CLIMATE change activists are saying that we should stop using gas to heat our homes – in order to reduce our CO2 emissions. The goal is a good one, but the proposed remedy is absolutely not. If the alternative is to heat using electricity, then switching is exactly the wrong thing to do in current circumstances.
That is because the efficiency of a typical gas boiler is much better than that of conventional fossil-fuelled electricity generation – 80 per cent as against 40 per cent. (We should also factor in the loss in transmission, which for electricity is five per cent and for gas is 0.05 per cent). On those figures, we would have to have 68 per cent of our electricity generated by non-carbon systems (nuclear + renewable), before the CO2 emissions would be equal for heating by gas and by electricity. The 2018 figure for non-carbon generation is 52.9 per cent for the UK. There are some factors that would alter those basic figures: there is quite a lot of gas-turbine/dual cycle generation, where the efficiency can be up to 50 per cent, and modern condensation boilers can give up to 90 per cent. Using those numbers, we would have to have in excess of 80 per cent non-carbon generation. It is clear that it will not, for many years to come, make any climate sense to switch from gas to electricity for heating.
There are of course other low-carbon alternatives for domestic heat: solar PV, heat pumps, wood chip, possibly bio-gas. The first two are particularly expensive (solar for our electrical devices can make sense, but not for heating – for example my electricity consumption is 3000Kwhr. pa. and my heating consumption is 43,000Kwhrs; I would hardly have enough roof area). Also, heat pumps need about 30 per cent electricity. Wood-chip and bio-gas both produce CO2, and while the former is in principle a sustainable system – in that the trees are replaced by replanting, which absorbs CO2 – that is a long-term process while the new trees grow large enough; and we are told we should be trying to be carbon neutral by 2025.
So, at present, the best thing we can do for the climate by way of heating our homes at reasonable installation cost, is to install a condensing gas boiler. (I have absolutely no financial interest in the boiler or gas industries.)
Professor James McKelvie, Glasgow G76.
DR Hamish Maclaren did a service by reminding us that the UK contributes only around one per cner of global carbon dioxide emissions (Letters, October 16). Scotland's contribution is one-tenth of that, that is, 0.1 per cent. Bearing this figure in mind, I would welcome a rational explanation as to why Scotland needs to do more to tackle climate change, which is asserted by environmental lobbyists and politicians on a daily basis. As a lifelong supporter of Scottish independence it gives me no pleasure to know that this is a case where (pace Greta Thunberg) Scotland is too small to make a difference.
Dr Iain Wilkie, Strachur.