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The Future of Electrical Power Generation

Prof. David J. C. MacKay, Cambridge University, had an interesting column in the New York Times last week here.  He discussed what assumptions can reasonably be made about the availability and use of renewable energy sources.  MacKay discusses the relationships between land area and energy needs of countries around the world.  It is very clear, as he runs through his numbers, that what is sauce for the goose is not, in this case, sauce for the gander.  The results of the analysis are not surprising to anyone who has thought about it.  But it is satisfying to number nerds (like me) to see the analysis carried out with some rigor.

For example, the good professor points out that the solar energy density in Germany's Bavarian solar generation facilities is around 5 watts per square meter of land area, while concentrating solar generation in deserts can produce 20 watts per square meter.  He contrasts this with the energy density of hydroelectric power in Scotland, which he states is 11 watts per square meter of compounded water surface area.  He doesn't give a value, but I expect that the solar energy density in cloudy Scotland is significantly smaller than Bavaria.

Some of the other land use efficiency factors MacKay cites include:  wind - 2.5 watts psm (per square meter) in windy areas; energy crops (in Europe) - 0.5 watts psm; and nuclear plants - 1,000 watts psm.

MacKay also gives some reference numbers for current electricity consumption in various countries.  (I could have said "present" but had to make the pun "current".)  He heads his list with densely populated, high standard of living Bahrain.  The consumption there exceeds 10 watts psm.  He said that many countries exceed 1 watt psm, including Britain, Germany, Japan, the Netherlands, Belgium and South Korea.  Obviously, countries such as these can not expect energy crops to contribute significantly to their electrical energy needs.

The U.S. electrical consumption is 0.3 watt psm.  MacKay identifies some countries near the global average (0.1 watt psm) as Saudi Arabia, South Africa and Mexico.  Obviously, at least in terms of land usage, these countries might consider some use of energy crops, although the usage efficiency per acre is much less than solar and wind.

I am surprised that MacKay is such a landlubber.  He does not consider in his discussion the power generation potential of land based geothermal sources (okay, a landlubber should have mentioned that) and the oceans.  Even if we assign part of that to a parochial perspective from the heart of England, there are oceanographic power generation activities going on in the UK.  There is a SeaGen installation in the tidal currents at Strangford Lough in Northern Ireland (here).  Another project not yet started, the Cardiff-Weston proposal (discussed here), could provide up to 5% of the UKs electrical power needs.  It may be that the UK does not have the geothermal potential of Iceland or the western U.S., but they certainly do have oceanographic potential.  Prof. McKay was remiss in leaving that out of his discussion.

Do not be put off by my sniping criticism.  The topics covered by Prof. MacKay have merit far outweighing the smaller areas he missed.  Read the entire Op Ed 
here.