Waste heat from the Tube is converted to supply heating and hot water to more than 1,350 homes, a school and two leisure centres by Cullinan Studio’s new energy centre on Old Street in north London
The Bunhill 2 Energy Centre is intended to provide a wider urban blueprint for reducing heating bills and carbon emissions while improving air quality and making the capital more self-sufficient in energy.
It is sited in the long-disused CIty Road Underground station, which has been transformed to house a 2m-diameter underground fan to extract warm air during winter months from the Northern Line tunnels below.
The warm air is 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 is increased to about 80°C using heat pumps and transferred via heat exchangers to communal heating system loops on housing estates. The heating bills for council tenants connected to the network will be cut by about 10 per cent compared with other communal heating systems.
12 bunhill2 ©paulraftery
Source: Paul Rafferty
The fan can operate in reverse to supply cooler air to the Tube tunnels during summer months.
The energy centre enables the addition of 550 homes and Moreland Primary School to Islington’s existing Bunhill Heat and Power district heating network, launched in 2012. The network already supplies heat to two local leisure centres – Ironmonger Row Baths and Finsbury Leisure Centre – and more than 800 homes, with the potential to supply up to 2,200 homes in the future.
The centre’s combined heat and power technology also generates electricity, which can be fed into the London Underground network and an adjacent tower block, powering its communal lighting and lifts.
Islington Council commissioned Scottish artist Toby Paterson to create an artwork featuring cast aluminium reliefs, which is wrapped around the building.
The project is a collaboration between Islington Council, Transport for London and the Mayor of London. It was funded by Islington Council, which owns and runs the network, and a grant from the European Union’s CELSIUS project. City Hall funded the early feasibility work for the project.
20 bunhill2 ©paulraftery
Source: Paul Rafferty
The design of Bunhill 2 ‘celebrates the necessary’. The project team explored how a new language of civic industrial architecture could begin to define this new typology of heat networks, just as Joseph Bazalgette had revolutionised the design of the public water systems in the 19th century and Sir Giles Gilbert Scott celebrated the design of the utilitarian phone box in the 20th century.
This small, neglected, but prominent site at a junction on City Road was full of disparate clutter, including the forlorn ventilation shaft of the former City Road Underground station, smothered in advertising hoardings and fly-postings, a shabby brick substation and left-over patches of space between. Signs, lamp posts, CCTV cameras etc milled around the site in a chaotic fashion and all was dwarfed by the surrounding towers. It also had many physical constraints, including below-ground voids, the need to maintain access to the shaft and substation, and proximity to adjacent dwellings.
Consulting extensively with the local community, planners and local councillors, Cullinan Studio’s approach was to organise the new elements with the existing features to create a well-composed assembly of prefabricated structures, clad in attractive materials and set in an enhanced landscape.
Key moves were made to minimise the visual and environmental impact on adjacent residents and using principles of good urban design. The architecture was composed to echo existing building lines, strengthen street edges and redefine the street corner.
A palette of robust materials was selected to be resistant to graffiti, knocks and scratches, with lustrous black glazed brick and charcoal vitreous enamel steel panels for the ground level, selected for their association with the site’s transport heritage and commonly found on London Underground. Cullinan Studio worked with artist Toby Paterson, whose cast aluminium relief panels tesselate across the base and provide his contextual response to the local community.
The rich, dark, copper-coloured metal cladding to the upper storeys accommodates a perforation pattern that ebbs and flows in response to the varying degrees of ventilation required for the equipment behind, providing dynamism and transparency to the façade. Growing in scale as they rise up the energy centre, they evoke the invisible networks below ground, whether these be pipes for district heating, underground tube lines or thermal air currents.
Cullinan Studio was approached by Islington Council in 2014 to design Bunhill Energy 2 Centre following its completion of energy centres for the Universities of Warwick and St Andrews.
Cullinan Studio is now working on an InnovateUK-funded research project GreenSCIES to implement the next generation of power and heat generation from waste heat in a partnership led by Islington Council and London South Bank University.
Alex Abbey, project director, Cullinan Studio
Bunhill phase2 network ©ramboll
The Bunhill district heating scheme is a revolutionary example of how linking waste heat resources to existing buildings and new high-density developments, using district heating, can provide low carbon and affordable heat alternatives. The Greater London Authority estimates there is enough heat wasted in London to meet 38 per cent of the city’s heating demand. With the expansion of district heating networks this could rise to 63 per cent of demand by 2050.
When Ramboll was appointed by Islington, it had already built the first phase of the Bunhill heat network, delivering efficient heating to 850 homes through a gas combined heat and power scheme at Bunhill Energy Centre 1, but wanted to do more, and was asked to find out how to supply heat to an additional 500 dwellings in north London using low-grade waste heat from the London Underground. Our ground-breaking study confirmed that Islington Council could in fact extend the district heating network to 1,350 homes by adding an innovative low-carbon heat source.
The proposed low-carbon heat source was a London Underground ventilation shaft, located on City Road, where 18-28°C air is exhausted to the atmosphere from a long-abandoned tube station (City Road, between Old Street and Angel), now part of the Northern Line tunnel ventilation system. Ramboll’s feasibility study confirmed that this source of waste heat could be exploited by heat pumps, which would capture the waste heat and upgrade it to approximately 80°C, as opposed to the original design temperature of 95°C.
Islington Council wanted the scheme to supply the cheapest, greenest heat possible, so the heat pump design temperature was lowered further to 70°C to increase the system’s efficiency. Ramboll investigated 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. Our investigations proved the heat pump concept was financially and technically viable.
Another design innovation was to incorporate two smaller gas-fired CHP engines which, as well as providing heat, also supply electricity directly to the heat pump when the power from the grid is most expensive, helping reduce the cost of the heat. Funding for this innovative feature was supplemented by a grant from the GLA. A second thermal store also enhances system technical and economic performance.
On completion of the feasibility study, Ramboll was appointed to act as the Owner’s Engineer on the project. This role involved developing the design of the complete system to enable planning permission to be obtained and for it to be tendered.
As part of the design development, discussions were held with LUL with respect to the size and function of the fan serving their ventilation shaft and how heating and cooling solutions can be integrated, resulting in further environmental savings. These discussions resulted in them upgrading the fan’s capacity and enabling it to be reversed, opening up the potential for the district heating scheme to supply cooler air during warmer weather.
Lucy Padfield, district heating director, Ramboll
Ground floor plan ©mcgurkcharteredarchitects
Source: McGurk Architects
This project was conceived to help address two key priorities for the council: cutting carbon emissions in the borough – further underlined by the climate emergency it declared last year – and helping reduce our residents’ energy bills at a time when the cost of living is soaring.
We wanted to expand the original Bunhill district heat network and, at the same time, lead the way in the progressive, innovative and ambitious use of technology to benefit hundreds more residents and improve our environment.
Bunhill 2 does just that; capturing heat from an industrial source that would otherwise be wasted, and using it to heat homes in a cheaper, greener, more sustainable way. It also proves that the technology is viable and replicable in urban settings across the world.
The centre contributes to a network providing cheaper energy to more than 1,350 households, a primary school and two leisure centres, with a projected saving of 500 tonnes of CO2 per year. That is equivalent to taking 340 cars off the road annually, which will help the council towards achieving its aim of being a net zero-carbon borough by 2030.
Karen Agbabiaka, head of public realm, highways, energy and operational facilities, Islington Council
City road elevation©cullinanstudio
Source: Cullinan Studio
Start on site 2016, 2017 (Energy Centre construction)
Completion December 2019
Gross internal floor area The GFA of the entire building (including LUL staircase, LUL head house structure and UKPN sub-station) is 614.7sq m
Form of contract or procurement route JCT/Design and Build
Construction cost Undisclosed
Design architect Cullinan Studio
Delivery architect McGurk Chartered Architects
Client and lead partner Islington Council
Key delivery partner Transport for London
Structural engineer Ramboll (design), McMahon Associates (delivery)
M&E consultant Ramboll
Landscape consultant J&L Gibbons
Project manager Islington Council
CDM co-ordinator AECOM
Approved building inspector Islington Building Control
Design and build contractor Colloide Engineering
Artist (artwork panels) Toby Paterson
Design, manufacture and installation of new heat pump system GEA
Testing and Commissioning assurance Topic Plan
Project consultants Inner Circle Consulting (worked alongside Islington’s internal team to strengthen project leadership and enhance internal capacity)
Rights of light Right Of Light Consulting
CAD software used MicroStation, Revit