Guest post: could we use the ground beneath a London park to generate low carbon heat?

We’re working on an exciting project to investigate using heat pumps in Hackney parks to provide low carbon heat to the surrounding buildings. This week London has officially become the world’s first National Park City - and to celebrate Hackney council have mown the logo into one of their parks! That got our team thinking… how much low carbon heat could you get just from that little circle of park? Louise Waters from Scene crunched the numbers.

To show their support for London becoming a National Park City, Hackney Council have mowed a 20 metre-wide National Park City logo into the grass at Millfields Park.

We’ve been thinking about the renewable heat resource beneath the country’s parks and green spaces as part of the Powering Parks project, working with Hackney Council and Nesta. So we wondered what amount of heat could be generated from the area underneath the logo and the 45 metre-wide circle around it…


There are two ways to collect heat using a heat pump. If vertical ground heat collectors were installed – pipes inserted into boreholes up to 200 metres deep – then this piece of ground could supply up to 80 kW of heat, saving about 15 tonnes of carbon emissions each year. The heat extracted would pass into a heat pump (or several heat pumps) that would ramp up the temperature to a level that could be fed into a building’s radiators, or generate hot water for sinks and showers. 80 kW could heat a medium-sized school, one or two large pubs or 6-10 typical detached homes. 

A lower-cost option might be to install horizontal heat collectors – pipes buried in trenches about one metre deep. But this would mean that only about 20 kW of heat could be supplied (about four tonnes of carbon savings). This could still be enough for a café, community centre or 2-3 individual homes.

In either case, the heat collectors and interconnecting pipework would be fully buried, and the grass above re-sown so that the system is hidden and the park can continue to be enjoyed as normal.

This is just an example of what could be possible with a small area of parkland.  There are no plans for a project like this at Millfields, but parks and green spaces across the country are home to vast renewable heat resources beneath the soil. Ground source heat pumps could offer councils the opportunity to save money on their heating bills or generate revenues to support park operations and improvements, while taking them one step further along their decarbonisation journeys.