A building integrated photovoltaic thermal (BIPVT) system based on long-run metal roofing is being developed at the University of Waikato in partnership with Dimond Ltd., a long-run roof product manufacturer. The concept consists of a CNC folded metal roofing sheet with a central channel and a collector plate bonded to the roofing sheet to create a sealed channel for thermal fluid flow. PV laminates are bonded to the collector plate and inlet and outlet manifolds attached for thermal fluid distribution. When exposed to solar radiation the system generates heat and electricity for domestic and industry use.
BIPVT manufacturing methods were investigated for creating the sealed channel for thermal fluid flow. Adhesives (ADH), resistance seam welding (RSW) and autoclaving (ATC) were considered the most suitable. Processes were designed for the three methods and investigated through economic analysis. ATC was found to be the best for production volumes greater than 20,000 BIPVT panels per year as it has greater production capacity and lower capital investment payback time than ADH and RSW. ATC had a payback time of 0.26 years for 90,000 BIPVT panels per year at a 40% mark up. However ATC has several technical challenges that need to be overcome whereas ADH and RSW are proven production methods. ADH is more suitable for low production volumes below 20,000 panels per year as it has a low capital cost compared to RSW and ATC and can be readily optimised when increased production is required. Cost savings can be achieved by reducing material costs as they were 95% of the total operating costs for all methods. ADH and RSW could be readily optimised to increase production at lower capital expenditure by installing additional equipment at production bottlenecks rather than installing new production lines. ATC could not be as readily optimised as it has high production capacities.
Installing a low volume BIPVT production facility into Dimond Ltd. could potentially generate an additional $3.5 million per year in profit, for a process that produces 7,680 panels a year. Payback time for the capital investment including a PV laminator would be just over half a year making BIPVT an attractive possibility
