Geothermal heat pumps in Enfield Social Housing
Overview
In the north London town of Enfield, eight tower blocks with over 400 flats were retrofitted with ground source heat pumps to connect to a network of ground loop arrays supplying the residents with clean and affordable heat. This heating replacement is expected to save 773tCO₂ per year - a number that increase over time as the share of renewables in the electricity production rises - and reducing energy costs for tenants by 50% and more preventing them from slipping into fuel poverty. The project, which was delivered in 2017 - 2018 by Kensa Contracting and ENGIE was selected as 2019 District Heating Project of the Year (H&V News Awards).
The shared ground loop network and networked heat pumps
Replacing the electric heating system in the Enfield Council tower blocks took less than a year during which time tenants were able to stay in their homes. The ground loop system consists of 100 boreholes ranging from 197-227m deep at two sites located in the green spaces surrounding the buildings. In the closed system, water circulates through borehole probes absorbing heat from the ground and then through a central network of pipes in each tower block to reach the apartments where it is heated up further in the individual apartments. Each flat received a small-size and quiet so-called “Shoebox” heat pump fitting into a cupboard and a hot water cylinder.
Benefits for tenants and Enfield Council
On the one hand, the use of individual heat pumps minimises heat losses as water in the heating grid circulates at lower temperatures before reaching the flats. On the other hand, it gives residents more control over their expenses as they only pay for the heating and hot water they actually use adding to flexibility and comfort.
It was expected that tenants could reduce their energy bills by 30-50%, however after the system had started operation, bills were reduced even further from an average £800 to an average £250 per tenant and year. Calculated over the 40 years system lifetime, savings add up to a total of £9 million.
The project was commissioned by Enfield Council and received support by the now closed Non-Domestic Renewable Heat Incentive through which businesses, public sector, and non-profit organisations were able to receive regular payments over 20 years based on the amount of renewable heat generated. The scheme supplies a 20-year income of £4.3 million to Enfield Council. Additionally, the Council benefits from improved Energy Performance Certificate (EPC) ratings for the property after the retrofit.
Summary
Type of GHP: Kensa Shoebox Ground Source Heat Pump
Capacity: 3kW | 6kW MWh per year
Date commissioned: 2017/2018
Service(s) provided: Space heating / domestic hot water
Depth: 197-227m
CO2 savings: 773t CO₂ per year
Energy use savings: 30-68%