Since 2018 the trend has been for new Utility Scale solar projects to also include battery storage (BESS) systems. This is now used on almost all solar PV projects. This is because of these trends:
- Energy is most needed in the 4-8 pm time in the summer, when the solar is starting to turn off as the sun sets
- Because of the Duck curve the utilities need power in this off period and may curtail the solar in the middle of the day
- Most PPA RFOs are now asking for a bid for combined PV and BESS systems and give priority to those offers.
Costs are dropping significantly since 2018 and this costing chart from NREL in 2018 shows the component costs at that time for comparing the DC and AC coupled sytems.
Determining the optimum configuration of the combined BESS and PV system, especially with regard to determining when to charge and discharge the BESS system to the grid, is quite complicated and involves significant work to optimize.
Determining Price For Combined BESS and PV RFO Bid
At the present time it is difficult to achieve great financial rewards for these combined systems since the prevailing winning RFO bid for solar alone is in the sub $30/MWh range and battery costs are still somewhat high. The secret to any such combined bids that that the combined price adder for the storage will also produce a higher price from solar produced by the PV system alone. Still this is a challenging problem as we end 2020.