Design, sizing, and feasibility analysis of a hybrid renewable generation system for the self-sufficiency of an off-grid house

Abstract

Rural isolation from national electricity grids represents a persistent infrastructure challenge in Mediterranean mountainous regions, where isolated dwellings have traditionally depended on generators with prohibitive environmental and economic costs. This study proposes a modular engineering framework for the design and sizing of hybrid off-grid renewable generation systems, applied as a case study to a residential property in El Pla de La Llacuna (Villalonga, Valencia, Spain). The methodology develops a decoupled catalogue of four independent energy modules – solar photovoltaic (PV), micro-wind, geothermal, and electrochemical storage – each governed by strict technical boundary conditions that filter site suitability. The framework was applied through a multi-step process: resource characterisation using the PVGIS-SARAH3 database and hyper-local AVAMET meteorological data; load profile construction via a bottom-up appliance inventory; and iterative system sizing validated through computational simulation. Three energy supply scenarios were simulated and benchmarked against a 100% fossil-fuel baseline. The results demonstrate that a hybrid solar-wind configuration comprising 8 photovoltaic panels (4.28 kWp), 6 LiFePO4 batteries (28.8 kWh), and a 10 kW Vertical Axis Wind Turbine (VAWT) constitutes the optimal solution for this site, achieving total annual energy self-sufficiency with a capital expenditure of €12,328, a net present value (NPV) of €337,406, a return on investment (ROI – return on investment) of 34.07, and a payback period of 0.323 years. Geothermal exploitation was rejected due to geological and logistical constraints, while continuous wind generation was discarded as a primary source due to insufficient mean velocities, though transient gusts up to 73.4 km/h were successfully harvested as a winter supplementary resource.