Solar PV Systems

Solar PV Systems use sunlight to generate electricity for your domestic use.  It either stores excess electricity in batteries for later use or fed into the electricity grid to reduce your electricity bill.

For off-grid systems, the solar panel converts sunlight into DC electricity to charge the battery. This DC electricity is fed to the battery via a solar regulator which ensures the battery is charged properly and not damaged. DC appliances can be powered directly from the battery, but AC appliances require an inverter to convert the DC electricity into 240 Volt AC power. 

Solar Modules

Solar panels are classified according to their rated power output in Watts. This rating is the amount of power the solar panel would be expected to produce in 1 peak sun hour. Different geographical locations receive different quantities of average peak sun hours per day. In Australia, the figures range from as low as 3 in Tasmania to over 6 in areas of QLD, NT and WA.

As an example, in areas of the Hunter Valley in NSW, the yearly average is around 5.6. The monthly figures for this area range from below 4.0 in June to above 6.5 in December. This means that an 80W solar panel would ideally produce around 320W per day in June and around 520W per day in December, but based on the average figure of 5.6, it would produce a yearly average of around 450W per day

Solar panels can be wired in series or in parallel to increase voltage or current respectively. The rated terminal voltage of a 12 Volt solar panel is usually around 17.0 Volts, but through the use of a regulator, this voltage is reduced to around 13 to 15 Volts as required for battery charging.

Solar panel output is affected by the cell operating temperature. Panels are rated at a nominal temperature of 25 degrees Celcius. The output of a typical solar panel can be expected to vary by 2.5% for every 5 degrees variation in temperature. As the temperature increases, the output decreases. With this in mind, it is worth noting that, if the panels are very cool due to cloud cover, and the sun bursts through the cloud, it is possible to exceed the rated output of the panel. Keep this in mind when sizing your solar regulator.

Solar Regulators

The purpose of solar regulators, or charge controllers as they are also called, is to regulate the current from the solar panels to prevent the batteries from overcharging. Overcharging causes gassing and loss of electrolyte resulting in damage to the batteries.

A solar regulator is used to sense when the batteries are fully charged and to stop, or decrease, the amount of current flowing to the battery.

Most solar regulators also include a Low Voltage Disconnect feature, which will switch off the supply to the load if the battery voltage falls below the cut-off voltage. This prevents the battery from permanent damage and reduced life expectancy.

A solar regulator also prevents the battery from backfeeding into the solar panel at night and, hence, flattening the battery.

Solar regulators are rated by the amount of current they can receive from the solar panels.

 Inverters

An inverter is a device which converts the DC power in a battery to 240V AC electricity. Inverters come in two basic output designs, pure sine wave and modified sine wave (squarewave).

Most AC devices will work fine on the modified sinewave inverter, but there are some exceptions. Devices such as laser printers can be damaged when run on modified sinewave power. Motors and power supplies usually run warmer and less efficiently, and some things, like fans, amplifiers, and cheap fluorescent lights, give off an audible buzz on modified sinewave power. However, modified sinewave inverters make the conversion from DC to AC very efficiently, and they are relatively inexpensive.

Pure sine wave inverters provide AC power that is virtually identical to, and often cleaner than, power from the grid.

Inverters are generally rated by the amount of AC power they can supply continuously. Manufacturers generally also provide 5 second and 1/2 hour surge figures. The surge figures give an idea of how much power can be supplied by the inverter for 5 seconds and 1/2 an hour before the inverter's overload protection trips and cuts the power.

Choosing your Solar System

Factors to consider:

• Your electricity demand—how much you use. The more electricity you demand, the larger the system and the greater the cost
   
• Your budget—how much are you prepared to invest? Your budget may create limits on the size of the system
   
• Your location—whether the mains electricity grid is available and, if so, how much would it cost to bring power out to your property and pay for ongoing maintenance of
  poles and cables on your property
   
• Aspect—there needs to be sufficient space on your roof for the mounting of north-facing modules
   
• Rebates—Commonwealth and/or state government rebates provide an incentive to householders to invest in solar. However these are subject to change from time to time.  Please check with Sivcorp Solar or the Australian Greenhouse Office.

 Sivcorp Solar only uses BCSC Accredited designers and installers so you can be confident  to obtain your full rebates.