Environmental Engineering Reference
In-Depth Information
less dense form of energy than fossil fuels, they generally require a more
extensive production system.
They need more space to grow (in the case of biomass) or to be collected
(wind and solar) than coal, oil or gas, which contain energy in a more
compact, and - crucially, for environmental reasons - underground form.
So wind farms with turbines a hundred metres high, or solar arrays with a
couple of square kilometres of reflectors, will usually take up more space,
and are often more visible, than a coal mine, oil and gas field. Not that coal
slag-heaps, gas flares or oil derricks are exactly invisible, of course.
Moreover, it is not just that some renewables operations are more exten-
sive and obtrusive than the hydrocarbons they might replace. They are
also usually in different places to conventional energy sources, and may
have different logistical requirements. The best wind power is normally
to be found in remote places, requiring the building of new links to the
electricity grid. A good example of this is Scottish wind farms: northern
Scotland produces the best wind in the UK, but southern England is
where most of the UK's consumers are.
New types of infrastructure may have to be used. For instance, a power
plant that uses coal can bring it in on a single-rail track or by barge on
a canal. A plant using biomass, however, will have to have it trucked in
from a far wider catchment area. Rob Church of the American Council
for Renewable Energy (Acore) makes the point that the economic dice are
loaded in favour of hydrocarbons. “If we were starting from zero, it would
be OK. But we have laid an infrastructure for coal already … many of the
problems with renewable energies are because we are having to change
delivery systems as well.”
Intermittency
The other characteristic of wind and solar power is unpredictable inter-
mittency (in contrast to tidal power, which is predictably intermittent). As
a grid operator, you have to take the power when you can get it, and make
other arrangements when it is not.
Wind and solar power is, in the jargon of the electricity industry,
“non-dispatchable”. A grid operator cannot just order up some wind or
solar power, as they might coal or gas, and dispatch it to the grid. Rather,
the operator has to take the wind power when the wind blows and solar
power when the sun shines. And make other arrangements when they're
not available.
