Ocean-based wave energy is tricky to harvest. The energy is there, and is fairly constant, but the hardware necessary to harvest large quantities of it has so far proven to be unequal to the task in economic terms. This is partly due to the fact that the energy is diffuse – there’s a lot out there, but it’s spread out over a large area of ocean surface. But the problems the industry’s faced have also got a lot to do with how badly electricity and sea water mix: wave-power generators need to be well sealed and insulated in order to function in the ocean, which really ups the capital cost.
Now, what if you moved where the power was generated, so that you didn’t have to worry about seawater leaking in and frying your generator? That’s what a company’s trying to do in England, by using wave energy to pump water into a reservoir on land, which can then function as a gravity-powered hydroelectric plant. Think of it as a miniature Hoover dam near the shore: pumps in the ocean use wave energy to pump water up into it, and as the water flows back down to the ocean it generates power.
The big question is, how much will it end up costing per MW? They’ve got some promising estimates, but we’ll have to wait and see if it actually lives up to their promises.