Higher Learning: Rooftop Solar Workshop
From as far as Staten Island, NY to York, PA, participants in MAREA’s most recent Solar Installation Workshop sweated and smiled through four vigorous days of cooperative work and learning.
This installation took place on a residential rooftop in Kutztown, PA at the home of Gene and Vivian Mosca. The installed solar electric system uses microinverter technology from Enphase with 30 Solon 225W solar modules for a system power rating of 6.75 kW. The system is expected to offset about 80% of the home’s annual electricity consumption. The state-of-the-art system was designed by Bill Hennessy, a NABCEP-certified PV installer and partner in Berks Solar, the business responsible for the installation.
Each day involved both classroom training and rooftop installation. Vera Cole, author of Pennsylvania Homeowner’s Guide to Solar Electricity and faculty member in Penn State’s Energy and Sustainability Policy Program, led many of the training sessions on topics including solar electricity principles, site and design considerations, system sizing, and financial considerations. Phil Jones, a LEED®AP and BPI-certified Building Analyst and director of Green Business Solutions at EMS Environmental, led an afternoon session on energy conservation and efficiency—essential considerations for all renewable energy generation projects.
Though the workshop was MAREA’s fifth PV installation, there were many firsts, including a rooftop site, Enphase microinverters with monitoring, and a new Power Rail racking system from DPW. It kept things hopping! Workshop participants, with the supervision of instructors and Lee Kauffman, the project electrician, worked on all aspects of the installation, learning first-hand (literally with their hands!) the nuts and bolts of solar systems. Most had no previous experience with solar but found this to be a great way to learn, and have fun doing it. Doughnuts, ice cream and fresh sandwiches delivered from Betty’s Wraps each day didn’t hurt either!
The homeowner’s solar plans include the solar electric array plus a solar hot water system on a roof that also has a chimney near the center. For this reason, the solar array was arranged into two sections on either side of the chimney, leaving the area beneath the chimney for a future solar hot water install (a plumbing convenient location). To begin, participants measured the roof carefully, identified rafters and laid out the rails and mounting points. L-feet and flashing were then installed and the rails attached. Then microinverters were mounted to the rails, one microinverter per module. The microinverters convert the DC generated by each solar module into AC of grid quality. Standard AC wiring (Romex) was routed from the roof to breakers in a subpanel in the basement, then to a production meter (newly installed, just to measure solar electricity production) and then to the electrical service panel.
Each microinverter comes with a pull-off sticker that has its unique serial number. These stickers were lifted off each inverter and placed on a map showing where in the array each microinverter is physically located. This map is important for monitoring over the years so that if there is a problem with an inverter a technician will know where to locate it in the array. Grounding wire was attached to all microinverters and rails in the system. Then AC connections were made between the inverters (just by plugging them together), connecting the microinverters into two branches of 15 each. Next, the solar modules were installed and grounded and the DC connections made with the microinverters. To complete the installation, an Envoy energy management unit from Enphase was setup near the main service panel and initialized until it recognized all 30 microinverters on the roof. This unit will provide on-going monitoring of individual microinverter/module performance.
This home uses approximately 10,000 kWh of electricity each year at a cost of more than $1400. The system is projected to generate approximately 8,000 kWh of electric energy, so the homeowner’s cost for electric energy will be greatly reduced. In addition, the homeowner will earn about 8 Alternative Energy Credits each year. (One AEC for each 1,000 kWh of clean electricity generated.) Most important to the homeowner, however, are the benefits to the environment. Over a 25-year system life, this solar installation will avoid more than 150 tons of greenhouse gas emissions.