Heat demand characterisation for heat pump retrofit

About the Project

Utilising heat pump technology is one of the main recognised solutions for transition to cleaner heat in the UK (DESNZ, 2023). By switching from natural gas boilers to electrical heat pump technologies, questions of performance (e.g., efficiency, comfort expectations, lifespan) are raised. Current practices associated with gas boiler driven heat systems undermine some of these performance issues. Oversizing of the gas boilers is, for example, a well noted practice (Bennett G, and Elwell C., 2020) that whilst having limited detrimental impact on these ’traditional’ heating systems, it can significantly undermine heat pump system performances. Therefore, a simple ‘like-for-like’ sizing of heat pumps during boiler replacement can lead to oversizing issues that would mean unnecessary financial investment, lower system efficiency and short cycling behaviours that reduce heat pump life expectancy. Correct sizing, through detailed examination of real heat demand, is a fundamental requirement for the success of transition from boilers to heat pumps.

Despite the availability of Energy Performance Certificates (EPCs), the estimated annual energy performance expressed in the EPCs cannot be used for sizing of the heating systems. The dynamics of heat demand must be understood so that a range of heat demand characteristics can be used to evaluate system options (e.g., peak load, heat storage potential, diurnal profile, etc.). This study aims to critically evaluate the application and robustness of existing heat demand estimation approaches and propose a roadmap for estimation of heat demand for replacement of gas boilers with heat pump technologies.

References:

DESNZ (2023). Heat Pump Investment Roadmap. The Department for Energy Security and Net Zero. London. Accessed, 05 October 2025.

Bennett G, Elwell C. (2020). Effect of boiler oversizing on efficiency: a dynamic simulation study. Building Services Engineering Research & Technology.;41(6):709-726.

University of Reading:

The University of Reading, located west of London, England, is ranked at 172 globally, according to the QS World University Rankings 2025. 98% of research at the University is of international standing (REF 2021, combining the University’s world leading, internationally excellent and internationally recognised submissions). The University’s main Whiteknights Campus is set in 130 hectares of beautiful, award-winning parkland, less than a 30-minute train ride to London Paddington and is approximately 30 miles from London Heathrow airport.

During your PhD at the University of Reading, you will expand your research knowledge and skills, receiving supervision and training in a number of different forms. We also provide dedicated training in important transferable skills that will support your career aspirations. If you need to develop your academic English skills before you start your studies, then the University has an excellent Global Academy which can help with this.

Eligibility:

• Applicants should have a good Bachelor's degree (minimum of a UK Upper Second (2.1) honours degree or equivalent) and preferably a Master’s degree in Engineering / Computing/ Applied Mathematics or a relevant discipline.
• Applicants will be judged on their academic experience, their understanding of the proposed research topic and their references. Experience in numerical modelling and knowledge of building services are essential. In addition, skills in programming and being familiar with Simulation tools such as EnergyPlus and TRNSYS are desirable.
• International applicants will also need to meet the University’s English Language requirements. We offer pre-sessional English courses that can help with meeting these requirements.

The University of Reading is committed to a policy of equal opportunities and non-discriminatory treatment for all members of its community.

How to apply:

Submit an application for a PhD in Energy and Environmental Engineering via our online application system.

Further information:

Construction Management and Engineering PhD webpage

Enquiries:

Dr Mehdi Shahrestani e-mail : m.shahrestani@reading.ac.uk

Funding Notes

We welcome applications from self-funded students worldwide for this project.

If you are applying to an international funding scheme, we encourage you to get in contact as we may be able to support you in your application.