Thermal analysis of a solar parabolic trough - ORC - biomass cogeneration plant of electricity and cooling applied to a shopping centre

[Master's thesis pursued at the University of Zaragoza - external thesis advisors: Miguel Ángel Lozano Serrano and Luis María Serra de Renobales] Design of a renewable system which function is covering the electrical and cooling annual demand of a shopping centre in Zaragoza, Spain. The analysis of the system includes sizing of parabolic trough collector solar field, integrated with a biomass boiler. The assembly has to provide the thermal energy needed in a power Organic Rankine Cycle which produces electricity for chillers and for other uses of the shopping centre besides, a possible connection to the city’s power grid is considered. The aim of the analysis is basically to employ a parabolic trough collector solar field designed using the software System Advisor Model [NREL. System Advisor Model 2017.9.5] and which parameters have been varied to analyse the system response and to provide different possible solutions. In order to present the technologies, a use case has been presented. The solar field has been placed within an ambient where the annual global horizontal radiation is significant: 1651 kWh/m2 [Meteonorm, www.meteonorm.com, 2018], the site is Zaragoza where this thesis has been studied. The system is also composed by a biomass boiler that complements the energy produced by the solar field to supply an organic Rankine cycle with almost a pre-set thermal input. The working fluid that flows through the power cycle is the refrigerant R245fa, chosen after comparing alternatives commercial fluids. Different possible operating results of the ORC, due to climatic conditions, are discussed. The results of the case study analysed are presented hourly throughout the year. Afterwards, an application of the whole system is presented. As it was mentioned earlier, cooling and electrical demands of a shopping centre in Zaragoza are analysed and thought to be covered by the electricity produced by the ORC. An integration with the power grid allows the whole system not to be oversized whilst, in condition of surplus of electrical energy produced, the grid connection enables additionally, to sell the exceeding electricity. In order to better combine all the components, the ORC cycle and the solar field are redesigned following the nominal power of the chillers needed for cooling the shopping centre. Furthermore, an hourly annual calculation is estimated; which is based on mean hourly values in each month of power production and electricity demand.