What are the different solar systems available?
There are three types of systems available in the market, On-Grid Systems, On-Grid 'Hybrid' Systems with battery back-up and completely Off-Grid Systems.
1) On-Grid Solar Power Systems
The solar power system is connected to an existing power grid. This is the most common set-up. Free solar power is first used in the home and any excess exported to the grid. Your power retailer will pay you a nominal amount, in the order of 7c to 20c per KWh for a households excess power. Electricity is imported from the grid when solar generation is not sufficient or not operating (eg. at night).
On-Grid solar power systems use inverters to convert the electricity produced by solar panels to the same voltage and frequency as grid power and to synchronise the systems. The system also incorporates safety devices which allow solar systems to be isolated automatically if the grid is shut down for safety or maintenance purposes.
On-Grid systems constantly monitor the voltage and frequency of the grid and specific standards exist to ensure that solar systems comply with this in Australia and around the world. This is one reason why choosing a high quality inverter is important. Lower quality inverters can suffer “trip-outs” if the grid power is varying and therefore your solar system temporarily shuts down. Higher quality solar inverters are better able to cope with grid power fluctuations and keep you connected for longer periods, giving you a better solar power output.
One implication of this type of system is that if there is a grid blackout, your solar system will not be able to supply your home with electricity, unless you have a battery with grid back-up.
2) On-Grid Hybrid Solar Power with Battery & Blackout Support
On-Grid solar systems with batteries are gaining popularity. They are a combination of an On-Grid system, with more sophisticated electronic control equipment and storage, typically in the form of on-site lithium batteries.
These systems, sometimes called 'hybrid' are designed to save excess solar power generated during the day for use during the night. These systems also supply power into the house during the day, for example when demand for power is 3kw and the solar panels are only producing 2kw the battery will jump in and supply the 1kw shortfall. These systems can be optimised to 'Time of Use' power tariffs to offset the most expensive peak period consumption. The battery capacity is generally not enough to go off the grid and the hybrid inverter and control systems are generally not robust or powerful enough to cope with high peaks in demand over 5kw which are normal in a typical home.
Most solar battery packages will have the facility to give the household some blackout power. Consumers must specifically request this is quoted as it involves extra wiring and equipment. In the event of a blackout or poor grid power quality, the solar battery system can disconnect the home from the grid, then reactivate your solar system to provide power via dedicated circuits. Note that these systems cannot run all appliances simultaneously as would be possible with the grid, so consumers need to specify to their solar installer which circuits they want e.g. fridges, lighting, important medical equipment etc.
3) Off-Grid Systems
Off-Grid systems are used where grid power is unavailable such as remote farms or homes, telecommunications sites, water pumping (see sample photo) or other remote industrial facilities.
Off-Grid systems need to be very carefully designed to match energy generation to energy demand and require a detailed energy audit and site specific assessment to work effectively.
Off-Grid systems use batteries to store solar energy so it is available to be used 24 hours a day and often include a back-up generator for unusually high energy demands or long periods of low solar irradiation. Whilst it is possible to operate such systems without a back-up generator, great care must be taken to ensure the energy demand is matched to the amount of energy stored in the batteries.
Off -Grid solar power have been particularly useful in third world countries and remote Australia. Many remote homesteads, farms and industrial sites use solar electricity in Australia as a cost effective and reliable alternative to diesel generation for household electricity, water pumping and agricultural uses. Solar electricity can significantly reduce the difficulties associated with getting fuel, maintaining complex generators and are virtually silent.