| Can I have my own wind turbine? |
| Yes! Small wind turbines are ideal for householders, farms, communities and small businesses to use for on-site energy generation. Your individual site specifications (such as location, wind speed and local landscape) will eventually determine the best turbine type and size for your needs. |
| How about VAWTS and HAWTS? |
Virtually all wind turbines used today fit within two broad classes: Vertical and Horizontal Axis.
Vertical axis wind turbines (VAWTs) have advantages and disadvantages, but overall they have not been commercially successful like their cousins, the horizontal axis wind turbines (HAWTs). This is largely due to the poor performance and reliability of most VAWTs. However, there are practical applications for VAWTs and new research and technology is improving their performance.
Horizontal Axis Wind Turbines (HAWTs), on the other hand, are very advanced, reliable, and economical. They come in many sizes and shapes, but they are all descendents of the old windmills used to grind grain or pump water. Today these machines are proven: they are used throughout the world producing clean, affordable, and sustainable electricity. Modern horizontal axis wind turbines produce electricity 70-85% of the time (whenever the wind is over 7-8 mph). |
| Why should I choose wind? |
Wind energy systems are one of the most cost-effective home-based renewable energy systems. Depending on your wind resources, a small wind energy system can lower your electricity bill by 50% to 90%, and help you avoid the high costs of having utility power lines extended to remote locations, prevent power interruptions, and is non polluting. |
| How much of the time do wind turbines produce electricity? |
| A modern wind turbine produces electricity 70-85% of the time, but it generates different outputs dependent on wind speed. |
| What happens when the wind stops blowing? |
| First of all, even if the wind stops blowing, thanks to the inertia of the blades, the turbine will still run and hopefully be turning until the next breeze. If the wind stops blowing for a long moment, electricity continues to be provided by other forms of generation in an isolated system (e.g. batteries, diesel generator), and by the grid in a grid-connected system. |
| What are the economic obstacles to greater wind power usage? |
Even though the cost of wind power has decreased dramatically in the past 10 years, the technology requires a higher initial investment than fossil-fueled generators. Roughly 80% of the cost is the machinery, with the balance being for site preparation and installation. If wind generating systems are compared with fossil-fueled systems on a "life-cycle" cost basis (counting fuel and operating expenses for the life of the generator), however, wind costs are much more competitive with other generating technologies because there is no fuel to purchase and minimal operating expenses. |
| Are wind turbines hazardous to birds and bats? |
Bird and bat deaths are one of the most controversial biological issues related to wind turbines. The deaths of birds and bats at wind farm sites have raised concerns by fish and wildlife agencies and conservation groups. On the other hand, several large wind facilities have operated for years with only minor impacts on these animals.
To try to address this issue, the wind industry and government agencies have sponsored research into collisions, relevant bird and bat behavior, mitigation measures, and appropriate study design protocols. In addition, project developers are required to collect data through monitoring efforts at existing and proposed wind energy sites. Careful site selection is needed to minimize fatalities and in some cases additional research may be needed to address bird and bat impact issues.
While structures such as smokestacks, lighthouses, tall buildings, and radio and television towers have also been associated with bird and bat kills, bird and bat mortality is a serious concern for the wind industry. |
| Do wind turbines pose a safety hazard? |
Unlike most other generation technologies, wind turbines do not use combustion to generate electricity, and hence don't produce air emissions. The only potentially toxic or hazardous materials are relatively small amounts of lubricating oils and hydraulic and insulating fluids. Therefore, contamination of surface or ground water or soils is highly unlikely. The primary health and safety considerations are related to blade movement and the presence of industrial equipment in areas potentially accessible to the public. Like all electrical generating facilities, wind generators produce electric and magnetic fields. |
| Are there environmental problems facing wind power? |
Although wind power plants have relatively little impact on the environment compared to fossil fuel power plants, there is some concern over the wildlife habitat impacts, noise produced by the rotor blades, aesthetic (visual) impacts, and bird and bat mortality. Most of these problems have been resolved or greatly reduced through technological development. |
| What are the advantages of wind-generated electricity? |
Numerous public opinion surveys have consistently shown that the public prefers wind and other renewable energy forms over conventional sources of generation. Wind energy is a free, renewable resource, so no matter how much is used today, there will still be the same supply in the future. Wind energy is also a source of clean, non-polluting, electricity. Unlike conventional power plants, wind plants emit no air pollutants or greenhouse gases. |
| Does the turbine location have plenty of wind? |
This point seems like a reasonable question. Just how much wind will your wind turbine be exposed to and how big are the seasonal swings? For a wind site to be considered a "good" site, it must get enough wind but not too much at one time. Indeed too much wind at one time can be considered a "bad" thing. You may think one day at 0 mph and another day at 40 mph would be an average of 20 mph but there is more to it than that. A 20 mph wind is a nice breeze if it is somewhat steady but extreme high and low speeds will present problems.
So what amount of wind is considered adequate? You can find recommendations of what your average wind speed should be and it is typically in the 12 mph range. This is good information but in our opinion you will want to know more about how that average correlates into useable power. If the application is a grid tie then average wind speed may be more easily applied but for the off grid system there is much more to consider. |
| How does the wind turbine perform compare to PV (Photovoltaics)? |
| It’s really hard to compare renewable energy between themselves as they are very different and too many constraints. In order to compare them, calculations are made to give a price per kWh. First the wind speed is a major factor in wind power generation, it is safe to say that above 4m/s, a wind energy system will easily outperform PV. The second major actor is the installation size. As we have seen above, contrarily to PV system, wind power increase with its blade size, therefore the bigger your wind turbine, the cheaper your price. |
| Do wind turbines make noise or interfere with TV reception? |
Most turbine noise is masked by the sound of the wind itself, and the turbines run only when the wind blows. Noise from wind turbines has diminished as the technology has improved. Early-model turbines are generally noisier than most new and larger models. As wind turbines have become more efficient, more of the wind is converted into rotational torque and less into acoustic noise. Under most conditions, modern turbines are quiet. Small wind turbines do make some noise, but not enough to be found objectionable by most people. A typical residential wind system makes less noise than the average washing machine. Wind turbines do not interfere with TV reception. |
| Can I connect my turbine to the grid? |
Yes! Small wind turbines can be connected to the local electricity network. When a wind turbine connection to the mains supply is made, it has to be approved by your local electricity distribution utility. This company will require the connection to be of a satisfactory technical standard. Therefore the cost of incorporating power import and export metering and approved electrical protection equipment will add to the total cost. The company may also limit the electrical capacity of the wind turbine that may be connected to a particular distribution line, depending on the loading of the electrical distribution system in the vicinity.
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| Can I use my turbine for heating? |
Yes but small wind turbines can be used for direct heating, e.g water heating as well as for battery charging and they are also ideal in remote off-grid locations. However, the energy required to heat a building is usually significantly more than the energy used in electricity, so a much larger turbine would be needed for building heat. Direct heating is only done with excess energy, for example when the batteries are full. Small wind turbines are very effective for powering a heat pump, which can heat your house.
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| What is the difference between a grid-tie and an off-grid wind energy system? |
Here's a basic overview of the three basic types of residential wind energy systems:
A. Grid-Connect (Grid-Tie) Systems without Batteries: Grid-connect systems interface directly with
the electric utility grid via an inverter (provided with our grid-connect wind generators). A Voltage Clamp ( grid-connect controller) rectifies the wind generator's "wild" (variable voltage & frequency) alternating current (AC) to direct current (DC) and limits the maximum output voltage in order to maintain the health of the inverter. The inverter changes the DC outputted from the Voltage Clamp into AC at the required frequency (60 Hz or 50 Hz, depending upon country) and synchronizes with the utility power grid, prior to sending energy produced by the renewable energy system to the household appliances and/or to the grid.
Advantages: Grid-connect systems avoid the inherent inefficiency and vigilant maintenance requirements of batteries. Sizing a wind energy system for grid-connection is also simpler than with its battery-charging counterpart, because the utility grid can make up for mismatches between the electrical loads and the wind generator's production capability.
Additionally in many states, there are production incentives for renewable energy sent to the utility grid (while relatively few states provide renewable energy incentives for off-grid production).
Disadvantages: If the utility grid shuts down, so do grid-connected renewable energy systems without battery back-up. In situations where continuous power is critical or where power outages are frequent, battery back-up equipment may be advisable.
B. Battery-Charging Off-Grid Systems: Battery-charging systems feed through a charge controller and into a battery bank. This type of system is primarily used in remote locations where grid power is not available. When storing renewable energy exclusively in batteries, the renewable energy equipment and battery bank must be sized appropriately to maintain sufficient energy to match consumption and maintain battery health.
Advantages: Battery-charging systems provide their owners with energy independence. Thus, off-grid systems are unaffected by electric utility grid outages.
Disadvantages: When insufficient energy is captured by a battery-charging system, the homeowners must curb their usage to match (since there is no infinite power source, such as the utility grid, to draw upon). Conversely, when the battery bank is full and renewable energy is being produced at a rate faster than loads are being fed, the excess energy is usually "wasted" by heat dissipation (this excess energy can optionally be put to use with water-heating elements in a hot water tank). Batteries require vigilant care and maintenance to keep water and charge levels adequate. Renewable energy batteries are expensive, and failure to properly maintain them can be a very costly mistake.
C. Grid-Connect Systems with Battery Back-up: Grid-connect systems with battery back-up can be configured in several ways - with batteries filled from the utility grid or from the renewable energy system. This system functions similarly to the system described in letter A (Grid-Connect Systems without Batteries) above but continues to function via a back-up battery bank when the local utility grid experiences a power outage.
Advantages: This system combines the best traits of the other two system types. The utility grid can be utilized to fill in energy consumption gaps or over-production surpluses, and they continue to operate (on batteries) if the utility power grid experiences an outage.
Disadvantages: Since this type of system uses batteries, careful maintenance and attention to battery water and charge levels are required in order to maintain healthy batteries. Also, this is generally the most expensive of the three system types, because a more complex configuration comprised of both grid-connect and off-grid equipment is required. |
| How tall should my wind tower be? |
Selecting an appropriate tower size can make a significant difference in energy production. In general, towers should be installed at such a height that the turbine's blade tips (in their lowest position) are 30 feet above all objects (buildings, trees, silos, hills, etc.) within a 500 foot radius.
This will minimize turbulence encountered by the turbine, aiding the wind generator to run more smoothly, minimizing the stress on its components, and increasing the generator's life. Another very important consideration regarding tower height: The higher the tower, the faster the wind speed!
A taller tower is the best way to increase your wind generator's performance at a given site. |
| How much space do I need for a turbine? |
| Ideally, stand-alone turbines should be sited as far away as possible from buildings or trees, which may block the wind and cause turbulence. As a guide, the wind turbine should be about twice the height of obstructions in the immediate front of it (for at least the prevailing wind direction). In general, the turbine should be above the height of nearby obstructions that are within a distance of 10 to 20 meters of the tower heights. Rooftop-mounting turbine is not something we generally recommend. It is fairly difficult finding a place on a roof that is strong enough to withstand the forces and has a good wind. Local turbulent airflow around the building, which causes reduction in generated output and could damage the turbine, must be considered as well. In general, the less turbulent and varying the wind, the better the wind power generation. |
| Are capacity factor and efficiency the same? |
No. Efficiency is a measure of how much of the kinetic energy in the wind is converted to electrical energy. It is unavoidable that some energy is lost in the conversion process. Even when a wind turbine is generating power at its maximum capacity, the electrical energy produced is only a fraction of the energy in the wind. (At best, it may be near 60%, which is actually quite efficient.) Efficiency is a matter of engineering and the limits of physics and usually irrelevant to normal discussion.
Capacity factor is a measure of a wind turbine's actual output, which varies with the wind speed, over a period of time.
It must be remembered, though, that wind power is intermittent and variable, so a wind turbine produces power at or above its annual average only a third of the time. That is, most of the time, it is not providing its average power to its average number of homes. It must also be remembered that residential use accounts for only a third of our total electricity use. |
| How does Auto Furl system work in high winds? |
During periods of high wind speeds the AutoFurl system will automatically protect the wind turbine. When furled, the power output of the turbine will be significantly reduced. In winds between 13m/s and 18m/s it is normal for the turbine to repeatedly furl, unfurl and then furl again. In winds above 18m/s the turbine should remain continuously furled.
AutoFurl is a simple and elegant method of providing high wind speed protection. The AutoFurl system is based on aerodynamic forces on the rotor, gravity, and the carefully engineered geometry of the wind turbine. As shown in Figure, the aerodynamic forces acting on the blades cause a thrust force pushing back on the rotor.
This force increases with increasing wind speeds. The thrust force acts through the centreline of the rotor, which is offset from the centreline of the tower pivot axis(yaw axis). Therefore, the thrust force on the rotor is always trying to push the rotor over to the side, away from the wind.
But the rotor is kept facing into the wind at speeds up to 12.5m /s by the wind turbine tail assembly. The tail, in turn, is kept straight by its own weight because its pivot at the back of the nacelle is inclined. So the weight of the tail holds it against a rubber bumper and the tail holds the rotor into the wind.
The geometries in the systems are carefully balanced so that at 12.5m /s the rotor force acting on the yaw-offset is large enough to overcome the preset force holding the tail straight. At this point the rotor will start turning away from the wind or furling. The tail stays aligned with the wind direction. The speed of furling depends on the severity of the wind gusts and whether the wind turbine stays furled depends on the wind speed.
As the wind turbine furls the geometry of the tail pivot caused the tail to lift slightly. When the high winds subside the weight of the tail assembly returns the whole turbine to the straight position. The AutoFurl system works whether the turbine is loaded or unloaded.
The AutoFurl system is completely passive, so it is very reliable and since there are no wear points, like in a mechanical brake system, it is very robust.
There is one situation in the field, however, that we have found can disrupt the operation of AutoFurl. If the wind turbine is installed on a sharp hill or next to a cliff so that the wind can come up through the rotor on an incline(e.g., from below; as opposed to horizontally) we know that this will affect furling and can produce higher peak outputs. We strongly recommend avoiding this situation. |
| How to choose the battery capacity? |
| For example, in a street lamp system with 24VDC battery, when a lamp is 24W and work 8hours a day, than it is (24W / 24V) X 8 hours =8 AH per day. We need the battery can keep system working without solar and wind in succession 3 days. So 8AH X 3 = 24 AH. The depth you discharge a battery to before recharging it is the depth of cycle. In a deep cycle battery, the depth of cycle could be 30%. So we can choose a 80 or 100AH battery bank, because 80AH X 30% =24AH. |
| What type of battery should I use (automotive or deep cycle)? |
We recommend a kind of deep cycle, VRLA (Valve-Regulated Lead Acid) batteries which will give you several hundred complete charge/discharge cycles. If you use the normal vehicle starting batteries they will wear out after about a dozen charge/discharge cycles. If you do not have a deep cycle battery, we recommend that you run the engine of your vehicle when operating the power inverter.
When operating the inverter with a deep cycle battery, start the engine every 30 to 60 minutes and let it run for 10 minutes to recharge the battery. When the inverter will be operating appliances with high continuous load ratings for extended periods, it is not advisable to power the inverter with the same battery used to power your car or truck. If the car or truck battery is utilized for an extended period, it is possible that the battery voltage may be drained to the point where the battery has insufficient reserve power to start the vehicle. In these cases, it's a good idea to have an extra deep cycle battery for the inverter (installed close to the inverter), cabled to the starting battery. It is recommended to install a battery isolator between the batteries. |
| How do I connect two or more batteries? |
It may be advisable to operate the inverter from a bank of 12 Volt batteries of the same type in a "parallel" configuration. Two such batteries will generate twice the amp/hours of a single battery; three batteries will generate three times the amp/hours, and so on. This will lengthen the time before your batteries will need to be recharged, giving you a longer time that you can run your appliances.
You can also connect 6 Volt batteries together in "series" configuration to double the voltage to 12 volts. Note that 6 Volt batteries must be connected in pairs.
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12 Volt Batteries connected in Parallel to double the current (amp/hours)
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6 Volt Batteries connected in Series to double the voltage to 12 Volts
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| What does an inverter do, and what can I use one for? |
An inverter changes DC power from a battery into conventional AC power that you can use to operate all kinds of devices ... electric lights, kitchen appliances, microwaves, power tools, TVs, radios, computers, to name just a few. You just connect the inverter to a battery, and plug your AC devices into the inverter ... and you've got portable power ... whenever and wherever you need it. The inverter draws its power from a 12 Volt battery (preferably deep-cycle), or several batteries wired in parallel. The battery will need to be recharged as the power is drawn out of it by the inverter. The battery can be recharged by running the automobile motor, or a gas generator, solar panels, or wind. Or you can use a battery charger plugged into an AC outlet to recharge the battery. |
| What size inverter should I buy? |
Short Answer: The size you choose depends on the watts (or amps) of what you want to run (find the power consumption by referring to the specification plate on the appliance or tool). We recommend you buy a larger model than you think you'll need (at least 10% to 20% more than your largest load).
Example: You want to power a computer with a 17" monitor, some lights, and a radio.
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Computer: |
300 Watts |
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2- 60 Watt lights: |
120 Watts |
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Radio: |
10 Watts |
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Total Needed: |
430 Watts |
For this application, you would minimally need a 500 W inverter, and should give some thought to a larger one, as there will likely be a time when you wish you'd bought a bigger model ... in this example, you might decide you'd like to run a fan while you compute, or let the kids watch TV.
Longer Answer: Determine Continuous Load and Starting (Peak) Load: You need to determine how much power your tool or appliance (or combination of them that you would use at the same time) requires to start up (starting load), and also the continued running requirements (continuous load). What is meant by the terms "continuous-2000 watts" and "peak surge-4000 watts" is that some appliances or tools, such as ones with a motor, require an initial surge of power to start up ("starting load" or "peak load"). Once started, the tool or appliance requires less power to continue to operate ("continuous load") |
| Do I need Modified Sine Wave, or Pure Sine Wave in wind energy system? |
Advantages of Pure Sine Wave inverters over modified sine wave inverters:
a) Output voltage wave form is pure sine wave with very low harmonic distortion and clean power like utility-supplied electricity.
b) Inductive loads like microwave ovens and motors run faster, quieter and cooler.
c) Reduces audible and electrical noise in fans, fluorescent lights, audio amplifiers, TV, Game consoles, Fax, and answering machines.
d) Prevents crashes in computers, weird print out, and glitches and noise in monitors.
e) Reliably powers the following devices that will normally not work with modified sine wave inverters:
Laser printers, photocopiers, magneto-optical hard drives
Certain laptop computers (you should check with your manufacturer)
Some fluorescent lights with electronic ballasts
Power tools employing "solid state" power or variable speed control
Some battery chargers for cordless tools
Some new furnaces and pellet stoves with microprocessor control
Digital clocks with radios
Sewing machines with speed/microprocessor control
X-10 home automation system
Medical equipment such as oxygen concentrators In conclusion, a pure sine wave inverter is preferable in a wind energy system. |
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