Techno-economic study of a concentrated solar thermal plant with sulphur as thermochemical energy storage for baseload power generation and sulphuric acid recycling

Abstract

A conceptual design and an economic analysis are presented for a thermochemical energy storage cycle of concentrated solar power which uses elemental sulphur as a storage medium. The thermochemical storage cycle is based on the splitting of sulphuric acid by high temperature solar heat. The heat for the process is provided by a centrifugal particle receiver. Diluted sulphuric acid (38 wt%), a waste product of the chemical industry, is regenerated inside the process. The storage medium sulphur is used in a sulphuric acid plant. Through burning the sulphur, the stored energy can be recuperated at a high temperature level and it can be used as a fuel in a highly efficient combined cycle power plant (gas turbine and steam turbine). Furthermore, high concentrated sulphuric acid (99 wt%, 2600 t/day) is produced as a valuable chemical commodity. The sulphuric acid plant produces 62 MW of electric baseload power, the efficiency (solar Irradiation to electricity) is in the range of 9 %. The price for the electricity generation depends strongly on the compensation price for the sulphuric acid recycling. For an estimated recycling price of 75 USD/t a minimum electricity generation price of 0.18 USD/kWh has been assessed. If in the future the recycling price for sulphuric acid increases to 140 USD/t, the baseload power generation with this process concept would be competitive without further financial funding.