From Adam Quantrill
In your news section you say that choppy seas take the edge off global
warming by reflecting sunlight back into space
(14 April, p 12), but in your
letters page a reader is advocating covering deserts with photovoltaic cells to
generate hydrogen via electrolysis (p 52).
Silicon solar cells are not very efficient. Only 20 per cent of incident
radiation is converted to electricity, a small amount being reflected back into
space and the rest being absorbed and turned into heat. If you compare the
reflectivity of pristine desert with one covered with solar cells, you may well
end up with a net warming effect, even after factoring in the savings in carbon
dioxide emissions from hydrogen fuel use. This is all the more ironic given that
the silicon in solar cells comes from desert sand. A better approach may be to
forget the solar cells and paint the desert white.
Cambridge
