The 3 Main Configurations of PV
An off grid PV solution is required when there is no power available from a electricity supplier. Either the main supply where the power will be fed from is a great distance or the installation of an electrical circuit is impossible. The other side of this system type is where a person would prefer to not rely on the electricity supplier. This system can be configured in a few ways:
- Off grid entirely – this would be when you have the entire house, lodge or work place running off this PV system. The night time power requirement would have to be supplied by batteries and the main loads on the system drawn during the day.
- Off grid segmented circuits – in an established building where there is power availalbe, certain circuits within the DB board can be supplied by the solar Off-Grid system. Typically a home owner will separate the lights, TV and components, fridge, deep freezer and the security system. This ensures that when there is power outages these circuits are not affected.
GETTING STARTED – your Off-Grid system
So how do you configure an Off-Grid PV System
The installation of a segmented circuit system uses the same equipment as the completely off grid system. The only configuration that will change will be within the Distribution board where the circuits are separated.
Systems designed to feed or subsidise the grid.
GETTING STARTED – your Grid-Tie system
So how do you configure a Grid-Tie System
The grid tie system uses a highly intelligent inverter to manufacture AC power which is suitable to power your internal grid as well as the national grid. This system takes strings of PV modules to series which allows the Wattage and voltage of these modules to be compoundly increased. Once the inverter has the minimal starting current it begins to push the power into your internal electrical system. Anything over 3kw should be connected in the distribution box. Electricity is much like water, it takes the path of least resistance and therefore the power is first taken from the PV system and the national power grid supplements the difference you might need.
In cases where you are generating more power than you are consuming, the electricity will be fed back into the grid at the same frequency as the national grid power.This power will reverse your meter in many cases.Reversal of meters is not advised as this can cause confusion with your local municipality. However, Eskom has started implementing a buy back system for these grid-tie systems where each unit of excess electricty fed back into the grid will be paid for.
The estimated price per KW paid to you by Eskom is 46c. Large scale installations are a must for corporate and industrial companies. SARS has a scheme where the capital outlay on a system can be deducted from your provisional income tax in a 50:30:20 process over 3 years. Also the VAT is fully claimable up front.
Simply the most agronomical PV system configuration to date.
So how do you configure a Grid-Interactive System
This system configuration is much like the grid tie system in that it can feed the grid internally and externally with excess power generated as well as draw from the grid when required.
The difference is that this is an off grid system at heart, where the inverter will charge a battery bank and allow the home or business to use this stored energy once the sun has set first.
If there is not enough stored power and the batteries are depleted then the national grid will kick in to gear with an uninterrupted power supply. This is the reverse of a UPS. During the day the excess power, after charging the battery bank and supplying the internal grid requirement, will be fed back into the national grid. These unis will either turn the meter backwards or in time generate a cash rebate from your power supplier.
The benefit of this system is that you can go off the grid in theory and still have Eskom power as a back up, this allows you maximum savings while quality of living will never be subsidised.