Optimal Operation Planning of a Photovoltaic-Cogeneration-Battery Hybrid System

The Japanese government has set targets for increasing the contribution from renewable energy sources, such as wind power and photovoltaic (PV) generation. To increase renewable energy near the demand side, a microgrid that utilizes controllable prime movers such as gas engines to compensate fluctuating demand and output of renewable energy is proposed here. However, because such systems include high-capacity batteries that are expensive, they are considered not to be cost competitive. The battery capacity can be reduced if gas engines in the system can follow the output change in renewable energy and the load change to some degree. Here, we model the optimal operation planning of a hybrid system for the day ahead and model the economic dispatch control for that day. For the day-ahead operation planning, we used 30-minute demand data. Three different objective functions were compared: minimization of running cost, CO₂ emission, and primary energy consumption. Results revealed that the optimal operation pattern when cost minimization is the objective is similar to that when primary energy minimization is the objective. Finally, we conducted a sensitivity analysis of PV capacity on the optimal operation of the hybrid system, and found that the break-even initial cost of PV is 200,000 yen/kW.