Bunhill 2 Energy Centre

The Bunhill 2 Energy Centre, situated on the long-disused site of the old City Road underground station in Islington, is the second phase of Islington Borough Council’s Bunhill Heat and Power District Heating Network, launched in 2012. The innovative project uses waste heat from the Tube to provide sustainable, cheap heating and hot water to homes and other buildings in the borough. A JCT Design and Build Contract provided the contract solution.

The Bunhill Heat and Power District Heating Network was supplying heating and hot water to 800 homes and two leisure centres, Ironmonger Row Baths and Finsbury Leisure Centre. The completion of the Bunhill 2 Energy Centre enables the addition of a further 550 homes and Moreland Primary School. The combined total of 1,350 homes, two leisure centres and a school has the potential to upgrade to 2,200 homes in future.

Islington Borough Council’s aims for the Network were to supply the cheapest, greenest heat possible, in order to cut overall emissions in the borough, and reduce residents’ energy bills at a time when living costs are on the rise. The Bunhill 2 Energy Centre achieves this by capturing heat from an industrial source that would otherwise be wasted and uses it to heat homes in a way that is cheaper and more sustainable.

The Greater London Authority estimates there is enough wasted heat in London to meet 38 per cent of the city’s heating demand. By expanding district heating networks such as Bunhill this could rise to 63 per cent of demand by 2050.

In choosing the site of the Centre, it was determined that 18-28ºC air was being exhausted into the atmosphere from the London Underground ventilation shaft located on City Road – now part of the Northern Line ventilation system – but once the shaft of the former City Road underground station. The Centre uses a 2m diameter fan underground to extract the warm air from the shaft below. The warm air is then used to heat water, which is pumped to buildings in the neighbourhood through a new 1.5km network of insulated underground pipes. The water temperature can be increased to 80ºC (although it is set at 70ºC to increase efficiency) using heat pumps and then transferred via heat exchangers to communal heating system loops on housing estates. Heating bills for council tenants connected to the network will be cut by 10 per cent compared with other communal heating systems.

The Centre’s combined heat and power technology also generates electricity – which is fed into the London Underground network and an adjacent tower block, powering its communal lighting and lifts.

The project includes a number of energy and cost-saving innovations. One includes the installation of two smaller gas-fired CHP engines. These provide both heat and supply electricity directly to the heat pump when the power from the grid is at its most expensive, which helps reduce the overall cost of the heat. Secondly, discussions with London Underground in establishing the size and function of the fan serving the ventilation system, resulted in a solution to integrate the heating and cooling functions and the fan was upgraded to enable it to be reversed to supply cooler air to the tube during the warmer weather.

In terms of the site itself, whilst it was small and neglected, it was in a prominent position on a City Road junction. This meant there were many physical constraints during construction, including below-ground voids, the need to maintain access to the shaft, and proximity to adjacent buildings.

Consultations were carried out with local community, planners, and local councillors to develop a design that included combining new elements with existing features and creating a set of prefabricated structures, attractively clad and set in enhanced landscape. It was also important to minimise the visual and environmental impact on adjacent residents, echo existing building lines, but take the opportunity to strengthen street edges and redefine the street corner.

Robust materials were chosen to resist graffiti and surface damage, including black glazed bricks and charcoal vitreous enamel steel panels at ground level. These materials were chosen for their visual association with similar materials used on the underground. Scottish artist, Toby Paterson, was commissioned by Islington Borough Council to create cast aluminium relief panels that tessellate across the base. They are designed to celebrate the often overlooked and undervalued everyday infrastructure that defines many Londoners’ lives.

Rich, dark, copper-coloured metal clads the upper stories. Its perforated pattern ebbs and flows in response to the varying degrees of ventilation required for the equipment behind – providing dynamism and transparency to the façade. The semi-transparent façade gives a clue to the invisible network below ground.

The Islington Council-led scheme included collaborations with Transport for London and the Mayor of London, along with a number of other key contractors and specialists.

As a key partner in the scheme, TfL upgraded its City Road mid-tunnel ventilation system to enable the capture of waste heat from the Northern Line tunnels. TfL is carrying out further research to identify opportunities for similar projects across the tube network as part of its Energy and Carbon Strategy. The Mayor of London brought together Islington Council and TfL to form the partnership that has delivered the project. City Hall also funded the early feasibility work and coordinated London’s overall involvement in the CELCIUS project. CELCIUS is an EU funded project that provided funding for the Centre as part of a wider project exploring low carbon innovation in heat networks in European cities, including Cologne, Genoa, Gothenburg and Rotterdam.

Cullinan Studio was responsible for the architectural concept design, and carrying out the consultation with local community, planners, and local councillors to secure planning permission. McGurk Architects were then appointed to take the design through to completion. Ramboll was appointed client’s engineer and contract administrator, developing the design of the system. Ramboll carried out the feasibility studies to determine that the heat pump concept was financially and technically viable. This involved investigating the impact of lower temperatures for the connected buildings’ heating and domestic hot water loads to ensure demands could be met, and end user comfort wasn’t compromised. Colloide Engineering were the design and build contractors for the project and GEA provided the design, manufacture, and installation of the heat pump system.

The JCT Design and Build Contract is the natural choice for a complex, multi-faceted project, involving close collaboration among a number of clients, client partners and specialists. It is especially relevant where responsibility for different elements of the design is split. It enables all parties to the contract to have a solid contractual under-pinning in order to capture the complexity of the works and the various responsibilities.

Whilst Islington Borough Council’s aim was to produce cleaner, greener energy for its residents, the Bunhill 2 Energy Centre goes further by providing a wider urban blueprint for reducing heating bills and CO2 emissions while improving air quality and making London more self-sufficient in energy. Its projected saving of 500 tonnes of CO2 per year – equivalent to taking 340 cars off the road annually, helps the council achieve its aim of net-zero carbon by 2030 and proves that the technology is viable and replicable in urban areas around the world.

Project data
Start: 2017
Completion: 2019
Gross Internal Floor Area: 617m²
Contract: JCT Design and Build Contract
Architect: Cullinan Studio (design)
McGurk Chartered Architects (delivery)
Client and project manager: Islington Borough Council
Key Delivery Partner: TfL
Structural Engineer: Ramboll (design), McMahon Associates (delivery)
M&E Consultant: Ramboll
QS: Gleeds
Landscape Consultants: J&L Gibbons
CDM Co-ordinator: 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 consultants: Inner Circle Consulting
Rights of Light: Right of Light Consulting
CAD Software: MicroStation, Revit