Optimized design of a hybrid renewable energy system with biogas energy storage for sustainable rural electrification: A case study in Sempu, East Java, Indonesia

Rural electrification in remote regions is constrained by low population density, challenging terrain, and the high cost of grid extension. Although hybrid renewable energy systems (HRES) have been widely proposed, most remain heavily dependent on battery storage, which is an expensive energy storage. This study develops and optimizes an HRES integrating solar photovoltaics (PV), wind, geothermal, and biomass (animal manure), with biogas-based storage replacing conventional batteries. Key contributions of the paper include the introduction of a systematic approach for optimal HRES design, identification of the breakeven point between HRES and grid extension, and evaluation of biogas against battery storage based on cost and environmental considerations. A case study in Sempu Village, East Java, approximately 1650 residents in 2024, was analyzed to minimize lifetime cost, eliminate unmet loads, and reduce emissions. Among 15 studied HRES configurations, the optimal system includes a 24 kW PV array, a 138 kW biogas generator, and a 29 kW converter, resulting in a Net Present Cost (NPC) of $309,767 and a Levelized Cost of Energy (LCOE) of $0.14/kWh. Scenario-based sensitivity analysis using Shared Socioeconomic Pathways (SSPs) until 2050 confirmed long-term cost-effectiveness and scalability. Biogas storage proved more cost-efficient than batteries, despite slightly higher emissions. The breakeven grid extension distance was estimated at 2.6 km. This study demonstrates that optimized HRES can provide sustainable, affordable, and resilient electrification for remote communities.