in this greenhouse-like heat-collector whooshes up the chimney, drawing
in cooler air from the perimeter of the heat-collector. Power is extracted
from the air-flow by turbines at the base of the chimney. Solar chimneys
are fairly simple to build, but they don’t deliver a very impressive power
per unit area. A pilot plant in Manzanares, Spain operated for seven years
between 1982 and 1989. The chimney had a height of 195 m and a diameter
of 10 m; the collector had a diameter of 240 m, and its roof had 6000 m2 of
glass and 40 000 m2 of transparent plastic. It generated 44 MWh per year,
which corresponds to a power per unit area of 0.1 W/m2. Theoretically, the
bigger the collector and the taller the chimney, the bigger the power density
of a solar chimney becomes. The engineers behind Manzanares reckon
that, at a site with a solar radiation of 2300 kWh/m2 per year (262 W/m2),
a 1000 m-high tower surrounded by a 7 km-diameter collector could gen-
erate 680 GWh per year, an average power of 78 MW. That’s a power per
unit area of about 1.6 W/m2, which is similar to the power per unit area
of windfarms in Britain, and one tenth of the power per unit area I said
concentrating solar power stations would deliver. It’s claimed that solar
chimneys could generate electricity at a price similar to that of conventional
power stations. I suggest that countries that have enough land and
sunshine to spare should host a big bake-off contest between solar chimneys
and concentrating solar power, to be funded by oil-producing and
oil-consuming countries.

What about getting power from Iceland, where geothermal pow-
er and hydroelectricity are so plentiful?

Indeed, Iceland already effectively exports energy by powering industries
that make energy-intensive products. Iceland produces nearly one
ton of aluminium per citizen per year, for example! So from Iceland’s
point of view, there are great profits to be made. But can Iceland save Europe?
I would be surprised if Iceland’s power production could be scaled
up enough to make sizeable electricity exports even to Britain alone. As a
benchmark, let’s compare with the England–France Interconnector, which
can deliver up to 2 GW across the English Channel. That maximum power
is equivalent to 0.8 kWh per day per person in the UK, roughly 5% of
British average electricity consumption. Iceland’s average geothermal elec-
tricity generation is just 0.3 GW, which is less than 1% of Britain’s average
electricity consumption. Iceland’s average electricity production is 1.1 GW.
So to create a link sending power equal to the capacity of the French inter-
connector, Iceland would have to triple its electricity production. To provide
us with 4 kWh per day per person (roughly what Britain gets from its
own nuclear power stations), Iceland’s electricity production would have
to increase ten-fold. It is probably a good idea to build interconnectors to
Iceland, but don’t expect them to deliver more than a small contribution.

Figure 25.10. The Manzanares prototype solar chimney. Photos from
Figure 25.11. More geothermal power in Iceland. Photo by Rosie Ward.