Wave energy advocates argue that consistency is an advantage in the mix of renewable energy technologies, particularly in a future low-emission society.

New research by Griffith University reveals seasonal and inter-annual variations in wave energy generation are considerable and should be factored into wave energy feasibility assessments.

Scientists from Griffith’s School of Engineering and Built Environmentand Griffith Centre for Coastal Management based on 31 years of high-resolution simulated historical wave data, examined the temporal variability in the wave energy resource off the Australia’s southeastern shelf and in the conversion of wave power into electricity at three promising sites along the NSW central coast using a range of wave conversion devices.

It has been estimated ocean wave energy alone could contribute up to 10% of Australian renewable energy needs by 2050.

There are a few wave energy farm projects planned for Australia along the coasts of Victoria and Western Australia (Albany, Carnegie Clean Energy Ltd) – that are financially supported by State Government Schemes, using wave energy technology comparable in maturity with international wave conversion devices.

Griffith’s research team – including Dr Nick Cartwright, Dr Darrell Strauss, Amir Etemad-Shahidi, and PhD candidate Joao Morim – combined the simulated wave data from the coasts of Newcastle, Sydney, and Seal Rocks, with conversion efficiency data obtained from 10 ‘pre-commercial’ wave energy devices (national and international), examining the variability of wave energy production and performance from between months and from year-to-year.

According to the researchers, temporal variations of wave power production can be highly significant and should be accounted for. The researchers said that recent assessments of the economic viability of wave energy farm projects failed to consider these variations and were instead based on annual and/or seasonal averaged assessments.

Morim said such assumptions could be misleading in terms of anticipating the revenue of wave energy farm projects. He said the findings instead support the long-proposed viability of wave energy farm projects.

“We have shown that inter- and intra-annual variations of monthly wave energy production can reach ~30 to 70% depending on the device and site, showing thateconomicalfeasibility studies based on stationary annual/seasonal-averaged analysis are misleading,” Morim said.

“Our preliminary analysis finds that smaller-scale wave energy devicesoptimisedto local sea states can not only potentially lead to a much higher wave conversion performance, but also lead to reduced electrical production variations between months (~30 to 80%) and between years (~11 to 80%) – which plays a key role in the cost-efficiency of wave farm projects.”

“These results show that using wave technology specifically developed for certain sea-states characteristic of a region is key to significantly enhance energy conversionperformance, anddecrease variations in electricity supply – which represents a promising finding for the future of wave energy exploitation and support future estimations of economic viability of wave energy farm projects within Australia and other countries.”

These findings are particularly valuable since wave energy is largely uncorrelated with wind power and has only a third of the natural variability exhibited by wind energy. Furthermore, waves can be forecast three times further ahead than wind.

The paper ‘Inter- and intra-annual variability of potential power production from wave energy converters’ is published inEnergy.