I NOTE with interest your article which quoted Lang Banks of the WWF praising renewable electricity generation in Scotland from wind and solar sources, using statistics that they produced power in October "equivalent" to the requirement of more than three million homes, while ignoring all the other demands on power ("Country could be powered by wind, says WWF", The Herald, November 4).

Accepting that his statistics are correct I must draw readers' attention to the devil in the detail.

Please note that "equivalent" does not in this case mean "equal to". Equivalent yes, implying that the units of power generated exceed the units of power consumed in the homes.

The problem is that the wind blows unpredictably, often during the night when we are all tucked up, using only power to drive the freezer and the fridge. Similarly, solar only really zings on sunny summer afternoons, again when home use requirements are low. All the while the generating companies are trying to balance supply and demand using hydro, fossil fuel and nuclear as base load. Hydro is great because it can store renewable power, but the supply is limited. Fossil and nuclear only work efficiently when demand is constant or at least predictable. So much of the renewable power is of little real use.

Wind power is already at a satura­tion point where the system has difficulty coping with the variability, yet we continue to throw vast subsidies at entrepreneurs to create more. At least the subsidies promote industrial-scale generation as opposed to tiny windmills in back gardens. But with solar we do the opposite; we give subsidies to put it on our house roof, economic nonsense when the capital cost is balanced against output. Instead we should encourage industrial-scale exploitation, but as far south as possible to get higher efficiency. We should focus the renewable subsidies on commercial hydro developers, recognising that we have already captured the best geography and there must be a point of diminishing returns.

So that leaves the big beasts. Fossil must go, for the joint reasons of global warming and diminishing fuel supply, nuclear is the best of what is left, yet our supposedly green Scottish Government has its head fully immersed in a bucket of sand.

Richard Heuchan,

15 Tower Drive,

Gourock.