IMEG provided engineering design and services for the utility-scale Red Rock Solar Generating Facility for Arizona Public Service (APS). The project is APS’s largest solar plant to date with 2,286 single-axis trackers supporting 182,880 photovoltaic panels generating 40 MW-AC and 57.6 MW-DC of solar energy on 400 acres.

Engineers provided electrical engineering design for the project, which received an award of merit in ENR Southwest’s 2017 Best Projects competition. The design included trackers self-powered by the photovoltaic modules and a throat connection between the inverter and medium voltage transformer to “close couple” the equipment, saving on installation and wiring costs by using fewer termination points and feet of conductor. (This was IMEG’s first use of throat connections, now a standard industry practice.)

An arc flash hazard evaluation had to be completed while commissioning and testing procedures took place, but areas within and connected to the inverter can be particularly dangerous when energized. Some commissioning activities and acceptance testing required personnel to interact with energized equipment, so engineers evaluated the specific construction of the inverter cabinets and commissioning and testing procedures to recommend protocol that would allow these activities to take place without excessive additional cost or time. Engineers led a meeting with multiple APS departments to coordinate the protection scheme and to work out the design of the interconnection point.

Construction began in March 2016 and was completed in December 2016. Arizona State University and PayPal have contracts to purchase solar power from the Red Rock plant.