Routines have been written and added to the Wright State developed solar system simulation program called Solar_PVHFC to model incident solar radiation for a compound parabolic concentrator (CPC) that uses solar panels (photovoltaic panels) to produce electrical energy. Solar_PVHFC is a program that models a solar energy system composed of solar panels to produce electricity from the sun, hydrogen storage tanks to chemically store the energy produced by the solar panels, and fuel cells to convert between electrical and chemical energy when required. Solar_PVHFC features several adjustable parameters to model a solar panel, hydrogen storage, and fuel cell system. Now Solar_PVHFC can model CPC solar panels. The CPC portion of this program allows for building and modifying CPCs based on three input variables: the concentration ratio, the degree of truncation, and the absorber width. Included in the program is a crude cost analysis that can be used as an economic means of comparing variations of CPCs and comparing CPCs against conventional solar panels.
Solar_PVHFC models available solar radiation impinging on a solar panel using TMY3 data files. Inputs include the tilt and azimuthal angle of the panels, the geographical location of the panels, and the time period of the analysis. Because of this thesis work, Solar_PVHFC can now model panels that track the sun for any configuration of one or two axes of rotation and can even incorporate rotational limits. This thesis investigated panels using a fixed orientation, three different single axis tracking orientations, and two axis tracking. Any manufactured module with known specifications can be used as the solar panel, and the program calculates the current-voltage curve and maximum power point for that module on an hourly basis. This thesis investigated CPC and conventional solar panels with module efficiencies of 15.2%, 20.4%, 21.5%, and 28.3%.
CPC solar panel simulations were run for concentration ratios of 2, 5, and 10. The degree of truncation ranged from no truncation with a truncated height ratio of 1, low truncation with a truncated height ratio of 0.75, moderate truncation with a truncated height ratio of 0.5, and high truncation with a truncated height ratio of 0.25. The absorbing width is the width of the solar cells at the bottom of the CPC and was scaled with the concentration ratio in an effort to maintain almost consistent total opening apertures. The absorbing width had values of 0.1657 m, 0.06627 m, and 0.03313 m with concentration ratios of 2, 5, and 10 respectively. Different mirror reflectivities and the use of cooling were also investigated.
The standard of comparison between different configurations of CPCs and conventional panels was the LCE (levelized cost of energy). This was calculated based on inputs of solar cell price and reflector material price on a per unit area basis. The LCE analysis used in this work only accounts for the solar cell and reflector costs and does not include costs associated with framing, tracking, wiring, inverters, maximum power point tracking, etc. It was thought that these costs would be similar for both the conventional solar panel system and the CPC solar panel system. This thesis’ cost analysis only looks at the part of the system where the analysis used provides differences between the CPC and conventional solar system. The electric output per unit area was also used as a means of comparison between the two systems.
Many results are shown and discussed in the main body of this thesis with an exhaustive collection of results found in the Appendix. East-west, north-south, and two axis tracking showed that CPCs could significantly reduce the LCE of higher priced conventional panels using the same solar cell module. Fixed and vertical axis tracking did not prove very effective for CPCs. The only CPC system to achieve a lower LCE than the low efficiency, low cost conventional panel was the low efficiency CPC, and this was conditional on two axis tracking and high reflectivity. The most effective CPCs generally utilized high degrees of truncation and low to moderate concentration ratios, with the exception of CPCs utilizing high concentration in combination with cell temperature control. All CPCs showed a drop in electric output per unit area compared to conventional panels; with north-south tracking showing the least drop.
A decrease in reflector costs and in high efficiency solar cell costs could enhance the potential of CPC solar panels. A higher mirror reflectivity could also make CPCs more competitive with conventional panels. CPCs show promise when compared to expensive, high efficiency conventional panels, but cannot compete with inexpensive, lower efficiency conventional panels. A more thorough cost analysis may bring more clarity to the comparisons between CPC solar panels and conventional solar panels.