The UK energy industry is in something of a mess. Small power companies are crashing, the big ones seem locked into ever rising costs. How did it get this way? We need to look back a bit at recent UK history to understand what has happened. The newly nationalised UK power sector had expanded after the second world war, with large 2GW coal fired plants becoming the industry standard, and new ones being added, year by year, as demand for power from the coal plants seemed to continually rise. But then, in the late 1970’s, it stopped rising, and new plant orders halted. The industry, and the big power construction companies like Parsons and Clarke Chapman in Newcastle, never recovered from the loss of what had seemed to be an automatic 2GW p.a. forward ordering programme.
The market was changing, and new technologies were also emerging- gas fired combined cycle turbines and new nuclear plants. The Thatcher government elected in 1979 was keen on the latter, but in the event was only able to build one new PWR at Sizewell. It was gas turbines that boomed, small cheap-to-build plants, using North Sea gas, popping up all over like mushrooms, aided by the privatisation of the power sector. That made life very hard for nuclear, as well as big coal plants- with the coal sector anyway being much diminished by Thatcher’s attack on the Mineworkers union in 1984-5.
The dash for gas also killed off another option that had emerged as a possible way to keep coal use going- Combined Heat and Power (CHP). That had been promoted in the 1970s by academics and energy technologists who pointed to the huge energy losses associated with electricity generation in thermal power plants. Around two-thirds of the primary input energy was wasted, rejected into the environment as waste heat. If some of that could be recycled, then the efficiency of the plant could rise to 70-80% or more, with the heat being fed to district heating (DH) networks in cities.
The coal-fired CHP/DH prescription was popular with some Labour controlled municipal authorities, and there were plans for city-wide projects in Sheffield, Leeds, Newcastle, Nottingham and elsewhere. But city-wide district heating pipework would be expensive to build, and, in the 1980s, with local authority budgets cut back under Thatcher, the plans came to nothing. There were still UK enthusiasts, but, although, once installed, CHP/DH could be attractive, in the short term, the installation costs and disruption associated with large infrastructure projects like this were seen as a disincentive. In theory, however, some said smaller projects might be more viable. In the early/mid 2000s, in the UK post power market liberalisation context, there was some interest in gas-fired micro-CHP, small domestic total energy systems using Stirling engines to supply heat as well as power, but, in the event, that market failed to take off significantly.
As it stands at present, for good or ill, in the UK, we are looking to another technology entirely to meet heating needs- heat pumps. They too have a long history. Back in the 1970s, when, for example, the Open Universities pioneering Energy Research Group was promoting CHP/DH, it was also pushing heat pumps- although a gas fired version. Nowadays the focus is on electricity powered units, with the expectation being that, under the right conditions, they can generate heat up to four times more efficiently than just by using the power direct- or via its conversion to green hydrogen. That sort of efficiency gain is obviously welcome, although it is interesting that CHP/DH systems could in effect be seen as having even better Coefficients of Performance (CoP), maybe up to 9 or more, compared to the CoP of 3-4 for heat pumps, depending on the temperature required.
The current policy situation in the UK is that ‘heat nets’ are being looked at as one option, along side heat pumps and also hydrogen, for domestic heating. So CHP/DH is still on the agenda, most likely gas-fired, with coal no longer seen as acceptable, even if burnt with high CHP efficiency, although biomass-fired systems are also viable. Indeed, the government has been trying to ensure that, when biomass/biogas is used for large scale heating, it is done with CHP to improve the efficiency of fuel use. There are also other green energy heat options. Geothermal power plants, using heat from deep underground, can be run in CHP mode, upping the system efficiency. Solar heat, collected by large solar arrays, can also be fed to heat nets, either directly, when available, or via large community heat stores, so that summer solar heat can be used in winter time. Natural gas or biogas fired CHP/DH is generally cheaper, but if heat nets already exist, solar heat can be a useful top up, and there are some large partly solar-fed inter-seasonal heat stores linked to local heat nets in Denmark and elsewhere in the EU.
More generally, CHP plants linked to heat stores can also play a role electricity balancing variable output from renewables like wind and solar, by varying the ratio of their heat to power output and feeding any surplus heat to the heat store. If there is too much green power on the grid, the CHP plant can produce mostly heat. If demand for that is low, it can be stored. If variable green power availability is low, the proportion of CHP plant power output can be raised, and if there is still demand for heat, it can be drawn from the heat store.
CHP/DH does require a reasonably nearby urban or perhaps suburban heat load to be viable, although heat can be sent quite long distances without significant losses, as has been demonstrated quite widely in continental Europe, where district heating is widely used and promoted. Oslo’s district heating network is fed via a 12.3 km pipe from a waste burning plant in the city outskirts. In Denmark, there is a 17 km link from a CHP plant to the city of Aarhus. The Helsinki CHP/DH system supplies over 93% of Helsinki’s heat, and includes a plant linked in via a 30 km pipe in a tunnel, while, in the Czech Republic, heat is delivered by a 200 MW capacity heat main to Prague from a power station 65 km away.
However, although it can once built supply cheap low-carbon heat, building extensive pipework like this will add to the project cost, and, although it can be reduced with insulation, there will also be heat losses. So it usually makes more sense to locate plants near to the load, which, in the case of cities, may be unacceptable, in safety and security terms, for nuclear plants, even small ones, though they might find a role in supplying heat for industrial processes in more remote areas.
Although it does have a few on-site gas-fired CHP/cogen plants, providing heat and power directly for industrial processes, and some biomass-fired CHP, the UK has so far trailed behind most of the rest of Europe in terms the wider use of CHP/DH. While around 15% of the EU heat come from CHP at present, the UK only gets around 1% of it building heat from heat nets. The UK governments advisory Committee on Climate Change has suggested that this could be increased to 18% by 2050. Given the potential for cheap flexible low or zero carbon CHP/heat net systems with high reliability (load factors of 80-90%) and multiple energy input possibilities (natural gas, biogas, bio-wastes, geothermal heat and solar top ups) and multiple output end-use applications, that doesn’t sound very ambitious. There can be problems with heat nets, and with collective heat provision generally: maintenance is vital to ensure reliable supply. But there can also been reliability issues with individual domestic heat pumps, while some say that large heat pumps feeding heat nets would be a better idea. The best of both worlds?
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