On modelling for domestic energy autonomy in the UK :understanding the role of traditional and novel technologies for small-scale hydrogen storage

The domestic sector is one of the largest consumers of energy in the UK. The poor energy performance of the existing housing stock within this sector has resulted in an ever-growing energy demand and an energy infrastructure that is struggling to cope. With an increasing drive towards decarbonisation comes the expansion of renewable generation across the UK, however with that comes the limitations of intermittency inherent in the technologies. Energy storage is considered as a solution to these limitations, though with this is the potential for redefining the UK’s energy regime. Decentralised generation, storage and consumption of energy is proposed as an alternative regime as the core theme of this thesis. A common type of British home (a pre-1920s Victorian end terrace building) has been modelled in the dynamic energy simulation software Designbuilder in order to explore how such buildings respond to decentralised energy management. The model was based upon a house of this type within the Energy House research facility at the University of Salford, constructed inside a climate controlled chamber and augmented with a photovoltaic installation. Intrinsic flaws in building modelling appear in the phenomenon known as the performance gap, which reduces the accuracy of models. The same flaws were found in the model created for this study. By applying a calibration procedure that replaced assumed performance parameters with those measured in-situ, the observed performance gap was reduced by a significant amount and therefore increasing the accuracy and predictive capacity of the model. The Energy House model was conditioned to reflect a variety of scenarios suited to the UK, including scenarios under the categories of archetype, occupancy, location, climate and level of retrofit. Each of these were identified as having a significant influence over energy consumption. Simulations under these scenarios revealed a high sensitivity to factors influencing the performance of the building’s envelope, with much less sensitivity to external influences and the building’s occupants themselves. A combination of best-case scenarios was found to deliver the greatest tendency towards energy autonomy, with a reduction of the grid demand by up to 70%. Trends identified in the modelling results indicated a need for energy storage to counter the offset between solar generation using photovoltaics and domestic consumption and the potential for closing the gap of energy autonomy. The home battery was considered as an established storage solution, while the use of hydrogen as an energy vector was also considered, with the established technology of compression and the novel technologies of absorption in metal hydrides and adsorption in activated carbon. A model for the battery in Designbuilder was conditioned to reflect a typical home battery, however additional models for hydrogen storage were scripted in Matlab. These models included bulk storage of hydrogen under pressure for the compressed gas and activated carbon solutions, whereas a finite element approach was modelled for the metal hydride solution. When comparing energy storage methods, simulations revealed that scenarios with variations to the average annual temperature had no impact on energy storage; in this case, as with the baseline model, the home battery outperformed other methods of storage. Under scenarios where modifications were made to the building’s envelope, compressed gas was found to be the most suitable candidate for storage. By combining the best-case scenarios from simulations, energy autonomy was virtually achievable, reducing the grid energy demand of a baseline model by 99.6%; both metal hydride and compressed gas storage solutions proved superior in providing this. This considerable reduction in domestic griddemand was only represented in a small number of homes in the UK however, with the benefits of integrated energy storage reserved for homes having high thermal performance, located at lower latitudes, and having lower occupancy densities. Despite the application of an autonomous decentralised energy regime being limited to a small proportion of the UK’s housing stock, this study realises the importance of energy storage in a future of renewables; it paves the way for further work in determining the role of small-scale energy storage as a solution to the challenges faced in the future of energy for the UK. This work found that for domestic energy autonomy to be achievable in the UK, it is first necessary to vastly improve the energy performance of the existing housing stock