Techno-economic analysis of an innovative purely solar driven combined cycle system based on packed bed TES technology

The present work performs a techno-economic analysis of a purely solar driven combined cycle composed of a solar air receiver directly connected to a topping gas turbine coupled to a bottoming packed bed thermal energy storage at the gas turbine exhaust, which runs in parallel to a bottoming steam cycle. Capacity factor, capital expenditure, and Levelised Cost of Electricity have been considered to assess the plant performance. A sensitivity analysis has been performed in order to understand the influence of solar multiple, energy storage capacity and gas turbine expansion ratio over the plant key performance indicators. The results show that the studied solar driven combined cycle is more costly than conventional ones, and therefore it leads to higher Levelized Cost of Electricity. However, it enables a complete reduction of CO2 emissions and increased flexibility in the system with the help of the introduction of an intermediate packed bed thermal energy storage. Furthermore, large solar multiple, medium storage capacity and complete expansion ratio through the gas turbine enable enhanced system performance. Finally, further works including optimized dispatch algorithms could enable a proper evaluation of the economic profit given by the flexibility offered by the storage unit and by a potential control of the Brayton cycle recuperation level in the modified plant layouts.