Hybrid Solar and Coal-Fired Steam Power Plant with Air Preheating Using a Solid Particle Receiver

Abstract

Fuel reduction has been achieved for coal power stations by hybridisation with solar thermal systems. Current technology uses feedwater or turbine bleed steam (TBS) heating with linear Fresnel based concentrated solar power (CSP) fields. The low temperature heat produced by these systems results in low solar to power conversion efficiency and very low annual solar shares. In this paper the technical advantages of solarising coal fired power plants using preheated air by a novel CSP system based on a solid particle receiver (SPR) are examined. This system is compared to the current deployed state-of-the-art coal plant solarisation by modelling the systems and analysing the thermodynamic heat and mass balance of the steam cycle and coal boiler using EBSILON®Professional software. Annual performance simulation tools are also used to calculate the performance of the solarisation technologies. Solarisation using SPR technology for preheating air in solar-coal hybrid power stations has the potential to considerably increase the solar share of the energy input by 28% points at design point and improve the annual fuel reduction from 0.7% fuel saved to 20% over the year. This is a significant reduction in fossil fuel requirements and resulting emissions. These benefits are a result of SPR solar system’s higher operating temperature and integrated thermal storage, which also allow a buffered response time for handling transients in the intermittent solar resource. Analysis indicates air-solarisation of coal plants can enable 81% higher solar to electric conversion efficiency than currently existing solar hybridisation option. Thus, the cost of the thermal energy generated by Fresnel based TBS solarisation must be up to 38% lower than thermal energy generation of secondary air preheating SPR system for economic parity between the options. Initial calculations indicate that the required thermal energy cost levels for SPR systems for this application are already achievable.