The waves are an almost inexhaustible source of power, with no period where their energy cannot be tapped.

Moon-power presents a great opportunity for renewables, so why is it not being further developed. Tidal power resources have been estimated at 120-400GW in various studies, but less than 1GW has been built. The short answer is money. The capital expense is as high as other non-carbon energy sources, but the efficiency far lower.

For a start, the power that can be harnessed by a turbine is a cube function of fluid velocity, so for half of the time, at high and low tide, there is not enough water moving past the turbines to generate any power. The tides are also strongest when the moon and sun align and their gravitational fields reinforce one another. But they half this at half moon, twice per month.

The result of this is that only 24 per cent of the total capacity is being achieved by tidal projects.

AS Thunder Said Energy note, that capacity factor ‘hurts’ when capex costs are $2,500-25,000/kW. Compared to this offshore wind might cost $4,000/kW but achieves a 40-45 per cent capacity factor. Nuclear plants can cost more, at $7,000/kW, but can achieve 98 per cent capacity factor. Solar is less efficient even than tidal, but it is cheap, and at less than $1,000/kW, its 15 per cent capacity factor still makes it a contender.

And so there it is. Current ability to harness the waves is too expensive per KW produced. Time, tide and capex wait for no man.

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