Multi-criteria optimization of a renewable combined heat and power system using response surface methodology

Sun is one of the reliable sources of energy that is available in most locations in the world. Among various solar power units, the parabolic trough collector (PTC) is one of the most functional systems that can provide considerable thermal energy. However, this unit is not able to directly provide electrical energy. Thus, this study presents a non-dimension model of a renewable power system that incorporates a photovoltaic cell and a PTC unit. This hybrid system can simultaneously provide both heating load and electricity. The scheme is examined from the perspectives of exertion, energy, emission, entropy, and economics (5E). In this order, the influence of diverse operating factors on the outcomes of the unit, including saved cost, electrical and thermal exergies, CO2 emission, electrical and thermal energies, and entropy generation, are examined. On top of that, the performance of this innovative unit is optimized using both single-objective and multi-objective methods. The findings indicate that increasing fluid inlet temperature and solar radiation intensity lead to an increase in the temperature of every component of the unit. A stronger heat transfer from the receiver tube to the working fluid causes the temperature of the fluid and solid zones to decrease when the mass flow rate is increased. The analysis shows that the optimum value of solar radiation for the electrical exergy and saved cost is around 900 W/m2 and further reduction or increment in the value of this parameter has an unfavorable impact on both electrical exergy and saved cost. While, raising solar radiation improves all other output parameters of the unit, continuously. Also, it is found that the concentration ratio is the only parameter that elevation in its value leads to ascending the value of all output parameters of the presented system. Based on the findings, at the optimum operating condition, the value of saved cost, CO2 emission, and entropy generation are 70 USD/month, 803.956 kg/month, and 23.93 W/ m.K, respectively.