Low Carbon Heating
More than a third of the UK’s greenhouse gas emissions are a result of heating. This is a major challenge to the government’s aim to reduce annual greenhouse gas emissions by at least 80% of 1990 levels by 2050. The Renewable Heat Incentive is due to end in 2021 and a ban on the installation of natural gas boilers in new homes built in England from 2025. Other political measures are likely but much is still to do especially as the vast majority (85%) of homes in the UK are heated by natural gas (a fossil fuel).
To decarbonised building heating in the future we are likely to use mix of electric heating (heat pumps as well as direct electric and storage heating) run on increasingly green grid electricity; district heating networks with low carbon heat sources; and conversion of gas networks to biogas or hydrogen.
There is an urgent need to instil a massive change in behaviour of millions of UK home owners, planners and developers to ensure the new modes of heating. Aside from technical issues, the main challenges are cost (both upfront and running cost – gas remains cheaper than electricity per unit), industry skill levels and customer acceptance. (Source: https://www.energysavingtrust.org.uk/ )
With this in mind my watercress farmhouse is designed within an eco-community of twenty farms on a three acre site that can happily produce wind turbine and solar energy for shared use. Neither of these can be constantly reliable and will always need maintenance. Even if the site had a fast flowing river hydro energy would provide the same issues.
This said, the building will have photovoltaic panels on the roof which would be enough to run a heat pump of which there are a variety of technologies; geothermal, ground source, air source, water source and earth energy.
Broadoak.co.uk explain this clearly;
In the same way that your fridge takes the heat out of a bottle of white wine and externalises it (which you can feel at the back of the fridge when it’s cooling things that were originally warm or at room temperature), heat pumps remove solar energy stored in the earth, air or water around your property, compress it to a higher temperature and transfer it into your hot water tank central heating system and/or hot water tank.
A ground source heat pump requires adequate outside space for the pipes which are typically buried in trenches. As I am using the majority of the 200 sq.m. of my allocated plot for watercress growing swales - not to mention granite piers and fondations - the amount of space for the pipes would be restricted unless the community as a whole considered using the large common areas between houses. However, this may be impractical since any spare land is to be used as much as possible for growing crops.
Air source heat pumps take up much less space, but you do need a sufficient distance between the system and your neighbours.
One of the best explanations of this systems is provided by the Scottish Energy Saving Trust:
A document prepared for London by Etude identifies some of the issues in new heating systems and uses some real examples:
There are some drawbacks on these systems and educating the users adequately on how to use them is paramount.
Noise and vibration is often an issue and a small air source heat pumps typically produce around 40-55 dB(A) at a distance of 1m, with noise falling as distance increases (42dB being a maximum optimum). Medium size units would produce more noise and would need to be placed more carefully.
The first video and these below explain air source heat pump systems which according to the Etude study mentioned above is slightly less efficient than the ground heat pump method.