London’s parks are known to store carbon in the trees and plants they contain, but did you know they also store energy?

Trials are underway of ground source heat pumps to see if we can harvest energy from our parks and public spaces. Any profits from the schemes can, and should, be ringfenced for parks management, improvements and maintenance.

The ground heats up in the sun during the day and slowly gives off heat overnight. At its most extreme this causes what’s called the urban heat island effect, where city centres are 1 or 2 degrees warmer than their surroundings. The temperature difference may be slight, but it can be amplified.

Putting heat pumps in our parks and playing fields could supply enough clean heat to keep the equivalent of 5 million UK homes warm. This would save a massive 8 million tonnes of carbon emissions each year, helping us to tackle climate change, improve air quality and generate income for councils and park authorities to re-invest locally.

The idea is to use parts of parks where the surface has already been disturbed rather than sensitive, natural areas. Tennis courts, multi-sport pitches and playgrounds would be perfect.

The system involves laying long water pipes underground. This is done without digging-up surfaces by using machines which burrow and lay the pipes in the soil. These waterpipes are then connected to a compressor, where the ambient heat from the water is put under pressure in a chemical mix and gives up its energy to heat another closed circuit of water to heat buildings nearby.

Although the compressors use electricity, the manufacturers have shown that for every unit of electricity used by the system, it generates the equivalent of 5 units in output. Even the heat generated by the compressors is captured and used in the process.

Those behind the trial believe the amount of heat that could potentially be supplied from parks, playing fields and other green spaces across Great Britain totals around 30 GW. That’s the equivalent of about 10% of the country’s total peak heat demand.

Powering Parks is a project by Possible, Hackney Council and Scene. If successful, it has the potential to tackle climate change, improve air quality and generate income for councils and park authorities to re-invest locally. They’ve also promised to share what they’ve learned so other local authorities can do the same.