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

Thank you! Questions ?

@ Reggio Calabria (IT)