Cooling the London Underground to power Islington‚Äôs heating network
Transferring heat has the potential to reduce energy consumption and curtail carbon emissions
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Transferring heat has the potential to reduce energy consumption
The Metropolitan Integrated Cooling and Heating (MICAH) project, funded by Innovate UK looks into the feasibility of transferring waste heat from London Underground to Islington Borough Council‚Äôs district heating network.
The lead participant in the project consortium is the London Underground Ltd, whose network has expanded to 11 lines, and in 2016‚Äì17 carried 1.379 billion passengers, making it the world’s¬†11th busiest metro system. The 11 lines collectively handle approximately 4.8 million passengers a day. The London Underground (LU) team work alongside the London Borough of Islington (LBI), with academic and research expertise from London South Bank University (LSBU).
As part of an upgrade to London Underground‚Äôs network, additional heat will be produced by the increase in train frequency. Cooling of London‚Äôs underground system is needed to maintain the future underground environment at safe temperature levels. So to mitigate the rise in heat and reduce the risk or heat strain to passengers, a new cooling system is to be installed. An opportunity has been identified to utilise the heat exchanger at York Road to support the expansion of Islington Borough Council‚Äôs district heating network.
This feasibility study has been able to demonstrate that there are opportunities to utilise waste heat from London Underground‚Äôs¬† exchanger at York Road to provide heat to Islington Borough Council‚Äôs district heating network (DHN). Combining the two systems would reduce the energy required by both parties, resulting in a reduction in energy use and carbon emissions and a reduction in the ongoing cost of energy consumed.
To evaluate the benefits of the proposed approach, an energy, carbon and whole life costing calculator model was developed to estimate energy, carbon and cost savings for a range of configurations and operating conditions. An inter-seasonal analysis was also carried out to determine how the benefits vary during the year.
Reducing carbon emissions
The 2008 Climate Change Act commits the UK government to an 80% reduction in carbon emissions below 1990 levels by 2050. The UK government‚Äôs strategy for meeting these challenging targets includes the constructive use of currently wasted heat by recycling and transferring it to where it‚Äôs needed. Emissions from heating contribute approximately one third of the UK total of carbon emissions. Reports have suggested that 25% of London‚Äôs heating needs could be met from decentralised sources such as secondary waste heat by 2025 if the right innovations and technologies are utilised.
LU requires ventilation and cooling to ensure that the temperatures within the tunnels are maintained at a safe level. LBI have identified that a district heating network (DHN) is beneficial at a location which is situated in close proximity to the proposed LU cooling scheme. An opportunity was identified to integrate the two systems whilst addressing the waste heat issue and the Metropolitan Integrated Cooling and Heating (MICAH) project was started.
The objectives of this feasibility study were to investigate how best to match the seasonal and daily heating demand with the heat availability, to complete a technical feasibility report on the works required to integrate the systems and to establish the emission savings and business case for these works.
A cooling and waste heat recovery system is proposed to be installed at a ventilation site on the Piccadilly line. It is planned to provide 900 kW (3.07 MBTU/h) of cooling, with a corresponding amount of extracted waste heat being recovered and transported over distances of up to 350 m (1,148 feet) to a DHN. The DHN will then distribute the heat to a number of nearby social housing estates and a public swimming pool in the Caledonian Road area of London, which are owned and operated by Islington Borough Council. The heat will be transported using water pipes which will need to be routed through the roads between the LU site and the DHN.
A key output of the study was a model that can be used to assess the potential for heat recovery at the proposed site and different LU sites. The model offers the opportunity to evaluate a proposed site with the key system parameters (inputs). These inputs alongside information from suppliers and capital expenditure allows for determination of a cost and carbon saving. LU will be able to validate the model at a proposed waste heat scheme that is currently under construction.
Nicholas Boot-Handford, senior project manager at Transport for London, is part of the MICAH project team and comments:
‚ÄúMICAH has been a very insightful and successful project and has also been a vital step in informing what we can do next in the development of waste heat initiatives. Delivering MICAH results in significant cost savings which gives a positive Net Financial Effect over a 30 year business case life, depending on system configuration. This gives a payback period of between 20 and 31 years. The carbon savings are approximately 1000 tonnes and 1800 tonnes per annum, depending on system configuration.‚Äù
The study has highlighted a number of important next steps for the development of waste heat initiatives, mostly of a technical nature. The project team still face challenges in developing the commercial and legal understanding of waste heat, including asset ownership, demarcation of assets, asset redundancy and the ability to charge parties for waste heat as well as further system optimisations.
There is now and probably will be an ongoing investment in model development, so that greater cost and carbon saving accuracy can be achieved. System optimisation, including delivery temperature of the heat pump, flow and return temperatures of the DHN, and removal of CHP from configuration to help achieve Mayoral air quality targets are all part of the plan. Finally, the development of detailed pipework route design, LBI Energy Centre design and LUL ventilation asset are priorities for the next stage of project development, and the team hope that these will all be completed in the near future to enable the system to be viable.