Wind Power – is it the Right Choice for You? 0

3.5 kW Grid-tied Wind Turbine

3.5 kW Grid-tied Wind Turbine

Wind.  It can be a cooling breeze on a stiflingly hot day, a devastating natural disaster or it can be a source of power.

Wind turbines, which convert the energy in the wind to usable power, are becoming popular with homeowners who want to produce their own renewable power and reduce their electrical bills.

Installing our First Wind Turbine

Installing our First Wind Turbine

We bought and installed our first wind turbine to help power our experimental off-grid solar and wind powered home.  At night it’s actually soothing to hear the wind howling around the house and know that our batteries are charging up!  But, when looking at investing in a turbine, don’t throw caution to the wind. We’ve learned a lot about wind conditions and power production – and a lot more than we wanted to about wind turbine repair and maintenance.

Before you buy a wind turbine, look past the glowing promises of wind turbine manufacturers and see if you have the right wind conditions and the right product to make the most of your investment.

How Much Wind is Enough?

You know you have wind – you know because all too often it’s a nuisance or downright destructive.  But does this mean you have enough wind to produce a useful amount of power with a wind turbine?

Wind turbines have a cut-in wind speed, usually about 7 mph, below which the turbine will turn but will not produce any power.  Seven miles per hour is a pretty stiff breeze.  Once there’s enough wind to start producing, the output increases very rapidly with increasing wind speed.  For example, when the wind speed doubles the power output goes up 8 times – up to the maximum rated output of the turbine.  This means that winds just above the cut-in wind speed don’t really produce very much – you need wind speeds upwards of 12 mph for worthwhile power production.

The power production increases until you reach the rated wind speed of the turbine, where it is producing its maximum power.  For example, a 1.5 kW turbine will produce 1.5 kW at its rated speed of 25 mph.  Higher winds will not produce more power.

Whisper 200 wind turbine furling at high wind speeds

Whisper 200 wind turbine furling at high wind speeds

Furling

Many small wind turbines for home use will “furl” when the winds are higher than the rated speed.  Furling turns the blades out of the wind to protect the turbine but still produce some power.

What Power Output Can You Expect?

Wind turbine manufacturers usually provide spec sheets that list the expected output (in kWh) at various average annual wind speeds.  The output they show makes some assumptions that will probably not apply to your particular site.  It is assumed that the surrounding terrain is flat and at room temperature and sea level.  Altitude, temperature and especially features in the terrain can make a huge difference to the actual output.

Effects of Terrain and Tower Height

Hills, trees and bush, buildings and other obstructions will create turbulence in the wind and reduce the amount of output you receive.  If you live on a farm or acreage you will probably still be able to get a reasonable output, even with rolling hills and shelterbelts, by putting the turbine on a minimum 50′ tower and keeping it as far as possible from trees and buildings.  Typically, rolling terrain with trees and bush will reduce the power output by up to 50% from the manufacturer’s specifications.

In towns and cities, small wind turbines generally aren’t feasible and are often prohibited by zoning restrictions.

Wind Turbine on 70' Tower with flat terrain

Wind Turbine on 70' Tower with flat terrain

All wind turbines must be mounted on a tower so they will be, as much as possible, above the turbulence created by the terrain.  The general recommendation is that the turbine should be at least 30′ above any surrounding obstructions.

Power output increases with height above the ground, so the higher the tower the better – remembering that you still have to put it up and will probably need to take it down occasionally for repair and maintenance.

Most small wind turbines for residential applications are mounted on tower heights of 40′ to 70′.  This puts the turbine above much of the turbulence but still makes it possible to raise and lower the tower with a truck or a winch system.

Some Pros and Cons

If you have a good wind resource and suitable terrain you can get excellent power production from a good wind turbine.  When the wind blows and others are complaining you will be saying “Yes! I’m getting power!”

However, it is those same conditions that can also give you problems.  Wind turbines have moving parts – blades, bearings, magnets, brushes – and they are expected to operate in some ferocious conditions.  They are expected to produce power at 30 degrees below zero and colder, during blizzards, freezing rain and sand storms.

Wear and tear is unavoidable but some turbines are more robust than others.  It’s a good idea to read reviews on various turbines that have been operating in your area and climate conditions to help you make your decision.  We have used two different brands of turbine.  Both have had good features but the locally designed product is more robust in our harsh climate and our repair experience is no longer so much in demand.

 

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