Dynamic modelling of a low-concentration solar power plant: A control strategy to improve flexibility

• We built a transient model of both the solar field and the thermodynamic module.
• We performed simulations on five consecutive.
• We analyzed the influence of the concentration on the specific production per unit surface of collectors and occupied ground.
• A volumetric expansion device can limit the efficiency losses by variable speed operations.
• Warm-up and shut down influence is not negligible and a proper control system is needed.

This paper deals with a dynamic analysis on a low concentration solar power plants coupled with Organic Rankine Cycles (ORC), which can be an alternative to PV systems because of their capability of providing a smoother electricity production due to their thermal inertia. At least within certain restraints, moreover they are able to exploit diffused solar radiation.The dynamic model of a plant with static Compound Parabolic Collectors and an ORC system, using a rotary volumetric expander, was developed using the simulation tool AMESim. All the main components of the plant are modelled: solar collectors field, heat transfer fluid circuit, heat exchangers and the ORC system. The plant response to the radiation of different days was analyzed to quantify the daily production and the trend of various plant parameters. Real ambient conditions were employed for the simulations by using data obtained by historical series.The results showed that the employment of a volumetric expansion device with variable rotating speed allows the plant to operate at different radiations and ambient temperatures without the need of any storage system or external heat sources. Results can be extended to other applications, such as low temperature waste heat recovery or geothermal systems.