ANDREW H Mackay (Letters, September 5) observes that “without a constant
supply of thermal electricity induced on to the windings of wind, wave and
tidal turbines … not one unit of electricity will be produced”. As a
professional electrical engineer for more than 50 years and counting this
makes no sense. If he is suggesting that electricity can be supplied to the
grid only through thermal sources via steam turbines he is wrong. He seems
to be implying that electrical power to the grid from renewables must be
converted to heat to drive steam turbines in order to achieve electrical
reliability. This is not true and it is a recipe for needless waste. Such a
procedure would be hopelessly inefficient.

The further claim in his letter that “the world will have next to no
electricity” once fossil fuel reserves are depleted is also untrue. Plenty
of studies have been performed in recent years which easily demonstrate
this. The power from the sun, which is intercepted by our planet on a daily
basis is more than enough to meet all of our energy needs (170,000Terawatts
or 5.7 x 1024Joules/year) if collected efficiently through direct solar
methods, through wind farming and through ocean wave exploitation. As has
been detailed in a range of recently published books, and scientific
papers, solar, wind and wave power, reinforced by geothermal, tidal,
biofuel based and clean nuclear, power are well capable of supplying the
energy demands of our modern world economies, simply by using technologies
which are already in existence. What is missing is the political will to
make it happen.

We cannot wait until all the fossil fuel reserves are exhausted, otherwise
climate change will be beyond reversal.

Alan J Sangster,
37 Craigmount Terrace, Edinburgh.

DISAPPOINTMENT is expressed by Andrew H Mackay at the reaction to his
earlier letter (August 28) predicting exhaustion of world coal supplies
within 19 years. He now says that this will result in the collapse of world
electric generation capacity. In contrast, the BP study he criticises
estimates that we have 153 years of coal at present usage levels. So who is
doing the right sums?

The BP study takes the world estimated coal reserves and divides by last
year’s usage. And, sure enough, that comes to 153 years. If coal use goes
up or down this year, the result of the sum will change.Mr Mackay’s
calculation, on the other hand, is based on the presumption that coal use
is increasing and that the increase is not proceeding arithmetically but
logarithmically – that it is soaring away doubling, compounding and
doubling again. This view is illustrated by the old story of putting one
grain of rice on the first square of a chessboard, two on the second, four
on the third, eight on the fourth, and so on. By the time you get to square
64 the quantity of rice needed is staggering. But is that what is really
happening with coal?

This December I can guarantee that I will drink twice as much alcohol as I
will in November. But once Christmas and Hogmanay are past, will I keep
doubling my alcohol intake each month? If I were to, it would be possible
to do a sum to predict whether my liver or my bank balance would give out
first. But that presumes I would not only keep on drinking at December
levels, but will double up every month. The sum might be calculated
correctly, but the premise behind it would be wrong. There has been a huge
increase in world coal use in past years, particularly in Asia. However, it
is not increasing any more. World coal usage fell by six per cent last
year. It has been falling steadily for the last five years. In the last 60
years coal usage in the UK has fallen from more than 240 million tons per
year to 12 million tons. This suggests that Andrew Mackay’s premise is not
correct and hence his predictions of impending crisis are not sound.

That is not to say that there are no challenges regarding electricity
supply in the future. The National Grid predict that there may be as many
as nine million electric vehicles by 2030 and the Government proposes that
all 33 million vehicles in the UK should be replaced by electric from 2040.
Where will the electricity to power them come from? Then there is the
effect of climate change itself. Extreme heat waves will be more frequent
and will increase demand for air conditioning and, correspondingly, deep
winter freezes will be more common. These may be once-in-20-years
experiences at present, but are likely to become once-in-five-years events
in the future. There are plenty of big issues facing us on electricity
security in the future. Running out of coal will probably not be one of the
major concerns.

Russell Vallance,
4 West Douglas Drive, Helensburgh.
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