Carolyn Churchill's article (April 25) on power generation had figures only from the nuclear industry. Considerably less favourable independent calculations suggest nuclear's CO2 emissions are comparable to emissions from gas turbines. CO2 savings, if any, will be late on in the lifecycle of a station - not soon, when we need them. It is unhelpful to repeat the intermittent supply argument against renewables, given that Hunterston B has spent six months out of commission for repairs and yet not a day has gone by when Scotland has had no wind, waves, tide or sunlight.

The political debate over whether to build more commercial nuclear power stations is more complex than a matter of CO2 emissions. We must take account of the international political equation where, for reasons of global safety, we need to take a principled stand against proliferation of potentially dual-use nuclear technologies. In committing to nuclear technology, we defer our energy crisis to the next generation when high-quality uranium ore (sourced from foreign shores) becomes the depleting resource over which the world fights.

Helpfully, the article cites one key statistic which should focus the minds of readers: the estimated 50% increase in electricity demands by 2050. This is not a given, merely a prediction that we can choose to influence politically. We may choose to bury our heads in the sand about our energy profligacy, provide a poor example globally and take out a further expensive nuclear loan whose repayments generations will rue. Or we can use existing nuclear power until the licences run out and forge ahead setting an example both with renewables and with efficiency. We can build a high-quality, low-energy, sustainable society which current and future generations will thank us for.

Dr Martin Bartos, Scottish Green Party candidate, Glasgow Kelvin, 185 Byres Road, Glasgow.

It may surprise Kerr MacGregor (Letters, April 16) that I, too, am an engineer well-versed in pragmatism and independent of the renewables industry. Like the politicians he praises, he appears to be basing his 100% renewables electricity generation claim on a far from proven and somewhat dubious basis. Perhaps he could be more specific on some of his claims, namely: 1. If, as he asserts, Norway "now gets 100% of its electricity from hydro", why is it building a large nuclear power station?

2. Can he elaborate on his statement that Denmark has "reached 20%" when he talks about wind energy? Denmark does not meet anything like 20% of its annual electricity demand from wind. He is surely aware that Denmark essentially gives away much of its wind-generated electricity to Sweden and Germany as its intermittency results in electricity being generated when not required and vice versa.

3. Does his assertion that "30% could come from on-shore and off-shore wind" take into account consequential grid instability? Ireland and Germany have experienced grid problems at much lower percentages of wind.

4. How can he predict that "at least another 30%" can come from "wet" renewables "such as wave and tidal" when the technology for these is far from proven?

If Mr MacGregor is typical of engineers advising political parties, it's time to buy a home generator.

Dr GM Lindsay, Whinfield Gardens, Kinross.