Turbines with Power Ratings of 300 Watts to 1 kW

Of the size categories considered, these wind turbines present the greatest variety in terms of technologies and designs. These machines are usually mass-produced with a high degree of component integration, and are therefore relatively inexpensive compared with larger turbines. They are typically sold as off-the-shelf consumer products in retail stores or through on-line distributors, often alongside other energy systems such as solar photovoltaic panels. They are available with power ratings that span most of the 300-1000 Watt range, typically in increments of 100 W (i.e. 300, 400, 500, etc.). The relatively high sales volume of these units makes for a relatively large number of competing manufacturers and gives product designers significant leeway in trying unconventional shapes and configurations. Nevertheless, the most common designs are three-bladed, up-wind horizontal axis machines that use direct drive, permanent magnet alternators and mechanical furling for overspeed control. The most popular turbines in this size range are frequently manufactured in volume at mass production facilities outside North America.

These machines operate at variable speeds and thus produce variable voltage and variable frequency AC power, which is then typically converted to DC by a rectifier circuit. The actual output of these turbines is thus usually DC electricity, which is most commonly used to charge batteries. Another significant characteristic of these systems is that they can often be simply mounted on a pipe of 2” diameter, or smaller. If guyed, this pipe can serve as the tower. This makes for relatively simple and sometimes inexpensive tower installations that can often be accomplished on a “do-it-yourself” basis by the owner.

Maintenance requirements tend to be minimal due to the small size and integrated design (i.e. minimum of moving parts), particularly for units in the lower part of the range (300-500 W). In fact, many such turbines are advertised as ‘maintenance free’. When such units fail, they are intended to be sent back to the manufacturer or dealer for repair or replacement, as is the case with many modern consumer products. The larger units (500-1000 W) may require minimally more maintenance and occasional on-site repair calls (for bearings, slip-ring or controller failures, blade damage etc.).

The lifetime of mini wind turbines is difficult to determine due to the wide variety of models on the market, the lack of standard durability tests and lack of surveyed field performance data. The longest warranties offered for such machines are for 5 years. A typical lifetime for these turbines, when operating in normal seasonal climates, is in the range of 10 to 15 years for the smaller units (300 to 500 Watts) and up to 20 years for the larger units (500 to 1000 Watts).  Turbines in extreme cold or coastal regions may have shorter lifetimes because of corrosion, temperature, and icing.

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