Solar tracking evaluation and comparison towards a competitive Solar Challenger race vehicle

Abstract

Observed global economic growth increases the demand for energy that is currently, especially in South Africa, generated with unsustainable fossil fuels. A substantial energy user is mobility that includes transportation. It seems that future markets are searching for alternative greener energy sources. One of the largest accessible sources of sustainable energy on earth is the sun, with a large drive of sustainable energy supply aiming at solar power. A sustainable mobility option would be solar powered vehicles and the Sasol Solar Challenge is a testing and development platform for this new technology. The South African Sasol Solar Challenge is a biannual competition and claims to be the ultimate test of technology and innovation. Being the ultimate technology test, it sees the development of some of the world’s most innovative energy technologies. Solar challenger vehicles are prototypical, fully electric vehicles, developed by research and competitive teams. The technology developed by these teams, similar to Formula 1 (F1) racing, might be seen in some form or another in electric vehicles of tomorrow. Events like the Sasol Solar Challenge accelerate research into more efficient solar cells, solar panels (also known as solar modules or PV modules), batteries, semi-autonomous vehicle technology, and battery management and protection systems. This study evaluates and compares solar tracking options towards a competitive solar challenger vehicle. It evaluates a proposal of a transparent aerodynamic cover under which tracking solar panels (also known as PV modules) could move freely, without influencing the aerodynamic characteristic and drag coefficient of the vehicle. This includes test methods, test instrumentation and final evaluation for an optimal cover material. Results indicate the gains with solar tracking and losses of irradiation of cover material with tracking that needs to be considered for drag coefficient gains towards a competitive solar challenger race vehicle. The study started by evaluating special cover materials, i.e. considering their chemical and physical properties. Then demonstrating the design, construction and testing of a scale-model instrument with which to evaluate and compare solar tracking, with and without such covering material. Thereafter it demonstrates the evaluation and comparison of solar tracking of the full-scale 2018 solar power challenger vehicle. The results of small-scale experimentation led to alterations on the full-size solar vehicle design, which included bypass diode placements. The preselection of materials, the design of scale testing instrumentation and scale results compared to the full-scale results are discussed to indicate the gains and losses that occur for a proposed cover. The scale model saw a 7% – 11% energy loss with the presence of the cover. On the full-size model this increased drastically to 20% – 33%. This large difference could be a result of the intense heat generated in the full-size model, as well as the environmental damage (scratches, sunburn) on the clear polycarbonate cover at the time of testing. Measurements were taken in all four cardinal directions. Finding of the research study has showed an increase in power with tracking, but that the energy loss of the cover does not justify decreasing of drag coefficient, when traveling at low speeds. Using real-world measured power, one should, however, reconsider this loss in the drag coefficients of new designs and/or the physical protection of cover material or other factors, like aerodynamic stability and drag at higher speeds.