The recent push for cost reductions in solar electricity production deployment has renewed interest in concentrating photovoltaic systems. One strategy in low-concentration systems has been to reduce balance-of-system costs by reducing tracking accuracy requirements and/or eliminating tracking in the azimuth or altitude direction. However, misalignment with the sun, due to a lower-performing tracker or intentional design, hurts the concentrator's performance. The effect of misalignment on the performance of a 8.1x compound parabolic concentrator developed for inclined single-axis tracking is evaluated. Both the ray tracing simulations and measured compound parabolic concentrator results show significant effects from misalignment on the concentrator's performance. Average irradiance decreases significantly as the acceptance angle is approached in the east-west or north-south direction. Additionally, the maximum irradiance value can increase significantly during misalignment and move locations within the exit aperture, having a significant impact on thermal management design. It is important to incorporate these "real world" effects of intentional and unintentional error in sun-tracking, so that the product design is effective and the true cost of less accurate trackers is understood.
Replex Plastics aims to develop a low-cost, low-concentration photovoltaic module using a metallized acrylic reflector
designed for use with an inclined single-axis tracker. An asymmetric compound parabolic concentrator is developed and
analyzed optimizing the many factors impacting the design, such as tracking strategy, manufacturing process, and cell
size. Ray tracing is used to improve the design as well as predict the performance. Results of the simulation closely
match the tested performance of the prototype. The final design is an asymmetric compound parabolic concentrator
mounted to an encapsulated silicon cell receiver with a system optical efficiency of 60%. The prototype concentrator
achieves ~7x increase in power output over an encapsulated receiver with no reflector.
Mirror augmented photovoltaic (MAPV) systems utilize low cost mirrors to couple more light into a
photovoltaic (PV) absorber. By increasing the light absorbed, they are expected to produce less expensive electricity.
As a substrate candidate for back surface reflector mirrors, two grades of PMMA have been exposed to UV stress
from two sources at two intensities for two doses in an effort to see the response of materials under different states of
stress and after exposure to different amounts of total stress. By developing a framework for correlating stresses,
such as short wave ultraviolet radiation, with responses, such as induced absorbance and yellowing, mirror durability
we have made progress in developing lifetime and degradation science using mirror durability as a case study. All of
the samples showed similarities in their degradation characteristics. The UV stress acceleration factor was quantized
as 10.2 in short wave ultraviolet irradiance, and 15.8 in total shortwave UV dose. The effects of UV absorbers in
protecting the polymer from degradation are discussed. Further study into degradation mechanisms will elucidate the
exact phenomena that contribute to these material responses to stress.