Figures do not add up for sea power

Jenny Fyall writes that the £4 billion to be invested in wave and tidal schemes in Scottish waters will deliver 1,200 MW of electrical power (your report, 19 May). However, the power output of the scheme is to be split almost equally between wave (capacity factor of 25 per cent) and tidal (capacity factor of 40 per cent) so the average power delivered will be in the order of 400 MW.

If the same 4bn was invested in a 1,650 MW EPR nuclear plant (capacity factor of 90 per cent) the average power delivered would be in the order of 1,480 MW, more than three times greater than the renewables scheme, without the need for back-up.

Moreover, a modern nuclear plant has a design life of 60 years compared with 20 years for marine renewables, so more than 10 times as much energy would be delivered.

In addition, it is proposed that wave schemes are supported by five Renewable Obligation Certificates (ROCs) for every MW-hour of energy produced, while tidal will attract three ROCs.

Each ROC provides 37 per MW-hour to generators (on top of the sale of electricity), so the 4bn scheme will attract renewable obligation costs in the order of 480 million a year. An industrial scale demonstration of wave and tidal power is an exciting development and is to be welcomed. It will allow innovation in engineering design to flourish and will provide real experience of operating costs. However, let's not delude ourselves that we are on the verge of a low-cost energy bonanza.

COLIN R McINNES

Williamwood Park West

Glasgow

Reading about the "600ft 'sea snake' to harness power of Scotland" (your report, 19 May), in which it was reported that Alex Salmond unveiled the plaque at the launch of the Pelamis Vagr Atferd wave electricity generator, I noted that it cost some 4.8m to build a 1,500 tonne, 600 foot-long unit with the claimed capacity to generate 750 KW. I wonder if our politicians pondered the scale-up issues with such a facility. In order to construct a commercial size generator of, say, 400 MW, it would require a 20 mile-long construction weighing around 800,000 tonnes costing more than 2bn.

Can this really be pragmatic or even capable of recovering the energy that would be expended on steel manufacture and associated fabrication?

Somehow I doubt there would be a huge worldwide market for such a device.

GM LINDSAY

Whinfield Gardens

Kinross