The ’70s energy crisis
Photo 1. Example of small windmill
A little before the ’70s energy crisis, Peter, Paul and Mary suggested in their famous song, “The answer, my friend, is blowing in the wind.” Today we realize that wind is a valuable resource we cannot ignore, but wind energy is just one piece in the pie. To fix this energy crisis, we are going to need a lot of conservation plus every alternative energy source we can find.
During the ’70s energy crisis, manufacturers of alternative energy sources starting popping up as the cost of fuel rose. Environmental concerns also started to surface. Concerned about the environment, some people, like my brother-in-law, his wife and three daughters, elected to live off the grid. Electric service from a utility was available but they decided to generate their own. For over 20 years, they have generated all their electric power from solar panels, a windmill and a small hydroelectric generator. There are two reasons why their system has been so successful: their electric energy needs were low and they live on the side of a mountain in Vermont where wind and water pressure are in great abundance. The only disadvantages are the cost of the energy they produce, over five times the utility rate, and the fact that a hair dryer plugged into their system could cause a melt down.
In 1971, I had just graduated from college and purchased my first home. I also had been readingMother Earth News, so I did my part by designing and constructing a 16-foot diameter windmill in my backyard for generating electricity to reduce my heating costs.
Photo 2. My 600-watt windmill in 1975
Unfortunately, I did not have the advantage my brother-in-law has. In Delaware, the wind “sucks.” Yes, it did pay for itself in a few years only because I used salvaged parts and my labor was free. The installation also cost me a few friends (my neighbors). Fortunately for them, they only had to look at it for a few years because my wife divorced me. She got the house. I got the windmill.
These examples of utilizing wind power back in the seventies bring out three very important aspects of wind power, location (How windy is it where you live?), environmental impact (How will your neighbors and the building inspector feel about your idea?), and how much will it cost (Will you ever get you money back?).
Windmill information on the Internet
There is a tremendous amount of information on windmills on the Internet. While writing this article, I have spent over forty hours searching the Internet researching wind power. Please note that neither the IAEI nor I are endorsing any of the products mentioned in this article. The manufacturers and organizations presented here are only examples of the many that are available.
Beware!
With this energy crisis, many good companies and organizations have developed reliable products and published truthful information on energy products and solutions. However, there are companies who manufacture and attempt to sell products that don’t do what they are advertised to do. To protect yourself, I recommend you use the following steps when considering a particular product: Find out how long the company has been in business. How many have they sold? Is there a local distributor in your area? How long has the distributor been in business and how long has it been selling these units? Contact your local Better Business Bureau to see if there are any complaints against the manufacturer or distributor. How long is the warranty? Get a list from the manufacturer of people/companies in your area who have purchased the unit you are considering. Go talk to them. Check out their installation. Find out how well their unit is performing. Did they have any problems? How were the problems resolved? If you are going to hire someone to do part or all of the installation, put it in writing (contract).
Utility-size wind powered electric generation
Photo 3. Example of utility-size wind powered electric generators at Maple Ridge Wind Farm
You may have noticed that many of the electric utilities in the U. S. are building monster windmills in high wind speed areas. Florida Power and Light is the largest U. S. generator of wind-powered electricity. They own 47 wind farms in 15 states. There are usually hundreds of windmills at each farm. As of January 2007, Florida Power and Light’s wind power capacity exceeded 4,000 megawatts. For more information, seewww.fplenergy.com.
Photo 3 is one I took of some of the windmills at Maple Ridge Wind Farm in New York about 75 miles northeast of Syracuse. Horizon Wind Energy owns this farm where there are 195 units that can generate a total of 322 megawatts of power. The blades are 130 feet long, the towers are 260 feet tall, and each unit can produce 1.65 megawatts of power. The blades rotate at 14 RPM. For more information, see www.horizonwind.com. There is also a very nice article on the upstate New York windmills in the September/October 2006 issue of Adirondack Life magazine.
In one farm I visited in Wisconsin, each windmill could generate 2.2 megawatts of power. The generator produced three-phase, 1000-volt ac at variable frequency because the turbine speed varied with the wind speed. At the base of each tower was a rectifier that converted the variable frequency ac to dc, an inverter that converted the dc to 60 Hz., 1000-volt, three-phase ac, and a three-phase transformer to change the voltage to 34,500-volt, three-phase. 35-kV class cables are used to transmit the power to a large central substation where several very large transformers boost the voltage to transmission levels to tie into the grid.
Location—How windy is it where you live?
Photo 4. Reflective aluminum blades of my windmill
The most important thing to consider when looking into purchasing a wind powered electric generator is the wind conditions in your area. Too often people assume that they have strong winds in their area because they frequently feel and enjoy the breeze, particularly people who live on or near the shore of a large body of water. Just because you often have a nice breeze doesn’t mean the wind is strong enough to make wind powered generation economical. I have heard a lot of people say, “It must be economical because it is free.” Yes, the wind is free but windmills are very expensive.
To check out the wind resource in your area, go to the Department of Energy, Energy Information Administration web sitewww.eia.doe.gov, click on Renewable & Alternative Fuels, on the left click on Wind, down at the bottom click on Wind Resource Potential (Map). This national map gives you a general indication of relative wind speed.
To see further detailed information on your particular state, go to the Department of Energy, Energy Efficiency and Renewable Energy web sitewww.eere.energy.gov, click on Wind & Hydropower Technologies, click on Wind Energy, click on Resource Potential under Wind Energy Basics, scroll down to the bottom and click on Wind Powering America State Wind Map. Just past the first national map, you will see on the left: Quick Links to States. Click on your state (abbreviation). Note the Wind Powering America Activities for your state. Some states have anemometer loan programs so you can do your own site survey. If your state has a Validated Wind Map, click on that phrase and you will see the map. Some states have a Small Wind Consumer Guide.
Site Survey
If your area looks promising, the next step is to get a site survey. The wind resource in your area may be good but your site may not be perfect. For example, if you have a lot of trees, the tree top height is ground level for a windmill. For the windmill to be effective, it has to be mounted well above the tree top level. Hilltops are usually great locations. Valleys are usually bad locations. The only way to be sure is to install a recording anemometer at the proposed location and height. There are companies who do this as a service. The local distributor of the unit you are considering can usually help or refer you to a survey company. They may have a record of locations where surveys have already been performed. There is no sense spending money for a survey if a neighbor down the street with a similar site has already done one.
Southwest Windpower has a very nice guide to Siting Wind Generators. To get to it, go towww.windenergy.com, click on Products on the right, click on Towers, just below Tower Kits and Monopole Towers click on Skystream 3.7 Monopole Towers, scroll up to just below the Increase in Wind Power graph and click on Guide: Siting Wind Generators.
Towers
Any time you are looking at wind data, note the height above ground where the wind was measured. Wind speed increases with the height above ground. The relationship between wind speed and height above ground is clearly demonstrated in the Increase in Wind Power graph we scrolled past to get to the siting guide. In the graph, if the wind speed is 12 mph at 33 feet, the wind speed increases to 16 mph at 150 feet. That is a 33% increase in wind speed and, more importantly, a 78% increase in available wind power since the wind power is a function of the wind speed squared. If the wind data was recorded at a height of 50 meter (164 feet) above ground and you plan to install your unit at a lower height, the wind speed will be less. Likewise, if your tower is going to be taller, the wind speed will be greater.
Photo 5. University of Delaware 400-watt windmill (in the background to the left of the anemometer)
It is very important to choose a tower with the rated strength that can handle the particular windmill. The larger the windmill is, the greater the force on the tower. The windmill manufacturer should be able to give you the extreme wind speed force the tower must be able to support. With this information, the tower manufacturer can recommend what you should buy. It is best if the windmill manufacturer makes the recommendation. Get it in writing. Some windmill manufacturers also sell towers. Southwest Windpower sells guyed towers from 24 to 80 feet in length, specifically designed for their Whisper brand windmills.
Most people use guyed towers because they are less expensive than the freestanding towers and they are easy to install. The building codes in most states require towers to be constructed far enough from the edge of the property so that if the tower should fall, it will not fall onto the neighbor’s property. That means that if your property is only a hundred feet wide and the tower is to be installed half way between the property lines, the tower plus windmill blade length can’t be more than fifty feet in height.
Environmental impact — How will your neighbors feel?
Sometimes neighbors are annoyed when someone tries to be different. The surfaces of the first windmill blades I built for my windmill were polished aluminum. They reflected sunlight like a mirror. At times, the rotation of the blades on a sunny day flashed light on my neighbor’s windows like a strobe light. I painted the blades flat gray to stop the reflection. The second complaint came over a concern for their children’s safety on a windy day. What if one of those blades flies off or the pole falls over?
Incentive programs — How to get the government to pay some of your expense?
Some states have incentive programs whereby homeowners and businesses can get tax credits or grants from the state to pay for some part of the alternative energy source expense. To see what your state offers, go to www.dsireusa.org and click on your state (the abbreviation on the map). Click on any item to get details. Note that the top item on the page is the federal incentives. Particularly in states where the wind resource is not as favorable, if you can get the government to pay for half the cost, the project might be economical.
The types of windmills
Most of the electric generating windmills available on the market fall into two categories: dc output units usually used with batteries and ac output units designed for direct grid-tie applications.
The dc output units usually charge batteries. They can be used to supply dc for a dc system or specific dc load or used with an inverter to supply ac to specific loads or supply ac loads in parallel with the utility. The advantage of having batteries in the system allows for serving a continuous load from an intermittent source like windmills or solar panels. They can also feed a load that may not be on at the same time the wind is blowing. A perfect example of this application is the 400-watt windmill I installed on the roof of one of the University of Delaware buildings in August 2007. The Southwest Windpower Air X marine 46-inch diameter windmill supplies some of the energy for a 70-watt HPS security floodlight. The light is on every night from dusk to dawn. The windmill only produces energy when the wind blows. When the wind blows, which is not very often in Delaware, the windmill charges the batteries and the batteries store the energy until the light goes on. In this installation, if the batteries do not have the capacity to supply the light, i.e., the wind has not been blowing strongly enough, the control system automatically switches the light to the backup source, the normal utility service.
When the photo-control calls for the light to be turned on, if the battery voltage indicates the battery has capacity to serve the light, the inverter is energized from the batteries. The inverter converts the nominal 12 VDC to 120 VAC to serve the light. If at any time the battery voltage gets too low, the light switches to the alternate source.
The disadvantages of this type of system are the batteries add additional expense to the project, the batteries will have to be replaced about every five years, the system may not be able to keep the load in service during long periods of low wind speed, and the batteries limit the utilization of all the power available from the windmill. This fourth disadvantage is a serious one. The ability of the batteries to accept the energy from the windmill depends upon the charge level of the batteries. If the batteries are fully discharged, the batteries will accept whatever the windmill produces. If the batteries are close to being fully charged, they will accept very little. Even if the bank of batteries is properly sized for the windmill and the load, there will be times when the capacity of the windmill will not be utilized. For more information on batteries, see the article “Charging Into the Future” in the June 2008 issue ofSailmagazine.
Photo 6. University of Delaware windmill controls
Most of the ac output units are designed for direct grid-tie applications. The advantage of this type is that you can sell your excess power to the utility. Some utilities allow the kilowatt-hour (kWh) meter to go backwards when your windmill is producing more power than you need. If you buy energy from the utility at 15 cents per kWh, when the meter goes backwards, they are paying you 15 cents per kWh for the energy you sell them. Unfortunately, some utilities install a second meter so that they can pay a much lower price for what they purchase from you. The disadvantage of this type of system is that most of these systems will not work separately from the utility. If you are in a remote location where electric service from a utility is not available, you will have to go with a dc output unit.
What is available?
To see what is available, I recommend you read three articles, “How to Buy a Wind-Energy System,” “Wind Turbine Buyers Guide,” and “First Steps in Renewable Energy: for Your Home,” all available atwww.homepower.com. Click on Wind Electricity, scroll down and click on the above titles. The articles give details and prices. For additional information on individual manufacturer’s units, go to their web sites.
Additional information
Most of the manufacturers have extensive libraries of information available on their web sites. The American Wind Energy Association is an incredible source of articles and information. There is a very good 28-page introduction to wind electric systems available through their web site atwww.awea.org. Click on Small Wind, scroll down to Downloads-Quick Links and click on “US Dept. of Energy’s Small Wind Electric Systems.”
Please send me your comments on this article. If you have general questions about electricity, alternative energy sources, or electric power distribution, please e-mail me atdave@daveyoungengineering.comor call me at 302-633-1044.