. . . back to part 2 . . .

How much is inside hot water? - part 3

Let's look at these numbers:
gas method kettle method
0.3 kWh of chemical energy
0.11 kWh of electrical energy
and
0.06 kWh of chemical energy
Total: 0.3 kWh of energy
Total: 0.17 kWh of energy
In terms of energy used in the home, the kettle method uses least.

PanKettle230

However, this is not the full story. In Britain, and almost all countries, extra electricity demand is met by turning up a fossil fuel power station.

Eggborough power station
But, in my house, I buy my electricity from Good Energy, which means that it all comes from windmills, right? I don't think so. Even if I stick Good Energy stickers all over my kettle, the truth is that whenever I switch the kettle on, a fossil fuel power station somewhere has to turn up a little.
And in Britain, power stations convert chemical energy to electricity with an efficiency of roughly 40%; then 8% of the electrical energy is lost in the electricity network. (That's an overall efficiency of 37%.) So every 1 kWh of electricity that I use entails the consumption of 1 kWh/0.92/0.4 = 2.7kWh of chemical energy at the power station.
So the energy balance sheet looks like this:
gas method kettle method
0.3 kWh of chemical energy
0.11 kWh of electrical energy, which involves the use of
0.3 kWh of chemical energy (at the power station)
and loses 0.19 kWh of heat (mainly in the cooling tower and a little the electricity network)
and
0.06 kWh of chemical energy (gas at home)
Total: 0.3 kWh of energy
Total: 0.36 kWh of energy
So when we take into account the way power stations work today, the two methods actually use roughly equal amounts of energy. The gas method uses slightly less.
GreenK

Continue reading part 4 of How much is inside hot water...

 
 
 
 
 
 
 
 
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This page is a tribute to cockeyed.com


To find out more energy numbers, you might like to read my book Sustainable Energy - Without the Hot Air.


David MacKay
Last modified: Tue Jun 24 00:56:10 2008