The St Louis Science Center project was a challenge that we met through careful planning and execution. The array is in two sections; a portion on the roof of a tall public foyer and an additional section atop an exhibit and walkway extension 40 feet above a busy city street and interstate highway. The installation required shutting down traffic on the public street for the crane lift, and working around the busy schedule of school groups and buses of excited school children. Due to the public exposure and proximity to the street and interstate, the racking design was a hybrid ballasted and fastened system. The Enphase microinverter system delivers the highest level of safety and optimized performance in the difficult shading conditions. In addition to the solar-PV system at the St Louis Science Center, we also designed, engineered and installed a solar-PV array on Evie, the Science Center’s electric truck. Evie goes to events around the region promoting energy understanding and conservation, and the solar-PV array allows the truck and all her exhibits to be powered by the sun instead of burning coal. Evie has solar-PV panels on her roof and a tilt-up array on the back, and a battery bank and complete control and management system inside.
Design Rationale and System Architecture: The St Louis Science Center (SLSC) entrusted their new mobile outreach platform to us to design and implement a very small but complicated system. Even though this system is only 3 kW of PV power capacity, it is two completely separated PV arrays integrated in a DC-coupled bus system. One of the arrays employs bi-facial PV modules, so that they will produce electricity from direct sunlight and reflected sunshine from the ground. That array also tilts out to provide shade and shelter while parked, but be safely tucked against the truck body while driving.
Project Challenges: The primary goals of the project were safety and simplicity for a cadre of volunteer Evie operators. The operation and procedures had to be clear and clearly documented. We provided a complete and clear Owner’s Manual for all projects, but this project required an added measure of care and attention that has allowed the electric truck to operate successfully since 2010. This long life expectancy also had to prevail in spite of the extended vibration caused by a large panel van driving down all manner of highway and byway.