Grid connect photovoltaic solar power systems are the most cost effect way of using solar energy to power your home, school, office or commercial facility. They can be scaled up or down to meet anything from a portion of a household's power requirements to the power requirements of large industrial facilities.
In a grid connected photovoltaic solar power system, the solar panels generate high voltage DC power which is then fed through a grid connect inverter which converts it into grid compatible 240V AC power which feeds into your switchboard. During the day, the solar electricity feeds any power requirements of the building with any shortage drawn in from the grid. If the solar array is producing more power than the building is using, then the excess solar electricity is fed out through the switchboard into the grid, running your meter backwards. At night when there is no solar power being produced, electricity is drawn in from the grid as per usual.
Grid connected solar power systems have many advantages. These systems are much cheaper then the equivalent stand alone system as they do not include expensive battery banks and do not require the solar array to be oversized to account for the worst case (peak load) situation, as the grid will provide power during any period when PV system output is insufficient.
Also these systems are much easier to operate and maintain. The end user does not need to do anything to make the system work and will notice no change at all in their electricity supply. The only difference is solar panels on the roof, an inverter next to the switchboard and a lower electricity bill.
In the event of a blackout, the grid connect system is required to shut down. This is to avoid energising part of grid which would be a safety risk for line workers. This can be avoided by installing a battery backup system which allows the system to disconnect from the grid and run on battery power during a blackout. This does add to the cost significantly however as batteries, charge regulator and a second, stand alone inverter are required.
Since a grid connect system runs in parallel to the grid rather than separate to it, it is not necessary for the solar to provide all of your electricity requirements. You may wish to choose a system which covers a certain percentage of your electricity based on budget, available roof space or a range of other factors. The amount of electricity you use on average is shown on your electricity bill in kilowatt hours (kWh) per day. As a rule of thumb, an unshaded, north facing solar array will produce roughly 4kWh per kilowatt of capacity per day in Sydney. For example, a 2kW system will produce approximately 8kWh per day of electricity on average. This figure will be higher in more northerly locations and slightly lower further south.
The average household uses approximately 20kWh of electricity per day, although this can usually be reduced through energy efficiency measures to around 10-12kWh per day. This is what is referred to as a standard energy efficient household. Buildings which are designed to be energy efficient can reduce this amount of energy further still and can also be more comfortable to live in.