Photovoltaic (PV) systems convert sunlight directly to electricity. They work any time the sun is shining, but more electricity is produced when the sunlight is more intense and strikes the photovoltaic modules directly (as when rays of sunlight are perpendicular to the photovoltaic modules). Unlike solar thermal systems for heating water, photovoltaic does not use the sun’s heat to make electricity. Instead, electrons freed by the interaction of sunlight with semiconductor materials in photovoltaic cells are captured in an electric current.
PV allows you to produce electricity— without noise or air pollution—from a clean, renewable resource. A photovoltaic system never runs out of fuel, and it won’t increase U.S. oil imports. Many photovoltaic system components are manufactured right here in the United States. These characteristics could make photovoltaic technology the U.S. energy source of choice for the 21st century.
The basic building block of photovoltaic technology is the solar “cell.” Multiple photovoltaic cells are connected to form a photovoltaic “module,” the smallest photovoltaic component sold commercially. Modules range in power output from about 10watts to 300 watts. A photovoltaic system connected or “tied” to the utility grid has these components:
AC electricity is compatible with the utility grid. It powers our lights, appliances, computers, and televisions.
Special appliances that run directly on DC power are available, but they can be expensive.
Before you decide to buy a photovoltaic system, there are some things to consider:
First, photovoltaic produces power intermittently because it works only when the sun is shining. This is not a problem for photovoltaic systems connected to the utility grid, because any additional electricity required is automatically delivered to you by your utility. In the case of non-grid, or stand-alone, photovoltaic systems, batteries can be purchased to store energy for later use.
Second, if you live near existing power lines, PV-generated electricity is usually more expensive than conventional utility-supplied electricity. Although photovoltaic now costs less than 1% of what it did in the 1970s, the amortized price over the life of the system is still about 25 cents per kilowatt-hour. This is double to quadruple what most people pay for electricity from their utilities. A solar rebate program and net metering can help make photovoltaic more affordable, but they can’t match today’s price for utility electricity in most cases.
Finally, unlike the electricity you purchase monthly from a utility, photovoltaic power requires a high initial investment. This means that buying a photovoltaic system is like paying years of electric bills up front. Your monthly electric bills will go down, but the initial expense of photovoltaic may be significant. By financing your photovoltaic system, you can spread the cost over many years, and rebates can also lighten your financial load.