HEAT PUMP Upgrades Waste Heat From London Underground

As part of main contractor Colloide Engineering Systems partnered with key consulting engineers, suppliers and sub-contractors   team, GEA, a global technology specialist supplied a purpose-built heat pump solution for this flagship project. GEA, Colloide and all those involved are supporting Islington’s efforts to reduce carbon emissions with the aim of achieving CO₂ neutrality by 2030.

Islington Council and its net zero carbon target for 2030

Client and Project Manager, Islington Council is committed to reducing carbon emissions for many years and has declared a climate emergency. In the corresponding declaration, it committed itself to working towards a net zero target by 2030, i.e. to achieve CO₂ neutrality. To achieve this goal for the benefit of its citizens, Islington is taking steps to provide cheaper and more environmentally friendly energy.

One of these measures is the Bunhill 2 Energy Centre, the first of its kind in the world. It represents a real blueprint for the use of waste heat from public facilities, in the specific case of the London Underground. The new Burnhill 2 energy center uses state-of-the-art technology on the site of a London Underground station that has been decommissioned for almost 100 years. The remains of the station, have been converted into a huge underground air extraction system that draws warm air from the tunnels underneath. The tunnels are used by London Underground’s northern line.

By heating and supplying hot water for homes, a school and leisure centers in Islington, energy is saved, carbon emissions are reduced, air quality is improved, and heating costs for Islington’s residents benefiting from the scheme, are reduced.

GEA heat pump solution

The technology used is the ammonia heat pump. In close cooperation with Islington Council, Transport for London (TfL) and the main contractor Colloide Engineering Systems, GEA installed a 1000 kW ammonia heat pump in a container at street level. GEA and their ammonia heat pump certainly meet that criteria.”– Paddy McGuinness, Managing Director of Colloide Engineering Systems.

Heat pump developed and manufactured by GEA for the system consists of a combined evaporator/separator, 3 compressors and four heat exchangers in the heating circuit. The heat exchangers optimize the heating circuit according to criteria based on the return of heating water at 55⁰C and the supply up to 80⁰C.

The heat pump extracts the energy from warm exhaust air from the underground tunnels. The slightly cooler air is vented to the ambient and energy is used to heat up water by the heat pump, which  is pumped through a 1.5 km network of district heating pipes to the buildings in the neighborhood, where it is finally used to heat the buildings. According to Kenneth Hoffmann, Product Manager for Heat Pumps at GEA Refrigeration Technologies, there were many challenges in the design of the system during the project. These included extensive testing to ensure that dust and dirt sucked into the ventilation air would not clog the heat exchanger coil.

According to Kenneth Hoffmann, Product Manager for Heat Pumps at GEA Refrigeration Technologies, there were many challenges in the design of the system during the project. These included extensive testing to ensure that dust and dirt sucked into the ventilation air would not clog the heat exchanger coil. He explains, “Bunhill’s district heating network required hot water from the heat pump up to 80⁰C. We used two-stage reciprocating compressors, also known as “pistons”, to achieve a Coefficient of Performance (COP), or heat pump efficiency, of over 3.5. Since the project was located next to a residential building, the installation also included a scrubber technology to filter the ventilation air from the plant room.”

The aim is: the local residents would not be exposed to the ammonia in the air, as it would be absorbed in the scrubber before being vented to ambient. Usually, heat pumps do not emit nitrogen oxides (NO_x) and therefore lead to cleaner air in cities. Moreover, ammonia is a natural refrigerant that does not contribute to global warming.

Inspiring result

There lies a real benefit to the environment, to residents and to Islington. The heating system is particularly environmentally friendly as it reuses heat that would otherwise be wasted. Supplying the connected households and public facilities with the upgraded waste heat will help to reduce CO₂ emissions by around 500 tons per year.

London district heating project using GEA heat pumps, set to become global benchmark. The idea is unique and has the potential to become a global role model.