Green power

Today’s letter from Morag Watson supports the thesis that “there are none so blind as those with an axe to grind”.

Firstly, I fully support every effort to provide carbon-free energy. However, the idea that “electric heat pumps are three times more efficient than their fossil fuel alternatives” is just bonkers engineering.

It is true that, in summer, heat pumps provide three times more heat than the energy used to power them. However, the average seasonal figure is nearer 2.5. Assuming an average winter value of 2, for every 100kwh of heat provided, 50kwh of electricity is required. Coming from the Grid, it is impossible to tell if this is traditional blue electricity or renewable green electricity.

If green electricity cannot meet demand in winter, gas turbine generators will come on line. These have an efficiency of around 50 per cent, meaning that for every 50KWH generated, 100kwh of fossil fuel energy is consumed.

Allowing for Grid losses, this rises to about 110kwh of gas consumed. A condensing gas boiler with an efficiency of 90 per cent can provide the 100kwh of heat required with a consumption of an identical 110kw of gas.

Oh, and don’t forget the huge investment cost difference between the two solutions.

BILL GRAHAM Chartered engineer, Findhorn Road, Forres

Morag Watson of Scottish Renewables writes in praise of her products, but she should remember that some of them – windmills in particular – would not have existed without a subsidy from the consumer in the form of increased electricity prices, regardless of ability to pay.

This unfair form of taxation has made landowners and foreign manufacturers rich while increasing the numbers of those who now cannot afford to heat their homes.

Perhaps that puts some perspective on her enthusiasm.

MALCOLM PARKIN Gamekeepers Road, Kinnesswood, Kinross