Design methodology for identifying optimum photovoltaic system configuration at UNC Charlotte

Solar photovoltaic (PV) systems provide an environmentally friendly method to harvest energy. Incorporating a PV system onto a campus building would help offset energy costs. UNC Charlotte identified the Colvard building roof as a promising candidate for solar panels. In this paper, the feasibility of placing a PV array on the roof is investigated. Six system configurations were identified as: (i) micro-inverter and grid tie (ii) micro-inverter with grid tie and battery backup (iii) micro-inverter and battery (stand-alone), (iv) central/string inverter with grid-tie, (v) central/string inverter with grid tie and battery backup, (vi) central/string inverter and battery (stand-alone). The designs were systematically eliminated based on the benefits of (a) micro-inverters, (b) battery bank, (c) AC coupling and (d) grid interconnections. Micro-inverters were ruled beneficial based on literature review and also the expansion opportunities they afforded. The battery bank was ruled unnecessary based on power reliability data obtained from Facilities Management. AC coupling was also deemed an inefficient way to couple a battery bank based on both cost and losses in efficiency. A grid tie was chosen over a stand-alone setup due to the power reliability of on-campus power and the unjustified cost a battery bank posed. Thus, the study found that a grid-tie system with micro-inverters is the most suitable configuration for the Colvard roof space at UNC Charlotte. The study also found that laying the PV panels flat maximized yearly power output for the roof. A novel way to mount the panels by point-loading was devised, allowing additional weight to be added without compromising the roof´s structural integrity.