New Energy Watch

Lieb's VAWT Design Proposals

We recently received a letter from inventor Paul Lieb of Norton, Ohio, excerpted below. Readers familiar with the technical niceties of vertical-axis wind turbine (VAWT) design are invited to comment here or contact Paul directly at his website.

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I would like opinions on the difficulties and the potential of my designs. I have not built any prototypes but I filed a provisional patent for a VAWT with 4 blades linked in pairs.

The first design example (below, top) will begin producing power at lower winds speeds by using the direct force (drag) of the wind hitting a large blade. The RPM will need to be controlled by a variable-draw generator so it can produce more power at high wind speeds, because if the wind speed is faster than the blade tip speed it is not efficient. These would be extremely efficient for their size. I hope these drawings provide the detail needed to understand its workings.

My second design (below, bottom) is one that will change automatically from the Savonius style above to the Darrieus style that is efficient at wind speeds that exceed the blade tip speed.  It combines the functions of both high- and low-speed wind turbine designs.

Here are some options worthy of note:

1. Bending / rounding the top and bottom 1/4 portions of the blades will increase output at lower speeds
2. Extending the blades past the hinge point (changing the pivot points) may improve performance
3. Changing blade height to width ratios – changing diameter to height ratio
4. Different styles may be ideal for different locations – telephone poles, on roofs, between buildings, wind farms etc…
5. Any number of support arm and links can be used.
6. Should be economical to produce with minimal tooling

Considering that prototyping and commercializing are expensive beyond my reach, I would be most pleased to work with a company or discuss licensing or sale of patent pending.

 

Wind Power Where the Deer and the Antelope Play

In 2006, Texas became the leading wind power state in the country, just edging out California. According to the American Wind Energy Association, at the end of 2006 there was enough wind energy coming out of the Lone Star state (2370 megawatts) to power 600,000 American homes.

Ironic, isn't  it, that the state synonymous with Big Oil is leading the charge into the future, while the hand-wringers of Nantucket talk a big enviro-game but won't countenance wind turbines in their own back yard?

Of course it's more complicated than that. But no matter which way you cut it, it's ironic. And the questions remain: Are we at war with terrorists who depend on oil money, or not? Is global warming urgent, or not? If we are indeed locked in a battle on these two connected flanks, then we need to get serious. Not interested in having a wind turbine in your back yard? Could we interest you in the 55-mph speed limit? No? How about gas rationing and a return of the draft?

The people who ranch and farm and live in the plains of Texas north of Amarillo and south of the Oklahoma panhandle are serious about these things. They want wind turbines on their land so as to thwart the terrorists, do right by the environment, and make money -- all valid reasons in whatever order they come on a given day.

Last summer (2007) we had a chance to help the folks at Lorax Energy and Higher Power Energy LLC set up two meteorological towers in Texas. Here are a few photos. One shows a 60-meter (200') tower in the early stages of assembly; the next shows the tower rigged and almost ready for hoisting; the last shows the tower upright, before the guy wires are fully tuned.

These towers are tall but skinny. With the use of gin poles (a 50-foot one to lever the main tower, and a shorter one to raise the main gin pole) they can be hoisted with a farm tractor.

Meteorological (MET) towers gather and log wind data at several levels, and are typically left in place for months, or even years, so that wind-power companies and investors can determine whether an area or a specific site will be good for wind energy. If our experience was an indicator, the Higher Power Energy sites will be great. As someone on the crew said, working on these plains at the height of summer is like standing in front of a giant blow dryer.

~ Doug Logan, New Energy Watch

Wind generators: horizontal and vertical both needed

Good comment from Jeremy Stieglitz at Wind-Sail, Inc. on the relative merits of horizontal-axis versus vertical-axis wind generators. The point is that neither type will necessarily trample the other in the marketplace. Both types have their strong points, and raw wattage output is only one of them. As mentioned elsewhere in this thread, the VAWT hits its stride in tighter spaces, low-wind conditions, and in other circumstances. Read Jeremy's comment in full here. Also see his blog, which includes valuable discussions of energy policy, and highlights some of the concerns, obstacles, and incentives faced by green energy start-ups these days.

One last thing: The HAWT versus VAWT discussion is another example of the fact that the energy future will be reached by many paths and efforts. All reasonable, honest efforts must be encouraged, and all helpful paths recommended.

~ Doug Logan, New Energy Watch

Quietrevolution discussion

Robert Webb, CEO of XCO2, kindly responded to some of the earlier discussion about his company's wind turbine, the Quietrevolution. His response to Henry duPont's comment that vertical-axis turbines are less efficient than horizontal-axis machines:

"It is not true that HAWTs are inherently more efficient than VAWTs. There are good aerodynamic studies showing the efficiency is similar in theory. The issue is simply that to date vastly more has been spent on developing HAWTs.

In fact for small scale applications near the ground, where the wind is turbulent, we predict a 20% to 40% better output for a VAWT due to responsiveness to rapidly varying wind conditions."

We would welcome a deeper discussion of the engineering and aerodynamic challenges involved in wind turbines. In the meantime, there's a lot to be said for any alternative-energy product that brings aesthetic satisfaction along with its other benefits. Such an edge can make all the difference when someone is contemplating the installation of a wind machine. The same can be said of lightbulbs, solar panels, and  other products. If someone has to sacrifice 25 percent of efficiency in order to put up with a switch to an alternative source in the first place, he's still 75 percent better off than before.

~ Doug Logan, New Energy Watch

VAWT versus HAWT wind power

Henry duPont of Lorax Energy Systems in Block Island, Rhode Island, dropped by electronically to  enlighten us on the matter of vertical versus horizontal axis wind turbines (VAWT versus HAWT). 

Henry says the advantages of the VAWT configuration (like the Quietrevolution elsewhere in the Wind Power section ) are that the generator and gearbox can be housed on the ground, and even some distance away from that turbine; and that a VAWT is omnidirectional and requires no yaw mechanism.

The disadvantages of typical VAWT systems are that they usually operate near the ground where there's not much wind; they produce wavy (sinusoidal) power pulses to drive mechanism; they don't start themselves in a breeze; and repair of the main bearing usually means having to take the whole machine apart. (The Quietrevolution appears to solve at least the first problem by being mount ed on a tower.) Most importantly, the VAWT is typically about 40% less efficient than the HAWT in energy production. According to Henry, you would need a VAWT almost twice the size of a HAWT to get the same amount of juice. 

The main advantage of the HAWT is the increased efficiency in power production, and the smooth transfer of that power from the rotor to the gearbox. HAWTs are also generally mounted on taller towers, where they have exposure to higher wind velocities and present smaller footprints on the ground. However, they require tall cranes for set-up; they require a yaw system; and any maintenance required has to be done at the top of a tower. The photo here shows Henry duPont's colleague Kim Granbery at altitude during the installation of a new HAWT above the Western desert.

Wind turbines - horizontal versus vertical

There's a terrific discussion at renewableenergyaccess.com related to the post above about the Quietrevolution wind turbine.

There's no question that noise and aesthetics play a role here. In some settings, people will be willing to deal with lower power output in return for a smaller footprint (airprint?) and a happy neighborhood.  In a crowded harbor, a sailboat with a wind turbine moaning and chattering all day and night can ruin the place just as easily as a gasoline or diesel generator being run at all hours of the day to charge batteries. The same would be true of noisy wind machines on the tops of residential buildings in cities.

Henry duPont, what's your take on this -- are vertical-axis turbines inherently less efficient that horizintal-axis ones? What are the trade-offs?

~ Doug Logan, New Energy Watch

Quietrevolution QR5

A British company called XCO2, based in London, has developed (have developed, as the British say) quite a beautiful helical wind turbine called the QR5, made of carbon fiber, with only one moving part --  the blade assembly of curved S-shaped foils that rotates around the support post.

It's a big machine. The blades themselves are 5m tall by 3m wide, and the bottoms of the blades are 9m off the ground. Total height is 14m, or about 45 feet. The turbine is designed to be almost silent, and relatively compact for its output, with the idea that it will serve well in urban settings where winds can be low in speed and and fluky in direction.

Maximum windspeed is 16m/s, or about 26 mph; it shuts down automatically above that speed. It begins generating power at 4m/s, or about 9 mph. There don't seem to be any electrical output figures or windspeed curves on the site, at least that I can find, except for a blanket estimate of
10,000 kWh per year at an average windspeed of 5.8m/s (13 mph.) That would be a bit more than one kilowatt of output, if my calculator is working right. I'll see if I can find out more about that from XCO2.

The cost of one of these things, including installation, is over $50,000 at today's rates. That's a bit of a showstopper, with a long payback time. It would be really interesting to see if they could make, say, a 200-watt model for a fraction of the cost, to compete with some of the smaller two- and three-bladed wind generators on the market.

The two pictures shown here are from the XCO2 website.

~ Doug Logan, New Energy Watch

Small wind turbines

Big wind turbines are sprouting up and tying into utility grids all over the country. More power to 'em. As for small wind turbines that are used to charge DC battery banks, we've seen a lot of them at work on sailboats, but only a few used on home sites or jury-rigged on parked RVs.

Success of a small turbine for home use depends on how hard the wind blows in your area year-round, whether you're sited well enough to take advantage of the wind, whether you can mount the thing in a place where the noise won't bother you and the neighbors, and how interested you are in making batteries and DC power part of your life.

Here's the U.S. Department of Energy's page on wind power: Wind Energy Technologies.

One of the most common small turbines is the 400-watt Air-X, made by Southwest Windpower. In fact, the company says it's "by far the world's number one selling small wind turbine." The Air-X starts producing current at 8 mph. of windspeed. It's a bit hard to read the power curve on the PDF spec sheet, but it looks like it  produces 5-6 amps at about 15 mph.

Small, fast-turning turbines like this are, to my ear, pretty noisy when the wind pipes up. But noise is a subjective thing, and much depends on where the thing is located.

There are plenty of competitors. If the expertise of the dealer is an indication of a good product, then the KISS High Output Wind Generator deserves a look. It's made in Trinidad and and distributed in North America by John Gambill of Hotwire Enterprises. The KISS is engineered to work well at relatively low windspeeds. For example, it kicks in at at about 6 mph. and produces about 4.5 amps of current in 10 knots (11.5 mph) of wind, and 10 amps at 15 knots (17.3 mph.)

If you're more serious and you have some elbow room, you can take advantage of the larger stand-alone wind turbines, like those made by Bergey Windpower Company.

If you have experience with stand-alone wind turbines, click the "Comments" link below and fan the knowledge.

~ Doug Logan, New Energy Watch