Energy self-sufficiency, grid demand variability and consumer costs: Integrating solar PV, Stirling engine CHP and battery storage

Abstract

Global uptake of solar PV has risen significantly over the past four years, motivated by increased economic feasibility and the desire for electricity self-sufficiency. However, significant uptake of solar PV could cause grid balancing issues. A system comprising Stirling engine combined heat and power, solar PV and battery storage (SECHP–PV–battery) may further improve self-sufficiency, satisfying both heat and electricity demand as well as mitigating potential negative grid effects. This paper presents the results of a simulation of 30 households with different energy demand profiles using this system, in order to determine: the degree of household electricity self-sufficiency achieved; resultant grid demand profiles; and the consumer economic costs and benefits. The results indicate that, even though PV and SECHP collectively produced 30% more electricity than the average demand of 3300 kWh/yr, households still had to import 28% of their electricity demand from the grid with a 6 kWh battery. This work shows that SECHP is much more effective in increasing self-sufficiency than PV, with the households consuming on average 49% of electricity generated (not including battery contribution), compared to 28% for PV. The addition of a 6 kWh battery to PV and SECHP improves the grid demand profile by 28% in terms of grid demand ramp-up requirement and 40% for ramp-downs. However, the variability of the grid demand profile is still greater than for the conventional system comprising a standard gas boiler and electricity from the grid. These moderate improvements must be weighed against the consumer cost: with current incentives, the system is only financially beneficial for households with high electricity demand (>4300 kWh/yr). A capital grant of 24% of the installed cost of the whole micro-generation system is required to make the system financially viable for households with an average electricity demand (3300 kWh/yr).