WIND electric systems capacity & efficiency

What's usually called small wind electric systems aren't as small as their name suggests; even a small system of 1 kW (Kilowatt) is a tall device, with a large diameter, typically installed in a rural area. Pumping water
Small wind turbine systems are good alternatives to traditional mechanical windmills. They are more versatile and effective and do not have to be located above the well.

Do not confuse these small wind-powered systems with micro-wind and wind-urban systems.

Small wind electric systems

The so called micro-wind electric systems (below 1 kW per hour) are mostly used to charge batteries and to supply power for a variety of applications: recreational vehicles, particularly sailboats, telecommunication dishes, measurement instruments, radar and telecom devices and security and electronic systems. Number of wind turbines
A single larger turbine is a better choice than two smaller units: it’s cheaper and requires lower installation and maintenance costs.

Small wind power systems are more powerful devices, with a wide power range: between 1 Kwh (kilowatt hour) and 100 Kwh, though most are in the 5-10 kWh range. They are mainly used in rural areas, to provide power for farming and residential purposes. They can be stand-alone or grid-connected.

Urban wind electric turbine systems are intended to provide electricity for general purposes, in urban areas. They can be mast-mounted or roof mounted in buildings. They are becoming common, but their usefulness is highly questionable. See, for details: Urban Small Wind Power Systems.
Before installing a small wind power system in your property you should reduce your electricity consumption as much as possible through conservation measures: high levels of insulation, energy-efficient windows, appliances and lighting...

The rated capacity and the average wind speed

The electricity generated by a small wind turbine depends largely on...

1) the average wind speed in your site
2) the rated capacity of the turbine…

Wind turbine systems vary a lot in their rated capacity. A capacity of 1 kW means it can produce about 1 kW of electricity per hour for a specific wind speed (typically 25-35 miles per second (11-15 meter per second)).

Be aware, anyway. The rated capacity doesn't mean a lot in the real world.

On average, the real output is something between 10% and 40% of the rated capacity.

The reason? The wind rarely blows at the constant wind speed considered by manufacturers; there are many periods when it doesn't blow at all, or blows at a slower speed, or is inconsistent.

In other words: typically, a 1kW wind turbine will produce per day between 1 kW x 24 hours x 10% and 1 kW x 24 hours x 40%, that is, an output between 2,4 kW and 9,6 kW/day (see table below), depending on the average wind speed in the area.

If the average wind speed in your property is higher, than the electrical output will be closer to the upper values listed in table below...

table small wind capactity

Left column: Small wind turbine rated capacity, in Kilowatts per hour.
10%, 40%: The real electrical output: typically between 10% and 40% of the rated capacity.
The rated capacity of a small wind turbine system is theoretical. It assumes wind speeds – often between 24 mph (10.5 m/s) and 36 mph (16 m/s) - that only exist for short periods of time. The real output is often estimated to 10 to 40% of the rated capacity…

Wind maps

Wind maps help assess the wind potential of your site.
Llinks to help you in your search:

The U.S. Department of Energy wind maps includes an impressive amount of data for each state. SeeU.S. Department of Energy wind data maps and resources and National Renewable Energy Laboratory
The Canadian Wind Energy Atlas – EOLE Project from the Environment Canada (RPN.
See: Canadian Wind Energy Atlas
European Wind Energy Maps and data
Some references
- a 1.5 kWh small wind turbine can meet power needs of about 300 kW per month, in areas with an annual average wind speed of 14 miles per hour (6.3 meters per second).
- Typical output of residential wind powered systems: 5 and 15 kWh;
- Typical output of small community wind powered systems: 10-50 kW;
- Agricultural, industrial and commercial applications: 20 kW or more;
- Minimal average wind speed for cost-effectiveness: 11-13 miles per hour (5-6 mps; meters per second). 
European Meteorological Institutes.
European Wind Resources Map
Australian Bureau of Meteorology wind data.

Airports & Wind Data

Airports near your area can also help you. They have extensive data on wind patterns...

Just make sure that the wind conditions in your site match the general patterns. Forests, clearings, hills, gullies, buildings or even fences and small obstacles can deeply affect the wind speed in your property, or parts of it.

See, on these issues:
Wind Towers Height and Types
Small Wind Power Systems Location




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