CMMI-EPSRC: Modeling and Monitoring of Urban Underground Climate Change

Overview
In dense urban areas, the underground is exploited for a variety of purposes, including transport, additional residential/commercial spaces, storage, and industrial processes. With the rise in urban populations and significant improvements in construction technologies, the number of subsurface structures is expected to grow in the next decade, leading to subsurface congestion. Recently emerging data indicate a significant impact of underground construction on subsurface temperature and there is extensive evidence of underground temperature rise at the local scale. Although it is well known that urbanization coupled with climate change is amplifying the urban heat island effect above ground, the extent of the underground climate change at the city scale is unknown because of (i) limited work on modeling the historical and future underground climate change at large scale and (ii) very limited long-term underground temperature monitoring. The hypothesis of this research is that (a) the high ground temperature around tunnels and underground basements, b) the observed temperature increase within the aquifer, and (c) inefficiency in ventilation of the underground railway networks, necessitate more detailed and reliable knowledge of urban underground thermal status. The project will develop a framework for monitoring and predicting temperature and groundwater distributions at high resolutions in the presence of underground heat sources and sinks. This can be achieved via a combination of numerical modelling, continuous temperature and groundwater monitoring and statistical analyses. The ultimate goal is for every city to generate reliable maps of underground climate, with the ability to understand the influence of future urbanization scenarios.

Merit
The objective of this joint NSF-EPSRC research is to advance understanding of the impacts of the urban underground on subsurface temperature increase at the city-scale. A low cost and reliable underground weather station using the fiber optic sensing technologies will be developed and installed at sites in London and San Francisco. A high-performance computing based thermo-hydro coupled underground climate change code will be developed to simulate the temperature and groundwater variation with time at the whole city scale. The main scientific deliverable from the district- and city-scale numerical simulations and the experimental temperature monitoring is a series of archetype emulators, which are defined based on the geological characteristics, above ground built environment, such as surface and buildings types, and the density and type of the underground structures. These archetype emulators will allow efficient city-scale modelling and enable application of the methodology to any other city or region with similar characteristics of above and underground built environment. This new knowledge will make possible to consider precise thermal conditions around underground structures in urban areas as well as facilitate efficient utilization of geothermal resources for both heating and cooling purposes.

Broader Impacts
Uneven spatial distribution of excess heat in the subsurface can be viewed as analogous to the urban heat island effect above ground. With correct planning, subsurface temperatures can be harnessed beneficially. However, if unchecked, they can result in a high environmental and economic costs. The combination of specially packaged monitoring equipment and open-source underground climate model can provide a robust framework to assess underground conditions and evaluate future evolution and potential impacts. Cities, local and state governments, agencies, utilities, as well as citizens, will be able to access these tools to make more informed decisions, avoid environmentally unsustainable practices, and extract value more fairly. In the long term, awareness of the health status of the underground is a step towards sharing responsibility for its sustainable and fair use. In the short term, the underground weather stations will provide data to assess the underground climate conditions over time. The outreach strategy is focused on engaging with the wider community and the profession to raise awareness of the issues and provide tools to explore solutions. The early career researchers will benefit from the international exposure of this US-UK collaborative project. The team has been successful in recruiting students from under-represented groups in engineering and mentoring of PhDs and postdocs towards successful academic careers.