Battery capacity planning for grid-connected solar photovoltaic systems

With the steady increase of grid-connected solar photovoltaic (PV) power generation in many parts of the world, management of solar generation intermittency becomes a key challenge for power system operators. A widely considered approach to addressing this issue is to install battery energy storages together with solar PV sources. This paper discusses the capacity planning when battery energy storage is used as a companion for grid-connected solar PV systems. We consider the concrete context of the National Electricity Market of Singapore (NEMS). For electricity markets like NEMS that adopt real-time bidding and clearance, we propose solutions that can enable a battery-companioned solar PV system to behave in the same way as traditional dispatchable generators. We observe that the battery capacity requirement can be reduced by shortening the cycle length for real-time bidding and clearance or by allowing occasional disconnection of solar PV units. To further reduce the battery capacity, we discuss the design of more flexible forms of contracts between the grid and the solar PV systems.