Contact Ida Shafagh (I.Shafagh@leeds.ac.uk) Employer University of Leeds State/Province England (United Kingdom) Title Research Fellow in Geothermal Systems Modelling (Part-time) Employment Dates Nov. 2017 — Jun. 2019 Duration 75% (1 year, 3 months) Tasks and Duties I worked as a key member of European Union Horizon 2020 GeoTech heating and cooling project. My contribution was to develop design tools for integration of borehole U-tubes and foundation heat exchangers into heatpump and chiller installations throughout the EU and UK.
Diaphragm wall foundations adapted for use as ground heat exchangers are an attractive proposition to achieve low-carbon heating and cooling with heat pumps in larger non-domestic buildings. As the extent of a diaphragm wall installation is driven by geotechnical questions and the number of storeys, key system design considerations are the peak and seasonal capacity of the ground heat exchanger and the proportion of the building demands that can be satisfied. Dynamic simulations of prototypical office buildings in a range of climatic conditions have been used to analyse heat exchange potentials using a Dynamic Thermal Network (DTN) heat exchanger model. Systematic evaluations of the time-dependent heat fluxes between three boundaries (heat exchanger, basement, ground surface) have been made to maximize heat exchange potentials and overall system efficiency given temperature constraints over 20 years operation. This has allowed maximum heat exchange potentials to be evaluated for a range of design parameters and climates to enable preliminary design of diaphragm wall heat exchanger systems and assessment of hybridized solutions. Considering short timescale dynamic effects suggests peak heat exchange rates higher than previously reported. In some climates seasonal operation is found to be constrained by temperature limits according to ground thermal properties.
Reference: Peterson EL and Shafagh I (2022). Evaluation of diaphragm wall heat exchanger potential. .Published in Energy and Buildings. Representative Projects in collaboration with HiRef, Gruenholland, University of Bolognia, and others I worked closely with Dr Ida Shafagh in a shared office to parametrically implement her OpenFOAM analysis of screen wall heat exchangers in TRNSYS models. I managed a campaign of simulations and analysis that resulted in practical guidelines for the exploitation of structural foundations as geothermal heating and cooling heat exchangers.
Given a heat-exchanger module developed by University of Leeds Building Physics Professor Simon Rees and a library of Dynamic Thermal Network (DTN) files generated by Dr Ida Shafagh I designed and developed a TRNSYS model of hydronic heating and cooling of building with diaphragm wall heat exchangers integrated into the basement carpark retaining walls. I also provided means for hybrid switching between the ground source and an auxiliary air-source heat exchanger with forced convection. I implemented systematic hourly simulations of a building heating and cooling loads as well as geoexchange performance for 20 years using ASHRAE IWEC weather data. I methodologically repeated simulations with increasing number of Geoexchange capacity to determine the threshold where air-source would not be required. I repeated such a process for a number of European cities representing warm Mediterranean and cool Oceanic climates to guideline the capacity of such foundation heat exchangers to support the heating and cooling of European office buildings. My work was repeated at each situation with a range of soil conductivities and at a range of pipework diameters, as well as two different basement foundation geometries. Consequently my work required more than one year of equivalent full time work. I also led the literature review, writing, formulation of guideline equations, design of control schemes, and international peer-reviewed defense required for publication. I acknowledge the foundational work of Dr Shafagh and Professor Rees in validation and publication of the DTN modelling methodology.