Stand-Alone PV Systems

Stand-alone PV systems are also called autonomous PV systems which are independent Photovoltaic systems. They are normally used in remote or isolated places where the electric supply from the power-grid is unavailable or not available at a reasonable cost. Examples for such an application are mountain huts or remote cabins, isolated irrigation pumps, emergency telephones, isolated navigational buoy, traffic signs, boats, camper vans, etc. They are suitable for users with limited power need.

Difference with the Grid-tied System

Stand-alone PV systems often don’t require an inverter like the grid-tied systems when being used for particular cases. Since PV systems, whether grid-tied or stand-alone, produce electricity at the first hand in the direct current type, they require an inverter if you need them to be converted into alternating current for supplying to the grid or running machinery which require AC (alternating current). But some devices like water pumps, cooling fans, and filament bulbs require DC (direct current). So, when connected with a Stand-alone PV system, they can directly get the power from the PV without the requirement of an inverter.

Ref: www.seners.gr

Advantages

Stand-alone PV systems have got a number of advantages in comparison with other sources of energy.

• First of all, you don’t need any fuel to run the power generation process. The sunshine is abundant in most of the places on earth at least for a few hours every day.
• This system is completely nature-friendly and does not produce any waste or bi-product.
• You can generate electricity where and when you need. It could be on a hilltop, on the roof of your tree-house, on your boat and in all imaginable places the sun can reach.
• The system is very simple, compact and modular. There is no complex wiring, control system or infra-structure required.
• The Stand-alone PV system is easy and quick to install. A whole system of 500 watts may weigh less than 70 kilograms. You can dismantle them easily, transport and install in a different location in a few hours.
• The lifespan of a Stand-alone PV system is quite long and requires minimum maintenance. There being no moving parts, wear and tear of the device is almost negligible. The system is almost maintenance free requiring occasional inspection and cleaning only.
• Finally, there is almost no operating cost as the system is completely automatic and suitable for unmanned operation.

As the Stand-alone PV systems can produce electricity only during daytime, during night or in low-lit winter days, the power has to be supplied from an alternate source.

Energy can be stored in batteries but there are practical limitations to this – for example, to store energy produced in the summer for use in winter will require a very large battery bank.

In places where winter allows very little sunshine, the Stand-alone PV system can be bridged with a hybrid system where an alternate source of energy like wind-turbine or bio-gas generator is available.