The article examines the introduction of solar-combi systems in large-size sports facilities. The examined solar-combi systems consist of solar collectors, a biomass heater and thermal storage tanks. In a sense, they constitute hybrid thermal power plants. The full mathematical background is presented on the operation of such systems, along with a proposed operation algorithm, aiming at the maximization of the captured solar radiation. A case study is implemented for the coverage of the thermal energy needs for hot water production and swimming pools heating, met in the Pancretan Stadium, Crete, Greece. In this way, the article aims to indicate the technical and economic prerequisites that can guarantee the feasibility of the examined systems, highlighting the significant potential contribution of such systems towards the realization of energy transition plans from fossil fuels to renewables. The economic feasibility of the introduced system is based on the avoiding diesel oil and electricity procurement cost, consumed for the coverage of the thermal energy demands under consideration. The optimum dimensioning of the examined case study results to an annual thermal energy demand coverage balance of 55% by the solar collectors and 45% by the biomass heater, giving a payback period of 5-6 years.
