GEA heat pump system installed at Bunhill 2 Energy Centre, Islington, central London. (Photo: Islington Council)

DUESSELDORF, Germany, 8 December 2020: The Bunhill Heat and Power Network project, in central London, uses waste heat from the London Underground network to supply heat and hot water to 1,350 homes, a school and two leisure centres in Islington, as part of Islington Borough Council’s efforts to reduce carbon emissions and achieve CO₂ neutrality by 2030.

GEA, in partnership with the main contractor, Colloide Engineering Systems, supplied a purpose-built heat pump solution for the project. The Bunhill 2 Energy Centre, GEA said, represents a real blueprint for the use of waste heat from public facilities, taking advantage of state-of-the-art technology on the site of the former City Road London Underground station, which was decommissioned nearly 100 years ago. The remains of the station, GEA said, have now been converted into a massive underground air extraction system that draws warm air from the tunnels underneath, still used by the London Underground’s Northern Line.

In close cooperation with Islington Council, Transport for London and Colloide, GEA installed a 1000 kW ammonia heat pump, housed within a container at street level. The heat pump, GEA said, extracts the energy from warm exhaust air from the underground tunnels. The slightly cooler air is vented to the ambient, and the rest is harnessed as energy and used to heat-up water through the heat pump, which is then pumped through a 1.5-kilometre network of district heating pipes, which provide heating to various buildings in the neighbourhood.

Exterior of Bunhill 2 Energy Centre, Islington, central London. (Photo: Islington Council)

GEA said the heat pump system it developed and manufactured consists of a combined evaporator/separator, three compressors and four heat exchangers in the heating circuit. The heat exchangers, GEA said, optimise the heating circuit according to criteria based on the return of heating water at 55 degrees Celsius and the supply up to 80 degrees C.

A key challenge in finalising the system design was the extensive testing required to ensure that any dust or dirt sucked into the ventilation air would not clog the heat exchanger coil, GEA said.

“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,” said Kenneth Hoffmann, Product Manager for Heat Pumps, GEA Refrigeration Technologies. “In the very unlikely event of a small amount of the natural refrigerant, ammonia escaping into the plant room, 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. The use of heat pumps is much more environmentally friendly than the use of gas boilers, especially in big cities, as they do not emit nitrogen oxides (NOx). Heat pumps, therefore, lead to cleaner air in cities and pay off financially. Moreover, ammonia is a natural refrigerant that does not contribute to global warming.”

Kenneth Hoffmann (left) and Iain Eckett (right) at Bunhill 2 Energy Centre, Islington, central London

Paddy McGuinness, Managing Director, Colloide Engineering Systems, said: “Colloide has been involved in several renewable energy projects. We partnered with GEA on this project, given their knowledge of ammonia refrigeration and heat pump technology. Based on GEA’s experience, 95% of the industrial refrigeration plants installed over the last 10 years have been ammonia based. Increased pressure to reduce energy bills for end users is driving a lot of  interest in ammonia heat pumps.”

According to GEA, the Bunhill 2 Energy Centre now connects an additional 550 homes and a primary school to the existing Bunhill Heat and Power district heating network, launched by the Islington Council in 2012. The heating costs for residents connected to the network will be cut by 10%, when compared to other existing communal heating systems, which themselves cost around half as much as standalone systems for heating individual homes, GEA said. The new system is a win-win for the environment and for the residents of Islington and aligns with the Council’s aim to end fuel poverty, GEA added.

The heating system is particularly environmentally friendly, as it reuses heat that would otherwise be wasted, GEA said. Supplying the connected households and public facilities with the upgraded waste heat will help to reduce CO₂ emissions in the Islington Borough by around 500 tons per year, GEA said.

“Thanks to the cooperation of all involved, this is a ground-breaking district heating scheme,” said Shaun Hannon, Contracts Manager, Colloide. “The main technology used is the ammonia heat pump, and as a result, this project provides cheaper, greener energy for the local community.”

Iain Eckett, Technical Sales Manager, Refrigeration Technologies, GEA UK, said: “This was a very ambitious task. But, we have shown that GEA has the knowledge, the technology and the ability to successfully implement innovative projects to generate cleaner and cheaper heating. We offer the most efficient solution at an attractive price.”

The principle of heat recovery using heat pumps can be applied in London and in underground networks all around the world, GEA said, adding that London alone has more than 150 ventilation shafts, where waste heat could potentially be recovered.

Project data
Start: 2017
Completion: 2019

Opening: 2020
Gross internal floor area: 617m²
Contract: JCT Design and Build Contract
Architects: Cullinan Studio (design),McGurk Chartered Architects (delivery)
Client and project manager: Islington Borough Council
Key delivery partner: Transport for London
Structural engineer: Ramboll (design), McMahon Associates (delivery)
M&E Consultant: Ramboll
QS: Gleeds
Landscape consultant: J&L Gibbons
CDM Coordinator: AECOM
Approved building inspector: Islington Building Control
Design and build contractor: Colloide Engineering
Artist: Toby Paterson
Heat pump system: GEA (design, manufacture, and installation)
Testing and Commissioning: Topic Plan
Project consultant: Inner Circle Consulting
Rights of light: Right of Light Consulting
CAD software: MicroStation, Revit

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