Wind Turbine Types and Benefits
With good, consistent wind flow, wind energy is one of the most economical forms of alternative energy available today… If your wind flow fluctuates, wind turbines can still be an excellent addition to a solar system, providing more consistent year-round power.Advances in wind turbine technology have focused on improving the efficiency of the components and reducing the number of moving parts, resulting in very reliable and effective turbine designs. Today, wind turbines are an essential part of a reliable renewable energy system.
- Wind Turbine Basics
- How Wind Turbines are Used
- Types of Wind Generators
- Using Wind Turbines in Alaska
- Benefits of Wind Energy
- Related Product Information
Essentially, a wind turbine (or: wind generator) is an alternator attached to a propeller. When the wind blows, the propeller turns and the alternator begins producing electricity. The design details that determine which turbines are best suited for various wind speeds get more involved, but all wind turbines operate in the same manner.
Installing a wind turbine is a bit more involved than installing solar panels, but they are still relatively easy to incorporate into your alternative energy system. The turbine needs to be mounted in an area free from obstructions to wind flow (nearby buildings, trees, etc.).
Some smaller turbines can be mounted to the rooftop of your house, but vibrations from the turbine may be transferred to the frame of the building. Rooftop turbine mounts often come with rubber vibration dampers to minimize this problem. As a general rule however, the higher in the air you can get your wind turbine the more effective it will be, so independent, guyed towers are the recommended mounting system. The wide variety of available tower heights and styles makes it much more likely you will find a mounting kit to suit your needs.
When installing the controls and wiring of a wind generator, it is important to understand two fundamental differences between wind turbines and solar panels:
Current Rectifiers: Solar panels produce direct current (DC) electricity required by power storage batteries, and can be connected directly to the battery bank without causing harm. Wind generators do not produce DC electricity, so a device called a "recitifier" is used to convert the turbine's output current to DC.
Some turbines have a rectifier built in. In most cases though, the rectifier is supplied as a separate component that must be installed between the wind turbine and the battery. Often, the rectifier is combined with a charge controller into one complete wind turbine control unit.
Load Diversion: Solar panels are "passive" electricity producers. Even though the sun is shining, they only produce eletricity when a charge is needed by the battery. Wind generators are "active" electricity producers. If the wind is blowing, they will produce current whether the battery bank needs the charge or not. In order to prevent damage to the wind turbine, all of the electricity it produces must be "used" in some way.
When the system batteries need charging current, they provide an electrical load to use the wind turbine's electricity. If the batteries are fully charged, the turbine's output must be "diverted" to another electrical load.
A load diverting charge controller regulates wind generator output so your batteries receive charging current when they need it, and any excess electricity generated by the wind turbine is diverted to an alternate load when the batteries are fully charged.
Some wind turbines have charge control features built-in, diverting their own excess current and allowing it to dissipate as heat through the wind turbine housing. In most turbine systems however, the charge controller is an external unit, and while DC rectifiers are always included as part of a basic wind turbine package, the load diverting controller may not be.
Some load-diverting charge controllers come with a heat-sink resistor to attach as the diversion load. When the batteries reach full charge, the load-diverting controller will simply send electricity to this resistor, where the energy will be released as heat. Some wind turbines have diversion features built into the turbine body itself, and the turbine's outer shell acts as a heat sink for the excess power. Many charge controllers allow you to use the diverted current for other uses, such as running a water heating coil, a ventilating fan or a space heating system, making the wind generator an even more useful and efficient source of power.
Once a load-diverting charge controller is attached between the wind turbine and the storage batteries, your electrical system can be connected to the batteries, either directly for a matching-voltage DC system, or through an inverter for an AC or mixed AC/DC system.
Wind turbines come in a range of output voltages, to match the overall voltage of your electrical system. While 12 volt is common for small to mid-sized systems, large systems can be designed in 24 or 48 volt configurations.
The primary consideration in a wind generator is the average wind speed at the installation site. A different turbine will give optimum performance at a site with average wind speeds below 15mph than one at a site with speeds in the low 20mph range. Generally, low speed generators will either have longer rotor blades or a larger number of short, wide blades to maximize power drawn from minimal wind. High speed generators may be built of more durable material, and will have narrow, relatively short blades to minimize potential rotor damage in extremely high winds.
Before choosing which type of turbine is best for a particular site, some sort of wind speed measurement should be taken for a few consecutive months (or ideally, a full year). With long term wind measurements an accurate average wind speed can be calculated, as well as determining likely maximum wind speeds. Armed with this information, a turbine can be chosen that will maximize performance at the average wind speed, as well as one that will withstand the likely maximum forces.
Wind generators are not as affected by Alaska's climate as solar panels. With the right site, you can have a steady wind flow all year, unlike our sunlight fluctuations. In general though, most sites will have more wind during the winter months. This is ideal if you have a solar/wind hybrid power system, as the wind turbine will perform best when the solar panels perform least and vice-versa.
One possible problem with wind turbines is the remote possibility of the propeller icing up in winter. Of course if the propeller freezes in place, the turbine won't be of much use. However, if the wind generator is mounted in a clear location (without snow blowing off surrounding surfaces into the turbine) with fairly steady winter winds, the constant motion of the turbine should be sufficient to keep the propeller clear.
However, to make up for the inconveniences, according to the Department of Energy's Energy Efficiency and Renewable Energy network (EREN), "Some wind turbines in Alaska produce more than their maximum rated power output because air becomes denser at lower temperatures. This effect can cause a 20% increase in maximum power output at -35degF."
Like solar power, a wind energy system is an entirely clean source of power. The only potentially hazardous materials involved are the storage batteries. Wind turbines produce no emissions, use no traditional fuel, and can provide reliable year-round power given the right location.
Wind generators require relatively little maintenance, but it is recommended that the generator receives annual visual check-ups to ensure the propeller blades haven't been damaged. If the turbine is located in a good spot it's very unlikely to be damaged by any flying debris, but a chipped or cracked blade can be a hazard should it break completely, and a chipped or damaged blade will also negatively affect the turbine's performance.
Wind turbines are very useful in almost any marine or household electrical system. In marine use, the movement of the boat will raise enough breeze to get the generator turning even when actual winds are fairly low, making them an extremely reliable source of on-board power. For residential systems, wind power can be a wonderful source of power during low-light winter months and even year-round, depending on the site. They can also be configured to power dedicated water pumping systems, which may be of particular interest to individuals currently without running water.
For commercial and industrial use, wind turbines are particularly useful in rugged remote locations such as mountaintop repeater stations or offshore oil platforms. High elevation and offshore or seaside remote sites often have fairly high year-round wind current that will make the most of wind generation systems. Industrial grade wind generators are available to withstand the worst storm winds present at such sites.