Exergoeconomic comparison of solar-assisted absorption heat pumps, solar heaters and gas boiler systems for district heating in Sarein Town, Iran

• Published in: Applied thermal engineering 2019-05, Vol.153, p.409-425
• Main Authors: Salehi, S., Yari, M., Rosen, M.A.
• Format: Article
• Language: English
• Subjects: Absorption; Absorption compression-assisted heat pump; Ammonia; Boilers; District heating; Efficiency; Evaporators; Exergoeconomics; Exergy; Feasibility studies; Freezing; Gas boiler; Heat pumps; Heat sources; Heating load; Heating systems; Hot springs; Multiple objective analysis; Optimization; Pumps; Solar energy; Solar heating; Solar heating system; Solar-assisted absorption heat pump; Space heating
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2019.03.022

•Solar-assisted absorption heat pumps economically compared with solar heating and gas boiler systems.•Geothermal hot springs are used for evaporation process and prevention of freezing.•The exergy efficiency has the highest value of up to about 25% for LiBr/H2O absorption systems.•The product unit cost for solar heating system has the highest value of about 220 $/GJ in December.•Gas boiler and NH3/H2O absorptions systems have the lowest values of product unit cost of about 25 and 40 $/GJ, respectively. The feasibility of solar-assisted absorption heat pumps for space heating is assessed with exergoeconomics and compared with gas boilers and solar heating systems for the town of Sarein in Iran. In the study, single-effect LiBr/H2O and NH3/H2O absorption and absorption compression-assisted heat pumps are analyzed for heating loads of 50–2 MW. Using the geothermal hot springs located in Sarein as heat sources for refrigerant evaporation, the problem of freezing is prevented. In addition, a multi-objective optimization is performed to specify the optimal design points considering the temperatures of the evaporator and generator as decision parameters. Simulations show that the gas boiler and the solar heating system have the lowest and second lowest values of exergy efficiency, at about 45% and 35% lower than the exergy efficiency for NH3/H2O absorption systems. The maximum achievable exergy efficiency for the NH3/H2O and LiBr/H2O absorption systems are 0.23 and 0.25, respectively. But, the solar heating system has the highest product unit cost, mainly due to its high capital costs. The minimum obtainable product unit costs for the NH3/H2O and LiBr/H2O absorption systems occur in April, and are about 22 $/GJ and 55 $/GJ, respectively.