A CSP plant using air as working fluid with a thermal storage section and an ORC-based energy recovery system

摘要

The increasing of global energy consumption and the use of non-programmable renewable energy sources require the use of conversion systems with a high level of flexibility. The reduction of fossil fuels is a need and calls for technologies based on renewable sources which provide continuity of production, even when the source is unavailable. Concentrated Solar Power (CSP) plants represent a valid alternative able to replace fossil fuels in a medium/long term as high thermal source, keeping conventional technologies for the energy conversion section: the possibility to have small-medium and large-scale power plants increases the plant flexibility and provides a valid contribution to the GHG reduction policies on a local and global scale. The paper is focused on an innovative Parabolic Trough CSP plant using air as working fluid, with the purpose of reaching an acceptable overall global efficiency of the conversion section, ensuring production continuity thanks to a Thermal Energy Storage section. The hybridization of the CSP plant with an auxiliary biomass plant improves the performances of the components of the conversion section keeping them at design conditions even in presence of the Sun energy variability during days and months. In order to make a yearly-based producible energy evaluation, a typical solar year in the South of Italy has been considered. The use of air as thermal fluid, the conversion cycle adopted (presented by the authors in previous studies) and the integration with the biomass conversion sections have invited to recover the thermal energy losses at medium and high temperature with conversion sections based on the use of Organic Rankine Cycle (ORC), significantly improving the overall plant performance and, therefore, profitability.