capital cost per mw generated, page-6

Despite the euphoria of the last few weeks (or days) expressed here it seems some rational debate on wavepower has commenced on this board. The posters here are a really genuine sensible bunch so that I have been hesitant about contributing warnings. (I have been reading here for the last six months.)

The unit costs of installing plant ($M / MW) discussed by Silkwood and YChromozome is a very useful comparative line to take but I do not want to pursue that at this instant. An even more important issue is the life of the established plant and the risks that might determine such limits. For the various conventional utilities the rates of depreciation are well established: the life of coal crushing mills, boilers, the 30 year 'accounting' life of a hydro power dam, etc. In the number crunching for determination of cost of generation of energy ($ / MWh, not just installing plant) some figure accuracy is required.

What is the life of a CETO generator field? Is it determined by the wear of the pumps attached to each buoy, or the corrosion of the materials in salt water? I suggest it might have more to do with the medium in which it resides and the extreme behaviour that that can experience. In short, it is storms. Land lubbers tend to grossly underestimate the power of a heaving, boiling sea. The energy in a wave is proportional to the square of the wave height. That means a 10m wave has 100 x the energy of a 1m wave. This is very nice if the energy can be controlled and extracted by your device. In a storm the wave energy is your enemy. What wave heights are there in a freak storm, 10 -30m? Note that in storms waves can superpose to be non sinusoidal, and at times may even have vertical sides. How many large waves does it take to smash your entire plant in one night? We are talking of billions of dollars of investment. Your plant has to sit in that sea to extract energy.

Thus for wave power generators the key problem is that the plant has to be designed to withstand the 1000 year storm while it can only deliver at best the average power of the wave field. This makes the plant incredibly expensive. No one seems to discuss such requirements. That is put in the hard basket, or ignored all together.

Perhaps I should mention that over twenty years ago I went on a world study tour on behalf of a key institution to investigate wave power prospects of systems that were being constructed at the time. They were fascinating and ingenious, ranging from Salter's Ducks, to the Norwegian logarithmic wave compressor to lift water to coastal holding ponds (no moving parts), to the surge towers topped by two way air turbines, and others. Hundreds of wave mechanisms have been devised for centuries, mostly of very low efficiency, and of short life. Wave pumps are not new either.

I am not suggesting that no wave power scheme is viable. One must always be open to even more ingenious devices that can take the above issues into account. Carnegie Corp's online cartoon clip of bobbing buoys in neat sinusoidal wave fields looks intoxicatingly beautiful. However, I have not found any serious discussion on the protection of your capital in storms. At best, there are some references to the fact that the buoys are just under water where they cannot be visible.(!)

Hence we may have a significant problem to solve even before considering comparative efficiencies.

Juke