station could be captured for a useful purpose without impairing the power

station’s electricity production. This sadly is not true, as the numbers will

show. Delivering useful heat to a customer always reduces the electricity

produced to some degree. The true net gains from combined heat and

power are often much smaller than the hype would lead you to believe.



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%.



The government has a target for growth of combined heat and power

to 10 GW of electrical capacity by 2010, but I think that growth of gas-

powered combined heat and power would be a mistake. Such combined

heat and power is not green: it uses fossil fuel, and it locks us into continued

use of fossil fuel. Given that heat pumps are a better technology,

I believe we should leapfrog over gas-powered combined heat and power

and go directly for heat pumps.



Heat pumps

Like district heating and combined heat and power, heat pumps are already

widely used in continental Europe, but strangely rare in Britain.

Heat pumps are back-to-front refrigerators. Feel the back of your refrigerator:

it’s warm. A refrigerator moves heat from one place (its inside) to

