Monthly Archives: October 2017

Electric Heating

We hear many times from politicians and assorted activists that in order to save the planet we must convert our homes to electric heating. No more carbon dioxide-spewing oil or gas heating, all heating must henceforth be from clean, carbon-free electricity. The future of our planet depends on electric heating!

Politicians love to make these kind of virtue-signalling promises and declarations, but in fact electric heating is a very inefficient form of heating which would result in most cases in more carbon dioxide being released, not less. Here’s why.

The electricity for your home heating will most likely be generated by a gas-fired power station. Yes, you may have wind and solar energy available, but these only work when the wind blows and the sun shines. We need heating mostly at night when it’s coldest, and the sun obviously isn’t shining then, so forget solar. People will be justifiably upset if you tell them that when the wind drops they must shiver, so forget wind for the most part as well. If you want everyone to have reliable electric heating, you must have gas-fired power stations.

A gas-fired power station burns gas in a furnace to make steam, which drives a steam turbine, which in turn drives a generator to create electricity. That electricity is then sent down some long wires from the power station, via various transformers and switchgear and so on, to your house where an electric heater converts the electricity back into heat. In effect, your house is heated by the gas which is being burnt at the power station. The steam turbine and generator and transmission system are just intermediaries to get that heat to you.

Power station

So far so good. But let’s look at the way the process works in greater detail. The steam turbine is what we call a heat engine, whose purpose is to convert heat energy into mechanical energy. You put in very hot, high pressure steam at one end, and the result is a rapidly spinning turbine and some not-so-hot steam coming out at the other end; we have converted some of the heat of the steam into the mechanical energy of the turbine. But herein lies a problem; it’s impossible to convert all the heat in the steam into mechanical energy, and we are therefore forced to throw most of it away. This is why power stations have cooling towers; their purpose is to dump the unusable heat to the atmosphere.Cooling towers

Typical thermal efficiencies for power stations are about 40%, meaning that the energy value of the electrical power that they produce is only about 40% of the energy value of the heat generated by burning gas. The other 60% of the heat is thrown away. There is no way around this problem, which is a matter not just of engineering design but of basic physics.

Now let’s follow that electricity on its way to your house. Electrical engineers have a technical term for long wires carrying electric current; they call them heaters. Depending on how far you are from the power station, you can have a 10% or more loss in the electrical energy being sent to you, because it is dissipated as heat along the way. Consequently, of the original heat that was created at the power station by burning gas, 60% is lost at the power station itself, and several more per cent can be lost along the way, so the heat delivered to you in your house typically represents only about one third of the heat generated at the power station. Using electric heating in your house means throwing away about two thirds of the heat created by burning gas in the power station.

Now contrast what would happen if, instead of burning gas at the power station, you were to burn the same gas in your house in a reasonably efficient gas heater. 80 to 90 per cent of the heat would remain in your house (the rest goes up the chimney). Contrast that with the 30 to 40 per cent of the heat from the power station furnace that makes its way into your house via an electric heater. Burning gas in your house is two to three times more efficient than burning it at a central power station.

If you are really concerned with saving the planet by reducing carbon dioxide emissions, heat your house with gas rather than electricity.