System type based on grid reliability

System Types

(in order of increasing system cost)

Supplementary

Photo Voltaic DC Power is converted to AC Power and fed directly to the load Excess power is then fed back into the grid. (if allowed)

Advantages:
• Self consumption of PV power
• Lower cost
• Highest efficiency
• Ease of installation
• Low maintenance
Disadvantages:
• No backup
• Grid off, PV off

Supplementary with backup Genset

This is the same as supplementary but with standby generator connected. When grid is off, PV off. Generator starts up and provides AC reference to PV inverters. PV inverters synchronize and provide power to the load. Mini fuel saver concept since generator does not take full load.

Limitation: PV Power < 20% of Gen Power without PV control. PV Power > 20% of Gen Power with PV control

Advantages:
• Same as supplementary
• PV operational when grid disconnects
Disadvantages:
• None other than fuel and refilling required

Hybrid System

PV 1+2 Power is supplementary and fully consumed by the load. When grid is live then PV 1+2 is in supplementary mode. Portion of the PV array is dedicated to the backup facility (PV2). When grid fails then PV 1 disconnects and PV 2 remains operational. AC reference is received from battery inverter/chargers.

Limitation (hence the splitting of the PV array):

• The amount of PV power that can be connected to the battery inverter/charger.
• Victron: PV power = Battery inverter power
• SMA: 2 x PV power = Battery inverter power

PV 1 is optional (dependent on required PV plant size).

Advantages:
• Backup facility due to batteries and inverter/charger.
• Essential circuits remain operational.
• System in supplementary mode in grid connected scenario.
Disadvantages:
• Non essential circuits disconnected when grid fails.
• Increased Cost due to battery component.
• Battery replacement timeframe of 4-15 years depending on how the battery system was designed and/or configured.

Off-grid System

Two modes:

AC coupled – through the use of grid-tie PV inverters. Highest efficiency of 97% since PV power is directly consumed by the load. This system is best used for high daytime loads.

DC coupled – through the use of charge controllers and low efficiency of 78% since PV power is used to charge the batteries and then inverted to the load. (recommended for high night time loads).

System sizing is critical since there is no grid assistance.

Advantages:
• Independence of municipal grid.
• Immune to utility tariff increases.
• Backup facility due to batteries and inverter/charger.
• Essential and non essential circuits remain operational.
Disadvantages:
• Much higher cost since batteries have to cater for full load. (No grid assistance). • Battery replacement timeframe of 4-15 years depending on how the battery system was designed/configured.

Helping build a sustainable future

We aim to facilitate and drive mass market adoption of renewable energy, thereby solving economic and environmental issues caused by fossil based power.

Just imagine... no more load shedding, no more power outages and all of this for less cost.

Your power is in your hands.

gps@greenpowersimplified.africa