Our Solar Array
Our solar panel system is located on top of our two-hundred-year-old barn, just above one of our passive solar greenhouses. We chose this location due to its southern orientation and its proximity to the Farm’s utilities. The system is a “grid tied” system, meaning any excess energy that is generated that the farm does not use gets transferred to the main electrical grid to be used by our neighbors.
Benefits & Savings
Our solar panel system is a renewable, self-generated power source that provides roughly 40 percent of the Farm’s electricity. The system also serves as an important educational tool for students and community members to learn about renewable energy. It saves over $200/year in electricity costs and over 6.7 tons of CO2/year.
Date of Installation: January 2008
|Site||Southern-facing, 160 degrees; Roof pitch (angle) is 30 degrees|
|Inverters||(2) from SMA Inc.; 7 kilowatts and 6 kilowatts|
|Solar Panels||52 crystaline and amorphous panels|
|Dimensions||52 inches x 35 inches x 1.5 inches|
|Avg System Output||10 kilowatts|
|Maximum Inverter Capacity||13 kilowatts|
*The overall weight of our system was an issue given the age and design of our barn’s roof — a structural analysis constrained the use of heavier panels.
Many people have asked us why we selected two inverter units, and why we wanted more inverter capacity than what the panels specified. Our answer is that panel rating represents an average output rating. They are actually capable of more than 10 kilowatts. So, on a sunny, cool day, when they are putting out more kilowatts than they are rated for, we wanted to be able to capture that extra output. The higher rating should also help to increase their life expectancy.
Data Acquisition System (DAS)
This is the system that collects pertinent information related to the overall system performance:
Irradiance (a measurement of the sun’s strength or density of radiation on a surface)
Current power (kilowatts) output
Total lifetime system power output (kilowatt-hrs).
This is critical to the educational aspect of the system as well as tracking the total energy produced and thus the net savings. The data is available on the web at: SunnyPortal.
|Site electrical work||$5,000|
How the System Was Funded
Massachusetts Tech. Collaborative provided us with a grant of $47,500. 90% of the grant was paid within 60 days of project completion; the balance was paid after 12 months of reporting monthly power output. The remainder of the project was funded by additional grants and private donations.