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Description

Description of On- and Off-Grid Small Wind Energy Systems

If your facility happens to be on or near an existing electricity grid, you will have to decide whether or not you want your small wind turbine to be connected to the grid. Below is a comparison of on- and off-grid applications - this will give you an idea of the typical applications for each system. After this, you can look at the practicality of either option, as well as the pros and cons.

On-Grid Applications       

• The wind turbine and the load it serves (e.g. a house) are connected to a large, external electricity distribution or transmission grid. This can be a national grid or one that supplies an isolated community, mining complex, or other large load.
• The house or other load typically receives its electricity from the wind turbine when wind is available and from the grid when supplemental/backup power is needed.
• Small wind turbines above 30 kW commonly use induction generators that produce grid-compatible AC electricity and can be connected to the grid directly, without inverters (although other power conditioning equipment such as step-up transformers may be required).  Such turbines usually need to be connected to the grid in order to operate, since the generator relies on the grid for field excitation and frequency synchronization.
• To connect a renewable energy system to the grid, you must adhere to interconnection guidelines and a net metering agreement.

Off-Grid Applications

• The wind turbine and the load it serves (e.g. a house) are not connected to a larger electrical network.
• Since wind is usually an intermittent energy resource, off-grid systems are typically installed with some form of energy storage device (usually a bank of lead-acid batteries) that stores excess wind-generated electricity and supplies it to the load (e.g. house) when there is insufficient wind.  Battery systems can supply reserve power when energy demand exceeds that delivered by the wind turbine, such as during calm spells.
• DC electricity from turbines can be used directly for battery charging but is not suitable for loads that require alternating current (AC), such as common household appliances.  In these cases, an inverter is required to convert the DC power to AC. Inverters are becoming more common in off-grid power installations and can provide AC electricity of the same quality as grid power.