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

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.

 

Savings

Over $2000/year in electricity costs

Over 6.7 tons of CO2/year

 

Technical Specs
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
Brand Sanyo (Japan)
Size 195 Watts
Dimensions 52 inches x 35 inches x 1.5 inches
Weight/panel 30 pounds*
Avg SystemOutput 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)

Wind speed

Temperature

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.

Alternatively, check out this series of production graphs from 2008-2012.

 

Cost

 

System Costs

number

value

total

Panels

52

$1,000

$52,000

Inverters

2

$4,000

$8,000

Installation

 

 

$30,000

 

 

 

$90,000

 

 

 

 

DAS Costs

number

value

total

System

1

$5,000

$5,000

Site electrical work

 

 

$5,000

 

 

 

$10,000

 

 

 

 

Total

 

 

$100,000

 

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.