alternative approaches for ocean wave energy harvesting
TRANSCRIPT
FP7-ENERGY-2012-1-2STAGE: Future Emerging Technologies
Grant Agreement: 309139
Alternative Approaches for
Ocean Wave Energy Harvesting:
Dielectric Elastomer Generators
Vertechy R.1,4, Fontana M.2,4 , Damiani F.3,4
1 University of Bologna, Italy2 University of Trento, Italy
3 Cheros S.r.l, Italy4 Scuola Superiore Sant’Anna, Italy
Dielectric Elastomer Generators (DEGs):
• What they are
• Potentials for ocean wave energy harvesting
Summary of results on the development of Power-Take-Off
(PTO) systems based on DEGs (2012 - 2017):
• Small scale prototypes tested in wave tanks and Hardware-In-the-
Loop (HIL) set-ups;
• Identification of suitable materials
‒ Limit performances
‒ Lifetime performances
• Prototype manufacturing
‒ Electro-mechanical conversion unit
‒ Power electronics
Vision and Future plans
Outline
Dielectric Elastomer Generators (DEG): Generalities
Dielectric Elastomer Transducers (DETs) are electrostatic devices that convert
electrical energy in mechanical energy and vice versa:
• They are deformable capacitors;
• They can be used as sensors, actuators and generators.
The key active element of DETs comprises:
• A thin membrane made of a Dielectric Elastomer (DE) material;
• Compliant electrodes.
DE
membrane
compliant
electrodes
DET Generators (DEGs) convert mechanical energy into direct electricity by
exploiting capacitance variation induced by material deformation.
max2 1
min
CV V
C
2V1V
maxC minC
Dielectric Elastomer Generators (DEG): Generalities
Advantageous properties of DEGs:
incompressible;
large deformability (up to 600%);
large dielectric strength (up to 300 MV/m);
good dielectrics (r 2 – 10)
low mass density (1000 kg/m3);
good electro-mechanical conversion efficiency
(theor. almost load-independent and up to 95%);
softness ( 15 – 3000 kPa)
good toughness
(in the range of 1-10 MJ/m3 and beyond, still within the elastic range)
good corrosion and fouling resistance;
integrated sensing functions;
silent operation;
easy to manufacture and handle;
moderate or low cost (5-50 €/kg).
DEGs are perfectly suited to be used as Power Take-Off (PTO) systems in ocean Wave Energy Converters (WECs)!
high energy density
(theor. up to 3 kJ/kg)Dielectric Elastomer Generators (DEG): Potentialities
Polymeric Oscillating Water Column
(PolyOWC, Nov. 2012)
WECs with DEG PTO: Scaled Prototypes and Wave Tank / HIL Tests
Aug. 2014
1:40 scale
Max Power: 871mW
( 350 kW full scale )
E.D.: 138 J/kg
w-t-w effic.: 18.6%
VHB - CG electrodes
R = 125 mm, t = 93 m
p = 4
WECs with DEG PTO: Scaled Prototypes and Wave Tank / HIL Tests
Polymeric Oscillating Water Column
(PolyOWC, Nov. 2012)
May and Aug. 2016
1:25 scale
Max Power: 3.8W
( 300 kW full scale )
E.D.: 135 J/kg
w-t-w effic.: 21%
VHB - CG electrodes
R = 195 mm; t = 2 x 86 m
p = 3.4
WECs with DEG PTO: Scaled Prototypes and Wave Tank / HIL Tests
Aug. 2014
1:40 scale
Max Power: 871mW
( 350 kW full scale )
E.D.: 138 J/kg
w-t-w effic.: 18.6%
VHB - CG electrodes
R = 125 mm, t = 93 m
p = 4
DEG
• PDMS film
- R = 65 mm;
- p = 1.1;
- t = 160 m
• SR film
- R = 65 mm;
- p = 1.6;
- t = 85 m
in 2016
1:30 – 1:40 scale
Tests without electrical activation
• Negative stiffness compensation
mechanism to tune system impedance
• Max. achievable power: 0.7 W
( 105 - 280 kW full scale )
WECs with DEG PTO: Scaled Prototypes and Wave Tank / HIL Tests
DRUMWEC
pressure
differential
system
June 2017
1:10 scale
Target Power: 100W
( 310 kW full scale )
VHB - CG electrodes
R = 4 x 200; t = 14 x 86 m
p = 3.4
June 2017
1:15 – 1:20 scale
Target power: 1-20W
( 40-300 kW full scale )
E.D.: 200/300 J/kg;
p-t-w effic.: 35-47%;
PDMS – CB electrodes
VHB - CG electrodes
R = 175-225 mm,
t = 0.2-1.2 mm
WECs with DEG PTO: Scaled Prototypes and Wave Tank / HIL Tests
Identification of Materials for DEG PTOs: Performance Limits
GM
[%]
Discharging time
constant: 240s - 40s
Viscous losses: 13%
PDMS
(Wacker or
Parker)
SR/NR
(Hygenic
Corp.)
ED
[J/Kg]352 - 510 412 - 590
MtE
[%]67 – 76 61 - 74
Price
[$/kg]2 - 10 1 - 2
Long-Term Performances of DEG PTOs: High-Cycle Electrical Fatigue
PDMS
SR/NR
75 MV/m
( > 300 J/kg )
Better Performances Expected on:
• PDMS with electrodes made by
automated processes (screen
or inkjet printing);
• SR/NR if membranes are
realized in a cleaner
environment.
DEG PTO Manufacturing: Electrode Deposition and Overall Assembly
PREPARATION
PET substrate
Elastosil® Film
Pouring mask
Mixture
POURING BLADING(a) (b) (c)
Additional areas
for electrodes contact
MEMBRANE ASSEMBLY
First half
Second half
Electrode 1
Electrode 2 (opposite side)
BONDING(d) (e)
Commercial Dielectric Layers
Advantages:
• Simple and cheap
• Not requires high
precision
• Use of commercial
components
• Scalable
• Safe and not polluting
(no dangerous solvents
employed)
Roll: 0.2m x 30m
DEG PTO Power Electronics: Design, Manufacturing and Testing
Multilevel Dual Active Bridge Bidirectional Converter
Features ValueCore ETD59/31/22-3C90Switching frequency 100 kHzRatio 1:1Primary turns 105Secondary turns 105Estimated efficiency(evaluated from datasheetvalues)
97% (better than)
Testing
WECs with DEG PTO: Modelling and Techno-Economic Evaluation
Assumptions
• Membrane life: 7-years;
• 1D, SF (10MW), BF (25MW)
Main Results:
• Possible LCOE <150 £/MWh
• BEP: 3-7
Significant reduction in LCOE can
only be achieved if:
• The cost of Structure and
Prime Mover (SPM) is reduced;
• New materials are used for
SPM construction.
Vision and Future Plans: Fully Elastomeric WEC
DEG PTO Fibre-Reinforced Elastomeric Composites Offshore structures
• Power-Take-Off (PTO) system based on DEG
• Structure and Prime Mover (SMP) based on Fibre-Reinforced Inflatable
Elastomeric Composites
Vision and Future Plans: Fully Elastomeric WEC
Targeted Key Performance Indices:
As compared to present WECs:
• Reduce CAPEX from 8-10 €/W to less than 2.5 €/W (potentially to 1.8 €/W);
• Increase Load Factor from 25-35% to 32-40% (potentially to 37-45%);
• Reduce mass from 500-5000 tonne/MW to less than 300 tonne/MW (potentially to
220 tonne/MW);
• Reduce LCOE from 300-600 €/MWh to less than 150 €/MWh (pot. to 90 €/MWh);
• MCTF larger than 5107
Collaborations:
• University of Bologna (IT)
• University of Trento (IT)
• University of Edinburgh (UK)
• University of Saarlandes (DE)
• European Marine Energy Center (UK)
• WaVEC Offshore Renewables (PT)
• Tun Abdul Razak Research Center (UK)
• Cheros S.r.l. (IT)
• IVG Colbachini S.p.a. (IT)
• CNET – Energias de Portugal (PT)
• Wave Energy Scotland (UK)
Idea submitted to:
Horizon 2020 Call:
H2020-LC-SC3-2018-2019-2020
Topic: LC-SC3-RES-1-2019-2020