Ramboll has been commissioned by Islington Borough Council to design and deliver district heating to 1,350 homes plus community buildings in north London, using unwanted heat from the London Underground.
Producing first a detailed study into the feasibility of using heat from the London Underground to supply district heating, and subsequently overseeing procurement and delivery, Ramboll has been instrumental in bringing this highly innovative low-carbon solution to the people of Islington. The Northern Line, the oldest deep level line in the world will heat 21st century homes, offices and leisure centres. The project will be a European first of its kind.
As well as being financed by the London Borough of Islington, the award-winning Bunhill Heat and Power Network was partly funded by the EU CELSIUS Project, and is supported by other London project partners including the Greater London Authority and UK Power Networks. Our work on the extension of the Bunhill heating network project is split into 2 phases.
Stage 1 - Feasibility and scoping
Our brief from Islington Borough Council was to find out how to supply heat to an additional 500 dwellings in north London using waste low grade heat. Islington had already built the first phase of the Bunhill heat network, delivering efficient heating to 850 homes but wanted to do more. Our ground-breaking study confirmed that Islington could extend the district heating network to 1350 homes adding an innovative low-carbon heat source.
Extracting waste heat from ventilator shaft
The heat source would be a London Underground ventilation shaft located on City Road where 18-28 degrees Celsius air is exhausted to the atmosphere from a long abandoned tube station (City Rd, between Old Street and the Angel), now part of the Northern Line tunnel ventilation system. The feasibility study confirmed that this source of waste heat could be exploited by heat pumps, which can capture the waste heat and then upgrade it to approximately 80 degrees Celsius. This heat could then be fed directly into the district heating system.
Connecting the heat network to established housing stock
The study proved the viability of this heat pump concept both in terms of providing the supply of heat and matching it with the heat demands from the connected buildings (largely existing council housing and leisure centres built in the 1930-1980s). In particular the study explored the impact of supplying heat from the extended district heating system at a temperature of 80 degrees C as opposed to the original design temperature of 95 degrees C. This involved looking at the impact of lower hot water temperatures for both the connected buildings’ heating load and domestic hot water load. The study proved that this was financially and technically viable approach.
“We believe that the use of large-scale heat in this way connected to urban district heating systems will play a major part in decarbonising the UK’s heating energy demand”, says Crispin Matson, head of Ramboll’s Energy Systems department in the UK. “The use of heat pumps utilising industrial waste heat sources is more carbon efficient than gas-fired CHP, the usual source of heat for district energy schemes. I am convinced that with the increasing use of renewable power sources, large-scale heat pumps connected to district heating systems will play a major role in the future heating of cities in the UK”, he says.
Stage 2 - Delivering the Solution
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 in the summer of 2015.
As part of the design development, discussions were held with LUL with respect to the size and function of their fan serving their ventilation shaft. This resulted in them upgrading the fan’s capacity but also enabling it to be reversed, opening up the potential for the district heating scheme to supply cooler air during warmer weather.
District Heating equipment being delivered at Bunhill: Image Ramboll
Islington Council want the scheme to supply the cheapest, greenest heat possible, so another design innovation was to incorporate two smaller gas-fired CHP engines which, as well as providing heat, will also be used to 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.
Continuing innovation
All district heating works are now complete and work on the Energy Centre is well under way. The main heat generation equipment will be containerised and vertically stacked within the new structure, and clad in a striking, perforated anodised aluminium façade. Art work, in concrete and aluminium, reflecting the design of the connected social housing estates has also been commissioned to run around the façade at ground-level. The heat generation equipment has started to be delivered to site.
The heating network at Bunhill is one of the most innovative networks in the UK, extending what is possible using waste energy and making for a more liveable, more sustainable London. Islington borough council benefits from low cost heat, Northern Line passengers benefit from cooler tunnels, while London residents as a whole benefit from lower carbon emissions. It's estimated there is enough heat wasted in London to meet 38% of its heating demand. With the expansion of district heating networks this could rise to 63% of demand by 2050. Bunhill will be the first of many such projects.
