Pathways to the use of concentrated solar heat for high temperature industrial processes

Abstract

New analysis is presented identifying strong potential for Concentrating Solar Thermal technology (CST) to be a cost-effective contributor to future sources of net zero-emissions, high temperature industrial process heat relative to other emerging options. Nevertheless, significant further development of the technology is needed to realise this potential because the majority of previous investment in CST has targeted lower temperature applications in power generation, which employs different working fluids and typically operates at different scales. A comparison with the flame temperatures typically employed in current industrial processes, together with an allowance for thermal storage, suggests that receiver temperatures in the range of 1100 − 1500 °C will be needed to drive many current high-temperature industrial processes, which is far above the range of temperatures employed commercially and also above the range at which most pilot-scale work for CST has been undertaken to date. Technology development will therefore be needed to realise this potential, both for the solar thermal plant and for the industrial processing plant, since current reactors have been developed to utilise fossil fuels. More work is also needed to advance understanding of the best options with which to hybridise CST with another back-up energy source, such as hydrogen, since it is uneconomical to seek to manage seasonal variability with thermal storage alone.

A case study is then presented of the techno-economic performance of a system based on the solar expanding-vortex receiver, which has proven potential to operate at the required temperature range and also employs air as the Heat Transfer Media (HTM) to facilitate integration into existing industrial processes. This analysis summarises the first major assessment of a fully integrated system that considers the full path from the solar plant to the industrial processes with thermal storage and combustion back-up, using a transient model that accounts for one year of resource variability in 15 min time intervals. The complexity of the system is compounded by the interdependence of the performance of each component, whichmakes it challenging to optimise. For example, the costs of integrating the solar thermal output to the industrial plant can be comparable with that of the heliostat field for a single tower at scales of 50MWth. However, the relative cost of integration decreases with an increase in thermal scale. Importantly, the best of these systems is found to have good potential to provide cost-competitive Levelised Cost of Heat (LCOH) compared with projected costs for other options for net-zero heat, notably green electrical power and hydrogen with storage, provided that the solar resource is good. Furthermore, it is anticipated that further reductions in LCOH will be possible, both with further system optimisation and with future technology development, such as that employing alternative HTM including steam or particles utilising other types of emerging technology also under development. Finally, some plausible pathwats are identified to seek to establish CST technology for application in high temperature industrial processes.