Tube's heat loss becomes neighbourhood's – and London's – energy gain

 

Bunhill 2 Energy Centre
Islington, London
Cullinan Studio with McGurk Architects

Bunhill 2 Energy Centre is an unusual MacEwen Award commendation because there isn’t much to see or witness. From across the road, the building appears as a five storey, carmine red box that someone forgot to put windows in. Its architecture for the common good is essentially invisible. You can’t go in, you won’t see community in action while you are there. Maybe you’ll see nobody at all. 

But look more closely and the building is effectively a delicate decorative Moorish metalwork envelope for a mass of pipework and technology. It is about connecting and servicing an undetectable local network of buildings and homes with heating. The common good element stems from the fact that the energy it provides is recycled unwanted heat from the Tube (remember that?), which makes it more sustainable and cheaper for a wide demo­graphic of residents. In summer the energy centre operates in reverse by providing natural cooling to the Tube.

Located on a peninsular corner plot, it is dwarfed by towers of 1960s council flats and by the even taller cluster of luxury residential skyscrapers that have crept out along City Road from the City of London towards Angel in recent years,  massively expanding the energy demand in the area.

Bunhill 2 is the culmination of a pioneering and unique collaboration between Islington Borough Council and Transport for London. They were brought together by a third party, the Mayor of London’s office, an aspect of the project which makes it particularly ‘MacEwen’ from the outset – and a factor that impressed judge Sue Stringfellow for its inherent difficulty in even putting together coherent funding applications. It is the first known scheme in the world to take waste heat from an under­ground rail network and use it to provide lower cost, greener heating and cooling by adding 550 homes and a primary school to the existing Bunhill district heating network, currently serving 800 homes and two leisure centres in Islington. This will reduce residents’ energy bills, which have risen significantly over recent years, but also plays an important role in Islington council’s zero carbon commitment by reducing annual CO₂ emissions by about 500 tonnes, as well as in the wider goals of improving air quality in the capital and making it more self-sufficient.

The project began with a feasibility study by Ramboll to confirm that the heat pump concept was financially and technically viable. Ramboll then acted as client engineer developing its design. TfL upgraded its City Road mid-tunnel ventilation system to enable the capture and utilisation of waste heat. London South Bank University analysed the real-life performance of the scheme, evaluating its benefits and identifying how best it could be applied.

In this context, Islington council challenged the architect Cullinan Studio, whose office is nearby, to create a new energy centre that would inspire and intrigue, as well as transform a site that was an unsightly cluster of leftovers from City Road Tube station on the City and South London railway (it became the Northern Line) which closed in 1922. The resulting design explores how a new language of civic industrial architecture could begin to define this new typology of heat networks, just as Sir Giles Gilbert Scott celebrated the design of the utilitarian phone box in the 20th century.

The site is now a well-composed assembly of prefabricated structures that echo the existing building lines and strengthen the street edges by redefining the corner. The cladding system is made of recycled aluminium, cast aluminium from waste sources and low carbon mild steel coated in vitreous enamel. Cut-out patterns to the upper storeys ebb and flow in response to the varying degrees of ventilation required for the equipment behind. Designed to be demountable in sections, it allows for the replacement of entire containerised plant assemblies. Artwork panels by Toby Paterson tessellate across the base, providing a contextual response to the local community. The materials are high quality, recyclable and robust, chosen for their association with the site’s transport heritage and as appropriate for the tough urban context.

 

MacEwen judge Hugh Pearman says: ‘The project is logically perfect, using waste heat from a train network for a district heating system. Cullinan Studio did design and community consultation. It’s on a prominent location in Clerkenwell with a filigree facade. It makes a virtue out of mesh. It also looks like the follies in Parc de la Villette by Tschumi – an interesting object in the cityscape.’

While some judges questioned its social impact, Kathy MacEwen felt its sustainability was the big social benefit in itself. Tumpa Fellows comments: ‘This stood out for me. It is a great example of how you can make things aesthetically pleasing even when you’re dealing with climate change and its social impacts. It’s quirky, interesting and makes me want to know more.’

The project also demonstrates so much potential and could be infinitely replicated across London. The GLA estimates there is enough heat wasted in London to meet 38% of the city’s heating demand. The expansion of district heating networks could achieve 63% of demand by 2050. The project is ground-breaking by providing a blueprint for decarbonising heat in London and around the world, and a deserving MacEwen commended winner. 

---

IN NUMBERS
614.2m² 
total floor area
£16.3m
project cost