Wind power is an excellent weapon for fighting climate change because wind generation produces no carbon emissions at all. When you consider that every unit of energy generated by wind, is a unit of energy free of carbon pollution, wind makes sense. Producing just 10 per cent of electricity from renewables could cut carbon emissions by 2.5 million tonnes a year.
Small wind-electric systems can provide electricity to remote sites, or to houses that are also connected to the utility grid. But the prices! A small turbine can cost $US 2,000! A medium turbine $3,000! A large one can cost $8,500 – and that’s without the rest of the equipment you will need, and installation costs! Although wind systems require some attention, if you build a strong system, following a proven design, wind-electric systems make great economic and environmental sense.
How much FREE electricity will I get? There seems to be a myth that wind power produces little power. Strange, when a 1.8-megawatt turbine produces enough power for 1,000 homes.
More realistically for the DIY wind turbine maker, a small wind turbine, with a rotor diameter of 7 feet (2.1 m), and a swept area of 38.5 square feet (3.6 m2) will produce, per month, at average wind speeds of 10 mph – 80 KWH! This is enough power for a low-energy home, yacht, or business. A medium sized wind turbine with a rotor diameter of 10 feet (3 m) and a swept area of 79 square feet (7.3 m2) will produce, per month, at average wind speeds of 10 mph – 130 KWH! This would be suitable for a medium-energy home, business, or school. A large wind turbine with a rotor diameter of 12.5 feet (3.8 m), and a swept area of 120 square feet (11.2 m2), will produce, per month, at average wind speeds of 10 mph – 230 KWH! This is for big energy consumers. A huge wind turbine with a rotor diameter of 56 feet (17 m), and a swept area of 2,462 square feet (229 m2) will produce, per month, at average wind speeds of 10 mph – 5,060 KWH! These power large farms, very high-energy businesses, villages, islands, and massive heating projects.
Smaller turbines can be built for boats, caravans, cabins, or where only a small amount of electricity is needed. But for significant amounts of energy, you need a large enough rotor, as this is the wind turbine’s ‘energy collector’. When sizing a wind-electric system, you don’t add windmills in as you need them, as you can with solar panels. Because wind is more cost effective as you increase in system size, most people put up only one wind turbine, big enough to significantly slash their electric bills, or to fulfill all of their energy requirements for the foreseeable future.
System Components: The turbine is only one component of a wind-electric system, and very often is not even the most expensive component. You need all of the necessary components to have a functional system. Plan ahead to buy quality components properly matched to each other and to your energy use.
A complete wind-electric system includes: • Turbine—blades + hub = “rotor,” which is the “collector” of the system. • Tower—supports the turbine, getting it up out of the turbulent zone created by trees and buildings, and exposes the turbine to more wind • Wiring and conduit—carries the electricity down the tower and to power-conditioning equipment • Controller/Electronics—controls charging of battery or input to inverter • Batteries—used for storage in off-grid systems or grid-tied systems with battery backup • Inverter—converts direct current (DC) electricity from batteries or rectifier to alternating current (AC) for home use or “storage” on the utility grid • Metering—allows user to understand and manage system operation.
Small wind turbine: needs a controller or inverter, and is suitable for battery less grid-tie or 12, 24, 48 VDC battery charging
Medium sized: needs a controller or inverter, and is used for charging 12, 24, 48 VDC batteries Large: needs controller, dump load, and inverter. Suitable for battery less grid-tie or charging 48 VDC battery.
Huge: suitable for battery less grid-tie
How does a wind turbine actually produce electricity? The rotating blades convert the wind’s kinetic energy into rotation in a shaft. The rotating shaft turns an alternator, which makes electricity. The electricity is transmitted through wiring, down the tower, to batteries, or an inverter. The blades are designed to intercept wind and capture its energy. Most modern wind generators have three blades, to compromise between the highest efficiency possible (one blade) and balance (multiple blades). The blades must turn to face the wind, so a yaw bearing allows the wind turbine to track the winds as they shift direction. A tail directs the rotor into the wind. In small-scale designs, the rotor is connected directly to the shaft of a permanent magnet alternator, which creates Alternating Current. This wild, three-phase electricity means that the voltage and frequency vary continuously with the wind speed. The AC output is used to either charge batteries or feed a grid-synchronous inverter, which turns it to steady, usable Direct Current. In small designs, the rotor is connected to the alternator, eliminating the need for gears. In larger systems, a gearbox is used to increase alternator speed from a slower turning rotor. A governing system limits the rotor rpm and generator output to protect the turbine from high winds. A shutdown mechanism is also useful to stop the machine during an extreme storm, or when you want to service the system. Understanding the Ratings Wind turbine rating is difficult because rated output is pegged to a particular wind speed, and different manufacturers compare different wind speeds to better promote their particular model. To understand the real power of wind, cube its speed. For example, 10 kph of wind, gives 10 x 10 x 10 = 1,000 watts. Or, a 10% increase in speed gives a 33% increase in power. This means that very small increases in wind speed create huge increases in power. This also means that a turbine that produces 1,000 watts at a wind speed of 28 mph, might produce only 125 watts at a wind speed of 14 mph – so half the wind produces 1/8 of the power. So ignore the rated peak output of a turbine, and look for the monthly (or annual) energy production you require (from your energy audit), estimated for the average wind speed at your site. After all, long-term energy is what you’re after, not peak output! If, for example, you know your home has 10 mph winds, and you need 400 KWH per month, you know what turbine to build. Knowing a turbine’s swept area may also help you calculate the annual energy output for the wind turbine. Jim Green at the National Renewable Energy Lab (NREL) developed a formula: annual energy output (AEO) in KWH = 0.01328 x rotor diameter (ft.) squared x average wind speed (mph) cubed. Easy!
Getting Started: Consider: Is it your aim to slash your bills, or to be completely independent? Are you going to be stand-alone, or will you still be connected to (and adding into/taking from) the grid? If you’re staying connected to the grid, will your local power company pay you for the electricity you generate?
First you need an energy audit of your home. Go to www.njcleanenergy.com for an accurate home energy audit, and great ideas on saving electricity and money. Sit down with your family, work out how many kilowatt-hours you all use, and find out where the waste is. But be realistic, reasonable, and think laterally. Just because you are now horrified at how much electricity your plasma TV uses, doesn’t mean the kids are never allowed to watch it. You may consider a smaller, more efficient TV for weekly use, and save the plasma for the weekend family movie.
Next, work out your location’s average wind speed, at a website like www.awea.org for the USA. When you know how much energy you need, and how much your wind will provide, you will be able to see the size of turbine you will need.
Now that you have a good idea of what you’re after, check out the DIY Wind Power Kits at EarthEnergyPlus.Com These kits have been selected with the DIY novice in mind, and include all the information you will need to build your own electricity-producing wind powerDetailed lists of the tools, parts, and where to get them. Video instructions you can play over and over. Great back-up from dedicated designers! Build your own wind power system this weekend, then sit back and watch your home-built wind generator turn a summer breeze into FREE electricity!
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