In all these countries, I think the most promising renewable is so-
lar power, concentrating solar power in particular, which uses mirrors or
lenses to focus sunlight. Concentrating solar power stations come in several
flavours, arranging their moving mirrors in various geometries, and
putting various power conversion technologies at the focus – Stirling en-
gines, pressurized water, or molten salt, for example – but they all deliver
fairly similar average powers per unit area, in the ballpark of 15 W/m2.

A technology that adds up

“All the world’s power could be provided by a square 100 km by 100 km
in the Sahara.” Is this true? Concentrating solar power in deserts delivers
an average power per unit land area of roughly 15 W/m2. So, allowing
no space for anything else in such a square, the power delivered would
be 150 GW. This is not the same as current world power consumption.
It’s not even near current world electricity consumption, which is 2000 GW.
World power consumption today is 15 000 GW. So the correct statement
about power from the Sahara is that today’s consumption could be provided
by a 1000 km by 1000 km square in the desert, completely filled with
concentrating solar power. That’s four times the area of the UK. And if we
are interested in living in an equitable world, we should presumably aim
to supply more than today’s consumption. To supply every person in the
world with an average European’s power consumption (125 kWh/d), the
area required would be two 1000 km by 1000 km squares in the desert.

Fortunately, the Sahara is not the only desert, so maybe it’s more rele-
vant to chop the world into smaller regions, and ask what area is needed in
each region’s local desert. So, focusing on Europe, “what area is required
in the North Sahara to supply everyone in Europe and North Africa with an
average European’s power consumption? Taking the population of Europe
and North Africa to be 1 billion, the area required drops to 340 000 km2,
which corresponds to a square 600 km by 600 km. This area is equal to
one Germany, to 1.4 United Kingdoms, or to 16 Waleses.

The UK’s share of this 16-Wales area would be one Wales: a 145 km by
145 km square in the Sahara would provide all the UK’s current primary
energy consumption. These squares are shown in figure 25.5. Notice that
while the yellow square may look “little” compared with Africa, it does
have the same area as Germany.


An organization called DESERTEC [] is promoting a plan
to use concentrating solar power in sunny Mediterranean countries, and
high-voltage direct-current (HVDC) transmission lines (figure 25.7) to deliver
the power to cloudier northern parts. HVDC technology has been in
use since 1954 to transmit power both through overhead lines and through

Figure 25.3. Stirling dish engine. These beautiful concentrators deliver a power per unit land area of 14 W/m2. Photo courtesy of Stirling Energy Systems.
Figure 25.4. Andasol – a “100MW” solar power station under construction in Spain. Excess thermal energy produced during the day will be stored in liquid salt tanks for up to seven hours, allowing a continuous and stable supply of electric power to the grid. The power station is predicted to produce 350 GWh per year (40 MW). The parabolic troughs occupy 400 hectares, so the power per unit land area will be 10 W/m2. Upper photo: ABB. Lower photo: IEA SolarPACES.