The conversion of sunlight to electricity requires the use of photovoltaic (PV) cells. These semiconductors are needed to convert the sunlight directly into electricity. Almost everyone is familiar with these devices which power many of our hand held calculators and they are being used in more and more decorative or landscaping lighting.
On a larger scale, they can be used to power circulating pumps, ventilation fans, and security systems. Taking this further, they can be integrated into the home to produce and, when combined with batteries, store energy replacing some of the need to purchase electricity.
There are several ways to put PV’s to use in stand-alone applications:
Direct coupled – similar to the calculator, this PV is directly connected to a pump, fan, or light. It does not store the energy, but allows you to power these items during times when enough light is available. Using the solar power to run an air conditioner is a great example of taking advantage of the simultaneous need for air conditioning and the availability of sunlight.
Battery storage for DC loads – PV’s produce direct current (DC) which is the same as power from a battery. In this situation, the PV charges the battery (with the help of a charge control to prevent over charging) and the battery powers the lights or appliance. Only DC loads can be powered with this design.
Battery storage for AC loads – Alternating current (AC) is what powers our homes. In order to convert the DC from batteries or PV cells, into AC, an inverter is required to change the DC to AC. Battery storage designs allow the use of equipment at night and on cloudy days.