Among concentrating solar power technologies, solar tower power plants currently represent one of the most promising ones. Compared to parabolic trough configurations, tower systems enable considerable efficiency gains as higher concentration ratios can be achieved. Direct steam generation systems, in particular, eliminate the usage of heat transfer fluids allowing for the power block to be run at greater operating temperatures and therefore further increasing the thermal efficiency of the power cycle. On the other hand, the current state of the art of these systems does not comprise thermal energy storage. Although it has been shown that the integration of storage potentially enhances the economic viability and profitability of the plants, there are no currently available and techno-economically feasible storage integration options for the case of direct steam generation towers.

The lack of storage adds to the already existing variability of operating conditions that all concentrating power plants endure due to the fluctuating nature of the solar supply. This situation is more prominent for the case of direct steam generation systems; leading up to multiple start-ups during a 24h period if the weather conditions are not optimal. In the interest of improving the annual performance and competitiveness of direct steam generation concentrating solar power plants, it is desirable for the plant to achieve fast start-up times to harness the solar energy as soon as possible. The start-up speed of the whole plant is limited by the thermal inertia of certain key components, one of which is the steam turbine.

This paper studies the potential for power plant performance improvement through the increase of steam turbine flexibility at the time of start-up. The methodology consisted of performing sensitivity studies on the annual operation of a power plant while considering different scenarios of turbine operational modifications. For each study, the corresponding power plant performance indicators were evaluated and compared to the base case without modifications. It is shown that gains of up to 7% in total power plant electric output and reductions in turbine maintenance periods can be achieved as a result of the implemented operational improvements.