energy storage - iva · summary the need for energy storage is increasing as the pro-portion of...

Energy StorageElectricity storage technologiesIVA’s Electricity Crossroads project

© Royal Swedish Academy of Engineering Sciences, 2016P.O. Box 5073, SE-102 42 StockholmTel: +46 (0)8 791 29 00Fax: +46 (0)8 611 56 23E-mail: [email protected]: www.iva.se

IVA-R 488ISSN: 1102-8254 ISBN: 978-91-7082-919-2

Authors: Anna Nordling, Ronja Englund, Alexander Hembjer & Andreas MannbergProject Manager: Anna Nordling, ÅFEditor: Camilla Koebe, IVALayout: Anna Lindberg & Pelle Isaksson, IVA

This report is also available for download at IVA’s websitewww.iva.se

ORDLISTA

AA-CAES – Adiabatic compressed air energy storage

AEC – Alkaline electrolysis cells

CAES – Compressed air energy storage

CH4 – Methane gas

CT – Combustion turbine

DoE – US Department of Energy

EEA – European Economic Area

GW – Gigawatt

GWh – Gigawatt hour

H2 – Hydrogen gas

kW – Kilowatt

kWh – Kilowatt hour

MW – Megawatt

MWh – Megawatt hour

m3 – Cubic metre

Nm3 – Normal cubic metre

NaS – Sodium sulphur

UPS – Uninterruptible power supply

PEM – Polymer electrolyte membrane/proton exchange membrane

SMES – Superconducting magnetic energy storage

VRB – Vanadium redox battery

Wh – Watt hour

3

Contents

Summary ...................................................................................................................... 4

1. Introduction ................................................................................................................. 5

2. Electrical energy storage ............................................................................................... 6 Application ................................................................................................................... 9

3. Energy storage technologies ........................................................................................ 11 Pumped hydropower ................................................................................................... 11 Compressed-air energy storage ................................................................................... 12 Batteries ...................................................................................................................... 14 Power to gas ............................................................................................................... 17 Flywheels .................................................................................................................... 18 SMES – Superconducting magnetic energy storage ....................................................... 19 Supercapacitors ........................................................................................................... 19

4. Comparison of different storage technologies ............................................................. 20

5. Appendix .................................................................................................................... 21 Footnotes .................................................................................................................... 21 Literature list .............................................................................................................. 22

SummaryThe need for energy storage is increasing as the pro-portion of intermittent energy production in the en-ergy system increases. Different types of storage tech-nology are needed depending on demand and type of electricity generation. The most common energy storage technologies today are pumped hydropower, batteries, compressed air and flywheels.

The most common drivers and application areas for energy storage are listed below:

• Price arbitrage• Balancing energy• Black-start services• Stabilising conventional generation• Island and off-grid storage• T&D (transmission & distribution) deferral • Industrial peak shaving• Residential storage

Different energy storage technologies have different applications in the energy system. Capacity, cost, en-ergy density, efficiency level, and technical and eco-nomic life are factors that determine in which context the technologies are the most suitable. Pumped hy-dropower and compressed air, for example, are both

suitable for energy balancing, while batteries are best suited as reserve power and for over-generation and off-grid systems. But larger battery units may be used in the future for other purposes. Geographical condi-tions are examples of other factors that must be taken into consideration in applications for pumped hydro-power and compressed air energy storage (CAES).

It is likely that all of these storage technologies will be used in some form or other in the future, but the tech-nology advancing the fastest today is battery technolo-gy. One reason for this is that batteries can be used on a small scale in households and vehicles, but they can also be used on a large scale by combining multiple modules. Also, the most recent advances in Tesla’s batteries indi-cate that cost levels will fall faster than expected. Since batteries can be produced on a small scale, the threshold for widespread commercialisation is very small.

Pumped hydropower is expected to grow the most in China and India which have the right geographical con-ditions to build efficient plants. Other countries need to consider other unconventional technical pumped hy-dropower solutions, such as pumping sea/ocean water and storage in underground caverns.

Compressed air technology will likely be used the most in the USA where a number of suitable locations

5

have already been selected for compressed air plants. Projects are also in the pipeline in the EU where the first adiabatic compressed air solutions are now being developed.

Energy storage in the EU at this time is focused on three different areas: small-scale use, arbitrage and reduction of capacity peaks1. The drivers for storage markets in Europe are:

1. Use in microgrids isolated from the grid.2

2. Batteries in combination with solar cells in residential contexts (mainly in Germany at the moment).3

There are still legal barriers to overcome for energy storage, and the definition of energy storage and own-

ership rules are still unclear. In Sweden, grid compa-nies are permitted to own their stored energy, but they can only use it for the purpose of covering grid losses or to temporarily compensate for power cuts/failures. In other words: stored energy use is only permitted in emergencies. An amendment to Sweden’s Electricity Act (Ellagen) is needed if energy reserves are to be commercially attractive for grid companies.

Batteries are expected to have a larger share in the future energy system in Sweden, both in homes and as part of the future electric-powered transport system. Other forms of energy storage will be developed in Swe-den as well, and price trends will determine what these will be.

1. IntroductionThe electricity system needs to be constantly in balance, i.e. electricity production and electricity demand need to be matched every second of the day. In cases where electricity generation cannot be controlled and does not match electricity demand, the energy (electricity) needs to be stored. By being able to store surplus generated elec-tricity for use later on when demand is higher than sup-

ply, the balance in the energy system can be maintained without constant matching of production and consump-tion. This report summarises the information in a series of reports on energy storage. The focus here is energy storage through mechanical, electrical, electrochemical and chemical storage. Reports and other sources used in this report can be found in the literature list.

Storage technologies

Pumped hydropower Lead-acid batteries

Flow batteries

Molten-salt (sodium)sulphur batteries

Lithium-ion batteries

Other advanced batteries

Hydrogen gasSMES

Compressed air Capacitor

FlywheelOther chemicals

Synthetic natural gas

Electrochemical ChemicalElectricalMechanical

0 MW

50,000 MW

100,000 MW

150,000 MW

200,000 MW

Pumpe

d hy

dropo

wer

Air co

mpr

esso

r sto

rage

Flywhe

el

Lithiu

m-io

n

Molte

n sa

lt ba

tterie

s

Lead-

acid

bat

terie

s

Conden

sers

Flow b

atte

ries

Gravit

atio

n sto

rage

Nick

el m

etal

batte

ries

Hybrid

bat

terie

s

Ultra b

atte

ries

Electro

chem

ical

Lead

carb

on ba

tterie

s

Met

al air

bat

terie

s

Aqueo

us io

n hy

brid

Aqueous ion hybrid 0.02 MWMetal air batteries 1 MWLead carbon batteries 1 MWElectrochemical 1,8 MWUltra batteries 7 MWHybrid batteries 9 MWNickel metal batteries 30 MWGravitation storage 50 MWFlow batteries 75 MWCondensers 78 MWLead-acid batteries 121 MWMolten salt batteries 153 MWLithium-ion 498 MWFlywheel 988 MWAir compressor storage 1,436 MWPumped hydropower 177,392 MW

0 MW

10,000 MW

20,000 MW

30,000 MW

40,000 MW

50,000 MW

60,000 MW

Pumpe

d hy

dropo

wer

Flywhe

el

Lithiu

m-io

n

Mont

en sa

lt ba

ttery

Hybrid

bat

tery

Conden

ser

Flow b

atte

ry

Nick

el m

etal

Lead-

acid

bat

tery

Lead-acid battery 1 MWNickel metal 3 MWFlow battery 3 MWCondenser 6 MWHybrid battery 8 MWMonten salt battery 47 MWLithium-ion 138 MWFlywheel 878 MWPumped hydropower 56,491 MW

6

2. Electrical energy storage

The need for energy storage in the energy system will increase as the share of intermittent energy generation in the energy system increases. Figure 1 is a diagram of different energy (electricity) storage technologies by primary physical energy transmission technology/storage technology. This report will not cover heat storage.

The energy storage market is still relatively lim-

ited and only a few technologies have reached the commercial stage on a larger scale. Figure 2 and 3 show capacity that exists, is being planned and being developed (2014) for mechanical and electrochemi-cal storage units. The data for these diagrams comes from the US DoE Global Energy Storage Database. The storage technologies shown in Figure 2 are de-scribed in more detail in Chapter 3.

Figure 1: Storage technologies

Figure 2: Global installed storage capacity, MW.4 Figure 3: Global installed storage capacity in the EEA, MW.5

Sodium-sulphur 23 %

Lithium-ion 10 %

Compressed air 27 %

Pumped hydropower 22 %

VRB 23 %

18

38,7

58,5

69,3 68,464,8

57,6

49,5

35,1

12,6

44,1

18

28,8

22,5

14,4

4,5

2015 2020 2025 20302015 2020 2025 20302015 2020 2025 20302015 2020 2025 2030

CHINA AND JAPANEUROPEREST OF THE WORLDNORTH AMERICA

0

50

100

150

200

250

Rest of the world

Europe

China and Japan

North America

Total

2030203020202015

SEK Billion

54

135

231,3

69,3

68,4

64,8

28,8

7

Figure 4 (above): Potential of various electricity storage technologies globally 2030.6

Figure 5 (left): Anticipated energy storage market development.7

Figure 6 (below): Energy storage market development in SEK billions.8

0 20 40 60 80 100 120 140 160 180 200

0

200

400

600

800

1000

1200

1400

1600

GW

h

GW

Table 1: Applicability of stored energy.10

Role in the energy system

Func

tion

The transmission system and centralised storage (national and European level)

The distribution system and regional storage(city and district level)

Consumer (building and residential level)

Balance between supply and demand

• Seasonal/weekly/daily/hourly variations• Substantial geographical imbalances• Large variations due to intermittent electricity generation

• Daily/hourly variations • Daily variations

Distribution (moving energy)

• Voltage and frequency control• Additional peak production• Power market• International market

• Voltage and frequency control • Power market

• Aggregation of small amounts of stored energy to meet distribution needs (capacity problems and loss reduction)

Energyefficiency improvement

Better energy efficiency in the global energy mix

Load and storage control for better efficiency in the distribution grid

Local generation and consumption, change in behaviours, increased value of local generation

Table 2: Application areas of different storage technologies. Suitable technology for the application More technology development or further cost reduction needed Technology not suitable for the application

Electricity quality and stability

Local energy optimisation

Moving energy in time (days or longer)

Investment defer-ment in T&D

Reserve power/UPS

Pumped hydropower

Compressed air

Lead-acid batteries


Sodium-sulphur batteries

Flow batteries

Supercapacitors

SMES

Flywheels

Inve

stm

ent

nee

d *

Tec

hn

olo

gica

l ris

k

Research Development Demonstration Market launch Mature technology Time

Synthetic natural gas

Hydrogen gas

SMES

Lithium-ion applications

Lithium-ion technology

Molten saltFlywheel


Compressed air storage

Adiabatic compressed air storage

Supercapacitor

Flow batteries

Pumped hydropower

8

Figure 7: Maturity of different storage technologies.9

9

In Revisiting Energy Storage11 the Boston Consulting Group (BCG) describes the estimated market potential of various technologies. This is illustrated in Figure 4. Batteries are expected to account for about half of all electrical energy storage. In terms of electrical power, pumped hydropower and compressed-air technology respectively are expected to dominate the market in 2030. These technologies are expected to gradually be replaced by hydrogen gas storage from 2020. The bat-tery storage technologies that are expected to dominate the market are sodium-sulphur batteries (NaS), VRB (vanadium redox batteries) and lithium-ion batteries.

The graph above shows one market scenario, but it may change due to rapid development battery prices, see Figure 11.

BCG also estimates that sales of storage technologies will reach SEK 54 billion in 2015, SEK 135 billion in 2020 and SEK 234 billion in 2030 (Figure 5). The high-est growth is expected to be made in North America, China, Japan and Europe.12

Figure 6 describes anticipated development in dif-ferent markets.

As mentioned earlier, the different storage technolo-gies are at different stages of commercial maturity. Figure 7 show where the different technologies were on the maturity scale in 2013.

Application

Different energy storage technologies have different ap-plication potential and limitations. Table 1 shows the various functionalities in different parts of the energy

system. Europe is focusing on integrating intermittent electricity generation in the energy system, while the US is placing more emphasis on ways to compensate for weaknesses in its electricity system. Table 2 shows application areas that are the most suitable for each of the technologies listed above.

Reserve powerStored energy can be used as reserve power. Below is a description of different types of reserve power.

Spinning reserve powerCapacity which is online and can respond within 10 minutes to compensate for generation or transmission interruptions. Frequency-responsive spinning reserve power responds within 10 seconds to maintain the system’s required frequency. Spinning reserve power is the first type used when there is a deficit.

Supplemental reservesElectricity generation capacity that can be offline or that consists of a block of curtailable and/or interrupt-ible load and that can be available within 10 minutes. Unlike spinning reserves, supplemental reserves are not synchronised with the grid’s frequency. Supplemental reserves are used after all spinning reserve capacity is online.

Back-up supplyReserve power that can be deployed within an hour. This is mainly a back-up for reserves. It can also be used as commercial reserves and for selling.

Figure 8: Vehicle battery systems via aggregators.13

Aggregator 1

GRID OWNER

Aggregator 2Aggregator 3

Traditional grid servicesGrid services integrated into vehicles

Figure 9: Common energy storage system compared to an optimised energy storage system.14

10

Electric vehiclesSince electric vehicles could potentially function as small distributed energy storage resources, they could potentially serve as an aggregated energy solution with smart technology and control. Electric vehicle batteries could be used as distribution units in the en-ergy system by way of an aggregator. Figure 8 illus-trates how a system like this would work.

Solar cells and battery storageSubstantial efficiency gains can be made through con-trolled battery charging and solar energy input into the grid. Figure 9 shows regular storage compared with grid-optimised storage.

Electricity ActThere are still legal barriers for energy storage and the definition of energy storage and the rules for owner-ship are unclear. In Sweden grid companies are per-mitted to own their stored energy, but they can only use it for the purpose of covering grid losses or to tem-porarily compensate for power cuts/failures. In other words: stored energy may only be used in emergencies. An amendment to Sweden’s Electricity Act (Ellagen) is needed if energy reserves are to be commercially at-tractive for grid companies.15

Charging during high energy production periods

Reduceinput to grid

Reduced input capacity increaseslocal grid capacity by 66%

Maximum input to the net

Charging until battery is full

Mid-day production peak fed into grid

COMMON ENERGY STORAGE SOLUTION

OPTIMISED ENERGY STORAGE

6 a.m. Noon 6 p.m.

6 a.m. Noon 6 p.m.

Charging during high energy production periods

Reduceinput to grid

Reduced input capacity increaseslocal grid capacity by 66%

Maximum input to the net

Charging until battery is full

Mid-day production peak fed into grid

COMMON ENERGY STORAGE SOLUTION

OPTIMISED ENERGY STORAGE

6 a.m. Noon 6 p.m.

6 a.m. Noon 6 p.m.

Figure 10: Diagram of a pumped hydropower plant.17

Table 3: Pumped hydropower plants in Sweden.

Drop Power (MW) Production (GWh/year) Constructed

Letten 191 36 65 1956

Kymmen 88 55 34 1987

11

3. Energy storage technologies

Pumped hydropower

In a pumped hydropower facility, water with low po-tential energy is pumped from a reservoir at a low el-evation to a reservoir at a higher elevation. The pump uses electricity to increase the potential energy in the water; a form of energy that can be stored. The facility is run as a pumping station when surplus electricity is available. When electricity is needed the pumping fa-cility can serve as a normal hydropower plant. Water is released from the highest reservoir through a pipe taking it to a turbine connected to a generator. The

potential energy in the water is first converted into ki-netic energy in the pipe and then into electrical energy after the generator.

A diagram of a typical pumped hydropower plant is presented in Figure 10.

Pumped hydropower is a mature and established technology that is well-suited for large-scale applica-tions but not yet implemented in small-scale solutions. Europe, including Norway, has a few remaining loca-tions that are suitable for pumped hydropower. There are some environmental considerations that must be taken into account as these plants have a significant impact on the natural environment.16

Out�ow

Plenum chamber

Transformer valve

In�ow

Reservoirs

Breaker

Power chamber

Table 4: Technical data for pumped storage hydropower plants.18

Pumped hydropower plant

Used for Load and energy peaks, minute reserves

Usage time 1 to 24 hours

Capacity Up to 5,000 MW depending on size of dam and elevation difference

Energy density 0.35–1.12 kWh/m3

Efficiency level 65–85 %

Losses 0–0.5 % per day

Start-up time Seconds to minutes

Life 50–100 years

Production phase Commercially available

Investment cost SEK 4,500–32,400/kW (depending on location)

Geographical requirements Elevation difference

Figure 11: Pumped hydropower plants by geography.

12

In Sweden Fortum has two pumped hydropower plants: Letten and Kymmen. These two plants are de-scribed in Table 3.

Pumped hydropower has the greatest potential in China and India which have suitable geographical locations for effective plants. Other countries in the world need to consider more unconventional designs such as pumped hydropower using saltwater and un-derground water reservoirs.19

Globally in 2011 there were 280 plants with a com-bined capacity of 132 GW. Around 40 of these plants have a capacity of between 50 and 2,100 MW.20 Figure 11 shows a geographical breakdown for the plants.

Pumped hydropower facilities have a short response time, which means they can be used for both voltage and frequency control, spinning and non-spinning re-serves, as well as for arbitrage and system capacity support.21

The fact boxes above show technical data for pumped hydropower plants.

Compressed-air energy storage

Systems based on compressed-air energy storage (CAES) use electricity (when supply is greater than demand) to compress air in a reservoir, either in underground cav-erns/aquifers, or vessels or pipes above ground. When demand for electricity is instead higher than the sup-ply, the compressed air is heated, expanded and taken through an expander or a conventional turbine to pro-

duce electricity. Figure 12 is a diagram of a CAES plant with subterranean storage in a cavern in a salt mine/mine.

In the compression process a large amount of heat escapes and if this heat is not recycled, the efficiency of CAES plants is low (42–54 percent). The current generation CAES plants do not recycle the heat and the challenge for the next generation CAES plants is the very high temperatures of 650°C or more, which affect the choice of materials used for heat exchangers.

CAES is the only commercially viable, large-scale storage technology aside from pumped hydropower. There is currently one facility in Germany (290 MW) and one in Alabama, USA (110 MW). Additional pro-jects are in the pipeline. CAES technology is expected to be used in the USA where a number of locations have already been selected. In the EU further develop-ment of CAES technology is expected, and in particu-lar the first adiabatic CAES technology facility, ADELE, is proving to be successful.22

ADELE is a project where advanced adiabatic CAES technology (AA-CAES) is used (so-called second gen-eration compressed air technology). Adiabatic here means that the heat generated in the compression process is used to increase energy efficiency. The goal is to increase energy efficiency to a level of 70 percent. ADELE is a demonstration plant that is ex-pected to be operational in 2016.23

The second generation CAES technology has the po-tential for lower installation costs, higher efficiency and shorter construction times compared to the first genera-

Other 20 %

USA 16 %

Japan 16 %

EU 30 %

China 18 %

Table 5: Compressed air technology.25

Compressed air technology

Used for Load and energy peaks, minute reserve

Usage time 1 to 24 hours

Capacity Depending on storage size

Energy density 0.5–0.8 kWh/m3 (60 bar, the energy density depends on the pressure)

Efficiency level Common compressed air technology: 42–54 %, Advanced adiabatic compressed air technology: up to 70 %

Losses 0–10 % per day

Start-up time MinutesAfter three minutes 50 % of the capacity is availableAfter 10–14 minutes 100 % of the capacity is available

Life 25–40 years

Production phase Common compressed air technology: commercially availableAdvanced adiabatic compressed air technology: development phase

Investment cost 6,000 (common CAES)–9,600 (AA-CAES) SEK/kW

Geographical requirements Close to a salt dome, empty gas field or aquifer

Figure 12: Diagram of a compressed air storage facility and adjacent electricity generation plant.24

Storage

Salt dome

Generator

Fuel(natural gas)

Engine Compressor

Heatrecycling

High-pressureturbine

Low-pressureturbine

13

Figure 14: Cost development for lithium-ion batteries.29

Figure 13: Different types of batteries and their estimated installed capacity (MW) in the world 2014.28

0

50

100

150

200

250

300

350

400

Installed capacity 2013–2014

Existing capacity 2012

Sodium-sulphurbattery

Lithium-ion

battery

Advancedlead-acidbattery

Redox�ow

battery

Nickelcadmiumbattery

Otherbatteries

MW

2005 2010 2015 2020 2025 2030

0

2,500

5,000

7,500

10,000

12,500

15,000

17,500

Cost estimated in publications – highest and lowest

Publications, reports and journals

Cost of Tesla Power Wall

Cost of Tesla Power Block

SE

K/k

Wh

14

tion. In one type of second generation CAES technology a natural gas fired combustion turbine (CT) is used to generate heat during the expansion process. In these plants about two thirds of the electrical energy pro-duced is generated from the expansion turbine and one third from the CT. A new compressor design and an advanced turbo unit also improves production in CAES systems based on the technology without a CT.

CAES plants that store compressed air above ground are typically smaller than plants with underground storage. The capacity of small plants is often between 3 and 50 MW with output of 2–6 hours.26

CAES plants with above ground storage are located at suitable sites, but are more expensive to build (cal-culated as SEK/kW) than plants with subterranean storage. The most cost-effective plants are CAES plants with subterranean storage with a storage capacity of up to 400 MW and an output of 8–26 hours. The loca-tion of these plants involves exploiting and verifying storage options based on geological information indi-cating suitability for a CAES plant in the area.27 The adiabatic CAES technology is fairly mature technology, particularly in the case of large-scale centralised ap-plications.

Batteries

Many different types of batteries are being developed today. The batteries that exist and their market share are shown in Figure 13. The reason for the big jump for lithium-ion batteries in 2014 is the dramatic price development.

Figure 15: Current cost and future anticipated development of different types of lithium-ion batteries.31

Figure 16: Cost for large-scale battery storage, comparison of current and expected.32

CostsThe big challenge for batteries is cost, despite the fact the cost is expected to fall dramatically over the next decade, partly due to economies of scale and partly due to technical innovation. Figure 14 shows the cur-rent costs and the expected cost trend for lithium-ion batteries in electric vehicles. Note also the cost level for the new Tesla batteries that have recently entered the market.

Figure 15 shows different types of large-scale lithi-um-ion batteries and expected cost trends.

Figure 16 shows a cost comparison between differ-ent types of batteries, current and expected.

Battery cost predictions are, however, constantly

changing. Recently, for example, (1 May 2015) Tesla launched its own battery, Tesla Powerwall, and in-dustrial battery, Tesla Powerblock. Powerwall batter-ies are sold for USD 3,500 (equivalent to around SEK 30,000) and have a storage capacity of 10 kWh.30 This is equivalent to a price of USD 350/kWh and is also for a small-scale system. The industrial battery is sold for USD 250/kWh, which is equivalent to about SEK 2,000/kWh.

MarketBoston Consulting Group estimates that the in-creased total market potential for storage technolo-gies will be an additional 300 GW over and above the

SE

K/K

Wh

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

202020172014

Lithium cobalt

Lithium nickel cobalt aluminium

Lithium manganese spinel

Lithium nickel manganese cobalt

Lithium ironphosphate

Lithium titanate

6,800

5,950

5,100 5,1005,525

3,655 3,7404,250

2,550 2,5502,380

1,785

3,400

2,720

1,912 2,082

1,5301,785

SE

K/K

Wh

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

202020172014

Sodium metal halide batteries



Advanced lead-acid batteries

Flow batteries

5,780

5,1004,675 4,675 4,675

2,550

3,952

34002975

4250 4250

1700

4,547 4,5474,148

Figure 17: Geographical distribution of current and anticipated installed battery capacity.33

MW

0

50

100

150

200

250

300

Planned and under construction

Installed capacity

ItalySpainSouth KoreaGermanyCanadaUnited KingdomChileChinaUSAJapan

277

191

106

59

35 3218

0 2 2 14 4 54313 10 810

16

existing 100 GW. Batteries are expected to account for almost 50 percent of the total investment in the market in 2030. Batteries are, however, expected to account for only a small part of the total installed storage capacity. The following market share is ex-pected in 2030.34

• Sodium-sulphur: 23 percent of the market, SEK 582 billion

• Vanadium redox (VRB): 18 percent of the market, SEK 448 billion

• Lithium-ion: 10 percent of the market, SEK 258 billion

Total investments in the battery market are expected to be equal to SEK 1,280 billion.

The market share estimated by the Boston Consult-ing Group above can, however, be questioned as other market predictions indicate that lithium-ion batteries are expected to dominate the market in electrochemi-cal energy storage.35

Figure 17 shows the current installed battery capac-ity and planned capacity.

Battery technologyBelow is a more detailed description of some of the various battery technologies.

Important parameters for a battery’s usefulness are its discharge speed (how fast the battery discharges), depth of discharge (how much of the total capacity is used in cyclic operation, i.e. if the depth is 20 per-cent, the battery is delivering 20 percent of its total capacity) and the number of discharge cycles during the battery’s life.

Sodium-sulphur (molten salt) batteriesSodium-sulphur batteries (NaS) consist of liquid so-dium and sulphur. This battery technology is mature and has a system efficiency of 80 percent.36 The ex-pected life is 15 years or 4,500 cycles.37

Energy density of this type of battery is around 60 Wh/kg and they cost around SEK 4,800/kWh in 2014.38

Lead-acidThis battery technology is also mature. The battery life varies greatly depending on the application, dis-charge speed and the number of discharge cycles.

Lead-acid batteries are very widely used in com-bination with small-scale renewable energy produc-tion. In 1995–2009, for example, 50,000 solar battery systems were installed in homes in Morocco, and in Bangladesh 3.5 million homes have solar battery sys-tems.39

The main problem for many lead-acid batteries is that they still have a low depth of discharge (less than 20 percent), low number of life cycles (fewer than 500) and a short life (3–4 years).

The energy density is around 50 Wh/kg, which is generally lower than for lithium-ion batteries. New versions of lead-acid batteries have, however, demon-strated significantly better properties, such as 2,800 cycles, 50 percent discharge depth and a life of 17 years.40

Lithium-ionLithium-ion batteries have high energy density and speed of discharge compared to other batteries. They are therefore efficient relative to their size and this is

Table 6: Data for lithium-ion batteries.41

Lithium- Cathode Anode ElectrolysisEnergy density

(Wh/kg)Number of cycles

2014SEK/kWh

Iron phosphate (LFP) LFP GraphiteLithium-

carbonate85–105 200–2,000 3,850–5,950

Manganese oxide (LMO)

LMO GraphiteLithium-

carbonate140–180 800–2,000 3,150–4,900

Titanium oxide (LTO)

LMO LTOLithium-polymer

80–95 2,000–25,000 6,300–15,400

Cobalt oxide (LCO)

LCO GraphiteLithium-

carbonate140–200 300–800 1,750–3,500

Nickel cobaltaluminium (NCA)

NCA GraphiteLithium-

carbonate120–160 800–5,000 1,680–2,660

Nickel manganesecobalt (NMC)

NMCGraphite,Silicone

Lithium-carbonate

120–140 800–2,000 3,850–5,250

Electricity from intermittent

electricity generation

Electrolysis production of

H2

Sabatier reactionproduction of

CH4

Distribution example gas grid

17

constantly being improved. They have a high efficien-cy level of 80–90 percent.

Lithium-ion batteries consist of an array of chemi-cal combinations, all with unique properties and costs. Table 6 shows the different types of lithium-ion batteries that exist and technical data for them.

One of the main challenges for lithium-ion batteries is safety. Due to their high energy density, the flam-mability of lithium and the oxygen content, they can overheat and start to burn.42

Flow batteriesUnlike other batteries, a flow battery has liquid elec-trodes. The liquid electrodes can be stored outside the battery cell, allowing larger volumes to be stored. This is one of the benefits of flow batteries and an-other is that they have short reaction times. Flow batteries also have a long life due to the fluid elec-trodes. The drawback with these types of batteries is that they have low energy density and that, due to

their size, they are not suitable for mobile applica-tions.

Power to gas

Power to gas (P2G) is a method used for large-scale storage of electrical energy in the form of gas. The concept can be briefly described as electricity being used to produce hydrogen gas by means of electrolysis.

The technology can, for example, be used to take surplus electricity from intermittent electricity gen-eration, i.e. from wind and solar. The hydrogen gas produced can, for example, be used to boost biogas production, or can be used directly or stored in gas grids. The hydrogen gas produced in a Sabatier reac-tion can be used to produce methane gas directly.

The diagram in Figure 18 illustrates the production process for hydrogen gas (H2) and subsequent produc-tion of methane gas (CH4)

Figure 18: The production process for hydrogen gas (H2) and subsequent production of methane gas (CH4)

Table 8: Power to gas, CH4 production.44

Power to gas, CH4 production

Used for Long-term storage, grid balancing

Usage time Seconds to minutes

Capacity kW–GW

Energy density 9.81 kWh/Nm3



Start-up time Minutes to hours

Life 20 years

Production phase Commercially available

Investment cost 21,600 SEK/kW

Geographical requirements None

Table 7: Power to gas, H2 production.43

AEC: Alkaline electrolysis PEM: Polymer electrolyte membrane/Proton exchange membrane

Power to gas, H2 production

Used for Long-term storage, grid balancing

Usage time Seconds to minutes

Capacity kW-GW

Energy density 3 kWh/Nm3



Start-up time AEC: minutes, PEM: seconds

Life AEC: Degrades to 75 % over 10 years, PEM: 5–10 years

Production phase AEC: commercially available, PEM: prototype

Investment cost 6,300–9,900 SEK/kW

Geographical requirements None

18

Table 7 and 8 show information on P2G in the two cases where hydrogen gas (H2) and methane gas (CH4) are produced.

In general the technology is very flexible in terms of capacity and is particularly well-suited for decentral-ised applications. No specific geological conditions are required. In 2025 storage costs (calculated as levelised cost of energy, LCOE) for 180 cycles a year are expected to be SEK 1.30/kWh, and for 360 cycles a year about SEK 1.15/kWh.45

Extensive research is taking place to develop tech-nology for hydrogen gas storage using a number of different methods.

Flywheels

A flywheel stores kinetic energy. A high-mass rotor spins fast and without resistance using magnetic bear-ings. By reducing the rotor speed energy is extracted and by adding energy to the rotor it spins faster and the energy is stored.

In most modern flywheel technologies the rotor sys-tem is enclosed for reasons of safety and efficiency. It is usually in a protective steel case encapsulating the rotor, engine/generator and other rotating parts. This also prevents it from causing harm to personnel and surrounding equipment in the case of a possible ro-

Table 9: Comparison between SMES, flywheels and supercapacitors.

Efficiency level Life Discharge speed Energy density (Wh/kg)

Flywheels 95 % 20 years 0.1–20 minutes 200

SMES 90 % 30–50,000 cycles 1–8 seconds 40–60

Supercapacitors 95 % 1,000,000+ cycles 0.001–3 seconds 1–30

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tor failure. Encapsulation also has a positive impact on the flywheel’s efficiency. The rotor often spins in a vacuum enclosure or one filled with low-friction gases such as helium.

Flywheel technology has high energy density which means that it requires little space to store a relatively large amount of energy. Response times for flywheel technology are also very short, often 4 milliseconds or shorter, and they can be deployed for short periods of up to an hour. A flywheel can be dimensioned at be-tween 100 kW and 1,650 kW. They have an efficiency level of around 93 percent and an estimated life of around 20 years.46

Thanks to the short response time, a typical appli-cation for flywheels is an uninterrupted power supply (UPS).47

Beacon Power has developed large-scale flywheel solutions such as a unit with a capacity of 20 MW (200 units of 100 kW, around 25 kWh) which is mainly used to correct frequency imbalances in New York. The use of flywheel technology solutions for voltage quality applications is expected to increase signifi-cantly over the next decade.48 Sales are expected to increase significantly in Europe and Asia, while the US is expected to remain the largest market until 2021.49

SMES – Superconducting magnetic energy storageSMES is a type of magnetic energy storage that uses superconductors. SMES has a high efficiency level of over 90 percent and is based on instantaneous charg-ing/discharging cycles, making SMES extremely well-

suited for electricity quality support solutions. SMES solutions are generally small scale with a current maximum storage capacity of around 10 MW. The physical size of the spool is a limiting factor for this technology. The extremely heavy weight of magnetic systems a natural obstacle for upscaling. It is essen-tially impossible to build and implement larger scale SMES solutions. Increasing the thickness of the super-conducting threads would raise the heat that develops and lower efficiency. Also, the effects of the magnetic field around the equipment has not yet been thorough-ly analysed.

SMES is a technology that is the most established among the technical high voltage solutions in installa-tions in Europe, Japan and the US. The US is expected to be an important market for SMES technology, along with Germany and Japan, but not on the same level as the fast markets for flywheel and supercapacitor technologies.50

Supercapacitors

The advantages of supercapacitors are their high en-ergy density, efficiency and the number of possible dis-charge cycles during their life; they have the ability to charge and discharge in more than one million cycles.

Supercapacitor technology is on the cusp of a break-through in the market for storage solutions for power grids. The US, Korea and Japan are expected to be the main markets for supercapacitors.51

Table 9 shows a comparison of SMES, flywheels and supercapacitors.

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4. Comparison of different storage technologies

As indicated earlier, the various storage technologies have different advantages and drawbacks. The table below shows a comparison of the different types of storage technology presented in this report.

Energy storage method Capacity (MW) Usage time Efficiency level (%) Start-up time

Pumped hydropower plant < 5000 1–24 h 65–85 s-min

Compressed air technologyDepends on

storage capacity1–24 h

42–54 (normal)70 (advanced

adiabatic)min

Lead-based batteries 0,001–50 s–3 h 60–95 -

Lithium-based batteries 0,001–0,1 min–h 85–99 -

Flow batteriesVanadium redox batteries

0,03–7 s–10 h 85 ms

Flow batteriesZinc bromide batteries

0,05–2 s–10 h 70–75 ms

Sodium-sulphur batteries 0,5–50 s–h 85–90 -

Power to gas, H

2 productionkW–GW s–months 62-82 s-min

Power to gas, CH4 production

kW–GW s–months 49–56 min–h

Flywheels 0,002–20 s–min 95 s-min

SMES 0,001–10 s 90 ms

Supercapacitors 0,01–1 ms–s 95 ms

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5. Appendix

FOOTNOTES

1. Normark, B., et al, How can batteries support the EU electricity network?, Insight Energy, November 2014.





6. Boston Consulting Group, Revisiting Energy Storage – There Is a Business Case, 2011.

7. https://www.bcgperspectives.com/content/ar-ticles/energy_environment_solar_pv_plus_bat-tery_storage_poised_for_takeoff/


9. SBC Energy Institute, Electricity Storage, September 2013.

10. DG ENER Working Paper, The future role and challenges of Energy Storage, European Commission.



13. Normark, B., et al, How can batteries support

the EU electricity network?, Insight Energy, November 2014.

14. IRENA, Battery storage for renewables: market status and technology outlook, January 2015.

15. POWER CIRCLE, Energilager i energisystemet, September 2014.

16. Boston Consulting Group, Electricity Storage- Making Large – Scale Adoption of Wind and Solar Energies a Reality, 2010.


18. iNTiS GmbH, Power to Gas, NEND, May 2013.

19. Visiongain, The Energy Storage Technologies (EST) Market 2011–2021, 2010.


21. Electric Power Research Institute, Electricity Energy Storage Technology Options – A White Paper Primer on Applications, Costs and Benefits, 2010.


23. RWE, http://www.rwe.com/web/cms/mediablob/en/391748/data/235554/1/rwe-power-ag/com-pany/Brochure-ADELE.pdf


25. iNTiS GmbH, Power to Gas, NEND, May 2013.

26. DOE/EPRI, Electricity Storage Handbook in Collaboration with NRECA, 2013.

22

27. DOE/EPRI, Electricity Storage Handbook in Collaboration with NRECA, 2013.


29. Nykvist, B., Nilsson, M., Rapidly falling cost of battery packs for electric vehicles, nature climate change, 23 march 2015.

30. http://teslaclubsweden.se/tesla-powerwall/





35. Hanson, M., et al., Energilagring i Energi-systemet, Power Circle, September 2014.

36. Electric Power Research Institute, Electricity En-ergy Storage Technology Options – A White Paper Primer on Applications, Costs and Benefits, 2010.

37. Electric Power Research Institute, Electricity En-ergy Storage Technology Options – A White Paper Primer on Applications, Costs and Benefits, 2010.






43. INTIS GmbH, Power to Gas, 2013.

44. INTIS GmbH, Power to Gas, 2013.

45. Boston Consulting Group, Electricity Storage- Making Large – Scale Adoption of Wind and Solar Energies a Reality, 2010.







LITERATURE LIST

VINNOVA, Lösningar på Lager – Energilagring-stekniken och framtidens hållbara energiförsörjn-ing, 2012

Boston Consulting Group, Revisiting Energy Storage – There Is a Business Case, 2011

Visiongain, The Energy Storage Technologies (EST) Market 2011–2021, 2010

Boston Consulting Group, Electricity Storage-Mak-

ing Large-Scale Adoption of Wind and Solar Energies a Reality, 2010

INTIS GmbH, Power to Gas, 2013

Electric Power Research Institute, Electricity Energy Storage Technology Options – A White Paper Primer on Applications, Costs and Benefits, 2010

DOE/EPRI, Electricity Storage Handbook in Collabo-ration with NRECA, 2013

23

ESA, http://www.electricitystorage.org/technology/technology_applications/spinning_reserve

RWE,http://www.rwe.com/web/cms/mediablob/en/391748/data/235554/1/rwe-power-ag/company/Brochure-ADELE.pdf

ÅF, Green Advisor Report 2013:01, 2013

KTH, På väg mot en elförsörjning baserad på enbart förnybar el i Sverige, 2013

EscoVale Consultancy Services, Electrical Energy Storage, 2010

prognos, The significance of international hydropow-er storage for the energy transition, 2012

Bradbury, K., Energy Storage Technology Review, 2010

Hirth L., et.al, Energy Storage in a System Perspec-tive Interim Report, 2010

McKinsey & Company, Storage in the European pow-er sector – Game changer or hype?, 2013

INSIGHT_E, Policy Report 1 – How can batteries sup-port the EU electricity network?, november 2014

IRENA, Battery storage for renewables: market status and technology outlook, january 2015

HSBC Global Research, Energy Storage – Power to the People, september 2014

T&D World Magazine, SDG&E Integrates EVs and Energy Storage into California’s Energy and Ancil-lary Service Markets, 24 february 2015

Nykvist, B., Nilsson, M., Rapidly falling costs of bat-tery packs for electric vehicles, nature climate change, 23 march 2015

SBC Energy Institute, Electricity Storage, September 2013.

POWER CIRCLE, Energilager i energisystemet, Septem-ber 2014

Jernkontoret, www.energihandbok.se/lagring-av-elektrisk-energi/

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