Performance of actively controlled domestic heat storage devices in a smart grid

Abstract

Distributed, small-scale energy storage has been identified as a means of improving load factors for intermittent renewable generation and displacing the need for fossil-based backup. Domestic electric storage heaters operating within a smart grid offer high density, controllable energy storage at low cost, allowing the network operator to shift demand by charging heaters to dispose of excess supply. This paper reports monitoring outcomes and simulation studies on the first field trials of such a system, in which heaters are capable of responding to instructions from the grid to vary charging level at 15-min intervals, as well as to occupant-set controls on power output. Monitoring found significant unexpected out-of-schedule power draw and under-utilisation of storage capacity. Alternative approaches to scheduling were tested using simulations, and evaluated using metrics to quantify schedule following as well as other aspects of performance to give a balanced view of system performance to the network operator. Modern insulated storage heaters are capable of supporting load shifting for up to 48 h with minimal impact on room temperatures or demand, and with high confidence that charging schedules will be followed. However, where device controllers compete with centrally generated charge scheduling, the network will experience significant out-of-schedule power draw while occupants will experience either lower temperatures or increased cost.