Integration of Solar Field into a Combined Cycle Power Plant for Fuel Saving in Insular Subtropical Climates

Abstract

The harmful environmental effects of fossil fuels and the variability in their prices are shifting attention away from conventional combined cycle power plants. Supply issues in islands are also a problem to be considered. The objective of this work is to evaluate the feasibility of integrating solar energy into a combined cycle power plant for fuel saving in insular subtropical climates. With this aim, a case study comprising a 93 MW combined cycle in Las Palmas de Gran Canaria (Spain) and the integration of solar energy in the gas upper cycle has been presented and analyzed with a thermodynamic model. The effects of incorporating solar heat before and after the cycle compressor were assessed, finding that injecting 35 MW of solar heat before the compressor resulted in savings of 49% of the original fuel consumption and an increase of 2% in the global cycle efficiency, but at the expense of reducing the net power delivered by 47%. On the other hand, incorporating the solar heat after the compression process resulted in an overall 16.2% increase in the cycle efficiency, while delivering the same net power as the original cycle and reducing fuel consumption in 22%. With the increase in the amount of solar heat added to the cycle, the difference between both options became greater, with the best option being injecting solar heat after the compressor. Estimations of the economic and environmental effects of the most suitable option are provided, resulting in potential overall savings of 7.14 million Euro per year and a yearly potential of 13.75 Mkg of CO2 emissions avoided. The results of this work are expected to contribute to improve energy supply problems by using a renewable energy source and reduce fuel imports, providing more energy stability and security to the inhabitants of islands with similar climates as Las Palmas.