AC Power Systems AC appliances can be powered by adding an DC-to-AC inverter. These components electronically switch the input DC voltage and current from the battery to produce alternating current (AC) and voltage. Such a power system could then operate any load that might be needed, including computers, fax machines, radios, TVs, VCRs and CD players, refrigerators and freezers, power tools and kitchen and bathroom appliances. DC load could still be included in the system as well.

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PV-Generator Hybrid Systems

Instead of relying purely on photovoltaic modules for energy, a system can be designed with other generators available as well. A common choice is a fuel powered generator, either gasoline, propane, or diesel. These generators produce AC power that can be passed directly on to AC loads through a transfer switch that prevents any generator power from feeding backwards into the inverter. The transfer switch could be a fast acting electronic design, or a simple manual switch that the user operates when needed. The generator can also pass power through a rectifier that changes AC back to DC current and voltage. This generated DC power could be passed into the battery bank, to recharge the batteries after a long stretch of bad weather. By combining the reliability and quiet operation of photovoltaic modules with the assured availability of generator power during any season, the user can enjoy the best of both worlds.

Utility (Grid-Tied) Connect Systems Instead of having a system independent of the utility grid, a system can be designed to work with the grid. A specially designed utility-interactive inverter is needed, and many models are available worldwide. The basic design of a utility-interconnected system is quite simple. The solar array is connected to the inverter, as is the utility lines. The output is connected to the normal distribution box for the house or business. During the day, power is generated at the array and fed into the inverter, to be changed into pure sinusoidal AC power. If that power is needed in the home, it is passed on. If the load demand is less than what the array is producing, the excess is fed into the utility grid system, and energy is credited to the home. If more power is needed in the home than the array can produce at a particular moment, then power flow from the utility grid to add to the array power. Typically there are no batteries in utility-interconnected systems, so at night all the power needed flows from the utility. Recently, new designs of inverters have been created that allow utility-interconnected systems to have battery backup as well. AC power from the utility is rectified into DC power and used to recharge the battery bank during bad weather. And battey power can be used instantly if there is a utility power failure or brownout, much like an uninterruptible power supply (UPS) system. print page