Basically a solar roof system is a system to convert solar energy to electricity for residential or industrial uses and usually it’s mounted on the roof of a house or building. The primary components that consist of a solar roof are the following:
1. Photovoltaic Panels (PV Array)
2. DC Disconnect
4. AC Disconnect
6. Battery bank
Photovoltaic (PV) panels are a component to convert sunlight energy to direct current (DC) energy. PV panels are one of two main technologies (provide the link to the previous article) to achieve this conversion. PV panels can be rated in watts and the rating can help to determine how many panels one need to meet his or her electrical needs. Multiple modules (also called array) may be needed to provide sufficient energy.
DC Disconnect is a safety device to prevent electrical attack from the electricity output from PV panels. Normally the electricity generated by PV panels is fed to electrical appliance or grid through an inverter. When maintenance or troubleshooting is needed, the DC disconnect is required to interrupt the flow of electricity from the PV panel.
Inverter is a power electronics device to transfer the DC electricity produced by PV panels into the alternating current (AC) electricity. Most home appliance is compatible only with AC electricity and the power grid is also formed as AC electricity. If the electricity produced by PV panels is tied to the grid, then grid-tied inverters are required which not only convert DC to AC but also synchronize the PV electricity with the grid and allow the electricity from PV panels to flow back to the utility grid.
AC Disconnect or AC Breaker Panel can be found at most houses with and without solar roof system. The AC Breaker Panel is usually mounted on a wall such as in basement, garage or exterior of the house. The inverter will be wired to the AC breaker panel before the PV electricity flows to the grid or home appliance. Same as the DC disconnect, the AC disconnect (AC Breaker Panel) enables the electricity to be disconnected for servicing and protect the electricity equipment against overheating and electrical fires.
Meter is needed to measure the amount of energy from the grid being consumed by the household, measured in kilowatt hour (kWh). For households with solar roof system installed, a bidirectional meter may be desired, to measure not only the energy received from the utility grid, but also to measure unused energy produced by PV panels that is fed back to utility. Such bidirectional meter can be also used to provide information on power usage profile to help determine the need for additional PV panels.
Battery Bank is optional to a solar roof system. Battery bank can be used to store the electricity produced by solar panels when it’s not needed. Battery bank also serves a source to provide constant power for home appliance such as in cloudy days when the sun doesn’t shine. Battery bank may not be needed if the house is still tied to the utility grid.