What are the different solar systems available?
There are a number of different types of systems available in the market. The major ones - On Grid Systems, Off Grid Systems and Combination Systems, are detailed below:
1) On Grid Solar Power System
The most common type of solar system - On Grid Solar Power System: This is where solar electricity is connected to an existing grid power supply and is the most common set up. Here free solar power is as first used first option. Electricity is imported from the grid when solar generation is not sufficient or operating (nb like at night). Conversely, solar power exported to the grid when there is more supply than is used (nb middle of day with noone at home). Your power retailer will then pay you a nominal amount at their cost to manufacture, in the order of 4c to 8c per kW.
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 together. 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, despite the fact that the solar panels may still be generating energy, unless you have an On Grid Support system which has storage battery support.
2) On Grid Solar Power System with storage battery support
Although not widely used yet, On Grid Support systems 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.
The battery capacity is not enough to go off the Grid. It is designed for daily use when solar power generation fails to meet demand or at night. In doing so it reduces a household's reliance on expensive Grid power. Where a home is on Time of Use metering the store power can be used to offset the most expensive Peak Period consumption.
In the event of a blackout or poor grid power quality, an On Grid support system can disconnect your home from the grid, then reactivate your solar system to provide power via dedicated circuits to cover computers and fridges via the batteries.
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.
Telstra was one of the early users of off grid solar power systems in Australia using it for remote repeaters in place of generators; thousands of systems have been deployed across Australia stretching right back to the mid 1970’s and the Australia’s telephone system in remote locations still utilises solar electricity.
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.
Off Grid solar systems are used in a huge variety of applications and are often life changing experiences for people in areas where little or no electricity was previously available.
Some of the applications in remote locations include:
- Power for villages, homes and farms
- Water pumping
- Water purification
- Vaccine refrigeration
- Electric fences
- Industrial applications
- Disaster relief
4) Combined Systems
These are not commonly available in Australia due to the availability of regular electricity supply and electricity regulations. This type of solar systems are more common in developing nations where due to erratic supply of electricity these type of solar power systems ensure that basic requirements such as lights or refrigerators continue to work.
In these systems the solar power is connected to the grid through a battery back-up system. These batteries can be charged through the solar panels or from the grid. In case of electrical failure the batteries then power the home.