Electricity Supply: Alternative Currents
28 September 2006
Reading the Current New Scientist (30 September 2006, p24) I see an
interesting article by George Monbiot, ‘Low Wattage Thinking’. He makes
some valuable observations about local micro generation of electricity.
We might have come to believe that wind powered electricity generators
and photovoltaic arrays on our roofs had to be a good idea though they
are still more expensive than mains electricity. I still think they have
their uses. George Monbiot quotes from ‘Building for a Future’ magazine
figures showing that for instance in a higher than average wind speed
of 4m/sec a 1.75m turbine produces about 5% of an average household’s
annual electricity consumption. To produce 50% 4m diameter is required
which GB comments, ‘would rip the side off your house’!
Photovoltaic tile installations are slated on other grounds, mainly
expense. He points out, quoting the International Energy Agency’s MARKAL
model, that the estimated cost of saving carbon emission by generating
electricity from sunlight by the year 2020 ranges between £2200 and
£3300 per tonne. In comparison the carbon saving cost of onshore macro wind
power ranges between £40 and £130 per tonne.
The conclusion seems clear that large wind power installations are the
better investment. What seems often not to be taken into account is
reliability of public supply. It is possible that concern about this might
seem, when everything is going well, warm September days and so on,
unnecessarily pessimistic. But a modest degree of preparedness, like some
of us still keeping a few candles and matches for unexpected blackouts,
might include provision for generating say a tenth of domestic
requirements from independent alternatives. A small turbine and perhaps one
square metre of photovoltaic cells could, perhaps in conjunction with
battery storage and a converter, supply enough to run a computer, a few
fluorescent lights, charge the mobile phone, and even run the central
heating. This might seem more ‘survivalist’ than ‘Earth friendly’ but good
management of resources helps both.
Another article in the same New Scientist (‘One degree and we’re done
for’, Fred Pearce, p 8/9) explains in convincing detail the positive
feedback loop of warming of the sub-arctic arboreal forests of the
northern hemisphere causing the release of carbon dioxide and methane as the
permafrost melts and forest fires consume dead trees killed by moth
infestations. The author, Fred Pearce, quotes Jim Hansen, director of
NASA’s Goddard Institute for Space Studies in New York and his team saying,
‘Another decade of business-as-usual carbon emissions will probably
make it too late to prevent the eco-systems of the north from triggering
runaway climate change’.
(Proceedings of the National Academy of
Sciences, vol 103, p 14288)
