Techno-economic assessment and investment conditions for a hybrid small hydropower–rooftop solar photovoltaic system in Ghana

Abstract

Attaining Sustainable Development Goal 7 (SDG7) requires reliable and affordable electricity, yet Sub-Saharan Africa continues to face persistent challenges of access, cost and supply reliability. In Ghana, thermal plants supply about 68% of generation, sustaining high tariffs and greenhouse-gas emissions despite abundant renewable resources. This study asks when an integrated small hydropower–solar photovoltaic (SHP–PV) hybrid system is the preferred investment over standalone rooftop PV, using Asantekrom in Ghana’s Tano River Basin as a planning-level case study. A flow-duration-curve assessment with an environmental-flow allowance indicates that a 4.4 MW run-of-river plant would deliver about 22.4 GWh/year at a capacity factor of approximately 0.59, consistent with peer-reviewed estimates for the basin. A GIS-based survey of 102 rooftops supports a 2.6 MWp photovoltaic system generating about 5.06 GWh/year, and the two resources are seasonally complementary (monthly correlation r = −0.59). At the current bulk-supply tariff of GHS 0.921/kWh, standalone rooftop PV is the superior investment (NPV GHS 18.7 million, LCOE GHS 0.50/kWh), while the hybrid is viable but inferior (NPV GHS 15.8 million, IRR 11.2%) because the loss-making hydropower component destroys GHS 2.9 million in value. Because the capacity factor derives from a regionalised monthly flow series and is best treated as an upper bound, this ranking is conditional: the hybrid overtakes PV only if the realised capacity factor exceeds about 0.60, above a tariff crossover of about GHS 0.94/kWh, or under development-finance lending terms near 8%. Scenarios added for February grid-firming costs, alternative turbine design discharges and locally observed PV degradation rates (0.5–1.5% per year) leave this ranking unchanged. A complete one-month hydropower shutdown in February is identified as a critical operational risk. The study contributes a documented, site-specific framework that quantifies when hybridisation adds value, providing evidence-based guidance for investment sequencing in Ghana’s electricity sector.