1. Social
April 9, 2018

Could heat-only nuclear help us decarbonise British cities?

By Alistair McCay

As a country, the UK will not meet future climate change targets unless we figure out how to heat and cool our cities without burning vast amounts of natural gas. Towns and rural areas also need to decarbonise their heat supply, of course. But cities being what they are, the greatest amount of energy going into keeping people and equipment at reasonable temperatures are in cities.

Renewable heat only supplying around 5 per cent on annual heat demand in the UK, and isn’t increasing anywhere near as much as needed. The UK government has introduced a world-leading Renewable Heat Incentive (RHI), which paid out cold hard cash to households and businesses to produce heat from renewable sources, with 90 per cent of installation being biomass. But the RHI at a household level has not been nearly as successful as comparative schemes for solar PV, likely due to a higher hassle factor, despite being potentially more financially lucrative.

Highly concentrated heat demand allows heat networks in cities to be economically viable, compared to towns or suburbs. Heat networks are essentially pipes of hot water, much like gas pipes. In cities, these networks can transport heat to where it is needed from large heat productions plants, or from processes which make waste heat in a city, like subways, sewers, or digital heavy infrastructure.

Many UK cities already have heat networks in place – but they are almost all based around burning gas. This is acceptable now, as combining heat and power production lowers national carbon emissions, but it comes at the cost of a huge point source of air pollution in a populated area. Although a properly designed flue should result in minimal emissions actually reaching people, it’s clearly a problem for the long term. And don’t feel this doesn’t affect you if you are running a biomass boiler or even a pretty wood burning stove in a populated area, air pollution restrictions might be coming your way.

There is good news as British cities are starting to move away from just burning stuff for heat and towards long term low carbon solutions – ones which don’t have impacts for air quality. Technologies like water source heat pumps can extract the low grade heat from our rivers or the sea, and boost it to useable temperatures. Rivers effectively act like massive solar collectors, gathering heat from their catchments and bringing into cities where it is needed (cheers, nature).

British cities with a legacy of mining are also starting to seriously look at their mining legacy as an asset to support heat extraction and storage in a dense urban environment. This strategy has been hugely successful in the Dutch city of Heerlen. But heat pumps still need power from the grid to work, and since they will be mostly used in winter the end result on the power grid is likely to be our gas or coal plants turned up slightly.

However there’s one solution which we’re not talking about, which perhaps we should be. It’s very low carbon, creates no air pollution, produces heat easily at higher temperatures, and doesn’t put extra demand upon the power network.

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That solution is nuclear – but not as you might know it. There are some grasping projections of how we could build small modular nuclear power reactors, place these near high heat demands (cities or industry) and reap almost continuous large volumes of high grade heat. But our electricity grid is rapidly decarbonising – so what if we did away with the electricity generation of nuclear and just sought the heat generated?

Producing only heat would significantly decrease the cost of each plant, as the nuclear fuel rods wouldn’t have to bother heating steam to hundreds of degrees celsius to drive turbines. For direct heat we would need relatively low temperatures (around 90°C maximum), simple heat exchangers are all that is required to ensure total isolation between the nuclear fuel and the heat under the streets and in our homes. This would result in claims of comparative costs per unit of heat delivered as gas.

Of course, an important component of plausible energy scenarios for the UK is social and political acceptability. There’s no point designing what will just be rejected by the public and elected representatives – and having a nuclear reactor in the centre of British cities, well, that might be a problem. Fortunately, there are many routes to decarbonising heat in the UK, which don’t rely on using nuclear heat

Meanwhile, China is currently undergoing a huge shift away from coal for heating, mainly driven by dire need to improve air pollution. Some homes may have even been left without heat during winter due to such effort to rapidly move away from coal.

China’s district heating networks consumed more energy in 2015 than the whole of the UK, and the majority are based around coal. Heat-only nuclear reactors have been trialled and operated in China. Wider roll out could occur from 2020.

So could your heat be provided by a heat only nuclear plant? If you’re visiting northern Chinese cities in the futures, then maybe.

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