Demand response via pre-cooling and solar pre-cooling: A review

Ever increasing numbers of air-conditioners and, in many places, more extreme weather and urban overheating are placing additional stresses on electricity networks globally, reflecting not only their high power draw but also highly correlated operation driven by weather conditions. The resulting peak demands can be considerably greater than average network flows requiring additional electricity generation and network capabilities for what might only be infrequent periods. Energy users must of course pay for this additional investment, including potentially via peak demand and time-of-use charges. Pre-cooling of buildings to spread air conditioning demand is one approach to reduce these peaks. Its potential contribution depends on the thermal performance of the building stock, particularly how long it can retain pre-cooled air, and patterns of weather on warm days. The use of solar energy, including particularly rooftop solar photovoltaics presents another possible option. Photovoltaics generates during daylight hours, which is well-matched with higher temperatures. However, photovoltaics generation may often be declining while heat loads in buildings and hence air conditioning are still climbing in the late afternoon. This suggests the potential of solar pre-cooling when solar photovoltaic electricity is used to run air conditioners in the pre-cooling phase. Literature reviews to date have tended to focus on only aspects of pre-cooling and solar pre-cooling, for example, the effect of thermal mass on the energy performance of buildings but not specifically on peak demand shifting and cost reduction. There is a particular gap with review papers that investigate pre-cooling and solar pre-cooling together with detailed characterization of their potential in different circumstances. The review presented here covers a wide range of state-of-the-art studies in the field of pre-cooling and solar pre-cooling covering the period 2014 to 2021. It also presents, for the first time, the necessary steps to design and implement pre-cooling and solar pre-cooling strategies. It is intended to support the growing research studies and practical implementations of pre-cooling and solar pre-cooling within the electricity sector.