You would be surprised how many people do not appreciate that when a wave energy device works it takes energy form the waves. This reduction in energy is primarly noticed in a reduction in wave height. It can also have a small but measurable impact on wave period.
Offshore devices like "Salters Duck", "The Mighty Whale" all use mechanical hydraulics as the energy transfer mechanism, and are VERY efficient (approx 90% conversion of wave to energy). The downside is that they have to be anchored offshore (not good in a storm) and maintenence is more difficult. Anchoring them way offshore is not an option at present because of the huge transmission losses that would be experienced.
Shore based devices like the Oscillating Water Column operate at much lower efficiency (primarly because the wave energy at the shoreline is only a fraction of that available offshore), but are cheaper to operate. Another downside is that they absorb the wave so there is almost no reflected wave and this can cause issues with sediment transport (ie adjacent beaches might disappear).
In the early 90's in Scotland a company called ART (not related to the windsurfing manufacturer) built an OWC with a wind turbine on top. Unfortunately it sank while being towed to its anchor site. While being funny now it was a travesty to those of us who were working in the wave energy field at the time, and caused large reductions in research funding levels. There is a working OWC in Pt Kembla at the moment (
www.energetech.com.au).
A single device will have minimal impact, a line of wave devices kilometers long will make conditions fantastic for speedsailors.
JB
