This document sets out the response of the UK Energy Research Centre (UKERC) to the Energy and Climate Change Committee’s Inquiry on Heat.
We would always encourage a “whole systems approach” to energy, certainly including heat with electricity, and ideally transport as well. Such an approach is more likely to encourage consistency between sectors, avoiding perverse incentives but also it is more likely to lead to the discovery of optimal solutions.
In the call for evidence, the Committee makes the comment that there is disagreement concerning the un-used heat from thermal electricity generation with some arguing that this should be used through combined heat and power (CHP) systems, while others suggest optimal energy efficiency occurs through centralised electricity generation plus heat pumps at the local level.
Heat exhausted from large thermal generators has very little use as most of the useful energy has been extracted to produce electricity. A typical temperature of the “exhausted heat” is around 30°C which is too low for district heating systems. This requires heat to be extracted at a higher temperature, circa 90°C, but this does result in lower electricity output from the thermal generators. Typically, 7 units of heat generated by a CHP unit will result in the reduction of 1 unit of electricity output. This contrasts with air source heat pumps where the ratio is 1 unit of electricity to 3 units of heat (typically).
Hence CHP is much more energy efficient but of course district heating system infrastructure is required. Opponents of CHP systems cite this as the major stumbling block but they ignore the electricity infrastructure cost, mainly distribution but also transmission and generation that would be required for heat pumps. They also ignore the customer based cost of the heat pumps, upgrades to home heating systems, etc. Once these costs are all included the economics for CHP are much improved.
A further point to make is that heat provided by CHP will have the lowest carbon emissions compared to other fossil fuel-based heat generation. For example, using typical values, a condensing gas boiler emits circa 210 g/kWht 1 and an electric heat pump circa 120g/kWht 2 . However, for a CHP it is circa 60g/kWht 3
Thus our overall opinion is that CHP (electricity and heat production) and district heating (which encompasses all forms of heat production as well as heat network and other associated infrastructure) do not receive the attention they deserve.