Modelling of groundwater flow and heat transport

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Courtesy of ESI Ltd - Environment Specialists

Client: Transport for London

Location: London

Services: Groundwater Modelling

Issues: Identifying the potential effects of pumping excess heat to the Chalk aquifer

Summary: ESI was commissioned to test the feasibility of one of the possible solutions identified to prevent temperatures on the deepest parts of the London Underground network rising to unacceptable levels. ESI developed a series of groundwater models of open loop ground source heat pumps in Greater London to identify the impact of pumping excess heat into groundwater.

As part of its £10bn Investment Programme, Transport for London (TfL) is investing over £150m in reducing summer heat on the Tube.  One potential technique to reduce summer platform temperatures is by pumping the excess heat into groundwater.  TfL is investing £150m of its £10 billion programme to address the issue of heat on the Tube.  Getting heat out of the London Underground (LU) network is a huge engineering challenge.  TfL has established a dedicated programme team to provide solutions to prevent temperatures on the deepest parts of the network rising to unacceptable levels.  ESI is supporting Parsons Brinckerhoff in exploring the potential effects that this scheme will have on the Chalk aquifer beneath London. 

ESI has developed a series of groundwater models of open loop ground source heat pumps in Greater London.  The purpose of the models was to simulate the effect the ground source heat pump schemes might have on groundwater temperatures and to identify potential interferences between neighbouring schemes.

The transport of heat within the aquifer was initially modelled using an adapted version of MODFLOW and MT3D.  To account for potential temperature effects on groundwater flow and the influence of the unsaturated zone on heat conduction, the models were also developed in the finite element code FEFLOW.  Results from the different numerical codes were compared to increase the understanding of the influence of the mathematical methods on the calculated solutions and intensive sensitivity analyses were carried out to account for the uncertainty inherent in the aquifer characteristics and thermal properties applied in the models.

The results from the models have been used to inform the design process and the selection of different technologies at particular sites.  As the project moves towards implementation, the models will be used to design and assess investigations at each site.

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