Introduction: 3D Tesla (boundary Layer) Turbine As a Micro Kinetic Hydro Power System
This was my entry in the instructables "recycle" contest. I didn't get it complete and tested, for the contest, but I'm still working on it. I know it's not dancing cats, but it's useful, and I'll try to keep it a bit entertaining.
I've added the .stl for the rotor I'm using on this attempt. It's meant for the modified overboard alternators I'm using. If anyone wants a customized version, tell me what your plan is, and perhaps I can help you out.
I'm going to say some controversial things, and I'm not well trained in information transmission, or the propagandizing of it (marketing :-) ).. I'm not an academic, I am however someone who can get unusual things done. I hope you read far enough to understand that I have proven what I'm saying, and it's not that this turbine will displace conventional turbines, but that this technology may open up a variety of new low impact opportunities, and I feel an obligation to explore and disclose what I've found. The future looks pretty bleak if we don't diversify our energy supply. If you look deeply enough I hope you will see that in my more than a decade at this work, I have consulted with senior professional engineers in the field and they have given positive written opinions on my work. I can show, and have given up all the tools needed so people can prove to themselves that my VAWT technology(and improved versions of it) is going to be a useful tool in our future.
Theory of Operation - A Three Dimensional, or unfolded Tesla Turbine?
This is a complex idea and tomorrow (Jan 6) I hope to get a .gif I've made to help explain what I think is going on in terms of how the turbine interacts with flow when optimally loaded (TSR 0.8- 0.9).
Review of Tesla Turbine
For those unfamiliar with the flow in a Tesla Disk turbine I will give a quick review. A Tesla Disk turbine is a stack of disks, think of Cd's, generally 5 or more, just a millimetre or so apart. The disks are mounted on a shaft that can rotate, and the whole thing is in a housing. To make it turn, jets are positioned around the edge, facing the disk at an angle so the jet hits the disk at a tangent. The fast moving jet of fluid sticks to the disk and the friction causes the disk to spin, and more jets hit the disk, pushing the first jet inward in a spiral, in which all the jets follow. Around the axle are a series of holes, so the jets spiralling inward have a vent. This is a boundary layer turbine, so there is no "blade" and the energy is exchanged with the disk via boundary layer drag. The inward spiralling particles path gets shorter and shorter each revolution, allowing the efficient exchange of energy with the disk as the slowing fluid and disk remain in contact without shearing.
This will be more understandable with illustrations, which I hope to add tomorrow, or over the next few days, along with video's and data from the first round of testing.
Understanding the ART Turbine
This turbine evolved from my experiments with Savonius type turbines. The Savonius turbine have been misunderstood and mischaracterized since the 1970's Blackwell report published it's flawed wind tunnel study on it, but failed to replicate the study in the real world. Blackwell found that the optimal performance of Savonius type turbine of the Sandia Lab's optimized geometry ( A two bucket rotor about 2x D tall) reached 0.21 Cp, at around TSR 0.3. Blackwell, nor any other that I can find has replicated this result in real world, or in field tests, on the contrary in the real world independent results are closer to 0.10 - 0.05 Cp. This is explained in the Ian Ross "Wind Tunnel Blockage Correction Factors 2010" (add link)
A version of my design was independently tested in air and reached Cp 0.31 (around 3x-6x more energy captured than the Savonius. You can read more about my triangulated, or faceted version of this design, in my previous instructable, and even review my data where I found support for a Cp of 0.31 or greater at TSR 0.8 (insert link here, sorry reader, for now check my profile for the link). The best conventional, propellor or HAWT type turbines of this size might reach Cp 0.35, however they are sensitive to turbulence and output and longevity will be severely reduced in unsteady flows, and they must be mounted on tall towers for useful longterm output.
Kinetic Hydro, or Hydro Kinetic power converts some Kinetic (motion) energy in moving water to shaft power that can be used for creating electricity. It's a bit like a wind turbine for water, the flow moving around the rotor turns it, and there is no need for a dam or pipeline system to create "head" or water pressure, it just uses the existing flow. Most existing Kinetic Hydro systems look a lot like the existing 3 bladed MW wind turbine. This means they have some of the same disadvantages, like being very sensitive to flow direction and uniformity. With a conventional HAWT (horizontal axis wind/water turbine), the 3 long thin blades are very sensitive to flow differences between them. If one blade faces turbulent water, or slower velocity, it will drag on the other blades and stresses and vibrations will result. This means that sites must be carefully chosen, and many high energy sites will not be suitable. Some success has been had, but only in very specific sites, and so the technology is restricted from application to most of it's market.
In 2005 the EPRI released a study showing 15,000MW of Kinetic Hydro power available in North America. This is the largest sustainable energy opportunity since Solar Power, and interestingly, it doesn't require high tech manufacturing, it doesn't require clean rooms, it can be a simple, single moving part system. Since then dozens of companies have tried to develop functional small systems, but no real success has been had.
By Jan 6th or so, what I aim to have you find here is a 250W or so Kinetic Hydro turbine. This kind of hydro turbine doesn't need any dams, or impoundments to create a large height differential, instead, like a wind turbine, it just allows flow to pass through it, and collects some of it's kinetic energy as it passes.
I've been working in the development of a turbine technology that's based on the Tesla disk turbine, but expanded into 3D. It's a boundary layer turbine. You can see some versions of it here on my Drewrt page, or on my youtube page. This summer I created a triangulated version which, like the Tesla truck, has great though counter intuitive aerodynamics. The higher Reynolds numbers for a water version means it will be smooth, not faceted.
If you look in the files section you will see my test results of just the alternator at this point, and without a lot of editing. It's just me from floor sweeping to executive design decisions, so I focus on getting the work done and this promotional/educational stuff, I do my best at.
I'll post a video about the turbines later but if you look in my instructable profile you'll get an eyeful.
AlsoI should dig out my tests on the PMA as stock, but I also need to focus on getting this done.... always that tension in life.
I'm pretty excited by the results of my mod's so far, as stock these motors measured about 3V at 40 rpm, now at 40 rpm, I get 12V output!. A gentle spin of it by hand will easily blow LED's.
However the modification I've done was a bit crude, and It's output waveform, especially at low loads and resistances is quite messy now. I don't think this helps with efficiency. Another knock against it is that the current carrying capacity is now radically reduced, and it's resistance increased. It would not make a good motor now, however I seemed to find up to 80% efficiency (crudely measured) as a generator, and that is including the rectification losses. I think I can improve the waveform, by changing the way I've connected the coils.
Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: My Mods
This is a three phase star connected stator with 27 poles, 9 groups of 3 poles, each phase being 3 groups of three, and wound AaABbBCcCAaABbBCcCAaABbBCcC (cap clockwise wind). It is wound for short bursts of high current, 5 wires in parallel, (5 in hand), with 10 wraps, making 50 turns of wire around each pole. What I have done is separated the 5 in hand wiring, so each group of 5 wires per phase, 10 ends, were reconnected in series, no longer parallel. This was a bit messy, and I rushed and didn't do as nice a job as I would have liked to and may redo this one, do another. I didn't really think it would work, I thought I'd likely have to rewind the motor (although I do have some hopes from a few controllers).
In the end, it works pretty good, as I'll show you in more video's.
Step 2: Testing
The weather here is quite changeable, but this snow is going to be with us for a while. Today was round 1, just to see how it would react to the load, to check the mounting height, and see if the instruments would work as predicted. The flow in this creek is between 0.7m/s and 0.5 m/s at it's highest so all the kinetic energy contained in the swept area of the turbine is only around 12W, so this round of testing is really just to look for issues with the test equipment and get them sorted. I did collect some data that I should be able to calculate unloaded TSR from.
Participated in the