A group is considering installing a solar power station and hasasked you for your recommendation for a photovoltaic system or asolar thermal system. At this stage you are asked not to includecost factors. The single point design condition they have given youis for an incident solar radiation on the collector of 550 W/m2, asurrounding temperature of 18 C. The dead state for this problemshould be taken as To = 291 K, Po = 1 bar. You can perform youranalysis at steady state conditions. In addition to determining thepower output and first law efficiency of the options, you have beenrequested to determine the exergy destroyed for each of them. Thephotovoltaic system has an efficiency of 0.15 defined as the poweroutput/incident solar radiation. The basic photovoltaic collectoris 1.1 m2 and losses heat from both the front and back surface. Theedge area can be neglected. The convective heat transfercoefficient is 10 W/m2 K. The inverter and signal conditioningdevice used to connect the photovoltaic collector to the grid andhousehold has an efficiency of 0.87. The inverter operatesisothermally. The solar thermal collector will heat the workingfluid from a temperature of 32 C and has a concentration factor of10,000. The concentration factor is the ratio of the incident solarradiation on the heat transfer surface to the incident solarradiation area. It is a concentrating collector with an opening of1.1 m2 and a heat transfer area of 0.05 m2. The mass flow rate ofthe working fluid through the system is 0.009 Kg/s. The heattransfer area is not equal to the area of absorption. Theconvective heat transfer coefficient is 1.0 W/m2 K. The heattransfer from the collector can be considered to be at the averagetemperature of the working fluid, (Tin + Tout)/2. The specific heatof the working fluid is 678 J/(Kg K). The useful energy from thiscollector system is the change in the enthalpy of the flow throughthe system. The working fluid enters a heat engine with anefficiency of 0.30 that is connected to a generator with anefficiency of 0.90. The generator operates isothermally.
Answer the following:
a) Determine the power output for each type of system for abasic collector area.
b) Determine the exergy destroyed for each type of system.
c) Which system would you recommend on this analysis? Thisquestion neglects the costs.
