House of Lords Tuesday 13th January 2009 The public discussion of energy options tends to be intensely
emotional, polarized, mistrustful, and destructive. Every option is
strongly opposed: the public seem to be anti-wind, anti-coal,
anti-waste-to-energy, anti-tidal-barrage, anti-fuel-duty, and
We can't be anti-everything! We need an energy plan that adds up.
But there's a lack of numeracy in the public discussion of energy.
Where people do use numbers, they select them to sound big, to make an
impression, and to score points in arguments, rather than to aid
My motivation in writing "Sustainable Energy - without the hot air"
(available both on paper, and for free in electronic form
[withouthotair.com]) is to promote constructive conversations about
energy, instead of the perpetual Punch and Judy show. I've tried to
write an honest, educational and fun book. I hope the book will help
build a cross-party consensus in favour of urgently making an energy
plan that adds up.
"Sustainable Energy - without the hot air" presents
the numbers that are needed to answer these questions:
How huge are Britain's renewable resources, compared with our current
How big do renewable energy facilities have to be, to make a
How big would our energy consumption be if we adopted strong
Which efficiency measures offer big savings, and which offer only 5
Do new much-hyped technologies such as hydrogen or electric cars
reduce energy consumption, or do they actually make our energy
Wherever possible, I answer these questions from first principles. To
make the numbers comparable and comprehensible, I express all energies
and powers in a single set of units: energies are measured in
kilowatt-hours (the same units that you see on your electricity bills
and gas bills, costing 10p a pop), and powers are measured in
kilowatt-hours per day, per person. Everyday choices involve small
numbers of kWh per day. If I have a hot bath, I use 5 kWh of
energy. If I were to drive from Cambridge to London and back in an
average car, I would use 130 kWh.
Let me give you three examples of what we learn when we work out
the numbers. First, switching off the phone charger.
I think I first heard this idea from the BBC, the idea that one of the
top ten things you should do to make a difference to your energy
consumption is to switch off the phone charger when you are not using
it. The truth is that leaving the phone charger switched on uses
about 0.01 kWh per day. This means that switching the phone charger
off for a whole day saves the same energy as is used in driving an
average car for one second. Switching off phone chargers is like
bailing the Titanic with a teaspoon.
Second, hydrogen for transport:
all hydrogen-powered transport prototypes _increase_ energy consumption
compared to ordinary fossil-cars; whereas electric vehicles are
significantly more energy efficient than fossil-cars. So hydrogen vehicles
make our energy problem worse, and electric vehicles make it better.
Third, here are the numbers for wave power. We often hear that
Britain has a "huge" wave resource. But how
huge is the technical potential of wave power compared with our huge
consumption? If 1000 km of Atlantic coastline were completely filled
with Pelamis wave machines, the average power delivered would be 2.4
kWh per day per person. That is indeed a huge amount of power: but today's
British total energy consumption is on average 125 kWh per day per
person. (That's for all forms of energy: electrical, transport,
heating - not just electricity.)
So a country-sized wave farm would deliver an average power equal to
2% of our current power consumption. I'm not saying we should not
invest in wave power. But we need to know the truth about the scale of
This message applies, sadly, to almost all renewables in Britain
(wind, tide, photovoltaics, hydroelectricity, biofuels, for example): to
make a substantial contribution, renewable facilities have to be
And this is perhaps the most important message: the scale of action
required to put in place a sustainable energy solution. Even if we
imagine strong efficiency measures and smart technology-switches that
halved our energy consumption [from 125 kWh per day per person to 60
kWh per day] (which would be lower than the per-capita consumption of any
developed country today), we should not kid ourselves about the
challenge of supplying 60 kWh per day without fossil fuels. Among the
low-carbon energy supply options, the three with the biggest potential
are wind power, nuclear power, and concentrating solar power in other
peoples' deserts. And here is the scale that is required if (for
simplicity) we wanted to get one third from each of these sources: we
would have to build wind farms with an area equal to the area of
Wales; we would have to build 50 Sizewells of nuclear power; and we
would need solar power stations in deserts covering an area twice the
size of Greater London.
Of course I'm not recommending this particular mix of options; there
are many mixes that add up; and a more detailed story would discuss
other technologies such as 'clean coal' with carbon capture and
storage (as yet, unproven); and energy storage systems to cope with
fluctuations of supply and demand.
Whatever mix you choose, if it adds up, we have a very large building task.
The simple wind/nuclear/solar mix I just mentioned would involve
roughly a hundred-fold increase in wind power over 2006 , and a
five-fold increase in nuclear power ; the solar power in deserts
would require new long-distance cables connecting the Sahara to
Surrey, with a capacity 25 times greater than the existing
It's not going to be easy to make a energy plan that adds up; but it is
possible. We need to get building.
1. David MacKay is Professor of Natural Philosophy in the Department of
Physics at the University of Cambridge. "Sustainable Energy -
without the hot air" (382 pages, full colour) is published by UIT
2. Of course, I'm not the first to present these numbers. All these facts
have been laid out, for example, by the Royal Commission on
Environmental Pollution in its 22nd report, "Energy - The Changing
Climate" (2000), and by the Committee on Climate Change in its report
"Building a low-carbon economy" (December 2008).
3. In 2006, all wind farms in Britain delivered an average power of
0.2 kWh per day per person.
4. In the year ending March 2008, Sizewell delivered
9.8 TWh per year, which is roughly 0.4 kWh per day per person.
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David J.C. MacKay email@example.com
Cavendish Laboratory, 19 J J Thomson Ave, Cambridge CB3 0HE. U.K.
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