Last winter, I visited friends in London, UK who live in an old Victorian house. When I arrived for dinner, they told me that we could not use the kitchen as it was too cold. The radiators were running at full capacity, but most of the heat they generated leaked directly out of the house. It was impossible to keep the temperature above 10°C, even though the outside temperature was only a few degrees below zero. We ended up eating our dinner in the living room in front of the fireplace, the only room in the house warm enough to be comfortable.
That evening made me think about the challenge of decarbonising heat. It is sometimes said that by electrifying everything or using green gases like hydrogen or biogas, we could solve the problem. In other words, if we change the supply, but not the nature of the demand. Also, in the case of my friends’ house, electrifying the heating system or switching to green gases would reduce the carbon emissions associated with heating.
But this myopic solution ignores a very basic problem in that it would be difficult and wasteful to heat the place to a comfortable indoor temperature by changing the heating system alone. Perhaps with an oversized heat pump or boiler and additional or significantly larger radiators it could be sufficiently warm. Compared to a house with a decent energy performance though, the investment cost would be considerably higher.
What is more, such an approach would also create costs for the energy system as a whole. An oversized heat pump would be a drag on the power system. Wasting valuable green gases and renewables, much needed for other purposes, would be foolish.
This is, of course, an extreme example. But it demonstrates that we need a combination of low-carbon heating technologies and energy efficiency improvements to decarbonise heat. It is the obvious answer.
Numerous studies have been conducted on the ideal technology mix for decarbonising heat, and most (if not all) of them agree that, without energy efficiency, the total cost of decarbonising heat will skyrocket.
A report published in April 2019 by the International Energy Agency (IEA) on the critical role of buildings for the clean energy transition demonstrates both the significant challenges and potential solutions for decarbonising the built environment, in particular as regards heat. It identifies three key strategies as potential responses.
First, sufficiency by avoiding unnecessary energy demand and technology investment by planning, building design and energy technology measures that address the underlying need for energy use without reducing (or possibly improving) service levels in buildings. Second, radical advances in energy efficiency through building fabric improvements and efficient appliances. Third, decarbonisation by replacing carbon-intensive technologies with high-performance, low-carbon solutions.
At the EU level, Eurelectric recently presented its decarbonisation pathways, showing that energy efficiency must be the main source of emissions reduction in buildings, followed by electrification through heat pumps.
These findings are mirrored by national studies. Analysis commissioned by Agora Energiewende shows that a scenario for heat decarbonisation in Germany involving both significant energy efficiency improvements and heat pumps is considerably cheaper to attain compared to a scenario based on power-to-gas. A similar study by the Wuppertal Institute shows that the emission reductions needed to meet climate goals — especially those from the electrification of heating — are much more easily achievable, from both a technological and economical standpoint, if associated with substantial energy efficiency improvements.
Analysis of UK household energy demand scenarios shows that an approach combining energy efficiency and heat pumps can deliver cost-effective energy savings of around 25%. The UK’s Climate Change Committee recently called on its government to significantly increase the rate of energy efficiency retrofits, saying UK homes were “unfit for the future”.
This means that energy efficiency is a necessary condition for successful heat decarbonisation. Proponents of an approach that relies exclusively on energy efficiency are, however, also mistaken. While it might be technically possible to retrofit existing buildings to a passive house standard, it is neither economical nor practically feasible to do so at scale or within the timescales required. In many, if not most, cases, a combination of energy efficiency and low-carbon heat will be the most cost-effective and practical solution. I call this efficient heat decarbonisation.
This message has not got through to enough stakeholders and policymakers or it is assumed that energy efficiency will just happen autonomously. I recently attended a meeting where participants presented scenarios for decarbonising heat by 2050. They assumed that energy demand would stay broadly flat, that no improvements would be made in the energy performance of the buildings to be heated in 2050.
Instead, they discussed a number of technology options, including electrification and hydrogen, assuming that the uptake would be significant both in terms of pace and scale. It remains a mystery to me why it would be easier to electrify millions of heating systems or to convert the gas grid to hydrogen rather than install cost-effective energy efficiency measures.
The key question for policymakers is not so much about what the exact technology mix should be, but how uptake can be achieved at scale and in a sensible way that makes full use of the economic potential of energy efficiency while promoting the lowest carbon heating options available. The alternative is to pursue a decarbonisation agenda at considerably higher cost to consumers and the economy. This is neither practical nor desirable. Let’s not throw money for heat decarbonisation out of the window.
This article is part of a series examining how to decarbonise heating and cooling systems
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