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Green heat and energy saving

By Dave Elliott

Heat supply is one of the key weak links in the UK government’s attempt to meet the EU-imposed 15% by 2020 renewable energy target. That target still applies – until the UK finally leaves the EU, if it ever does fully. Although there is talk of green heat networks, for the moment the focus is mostly on direct green heat supply for business and private consumers, and there are some changes underway. The UK’s Renewable Heat Incentive (RHI) has escaped cuts so far. Indeed it is set to expand, but the government wants to restructure it to keep energy costs down for consumers and get better value for money. So, concerned also about impact on food growing, it wants to support the use of food and farm waste-based biomass feedstock rather than crop-based feedstocks for biogas production in Anaerobic Digestion (AD) plants. It has also proposed cutting support for solar heating since it is not seen as good value for taxpayer support.

The Solar Trade Association was none too happy about the solar heating cuts: ‘If the proposals go through, the internationally proven technology will be cut out of the Renewable Heat Incentive entirely next year’. It’s odd, given that Denmark, with a similar climate, is pushing ahead with solar heat, including inter-seasonal solar heat stores feeding heat networks.

On biomass, the Renewable Energy Association (REA) said that if the RHI changes proposed were approved, the resulting collapse of the biomass heat industry would mean job losses and a significantly slowed rate of decarbonisation. Though UK progress had been limited, biomass represented 89% of the renewable heat in Europe and the REA worries about cuts in UK support levels, the new policies favouring heat pumps and shifting biomass feedstock eligibility away from energy crops to wastes: ‘We need a range of technologies to decarbonise a range of properties. Rural locations, for example, with no access to a gas network cannot be left behind. Biomass boilers are low-cost, provide significant carbon savings compared to oil boilers, and support the growth of healthy British forests. For many properties, biomass boilers are a pragmatic low-carbon alternative. It is distressing that the Government’s proposals would shutter this growing industry and would have us rely instead on largely untested technologies.’ But it welcomed the support for AD.

However, some practitioners see problems with biomass and some of the other new green heat options supported by the RHI and by DECC (while it was still around!), including heat networks, with £1.5 m for 27 heating projects across 24 local authorities in England and Wales, and a £320m policy/project option review exercise: .

The Energyst trade journal surveyed 80 practitioner’s views on UK green heating. Its editor concluded that it showed that, with gas heating still being cheap and well established, ‘there is currently little incentive for companies to start paying serious attention to renewable heat unless it is going to save them money and deliver reasonably quick payback. Respondents interviewed for this report said that many renewable heat technologies are simply not cost competitive. Others said that heat subsidies in the main are unattractive for all but the largest biomass installations, many of which are, funnily enough, larger than they need to be. Meanwhile technology remains expensive and can be rendered inefficient through poor operation and maintenance’.

He noted that: ‘Heat networks undoubtedly have merit. They are assets that infrastructure funds will find attractive, bringing in extra capital. But DECC’s own figures predict that the £300m it has set aside to boost local authorities’ chances of getting projects off the ground will at best result in lower carbon heat for the equivalent of 400,000 homes. That equates to 1.5% of the UK’s 26.5 million households. Retrofitting heat networks will also be very challenging. The truth is that decarbonising heat, while perhaps technicallynot that difficult, will be extremely expensive due to the disaggregated nature of the task’.

So overall he felt that ‘until renewable heat technology becomes more cost competitive, or the available incentives reallocated to genuinely support the lowest cost solutions to decarbonisation, energy efficiency is likely to be our best bet. Also, a major drive on insulation and efficiency would mean a much lower peak than the 360GW currently needed if we were, eventually, to meet heat demand by switching from gas to renewable electricity. Now that would be expensive’.                                                                           

One of the contributors to the review noted that, according to one estimate, ‘heat networks would require subsidy of 75p/kW hour to create the seven-year payback periods sought by investors’, which ‘would make even Hinkley C look cheap’, although it was also noted that they were multi-decade infrastructure assets, so that longer term payback periods were reasonable. There is certainly a good case for heat networks: plugging into them can even be a cheaper option than major insulation retrofitting programmes in some types of building e.g. old high-rises, and they can use a range of fuels, including renewable sources, and be linked to large efficient community-scale heat stores.

Certainly there were contributions in The Energyst survey backing other options, including domestic-scale solar heat storage, with one possibility being the use of magnesium sulphate heptahydrate, otherwise known as Epsom salts, widely used to treat indigestion. ‘If you heat it, dry off the water, keep it somewhere dry, go back a few months later and add some water to it, it will get up to about 80 degrees C,’ said Chris Sansom from Cranfield University, UK. Whereas hot water stores around 150MJ/cubic metre, he said Epsom salts store around 2000MJ/cubic metre. His students are building seasonal storage units ‘about the size of a small shed… something you would put in your garden or loft’. And that is with standard, off-the-shelf solar thermal panels. More advanced panels he says, ‘will reduce the footprint further’.

However, the report also includes strong support for energy efficiency, for example for nanotech coatings for windows and walls, which it’s claimed can reduce heat loss by up to 40%.  That’s certainly worth following up.  The idea is being explored in the US, where Berkeley Lab scientists are developing a low-cost paint-on coating to reduce energy losses through windows. It’s estimated that 10% of all the energy used in US buildings can be attributed to window performance, costing building owners about $50 bn p.a, yet the high cost of replacing windows or retrofitting them with an energy-efficient coating is a major deterrent. US DoE Lawrence Berkeley National Lab researchers are addressing this problem with creative chemistry, using a polymer heat-reflective coating that can be painted on at a tenth the cost.  

So will and should the emphasis shift from green heat supply to energy saving? There is no question that energy efficiency has still not been taken seriously enough, so there is plenty that can and should be done: . Certainly, abandoning the Zero Carbon Homes policy is not very helpful.  Buildings are clearly a major target for energy saving. But the potential for energy saving is also huge in other sectors, including industry. For exemplars of best practices from around the world, see this UNEP report. One of its authors noted that a University of Cambridge study has said that ‘73% of energy used in industry can be saved using currently available technical know-how and technology’. But the IEA says under 1% of global average energy savings are currently achieved by industrial energy efficiency. We need to try harder in that and other sectors. However, that doesn’t mean that we can ignore green heat supply: we need to do both.  Even in the UK, when and if it leaves the EU. Thankfully we still have our own climate targets, recently confirmed and consolidated, which means we have to go flat out on all the options.

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