Basics of Grid-Tied PV
The basics of a grid-tied photovoltaic systems.
Most residential photovoltaic (PV) systems consist of PV
modules, a battery bank to store the electricity, a charge
controller to regulate the charging of the batteries, and
an inverter to change the solar-generated direct current
electricity into the more commonly used alternating
current. People living in remote areas of the U.S., off the
grid, have been relying on these types of PV systems for
years. However, more and more people who are already
connected to the grid are turning to renewable energy for
part or all of their electricity needs. These grid-tied PV
systems send solar-generated electricity back into the
already existing utility grid.
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With a grid-tied system there is no battery bank - the
utility company acts as the battery. (Many people choose to
keep batteries, however, as a backup in case of grid
failure.) When a system produces more electricity than is
needed, the excess is sold to the utility company. When the
homeowner needs more electricity than is being produced,
electricity is bought from the utility company. Under
federal law, the Public Utility Regulatory Policy Act
(PURPA, Section 210), utility companies are required to buy
electricity from renewable energy producers.
The other difference in grid-tied systems is the type of
inverter used. Line-tied inverters are designed to sense
the presence of grid power and shut off when the grid does.
This keeps the PV-generated electricity off the grid in
case there are utility people working on it.
The majority of grid-tied PV systems use PV modules mounted
on a roof or a pole near the house. However, some systems
use PV cells that actually become an integrated part of the
building (a common example are PV roof tiles). While these
systems may reduce the cost of PV systems, they are still
about 50% more expensive than standard PV modules. And
standard PV modules don't come cheap.
For more information:
Solar Energy International ,
P.O. Box 715, Carbondale, CO 81623; (970) 963-8855;
fax: (970) 963-8866;
e-mail: sei@solarenergy.org ; Web site:
www.solarenergy.org
Solar Sales &
Service ,
White Bluff, TN 37187; (800) 398-5188 or (615)
8761911;
e-mail: SOLARSALES@aol.com
Sacramento Municipal Utility District ,
P.O. Box 15830, Sacramento, CA 95852-1830;
www.smud.org
Home Power Magazine,
P.O. Box 520,
Ashland, OR 97520;
e-mail: hp@homepower.com ;
Web site: www.homepower.com
1 Maka Rukus and Jenny Freely, "Guerrilla Solar." Home
Power Magazine, Issue #67, October/ November 1998,
page 35.
