What is Wave Energy?
The energy in ocean waves mainly comes in an irregular, oscillating form at all times of the day and night. Solar energy causes winds to blow over vast ocean areas which, in turn, causes waves to form, gather and travel huge distances to the shoreline of continents. The wave height, period and direction are primarily dependent on the wind properties (speed, direction and duration) and also the geometry of the sea (fetch-length and depth). There is surprisingly little loss of energy in deep water ocean waves, so as they travel to distant shores they continue to ‘collect’ more and more wind energy. However, as waves approach relatively shallow water, their energy is greatly dissipated due to ground effects and this causes the dynamic, chaotic and highly variable environment we know as wave-breaking close to shore. The machines used to exploit energy in this shallow or deep water are known as wave energy converters (WECs).
“In order for an oscillating system to be a good wave absorber it must also be a good wave generator” (Falnes, 1978). An offshore SeaPower Platform, deployed in relatively deep water (>50m) is one such device.
Wave Energy Resources
This map shows the wave regimes throughout the globe. The values refer to the annual average available wave power in kW per metre width of wave crest. The areas with the most potential for wave power absorption are those along continental western seaboards with higher concentrations at the higher latitudes. Note the incident power values at Alaska, South America, Ireland, Spain, Portugal, South Africa, Western & Southern Australia and New Zealand. Wave energy devices must be scaled to match the local wave resource (wave height and wave period) but the Seapower Platform is unlikely to be economically viable where the local mean annual resource is less than 40kW/m.
The draft Offshore Renewable Energy Development Plan prepared by the Irish Department of Communications, Energy and Natural Resources quote the following wave energy potential in Irish waters alone:
- 0 – 100m water depth: 12.5GW – 13.6GW
- 100 – 200m water depth: 15.0GW – 17.5GW
- Total: 27.5GW – 31.1GW
Fossil fueled power station:
The Time is Right
Traditional oil & gas production rates are beginning to decline. Energy security for all regions of the globe is now at a critical stage. Hydraulic fracturing “Fracking” of hitherto unreachable oil and gas is proving to be extremely costly to society (monetarily and environmentally). This fact, combined with a collective shift in focus towards the exploitation of sustainable and renewable energy resources has triggered recent interest again in the wave energy sector. The engineering challenges of wave energy production are slowly being overcome. Seapower has learned from the mistakes of earlier device developers who, ill advisedly through investor pressure, put their ideas into the water too soon. Seapower has resolved many of these engineering issues through small scale trials, numerical and physical modeling. We won’t build big unless we are sure as engineers that the time is right. The Seapower Platform, by combining the high performance of its base machine with the right PTO technologies and promising cost benefit outcome, is likely to become a forerunner in this most challenging of renewable energy sectors.