The application of thermionics to concentrated solar power generation

Concentrated Solar Power (CSP) provides a promising solution to the generation of base load power using a renewable resource prevalent in Australia. This research commenced with a study through simulation of a CSP plant based on the ASTRI 110 MWe pilot design. From this analysis, high temperature topping cycles have been identified as a key avenue to increasing the performance of CSP. Thermionics has been selected as an ideal technology to fill this role, however it is noted that a robust model of thermionic conversion able to be applied and optimised for use in a CSP plant is lacking. In this thesis, such a model is developed; first in one dimensional and then two dimensional finite difference simulations. The results are compared with experimental data for a range of operating conditions with good consistency. The model has been used to analyse and improve thermionic performance through varied surface topologies in a novel study. Finally, results based on the thermionic simulation were integrated as a performance model into the thermal model of a CSP receiver. This was found to marginally increase the maximum receiver power density under high solar flux conditions from 0.623 MWt/m2 to 0.631 MWt/m2, compared to a benchmark case. In line with current advances in thermionic technology, a hypothetical case was considered in which conversion efficiency was doubled. In that case, the augmented receiver exhibited a maximum power density of 0.753 MWt/m2, a significant improvement over the current state of the art. Through this analysis, it has been concluded that the current technology does not provide sufficient benefit to a CSP receiver to justify the added complexity and cost that it introduces. However, avenues of development have been identified which, if succesful, should alter thermionic performance to a stage where it becomes favourable for this application.