Fantasy time: solar farming

If a breakthrough of solar technology occurs and the cost of photovoltaics
came down enough that we could deploy panels all over the countryside,
what is the maximum conceivable production? Well, if we covered 5% of
the UK with 10%-efficient panels, we’d have

10% × 100 W/m2 × 200 m2 per person
50 kWh/day/person.

I assumed only 10%-efficient panels, by the way, because I imagine that
solar panels would be mass-produced on such a scale only if they were
very cheap, and it’s the lower-efficiency panels that will get cheap first.
The power density (the power per unit area) of such a solar farm would be

10% × 100 W/m2 = 10 W/m2.

This power density is twice that of the Bavaria Solarpark (figure 6.7).

Could this flood of solar panels co-exist with the army of windmills we
imagined in Chapter 4? Yes, no problem: windmills cast little shadow, and
ground-level solar panels have negligible effect on the wind. How auda-
cious is this plan? The solar power capacity required to deliver this 50 kWh
per day per person in the UK is more than 100 times all the photovoltaics
in the whole world. So should I include the PV farm in my sustainable
production stack? I’m in two minds. At the start of this book I said I
wanted to explore what the laws of physics say about the limits of sus-
tainable energy, assuming money is no object. On those grounds, I should
certainly go ahead, industrialize the countryside, and push the PV farm
onto the stack. At the same time, I want to help people figure out what
we should be doing between now and 2050. And today, electricity from
solar farms would be four times as expensive as the market rate. So I feel
a bit irresponsible as I include this estimate in the sustainable production
stack in figure 6.9 – paving 5% of the UK with solar panels seems beyond
the bounds of plausibility in so many ways. If we seriously contemplated
doing such a thing, it would quite probably be better to put the panels in
a two-fold sunnier country and send some of the energy home by power
lines. We’ll return to this idea in Chapter 25.


Manufacturing a solar panel consumes more energy than it
will ever de-liver.

False. The energy yield ratio (the ratio of energy delivered by a system
over its lifetime, to the energy required to make it) of a roof-mounted,
grid-connected solar system in Central Northern Europe is 4, for a system
with a lifetime of 20 years (Richards and Watt, 2007); and more than 7 in

Figure 6.7. A solar photovoltaic farm: the 6.3 MW (peak) Solarpark in Mühlhausen, Bavaria. Its average power per unit land area is expected to be about 5 W/m2. Photo by SunPower.
Figure 6.8. Land areas per person in Britain.