Study on Thermal Economy of Solar-Coal Hybrid Power Generation Units

Three integrated modes of solar-coal hybrid power generation systems were proposed, in which the solar energy was introduced respectively at the place of boiler evaporating heating surface, extraction side of high pressure heater, and the low-pressure cylinder of steam turbine. Following evaluation indexes were defined, such as the solar thermoelectric conversion efficiency, the amount of unit coal saving and the thermal contribution rate of solar energy, etc. Taking a 300 MW power unit as an example, the thermal economy of three integrated schemes was calculated and compared using equivalent enthalpy drop method, after which the optimal integrated mode of hybrid power generation was determined, together with a preliminary analysis on its thermal economy. Results show that the thermal economic indexes, the operation safety and stability of scheme 2-1 are relatively good among the three schemes, which therefore is regarded as the optimal integrated mode. In the hybrid power generation mode, the unit cost of solar power generation is 0.63 RMB/(kW·h), being less than the cost 0.75-1.85 RMB/(kW·h) under pure solar energy power generation mode.