Solar Electric (Photovoltaic or PV) Systems
A solar electric system can go on any south-facing roof or ground area that is unshaded from 9:00 - 3:00. Solar is a great way for you to generate some of your own power and reduce our dependence on power plants, the 2nd largest contributor to climate change.

Solar panels are most efficient facing within 30 degrees of True South. 40 degrees is the optimum tilt for yearly production, a lower angle favors summer production.

How They Work….
Solar Electric (or Photovoltaic) Systems generate electricity anytime the sun is shining. The panels are made up of two layers of silicon that have been doped to create a positive and negative layer. As the sun shines on the panels, electrons flow from the positive to the negative. If a circuit is attached to the metal contacts on the panels, direct current flows. This current goes to an inverter and becomes alternating current for use in houses and buildings.

With grid-tied systems, the electricity generated is used right away. Or, if it not needed, it goes back out to the utility grid for use at another location, spinning the electric meter backwards. In Massachusetts, with net metering, you are charged each month only for the amount your meter has spun forwards. You get retail rate credit for the electricity your solar system has produced. Grid-tied systems are reliant on matching the sine-wave of the utility grid. During power failures, they shut down. This is for safety reasons. Grid-tied systems are the most effective way to make an environmental contribution with solar electric.

A typical family of 4 uses 600 kilowatt-hours/month or 7200 kwh/year. With energy efficiency efforts, this number can be reduced by 25-50%. A 2.5 kilowatt grid-tied system can then be used to provide another 3000 kwh/year.

With stand-alone systems, the direct current from the panels is stored in batteries until it is needed. Then, it is turned into alternating current for use in the building. The Vineyard has number of these systems where connection to the grid is not possible or, is expensive. Cape Poge and parts of Tisbury Great Pond are two examples.

A hybrid of grid-tied and stand-alone is an emergency back-up system. These systems have solar panels, an inverter and batteries. On a normal day, they feed the excess power back to the grid. During power failures, power is drawn off the batteries for use in the house. These systems don’t operate as efficiently as grid-tied systems at times of normal operation and, they require a large number of batteries if back-up is desired for more than some lighting, refrigeration and water-pumping. The batteries add a significant expense to the cost of the project. We have a few of these on the Vineyard but, many solar experts believe that a generator is a better solution during times of power failure.

Mounting
Solar electric panels can be mounted on a south-facing roof or ground area. Roof-mounted systems use aluminum rails that are attached to roof rafters. Panels are connected to the rails. Ground-mounted systems have a pressure treated frame that the aluminum rails are attached to.

It is also possible to do a “tracking” system where the panels follow the path of the sun. These systems have a single pole that goes down in the ground about 8 feet, supported by a concrete footing. The racks are connected to the pole. These systems cost a bit more to install and are generally used in sunnier climates than ours. They will increase production here by about 20%.

A number of reasons to go solar:

• Solar Electric systems are low-maintenance and make power for the island whether you are here or not! There are no moving parts to a PV system. The panels will last 20-30 years.
  
• A solar electric system is a hedge against the uncertainty of future rate increases. As fuel costs rise, so will our electrical rates.
  
• Because of net metering, you receive credit for any power that you generate. As the sun shines, solar provides power for your house. If you don't need it at the moment, your electric meter spins backwards! You receive credit for any power you make.
  
• Electricity generated locally is more efficient, cleaner, secure and reliable.
  Power plants are a big contributor to air pollution. There are great transmission losses when power travels long distances. Making power at your own home eliminates these losses.
  
• Solar provides power at peak times: on those hot summer days at the time of day when we need it most.
  
• A 1 kilowatt system reduces your greenhouse gas emissions by about 1 ton/year.
  

Combined with energy efficiency, this is an easy way to help slow Climate Change.

Cost of an Installed System: See Solar Funding Opportunities Page for price, subsidies and tax credit opportunities.

Required Paperwork:

• NStar application for connection to the utility grid and completion form;
• Permit application and inspection by Town Wiring Inspector;
• Massachusetts Renewable Energy Trust application if you wish to be part of the subsidy program including:
• A copy of a contract with a solar supplier/designer and an installer;
• Drawings of the proposed system;
• A copy of an electrical bill;
• A copy of your energy audit if you have had one done OR,
  agreement on the application that the audit and recommendations of the audit will be completed within the year that your system is installed.
• certificates of insurance for your electrician and rack installer that meet the MRET requirements.