By Dave Elliott
The UK Energy Technologies Institute’s report by Jeff Douglas on Decarbonising Heat for UK Homes notes that ~20% of CO2 emissions are from domestic heating, but says insulation/upgrades won’t cut that enough: ‘the scope for cost effectively reducing the energy demand of existing buildings to the great extent required to meet emissions targets is limited as comprehensive insulation and improvement measures are expensive and intrusive. A several hundred billion pound investment in demand reduction for the entire building stock might deliver less than half of the emissions abatement needed. The most cost effective solutions therefore involve the decarbonisation of the energy supply combined with efficiency improvements that are selectively rather than universally applied, as part of a composite package’.
The ETI report notes that an earlier ETI study, ‘Optimising Thermal Efficiency of Existing Housing’, had concluded that a basic ‘Retrofix’ package of measures could achieve CO2 savings of around 33% at costs in the range of £7,500 to £21,000 per building. A more extensive ‘Retroplus’ package could, it suggested, reduce CO2 by around 45% for between £15,000 and £31,000 per dwelling. However, even with this scale of investment, the ETI noted that ‘the emissions savings across the UK house archetypes are somewhat lower than half the desired 80% target’. And it concluded that retrofitted efficiency measures ‘would therefore be most appropriately deployed selectively to around seven million homes, suggesting a national programme with costs in the order of £100 billion. The above case represents a reduction in the UK’s total primary energy consumption of around 7% over the base case’.
So what else is on offer? The current UK plan is (or was) to replace the use of gas for most heating with decarbonised mains electricity (based on renewables and nuclear), with electric heat pumps seen as a key way ahead, along with efficiency upgrades. But ETI worries about intrusion, disruption and consumer resistance: ‘Current boiler based heating technology is very responsive to peak heating demand, generally delivers appropriate levels of comfort and is the accepted solution in over 90% of households with central heating. Consumers are not greatly engaged in the complexities of energy systems so it will be challenging to displace gas heating in a way they find acceptable. Low carbon heat solutions will need to be at least as effective in meeting consumer requirements as the incumbent gas system and be capable of integration within the building space’.
While some upgrades should be included, it backs heat networks as the better bet. It says that ‘in more densely populated urban and suburban areas, and potentially some rural towns the solutions are likely to involve shared heat network installations with relatively limited household intrusion during conversion’, although it admits that ‘the challenges are building the social and political momentum necessary to introduce new local energy production and distribution assets that are shared by users across whole areas’.
However, this isn’t a one-size-fits-all approach. At most the ETI sees heat networks as supplying under half of heat by 2050 – electricity supplies the rest. Certainly in locations with lower density housing ‘the solutions are more likely to be focused on individual properties, using electrically powered heat pumps or direct resistance heating. Here, the challenges are more about integrating solutions into homes and the wider energy system as these solutions generally have significant space requirements and involve extensive efficiency improvement measures, resulting in substantial investment in the individual properties coupled with electricity infrastructure reinforcement’.
To support this, it would also be necessary ‘to reinforce the local power networks to meet the electricity demands of the individual home solutions’, since the power grid would have to take over from the gas grid. A key point being that heat demand is larger and varies more than domestic electricity demand over the day and certainly over the year. Adding heat networks to the mix helps with that, and could also help with system balancing, via Combined Heat and Power (CHP) plants feeding district heating (DH) networks and heat stores.
Overall the report calls for a system-wide approach, with smart heat demand management and integrated systems optimisation, and certainly its vision stretches beyond the usual technical fix approach, or indeed the conventional ‘just add more insulation’ approach. It feeds into the ETI’s wider scenario work, in which local generation, heat networks and demand management figure strongly, as in its ‘Patchwork’ community orientated scenario: www.eti.co.uk/wp-content/uploads/2015/02/Options-Choices-Actions-Hyperlinked-Version-for-Digital.pdf
It will be a huge task to do all this: the ETI report says ‘This transition will involve whole areas of housing, working at a rate of around 20,000 homes per week over a 25 year period – the equivalent of ten Milton Keynes each year.’
However, some think an overall transition on a large scale is viable, with, for example, local CHP/DH playing a much bigger role in the Thousand Flowers 2050 scenario, developed by the academic ‘Realising the Transition’ research consortium, than in the ETI’s Patchwork scenario. In this much more radical decentral pathway, ‘a large proportion of domestic space heating and hot water demand is met by renewable (biogas) community-scale and micro-CHP systems rather than electric heating systems, helping to reduce electricity demand. In addition, the power generated by these local scale CHP systems replaces a significant proportion of centralised electricity supply.’ www.realisingtransitionpathways.org.uk/realisingtransitionpathways/publications/WorkingPapers.html
In the Thousand Flowers pathway, by 2050, around half of UK electricity use and 60% UK domestic heating is met by distributed and low carbon sources, with devolved governments, municipalities, co-ops and communities playing a major role. There are still some large fossil plants, but nuclear falls to 5GW, so it’s not quite a ‘Zero Carbon Britain’ non-nuclear future, as in CAT’s much more ambitious version, but it’s on the way to that. And of course energy efficiency and low energy house design are seen as essential, cutting energy demand significantly – annual electricity demand falls to 310TWh, from 337TWh as in 2010. That is helped by consumers playing an active role in demand management.
The only perhaps surprising thing is that PV solar (at 16GW) plays a relatively limited role – only making a 4.8% contribution to power needs by 2050. That’s a little odd since some say we could get to 20GW of PV by 2020 (up from around 10GW now), and the ‘prosumer’ experience in Germany indicates that might well happen. Although its contribution is large, wind power also plays less of a role (30GW total) in this scenario than in the ETI’s decentral Patchwork scenario (75GW), which also has 28GW of PV. But that’s because there is 44GW of local CHP/DH in Thousand Flowers. A big new idea – requiring a lot of ‘bottom up’ community and Municipal level initiatives. It sounds interesting and possibly viable, but with the Zero Carbon Homes policy and much else abandoned, who knows whether that can or will happen, given our present political set up! www.realisingtransitionpathways.org.uk/publications