Photovoltaic (PV) Solar Electric Systems
In most installations PV electric works just like power from the grid. No batteries are required to store power because you remained grid tied with a net-use meter. If connecting to the power grid is cost prohibitive or undesirable, then a battery bank will be necessary to provide power throughout the day.
Solar electricity is generated by a group of solarcollectors called an array that is normally installed on a roof or a ground mounted rack. When the sun’s radiant energy hits the solar modules DC electrical current is created. The DC electricity feeds into an inverter that changes it to standard AC electricity - the same kind your home already uses. This power is feed into the grid. As needed, you pull your power from the grid as before. Should the grid go down, you would loose power despite the fact your PV system is producing. This is a safety feature to prevent power from entering a disabled line and harming lineworkers. It is possible to install an automatic grid disconnect switch and small battery bank to switch to PV power in case of an outage.
PV panels like to face south and must be in the sun, especially from 10:00-2:00. It is possible to install tracking devices that rotate the PV panel to follow the sun’s angle throughout the day, and the season. This can increase the panel output, but also increases the cost and maintenance needs.
Due to global oversupply as countless new manufactures entered the market and decreased demand in 2009 because of the worldwide economic crisis, the price on PV panels has sharply dropped. In our area we are seeing prices in the neighborhood of $5 per watt installed. After incentives (visit www.DsireUSA.org) this put the pay-back time for an average family under 10 years. You can expect your system to run 25 years or longer. That is a lot of free electricity.
The PV world keeps changing. Thin film is said to be the up and coming technology. It can be applied to any smooth surface and is flexible. Currently standard crystal panels outsell and out produce thin film, but that may soon change. We now have many types of roof integrated systems that are visually appealing.
Net-use meter
A standard electrical meter tracks the power you pull from the grid. A net-use meter has the ability to track not only use, but also credit your account for the power your PV system feeds into the grid. With a net-use meter a battery system is not necessary since you will pull power from the grid to meet your needs. The use charges are offset by the power you feed into the grid. The power company uses a 12 month window to calculate your net use. Often there is excess production during the long days of summer and you draw from the grid during the shorter days of winter. The ideal is to “net to zero” as excess production is forfeited.