In a previous post I have touched on why I don’t think CHP is the answer to all the UK’s problems. This time I want to expand a bit. I am not saying that CHP is bad, I am just saying that some people are overrating it. I will try and look at two things here, district heating CHP and microCHP (μCHP).

Let’s start with district heating. So in district heating there is a power plant in the middle of the community (figuratively) and its main role is to generate electricity. But when it generates electricity it also happens to generate heat and this heat is used to heat up the houses and water of the neighborhood. Now there must be some metering mode for the heat, otherwise it is subject to the tragedy of the commons and everyone will have their heating on maximum all the time. If it happens to be too hot they could just open a window, at least they are ventilating their houses.

Ok so we put a meter on the heat exchangers in every house. Now people are paying for both heat and electricity. Come the summer and no one wants the heating on, so everyone turns their heating off. So all the CHP heat has to find somewhere to go. This might actually end up costing the power plant owner some money for a cold utility to take the heat away. Lets hope the neighbourhood is near a river or a sea so they can just pump that water through. Yes there is still demand for hot water, but this is nowhere near as much as required for heating space and water.

OK, I can hear you saying Trigen. Put an absorption refrigerator there and cool the place. This way we haven’t wasted the heat. Now I am quite certain that the efficiency of the refrigeration process is lower than the heating process, so all those claiming 95% efficiency can stop it. It’s better than completely wasting it, but then if we weren’t going to use it in the first place are we wasting it or not?

British people rarely need air conditioning during their two-week summers. There is a substantial time when the weather is somewhat mild, according to British standards, and heating and cooling are not greatly required. What happens then? If they use the heating or cooling when they don’t really want to then it’s wasteful, and if they don’t use it it’s also wasteful. It all depends on the way you look at it.

This would probably be a typical scenario where people become complacent with their energy use because they feel like they have already been more efficient. Buy the energy saver light bulb and keep it on all the time kind of thing. This completely defies the point.

Next post μCHP…