On the design of product integrated photovoltaic systems

With photovoltaic (PV) systems it is possible to create electricity generation systems for a wide range of purposes, of literally any size (microwatts to gigawatts). Solar cells deployed in large scale, grid-connected PV systems may energize millions of electric appliances connected by a utility grid. Solar cells may also be incorporated into single electronic appliances, such as calculators. In this thesis, the focus is primarily upon these Product Integrated PV (PIPV) systems. Employing solar cells to power electronic appliances could have beneficial effects in many aspects. For one, the economic enticement seems attractive, which is due to the large quantities of units involved in present-day product manufacturing. The environment could also benefit, especially when PIPV systems replace products nowadays shipped along with primary (single-use) batteries. Solar PV may also help powering electronic appliances for approximately 1.6 billion people who, as of yet, lack access to utility grids entirely. Finally, also consumer awareness toward PV technology in more general terms can be influenced. Many of the PIPV systems currently commercially available, however, show shortcomings making them non-competitive to their non-PV powered counterparts. In this thesis, the focus is on modeling the energetic performance of PIPV systems, from a physical and technological perspective. The aim is to thereby develop methods and tools and to generate data that may facilitate technical decisions during the design process of PIPV systems. The data, methods and (software) tools to be developed should in particular allow for eased energy balancing calculations. One research question addressed is whether and how the use of Computer Aided Design (CAD) software environments allows for simulating PV power output and PV energy yields, respectively. It is found that the three-dimensional drawing, rendering and ray-tracing features of CAD software may provide a key tool for the simulation of the energy yield of PIPV systems. In such ‘CAD-PV’ simulations, 3-D irradiation conditions are ray-traced in 3-D CAD sceneries, which were created using the 3-D drawing features available in most CAD environments. Comparisons of measured to simulated PV output of the mouse showed that, also in practice, simulation accuracies can be very high. Theoretically, this concept has great potential, as it can be adapted to suit a wide range of solar energy applications, such as sun-tracking and concentrator systems, and Building Integrated PV (BIPV) or Product Integrated PV (PIPV) systems. Another research objective addressed in this thesis is solar cell performance modeling at low-light conditions. Efficiency of PV cells is usually reported only for Standard Test Conditions (STC): 1000 W/m2 irradiance intensity of perpendicular incidence under Air Mass (AM) 1.5 spectral conditions, and 25 degrees Celsius cell temperature. Indoor irradiance intensity, however, is much lower and also spectral compositions can be very different from the AM 1.5 reference spectrum for PIPV used indoors. Here, it is investigated to what extent procedures could be improved, adapted, or developed for a more detailed estimation of the PV efficiency under non-STC operating conditions. Finally, also environmental aspects of PV electricity for outdoor-operated, grid connected PV systems are addressed.