AA-CAES Plant ............................................................................................................. 7 Energy Storage and Synthetic Methane ................................................................................................................................................................... 8 Energy Storage Demonstrators within SCCER Heat and Electricity Storage ............................................................................................................. 9

Posters Thermal Energy Storage Investigation of AA-CAES Plant Configurations and Grid Integration .................................................................................................................... 13 AA-CAES Plant Modeling and Validation against the Pollegio Pilot Plant Data ...................................................................................................... 14 Numerical Topology Optimization of a High-Temperature Energy Storage made of Metal Phase Change Materials in Cylindrical Encapsulations

Heat Storage for Enhancing the Use and Performance of Automotive Catalytic Converters .............................................................................. 16 Designing, 3D Printing And Testing of SiSic Porous Structures .............................................................................................................................. 19 Sorption-based long term thermal energy storage using sodium hydroxide ......................................................................................................... 20 Seasonal Thermal Energy Storage with Aqueous Sodium Hydroxide – Reaction Zone Development ................................................................. 22

Battery and Battery Materials Investigation on the Promising P2-Na0.67Mn0.6Fe0.25Al0.15O2 Cathode Material .......................................................................................... 27 How Reliable is the Na Metal as a Reference Electrode? ...................................................................................................................................... 28 Electrode Nanomaterials for Li-ion Batteries ........................................................................................................................................................ 29 Investigations for a Full Cell Li(Ni1/3Mn1/3Co1/3)O2 (NMC) Benchmark ........................................................................................................... 31 Pilot Production Line for Battery Cell Manufacturing ........................................................................................................................................... 32 Electrode Foils Cutting Studies with Fiber Laser Unit ............................................................................................................................................ 34 MoS2 Lamellar Membrane for Selective Molecular Transport, HER and its Application in Li Water Battery ....................................................... 36 Rechargeable Li-Air and Li-Water Batteries .......................................................................................................................................................... 37 Nano Structured Nickel Electrodes for Ultra-High Power Aqueous Double .......................................................................................................... 39 Non-Aqueous Copper Battery for Heat-to-Power Conversion and Storage .......................................................................................................... 40

Hydrogen Generation Hydrogen Storage Synthesis and Characterization of Core-Shell Structure of NaBH4 for Hydrogen Storage .................................................................................... 43 Efficient Electrodes Based on Stainless Steel for Water Oxidation........................................................................................................................ 44 Inkjet Printing of Electrocatalysts and Electrocatalyst Gradients in 2D and 3D for the ORR and OER .................................................................... 45 Formic Acid : A Viable Option to Chemical Hydrogen Storage ............................................................................................................................... 46 Formic Acid on the Way to an Industrial-scale Energy Storage Vector .................................................................................................................. 47

Synthetic Fuels Behavior of Sputter Deposited Thin Films of Cu and Cu Oxide towards CO2 Electroreduction ........................................................................... 51 CO2 Hydrogenation of Copper Nanoparticles Supported on Zirconium Modified Silica ..................................................................................... 52 Surface-Supported Cu-based Catalysts towards CO2 Conve rsion ......................................................................................................................... 53

Indirect MeOH Production from CO2 via Cyclic Carbonates under Solvent-Free, Metal-Free Conditions ........................................................... 54 Triazolium and Pyrazolium Ionic Liquids for Electrochemical Reduction of CO2 ................................................................................................... 55 Role of the Initial Amount of Hydrogen and CO2 for Successful CO2 Reduction to Hydrocarbons .................................................................... 56 Methanation Reactor Design and Operation for Methane Production using Sabatier Process .......................................................................... 57

Assessment of Storage Systems . Optimization of Residential PV-coupled Battery Systems with Stacked Benefits: a Cross-country Comparison. .................................................. 61 HEPP High Efficiency Power-to-Methane Pilot...................................................................................................................................................... 62

List of Participants only in paper copy

Oral Presentations SCCER Heat & Electricity Storage 6th Symposium

Hydrogen and Hydrides, Storage and Compression

A. Züttel*1,2, N. Gallandat1, M. Spodaryk1, H. Yang1, L. Lombardo1

*[email protected]

1) Laboratory of Materials for Renewable Energy (LMER), Institute of Chemical Sciences andEngineering (ISIC), École polytechnique fédérale de Lausanne, EPFL Valais/Wallis, Switzerland, 2) EMPA Materials Science and Technology, Dübendorf, Switzerland

Until recently the main motivation for the development of energy storage system was the increasing problem with the emission of CO2 and the global temperature increase as well as the limited resources of fossil fuels. However, the current development in China, i.e. the large production of photovoltaic cells and the huge amount of installed renewable power, has changed the global situation. Assuming the exponential growth of the last 10 years in installed photovoltaic continues, the peak power will reach the global energy demand of 18TW in 2025 already (Fig 1). Therefore, the storage and transport of renewable energy is the key technology for the energy turnaround.

Fig.1 Development of the installed peak power for wind (green) and PV (blue) and the extrapolation (left hand side)

Fig. 2 volumetric vs. gravimetric hydrogen storage density in various storage systems (right hand side)

The storage of renewable energy for mobility and for seasonal energy transfer are the major challenges. While hydrogen storage reaches the highest gravimetric energy density (Fig. 2) for a fuel the hydrocarbons are high in gravimetric and volumetric energy density. Furthermore, in view of economic measures, batteries cost around 200 €/kWh, hydrogen costs 0.25 €/kWh and synthetic hydrocarbons around 0.3 €/kWh. Hydrogen absorbed in hydrides exhibits almost twice the density of liquid hydrogen is at moderate pressure and can be stored over a long time without any loss. The research on hydrogen storage focuses on new materials consisting of light weight elements and high hydrogen density. With the discovery of the complex hydrides, i.e. alanates [1] and the borohydrides [2], as storage materials the potential gravimetric hydrogen density was increased by an order of magnitude. However, in contrast to metal hydrides the complex hydrides decompose in multiple phases upon hydrogen desorption. The control of the reaction on the nanoscale becomes essential in order to develop a hydrogen storage system based on complex hydrides. Furthermore, a large amount of possible complex compounds spontaneously desorb hydrogen and are liquids at room temperature. We have successfully synthesized and stabilized Ti[BH4]3 by infiltration in a metal organic framework [3], a new way to change the stability by means of interaction with nanomaterials. Beside the investigation of host materials for hydrogen our research also includes the reduction of CO2 with hydrogen in order to produce a specific hydrocarbon with a catalyzed and highly selective reaction. The main advantage of hydrocarbons is they are easy to store and exhibit an energy density twice as high as the hydrides. References: [1] B. Bogdanovic, M. Schwickardi, “Ti-doped alkali metal aluminium hydrides as potential novel

reversible hydrogen storage materials”, Journal of Alloys and Compounds 253, 1-9 (1997) [2] A. Züttel et al., “LiBH4 a new hydrogen storage material”, Journal of Power Sources 118 (2003),

pp. 1–7 [3] E. Callini, P. Á. Szilágyi, M. Paskevicius, N. P. Stadie, J. Réhault, C. E. Buckley, A.

Borgschulte and A. Züttel, " Stabilization of volatile Ti(BH4)3 by nano-confinement in a metal–organic framework", Chemical Science, 7, 666 – 672 (2016)

SCCER HaE 6th Symposium

October 25, 2017 1 Martigny

mailto:[email protected]

Catalyst Design for the Electrochemical CO2 Conversion

A. Dutta, M. Rahaman, A. Zanetti, C. Morstein, N. Schlegel, A. Kuzume, S. Vestergom, B. Kaliginedi, A. Rudnev, and P. Broekmann*

*[email protected]

Department of Chemistry and Biochemistry, University of Bern Freiestrasse 3, 3012 Bern, Switzerland

The electrochemical conversion of CO2 into products of higher value can be considered as a seminal approach that has the technological potential of contributing to a closing of the anthropogenic carbon cycle. Such CO2 electroreduction (CO2 RR) offers not only the unique chance to reduce the amount of environmentally harmful CO2 , it provides in addition means of storing intermittently produced excesses of electricity originating from renewables like wind, solar and hydro sources. Major challenges that currently prevent such electrochemical CO2 conversion technology from being implemented into industrial applications are related to the enormous overpotentials needed for CO2 activation, thus typically resulting into a poor energy efficiency of the entire full cell-level process. Among the vast number of materials screened so far, it is Cu which deserves particular attention since it is the only catalyst which is capable to convert CO2 into hydrocarbons and alcohols. Crucial for the performance of the Cu catalysts is their pre-treatment, e.g. by thermal annealing, exposure to oxygen plasma, electrodeposition, and electrodeposition. An additive-assisted metal foam electrodeposition can be considered as a promising approach towards design and production of novel high-surface area CO2 RR catalysts.[1-2] For selected examples, it will be demonstrated that oxide-derived Cu foam catalysts can reach Faradaic efficiencies of up to 25% for the production of highly valuable C2 and C3 alcohols.[3] Identical location (IL) SEM/TEM investigations in combination with operando Raman and EXAFS/XANES measurements clearly prove that the actually active catalyst forms only under reactive conditions during an ongoing CO2 RR.[4] We will further demonstrate that the concept of metal foam electrodeposition is rather versatile and can be extended to other catalyst materials like Ag, Pd and alloys thereof. These CO2 RR catalysts show a superior performance for CO2 RR not only in terms of activity and product selectivity but also with respect to their long term durability and stability.

Fig.1 Identical location (IL) HR-SEM analysis of dendritic Cu catalysts used for C2 and C3 alcohol production.[4]

References: [1] Dutta, A.; Rahaman, M.; Luedi, N. C. ; Mohos, M.; Broekmann, P.; ACS Catal. 2016, 6, 3804-3814 [2] Dutta, A.; Rahaman; M.; Zanetti, A.; Broekmann, P. ; ACS Catal. 2017, 7, 5431–5437

[3] Dutta, A.; Kuzume, A.; Rahaman; M.; Vestergom, S.; Broekmann, P.; ACS Catal. 2015, 5, 7498- 7502

[4] Rahaman, M.; Dutta, A.; Zanetti, A.; Broekmann, P. ; ACS Catal. 2017 (accepted for publication)




Powering Progress Together – Providing Energy Storage Solutions for a Changing World

J. Huijsmans

[email protected]

Shell Global Solutions International B.V., P.O. Box 38000, 1030 BN Amsterdam, the Netherlands

The world must find ways to meet the rising energy demand while reducing global greenhouse gas emissions to limit the effects of climate change. The historic Paris Agreement established a goal to limit the global temperature rise this century to well below 2°C. This reinforces the need to shift our existing energy system to a system based on energy sources that are lower-carbon. It requires a huge undertaking – a global energy transition involves producing and consuming energy in a different way.A successful energy transition requires substantial investment across all energy sources, including oil and gas production, to meet a growing demand for energy.

Electricity is moving from being one of the most expensive energy carriers to that with lowest cost, with solar generation offering highest energy utilization and smallest footprint. There is currently the potential for large scale electrification of the energy system, depending on policy, technology and market developments. In the event large scale electrification of energy supply would happen, new connections will need building – from power to heat and from power to mobility. However, electrification of the energy system is technically not simple, because electricity is relatively difficult to store and transport – this is in particular a problem in dealing with large variations in demand (winter/summer cooling/heating) as well as the intermittency of supply. The expectation is that a molecular energy vector is needed and the simplest solution would be hydrogen. Hydrogen could become an energy vector – linking increasingly electricity based supply with the various demand sectors; while also enabling long distance transport. In principle we could go further – hydrogen can serve as building block to also synthesize liquid fuels – very much needed in commercial transport and air transport as well as chemicals. Solar to energy technologies include: Solar PV*, Solar thermal*, Wind, Hydro, Bio-energy and Solar fuels.




The All-Organic Redox Flow Battery

O. Conrad*

*[email protected]

JenaBatteries GmbH,Botzstraße 5,07743 Jena,Germany

We all know that we need to change some things if we want to preserve our planet. Unfortunately, the average stationary battery system is relying heavily on mining and refining in sensitive habitats and is anything but green. JenaBatteries creates revolutionary organic redox-flow-batteries based on metal- free energy storage materials, salt and water, which reduce the environmental impact and can be manufactured at a much lower cost. The redox-flow-battery systems are based on metal-free storage materials that are produced in bulk already and require only common base chemicals as starting material. They are starting at a capacity of 40 kilowatt hours, but go up to several tens of megawatt hours. Power and capacity are scalable, independently of one another, which makes it possible to tailor the system to the customers’ needs. The battery’s lifespan is above 10,000 cycles and impresses with no self-discharge. The battery is also operable without active cooling between zero to 60 degrees, which again saves costs, especially in warmer countries. The organic redox-flow-batteries can be used in a wide range of sectors such as off-grid applications, micro-grid solutions, island grids, storage of renewable energy, load shifting and peak shaving, emergency and uninterrupted power supply, for e-mobility charging solutions and many more, see figure 1. [1]

Fig.1 Applications for the organic redox flow battery

Renewable Industry, public energy buildings, hotels,

homes, power grids, off-grid solutions …

Scalable battery

References: [1] Stracke M., Discover Germany (54), 9, 2017 , 69




Battery Production Research for Switzerland

A. Fuerst*1, P. Häring2

*[email protected]

1BFH-ESReC, Research group: Manufacturing technologies for battery production, BFH-TI, Switzerland

2Renata SA, Kreuzenstrasse 30, 4452 Itingen, Switzerland

Today, there is a gap between battery material development and system development for Swiss battery manufacturers and research institutions. Therefore, it is not possible to produce an application sized battery cell in a reproducible way at quantities large enough for qualified testing. The development of the pilot line closes this gap.

On the other hand, there is a growing market for batteries for mobile and stationary applications, demanding for large sized battery cells. The production process for those type of cells is by far not optimized in terms of methodology and sometimes it still contains manual steps. Consequently large sized cells are 30% more costly than consumer cells.

An elimination of such inefficient steps and alternative production methods will bring quality improvements and cost advantages. The Swiss manufacturing systems engineering industry, an export oriented economy, benefits from the possibilities to develop and export production equipment for batteries. I.e. Bühler AG has the novelty of continuous slurry mixing. The pilot line developed at BFH (fig. 1) offers the opportunity of process technology development for Swiss industry together with Swiss battery research.

In this talk, the motivation of the activities around the pilot line is discussed and the status of the setup explained.

Fig.1 Layout of the battery manufacturing pilot line.




Thermal Energy Supply and Storage in Energyhub and NEST

L. Baldini*

*[email protected]

Empa Swiss Federal Laboratories for Materials Science and Technology, Laboratory of Urban Energy Systems, Building Systems and Technologies Group

Nest and ehub are both important research and innovation plattforms at Empa campus allowing for studying novel technologies and their system integration in the building sector. Nest with its shelf like construction represents a vertical district holding several experimental buildings. All these buildings feature different novelties on the level of energy systems or construction. These potential innovations will be evaluated in real operation and are exposed to peoole living and working within Nest. As such, Nest is bridging the gap between the lab and the market helping the diffusion of potential innovations into the market.ehub standing for energyhub is hosting a set of energy technologies such as heat pumps, groundheat exchangers, ice storage, batteries and super capacitors, responsible for the energy supply of the district represented by Nest (fig. 1). Further, it connects to the mobility demonstrator move hosting a PV installation, an electrolyser, a hydrogen and electric fuelling station.The ehub allows for researching district energy systems with different technology combinations. Electrical microgrids or thermal district networks can be operated and tested. As such ehub is an ideal plattform for integrating and assessing novel energy storage technologies such as our long term thermal energy storage based on liquid sorption using sodium hydroxide and water. Within the SCCER research activity the lab scale storage will be upscaled and integrated into ehub and Nest in 2020. This integration will allow for testing with real loads and under realistic conditions.

Fig.1 The technologies included in the ehub, and the heat related systems




Experimental and Numerical Investigation of a Pilot-Scale AA-CAES Plant

G. Zanganeh*1, A. Haselbacher#2, V. Becattini2, L. Geissbühler2, S. Zavattoni3, M. Barbato3, A. Steinfeld2

*[email protected]#[email protected]

1ALACAES SA, Lugano, Switzerland 2ETH, Zurich, Switzerland

3SUPSI, Lugano, Switzerland

The growing share of intermittent renewable-energy sources such as wind and solar requires short- and long-term energy storage to guarantee the power supply. At present, pumped hydroelectric storage (PHS) accounts for the majority of bulk storage capacity. The construction of additional plants is hampered by high capital costs and restrictive site requirements. Advanced adiabatic compressed air energy storage (AA-CAES) is so far the only alternative that can compete in terms of capacity and efficiency and has the advantages of lower expected capital costs and less strict site requirements. The basic principle underlying CAES has been demonstrated through the diabatic CAES plants in Huntorf (321 MW, Germany) and McIntosh (110 MW, USA). In these plants, the heat of compression is wasted and must therefore be resupplied prior to expansion, resulting in relatively low cycle efficiencies of about 45-50%. By contrast, in AA-CAES plants, the thermal energy generated by compression is stored in a thermal-energy storage (TES), increasing cycle efficiencies to about 70-75%. In the presentation, the authors will show experimental results from the world’s first pilot-scale AA-CAES plant using a rock cavern and combined sensible/latent TES and compare the results with data from simulations. The pilot plant was built near Biasca in an unused tunnel and demonstrated the technical feasibility of the AA-CAES concept, the use of rock caverns, and the combined TES at high temperatures.




mailto:%[email protected]

Energy Storage and Synthetic Methane

N. Gallandat1, N. Mlynek2, A. Züttel1*

*[email protected]

1 Laboratory of Materials for Renewable Energy, £cole Polytechnique F®d®rale de Lausanne (EPFL) Va-lais/Wallis, Energypolis, Rue de lôIndustrie 17, CH-1951 Sion, Switzerland

2 Gaznat SA, Av. G®n®ral Guisan 28, 1800 Vevey, Switzerland

Two examples of pilot plants for the production of synthetic hydrocarbons are presented. First, the design and build of a demonstrator for the conversion of solar energy to synthetic hydrocarbons is presented. The average power of the installation is set to 2 kW, which corresponds to the global ener-gy consumption of a single person. The main components of the system are photovoltaic cells, batter-ies, an electrolyser, a metal hydride storage and compression system, a CO2 capture unit and chemi-cal reactors. The installation allows studying the energy flows and reservoirs and the interaction be-tween different components, comparing the performance of competing technologies and establishing an energetic and economic database from the real world. Further, the operating parameters such as pressure, temperatures and energy flows are recorded at different locations to enable for system modeling and advanced optimization techniques to be applied on real data. Last, the degradation of the various components will be investigated under actual working conditions [1]. The second pilot plant aims at improving to overall energetic efficiency of gas metering and regulating stations positioned as interface between the transmission (50-80 bar) and distribution (5 bar) grids. The goal of this project is to combine the use of renewable waste heat with the production of synthetic methane in order to par-tially replace the conventionally used natural gas boiler. Waste heat from the electrolyser and the chemical reactor is recovered to pre-warm the incoming stream of natural gas prior to the expansion. The proposed system not only prevents the consumption of natural gas, but instead produces synthet-ic, renewable methane. Further, CO2 is consumed instead of being produced. It is calculated that CO2 emission in the amount of around 37.3 Tons will be avoided yearly.

Figure 1: Layout of the Small Scale Demonstrator Plant at EPFL Valais/Wallis in Sion.

References: [1] N. Gallandat, J. Bérard, F. Abbet, and A. Züttel, “Small-scale demonstration of the conversion of

renewable energy to synthetic hydrocarbons,” Sustain. Energy Fuels, 2017.




Energy Storage Demonstrators within SCCER Heat and Electricity Storage

M.J. Friedl, S. Moebus*

*[email protected]

HSR Hochschule für Technik Rapperswil

There are four Power-to-Gas demonstrators integrated in SCCER HaE phase ll, listed in table 1. The involved four academic groups work on the same objective, which is to design improved power-to-gas systems using state-of-the-art technologies and to bring them to TRL 6.

In 2017, the academic partners designed, ordered and installed their research equipment. Several meetings were organized in order to exchange the experience and preliminary results. It is planned to compare the demonstrators with each other. Results are expected as from 2018.

As a perspective for the end of the SCCER HaE phase ll the academic partners involved in WP5.4 will jointly release their results, especially on the specific efficiencies of their Power-to-Gas technology. For this purpose, it is expected to follow a harmonized assessment protocol suggested in a forthcoming publication [1] and to combines it with scientific research of Life Cycle Assessment of Power-to-Gas technologies [2].

Table.1: Energy Storage Demonstrators and involved academic groups

Academia Demonstrator Objective Staff

HSR Hochschule für Technik Rapperswil

HEPP High Efficiency Power-to-Methane Pilot

Implementing High Temperature Electrolysis to Power-to-Methane systems.

Markus Friedl, Luiz De Sousa, Sandra Moebus

EPFL Vallais, Martigny

Grid to mobility Demonstrator

Better understanding chain between grid and/or renewable energy and electrical vehicles.

Hubert Girault, Heron Vrubel, Véronique Amstutz

EPFL Vallais, Sion

Small-Scale Demonstrator Sion

Examining technical feasibility of the conversion from renewable energy to synthetic hydrocarbons

Andreas Züttel, Noris Gallandat

PSI Paul Scherrer Institut

Energy System Integration Platform (ESI)

Research and technology transfer for SCCERs HaE and BIOSWEET.

Peter Jansohn, Marcel Hofer, Tilman Schildhauer

References: [1] E. Frank; J. Gorre, F. Ruoss; M.J. Friedl (forthcoming). Submitted to Applied Energy Journal, 2017. [2] X. Zhang; C. Bauer; C. L. Mutel; K. Volkart. Applied Energy Volume 190, 2017, 3, 326-338




Posters SCCER Heat & Electricity Storage 6th Symposium

Thermal Energy Storage


Investigation of AA-CAES Plant Configurations and Grid Integration P. Roos*1, G. Zanganeh2, J. Roncolato3, M. Barbato3, J. Garrison4, T. Demiray4,

A. Haselbacher1, A. Steinfeld1

*[email protected]

1Professorship of Renewable Energy Carriers, ETH, Switzerland 2ALACAES, Switzerland

3Department of Innovative Technologies, SUPSI, Switzerland 4Research Center for Energy Networks, ETH, Switzerland

During Phase I of this SCCER project the technical feasibility of an advanced adiabatic compressed air energy storage (AA-CAES) was shown during experiments performed in a pilot plant.[1] Phase II aims at proving profitability of an AA-CAES plant integrated into the Swiss electricity grid. To predict the profitability, a techno-economic and environmental analysis of the entire plant will be performed. This includes component and plant modelling as well as electricity grid simulations that model the anticipated future market conditions.

A plant site study is ongoing where the suitability of decommissioned military caverns as compressed air storage reservoirs is analyzed. These caverns could be of interest due to their general geological stability as well as the inherently decreased plant site construction costs due to an already existing storage volume as well as a first access path. The two most important requirements for the cavern site are proximity to a grid connection as well as the existing volume of the air storage reservoir. Figure 1 shows a map of a first set of cavern sites as well as the electricity grid nodes. A first evaluation of the data shows that there are possible candidates that could be used for an AA-CAES application.

Fig.1 Map of plant site study for decommissioned military caverns and electricity grid nodes.

References: [1] Geissbühler, L.; Becattini, V.; Zanganeh, G.; Haselbacher, A.; Steinfeld, A. SCCER HaE-Storage – Annual Activity Report 2016: Sensible and Combined Sensible/Latent- Heat Thermal Energy Storage for Advanced Adiabatic Compressed Air Energy Storage, pp. 5-6, 2016.




AA-CAES Plant Modeling and Validation against the Pollegio Pilot Plant Data

J. Roncolato*1, A. Pizzoferrato1, V. Becattini2, A. Haselbacher2, G. Zanganeh3, M.C. Barbato1

*jonathan.roncolato @supsi.ch

1MEMTi,SUPSI - DTI, Switzerland2ETH Zürich, Switzerland

3ALACAES SA, Switzerland

A numerical model of an Advanced Adiabatic Compressed Air Energy Storage (AA-CAES) was developed in Matlab-Simscape taking into account temperature dependent properties of air, dynamics of the cavern, efficiency maps for compressor and turbine together with realistic power ramps for start and stop of these components. A 1D Fortran code developed by ETHZ is embedded in the AA-CAES model in order to accurately describe the thermocline evolution within the TES according to the plant operation and considering the detailed storage structure and the heat storage materials, which can be based on both sensible and latent media. The model was validated against the experimental data gathered from the pilot plant built in Pollegio, near Biasca (Ticino), by ALACAES SA.

Fig.1: Overview of the AA-CAES model implemented in Simcape. In an AA-CAES plant, electrical energy is used to compress air in the compressor train. Subsequently, the high temperature air enters the TES where, before being stored in the cavern, its thermal energy is removed. During the discharge, air flows from the cavern through the TES and then expands in the turbine moving the generator and producing electrical energy.





Numerical Topology Optimization of a High-Temperature Energy Storage made of Metal Phase Change Materials in Cylindrical Encapsulations

N. Mallya*, S. Haussener

*[email protected]

Laboratory of Renewable Energy Science and Engineering, EPFL, 1015 Lausanne, Switzerland

Highly conductive, high melting point (above 400°C) metal alloys can be used for high energy and power density latent heat storage. We aim at developing a tool for the numerical structural optimization of a latent heat storage device with accurate phase-change modeling in order to control the limiting convective heat transfer rate from the heat transfer fluid (HTF) to the encapsulated phase change materials (PCMs) and to design heat storage devices with tailored energy and power density. The use of a Genetic Algorithm (GA) in the field of heat exchangers to optimize pressure drops and heat exchange is well known[1,2] but has not been utilized with full-scale CFD and melting simulations for optimizing heat storage systems.

We developed 2D melting-solidification simulations in Fluent using the enthalpy-porosity method [3,4,5] to predict the movement of the melt interfaces. The metal is assumed to be homogeneous and isotropic, and the molten fluid is assumed to be a laminar, Newtonian fluid without viscous dissipation. A multi-objective binary coded GA coded in MATLAB was used for optimizing multiple geometric and thermodynamic parameters – for example maximizing heat transfer rate or obtaining a constant exit flow temperature – depending on the application’s requirements and constraints. The GA uses roulette selection[6] (the probability of being chosen for production of offspring is based on the fitness score) and elitism[6] (including the parent and offspring populations in the same mating pool) to reach a specified or optimum value of the parameter to be optimized. The radii within the ranges permitted are coded in binary for easier crossover and mutation.

Fig.1 (a) Melting and flow simulation in cylindrical storage tubes showing Al12Si as the PCM and air as the HTF being optimized using GA for increasing heat transfer rate by changing the radii of the

For maximizing the heat transfer rate, the results confirm that the convective heat exchange between the HTF and PCM encapsulations is limiting. The results of the GA applied to PCM encapsulated in cylindrical pipes will be used to build an industrial heat storage unit with a specific energy density, charging-discharging rate, and constant temperature discharge. The developed model provides a tool for designing heat storage units with the required specifications.

References: [1] Hilbert, R.; Janiga, G.; Baron, R.; Thévenin, D. Int. J. Heat and Mass Transfer 2006, 49, 2567- 2577[2] Dias Jr, T.; Milanez, L.F.; Int. J. Heat and Mass Transfer 2006, 49, 2090-2096. [3] Brent, A. D.; Voller, V. R.; Reid, K. J. Numerical Heat Transfer 1988, 13, 297-318. [4] Shamsundar, N.; Sparrow, E. M. ASME J. Heat Transfer 1975, 97, 333-340. [5] Voller, V. R.; Prakash, C. Int. J. Heat and Mass Transfer 1987, 30, 1709-1719. [6] De Jong, K.A. Diss. Abst. Int. 1975, 36.

tubes. (b) An almost constant (±1K) exit flow temperature can be observed.




Heat Storage for Enhancing the Use and Performance of Automotive Catalytic

Converters C. Suter*, D. Hade, J. Schnidrig, N. Ter-Borch, S. Haussener

*[email protected]

Institute of Mechanical Engineering, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne,

Switzerland

Fossil fuel driven cars are equipped with catalytic converter in order to reduce exhaust gas emissions by 95% [1]. Catalytic converters are fully functional only when the operational temperature is higher than the light-off temperature of the catalytic reaction (around 300°C). Thus, 50 – 80% of all emissions occur during cold starts, which describes the period of 2 to 5 minutes after starting the engine till the catalytic converter reaches the light-off temperature. To meet future exhaust gas regulations various methods have been proposed: (i) secondary air injection at the exhaust gas valve during cold start period increasing the air-fuel ratio and therefore the exhaust gas temperature; (ii) an auxiliary second catalytic converter placed upstream to the main catalytic converter, thus reaching light-off temperature earlier; or (iii) an electric system to pre-heat the catalytic converter before starting the engine. All methods show drawbacks related to technical feasibility (i/ii) or extra weight and increased requirement for the battery capacity (iii) [2,3]. A novel approach is the usage of a phase change material (PCM) mantel around the catalyst serving as heat storage, charged by the hot catalytic converter during the operation of the car and discharged during the standstill of the car. This configuration allows the delay of the cool-down time of the catalytic converter below the light-off temperature, i.e. it increases the available stop time while a warm start is still possible.

In the present work, we have investigated as example car a Fiat Punto 1.4 BiPower comprising a 1.4- litre 4-cylinder 57kW gasoline engine and a three-way catalytic converter (TWC) yielding a maximum speed of 165 km/h. A numeric heat transfer model coupling convection between the exhaust gas and catalytic converter’s honey comb structure with conduction/convection between the catalytic converter, PCM mantel, insulation and environment has been implemented and validated in terms of experimental data provided by EMPA (Automotive Powertrain Technologies group, Thomas Bütler). The schematic cross-section containing the cylindrical catalytic converter (black/white) with the honeycomb structure having radius rCAT = 5 cm, the PCM layer (red) having a thickness δPCM = 1 – 10 cm and the Al2 O3 insulation (blue) with a thickness of δINS = 4 cm is shown in Fig. 1a. The lumped parameter model approach using uniform temperatures for the catalytic converter (Tcat), PCM mantel (TPCM ) and insulation (TINS ) as well as for the exhaust gas (Tgas ) and ambient air (Tamb) is depicted in Fig. 1b. The thermal behavior of the PCM material has been simplified using the enthalpy method [4]. Three different types of PCM materials have been considered, which are Al-65wt%-Cu-30wt%Si-5wt% (Al-Cu-Si), Al-54wt%Cu-22wt%Mg-18wt%-Zn-6wt% (Al-Cu-Mg-Zn) and Al-59wt%-Mg-35wt%Zn-6wt% (Al-Mg-Zn) having melting temperatures of 571°C, 520°C and 443°C, respectively. Their thermal properties are shown in Table 1 [5]. For various car speeds (ranging from 30 – 120 km/h) and driving cycles, a parametric study has been performed to determine the influence of the PCM material and the PCM layer thickness on the delayed cool-down time of the catalytic converter, Δtc,300 , which is defined as the time gain in the discharge cycle between the time elapsed till the PCM catalytic converter temperature drops below the light-off temperature compared to the one of a reference catalytic converter without PCM/insulation.

Fig. 2 (a) shows an example run for a driving cycle consisting of driving at 80 km/h for t = 0 – 40 min and resting for t > 40 min. The PCM material is Al-Cu-Si with a thickness of δPCM = 5 cm. The temperature is plotted as a function of time for the exhaust gas Tgas , the PCM catalytic converter TCAT,PCM , and the reference catalytic converter TCAT,ref . When the car stops the temperature of the reference catalytic converter drops below light-off temperature within approximately 1.5 min whereas the PCM-mantled catalytic converters last for almost 60 min. The delayed cool-down time is indicated by a double arrow, which is Δtc,300 ≈ 60 min. Fig. 2 (b) depicts the required PCM layer thickness as a function of the delayed cool-down time of the catalytic converter showing a quasi-linear and similar




behavior for all three PCM materials. For δPCM = 10 cm the Al-Cu-Si configuration shows the largest Δtc,300 = 114 min due to the combination of the highest specific latent heat (422 kJ/kg) and the rather high density (2730 kg/m3) whereas the Al-Mg-Zn configuration shows the shortest Δt c,300 = 96 min due to the lower specific heat (310 kJ/kg) and the low density (2380 kg/m3). For a PCM thickness δ PCM = 1 cm the delayed cool-down time ranges from 7 – 10 min. As a drawback, the Al-Cu-Si configuration is not suitable for low car speeds (30 km/h) as its melting temperature (571°C) is higher than the exhaust gas temperature.

As a conclusion, PCM mantled catalytic converters show a high potential as the cool-down time can be delayed for reasonable PCM layer thicknesses, i.e. Δtc,300 ≈ 60 min and Δtc,300 ≈ 120 min for δPCM = 5 cm and δPCM = 10 cm, respectively (corresponding to an additional weight of 3.2 kg and 8.6 kg, respectively). The limiting factor of a PCM catalytic converter is the layer thickness. Thus, the extension of the cool-down time to long-term parking (e.g. over night) is not feasible. The design of the PCM mantel, i.e. the choice of the PCM material and the appropriate thickness, has to be well matched to the entire vehicle taking into account the operation conditions as driving cycles resulting in a trade-off between optimizing the maximum delay of the cool-down time and minimizing the additional weight imposed by the PCM mantel.

Fig. 1 a) schematic cross-section of catalytic converter (black/white) with the honeycomb structure, the PCM layer (red) and the insulation (blue) with the respective radius/thicknesses; (b) lumped parameter model with the respective radius/thicknesses and temperatures Tcat, TPCM and TINS as well as Tgas and Tamb.

k [W/m/K] cp [J/kg/K] ρ [kg/m3] L [kJ/kg] Tmelt [°C] solid liquid solid liquid

Al-Cu-Si 80 42 1300 1200 2730 422 571

Al-Cu-Mg-Zn 75 39 1510 1130 3140 305 520

Al-Mg-Zn 50 26 1630 1460 2380 310 443

Table 1. Thermal properties for Al-65wt%-Cu-30wt%Si-5wt% (Al-Cu-Si), Al-54wt%Cu-22wt%Mg- 18wt%-Zn-6wt% (Al-Cu-Mg-Zn) and Al-59wt%-Mg-35wt%Zn-6wt% (Al-Mg-Zn) [5].



Fig. 2 (a) Temperature as a function of time for exhaust gas, PCM catalytic converter and reference catalytic converter for an exemplary run with an 80 km/h step and Al-Cu-Si with 5 cm thickness. At t = 40 min the engine is stopped. Indicated is the delayed cool-down time (double arrow) of around 60 min. (b) PCM layer thickness as a function of delayed cool-down time for Al-Cu-Si, Al-Cu-Mg-Zn and Al-Mg-Zn for an 80 km/h step.

[1] Santos, H., and Costa, M., “Evaluation of the Conversion Efficiency of Ceramic and Metallic Three Way Catalytic Converters,” Energy Convers. Manag., 49(2), pp. 291–300, 2008.

[2] Farrauto Robert J., H. R. M., “Catalytic Converters: State of the Art and Perspectives,” Catal. Today, 51(3–4), pp. 351–360, 1999.

[3] Balenovic, M., and Hoebink, J., “Modeling of an Automotive Exhaust Gas Converter at Low Temperatures Aiming at Control Application,” SAE Pap. No. 1999 …, (October) , 1999.

[4] Voller, V., and Cross, M., “Accurate Solutions of Moving Boundary Problems Using the Enthalpy Method,” Int. J. Heat Mass Transf., 24(3), pp. 545–556, 1981.

[5] Kenisarin, M. M., “High-Temperature Phase Change Materials for Thermal Energy Storage,” Renew. Sustain. Energy Rev., 14(3), pp. 955–970, 2010.



Designing, 3D Printing And Testing of SiSic Porous Structures

E. Rezaei*1,2, S. Gianella3, S. Haussener2, A. Ortona1

*[email protected]

1MEMTI-SUPSI, 6928 Manno, Switzerland 2Institute of Mechanical Engineering, EPFL, 1015 Lausanne, Switzerland

3EngiCer SA, Viale Pereda 22, Balerna 6828, Switzerland

Open-cell cellular ceramics are attractive structures for high temperature applications such as heat exchangers, recuperators, radiant burners and heat storage systems. They offer low pressure-drop due to their high porosities (typically about 75-95%) and exhibit very high heat transfer due to their large surface area per unit volume. Nowadays porous structures can be designed and finely manufactured via direct or indirect rapid prototyping. Recently, near-net-shape Si-infiltrated SiC (Si- SiC) lattices have been fabricated via the replica technique followed by reactive melt infiltration of silicon.

Here, porous Si-SiC structures with various morphologies are designed and manufactured and their heat transfer behavior analyzed. In the experiments, cold air enters the porous solids, which are heated up by a tubular furnace. The volumetric heat transfer coefficient (VHTC) of each lattice is predicted for different mass flow rates by an inverse numerical method, utilizing the experimental data as well as a computational model. We developed a local thermal non-equilibrium continuum model, which considers two separate energy equations for the solid and fluid phases of the porous medium. The two energy equations are coupled by a volumetric heat transfer source/sink term.

The coupled experimental-numerical results show that VHTC increases with the velocity; a trend that is in accordance with the studies found in the literature. However, the Weaire-Phelan and Tetrakaidecahedron lattice had higher VHTCs. We hypothesize that this is due to the clogged pores of these lattices, which were formed during imperfect manufacturing.

Figure 1: SiSiC lattices of different cell types and the random foam.




Sorption-based long term thermal energy storage using sodium hydroxide

L. Baldini*, B. Fumey, R. Weber

*[email protected]

Empa Swiss Federal Laboratories for Materials Science and Technology, Laboratory of Urban Energy Systems, Building Systems and Technologies Group

A novel spiral finned tube heat and mass exchanger (HMX) (Fig. 1a) has been designed and tested in a lab setup at Empa to overcome the problems encountered with the former HMX studied in the European COMTES project [1-2]. The new design features a slow flow of liquid sorbent along the spiral fins admitting ample time for absorbing sufficient absorbate. Aqueous sodium hydroxide is used as sorbent and water as sorbate. Owing to the continuous film flow attained in this setup good surface wetting is achieved resulting in effective absorption. For storage application it is of primary importance that a high concentration spread, i.e. a high level of water vapor absorption is reached in a single pass without recirculation. In this way, high storage capacity and maximum temperature increase are reached. Experimental testing of the absorption process, confirmed its well-functioning by reaching a concentration reduction from an input of 50 wt% to an output of 27 wt% at a temperature increase of 35 K and a thermal discharge power of up to 400 W. Results of the various absorption and desorption tests with their positioning relative to the equilibrium curve are shown in Fig. 1b and are further explained in ref [3].

Fig.1 a) Spiral finned tube heat exchanger as part of the novel HMX design (left). b) Results from various absorption and desorption tests for different parameter settings diplayed in the concentration-temperature plane and compared to equilibrium conditions represented by the dashed curve (right)

Continuing research aims at upscaling the lab scale HMX towards a thermal discharge power of approximately 5 kW and more. Existing HMX design is optimized involving identification of advantageous heat exchanger characteristics such as fin spacing, width and slope. Furthermore, the heat transfer from the sorbent to the heat transfer fluid needs to be studied, focusing on suitable inner tube diameters and turbulators to maximize heat transfer and minimize temperature differences across the heat exchanger. This is of great importance for system performance, directly affecting maximum output temperature, mass transfer rate, and minimum concentration reached during absorption. Upscaling to greater power is then reached by installation of multiple heat exchanger tubes in parallel.

Further optimization addresses mass transfer enhancement in order to increase power density. From literature [4] it is understood, that at first contact with water vapor, equilibrium condition at the interface to sodium hydroxide is reached almost instantaneously such that a passivation layer is formed. Mass transfer is then governed by molecular diffusion driven by the concentration gradient across the liquid




film. Common approach to mass transport enhancement is surface to bulk mixing, evoking surface renewal hence increasing mass transfer rate [5]. Preliminary tests with modified fins, to reach a cascading flow with droplet impingement, showed up to double the transfer rate. Thus, modifications of heat exchanger tubes in this direction shall be more thoroughly investigated. In addition, surface inactivation as well as absorption and diffusion kinetics will be studied in more detail by analyzing the liquid sorbent film using Raman spectroscopy (Fig.2a). This will allow to understand the actual mass transfer mechanisms at work and to study mass transfer for different non-equilibrium conditions encountered within the HMX. Kinetics of absorption, especially for different mixing conditions will further be studied in a bulk lab scale reactor currently under design at Empa (Fig 2b). This reactor will offer the possibility to study a broad range of liquid sorbents, extending the scope beyond sodium hydroxide.

Fig.2 a) Exemplary lab setup to study absorption kinetics using Raman spectroscopy (left). b) Bulk lab scale reactor for studying different sorbents and effect of mixing on a bulk scale (right).

References:

[1] Köll, R.; van Helden, W.; Fumey, B. European Union Seventh Framework Program Project COMTES - Combined development of compact thermal energy storage technologies - Deliverable 5.1: Description of experimental systems; 2015. [2] Daguenet-Frick, X.; Gantenbein, P.; Müller, J.; Fumey, B.; Weber, R., Seasonal thermochemical energy storage: Comparison of the experimental results with the modelling of the falling film tube bundle heat and mass exchanger unit. Renew. Energy 2017, 110 (Supplement C), 162-173. [3] Fumey, B.; Weber, R.; Baldini, L., Liquid sorption heat storage – A proof of concept based on lab measurements with a novel spiral fined heat and mass exchanger design. Applied Energy 2017, 200, 215-225. [4] Tsai, B.-B.; Perez-Blanco, H., Limits of mass transfer enhancement in lithium bromide-water absorbers by active techniques. Int. J. Heat Mass Transf. 1998, 41 (15), 2409-2416. [5] Bigham, S.; Yu, D.; Chugh, D.; Moghaddam, S., Moving beyond the limits of mass transport in liquid absorbent microfilms through the implementation of surface-induced vortices. Energy 2014, 65, 621-630.



Seasonal Thermal Energy Storage with Aqueous Sodium Hydroxide – Reaction

Zone Development

X. Daguenet-Frick*, L. Omlin, M. Dudita, P. Gantenbein

*[email protected]

SPF Institute for Solar Technology, HSR University of Applied Sciences Rapperswil, Switzerland,

The focus of our work is to design, develop and test a 1 kW closed-sorption thermal energy storage (TES). Using a falling film heat and mass exchanger (HME), a system with improved efficiency and an experimental stand for testing the sensors were designed (Fig. 1 - Fig. 3). This concept was chosen because of the large contact area between sorbate and the liquid sorbent. Moreover, it allows a compact and modular design, reducing the volume of the reaction zone. The charging (desorption) and discharging (absorption) processes occur under reduced pressure. Numerical models of the desorption and absorption reaction zone were developed. Different sorbent pairs with high energy density (NaOH-H2 O, LiBr-H2 O and LiCl-H2 O) were investigated. [1] However, the sorption process is strongly influenced by the liquid sorbent wetting over the HME surface and its residence time. In the case of the absorption process, the concentrated sorbent solutions have high surface tension, thus poor wetting. This has a strong influence on the heat and mass transfer at the tube bundle surface. Several experimental methods to improve the surface wetting (surface texturing, different sorbents with/out surfactant addition) were investigated.[2]. The liquid sorbent residence time in the water vapor was increased by the use of porous SiC foams.[3] The foam is manufactured as a tube, inside which the stainless steel tubes (SS 316L) from the tube bundle are inserted (Fig. 3). Different porosities of the SiC foam were selected for testing, with porosity ranging from 10 to 30 PPI, where PPI (Pores per Inch) represents the number of pores in one linear inch (length). The preliminary experiments have indicated that all the tested ceramic foams have a hydrophilic behavior, both with concentrated NaOH (45 wt.%) and with LiBr (54 wt.%) solutions. Higher residence time are obtained for the sample with smaller pore size (30 PPI). Larger pores favor a faster flow of the concentrated sodium hydroxide solution, thus a lower residence time follows. The SiC foam will be further tested by integrating it in the desorber/absorber unit from the 1 kW prototype. A modular design was chosen for the easy replacement of the tube bundle flange in case of the absorber/desorber unit. This configuration allows testing several types of tubes and liquid sorbent modifications. Preliminary test of the main sensors (Fig. 2) used for accurately assessing the sorbent’s mass flow and concentration were performed using concentrated sodium hydroxide solution (50 wt.%).

Fig. 1 Isometric view of the top of the facility with the heat and mass exchanger unit as well as the storage tanks.

Fig. 2 Experimental stand for accurately assessing the sorbent’s mass flow and concentration of sodium hydroxide solution.




Fig. 3 Sectional view (left) of the absorber/desorber heat and mass exchanger (tube bundle and flange in blue, manifold in yellow) and (right) hydrophilic SiC ceramic foam with pores partially filled by concentrated aqueous sodium hydroxide; the porosity is 30 PPI, where PPI represents the number of pores per inch.

References: [1] Daguenet-Frick, X., Gantenbein, P., Frank, E., Fumey, B., Weber, R., 2015. Development of a numerical model for the reaction zone design of an aqueous sodium hydroxide seasonal thermal energy storage. Sol. Energy, ISES Solar World Congress 2013 (SWC2013) Special Issue 121, 17–30. doi:10.1016/j.solener.2015.06.009 [2] Dudita, M., Daguenet-Frick, X., Gantenbein, P., Seasonal Thermal Energy Storage with Aqueous Sodium Hydroxide – Experimental Methods for Increasing the Heat and Mass Transfer by Improving Surface Wetting, in: 11th ISES EuroSun Conference - International Conference on Solar Energy for Buildings and Industry. Palma (Mallorca) 2016..

[3] Dudita, M., Daguenet-Frick, X., Gantenbein, P., 2018. Closed Sorption Seasonal Thermal Energy Storage with Aqueous Sodium Hydroxide, in: Visa, I., Duta, A. (Eds.), Nearly Zero Energy Communities: Proceedings of the Conference for Sustainable Energy (CSE) 2017. Springer International Publishing, Cham, pp. 239–246. doi:10.1007/978-3-319-63215-5_18




Battery and Battery Materials


Investigation on the Promising P2-Na0.67Mn0.6Fe0.25Al0.15O2 Cathode Material

E. Marelli*, C. Marino, C. Villevieille

*[email protected]

Paul Scherrer Institute, Electrochemistry Laboratory, CH-5232 Villigen PSI.

The worldwide increased demand of energy and the need to limit the fossil fuel consumption urged scientists to develop cleaner and more efficient storage system. Lithium-ion batteries (LiBs) are, since their first commercialisation in the early ‘90s, the technology of choice to power portable devices, thanks to the largest energy density stored. The limited availability of lithium and thus its expected increase in costs, however, favoured the development of the analogous sodium-ion batteries (NiBs). The larger atomic radius and ionisation potential of Na compared to Li, inevitably lead to a lower energy density in this family of batteries, which has to demonstrate long-term cycling stability and lower costs than the Li equivalent to hope for commercialisation.

Based on the remarkable performance reported for the P2-Na0.67 Mn0.5 Fe0.25 Co0.25 O2 (NaMFC) phase [1], the cobalt-free P2-Na0.67 Mn0.5 Fe0.25 Al0.25 O2 (NaMFA) was studied. Despite cobalt is believed to stabilise the layer structures upon cycling, NaMFA proved to have not only an higher specific charge, but also a better long cycling stability than its cobalt analogous. As it can be seen in the operando XRD analysis (Figure 1), the P2 phase is replaced by another structure, O2 phase, during the charge process. Several analytical techniques (including but not limited to XRD, SEM, XAS, electrochemical tests) were used to characterise the pristine and phase transitions occurring during cycling, in order to elucidate the reaction mechanism and the role of Co/Al.

Fig. 1: Operando XRD measurement of two selected diffraction peaks during the NaMFA charge and discharge in half-cell configuration with the corresponding galvanostatic curve (on the left).

References: [1] Liu, L.; Li, X.; Bo, S-H.; Wang, Y.; Chen, H.; Twu, N.; Wu, D.; Ceder, G. Adv. Energy Mater. 2015, 5(22), 1500944.




How Reliable is the Na Metal as a Reference Electrode?

J. Conder1,2, C. Marino1, C. Villevieille*1

*[email protected]

1Paul Scherrer Institut, Electrochemistry Laboratory, Switzerland

2Institut de Science des Matériaux de Mulhouse, Carbon and Hybrid Material Group, France

There is no doubt that Li-ion batteries are nearing their limitations in terms of energy density, lifetime and safety, and the progress is slower than expected. Thus, other alkali metals, especially Na, are currently being extensively investigated as alternatives to Li metal. So far, electrochemical systems based on Na-ion have been mostly considered to be purely academic. This system has been considered to be purely academic, and no real applications have been developed to investigate its viability, the only exception being the high temperature Na-S system, which was commercialized in the 1960s. Recently, however, the amount of research and the number of papers devoted to the development of active materials for Na-ion batteries is exponentially increasing, reflecting the interest of the battery community to re-consider the commercialization of Na-ion batteries in the near future. To date, most of the studies of novel materials for Na-ion batteries are performed using Na metal as both counter and reference electrode. Knowing the increased reactivity and sensitivity of the Na compared to Li metal, the question has been raised whether Na metal is a reliable reference electrode. In an attempt to answer it, by means of electrochemical impedance spectroscopy, EIS, we were studying the interfacial reactions taking place at the surface of the Na metal. We employed symmetric Na/Na cells and at first focused on the impact of the presence of a native oxide layer on the surface of Na.[1] As can be seen in Figure 1, scratching of the surface of the Na metal is crucial for improving the electrode/electrolyte interphases and, thus, ensuring reproducible results. In addition, other parameters, such as the thickness of the Na metal foil, the presence of air and water in the electrolyte, and electrolyte additive have a strong impact on the impedance response of the symmetric Na/Na cell. Although the results are still being analyzed, the knowledge acquired from these experiments has already resulted in modified cycling protocol and an example of the Na-ion cell with the optimized Na metal counter electrode will be presented.

Fig.1. Representative EIS spectra of symmetric Na/Na cells assembled with (left) the non-scratched and (right) the scratched Na metal electrodes.

References: [1] Conder J., Marino C., Villevieille C., Electrochemistry Communications, 2017, Submitted




4

+

Electrode Nanomaterials for Li-ion Batteries

N. H. Kwon*, J.-P. Brog, S. Maharajan, K. M. Fromm

*[email protected]

Department of Chemistry, University of Fribourg, Chemin du Musée 9, CH-1700 Fribourg, Switzerland

Nanomaterials are known to interact well with lithium ions due to their high surface area and short diffusion path length of Li+ as compared to micron-scale materials. We studied nanoscale LiMnPO4and LiCoO2 as cathode materials and carbon-encapsulated Sn as anode nanomaterial for the application of Li-ion batteries [1, 2].

LiMnPO4 has an excellent structural stability versus Li + insertion/extraction due to PO4-3 polyanions and has a high redox potential of 4.1 V vs. Li+/Li, providing a higher energy density (701 Wh/kg) compared to that of commercial LiFePO (578 Wh/kg) [3]. The kinetic reaction of LiMnPO4 with Li+can be enhanced by controlling the shape and size of LiMnPO4 nanoparticles. Our study revealed that shortening only the length of the Li+ diffusion direction in the LiMnPO4particles (rather than reducing all dimensions of LiMnPO4 particles) is the critical parameter to increase the rate capability and gravimetric capacity (mAh/g) (Fig. 1 left). On the other hand, the packing densities of nanomaterials are lower compared to that of micron-sized materials. This issue can be solved by the formation of a dense and homogeneous composite structure. Ball-milled LiMnPO4 /C composites exhibited 273 and 180 mAh/cm3, while non-ball milled LiMnPO4 mAh/cm3 at C/20 and 1C, respectively (Fig. 1 right) [4].

with carbon exhibited only 75 and 50

Fig. 1. The rate capability of nano-rod shaped LiMnPO4 electrode (left). The comparison of volumetric capacities of ball milled and non-ball milled LiMnPO4 /C at different C-rates (right).

In case of LiCoO2 , we synthesized a bi-metallic single-source precursor, reducing a calcination temperature and duration in half of the one of conventional processes of solid state reactions. This yielded LiCoO2 as nanoparticles with an electrochemically reversible structure. Using nano-LiCoO2 in the cathode composite instead of micron-scale material, we could improve the relative amount of accessible/useable Li+ to more than 70 % of the theoretical capacity. For comparison, commercial micron-sized LiCoO2 exhibits about 50 % of Li available (Fig. 2. Left). Furthermore, we found the Li+

diffusion coefficient of nano-LiCoO2 to be > 10-100 times higher than that of micron-LiCoO2 due to the shortened diffusion path length in the lattice structure of nano-LiCoO2 (Fig. 2 right) [5].




Fig. 2. The rate capability of nano-LiCoO2 prepared by various single bi-metallic precursors (left). The comparison of Li+ diffusion coefficients in commercial and nano LiCoO2 materials (right).

Sn can provide about 3 times higher specific capacity (994 mAh/g) compared to carbon-based anode material (372 mAh/g) by forming Sn-Li alloy. However, Sn based anodes undergo up to 360 % of volume expansion upon lithium ion insertion, leading to cracks and hampering reversible electrochemical processes. One solution to improve the reversibility and the coulombic efficiency is the formation of a nanostructured composite. When Sn is encapsulated by a carbon shell, pulverization and irreversible reactions with Li+ might be prevented. The synthesis of Sn@C nano- rattles is however challenging due to a low melting point of Sn (232 oC). Nano-rattle structured Sn@C showed reversible electrochemical reactions (Fig. 3) and specific capacities of 600, 300 and 150 mAh/g at C/10, C/5 and 1C, respectively.

Fig. 3. The rate capability of nanorattle structured Sn@C anode (left). The cyclic voltammograms of Sn@C anode (right).

References: [1] N.H. Kwon, J.P. Brog, S. Maharajan, A. Crochet, K.M. Fromm, Chimia, 2015, 69, 734-736. [2] S.-L. Abram, J.-P. Brog, P.S. Brunetto, A. Crochet, J. Gagnon, N.H. Kwon, S. Maharajan, M. Priebe, K.M. Fromm, Chimia(Aarau), 2016, 70, 661.

[3] A.K. Padhi, K.S. Nanjundaswamy, J.B. Goodenough, J. Electrochem. Soc., 1997, 144, 1188-1194.

[4] N.H. Kwon, H. Yin, T. Vavrova, J.H.W. Lim, U. Steiner, B. Grobéty, K.M. Fromm, J. Power Sources, 2017, 342, 231-240. [5] J.P. Brog, A. Crochet, J. Seydoux, M.J.D. Clift, B. Baichette, S. Maharajan, H. Barosova, P. Brodard, M. Spodaryk, A. Zuttel, B. Rothen-Rutishauser, N.H. Kwon, K.M. Fromm, J Nanobiotechnology, 2017, 15, 58-80.



Investigations for a Full Cell Li(Ni1/3Mn1/3Co1/3)O2 (NMC) Benchmark

J. Vidal Laveda*, E. Stilp, S. Dilger, and C. Battaglia

*[email protected] – Swiss Federal Laboratories of Materials Science and Technology,

Laboratory Materials for Energy Conversion, Switzerland

Our aim within the SCCER Storage is the development of a high energy density cathode material for Li-ion batteries and to combine it into a full cell with a nano-Sb based anode delivering an energy density of 275 Wh/kg on cell level. During the first 9 months of the project, we built and validated an automated co-precipitation setup for the shape-controlled synthesis of NMC-type cathode powders. The use of alternative synthesis routes employing microwave radiation to fasten reaction times is also being investigated.

To improve energy density on cell level, we developed a NMC slurry preparation and coating process that enables us to reach high mass loadings (up to 29 mg/cm2) and high active material contents (96%) in the electrodes showing excellent rate capability (3.8 mAh/cm2 at 1C) when compared to industrial reference electrodes (Figure 1a). Full cells NMC111/graphite were tested at slightly lower mass loadings and optimized using vinylene carbonate (VC) as an additive in the electrolyte (Figure 1b). Ultimately, we also performed preliminary electrochemical tests of our electrode materials in pouch cell configuration with 2 cm x 2 cm active area.

Figure 1. (a) Rate performance of NMC111 vs. Li compared to the NMC111 and NMC811 industrial references. (b) Rate performance of a NMC111 vs. graphite full cell optimized using VC as electrolyte additive.




Pilot Production Line for Battery Cell Manufacturing

A. Fuerst*, A. Haktanir , M. Stalder

*[email protected]

BFH-ESReC, Research group: Manufacturing technologies for battery production, BFH-TI, Switzerland

The manufacturing technologies for battery production team at Bern University of Applied Sciences leading research activities on battery manufacturing and support battery production industry, its equipment manufacturers and material suppliers in Switzerland. The team combines machinery and process knowledge with a holistic approach undertaking cooperation between industry and research studies for a mutual know-how transfer.

Presently, the team is implementing a pilot production line for battery manufacturing. For this aim and with the consent of industrial partners, the pouch cell design was chosen as a common application of Li-ion batteries. For pouch cell type a multi-layer composite with aluminum is used as the housing material [1]. Mentioned battery manufacturing typically includes cutting, stacking and assembling production stages. These are three important steps which have major potential for improvement concerning the process parameters such as positioning and cutting accuracy, cutting speed etc., including quality control for self-adjusted process control [2].

The following figure shows the status of the pilot production line. The orange colored part shows the major steps for electrode production which will be studied in the future. The current activities focus on battery cell manufacturing and especially cutting and stacking steps, marked in blue.

Figure 1: Lithium-ion battery production steps and pilot production line (current state)




Firstly, a nanosecond pulsed fiber laser unit is implemented for cutting the anode and cathode sheets. Optimization studies for the operational parameters to achieve the required quality of the electrode cuts are ongoing. First of all, this requires some more work for copper foils, since the laser light is highly reflected by plain and mainly by melted copper.

After the electrode cutting, anode and cathode sheets are assembled with a separator. Z-folding is one of the assembling methods in which the separator foil is continuously folded, surrounding anode and cathode sheets. As a second step for the pilot line the Z-folding module has been installed. This unit is rather flexible to assemble different sizes of electrodes ranging from DIN A4 sheet size to DIN A8 (credit card size).

Another important issue about the above-mentioned applications is the handling of electrode sheets between these two modules. For this aim, a handling system with two robotic arms will connect the cutting and the Z-folding units, hence anode and cathode sheets can be fed without human contact. Realization of the handling system will be completed by the end of 2017.

To optimize the handling unit with robots, additional simulations were done. This simulation represents a virtual copy of the operational process. The outcome of these simulations will be published later.

Figure 2: Virtual production steps of the pilot production line (current state)

As a conclusion, it can be said that this pilot line helps to get in-depth understanding and serves as a showcase for industrial partners and research groups. With the aid of modelling a virtual production line and the integration of smart sensors to the system, an „Industry 4.0" environment for the future applications and their developments will be ensured.

[1] Korthauer, R., Handbuch für Lithium-Ionen-Batterien. Springer Vieweg: 2013; 228. [2] Fuerst, A.; Haktanir, A., Pilot Production Line for Battery Cell Manufacturing. In Book of Abstracts Heat & Electricity Storage 5th Symposium, 9 May 2017.



Electrode Foils Cutting Studies with Fiber Laser Unit

A. Fuerst*, A. Glarner , M. Müller , P. Weber

*[email protected]

BFH-ESReC, Research group: Manufacturing technologies for battery production, BFH-TI, Switzerland

Cutting or shaping of electrodes is generally done by the mechanical method die cutting or by laser beam [1]. In terms of high improvement potential of process and quality parameters, it is one of the most important steps in Li-Ion battery manufacturing. Both methods have certain advantages and disadvantages. Because of a high production flexibility regarding the cutting shape and speed [2], the research group has focused on the laser unit. In the running process, it also allows to change the electrode geometry on the fly. However, the complexity of laser cutting requires in-depth knowledge of the related parameters in terms of process and quality requirements for various types of current collectors and cell geometries. For that purpose, the group has developed a test construction for the laser parameter optimization which takes place in the pilot line project for battery manufacturing. Properties and current activities of the fiber laser unit are summarized in the following sections.

Fiber Laser unit properties at BFH

• SPI – Pulsed Fiber Laser• Wavelength: 1064nm • Pulse waveforms: 18 • Pulse repetition frequency rate: 460 kHz • Max pulse energy: 0.22mJ • Pulse duration range: 30 ns

Figure 1: Laser with scanning unit – electrode cutting test construction (current state)




The scope purpose of the test construction is the optimization of laser parameters such as cutting speed, laser power, focus position in Z-direction, number of repeated cuts etc. The material cuts are evaluated regarding to pre-defined quality related properties [3].

In this test design, the laser cut is carried out under nitrogen atmosphere which prevents metal oxidation. Residues are taken out of the system simultaneously with vacuum outlets, cf. Figure 1. Furthermore, the process occurs in a closed box to shield it from the laser beam. In order to observe the process on-line, a camera system is installed, cf. Figure 1.

Summary of studies

The development of the test construction was supported with CFD (Computational Fluid Dynamics) simulation, cf. Figure 2. The goal was to ensure a laminar flow between inlets and outlets to obtain optimal shielding conditions. Thus, the waste particles can be removed from the system against the laser direction, which ensures a high cutting-quality.

Figure 2: CFD simulation results

Presently, a test construction has been assembled and first tests for aluminum and steel samples without coating are carried out. Research studies for the demanding quality of the electrode cut for various types of materials are ongoing. The optimization studies will ensure the acquaintance of the electrode cutting with a fiber laser unit. In this manner, the acquired knowledge enables a flexible electrode production at the battery manufacturing pilot line at BFH.

References

[1] Korthauer, R., Handbuch für Lithium-Ionen-Batterien. Springer Vieweg: 2013. [2] Michaelis, S.; Maiser, E.; Kampker, A.; Heimes, H.; Christoph, L.; Wessel, S.; Thielmann, A.; Sauer, A.; Hettesheimer, T. Roadmap Batterie-Produktionsmittel 2030 - Update 2016; VDMA: 2016. [3] Techel, A. Produktionstechnisches Demonstrationszentrum für Lithium-Ionen-Zellen; Fraunhofer: 2011



MoS2 Lamellar Membrane for Selective Molecular Transport, HER and its

Application in Li Water Battery

M. Deng, M. Li, H. G. Park*

*[email protected]

Nanoscience for Energy Technology and Sustainability, Department of Mechanical and Process Engineering, Eidgenössische Technische Hochschule (ETH) Zürich, Switzerland

Molybdenum disulfide (MoS2 ) can construct a lamellar membrane via Van der Waals interaction which offers the easy to form a freestanding and flexible membrane without the need of adding additional additives. Such a lamellar structure stacked by 2 dimensional (2D) MoS2 platelets offers unique and massive 2D channels with an interspace of ~6.3 Å confirmed by XRD characterization. These channels can maintain the interspace without significant change in a harsh aqueous environment of pH from 0.6 to 13.2, resulting in a highly stable lamellar membrane. Like graphene oxide, this lamellar membrane shares in common that it is permeable to water vapour, yet impermeable to gas. For the first time, this membrane reveals a molecular sieving behaviour to organic vapours and selective diffusion to aqueous ions.[1]Furthermore, through surface engineering technology, MoS2 platelets membrane with improved morphology texture exhibits a promising catalytic activity to HER in a basic (pH: ~12-13) aqueous solution, hinting the possible application involved in basic environment. As a result, an investigation in Li water battery has been carried out. Due to the high stability and excellent activity of MoS2 , the battery cell for the first time equipped with MoS2 platelets could offer a reliable voltage >2.2 V for more than 2.5 days.

Fig.1 A freestanding lamellar MoS2 membrane (left) and its stacked structure with the simulated water molecules inside (right)

Reference: [1] Deng, M.; Kwac, K.; Li, M.; Jung, Y.; Park, H. G., Nano Letters 2017, 17, 2342-2348.




Rechargeable Li-Air and Li-Water Batteries

N. H. Kwon*, H. Yao, K. M. Fromm

*[email protected]

Department of Chemistry, University of Fribourg, Chemin du Musée 9, CH-1700 Fribourg, Switzerland

Rechargeable lithium-air batteries potentially provide higher energy densities than the conventional rechargeable batteries due to the redox combination of a light lithium metal anode and an oxygen cathode [1, 2]. However, the reversible redox reactions and cyclability of those batteries remain a challenge. Among the possible set-ups of Li-air batteries is the use of an aqueous electrolyte, which provides a higher efficiency and cyclability due to the high ionic mobility and good solubility of the discharge products [3]. However, water must not contact the lithium metal anode to avoid a violent reaction, producing heat and gas evolution. Thus, we propose an organic electrolyte on the lithium anode to protect the metal and an aqueous electrolyte on the cathode side to allow reversible electrochemical reactions. During discharging, the pH-value increases due to the formation of LiOH, which damages the membranes [4] and leads upon saturation to precipitation [5]. Therefore, buffering the pH in an aqueous electrolyte is a key parameter to improve the reversibility of the redox reactions.

Commercial carbonate based organic electrolytes are not suitable to be used in the Li metal anode compartment because these are not chemically stable under O2 environment [6]. It is also reported that imidazolium-based ionic liquids as electrolyte react with lithium metal [7]. Therefore, we studied new electrolytes based on crown ether ionic liquids in order to be stable chemically, thermally and electrochemically. The synthesized crown-ether based ionic liquids showed an excellent thermal stability until ca. 400 oC (Fig. 1 left). The cycleability of 10 % of ionic liquid in EC:EMC:DMC with 1M LiPF6 was tested with Li metal as both anode and cathode in a coin cell in a constant current mode. It showed good electrochemical stability: 78 % of retention from the initial value at the 200th cycle (Fig. 1 right). In addition, the cation transference number of ionic liquid containing organic electrolyte is larger than 0.5 while that of commercial electrolyte without ionic liquid is 0.3 – 0.4. We also observed that these ionic liquids are chemically stable with lithium metal, which is different from other unstable imidazolium-based ionic liquids which react with lithium metal.

Fig. 1. The thermogravimetric analysis of synthesized crown-ether based ionic liquids (left). The cyclability of the synthesized ionic liquid upon 200 cycles versus Li+/Li (right).

Since the electrochemical reaction occurs at the air electrode compartment where O2 is entered, we studied a half cell of air electrode compartment using an aqueous electrolyte as well. The solubility of O2 in an aqueous solution increased when the concentration of LiOH decreased. We added phosphate buffers to adjust the pH to 7 in a half cell Li-air system and to maximize the solubility of O2 . After optimization of air electrode compartment with an aqueous electrolyte, a dual-electrolyte rechargeable Li-air battery was developed with an organic electrolyte compartment at the Li-metal anode and an aqueous electrolyte compartment at neutral pH for the air cathode. We observed oxygen reduction and oxidation reactions in CV at a cell potential of 3.6 V (Fig. 2 left). The full cell is reversible at the potential range between 3 and 4.5 V at 6.4 uA. When we enlarged the potential




window to 2-4.5 V, the cycleability degraded. The specific capacity of the full cell is yet about 30 – 40 mAh/g (Fig. 2 right).

Fig. 2. The cyclic voltammograms of a dual-electrolyte Li-air full cell (left). The cyclability of a dual- electrolyte Li-air full cell (right).

References: [1] J.P. Zheng, R.Y. Liang, M. Hendrickson, E.J. Plichta, J. Electrochem. Soc., 2008, 155, A432-A437. [2] F. Cheng, J. Chen, Chem Soc Rev, 2012, 41, 2172-2192. [3] X. Wang, Y. Hou, Y. Zhu, Y. Wu, R. Holze, Nature, 2013, 3, 1401.

[4] D.-J. Lee, O. Yamamoto, D.-m. Im, Y. Takeda, N. Imanishi, Lithium air battery, US20120028164A1 2012. [5] Y. Wang, H. Zhou, J. Power Sources, 2010, 195, 358-361. [6] F. MIZUNO, S. NAKANISHI, Y. KOTANI, S. YOKOISHI, H. IBA, Electrochem., 2010, 78, 403-405. [7] P. Schmitz, R. Jakelski, M. Pyschik, K. Jalkanen, S. Nowak, M. Winter, P. Bieker, ChemSusChem, 2017, 10, 876-883.



2

Nano Structured Nickel Electrodes for Ultra-High Power Aqueous Double Layer Capacitor Application

J.B. Asante*, B. Fuchs, O. Boese, L. Joerissen

*[email protected]

Center for Solar Energy and Hydrogen Research (ZSW), Helmholtzstr. 8, 89081 Ulm, Germany,

Alkaline secondary batteries (e.g. NiCd, NiZn and NiMH) has been deployed in industrial and consumer applications since several decades. NiMH as an example continues to dominate the present-day technology used in full hybrid electric vehicles. For high power applications, the current collectors tend to have enlarger surfaces to reduce internal impedance, as a result of which sinter, fiber or foam electrodes were designed with structures in the low µm range.[1] Here we present the preparation and utilisation of nano-structured nickel current collectors and derived nickel hydroxide positive electrodes, which helps to enlarge significantly their power capabilities.

Fig. 1: Electron micrograph of nano-structured Nickel current collector at different magnifications

The developed nano-structured Nickel current collector which is bendable, allows the production of positive nickel hydroxide Ni(OH)2 electrodes of varying thicknesses by electrochemical deposition.[2] Capacities of 1.5 mAh cm-2 are achievable for a 10 µm equivalent Ni(OH) coating thickness. Furthermore, the very fast positive Ni(OH)2 electrode was combined with an activated carbon electrode as negative electrode to obtain an asymmetrical double layer capacitor which was able to deliver at a 1150 C-rate 69.0% of initial capacity. The Peukert diagram shows a linear behaviour up to this current load.

10 NiMH high energy cell NiMH high power cell

1 ZSW high surface area cell

0,1

0,01

Linear Peukert

Range

1E-3 Non-linear

Range

1E-4

1E-5 8C 35C 1150C

1 10 100 1000 10000

C-Rate [h-1]

References:

Fig. 2: Peukert diagram of Ni(OH)2 based technologies

[1] A.K. Shukla, B. Hariprakash in J. Garche (Ed.) Encyclopedia of Electrochemical Power Sources (Elsevier), 404-411 (2009).

[2] M. Wohlfahrt-Mehrens et al. Solid State Ionics 86–88 (1996) 841-847

Dis

char

ge ti

me

[h]




4 6 3 4

Non-Aqueous Copper Battery for Heat-to-Power Conversion and Storage

S. Maye*, P. Peljo

*[email protected]

Laboratory of Physical and Analytical ElectrochemistryEcole Polytechnique Fédérale de Lausanne, 1951 Sion, Valais, Switzerland

For this poster, we will describe a new approach for conversion of heat into chemical energy, stored in a battery. A thermo-electrochemical system with a redox flow battery (RFB) is proposed to allow the conversion of heat at relatively low temperature into chemical energy. The electroactive species of the battery are copper ions in an organic solvent mixture containing acetonitrile (ACN) as a complexing agent. Water is avoided because its presence influences considerably the voltage that can be achieved by the cell. During the process of charging, the Cu(I) complex with acetonitrile can be destabilized by a heat source around 150°C (or more) and it leads to the disproportionation of Cu(I) in Cu and Cu(II). In this charged state, the chemical energy can be converted into electricity with the Cu oxidation and Cu(II) reduction in the different half cells. This battery can also store energy as a conventional RFB with a purely electrical charging [1]. For a better understanding, the electrochemistry of copper in acetonitrile and propylene carbonate (PC) mixtures has been investigated. The thermodynamic properties of the copper electrolytes, as well as the heat required for the thermal regeneration has been evaluated by differential scanning calorimetry (DSC).

a)

b) c)

Fig. 1: a) the concept of heat conversion into chemical energy stored in an all-copper battery. b) DSC curves of ACN, PC and [Cu(CH CN) ]BF at 5°C·min−1 c) IR corrected charge/discharge

3 4 4 cycles at 60°C with 10 mA·cm−2 regarding the potential of a cell with 0.15 M [Cu(CH CN) ]BF and

3 4 4 0 15 M TEABF4

The theoretical battery efficiency should reach 30%, if a thermal charging is applied. For the battery performance with an electrical charging, the Coulombic efficiency is around 95% and the energy efficiency stays between 45 and 60% with charging current in a range going from 1 to 15 mA·cm−2. Dif- ferent counter anions (BF −, PF − …) for the [Cu(CH CN) ]− complex have been tested to increase the solubility and performance of the CuRFB. References:

[1] P. Peljo, D. Lloyd, N. Doan, M. Majaneva, et K. Kontturi, Towards a thermally regenerative all- copper redox flow battery, Phys. Chem. Chem. Phys., vol. 16, p. 2831‑2835, 2014. [2] Deno, N. C.; Richey, H. G.; Liu, J. S.; Lincoln, D. N.; Turner, J. O. J. Amer. Chem. Soc. 1965, 87, 4533-4538.





Hydrogen Generation Hydrogen Storage


Synthesis and Characterization of Core-Shell Structure of NaBH4

for Hydrogen Storage H. Yang*1,2, L. Lombardo1, A. Züttel1,2

*[email protected]

1 LMER, ISIC, SB, École polytechnique fédérale de Lausanne (EPFL) Valais/Wallis, Energypolis, Ruede l’Industrie 17, CP 440, CH-1951 Sion, Switzerland

2 Empa Materials Science and Technology, Dübendorf, Switzerland

Sodium borohydride (NaBH4 ) is a promising hydrogen storage material due to its high storage capacity. However, the hydrogen desorption temperature is high and the hydrogen adsorption / desorption cycle is not technically reversibly. Therefore, NaBH4 is synthesized as nanoparticles to reduce the melting point resulting in a lower hydrogen desorption temperature and improved hydrogen absorption/desorption reversibly. The surface of NaBH4 nanoparticles was coated with various metal catalysts (nickel, palladium, and cobalt) to form a core-cell structure [1]. These NaBH4 nanoparticles are capable of rapid hydrogen desorption at moderate temperatures due to the short diffusion length of hydrogen, instability in the structure between the metal catalyst and boron. The hydrogen sorption cycles are highly reversible [2, 3]. Various metal catalysts are compared in order to optimized the catalytic activity on NaBH4 and to design effective hydrogen storage materials. As-prepared materials were identified by XRD, TEM and Raman spectroscopy. The hydrogen adsorption/desorption capacity and the reversibility were analyzed by means of TGA and PCT.

Figure 1. The core-shell structure of NaBH4 with various metal catalysts.

References [1] Christian, M. L.; Aguey-Zinsou, K. F. ACS Nano. 2012, 6, 7739. [2] Simoes, M.; Baranton, S.; Coutanceau, C. Phys. Chem. C. 2009, 113, 13369. [3] Demirci, U. B.; Miele, P. Phys. Chem. Chem. Phys. 2010, 14651.




Efficient Electrodes Based on Stainless Steel for Water Oxidation

F. Le Formal*1,2, N. Guijarro2, X. Pereira Da Costa2, and K. Sivula1,2

*[email protected]

1SCCER Heat and Electricity Storage, c/o Paul Scherrer Institut, Switzerland 2LIMNO, Institute of Chemical Sciences and Engineering (ISIC), EPFL, Lausanne, Switzerland

Efficient storage of renewable sources of energy into chemical fuels is an attractive method to utilize these universal and abundant types of energy all year long, limiting the drawbacks of intermittency and distance between consumption and production locations. Hydrogen is extremely valuable in this sense, due to its high energy density, and its ability to be produced readily from electricity and water through electrolysis. However, electrolyzer costs need to be decreased in order for this technology to become available on the market.[1]

Water oxidation, half of the water electrolysis reaction, has long been considered as the major limitation due to the high overpotentials required to perform the reaction. NiFe alloys are assumed to be amongst the best catalyst, with overpotentials in the range of 0.3 – 0.35 V to establish 10 mA cm-2

of oxidative current. We have shown previously that this state-of-the-art catalyst can be be synthesized in-situ on naturally occurring minerals, such as the Gibeon Meteorite.[2]

Here, we report our recent studies concerning the utilization of mass-produced stainless steel sheets as OER electrodes. The best performance (0.25 – 0.3 V overpotential) are obtained after a few hours of OER operation due to the in-situ formation of an active layer. This active layer is characterized as an oxy-hydroxy porous film which has a different metal composition than the original stainless steel sheet due to slow dissolution of Cr and Fe atoms in alkaline solutions at potentials where OER is performed. Interestingly, different stainless steels with different composition resulted in catalytic layers with similar composition, suggesting a stable and high-performing composition for the electrode. Strategies developed to prepare electrodes from the inexpensive and abundant 3d transition metals are also discussed.

[1] Le Formal, F.; Bourée, W. S.; Prévot, M. S.; Sivula, K. Challenges towards Economic Fuel Generation from Renewable Electricity: The Need for Efficient Electro-Catalysis. Chim. Int. J. Chem. 2015, 69 (12), 789–798

[2]Le Formal, F.; Guijarro, N.; Bourée, W. S.; Gopakumar, A.; Prévot, M. S.; Daubry, A.; Lombardo, L.; Sornay, C.; Voit, J.; Magrez, A.; et al. A Gibeon Meteorite Yields a High-Performance Water Oxidation Electrocatalyst. Energy Environ. Sci. 2016.




Inkjet Printing of Electrocatalysts and Electrocatalyst Gradients in 2D and 3D for the ORR and OER

V. Costa Bassetto, A. Lesch*

*[email protected]

Laboratoire d'Electrochimie Physique et Analytique, École Polytechnique Fédérale de Lausanne, EPFL Valais Wallis, CH-1951 Sion, Switzerland

State-of-the-art inkjet printers equipped with various parallel printheads and integrated post- processing techniques enable the rapidly adjustable and high throughput fabrication of multi component systems, e.g. gradient material libraries, and multi-layered structures. Nanoparticulate dispersions and precursor inks can be printed with micrometer resolution (drop spread on the surface) at high speed using up to several hundred nozzles at once. Both concepts applied in this contribution for the preparation and investigation of catalyst layers (CLs) in electrochemical energy conversion devices.

For instance, inkjet printing can be used for the controlled deposition of a mixture of carbon black supported Pt or Ir nanoparticles and an ionomer onto ion exchange membranes, which are then denoted as catalyst coated membranes (CCMs). In such CLs the oxygen reduction reaction (ORR) and/or the oxygen evolution reaction (OER) take place as one half reaction in polymer electrolyte membrane fuel cells (PEMFCs) and electrolyzers. State-of-the-art electrocatalyst materials are often selective and durable for just one of the two reactions, either for the OER or ORR. However, there are currently just a few electrocatalyst materials and structures discussed, which seem to be promising to withstand the conditions for both reactions, at least for a certain amount of time. Due to the sluggish kinetics of the ORR an asymmetry between ORR and OER generally appears. This could potentially be overcome by mixing different catalysts in very defined ratios. In this work, Pt and Ir were the chosen as model catalysts to print bifunctional CLs active for both the ORR and OER. Knowing the stability issues of the used catalyst materials for long-term operations in reversible modes, these materials were, however, ideal to demonstrate the applicability of inkjet printing. In order to investigate the printed CLs, spectroscopic, microscopic and electrochemical (e.g. voltammetry, electrochemical impedance spectroscopy and scanning electrochemical microscopy with soft probes) methods were applied. In particular, we demonstrate the application of contact mode SECM with a soft platinum microelectrode enabling the convenient investigation of reactivity along the strongly curved and bent membranes in solution.

Furthermore, we present a totally new approach of combining inkjet printing and flash light irradiation of electrocatalyst precursors to coat large electrode surfaces within few minutes under ambient conditions with well-defined platinum nanoparticles. This facile process, which combines nanoparticle synthesis and electrode fabrication, can be used for preparing material libraries and could potentially be used for building up CLs in a layer-by-layer fashion with simultaneous printing and photonic curing.





Formic Acid : A Viable Option to Chemical Hydrogen Storage

M. Montandon-Clerc*, A. F. Dalebrook, G. Laurenczy

*[email protected]

Institute of Chemical Sciences and Engineering, Group of Catalysis for Energy and Environment; École Polytechnique Fédérale de Lausanne (EPFL), Switzerland

Today’s energy economy is completely dominated by fossil fuels, whether it is for transportation, residential, commercial or industrial use. This intensive use of oil, coal and natural gas is bringing problems such as global warming and resources depletion. It is obvious that the world will need renewable energy in a near future. Some efforts are already deployed but a main issue always appears, the storage problem. Energy is not easy to store, which makes fossil fuels so convenient. Hydrogen, for example, is a really promising energy vector but is problematic for many reasons. It is highly explosive, demands effort to compress and the reservoirs in which it is pressurized are bulky and not easy to handle.[1] In 2006, our group came up with the idea of using formic acid to produce hydrogen. Using a ruthenium based catalyst, we were able to dehydrogenate formic acid in aqueous condition. Releasing hydrogen on demand from formic acid makes the latter a practical medium to chemically store hydrogen.[2-3]

Fig 1 Using formic acid to store hydrogen and thus, energy.

Later, our group has shown the opposite reaction, CO2 reduction to formic acid. This method has also the advantage of being a way to valorize CO2 , which is usually a waste and also a greenhouse gas.[4] This is a second step in the idea of a “hydrogen battery”. Using an appropriate catalyst and changing the conditions, one should be able to store hydrogen via formic acid and later on, release it. Such a system would be CO2 neutral and could rely on renewable energy to produce hydrogen for its first step, such a solar and wind energy. In our more recent work, we were able to develop an iron based catalyst for the dehydrogenation of formic acid.[5] The use of non-noble metal is extremely interesting in the perspective of an industrial use of the aforementioned battery-like system. Using atmospheric pressure and mild temperatures, formic acid is dehydrogenated without traces of CO, a potential issue for PEM fuel cell membranes. Recently, we were able to produce formic acid, while going for high pressure and ambient temperatures, in acidic aqueous conditions and without any additives. (manuscript in preparation)

Acknowledgments: EPFL and SCCER are thanked for financial support.

References: [1] Léon, A. Hydrogen Technology in Mobile and Portable Applications; Springer-Verlag: Berlin, Heidelberg, 2008. [2] Fellay, C.; Dyson, P. J.; Laurenczy, G. Hydrogen production from formic acid. EP 1918247, 2006. [3] Fellay, C.; Dyson, P. J.; Laurenczy, G. Angew. Chemie - Int. Ed. 2008, 47, 3966–3968. [4] Moret, S.; Dyson, P. J.; Laurenczy, G. Nat. Commun. 2014, 5, 4017. [5] Montandon-Clerc, M.; Dalebrook, A. F.; Laurenczy, G. J. Catal. 2016, 343, 62–67.

H2 + CO2

Energy Energy Energy Energy Energy

HCOOH





Formic Acid on the Way to an Industrial-scale Energy Storage Vector

C. Fink*, G. Laurenczy

*[email protected]

Institute of Chemical Sciences and Engineering, LCOM, Group of Catalysis for Energy and Environment; École Polytechnique Fédérale de Lausanne (EPFL), Switzerland.

Renewable energies are replacing conventional energy sources more and more. A major drawback associated with them is that they are not available on demand but depending on short-term weather fluctuations and also on seasonal changes. The unsteady production per calendar month is well illustrated in Figure 1, which shows the total electricity production and consumption of Switzerland over the course of a year. Clearly can be seen an excess in summer and shortage in winter. The main factor for this behavior can be attributed to the blue bars which are representing renewable energy sources.

Fig. 1 Production (bars) and consumption (yellow line) of electricity of

Switzerland per year [1]

Fig. 2 The mixing of formic acid and DMSO is accompanied by heat release. The comparable high concentrations of FA (2.1 M)[2] reached during CO2hydrogenation in this system are associated with a more energy intensive hydrogen liberation.

An elegant solution would be to reversibly store the surplus energy from summer and consume it then upon demand during winter. Hydrogen obtained via electrolysis of acidified water is a simple and robust method to transform electrical into chemical energy. The challenging task of storing hydrogen can be solved by selective hydrogenation of carbon dioxide to formic acid.[2] The storage and recovery efficiency of hydrogen in the process is a 100% and formic acid storage is easily accomplished at ambient conditions and over long periods.[3,4]

In laboratory scale, the thermodynamics of these reactions can be neglected, since total energies are comparable small (Fig. 2). In total contrast stands the industrial, large-scale application of the same system. Hydrogenation and dehydrogenation energies contributing significantly to the total energy balance and therefore it is imperial to possess reliable thermodynamic data for planning such an energy storage system. In our laboratories, we perform reaction calorimetric studies to determine these values experimentally since literature offers only theoretical values.[5] These measurements combined with NMR spectroscopic examinations to elucidate the fundamental mechanistic mode of operation of the employed catalyst provide a solid basis for determining the desired thermodynamic data.[6] Acknowledgement: SCCER and EPFL are thanked for financial support References: [1] online source: http://sti.epfl.ch/page-78316-en.html, 28.09.2017 [2] S. Moret, P. J. Dyson, G. Laurenczy, Nat. Commun. 5 (2014). [3] D. Mellmann, P. Sponholz, H. Junge, et al., Chem. Soc. Rev. 45 (14), 3954-3988 (2016). [4] K. Sordakis, A. Tsurusaki, M. Iguchi, et al., Green Chemistry (2017). [5] C. Fink, S. Katsyuba, G. Laurenczy, PCCP 18 (16), 10764-10773 (2016). [6] C. Fink, G. Laurenczy, Dalton Transactions 46 (5), 1670-1676 (2017).




http://sti.epfl.ch/page-78316-en.html


Synthetic Fuels


Behavior of Sputter Deposited Thin Films of Cu and Cu Oxide towards CO2

Electroreduction A. A. Permyakova*1, A. Pătru1, J. Herranz1, T. J. Schmidt1,2

*[email protected]

1Electrochemistry Laboratory, Paul Scherrer Institut, Switzerland 2Laboratory of Physical Chemistry, ETH Zürich, CH-8093 Zürich, Switzerland

Presently electrochemical CO2 reduction technologies are challenged by high reaction overpotentials, poor faradaic efficiencies (FE) and low selectivity. The right choice of catalyst can significantly improve these factors, especially reaction selectivity [1-3]. Recent experimental studies on Cu electrocatalysts have shown that higher CO2 reduction selectivities and efficiencies towards certain valuable products could be achieved by modifying these metallic electrodes [4,5]. For example, Cu thin films prepared by electrochemically reduced thermally grown Cu oxide (Cu2 O) layers exhibit improved selectivity towards ethanol at significantly lower potentials (up to 50% FE at -0.35 V vs. RHE) in comparison to non-treated Cu catalysts (≈3% FE at -0.35 V vs. RHE).[5]

Herein, we will present detailed examination of Cu and Cu oxide thin film electrodes fabricated by reactive sputter deposition. A combination of SEM/EDX, XRD and XPS were used for physico- chemical characterization. Whereas, CO2 electro-reduction products were monitored using in line GC for gas products and capillary GC, IC, NMR for liquid products. Influence of Cu oxides and surface oxidation states on products efficiency and selectivity will be discussed.

References: [1] Herranz, J.; Durst, J.; Fabbri, E.; Patru, A.; Cheng, X.; Permyakova, A.A.; Schmidt, T.J. Nano Energy 2016, 29, 4.

[2] Durst, J.; Rudnev, A.; Dutta, A.; Fu, Y.; Herranz, J.; Kaliginedi, V.; Kuzume, A.; Permyakova, A. A. ; Paratcha, Y.; Broekmann, P.; Schmidt, T.J.; Chimia 2015, 12, 69. [3] Hori, Y. Electrochemical CO2 reduction on metal electrodes. Modern aspects of electrochemistry; Vayenas, C.; White, R.; Gamboa-Aldeco, M., Ed.; Springer, New York, 2008, Vol 42, pp 89–189. [4] Chen, Y.; Li, C. W. and Kanan, M. W. J. Am. Chem. Soc. 2012, 134, 19969 – 19972. [5] Li, C. W.; Ciston, J. and Kanan, M. W. Nature 2014, 508, 504 – 507.





CO2 Hydrogenation of Copper Nanoparticles Supported on Zirconium Modified Silica

E. Lam*, K. Larmier, P. Wolf, C. Copéret

*[email protected]

Laboratory for Interfacial Chemistry, ETH Zürich, 8093 Zürich, Switzerland

To date, there is no efficient way to employ and transform the ever-increasing amount of carbons dioxide (CO2 ) into more valuable resources. One approach to use CO2 could be its transformation into more valuable compounds such as methanol (MeOH).[1] Copper based catalysts have shown promising efficiency in terms of activity and selectivity for transforming CO2 to MeOH when supported on specific metal oxides. Of them zirconia (ZrO2 ) is known to promote MeOH synthesis. [2] Recently we proposed a reaction mechanism leading to MeOH occurring on the interface between copper and zirconia going via formate as an intermediate.[3]

Herein we use a surface organometallic chemistry (SOMC) combined with a thermolytic precursor (TMP) approach as well as incipient wetness impregnation (IWI) to maximize the ratio between Zr at the interface vs. the bulk on silica (SiO2 ). Cu nanoparticles on such supports show greatly enhanced activity and selectivity towards MeOH under CO2 hydrogenation conditions compared to Cu nanoparticles on SiO2 .

Solid state nuclear magnetic resonance spectroscopy and X-ray absorption spectroscopy was further used to investigate the catalyst and reaction intermediates

.

References: [1] Goeppert, A.; Czaun, M.; Jones, J.-P.; Prakash, G.K.S.; Olah, G. A., Chem. Soc. Rev., 2014, 43, 7995 [2] Fisher, I.A.; Bell, A.T.; J. Catal, 1997, 172, 222

[3] Larmier, K, Liao, W.-C.; Tada, S.; Lam, E; Vérel, R.; Bansode, A.; Urakawa, A.; Comas-Vives, A.; Copéret, C., Angew. Chem. Int. Ed., 2017, 56, 2318




Surface-Supported Cu-based Catalysts towards CO2

Conversion N. Kaeffer*, C. Mavrokefalos, H.-J. Liu, C. Copéret

*[email protected]

Laboratory of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog Weg 1-5, Zürich, Switzerland.

Our societies urgently need for alternative sources of energy.[1,2] Using sunlight to transforming CO2 , a species responsible for global warming, into a valuable fuel is an appealing strategy.[3,4] Such CO2- reduction reaction might be performed through the use of stoichiometric amounts of hydrogen[5] or by electroreduction.[4] In both cases, supported Cu nanoparticulate systems are efficient catalysts, although the reactivity and the selectivity of products are still not fully understood. Our group has a deep background in the preparation of well-defined nanoparticles onto oxides interfaces by the use of surface organometallic chemistry.[6,7] In this work, we investigate the preparation of Cu nanoparticles onto different substrates, including conductive carbonaceous surfaces. These systems will be assessed in regards of their catalytic properties, namely towards CO2 electrochemical reduction to gain understanding in terms of reactivity and selectivity of the reaction.

60

50

40

30

20

10

0 2 3 4 5 6 7 8

particle size (nm)

Fig.1 Transmission electron microscopy image of Cu nanoparticles deposited on carbon black by surface organometallic chemistry (left) and corresponding particle size distribution histogram (right).

References: [1] Cook, T. R.; Dogutan, D. K.; Reece, S. Y.; Surendranath, Y.; Teets, T. S.; Nocera, D. G. Chem. Rev. 2010, 11, 6474-6502.

[2] Faunce, T.; Styring, S.; Wasielewski, M. R.; Brudvig, G. W.; Rutherford, A. W.; Messinger, J.; Lee, A. F.; Hill, C. L.; deGroot, H.; Fontecave, M.; MacFarlane, D. R.; Hankamer, B.; Nocera, D. G.; Tiede, D. M.; Dau, H.; Hillier, W.; Wang, L.; Amal, R. Energy Environ. Sci. 2013, 4, 1074. [3] Olah, G. A. Angew. Chem. Int. Ed. 2013, 1, 104-107. [4] Qiao, J.; Liu, Y.; Hong, F.; Zhang, J. Chem. Soc. Rev. 2014, 2, 631-675. [5] Tada, S.; Thiel, I.; Lo, H. K.; Coperet, C. Chimia 2015, 12, 759-764.

[6] Roussey, A.; Gentile, P.; Lafond, D.; Martinez, E.; Jousseaume, V.; Thieuleux, C.; Copéret, C. J. Mater. Chem. C 2013, 8, 1583.

[7] Coperet, C.; Comas-Vives, A.; Conley, M. P.; Estes, D. P.; Fedorov, A.; Mougel, V.; Nagae, H.; Nunez-Zarur, F.; Zhizhko, P. A. Chem. Rev. 2016, 2, 323-421.

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un

t





Indirect MeOH Production from CO2 via Cyclic Carbonates under Solvent-Free, Metal-Free Conditions

F. D. Bobbink, P. J. Dyson*

*[email protected]

Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.

Recently, alternative strategies to reduce the energy input required for direct catalytic CO2 reduction have been developed.[1] The general strategy relies on a two-step reaction of CO2 . First, CO2 is incorporated into an organic molecule, for example in the form of a cyclic carbonate or a formamide. Subsequently, a reduction step is performed, resulting in MeOH. Both hydrogen or other reducing agents may be used for this second step.[2] Here, we have developed a catalytic system that can efficiently achieve the two-step conversion of CO2 into CH3 OH in a single-pot, under atmospheric pressure of CO2 and at a temperature inferior to 100 °C. The reducing agent comes in the form of a silane, which can be polymethylhydrosiloxane, a stable, mild reducing agent that is originally a waste from the silicon industry. Several epoxides can be tolerated under the reaction conditions, and this process represents the first example of a solvent-free, metal-free, pressure-free process for indirect MeOH production.

Fig.1 Strategy for the indirect MeOH production from CO2

References: [1] E. Balaraman, C. Gunanathan, J. Zhang, L. J. W. Shimon and D. Milstein, Nat. Chem., 2011, 3, 609–14. [2] C. Lian, F. Ren, Y. Liu, G. Zhao, Y. Ji, H. Rong, W. Jia, L. Ma, H. Lu, D. Wang and Y. Li, Chem. Commun., 2015, 51, 1252–1254.




N

Triazolium and Pyrazolium Ionic Liquids for Electrochemical Reduction of CO2

D. Vasilyev, E. Shirzadi, P. J. Dyson*

*[email protected]

Laboratory of Organometallic and Medicinal Chemistry, Institute of Chemical Sciences and Engineering, EPF Lausanne, Switzerland

Carbon dioxide conversion to useful chemical is an energy demanding process due to high kinetic and thermodynamic stability of CO2 molecule. Imidazolium ionic liquids (ILs) were the first ILs found to possess co-catalytic activity for electrochemical reduction of CO2 .[1] Herein, we report two new classes of ionic liquids capable to promote the target process (Fig. 1). One of them, which is based on triazolium cation, significantly reduce the reduction potential. Moreover, cyclic voltammetry data reveal possibility of not standard mechanism for such reduction. The second class, pyrazolium ILs, does not possess such activity. On the other hand, their stability is higher compared to imidazolium ILs, therefore they allow to reach higher current densities. These results indicate, that ionic liquids are versatile catalysts for CO2 reduction, and by tuning of their structure it is possible to adjust their catalytic performance according to someone needs.

R N N

N+ R

R N

N+ R

R N N N

N+ + R

N N R

N+ N

N+ R

Fig.1 (Left) Performance of dibuthyltriazolium bis(trifluoromethylsulfonyl)imide – one of ionic liquids from the pool. (Right) Selected cations of ILs, investigated in this work.

References:

[1] Rosen, B.A., Salehi-Khojin, A., Thorson, M.R., Zhu, W., Whipple, D.T., Kenis, P.J.A., Masel, R.I. Science 2011, 334, 643-644.




Role of the Initial Amount of Hydrogen and CO2 for Successful CO2 Reduction to Hydrocarbons

M. Spodaryk*, A. Züttel

*[email protected]

École Polytechnique Fédérale de Lausanne (EPFL) Valais/Wallis, 1951 Sion, Switzerland

The simultaneous electrochemical reduction of CO2 and H2 allows the direct production of hydrocarbons, which have the same energy density as fossil fuels, from electricity. Among the other important factors, the key factor in determining the product distribution in electrochemical CO2reduction is the cathode material. According to Hori [1] copper is a unique electrode among all investigated metals on which hydrocarbons can be obtained. Hydrides of metals and alloys [2] have the ability to adsorb CO2 and may be active catalysts for the reduction reaction as well as a source of atomic hydrogen at the surface. Our study is focused in direct electrochemical CO2 reduction on new catalytic copper-containing surfaces, such as nanorods and intermetallic alloys.

In this work we compare the electrochemical CO2 reduction process on Cu foil, Cu-containing 2- nanorods covered by carbonate and LaNi4 Cu alloy. While Cu is a metal, the carbonate provides CO3and the hydride provides H at the surface. The electrochemical CO2 reduction was carried out in the standard three electrode electrochemical cell (CE – Au plate, RE – Ag/AgCl in 3M KCl solution) using saturated with carbon dioxide 0.1M KHCO3 electrolyte (Carl Roth, 99.9%; pH = 6.65 - 6.8) with continuous CO2 bubbling (25 ml/min) trough it and stirred by a magnetic stirrer to avoid local increase of pH close to the electrode during the reduction process [3]. The reaction typically was carried out for 10 - 12 hours at a constant potentials in the range from -0.8 V to -1.1 V vs. RHE with the special focus to the reduction process at -0.982V, at which the highest Faradaic efficiencies for C2 H4 were reported [1].

Cu foil Cu-containing nanorods Cu-containing Metal hydride

Fig.1. Schematic representation of catalyst surface during and after electrochemical CO2 reduction The results of the study showed that at on the Cu foil mostly CO and H2 are produced, the

amount of C2 H4 and C2 H6 is rather low (FE <10%); Cu surface changes to CuO (dark) upon the reaction (Fig. 1). The reduction process on Cu-containing nanorods at the same current densities as Cu foil resulted in increased Faradaic efficiency for C2 products for an order of magnitude; the surface of catalyst reduced to Cu2 O+Cu (brown). The surface of LaNi4 Cu alloy during CO2 reduction was evolving mostly hydrogen. Moreover, since the plateau pressure of this alloy is above 1 bar [4] the hydrogenation of the alloy itself is accompanied by strong hydrogen evolution, which blocks the CO2molecules access to the catalyst surface. In conclusion, the amount of H2 at the catalyst surface has to be much less than the CO2 in order to obtain high Faradaic efficiency of C2 products instead of CO and H2 , ideally some CO2 has to be included in the catlyst itself. References: [1] Y. Hori, Electrochemical CO2 reduction on metal electrodes, Mod. Aspects of Electrochem. Springer, New York, 2008, 42, ch. 3, 89–189. [2] S. Kato, A. Züttel et al., The Origin of the Catalytic Activity of a Metal Hydride in CO2 Reduction. Angew. Chem. Int. Ed. 2016, 55, 6028–6032. [3] M. Spodaryk, A. Züttel et al. Role of the initial amount of Hydrogen and CO2 for successful CO2reduction to hydrocarbons. To be submitted to Chem. Comm., October 2017. [4] M. Spodaryk, A. Züttel. Hydrogen storage and electrochemical properties of LaNi5-xCux hydride- forming alloys. To be submitted to Journal of Alloys and Compounds, October 2017.




Methanation Reactor Design and Operation for Methane Production using Sabatier Process

W. Ruppen, D. Martinet, Ch. Ellert*

*[email protected]

HES-SO Valais-Wallis: Institute of Industrial Systems, Route du Rawil 47, 1950 Sion

The energetic transition into increasing utilisation of renewable energy sources will require flexible and reliable power sources. In this sense, energy storage plays a key role, as renewable energies do not supply a constant power throughout the year. However, the applications of energy storage differ in terms of grid integration (for example centralized versus distributed, different sizes) and on temporal scale (seasonal versus short-term). It appears that the choice of the technology is of highest importance to fit to the end-customer demand in terms of energy.

The Sabatier process has been used for the production of methane in the last decades. It involves the reaction of hydrogen, mostly produced via electrolysis, with carbon dioxide at elevated temperatures (200-400°C) in the presence of a catalyst, nickel or ruthenium, to form methane and water. Initial energy is required to reach operating temperature, which is then maintained by the exothermic reaction.

In our laboratory, a custom design methanation reactor has been developed and integrated into our power-to-gas installation. The reactor has a cylindrical shape with a central heating rod and an external cooling system, using air or water, to maintain a constant temperature inside the vessel, fully filled with the nickel catalyst in the form of nickel pellets (see Fig 1a). At the bottom of the reactor a mixing chamber has been installed, in which the two incoming gases are forced to mix together before reaching the catalyst region. Thermocouples monitor the temperature inside the vessel at different locations.

This reactor is able to run at temperature ranges from 50 to 400°C, pressure ranges from atmosphere to about 6 bars and input hydrogen flows up to 10slm. To characterise the performance of the reactor, the water is removed by condensation and zeolite filtering. The remaining gas mix is measured with a FTIR spectrometer and the concentration of methane and carbon dioxide can be determined (Fig. 1b).

a) b)

Fig.1 a) left: Schematic of the cylindrical reactor used for the Sabatier process to form methane from carbon dioxide and hydrogen. b) right: Methane concentration at the exit of the reactor as a function of the internal temperature





Assessment of Storage Systems


Optimization of Residential PV-coupled Battery Systems with Stacked Benefits: a Cross-country Comparison.

A. Pena-Bello*1,E. Barbour2, M.K. Patel1, D. Parra1

*[email protected]

1Energy Efficiency Group, Institute for Environmental Sciences and Forel Institute, University of Geneva, Geneva, Switzerland.

2Human Mobility and Networks Lab, Civil and Environmental Engineering Department, Massachusetts Institute of Technology, USA.

Energy storage is a technical solution for improving the dispatch ability of renewable energy technologies and it can play a pivotal role in increasing their value by providing renewable energy on demand. This study focuses on PV and residential battery storage given the increasing penetration of PV in the built environment and the growing interest in energy storage systems located very close to consumers. Since residential batteries are not economically attractive yet, we study the different applications which residential batteries can perform from a consumer perspective (i.e. to reduce the energy bill and/or environmental impact) in order to understand to which extent benefit stacking could contribute to create a positive economic case. In particular, we determine the optimal battery technology and size depending on the applications combined. Five different battery technologies currently available in the market are considered (i.e. NMC, LFP, NCA, LTO and advanced lead-acid). Applications such as avoidance of PV curtailment, demand load-shifting and demand peak shaving are considered along to the base application, PV self-consumption. Furthermore, we analyze the impact of the type of demand profile by comparing results across dwellings in Switzerland and dwellings in USA. The dataset includes 860 measured demand profiles with 1-hour resolution. This will allow us to conclude up to what point our results are region-dependent.





Fig.1: Process Concept of the High Efficiency Power-to-Methane Pilot including Heat Management and High Temperature Electrolyser (SOEC)

References: [1] Friedl, M.J. Pilot- und Demonstrationsanlage Power-to-Methane HSR: Schlussbericht. https://www.iet.hsr.ch/index.php?id=13510 (PDF) (accessed Jul 19, 2017) [2] Moebus, S. Aqua & Gas, 2017, 7/8, 26-29

HEPP High Efficiency Power-to-Methane Pilot

L.C. De Sousa1, M.J. Friedl1, S. Moebus*1

*[email protected]

1HSR Hochschule für Technik Rapperswil

The catalytic methanation reaction used in Power-to-Methane technology is strongly exothermic and releases 22% of the hydrogen calorific value as heat. That entails an overall efficiency about 60% of a Power-to-Methane system (ratio of the electrical energy used to the calorific value of the generated gas) [1].

The aim of the High Efficiency Power-to-Methane Pilot is to significantly improve the efficiency to 70% or higher and to improve the technology readiness level of the Power-to-Methane technology. The aim is reached by the development of a high-temperature electrolysis (solid oxide electrolysis cell, SOEC) and a new heat management, which uses waste heat from the catalytic methanation internally to evaporate water that is an input to the SOEC [2]. The process concept of the plant is shown in fig. 1.

The High Efficiency Power-to-Methane Pilot has an electrical input of 10kW. Industry relevant questions will be answered so that the technology scaling-up can be achieved. In addition, innovative technologies developed in Switzerland are being integrated to the plant (new methanation concepts, membrane separation technology and gas analytics). Work on the project has already begun. The demonstrator will be built in mid-2018 and results are expected afterwards.



http://www.iet.hsr.ch/index.php?id=13510

List of Participants SCCER H 6th


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SCCER Heat and Electricity Storage c/o Paul Scherrer Institut OVGA 05 5232 Villigen PSI

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