More and more people are realizing that renewable energy is the way of the future. But few people clearly understand what its all about and how to make the right choice for their personal situation. If you are considering wind energy as part of your strategy, there are a few important things you need to consider in order to determine if wind energy is right for you.
When wind currents blow past a turbine, the blades capture this “kinetic” energy and begin to turn or rotate. This rotation drives an internal shaft that is connected to a gear box. The gear box increases the speed of rotation about 100 times. This increase in rotation spins a generator that produces electricity.
-Utility scale: These wind turbines generate greater than 100 kilowatts of electricity. The energy is delivered to the power grid and distributed by utility companies and eventually to the consumer.
-Off shore wind energy: These utility scale turbines are erected in various bodies of water, especially the ocean.
-“Small wind”: These are turbines of 100 kilowatts or smaller that deliver direct power to a home or business. This is residential scale wind energy.
From a technical perspective, there is a very specific mathematical formula used to calculate the exact amount of power that can be derived from wind energy. However, this is the stuff for engineers.
On a practical basis, a maximum of about 60% of wind power can be theoretically captured as energy. This is because no energy generation system is 100% efficient. There are losses in drive trains, generators, inverters and power lines. Ultimately, only 30 to 35% of the available wind energy will be converted into usable electricity.
For the sake of comparison, due to system inefficiencies, a 2.0 kilowatt solar array would only produce about 1.0 kilowatt of usable energy.
The simple fact is that wind energy is not for everyone. There are a lot of situations where you simply cannot tap into this resource well enough to make a return on your investment. So, let’s look at what it takes to have a good wind energy system.
Reliable wind resource.
In order to generate a significant amount of electricity using wind, you obviously need to have a lot of wind. Average wind speed needs to be 8 to 14 miles per hour. Wind turbines usually have a minimum start up wind speed as well as a cut off speed. Too high of a wind velocity can actually damage a wind turbine.
For any renewable energy system, the amount of energy production directly affects return on investment, cost savings, etc. This is NOT an area where you want to play a guessing game. Read below for further information on site assessment.
Wide open spaces
In order to harvest wind energy, a tower of sufficient height is imperative. Industry standard is for the lowest blade tip to be at least 30 feet higher than anything within 500 feet away. Most home wind turbine towers are 80 to 100 feet tall. The taller the better with no obstructions.
Most turbine installation instructions will have a minimum tower height on open ground and will also list a minimum height above any obstructions. Nearby obstructions tend to create wind turbulence, which in turn reduces the efficiency of the turbine. Pay attention to these details in order to obtain maximum energy production.
In my experience, it is important to spend some time on your property prior to installing any sort of renewable energy system. Nothing can substitute for several months of observation of weather patterns. Some people recommend living on your property for at least a year. I had my property for a number of years prior to installing a large solar array. By then, I knew exactly where the installation would occur.
However, there are a number of things you can do to access your property in a timely manner and get installation under way. Consider the following:
Onshore versus off shore winds:
This type of wind pattern is easily noted near the ocean or other large bodies of water. Uneven heating and cooling of the land versus the body of water causes onshore winds (blowing inland) in the morning and offshore winds (blowing toward the body of water) in the afternoon.
Wind moving up and down valleys also occurs due to uneven heating and cooling. As the land warms up so does the air. Warm air moves up a valley in the first half of the day. As cooling happens later in the day, air flows back down a valley.
Tall trees and tall buildings close by can deflect the wind and cause a lot of turbulence. This will directly affect the efficiency of your wind turbine and consequently the efficiency your energy production.
As winds travel up and down ridges, wind speed can increase by as much as 50%. Ridge tops can be a great location for a turbine.
If your property is your primary residence, most likely you already have a great idea of the direction of prevailing winds. If it is not your residence then spend some time on your property on a regular basis through out the year. Weather patterns can be very regional depending on your local geography. You may be surprised to realize that you have your own microclimate. Nothing beats good observation.
Also, take note of vegetation patterns. Strong prevailing winds in one direction tends to cause “flagging”, which is similar to a flag on a pole blowing down wind. Persistent strong winds stunt the growth of limbs on the up wind side of the tree which makes the limbs on the downwind side appear to be “flagging”.
Flagging can be used as a means of approximating the average wind speed. The scale is known as the Griggs-Putnam Index of Deformity. According to the index, slight flagging means that most likely the average annual wind speed is seven to nine miles per hour. Slightly more flagging equates to an average annual wind speed of nine to eleven miles per hour. Moderate flagging means 11 to 13 miles per hour. Complete flagging equates to an average annual wind speed of 13 to 16 miles per hour.
For a great pictorial example of this, search for the Griggs Putnam Index of Deformity.
Highest point on the property
Examine the highest point on the property, which can often be the best place for a wind turbine. Take photographs in every direction in order to analyze any potential problem areas.
It is important to look at several different resources in order to properly analyze your wind energy potential. This will give you a more complete picture of your potential energy resource. Before pulling out your wallet, start by looking at data on the internet to first determine if you have the potential for harvesting wind energy.
There are a number of resources that can give you a great idea of the wind in your area. Keep in mind that you cannot depend solely on this information.
National Renewable Energy Laboratory nrel.gov
This is a government sponsored website geared toward assessing numerous aspects of national renewable energy resources. Click on the “Wind” tab. Scroll down to find an area for Annual Average Wind Speed. Heights range from 30 meters to 80 meters. The 30 meters is geared toward residential. From this point, look at state maps and get a good idea of the average wind speed. State maps are at windexchange.energy.gov. You can download a PDF if you wish.
Cost to you: FREE
This site is useful for looking into historical weather data for a particular area.
Cost to you: FREE
-windNavigator @ navigator.awstruewind.com
This is a fantastic website. It is obviously aimed at utility scale wind assessment. The least expensive price I could find was a Day Pass for $150. However, this is a small investment if you are truly interested in accurate data.
Minimum cost: $150
Set up a mini turbine
Purchase a small turbine, similar to what would be used for marine application. Connect the turbine to a watt meter and record your energy production. Due to the size of this turbine, it will not produce a signifiant amount of electricity. However, it will take a direct measurement of what you could potentially produce.
The disadvantage of doing this is that you have to set up a tower at the same height which would be needed for a larger turbine. The tower for the smaller turbine will not be sufficient for the larger turbine needed to produce household electricity. Consequently, I would only recommend this method if you are in the mood to experiment and have the time and finances to do so.
Set up a mini weather station
If you are interested in only wind speed, purchase a pole mounted anemometer. Cost is usually under $100. Another option would be to purchase a complete weather station. These cost from $125 to $1000. However, with the advantages of modern technology, a good instrument can be found for less that $150 in order to produce the needed information.
With some exceptions (perhaps micro-hydro) most renewable energy systems are not generating electricity 24/7. This does not have to be a problem depending on what you decide to use for a backup.
If you are tied to the grid, then the grid serves as your back up power. If you are off grid, a battery bank serves as your back up. For example, with solar energy, obviously the system is not generating electricity at night when there is no sun. Consequently, energy generation is variable. At night, energy is drawn from the battery bank. The same is true with a wind energy system. The battery bank serves as a back up when the wind is not blowing.
The primary factor that makes a difference in noise level is rotational speed. Smaller turbines generally have a greater rotational speed and will thus make more noise. If you want to compare turbines of the same size, look at the rotations per minute (rpm). That being said, poorly designed systems will always make more noise.
City, county, and state governments may all have requirements that need to be taken under consideration. Due diligence, due diligence, due diligence!! Know what you have to deal with before starting down this road. For example, local restrictions may drive the tower height down so low that any wind energy system will be unproductive. That being said, having a wind generator in a densely populated area is not a great idea anyway.
Electrical and building permits
The average person is not familiar with local electrical codes and building permits. It is therefore important to enlist the services of a professional that can help negotiate this process and make certain the system will pass inspection.
People are usually afraid of or object to things they are unfamiliar with. If you have neighbors, be sure to take them into consideration. Talk to them. Make sure they are aware of what you are doing and educate them on the potential benefits. Once they understand, chances are they fears and objections will subside.
This article is intended to be a good introduction to wind energy. There are many benefits to renewable energy systems. If you want to learn more then read this post on Introduction to Renewable Energy Systems
Go off grid and live well,
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