Clean heating ain’t easy – so make it good

by | 2 Jun 2022

One of the hardest issues to solve in decarbonising Scotland is heating. So what are the issues - and how do we get it right?

First published by Common Weal

As we reach the third week of Common Weal’s Our Common Home campaign we reach the part which gives people most difficulties – heating. It gives difficulties purely for one reason; there is no simple answer to the problem. We have to do something but anything we do is hard.

Why is it so hard? For anyone who knows their physics, heat is the easiest form of energy to generate (to the extent than in endless applications such as microchips or engines the whole aim is to not generate heat). Doesn’t that make it an easy fix?

Here’s part one of our problem; because heat is so simple to create we are used to heat coming from sources which are cheap. Which is to say mostly we burn stuff, first wood, then goal, then oil and gas. It is simple – you heat it enough and then it does it’s own thing. Of course that is at the heart of the whole damned problem in the first place – burning things is dirty. The energy is inexpensive but costs us in other ways.

The other big problem with heat as a form of energy is that it is easy to generate but not easy to transmit or move around. Heat is easy to generate because it is ‘disordered’ (it’s basically just a bunch of particles getting very excited and going all over the place). Ordered energy like light and especially electricity transmits much more easily because they form waves. Likewise burnable fuel can be transported fairly easily. Heat just goes everywhere.

This is the basic conundrum – the cheap and easy way to do it is easy to transport but is making our planet unliveable. The clean way to do it which is easy to transport/transmit is very expensive. And the clean way to do it which isn’t expensive is very hard to transmit.

So what are the options? Let’s just rule out the use of ‘blue, brown or any other colour of hydrogen which isn’t green’. These are all just ways of laundering petrochemicals back into the energy system and should not be considered. If we do that then we come to three options in which the energy needed is easily transmittable, though basically they are three ways to heat your house with electricity. (All the information and data in this piece can be found in the Common Home Plan.)

The first way is just to heat your house using electricity via electric radiators and electric water heating. Radiator technology has moved forward so they are more efficient than they used to be – but there are two major problems.

The first is that almost everyone in Scotland has water-based radiators – you heat the water, pump the water through a radiator and then the radiator heats the room. So to switch from that system to an all-electric system means taking out all the radiators and piping and getting rid of your gas boiler in favour of an electric immersion heater.

That’s a lot of work, but any option is a lot of work. The thing is, it’s also expensive. Switching from gas to electricity will triple your heating bills. It’s that difference between ordered and disordered energy again – it’s hard to make electricity compared to making heat, so making heat from electricity is expensive compared to just making heat. Think of it like trying to make sand by finely crushing lots of wine glasses.

The cheap and easy way to do it is easy to transport but is making our planet unliveable, the clean way to do it which is easy to transport/transmit is very expensive, and the clean way to do it which isn’t expensive is very hard to transmit

The second electricity option is to make green hydrogen by running electricity through water and splitting it into hydrogen and oxygen. You capture the hydrogen, send it to houses through gas pipes and then burn it in your existing gas boiler.

There is a lot of complication to this – you don’t want to put pure hydrogen into the boiler because it burns too hot so you need to do a 50/50 mix with some inert gas like nitrogen and hydrogen does not play nicely with metal making it brittle, and you certainly don’t want odourless and highly explosive gas leaking.

But let’s set these issues aside because there is a more fundamental problem – hydrogen is something like seven times more expensive to heat your house with than natural gas. It is even less efficient to turn water into hydrogen than just using the electricity to produce the heat (though hydrogen lets you keep your boiler and radiators – see, it’s all complicated).

So let’s look at what is viewed by many as ‘the saviour technology’, Air Source Heat Pumps (ASHP). After all they just suck heat out of literal thin air, right? Well, kind of, in the way a fridge just ‘kind of’ pushes all the hot air out leaving only the cold air. You can describe it like that, but it’s not a very accurate description.

Actually, what you are doing with an ASHP (which is just a ‘reverse fridge’) is more accurately described as ‘using electricity to drag the heat out of the air’, and the less heat there is in the air the more electricity is needed to get it out of the air.

At home we had a heating engineer out for a boiler problem and they offered us a quote for an ASHP and it was telling. Basically it would be cheaper for us to run in the summer months but more expensive than our current oil boiler over the winter. Which is unfortunate as we don’t heat the house in the summer. That shows the problem

ASHPs are more efficient at creating heat than electric radiators for much of the year, but they are expensive in and of themselves, need substantial effort to fit them, they are best at producing low levels of heat on a continuous basis which is very different from how we currently heat our homes and because they are mechanical they will inevitably break down sooner or later.

So why is it that you hear a lot about hydrogen and ASHPs? A good way to think about it is this; hydrogen heating is how the oil industry keeps the heating market out of the hands of the electricity industry and ASHPs are how the electricity industry steals the heating market from the oil industry.

And why are politicians so keen on talking about ASHP? This is purely cynical – it’s the source of heat which gets them off the hook the most because they don’t really need to do anything. They can offer grants, expect you to do it for yourself and leave it at that.

All of these solutions approach the problem from the ‘ease of transmissibility’ angle, using easily-transmissible energy sources that can be sent down existing infrastructure. But doing that doesn’t actually do much to reduce the disruption, it costs a lot more and it requires upstream investment (basically, you need to build a lot more electricity generation and reinforce the grid to be able to deal with the heating surges).

I’ll skip over various forms of biofuels or ‘ecogas’ (recovered from the methane coming of landfill) because while they will be significant for houses which are off the gas grid, we can’t produce anything like enough of them to be a solution in most homes.

So what if we approach it from the other direction – are there cheap ways of creating heat? Yes, there really are. In fact there are a number of ways of doing it. You can burn biomass, you can recover heat from all kinds of things like old mineshafts, rivers, geological formations or from places where heat is wasted such as industrial plants. You can also use electricity without sending it through the grid by heating something directly (which is much cheaper).

District heating is the cleanest option, it is the longest-lasting option, it is the most reliable option and it is by far the cheapest option once installed.

But among the cheapest possible sources of heat is solar thermal (which is much, much more efficient than solar PV which produces electricity). Solar thermal panels are cheap and long-lasting. You just need to find a way to store the heat because you get way too much in the summer and not enough in the winter.

And this is where the transmissibility problem comes in – with all of these options you then need to get the heat from the place where you generate it, store it somewhere and then distribute it to houses. Storing the heat is surprisingly easy – just put a heat exchanger into a gravel pit filled with water and insulated above, put heat in when its available and take it back out again when its needed.

The problem comes from getting the heat to the households. None of these options can be applied directly to a single house because none of them generates enough heat alone. It needs a cocktail of them and it is much more efficient to do it at scale anyway. So you need a heat network – and that is why there is public policy reticence.

Because where an ASHP is your problem, creating heat networks is government’s problem. The way you transmit heat is by sending very hot water through pipes to homes. You replace your boiler with a heat exchanger, take the heat out of the hot water and use that to heat your house. It has minimal disruption in your house, but more disruption than the other options outside your house.

You need a ring main from the main heat stores (heat networks can be heated at any point along the ring main) and then sub mains to each house. That’s a lot of holes to dig and a lot of pipework, meaning a lot of disruption.

So why did Common Weal chose this most disruptive option? Because for so many reason it is the best option. Any way you look at this problem the total cost of anything you do is going to be in the order of £30 billion to £60 billion, so it helps to focus on what you get for your money.

And on that basis, district heating (the heat networks model) is the one you’d choose as a householder if you could choose. It is the cleanest option, it is the longest-lasting option, it is the most reliable option and it is by far the cheapest option once installed.

It is clean because you can capture lots of truly zero-carbon heat without needing to generate more electricity. It is long-lasting because it has next to no moving parts so could last for hundreds of years once installed and because if new heat technologies come along you can just ‘plug them into the system’. It is reliable because its mostly just pipes with no moving parts so doesn’t need much maintenance. And the energy is very cheap to generate and doesn’t compete with other energy uses.

Sorry this article is a little longer than usual but it is important that people are helped to understand this issue. We are doing what looks cheap and easy (ASHP) but in reality it is neither. It’s just short-termism. We are ignoring what is by far the best long-term investment for households because it takes more work. And we’re barely talking about the issue either way.

In the end, in a world of no easy solutions it is worth thinking which solution you would prefer to live with. You may not know it yet, but that would be a clean renewable heating network (known as district heating) providing reliable, cheap heat without massive disruption in your house.

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