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Our Common Home

Heating in Scotland, discovering the best option.  

In Scotland, 95 per cent of our heating emits greenhouse gasses – the highest proportion in Europe. This is one of the most complex problems to solve in becoming an environmentally-responsible nation. It is worth explaining why this is. 

The first problem is that if we use the existing infrastructure, there is no alternative to the natural gas which heats most houses. Biogas (often methane from processing waste) has a very important role to play (it can be the source for LPG gas cylinders used in off-grid houses) but it simply isn’t possible to produce anything like enough to replace natural gas. Hydrogen can also be mixed with natural gas, but only a small proportion (about ten per cent) because hydrogen tends to leak straight through existing gas pipes. It is also about eight times as expensive as gas. 

Electricity is often assumed to be the preferred option, but this is much more difficult than it seems. First, it will take a lot to install the additional renewable electricity capacity simply to replace gas-fired power stations, which must then be doubled again if we are to move to electric and hydrogen vehicles. Electric heating would require this to be tripled over the same period. Even if this was achieved, the impacts on the grid could be severe; while the average load on the grid would double, most of us put on our heating and have showers at similar times, and because this is also when we are boiling kettles for tea and cooking, the peak load could be many times more than double and this would cause serious grid instability. It would also require the heating systems in most houses to be replaced which is an enormous task – and electric heating is three or four times more expensive than natural gas, even when using the most efficient new electric heaters. (Air source heat pumps are often proposed as part of the solution but these are expensive to fit, much less effective than people believe and simply don’t work in the winter when air temperatures are low but heating is most required.) There are many other ways to generate heat, but none of them can be both fitted to a single house and also provide all the heat that house needs. 

There is, however, another solution. While renewable heating technologies can be very cheap indeed (even cheaper than natural gas), they must be combined to meet total need, and to do that there needs to be a way to deliver the heat to the homes. This can be achieved through a district heating system. District heating is when every house is connected to a grid that delivers hot water directly, just like electricity. A big very-hot-water ring main is installed round a town or city. From the ring main a network of local grids will feed heat directly to houses. The water that comes into the house will be very hot indeed and so will go into a ‘heat exchanger’ which will extract some of the heat from the water for use. The heat exchanger will simply replace the current gas boiler and the rest of the system in the house will stay much the same as it is. Installing district heating to every house is an enormous engineering task, but once installed it can last for hundreds of years and the heating provided would be very inexpensive. Alternatives might be slightly cheaper and easier to install, but the result would be an expensive and unstable system which would require replacement in the near future. For this reason Scotland should install district heating to every house. This will be the biggest and most expensive single task in the Common Home Plan, but the results will be worth the investment. If any urban house cannot be connected to district heating, then the next option should be a new hydrogen or electric system – but there would have to be a very good reason to do this and those households would need to be compensated in some way for the high cost of heating. 

It is often assumed that rural homes cannot have district heating systems, but this isn’t correct. While the distances are greater, the cost of installing them is lower and so the overall cost is similar. But many rural households aren’t on the gas grid (a good indicator of whether a district heating system is viable) and these will best be served by biomass or bioLPG boilers, in combination with ground source heat pumps where possible. 

The ring mains which serve the district heating systems must themselves be heated. The most efficient heating source is solar thermal (which is a much more efficient use of solar energy than using it to produce electricity), but this must be combined with inter-seasonal heat storage so the heat of the summer sun can warm our houses in the depth of winter. Solar may provide about half of heating need. What other sources are used will depend on the specific geography of each area - where there are disused mines, much will come from heat recovery while if there are nearby sources of wood fuels, more from biomass. ‘Redundancy’ is spare capacity which can be ‘turned on’ when there is particular need (such as in prolonged spells of very cold weather). Hydrogen is a good option. for redundancy capacity. 

A National Energy Company should install district heating to every house. From ring main to house (including boiler replacement) this should cost about £10,000 per house and require about 5,000 staff of which about a third will be skilled trades. As with the National Housing Company, this size of workforce can fit about 60,000 houses a year, and so that workforce must also quickly double in size to complete in time. The ring main and the various heat-generating plants and inter-seasonal heat store systems will need to be put in place first. 

This will require complex planning, so a Scottish Energy Development Agency should be established. All new-build houses should be required to put in the infrastructure for district heating, even if the ring main in their area is not complete, and no new houses should be built with natural gas heating.