Abstract
Combined heat and power (CHP) systems offer high energy efficiencies as they utilise both the electricity generated and any excess heat by co-suppling to local consumers. This work presents the potential of a combined heat and hydrogen (CHH) system, a solution where Proton exchange membrane (PEM) electrolysis systems producing hydrogen at 60–70% efficiency also co-supply the excess heat to local heat networks. This work investigates the method of capture and utilisation of the excess heat from electrolysis. The analysed system was able to capture 312 kW of thermal energy per MW of electricity and can deliver it as heated water at either 75 °C or 45 °C this appropriate for existing district heat networks and lower temperature heat networks respectively. This yields an overall CHH system efficiency of 94.6%. An economic analysis was conducted based on income generated through revenue sales of both hydrogen and heat, which resulted in a significant reduction in the Levelized Cost of Hydrogen.
Highlights
To meet net-zero emissions targets [1], the UK aims to increase the utilization of Renewable Energy Sources (RES)
This study has demonstrated the possibility of modelling combined heat and hydrogen (CHH) generator systems
The developed model is consistent with current commercial designs and provides the ability to scale the CHH generator to different sizes for a range of different applications
Summary
To meet net-zero emissions targets [1], the UK aims to increase the utilization of Renewable Energy Sources (RES). Hydrogen can be utilised across transport, industry, or heat, should electricity demand transcend supply, hydrogen can be converted back to electricity. Current figures estimate an excess renewable electricity generation of over 45GWh per year [4] equating to roughly £67million of lost revenue and useful energy [5]. This article analyses the potential opportunity of generating hydrogen through PEM electrolysis whilst harnessing excess heat produced and integrating it into district heating networks (DHNs) for domestic use. It brings forward the concept of a combined heat and green hydrogen (CHH) generator system – analogous with the widely deployed combined heat and power (CHP) generator system.
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