Vertical Windmills...

My 2 cents worth here as someone who owns a fairly big wind turbine--30 ft diameter blades on a 120 ft tower coupled to a 25 kw generator. Last night it was putting out 185 amps at 220 volts AC, for example which I sell back out onto the grid. It is a Jacobs turbine, a HAWT (horizontal axis wind turbine).

WHile I have not built a VAWT (vertical etc.), the majority (of course there are folks who argue differently) opinion is that VAWT's are a dead end idea, at least given the materials and technology we've got now. I see VAWT's brought up many times, in many different variations, but the numbers just don't hold up in the REAL world of wind. Early commercial attempts were a disaster and have not been repeated. Look for example at all the corrent commercial wind farms you see...not a single VAWT. There's a reason why. DOn't get me wrong: there are promoters of VAWT out there, passionate as all get out. The consensus is thumbs down, though.

Also, while the idea of using a electrical bridge between the turbine and propellor has been discussed here in this very interesting thread, I can't see how this would ever do as well as a direct mechanical linkage. Why? The best of electrical turbines harvest maybe 30% of the wind energy out there, and then even more is lost in conversion. Storing it makes it even that much worse as this old antique thing called a battery hasn't much changed since Voltaire days. Defiinately the weak link in the system.
Here's a pic of my house and turbine behind it.
BTW, I really enjoy the spirited discussions on this board and the all that comes with it, the jabs, the key pounding and even the heart-felt apologies.
regards,
~martin

 

if a sailboat had a turbine to run a electrice motor ,,,,is it still a sailboat?

 

Martin
I have been doing some calculations on a solar/wind power boat. At this stage I am working on using Etek motors with 4-quadrant drives on both water and air twisted foils. This way either can be used for propulsion and either for generating.

The beauty of modern electrical/electronic connection is that it has a wide gear range. A mechanical system would need much more complex gearing and linkages to continuously optimise. The Etek motors have a peak efficiency of 90%. Having batteries also mean you can store energy while at anchor either from wind or sun.

You are right that only around 30% of the wind energy is absorbed to produce mechanical energy and slightly less to electrical but you need to compare it with a sail. What percentage of the wind energy does a sail absorb and convert to mechanical energy???

I expect to be able to get 1.5kW from a 2.2m diameter turbine in 13m/s apparent wind. The blades I have will be loaded axially to 150N under these conditions. They have a design Cp of 31%. Taking the example of apparent wind abeam, then the axial load only causes healing. It does not oppose the water prop thrust. If the wind is more on the nose then the system has to handle more power but it still goes forward easily - even directly into the wind.

I have designed a slender hull that will require 1.3kW electrical at the motor for 7.5kts. The 150N will cause under 10 degrees heal on a WL beam of 1.2m.

By comparison I would need a deep canting keel to hold a sail upright on such a narrow hull. And there is no way of collecting and storing energy from the sail when at anchor.

The point is I see huge merit in electric powered systems. I also disagree on the batteries. There are significant developments going on with batteries; even lead/acid. You no longer have to worry about acid leaking or topping them up. They can be used in any position.

Rick W.

 

just saw a special about (enviorteck)I believe ,,,they are building a turbine in austrailia that is 2500 ft high,and can produce enough to run a city,,,with new designs ,with the same principals ,why cant a sailboat ,with mast turbine ,operate??,,,,,,,sails 2500...mast 1000,,,,,,,rigging 400 ,if you do it yourself.I would be willing to spend a little more for a turbine and rigg to drive her,longliner

 

I agree with you nearly 100%: VAWT are not competitive with HAWT for generating electricity and only a head-in-the-clouds bozo would consider a VAWT for that application. Just look at how much material is needed to make a VAWT compared to a HAWT. The parasitic drag of the radial arms is a killer, and vibration problems are still poorly understood.

There are, however, some esoteric mechanical applications where VAWT might be better-suited than HAWT: e.g. some pumping applications, compressing air, stirring large bodies of water, or extracting power from some tidal streams.

All the best,
Leo.

 

Well, you obviously know your stuff here and I'm not saying anything neg at all about turbine-driven sailboats--it's a fascinating thing--but, I'm still unconvinced about the electric angle of it all (though obviously it is easier, gearing-wise than mechanical). 1.5 kw isn't much power really. I'm not an engineer, but doesn't 1.5 kw covert to about 2 horse power? Wouldn't push much of a boat, especially if you were wanting to go into the wind, but maybe I'm missing something.

Also, yes, batteries are getting better, you're right about that, but out in the applied world of batteries they're all kinds of headaches related to battery life, charge memory, sulphating. IN fact, most folks off the grid by a cheaper set of batteries for their first go at things, say golf cart batteries, to "learn" on and make their mistakes with, before buying fancier batteries, and still, there's headaches involved. The cutting edge of batteries the auto industry is developing look promising, still there's the cost, the weight, the life span.

There I've definately thrown in my 2 cents...and that's about all I'm good for. I've got SO much to learn about boats, and pretty much just lurk and read threads, but the wind turbine thing allowed me to add something, I hope, for the greater good.
~martin

 

Re Flywheels -
This technology could be due to be replaced by a new form of battery, a "Flow Battery"
This technology brings large scale power storage back into the battery technology.
It is already being used commercially, and will soon be available to the average user.
A good start for the explanation of the technology can be found at
www.science.org.au/nova/newscientist/037ns_001.htm
Compared to the engineering difficulties associated with flywheels, this should be a much 'friendlier' solution.

 

Martin
Just to keep the debate going.

I have attached some views of the proposed boat. The one with the top off is the latest model. It is a challenge to get usable space in a slender hull. It is 48ft long and 5ft wide overall. Going into a wind is actually an advantage because you get more power than needed from the wind turbine. Irrespective the boat has low windage.

I have been doing a good deal of experimenting to learn design basis and validate theory on hulls and props in the last few years. Today I ran my first test on an electric boat. I just put a 300W scooter motor on one of my old pedal boats. (See photo and video) The prop was not pitched correctly to get the full rated power of the motor but I achieved 8.5kph with 160W out of the battery. The hull requires 90W to do this speed in calm conditions. So overall efficiency from battery to hull off 56%. The motor has a peak efficiency of 78%. The prop efficiency is around 80% and there are some small losses in the controller.

The Solar/Wind boat will have 8 off 12V X 120Ah batteries configured for 48V. They provide 288kg of ballast to stabilise the narrow hull plus something like 11.5kWh of storage. I take your point about cycle life and hope to avoid frequent deep cycle. My aim is mainly coastal cruising between sheltered anchorages on a day-to-day cycle.

The Etek motor should enable me to get a top speed of 12kts but it would not be good for the batteries to do this for more than a few minutes.

We have had power to burn in the past, literally, and have not got very smart at designing for low power and good performance.

The proposed boat is really a 20ft boat with fairing on either end to reduce wave drag and provide collision protection for what will be a lightly constructed boat. My target is 1 tonne including the pilot. The ends will be removable for trailering and storage.

Rick W.

 

Most interesting design, Rick. Keep us informed.
Thanks in advance.
Cheers.

 

I saw on the TV a generator concept model that had a flat rubber band, that had been cut and stretched out. A little bit from one end was a fixed coil and attached to the rubber band was (I suppose) a magnet. When a fan was turned on as the wind source, the rubber band started vibrating up and down which drove the magnet up and down in the coil, which generated enough electricity to light a small bulb. The idea was it would be dirt cheap, there were no "moving" parts and no energy lost to friction, etc. I believe there was an article in Popular Mechanics or something maybe from MIT.

 

Rick,
I'm very impressed, not only with the concept, but also your efforts to get it off the paper and into water. Good stuff.

When I saw your video clip it reminded me of when I was a kid, I put an electric trolling motor on the back of a sea kayak. One auto 12 v battery would keep me cruising all day, and at a pretty good clip, too.

Here's something to think about: Instead of relying ONLY on batteries as a back-up, what about a very small gas/diesel/propane generator? You could have that and batteries, too. Wouldn't take much of a generator at all and that would save your skin if the battteries got low and you needed to get somewhere, or if you needed to go a long distance and wanted to save your batteries (remembering that deep discharging the batteries is what shortens their life span).

It's akin to folks off the grid whom rely mostly on wind and solar for their power needs and have battery back-up. pretty much 100% of them also have a generator of some sort.

It's still amazing to me how much energy is stored in one gallon of fuel. Just the other day, I was digging ditches with my backhoe and stopped and considered how long that would take me to do this by hand (days) and yet I hadn't burned but 1/2 gallon of diesel. Of course, this is how me got into the energy crunch/global warming mess to begin with! So, I appreciate your efforts to work outside the prverbial box. Definately keep us posted on progress and if there's any assistance I can provide regarding turbine design or selection, etc. give me a shout.
~martin

 

Hi, it looks nice, but how is it's ability of catch the energy from the wind, with how high effeciency?

 

As noted earlier the turbine has a Cp of 31% at design conditions. The blade design is optimised to minimise axial load for the best power output so power efficiency was not the driving factor. The diameter is only 2.2m so if I find I cannot get enough power in the typical wind conditions then I will make bigger blades. The swept area is much smaller than the sail area to do the same job.

Rick W.

 

If i remember it correctly, this type of turbines are called Darrieux Turbines.
A different version also called the Musgrove Turbine.
The variable geometry vertical axis windmill- P.J. MUSGROVE
Also see C.A. Marchaj- Adlard Coles.

 

There are some papers (including a PhD by my colleague Brian Kirke) at:
http://www.cyberiad.net/vawt.htm

On the same page there is an extensive bibliography of papers on VAWT (Darrieus turbines, giromills, cycloturbines etc) as well as references to some mathemaical modelling methods and engineering.

All the best,
Leo.