A recent study published on 13 February in Proceedings of the Royal Society A describes a novel device for generating energy from the sea by converting wave energy into electricity. The new technology is low cost and can overcome some of the drawbacks of conventional wave energy systems.
Wave energy has the potential to offer an incredible source of clean power, however, the performance of wave systems is significantly reduced in rough weather. Previous designs have been also been hindered by the use of complex air turbines and expensive moving parts made of rigid, corrosion-sensitive metal. Moreover, the relatively high cost of constructing wave energy systems in the harsh marine environment as well the challenges associated with developing devices that can withstand the harsh and aggressive sea waves has made wave energy less economically feasible than other renewable energy sources.
Now, researchers from the University of Edinburgh have demonstrated a wave energy technology that can be added to existing ocean systems and potentially scaled up. The novel low-cost structures are made of durable material ― flexible rubber membranes ― with few moving parts and are therefore easier to maintain.
The new system is based on an electrostatic power take-off system, known as a Dielectric Elastomer Generator (DEG), which can directly convert mechanical power into electrical power. The membranes sit on top of a flexible tube ― an oscillating water column ― that fills and empties, and therefore, rises and falls with the motions of the waves. As seawater enters the column, it applies pressure to trapped air within the membrane, causing the membrane to inflate generating a voltage and the deflate, to generate electricity.
The researchers, in collaboration with the Universities of Trento, Bologna, and Scuola Superiore Sant’Anna Pisa in Italy, used a comprehensive modelling approach to first analyse the design and then, build and test an experimental prototype of the system. The findings suggest the device may have the potential to provide electricity to thousands of households ― just one full-size device can generate around 500 kW of electricity, which is enough to heat about 100 homes.
The authors believe their design will replace conventional wave power generators, which are bulky and inefficient, and hope fleets of the devices will one day be used globally to power cities. However, further “fundamental steps” are required before DEGs can become a viable wave energy technology. This includes the development of scalable manufacturing processes and ensuring the materials are capable of withstanding millions of wave cycles. Furthermore, concerns about marine life, the fishing industry and, indeed, the aesthetics of large-scale wave farms still need to be addressed before the technology can become commercially viable, and on a meaningful scale.
As of yet, no renewable energy can produce enough energy to match conventional fossil fuel-burning power plants. More likely, a combined approach will be required. Nonetheless, wave energy has the potential to make a significant contribution.
(1) Moretti, G. et al. Modelling and testing of a wave energy converter based on dielectric elastomer generators. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2019; 475 (2222): 20180566 DOI: 10.1098/rspa.2018.0566