A new optimal sizing methodology of storage-less PV system for retrofitting existing diesel-based power generation system within mini-grids

Abstract

With the increasing threats caused by fossil fuels consumption, Hybrid Power Generation Systems (HPGS), which combine Renewable Energy Sources (RES) and conventional ones, are gaining an increasing interest as they ensure a sustainable and cost-effective way to electrify rural and remote areas namely via mini-grids. However, a detailed assessment of the technical challenges and economic factors involved by such integration is essential to optimally size those HPGS.This study aims to determine the optimal storage-less PV system capacity to retrofit, at low penetration level, existing large-scale multiunit diesel-based Power Generation System (PGS) regarding the lowest Levelized Cost of Electricity (LCOE). Since excessive cycling of large-size Diesel Gensets (DGs) is fuel-intensive and increases maintenance expenses, the proposed methodology is based on a period ahead DGs operating-scheduling algorithm. The paper assesses, thereby, the effect of this period ahead length on the annual values of cumulative number of DGs operating hours, DGs loading factor, number of DGs starts as well as total fuel consumption for both diesel-only and PV-diesel systems. These operational outputs are then introduced into the system economic modeling to calculate its LCOE for each value of the PV system capacity.Simulation results of the developed optimization methodology, using data of the existing diesel-based PGS supplying Tinelkoum village in the Great Algerian South and its realistic hourly load profile recorded during the whole year of 2019, reveal that the choice of the operating-scheduling period ahead is a trade-off between the fuel consumption and the total number of DGs starts. Also, technical constraint of minimum DGs loading factor is observed to be better met when the PV system is integrated. According to the present study, Tinelkoum diesel-only PGS can host an optimal storage-less PV capacity of 650 kWp to 750 kWp depending on the period ahead. The optimal PV system will, thus, share for 1 h, 4 h and 8 h periods ahead respectively 19.94%, 19.54% and 19.10% of the resulting PV-diesel HPGS annual energy balance allowing a cost-saving, compared to diesel-only system, of 13.32% (0.275 $/kWh vs. 0.317 $/kWh), 12.53% (0.282 $/kWh vs. 0.323 $/kWh) and 11.91% (0.288 $/kWh vs. 0.327 $/kWh) for the three periods ahead respectively. Finally, the influence of fuel price and PV investment cost on the optimal PV capacity and, thus, the LCOE of the resulting HPGS has been analyzed.As it highlights the propitious opportunities of harnessing the solar PV potential endowing the Great Algerian South localities, the present work will helpfully serve as a guideline for the ongoing hybridization projects of their exiting fossil fuels-based PGS and eventually similar cases elsewhere.