Electrical devices available at the residence are itemized with their power ratings and time of operation during the day to obtain the average energy demand in Watt-hour per day. The total average energy consumption is used to determine the equipment sizes and ratings starting with the solar array and ending with system wiring and cost estimate.

Solar photovoltaic systems (PV systems) includes different photovoltaic components that should be selected according to your system type, site location and applications. A Balance-of- System wired together to form the entire fully functional system capable of supplying electric power. The required components are:

PV module

It is made from semiconductors and convert sunlight to electricity. The PV converts sunlight into DC electricity. The most common PV modules include single or polycrystalline silicon and amorphous silicon with other technologies entering the market.

Battery

Stores energy for supplying electrical appliances when there is a demand. Battery banks make the energy available at night or at days of autonomy (sometimes called no-sun-days or dark days), when the sun is not providing enough radiation.

These batteries, usually lead-acid, are designed to gradually discharge and recharge 80% of their capacity hundreds of times. Automotive batteries are shallow cycle batteries and should not be used in PV systems because they are designed to discharge only about 20% of their capacity.

Solar charge controller

Regulates the voltage and current coming from the PV panels going to battery and prevents battery overcharging and prolongs the battery life.

Inverter

Converts DC output of PV panels or wind turbine into a clean AC current for AC appliances or fed back into grid line. It is one of the solar energy system’s main elements, as the solar panels generate dc voltage. Inverters are different by the output wave format, output power and installation type.

It is also called power conditioner because it changes the form of the electric power. The efficiency of all inverters reaches their nominal efficiency (around 90 percent) when the load demand is greater than about 50 percent of rated load.

Load

The term load represents electrical appliances which are connected to solar PV system such as lights, radio, TV, computer, refrigerator, etc.

Other considerations

But just knowing the photovoltaic components is not enough. The photovoltaic systems are classified according to how the system components are connected to other power sources such as standalone (SA) and utility-interactive (UI) systems.

In a stand-alone system the system is designed to operate independent of the electric utility grid, and is generally designed and sized to supply certain DC- and/or AC electrical loads.

System sizing is the process of evaluating the adequate voltage and current ratings for each component of the photovoltaic system to meet the electric demand at the facility/home and at the same time calculating the total price of the entire system from the design phase to the fully functional system.