A comprehensive power management strategy for the effective sizing of a PV hybrid renewable energy system with battery and H2 storage

Abstract

In the present work a detailed Power Management Strategy (PMS) of a Photovoltaic Hybrid Renewable Energy System (PV-HRES) with battery, H₂ storage/re-electrification, and diesel generator (DG) back-up has been developed. The PV-HRES was regarded to employ commercial PV modules, battery cells, and power electronics, as well as commercial alkaline electrolyzer (EL) and PEM fuel cell (FC), both regarded to variably operate following the fluctuations of PV-power excesses/shortages. The scope was to demonstrate the operability of the PMS and to utilize the PMS for the rational sizing of the PV array, the batteries' bank and the hydrogen storage capacity, for a given load and a solar irradiation annual profile. The annual operation of the PV-HRES was simulated for 440 combinations of PV-arrays and battery/H₂ storage capacities, with constant EL and FC capacity, aiming for: (i) exclusively renewable power generation, (ii) rational PV-array sizing and (iii) annually balanced H₂ generation/consumption. The operation algorithm was based upon the battery's State of Energy (SOE) variation between 20 and 95 % of their nominal energy capacity (B_NEC). Below 20 %, the PV-energy deficits were covered by the FC, in case of sufficient stored H₂, whereas beyond 95 %, energy excesses were converted to H₂, in case of H₂ storage volume availability. Increased PV-arrays and batteries led to the exhaustion of H₂ storage volume and to significant dumped renewable energy waste (up to 23 % of the PV generation), whereas decreased PVs and battery capacities led to H₂ exhaustion, throughout the annual operation. Out of the 440 examined combinations, 40 were found to simultaneously: i) nullify the DG generation, for exclusively renewable energy generation, ii) prevent both battery and H₂ storage volume exhaustion, thus eliminating excessive energy wastes and rationalizing the PV-array size, and iii) balancing the annual hydrogen generation/consumption. To fulfill the 1.48 kW average load demand, the analysis pointed out an optimum PV-HRES of 10.23 kWp nominal PV power, 120 kWh battery storage capacity, and 4 m³ H₂ storage volume, at 100 bars maximum pressure; for which the annual PV generation exceeded by 25.8 % the annual load demand.