*Article* **Power and Energy Rating Considerations in Integration of Flow Battery with Solar PV and Residential Load**

**Purnima Parmeshwarappa, Ravendra Gundlapalli and Sreenivas Jayanti \***

DST-Solar Energy Harnessing Center, Department of Chemical Engineering, IIT Madras, Chennai 60036, India; purnimagp@gmail.com (P.P.); ravendra.gundlapalli@gmail.com (R.G.) **\*** Correspondence: sjayanti@iitm.ac.in; Tel.: +91-44-2257-4168

**Abstract:** Integration of renewable energy sources such as solar photovoltaic (PV) generation with variable power demand systems like residential electricity consumption requires the use of a high efficiency electrical energy system such as a battery. In the present study, such integration has been studied using vanadium redox flow battery (VRFB) as the energy storage system with specific focus on the sizing of the power and energy storage capacities of the system components. Experiments have been carried out with a seven-day simulated solar insolation and residential load characteristics using a 1 kW VRFB stack and variable amounts of electrolyte volume. Several scenarios have been simulated using power and energy scale factors. Battery response, in terms of its power, state of charge and efficiency, has been monitored in each run. Results show that the stack power rating should be based on peak charging characteristics while the volume of electrolyte should be based on the expected daily energy discharge through the battery. The PV source itself should be sized at about 25% more energy rating than the average daily load. The ability to design a VRFB with a high power-to-energy ratio makes it particularly attractive for PV-load integration.

**Keywords:** solar photovoltaic energy; redox flow battery; residential load; renewable energy integration; battery sizing; battery efficiency
