The water entering the column compresses the air above it, driving it through turbine propellers which power electrical generators. But as waves crash against the shore, they also recede. As the water flows out of the column sucks air back across the turbine propellers, so the Limpet 500 uses a special Well's turbine which self corrects for changes in the direction of air flow. Fossil fuel costs around 2p per unit, but the electricity generated on Islay is being sold for 5.9p. The difference in price is marked, but prices will fall as the technology is refined.
Electricity companies are about to have their minds sharply focused on renewable energy.
For companies which serve urban areas, this may be difficult. Wavegen believes this may eventually help power a market for small rural communities running their own wave generators and exporting electricity.