Cooling and recovery of heat from

underground railway tunnels for district heating

Gareth DaviesSchool of the Built Environment and Architecture, London South Bank University

103 Borough Road, London SE1 0AA

Presented at CIBSE ASHRAE Technical Symposium, Loughborough University, UK, April 5-6, 2017

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Topics to be addressed

• Heat challenge and need for carbon saving

• Opportunities for waste heat recovery

• Case study of integrated cooling and waste heat recovery

- London Underground

• Benefits of waste heat recovery

• Conclusions

• Future work2

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Heat challenge for the UK and London

3

Climate Change Act (UK) - 80% reduction in carbon emissions by 2050

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How can challenge be met?

5 key areas identified:

1) Decarbonizing the grid

2) Industrial heat

3) Waste heat and heating networks

4) Heat in buildings

5) Grids and infrastructure

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Heating in London

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• Heat usage map indicates significant residential heat demand throughout London

• London Mayor reports on future heating strategy for London; plan to meet 25% of London’s heating needs from secondary waste heat sources by 2025

• Plan to greatly increase number and scale of district heating networks (DHNs) in London

• For map on right, yellow lines indicate existing heat networks and red lines indicate proposed heat networks

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Opportunities for waste heat recovery in London

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Heat Source Proximity to heat

demand

Available year

roundTypical source temperature

Power station

rejection35°C

Buildings 28°C

Industrial heat 35-70°C

Underground

Railways32°C

Electricity

substations50°C

Sewer heat

mining14-22°C

Data centres 35°C

Roads /

Car parks25°C

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Heat in London Underground (LU) tunnels

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LU tunnel air temperatures

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Underground Temp Vs Ambient Temp

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17

19

21

23

25

27

29

31

33

20 22 24 26 28 30 32 34

Underground temp

Am

bie

nt

tem

p

Tunnel air temperatures 5-10°C higher than ambient

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District heating networks

• London plans to build many low temperature heat networks –supply temperature e.g. 70°C (London Mayor report, 2013)

• Low temperature waste heat e.g. LU tunnel air, could be upgraded via heat pumps to contribute heat at this temperature

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• Currently supply only 2% of heat demand in UK by district heating

• UK government plans to substantially expand district heating networks making use of waste heat sources e.g. LU tunnel air

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LU ventilation shafts

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Recovery of waste heat from LU tunnels

11Cooling and heating e.g. summer Heating only e.g. winter

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Benefit of integrated cooling and heating

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Modes of operation for vapour compression systems:

1. CoPc= Qe/ W = 4/1 (cooling only mode i.e. refrigeration)

2. CoPh = Qc/ W = 5/1 (heating only mode i.e. standard heat pump)

3. CoPc+h = (Qc + Qe)/ W =9/1 (integrated cooling and heating mode)

• For current waste heat recovery application use modes 2 and 3 only:

• Extract mode ≡ mode 2 (heating only mode)• Supply mode ≡ mode 3 (integrated cooling and heating mode)

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Renewable Heat Incentive (RHI)

13

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Project MICAH

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• Metropolitan Integrated Cooling And Heating – combined cooling and waste heat recovery

• A feasibility study funded by Innovate UK

• LU, Islington Council and LSBU

• Investigating costs and savings using a disused underground station

• Develop generic guidance/ evaluate benefits of LU waste heat recovery

• Other waste heat sources may also be used

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MICAH – site plan

15

300 m

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MICAH schematic

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MICAH project tasks

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• Project builds on previous LU/IBC studies i.e. delivery of heat to Bunhill DHN using heat pump, and recovery of waste heat from ventilation shaft at City Road station

Project tasks undertaken for MICAH include:

• Technical design of system (All partners)

• Surveys and constructability (LU)

• Modelling of system (LSBU/LU)

• Quantification of benefits (LSBU)

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MICAH model

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Inputs include details of:

- Ventilation shaft air and HRHX- Primary pumped water loop e.g.

temperatures, pressure drops and distance

- Heat pump heat exchangers and CoP- Secondary water loop e.g.

temperatures, pressure drops and distance

Outputs include:

- Predictions for energy use, carbon emissions and costs (i.e. OPEX) for MICAH

- Comparison with conventional heating e.g. CHP, gas boilers, and cooling using vapour compression system

- Calculated energy, carbon and cost savings for different MICAH operating conditions

• Model is spreadsheet based

• Uses relationships between the different input parameters to calculate the performance of the system for different operating conditions

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Comparison of conventional cooling and

heating energy inputs with MICAH

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Heating only mode (extract) Cooling and heating mode (supply)

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Comparison of conventional cooling and

heating carbon emissions with MICAH

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Heating only mode (extract) Cooling and heating mode (supply)

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Comparison of costs for MICAH with and

without RHI (heating mode only)

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Heating only mode (extract)(Operational costs without RHI)

Heating only mode (extract)(Operational costs with RHI)

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Benefits of waste heat recovery

22

Cooling application with waste heat recovery

• Reducing energy costsassociated with cooling

• Lower carbon emissions

• Shared equipment costs

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Conclusions

• There are many waste heat sources available, especially in cities

• Although waste heat is often of low temperature, it can be readily upgraded using heat pumps and reused

• Greatest energy, carbon and cost savings are achieved when cooling and heating are integrated

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Future work

• Further development of MICAH model and application at a range of LU sites

• Identification of the effects of seasonal temperature variation and cooling and heating demand profiles during the year and implications for MICAH

• Evaluation of potential for energy, carbon and cost savings for waste heat recovery from LU tunnels using MICAH, operating under different modes i.e. supply and extract

• Use MICAH model to optimise the waste heat recovery system

• Develop plan for development of a prototype system

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Bibliography

• Climate Change Act. 2008. (c.27). London: The Stationery Office, UK

• DECC. 2013. The Future of Heating: Meeting the Challenge, Department of Energy and Climate Change, UK

• London Plan, 2004. Mayor of London. The London Plan. Spatial Development Strategy for London. Greater London Authority, London, UK

• London’s Zero Carbon Energy Resource: Secondary Heat. Summary Report. 2013. Mayor of London Report, UK

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Project is being funded by Innovate UK, with support from Transport for London, Islington Borough Council, London South Bank University and i-STUTE (interdisciplinary centre for Storage Transformation and Upgrade of Thermal Energy), UK EPSRC project EP/K011847/1

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