Power generation by means of regenerative solar-Rankine plants

In the present paper an original approach to the use of concentrated solar-thermal technology has been carried on for electric power generation, based on the application of Rankine cycles in Mediterranean areas. In particular, solar energy has been thought as an auxiliary thermal source to face the regenerative part of the thermal cycle (feed water pre-heating), so obtaining major thermodynamic advantages together with an important reduction of pollution. Concerning the solar plant main components, parabolic trough collectors have been taken into consideration using diathermic oil as intermediate operating fluid, as they are widely utilized today in solar power generation due to their well known reliability (i.e.: mirrors, receivers, photo selective coatings, materials, etc..). A thermodynamic and economical analysis have been provided to estimate the efficiencies and the unit costs of producing energy by different typologies of hybrid power plants, compared to conventional ones working with methane gas. The solar energy aid has shown an undisputable thermal efficiency improvement, so reducing fossil fuel consumption and the primary cause of air pollution. Regarding the energy cost, some case-studies have shown competitiveness with respect to conventional plant only if social external costs are unavoidably considered, due to the effects of pollutant emissions (first of all, CO2 emissions) to the environment.