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.

The goal of the proposed research is to develop two in-situ sensor systems that measure in-ground gas concentrations and strain/moisture/temperature/suction at different scales in order to provide data on the dynamics of gas flux and soil structure. One is based on distributed fiber optic sensor (DFOS) system that can provide measurements at meters to kilometers-scale, whereas the other is based on low-power sensor coupled with in-ground mesh-network wireless sensor network (WSN) system that provides data at selected local points in distributed manner. Both technologies are currently being prototyped at UC Berkeley (UCB). The developed sensor systems will be trialed first in the unique wind tunnel-soil experimental facility available at the Colorado School of Mines (CSM). We propose an experimental plan designed to manipulate soil moisture fluctuations by balancing subsurface water introduction through precipitation events and losses to evaporation and evapotranspiration as controlled by atmospheric perturbations (temperature, wind speed, and relative humidity) so as to make more informed biogeochemical predictions and soil structure changes under changing climate conditions. Under the controlled environment, we will quantify the precision errors of the developed sensor systems. The developed systems will also be implemented in the fields of Rothamsted Research (RR) to examine its feasibility in the actual field conditions. The ultimate goal is to improve the predictive understanding of how atmospheric carbon loading is affected by soil structure changes. The proposed sensor development and experimental research will lead to a substantial improvement of soil carbon models such as the RothC model developed at RR]. Each compartment in the model decomposes by a first-order process with its own characteristic rate. The IOM compartment is resistant to decomposition. The model adjusts for soil texture and its changes by altering the partitioning between CO2 evolved and (BIO+HUM) formed during decomposition, rather than by using a rate modifying factor, such as that used for temperature. Moreover, total CO2 effluxes are largely controlled by root respiration, and microbial respiration of soil organic matter including rhizospheric organic carbon and all of these processes are highly sensitive to soil structure. In this proposed research, we therefore hypothesize that soil structure change is strongly linked to soil gas generation. We will develop and implement sensor systems that measure both, which in turn will allow us to quantify the link. These new models will in the future allow the effects of soil management on carbon dynamics to be predicted and hence give an understanding of the impact of different soil management strategies (e.g. tillage) on soil sustainability. The research will complement ongoing field research at RR supported by the BBSRC in the National Capability scheme and in ISP funding streams; especially on the delivery of nutrients to plants. The processes to be studied in the project are expected to lead to improved formulations to include multi-scale, multi-physics under development at RR by: (1) more rationally representing the coupled surface-subsurface processes, (2) including vegetation hydrodynamics and carbon and nutrient allocation, and (3) incorporating soil and genome-enabled subsurface reactive transport models that have explicit and dynamic microbial representation. The project will lead to the development of spatially-distributed sensing systems in the field that can (1) sense changes in soil stricture and (2) link these changes to fluxes of N2O, CH4, CO2 and O2 into and from soils.

This transformative research fellowship will advance electrochemical carbon dioxide capture as a greenhouse gas mitigation technology. To limit global warming to 1.5C and avoid catastrophic climate change we must greatly reduce our emissions of greenhouse gases. To this end the UK has recently committed to net zero greenhouse gas emissions by the year 2050. Carbon dioxide capture and storage (CCS) is a critical technology that must be deployed at scale if the UK is to meet this goal. CCS is a process where carbon dioxide is first captured at point sources (industrial processes, fossil fuel power) or directly from the atmosphere, before subsequently being stored underground. State of the art CCS technology uses amine molecules to absorb carbon dioxide. Subsequently a large amount of energy must be supplied in the form of heat (or a vacuum) to regenerate the amines and release pure carbon dioxide for storage, thereby increasing the cost of CCS. The amine process also suffers from (i) limited carbon dioxide capacities, (ii) amine evaporation into the atmosphere and (iii) amine degradation in the presence of oxygen and other contaminant gases. This programme will explore the use of electricity to capture and release carbon dioxide as a more energy-efficient method of CCS that can overcome the limitations of amines. In electrochemical carbon dioxide capture, the charging of an energy storage device such as a battery or a supercapacitor causes the selective absorption of carbon dioxide. When the device is discharged, pure carbon dioxide is released (for subsequent storage), and much of the energy supplied during charging is recovered. Initial work suggests that this technology may be more energy-efficient than existing approaches, and there is still vast room for improvement, especially if the molecular mechanisms of capture can be understood and manipulated. We will (i) advance the understanding of electrochemical carbon dioxide capture and (ii) discover new materials and devices that capture carbon dioxide more efficiently. Specifically we will focus on electrochemical carbon dioxide capture by (i) supercapacitors and (ii) batteries. We will measure the amount of carbon dioxide that can be captured by these devices and we will vary the structures of the materials used to guide their improvement. A proper understanding of the molecular mechanism of electrochemical carbon dioxide capture may lead to breakthroughs for this technology. A key thrust of the programme is therefore mechanistic studies of the molecular-level capture mechanism. We will use a suite of experimental techniques to study the chemical structures of the electrode materials, and we will correlate these structures with their carbon capture properties. We will develop nuclear magnetic resonance studies that allow the molecular form of the bound carbon dioxide to be determined at different stages of the capture process. Our mechanistic studies will inform the design and synthesis of improved materials for electrochemical carbon dioxide capture. We will synthesise the next generation of materials with (i) larger carbon dioxide uptake capacities, (ii) lower energy requirements for regeneration and (iii) faster uptake rates. New technology generated by this work will be prototyped and developed into new products. The developed technology will generate clean economic growth and will help the UK meet its 2050 net-zero emissions target. The research background of ACF combined with the assembled team of partners and excellent institutional support will lead to new knowledge and technology that will make the UK world-leading in electrochemical carbon dioxide capture.