Jumping into the bandwagon of renewable energy, wind power actually has long been powering homes and farms in the early days. In fact, it was already utilized by humans dating as far back as the 9th century in areas of Persia, or better known now as Iran. It was traditionally used to facilitate milling of agricultural grains into flour, or pumping water for livestock Nevertheless, it was only in July of 1887 in Scotland when the windmills were first wielded to produce electric power. Years thereafter, various developments have undertaken which successfully lead us today to a cleaner and sustainable means of providing electricity for domestic and industrial uses.
In 2017, wind power generated the second most renewable electricity, contributing as much as 1,134 TWh or 18% globally. This green alternative energy is quickly becoming a viable source of electricity not just for commercial but most especially for residential consumers too. In this article, we will focus on the application of wind energy in a more basic and practical setting, our homes.
What is a Small Wind Electric System?
A small wind electric system is primarily comprised of small wind turbines that are intended to use for the microgeneration of electricity, rather than the typical large commercial turbines used in wind farms. Nonetheless, the basic principles governing both the small wind and large-scale systems are practically the same.
How does a Small Wind Electric System work?
The wind is created by the uneven heating of the sun on the Earth’s surface and the atmosphere. The wind turbines then function by converting the kinetic energy of the wind into clean electricity. Basically, as the propeller-like blades of the turbines get spun by the wind, the rotor shaft captures the kinetic energy from the wind and converts it into mechanical power that runs the generator thus producing electricity in the end. Most modern turbines are equipped with an automatic overspeed-governing system that efficiently regulates the pace of the rotor and prevents it from getting out of control as caused by very high winds.
What are the basic designs of Small Wind Turbines?
Horizontal-Axis Wind Turbine
The Horizontal-Axis Wind Turbine or HAWT, in short, consists of a rotor shaft and generator at the apex of the tower. With this type, it is a prerequisite that it should be pointed at the direction of the wind for it to capture the flow face-on and function efficiently. The HAWT for small turbines are connected to a simple wind vane, unlike in large turbines that are attached to a wind sensor. As for the blades, it is usually positioned with a certain distance in front of the tower. There are also instances where manufacturers design it to slightly tilt forward into the wind. Furthermore, the blades are also intently built to be rigid so as to prevent it from pressing towards the tower in cases of very high winds.
Vertical-Axis Wind Turbine
The Vertical-Axis Wind Turbine or VAWT, in short, is distinctly different from HAWT in a way that its main rotor shaft is positioned vertically. Thus, it renders it unnecessary for the turbine to be pointed toward the wind in order for it to become effective. This advantage is particularly beneficial for locations where the direction of the wind is eminently uneven. However, the VAWT also has its own set of pitfalls. A few of its major limitations are its low revolving speed and significantly higher torque.
Aside from the obvious differences between horizontal-axis and vertical-axis wind turbines, the table below further shows the comparison of both in relation to specific parameters:
|Power generation efficiency||50% – 60%||More than 70%|
|Wind steering mechanism||Yes||No|
|Gear box mechanism||Yes||No|
|Blade rotation space||Large||Small|
|Noise||5 – 60 decibel||0 -10 decibel|
|Starting wind speed||2.5 – 5 m/s||1.5 – 3 m/s|
|Operation & maintenance||Complicated||Convenient|
What are the components of a Small Wind Electric System?
The majority of the small wind turbines manufactured in the market today are horizontal-axis turbines. This type usually comes with two to three blades that are oftentimes made out of a composite material such as fiberglass. The frame of the turbine itself is where the rotor, generator, and tail are attached to. In addition, the diameter of the rotor fundamentally determines the amount of energy the turbine produces by virtue of defining how much wind has been intercepted by the blades. Meanwhile, the tail is responsible for making sure that the turbine is facing accordingly towards the direction of the wind.
To serve as the base, the wind turbine is mounted onto a tower. By principle, the higher the tower, the more power will be produced since wind speed relatively increases with height. There are two main types of towers for wind turbines. First, is the Stand-Alone also referred to as the “Free-Standing” tower, and the second type is Guyed. Most wind power systems in homes today are anchored on guyed towers. Primarily because it is cheaper and also easier to install than the stand-alone type. Notwithstanding, due to the required guy radius of at least one-half or three-quarters of the height of the tower, it is imperative that a significant amount of land area must be allocated for this. On the other hand, a tilt-down version of the guyed tower is also available. Though it is typically more expensive, the tilted position makes it more convenient for users to perform routine maintenance. Moreover, it is also possible to lower this tilt-down guyed tower to the ground, especially at times when an extreme weather disturbance, such as a hurricane or tornado, is anticipated to strike the location.
|TOWER TYPE COMPARISON TABLE|
|Tower Type||Stand-Alone||Guyed||Tilt-Down Guyed|
|Installation||Crane||Installed on the ground then lifted with a crane||Installed on the ground then lifted with a crane|
|Base||7-10% of tower height||Guy radius 50-80% of tower height||Guy radius 25-60% of tower height|
Balance of System (BOS) Components
The Balance of System or BOS are components other than the wind turbines. This includes wiring, switches, inverter, batteries, and chargers. In a small wind turbine system, the BOS parts depend on whether if its a stand-alone, grid-connected, or hybrid type. Nevertheless, most packages offered by the manufacturers for residential small wind turbine installations typically include the following components:
- Storage battery
- Disconnect switch
- Grounding system
- Tower foundation
How to plan a Small Wind Electric System?
If you are considering to invest in a small wind electric system, thorough planning is absolutely crucial in determining the appropriateness and effectiveness of the system to your specific energy requirements. Aspects such as the sufficiency and consistency of wind supply, the suitability of the site for the system, legal zoning parameters, and the overall financial implications must be factored in accordingly in the planning phase.
Wind Resource Estimation
The very first thing to look into is the availability of wind resources. Given that we are mainly looking forward to generating energy through wind power, it is imperative to take into account the estimation of how much and how consistent is the wind resource within the chosen location. The formation of the local terrains also greatly affects the flow of wind in the surroundings. Here are a few ways to help you estimate the wind resource:
- Consult Wind Resource Maps – This is the most basic step to check the estimation of wind resource in your preferred site. The maps can be accessed through the U.S. Department of Energy’s WINDExchange resource portal.
- Check the Airport Wind Speed Data – Another way to gather information with regards to the wind resource is through the wind speed data report from the nearby airport facility. The airport wind data are typically measured at a height of about 20 to 33 feet or 6 to 10 meters above the ground level. Nevertheless, do note as well that the terrain and other factors surrounding the airport may vary from your particular site. Thus, the data may not be as reliable but rather provide rough estimates only.
- Observe Vegetation Flagging – Flagging basically refers to the deformation or weakening caused by strong winds against the trees and other forms of vegetation. By observing which, you will somehow gain an insight into the possible wind speed capacity of the area.
- Measurement System Usage – Using a wind measurement system will provide you with direct and accurate information on the wind resource available in your area. Monitoring may incur costs usually ranging from $600 up to $1,200. Ideally, the readings must be taken at an elevation where the turbines will most likely be installed in order to gather more precise and useful information.
- Gather Information from Local Small Wind System – If the locality has an existing small wind system, you may opt to request for the available information pertaining to the annual output and wind speed data.
Zoning & Permit Requirements
Prior to deciding to install the small wind system, it is also important to research the local requirements imposed by the city, municipality or state. The information concerning the zoning restrictions can be obtained from the local building inspector, the board of supervisors, or the planning board in the area. These point persons will help determine which permits and requirements need compliance.
Furthermore, it is also worth looking into the prevailing community issues if there are any. Apart from the legal obligations, there are also instances where the community themselves poses some level of objection in relation to having a wind system installed in the vicinity. Commonly, homeowners are particularly worried about the following issues:
- Height – Most residentially-zoned areas restrict the height requirement of structures usually at a maximum limit of 35 feet. Although the figure may differ depending on the local ordinances.
- Noise – The typical sound level of most modern residential wind turbines is slightly above the ambient wind noise depending on its type. That being said, the small wind turbines do not necessarily produce disturbing noise. Nevertheless, you still have to ensure that the neighboring homeowners and facilities are not bothered in any way to prevent future disputes.
Economics of Small Wind System
Installing a small wind system is certainly a big investment. Thus, it is imperative to make a careful analysis of the financial impact of the system. Knowing this will help you determine whether the wind energy system will practically work in favor of your benefits and gains in the longer run. Below are some of the things you need to assiduously evaluate:
- Wind characteristics
- Total wind output
- Electric bill comparison
- Cash flow
- Return of investment
How to install a Small Wind Electric System?
Now that comprehensive planning has already been undertaken, let us now move into the circumstances involved in the installation of a small wind electric system. This usually involves finding the right location, determining the correct sizing of turbines and tower, estimation of annual energy output, and deciding whether to connect to the electric grid or to remain as an off-grid or stand-alone system.
Finding Location for Small Wind Electric System
In order to find the right location to install the small wind electric system, the following circumstances must be taken into account accordingly:
- Wind Resource – The complexity of the terrain along with structural interference, such as trees, houses, and buildings, impacts the efficiency of the wind flow. Generally, the higher the elevation and less obstructed, the more wind can be harnessed as compared to those on a gully or sheltered side of the hill. Hence, it is possible to have varied wind resources in the same property. Ideally, the turbines must be sited at least 30 feet above any structure within a minimum of a 300-feet parameter area. Moreover, it is equally necessary to determine the direction of the wind flow to get the right positioning of the system and optimize the power.
- System Component Considerations – Depending on the type of wind system used, ensure that there will be sufficient land area allocated for the guy wires if using guyed towers. The length of the wires plays a significant role in the occurrence of energy lost. The longer the wiring, the more electricity will be wasted due to resistance. In addition, a large area is also needed to give space in the lowering and raising of the tilt-down guyed tower during routine maintenance or weather emergencies.
Sizing the Small Wind Turbine
The size of small wind turbines intended for domestic applications basically depend on the energy requirements of the user. Most often, it ranges from 400 watts up to as much as 20 kilowatts. To help you decide on what appropriate size to choose, you must first set how much the energy budget will be. Practically, the reduction in electricity usage is more cost-effective than having the need to generate more energy to accommodate demand. In addition, it also minimizes the initial expense subsequently because the lesser the energy need, the smaller the size of the wind turbine will be required too.
Furthermore, the height of the wind turbine’s tower is another important factor to deal with as it also controls how much wind power the system will be able to generate. Technically, the higher the tower, the more power is produced due to the increase in wind speed. Nonetheless, it is still highly advisable to consult professional assistance from experienced installers to get a more accurate sizing.
Annual Energy Output Estimation
Among all methods, the annual energy output is the best determinant of the size of the small wind system. The estimation of which will provide you an insight regarding the sufficiency of the system based on your prevailing energy demands. Generally, wind turbine manufacturers can assist you to figure out the estimated amount of expected energy production. The following elements are often used by the manufacturer as the basis to calculate the estimates:
- Wind turbine power curve
- Average annual wind speed
- Height of the tower
- Frequency distribution of the wind
Grid-Connected Small Wind Electric System
Upon installation of the small wind system, the users have the option of whether to tap into an electric grid or not. In the case of a grid-connected system, the utility provider will only supply electricity during instances when the turbine is not capable to deliver. On the other hand, if in case the energy production is greater than the actual consumption, then the excess power is sent off to the grid in exchange for incentives. Overall, the grid-connected system only becomes practical if the conditions stated below are met:
- The average annual wind speed of the area is at least 10 miles per hour or 4.5 meters per second.
- The utility-supplied electricity is expensive or about 10 to 16 cents per kilowatt-hour.
- The grid-connection requirements of the utility company are reasonable and not overly expensive.
Stand-Alone Small Wind Energy System
As opposed to the grid-connected wind energy system, the stand-alone type are independent of the electricity supply of local utilities. And because of that, it is often used for off-grid applications. However, to help augment the power generation, the stand-alone system is also used in combination with other renewable components such as a small solar electric system, for example. Thus, creating a reliable hybrid power system that can adequately deliver the electrical needs of a regular household, farm, or even a small community that are beyond the reach of the utility providers. Notwithstanding, the stand-alone system only becomes practical if the conditions stated below are met:
- The average wind speed of the area is at least 9 miles per hour or 4.0 meters per second.
- Grid-connection is not available, or if there is any, the extension tends to be extremely expensive.
- Your goal is to gain energy independence.
- Your goal is to generate cleaner and sustainable energy.
How to maintain the Small Wind Electric System?
Just like any electric system, the small wind energy system also requires periodic maintenance to keep it running in tip-top shape thus ensuring you get the most benefit out of it. Nevertheless, the system is quite a huge structure with a fairly complex electronic set-up. That being said, if you do not have access to lifting equipment, such as a crane, and if neither are you a certified electrician, then it is highly advisable to seek professional help from experienced installers. For convenience and safety reasons, it is wiser to leave the job to the highly trained people. A small wind electric system is a big investment hence it deserves to be well-taken care off to optimize the gains and extend its longevity.
Typically, the tower and turbine manufacturers provide service and maintenance plans to their customers. So it is best to contact them first for assistance especially if it is still under warranty period. Nonetheless, there are also independent contractors available in the market. You can try to contact the local utility or state energy office to ask for a list of recommendations of credible installers within your area. With proper maintenance routine, a small wind energy system can be expected to last for at least 20 years or even longer. The annual maintenance encompasses services such as check-ups, tightening, and conditioning, but may also require replacement or repair of parts if the need arises. The process usually includes the following:
- Change oil
- Checking and/or replacement of brake pads
- Checking and tightening of bolts
- Checking and tightening of electrical connections
- Checking of machines and other parts for corrosion
- Checking of guy wires for appropriate tension
- Checking and/or replacement of worn leading edge tape of the turbine blades
- After 10 years, checking and/or replacement of turbine blades and bearings if necessary
As we strive to live a cleaner and greener lifestyle, any simple yet valuable action will bring us a step closer to a better and healthier world. Utilizing the power of the wind is one effective way to greatly reduce our carbon footprint. Hence, this once ancient energy system has now effortlessly become popular in the modern age given the technological advancements. The various innovations presented in the market today paved the way for consumers, especially in the residential areas to have their own small wind electric system installed right off their land. This enables the homeowners to be not just energy-efficient and sustainable, but at the same time attain the opportunity to earn extra credit or profit by contributing its generated power to the national grid. Therefore, it is clearly a win-win situation for the user and the environment if one consciously chooses to install a small wind electric system.