PV Systems
Photo Voltaic Systems
PV Domestic Systems
Grid-Tie Power Systems (220 / 380 Volt)
DC power generated from the PV modules is converted from a fluctuating DC voltage to 220V grid connected power.
Grid systems do not store energy and thus do not have backup. If grid failure occurs no power will be produced from the system. Grid systems are easy to monitor and measure performance as there are no storage losses.
Grid inverters are very efficient and very few losses will occur in high quality grid systems.
Advantages
Most cost effective PV solution
No energy storage losses
Easy to monitor system production and performance
Very high conversion efficiencies
Simple installation
Disadvantages
No backup
Island Power Systems (220 / 380 Volt)
Energy generated from the PV modules is used by inverters to produce 220Vac power.
Surplus power is stored in batteries to ensure power availability when usage exceeds PV production. Battery storage is sized in order to achieve about 3 days autonomy.
As the batteries will be working on a daily basis, cyclic batteries should ideally be used.
True hybrid inverters have the ability to select how it will interact with the grid supply. If grid supply is in the form of the national grid, a true hybrid inverter can be programmed to ignore the dedicated supply and only accept it due to low battery or the load exceeding inverter specification.
In the case of generator supply it can manage the generator and can be programmed
not to overdraw the generator. True hybrid inverters are expandable in parallel and three phase.
Advantages
Grid independence
Expandable into parallel or three phase
Reliable power supply with grid/generator backup
Disadvantages
Batteries will be cycling on a daily basis
Once battery capacity is reached power generated by the PV system is dissipated
Battery capacity needs to ensure autonomy for about 3 days
Multi Hybrid Systems
This system consists of 2 alternative energy systems working together.
An island system secures backup power to the “essential” appliances. A Grid-connected system feeds power to both the essential and non-essential appliances.
The topology of a multi hybrid system allows it to function as a full island system under grid failure, ensuring an unlimited power supply to all the essentials.
As the grid-connected PV system is usually sized to serve both the essential and non-essential appliances, it is well oversized in case of grid failure to supply the essential appliances.
As the batteries will only cycle in case of grid failure, standby batteries can be used that can achieve similar life to that of cyclic batteries but are far more cost effective.
Battery backup is then only sized for essential applications and therefore significantly less than typical off-grid applications.
Advantages
Reliable supply for essential appliances
Batteries will not be cycling if grid power is available
Battery backup is only for essential equipment resulting in a reduced battery bank
Expandable in both the island and grid capacities
Surplus power is fed back into the grid and not dissipated as in island systems
Essential appliances can be selected and added
Standby batteries in this application can achieve similar life to cyclic batteries in a cyclic application
Disadvantages
Only partial grid-independence is achieved
