The recent revival of urban living in the UK has been stimulated by many different factors, including life style choices and government policies. This has led to a rapid increase in the number of apartments in the UK cities. This increased density living has also brought about various changes in the city infrastructure, including the way energy is supplied to residential buildings. The recent trend of ‘electrification of heat’ represents one of these changes, whereby electricity rather than natural gas is now typically being used for space and water heating as well as for cooking. Further growth in electricity demand has been predicted in the governments Carbon Plan with the increased use of all-electric systems including heat pumps for domestic heat. This will in turn impact the environment since electricity supplied in the UK is predominantly based on fossil fuels and contributes to significant greenhouse gas (GHG) and other emissions. However, greater penetration of renewable sources in the future would be expected to reduce GHGs. This would also help to improve the security of supply through diversification of energy sources. On the other hand, there are concerns that increasing reliance on electricity could lead to fuel poverty for a greater section of society. Thus, it is not immediately clear whether the change from gas to electricity would contribute to the sustainability or otherwise of energy supply in the UK residential sector. Therefore, this research has set out to understand better the implications of the electrification of heat in the urban residential sector by examining the trade-offs between environmental impacts, techno-economic costs and social aspects. This work therefore goes beyond the previous research that has typically focused solely on GHG emissions and energy pay-back times of different energy options. This is also the first time as far as the author is aware that the sustainability of the electrification of heat in cities are analysed in depth. Various tools have been used for these purposes, including life cycle assessment (LCA), indoor air quality monitoring (IAQ), life cycle costing (LCC), social surveys (SS), scenario analysis (SA) and multi-criteria decision analysis (MCDA).Assuming all sustainability aspects considered here to be equally important, the most sustainable option is the district heating system. All-electric heat-providing systems (electric panel, electric storage, and air source heat pumps) have on average 2.5 times higher environmental impacts than gas-based systems (individual gas boiler, solar thermal and gas, district heating and community CHP systems). The techno-economic costs of all-electric systems are 80% that of the district heating system – however, fuel cost and demand changes increase substantially all-electric system cost vulnerability. Gas-based systems are widely accepted and valued - all-electric systems while a ‘good fit’ for particular city homes - have greater social impacts including affordability. If the proposed decarbonisation of electricity generation is realised, the global warming potential from electric heat-providing systems could be reduced to a 1/10th of present emission levels by 2050 increasing electrification of heat sustainability. Therefore, the choice of the most sustainable heat-providing options in the future, including that of the ‘electrification of heat’, will depend on the extent of the decarbonisation of the UK electricity supply and the relative importance placed on sustainability impacts by different stakeholders.

L'introduction des énergies renouvelables intermittentes, la mise en place d'une réglementation thermique qui baisse les besoins de chauffage d'un facteur 5 à 10, entraîne une re-conception des moyens de chauffage intégrant efficacité énergétique et effacement d'équipements domestiques lors des heures de pointe. Cette thèse comporte l'étude et la conception d'une PAC intégrant un stockage thermique par chaleur latente dans son condenseur. Ce stock permettra un effacement d'au moins deux heures. Les besoins d'une maison basse consommation (BBC) ont été évalués ainsi que la quantité de chaleur à stocker afin d'assurer cet effacement. Une étude sur le phénomène de changement de phase et les MCP a été menée afin de sélectionner un matériau adapté à cette application. Le phénomène de changement de phase a été modélisé en régime dynamique. Quatre matériaux candidats ont été sélectionnés et analysés par colorimétrie différentielle (DSC) avec ajustement par méthode inverse. Plusieurs structures de l'échangeur stockeur ont été proposées, simulées et optimisées et deux ont été choisies et réalisées. Les deux échangeurs réalisés ont été testés seuls et intégrés dans un système de PAC. La dernière génération a donné des résultats très encourageants pour le développement d'une PAC à stockage efficace. Finalement, l'apport de stockage a été évalué en termes d'efficacité énergétique et d'émissions de CO2. Cette PAC présente une amélioration potentielle du COP saisonnier de 20 à 30 % comparativement à des PAC air/eau et air/air du fait de la gestion intelligente du stockage/déstockage d'énergie en faisant fonctionner la PAC pendant les heures les plus favorables de la journée et en évitant les cycles courts de fonctionnement correspondant aux besoins thermiques faibles. / The introduction of intermittent renewable energies, the implementation of a thermal regulation, which decreases heating needs of a factor between 5 and 10, causes a redesign of heating systems integrating energy efficiency and the cut-off of domestic equipments during peak hours. This thesis involves the study and design of a heat pump incorporating a latent thermal storage in its condenser. This storage will allow a cut-off during at least two hours. The heating needs of a low-energy consumption house (BBC) have been estimated as well as the heat amount to be stored so as to ensure such a cut-off. A study on the phase-change phenomenon and the PCM has been carried out in order to select suitable materials for this application. A dynamic model of the phase change was also developed. Four candidate materials were selected and analyzed by tuned Differential Scaning Calorimetry (DSC) with adjustment by the inverse method. Several storing-exchanger structures have been proposed, simulated, and optimized; two of them have been realized. Both heat exchangers have been tested alone and then integrated into a heat pump system. The final generation gave very promising results for the development of an efficient heat pump with storage. Finally, the heat storage effect has been evaluated in terms of energy efficiency and CO2 emissions. This heat pump presents potential improvement of the seasonal COP between 20% and 30% compared to air-to-water and air-to-air heat pumps because of the smart monitoring of the energy storage/delivery due to the heat pump operation during the most favorable hours of the day and by avoiding short cycles operation corresponding to low heating needs.