EPoSil: electroactive polymers for generating electricity from wave power
30 July 2013
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| The EPoSil concept uses dielectric elastomer transducers to generate electrical energy from wave motion. Source: Bosch. Click to enlarge. |
A German consortium involving four companies and and two universities is developing dielectric elastomers (electroactive polymers) for the conversion of mechanical energy—in this case wave power—into electrical power.
The German Federal Ministry of Education and Research is supporting the project known as EPoSil (electroactive polymers based on silicon for power generation) until January 2015 with funding of nearly €2 million (US$2.7 million). This grant is part of the “smart materials for innovative products” program.
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| Global potential for wave power. Fugro Oceanor has drawn up a map illustrating the likely potential for wave power along the world’s coasts. The figures are 10-year average values; values can fluctuate sharply within any one year. The company used data from the European Centre for Medium-Range Weather Forecasts (ECMWF). Click to enlarge. |
Waves are a huge potential source of energy—29,500 terawatt-hours a year, according to calculations by the United Nations. By comparison, the International Energy Agency reports that some 21,500 terawatt-hours of electrical power were generated worldwide in 2010. EPoSil hopes to unlock this reserve of renewable energy.
A number of expert partners have come together to exploit wave energy: Wacker Chemie AG supplies a silicon-based material. This is an essential part of the electroactive polymer that converts mechanical energy into electrical power. The project is coordinated by Bosch, together with its subcontractor Compliant Transducer Systems.
The Technical University of Darmstadt is developing a method for testing the electroactive polymers. A scale model is to be tried out in the wave canal of the Technical University of Hamburg-Harburg. The systems for testing the generator units are being developed by Ingenieurbüro Brinkmeyer & Partner in Winnenden, near Stuttgart. Bosch Rexroth is supporting the consortium by constructing the models.
The energy converter is basically a three-ply sheet. The top and bottom layers are conductive to electricity—i.e. they are electrodes. The middle layer is made of extremely elastic silicon, which has pronounced isolating properties. Even under industrial conditions, this can be manufactured at a constant thickness.
The movement of the waves exerts a mechanical force on the converter (sheet). Initially, the upward movement of the wave compresses the silicon. As a result of this compression of the middle layer, the distance between the two electrodes is reduced. A tiny electrical current is applied from an external source, positively charging one of the electrodes, and negatively charging the other.
As the wave begins to fall, the force acting on the converter decreases. The silicon relaxes and returns to its original thickness. The distance between the negatively and positively charged electrodes increases. This effect leads to an increase in electrical power in the converter. The result is that the mechanical energy of the wave has been converted into electrical power. This power is harvested, and the cycle begins again.
There are several ways in which the three-ply sheets can be compressed by ocean waves. Imagine a buoy made up of two parts. The upper half floats on the ocean surface, the bottom half is firmly anchored to the ocean floor. The two halves are connected to each other by a stack made up of thousands of sheets. Every 3 to 10 seconds, these sheets are deformed by the movement of the waves.
The electrical current from one individual layer is minimal, but when it is multiplied by a thousand or more, it soon adds up.
—Dr. Istvan Denes, Bosch corporate research and advance engineering
The first true-to-scale model of a wave-power generator is slated to be launched in the wave channel of the Technical University of Hamburg-Harburg in 2014. Looking further ahead, the plan is to have commercial wave-power generators compressing and relaxing again tens of millions of times. The target efficiency for converting mechanical energy into electrical power is 50%.
'Waves are a huge potential source of energy—29,500 terawatt-hours a year, according to calculations by the United Nations. By comparison, the International Energy Agency reports that some 21,500 terawatt-hours of electrical power were generated worldwide in 2010. EPoSil hopes to unlock this reserve of renewable energy.'
This is total theoretical energy regardless of costs, and assuming that none is 'wasted' on the natural ecology of tidal action:
'The total theoretical wave energy potential is estimated to be 32,000 TWh/yr (115 EJ/yr) (Mørk et al., 2010), roughly twice the global electricity supply in 2008 (16,800 TWh/yr or 54 EJ/yr). This fi gure is unconstrained
by geography, technical or economic considerations. The regional dis-tribution of the annual wave energy incident on the coasts of countries or regions has been obtained for areas where theoretical wave power P≥ 5 kW/m and latitude ≤66.5º (Table 6.1). The theoretical wave energy
potential listed in Table 6.1 (29,500 TWh/yr or 106 EJ/yr) represents a decrease of 8% from the total theoretical wave energy potential above (it excludes areas with less than 5 kW/m), but should still be consid-
ered an estimate of theoretical potential. The technical potential of wave energy will be substantially below this fi gure and will depend upon technical developments in wave energy devices. Sims et al. (2007) esti-mate a global technical potential of 500 GW for wave energy, assuming that offshore wave energy devices have an effi ciency of 40% and are only installed near coastlines with wave climates of >30 kW/m, whereas Krewitt et al. (2009) report a wave energy potential of 20 EJ/yr'
http://srren.ipcc-wg3.de/report/IPCC_SRREN_Ch06.pdf
So the realistic energy which could be got from this is a small fraction of world demand, and even then would likely have severe effects on the local ecology.
This is a subsidy ploy, which is wrongly represented as a major energy contributor, and which will remain fundamentally irrelevant to our energy future.
Posted by: Davemart | 30 July 2013 at 02:43 AM
@Davemart
The fraction ow world energy demand that wave power could meet is not the point. Wave power won't be coming to inner Mongolia or Kansas anytime soon but locally wave could be a viable addition to the renewables palette. See also http://www.withouthotair.com/c12/page_73.shtml. Not surprisingly, the UK is pushing to be a leader in getting wave technology developed and deployed - http://www.emec.org.uk/facilities/wave-test-site
As for affecting the 'natural ecology', increased wind speed associated with climate change will do that anyway. Negating some of the resulting increase in coastal wave energy would surely be a benefit.
No idea where the 'tidal action' comment fits into wave energy.
Posted by: Thomas Lankester | 30 July 2013 at 06:05 AM
Just as we see with offshore windmills, the impact on local marine ecology may be spectacularly positive.
These devices are almost immobile. the pillar is firmly built to the bottom of the sea, and the buoy only modestly goes up & down.
Just as for windmills, the presence of these "buildings" at the seabed protects the local ecology against fishing boats (who do far more damage to the marine ecosystem than all other human activities combined) and a lot of sea creatures live on the outer layer of the structures.
Posted by: Alain | 30 July 2013 at 06:42 AM
The Shetland Viking windfarm has planning permission for 370MW of turbines with an expected ~50% capacity due to the good wind conditions there. The crude potential is for 150km x 60kW/m = 9000MW so is significant. Not enough to power the whole world but it doesn't have to be to prove useful.
My hunch though would be that the practical potential would be less than 370MW, would provide less ecological concerns than the turbines and be much more expensive. I can't see it succeeding in its current form. Would it be useful for navigation buoys?
The novelty is the mechanical to electrical conversion - so how does it compare to a standard generator? I'm cynical when no mention is made.
Posted by: DavidJ | 30 July 2013 at 08:58 AM
Apologies for the slip referring to wave power as tidal.
This minor resource is going to absorb vast amounts of cash, when a fraction of the same expenditure could much improve current nuclear reactors, which really can do the job of powering a low carbon energy rich future.
This is yet another ploy by anti nuclear people to pretend that there are real alternatives, when not even solar, by far the pick of them, can do the job of powering a highly populated advanced industrial economy.
Another ecologically disastrous fake alternative, designed to transfer subsidy to the pockets of the connected.
Posted by: Davemart | 30 July 2013 at 09:11 AM
@Davemart: I'm not so sure about 'ecologically disastrous' but I agree this is a distraction from the pursuit of real solutions, such as next-gen nuclear.
Posted by: Nick Lyons | 30 July 2013 at 12:28 PM
Energy production diversity is very positive and harnessing wave energy could be an important source in coastal areas.
Solar may be more advantageous in Southern USA and similar areas.
Current nuclear technology may not survive due to very high overhaul and used fuel disposal cost and perceived safety issues.
Converting industrial, forestry, agriculture residues and domestic wastes into energy will become another important energy source.
Posted by: HarveyD | 30 July 2013 at 04:01 PM
If this stuff works then as we build sea walls around our coastal cities to deal with rising water we can cover their ocean-facing sides with electricity generation.
Yeah, we might have to use coffer dams to let us get the restraining walls into the water, but....
Posted by: Bob Wallace | 31 July 2013 at 02:09 PM