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a little adds up to a lot,” if all those “littles” are somehow focused into a single “lot” – for example, if one million people donate £10 to one accident- victim, then the victim receives £10 million. That’s a lot. But power is a very different thing. We all use power. So to achieve a “big difference” in total power consumption, you need almost everyone to make a “big” difference to their own power consumption.

by reducing our population

A final impediment to rational discussion of combined heat and power is a myth that has grown up recently, that decentralizing a technology somehow makes it greener. So whereas big centralized fossil fuel power stations are “bad,” flocks of local micro-power stations are imbued with goodness. But if decentralization is actually a good idea then “small is beautiful” should be evident in the numbers. Decentralization should be able to stand on its own two feet. And what the numbers actually show is that centralized electricity generation has many benefits in both economic and energy terms. Only in large buildings is there any benefit to local generation, and usually that benefit is only about 10% or 20%.

Power consumption per capita, versus GDP per capita,

Figure 30.1 (p231)

The only notable ex- ception to the rule “big GDP implies big power consumption” is Hong Kong.

We use about as much to heat and cool ourselves (in Britain) as we use to move around in our cars, while lighting uses onlu a graction of that energy - especially using low energy fluorescent bulbs or the new generation of LED lights. Hydro-electric power in Britain, however, even with generosity from the wet Highlands, will only deliver about one third of the small amount of energy we use to light ourselves. How unfortunate that such accidental power-concentrators as mountains and streams are not more plentiful, and not just, maybe, for the energy benefits.

The average winter-time temperature in English homes in 1970 was 13C. Today, 50% more than that is usually thought of as just about tolerable. There are three strategies for reducing the carbon footprint of keeping warm: reduce the temperature difference between the inside and outside; reduce heat losses from inside to outside and increase the efficiency with which energy is transformed into heat. The first two seem obvious and cheap solutions. We hear a lot about "nudging" as a policy, and this seems an ideal area for clever devices to make people aware that they could be heating less and leaking less heat. David does not mention my own favourite long term solution here---a widespread move to small exoskeletons as a substitute to housing: we should be able to walk around with our temperature control close to our bodies and our living spaces open to the elements. David makes a powerful argument for heat pumps rather than Combined-Heat-and-Power plants, and slips in a big fault-line in eco-politics versus eco-engineering: energy transformation efficiency tends to rise as scale rises, whereas green politics loves to decentralise and make solutions small and local. This chapter is full of low-ish tech, labor-intensive investments that make energy-efficiency sense today. This is just what government policy should be stimulating our economies with today.

Electrify transport. There's not much to beat trains+bicycles, and any government looking for a Keynesian stimulus should find lots of infrastructure opportunities here. David MacKay comes down softly on the car---which shows great realism---and finds that electrification is the only real solution there. He debunks hydrogen as a good energy carrier. Flying is a really tough case---there is not much that can be done to reduce its energy intensity. (I was sitting in an easyjet plane the other day that tried to convince me of its greenery by saying: "Flying contributes less CO2 than driving to the atmosphere" ...). Batteries are the way to go---though just wait for the peak lithium scares. David has an interesting aside on nuclear ships. If we could make the (political) world safe for small-scale nuclear power, maybe there's more than ships that could benefit.

Second, to supplement solar-thermal heating, we electrify most heating of air and water in buildings using heat pumps, which are four times more efficient than ordinary electrical heaters. This electrification of heating further increases the amount of green electricity required. Third, we get all the green electricity from a mix of four sources: from our own renewables; perhaps from “clean coal;” perhaps from nuclear; and finally, and with great politeness, from other countries’ renewables. Among other countries’ renewables, solar power in deserts is the most plentiful option. As long as we can build peaceful international collabor- ations, solar power in other people’s deserts certainly has the technical potential to provide us, them, and everyone with 125 kWh per day per person.

The lion's share of the money is thus cleaning up military mess, not civilian-power mess.

Many gadgets consume a surprising amount of power on standby. David cut his electricity consumption by half by making sure his "vampire appliances" were kept off. There are real savings available here. David and friends set up "ReadYourMeter.org" to try to encourage others to make this sort of saving. According to the International Energy Agency, standby power consumes a surprising8% of residential electricity.

As for a 500 ml water bottle made of PET (which weighs 25 g), the embodied energy is 0.7 kWh – just as bad as an aluminium can!

Computers Making a personal computer costs 1800 kWh of energy. So if you buy a new computer every two years, that corresponds to a power consumption of 2.5 kWh per day.

In which we learn that to get by on wave power you need to be very very insular -- that is, have a small number of people per unit length of exposed coastline (sounds like a nice place to me, but the British Isles don't fit the description) -- and also that our food habits, especially for red-blooded carnivores with meat-eating pets -- amount to more than half our driving habit in energy. There is a real energy case to be made for vegetarianism (approximately twice as efficient) and even more for veganism (another doubling).

Eating meat requires extra power because we have to feed the queue of animals lining up to be eaten by the human.

While wave power may be useful for small commu- nities on remote islands, I suspect it can’t play a significant role in the solution to Britain’s sustainable energy problem.

Loch Sloy’s surface area is about 1.5 km2, so the hydroelectric facility itself has a per unit lake area of 11 W/m2. So the hillsides, aqueducts, and tunnels bringing water to Loch Sloy act like a 55-fold power concentrator.

One kilowatt-hour per day is roughly the power you could get from one human servant. The number of kilowatt-hours per day you use is thus the effective number of servants you have working for you.

The UK has made it onto the winners’ podium. We may be only an average European country today, but in the table of historical emitters, per capita, we are second only to the USA.

It doesn’t require high-cost hardware, in contrast to solar photovoltaic power.

there is no prospect of significant improvements in plane efficiency.

Figure 20.23. Energy requirements of different forms of passenger transport. The vertical coordinate shows the energy consumption in kWh per 100 passenger-km. The horizontal coordinate indicates the speed of the transport. The “Car (1)” is an average UK car doing 33 miles per gallon with a single occupant. The “Bus” is the average performance of all London buses. The “Underground system” shows the performance of the whole London Underground system. The catamaran is a diesel-powered vessel. I’ve indicated on the left-hand side equivalent fuel efficiencies in passenger-miles per imperial gallon (p-mpg). Hollow point-styles show best-practice performance, assuming all seats of a vehicle are in use. Filled point-styles indicate actual performance of a vehicle in typical use. See also figure 15.8 (energy requirements of freight transport).