Design of a Hybrid Geothermal and Concentrated Solar Power System with Thermal Storage

Abstract The Olkaria IV geothermal site in Kenya serves as the focal point for this investigation into a hybrid renewable energy configuration that couples geothermal generation with concentrated solar power (CSP) and thermal energy storage (TES). A well-documented limitation of geothermal plants is the progressive decline of reservoir output attributable to declining reservoir pressure, temperature, and flow rates, with degradation estimates approximating 0.7% annually. CSP integration offers a thermal compensation mechanism that mitigates this decline while TES enables the system to deliver dispatchable electricity on demand. The economic performance of the proposed hybrid system was assessed through four principal indicators: LCOE, NPV, IRR, and payback period, evaluated over a 25-year project lifespan. Site-specific simulation data informed the analysis, coupled with sensitivity testing across a range of financial and environmental assumptions. The hybrid configuration requires an upfront capital investment of $886,990,336, yet produces 1,467,525,376 kWh in its first operational year. On the financial side, a real LCOE of 12.23 ¢/kWh and a real levelized PPA price of 22.01 ¢/kWh underpin a project NPV of $1,766,798,208, with an IRR of 29.81% attained at year 20. Taken together, the evidence establishes that geothermal-CSP hybridization is both technically sound and economically justified, positioning it as a credible contributor to Kenya's renewable energy expansion and national grid reinforcement goals.