St. John's County Council on Aging Transit Facility Solar Power

GRAEF worked directly for St. John's County providing electrical and structural engineering services to design a solar power system with supporting structure to provide power for the operation of the entire Council on Aging (COA) Transit Facility. The existing facility was built in 2010. It is approximately 6,600 square feet and houses administrative offices with covered porches and a multiple bay fleet maintenance garage with a mezzanine. GRAEF designed the new solar energy system located in the existing bus parking lot.

Electrically, GRAEF designed a grid interactive solar power generation system consisting of photovoltaic (PV) panels and minor upgrades to the existing security system. We determined the methods for interconnecting the PV system with the electric utility production and distribution network system, analyzed the existing kilowatt (kW) demand as registered by the electric utility company, estimated the tier level of PV kW production, determined point of connection to the existing premises wiring system, designed a 63 kW ground-mounted PV panel array system, and detailed one-line diagrams depicting PV components types and sizes along with the interconnecting conductors/conduits types and sizes. Additionally, GRAEF designed and selected circuit wiring methods, overcurrent protection, disconnecting means, and utility-interactive inverters.

Structural systems included auger cast concrete pile foundations and concrete piers supporting hot-dipped galvanized structural framing to carry the arrays which allow the buses to park beneath the structures. There are 19 total arrays with multiple panel arrangements including a 10 panel layout and a 12 panel layout.

The project has resulted in the Council on Aging facility being a Net-Zero Energy Building. The facility is a grid-connected building enabled to generate electricity from renewable resources (PV panels) to compensate its own electric demand. In other words, it produces more electricity than it uses during the daytime. The electricity that is produced by the PV panels during the daytime that is in excess of what the building requires is sold to the grid. At night, electricity is purchased back from the grid as necessary.