Energy and exergy analysis in typical days of a steam generation system with gas boiler hybrid solar-assisted absorption heat transformer

A solar-assisted absorption heat transformer (SAAHT) is a useful substitute for the conventional equipment to generate low-pressure steam. A 100 kW steam generation system with a SAAHT in Langfang (China) is evaluated in this study. Hourly thermodynamic performance, including system efficiency, exergy efficiency, CO2 emission reduction rate and output heat in typical days in four seasons, is discussed. Results show that ambient temperature has a smaller effect on system performance than solar irradiation. In any one of the typical days in spring, summer and autumn, the system presents higher output heat and CO2 emission reduction rate, more stable system efficiency and exergy efficiency than those in winter. Comparative results from two methods show that ratio method has higher system efficiency with solar irradiation below 600 W/m2. A hybrid method combining both the degree method and ratio method is adopted to work with the off-design condition, and results show that performance improvement for system is not so obvious as that in solo absorption heat transformer. Among the four typical days, the most obvious improvement occurs in summer with cumulative output heat increasing from 1318 kWh to 1343 kWh, and the CO2 emission reduction increasing from 296 kg to 301 kg.