Thank-you for a most excellent article.
There are HAWTs, Savonius and Darrieus, and variations of these.
Now if you could just get everyone to stop switching the efficiency labels for the Darrieus and the American Multiblade (a low-efficiency, high-torque type of HAWT) from that 40 year old magazine article graph that keeps getting reprinted...
Excellent information. It's gotten quite annoying to see one of these "inventions" about every other week on some blog or another.
Great write-up. I am particulary skeptical of the flying kite generators. Your summary of the required easments and the obstacles they produce in a real world application puts it in perspective. What happens when the 4 KM kite descends with its carbon-fiber kite string falling across high-voltage power lines? (AT&T Austin smacks his forehead) That's right, Austin.
I'm amazed that people can actually get funding for some of these projects. When you do the math on biomass energy, the entire continent could be a switchgrass farm and it still wouldnt meet our energy needs...so why fund the research? Captital Investment Analysts must be morons.
50 nuclear power plants on 50 military bases in each of the 50 states equals clean, safe and domestically generated energy...its not complicated.
Thank you, Mark, for an informative and credible article. I didn't know about the Betz limit, which must rank pretty much up there with the laws of thermodynamics.
My favorite goofy idea is the strawscraper, typical of the hot wind emitted by architects.
now i suggest you write the same article telling us off-grid wannabes without all the research data how to pick a wind generator system for 5 to 10 kw.
and keeping the price low. in the spokane, wa area there is a mfg. claiming reasonable power output at lower height. how can we users tell whether their product is worth buying?
it called physics and the limits to efficency ... for the most part these "new" turbine projects are simply grant or funding cons ...
if you really found a "new" way to harvest wind energy you wouldn't need tax credits or pie in the sky press releases ...
So, wondering how the Blackhawk TR-10 VAWT from BHWE (www.blackhawkwindenergy.com) stacks up to these tests. It's a variant of a Darrieus design that claims certain improvements (exhaustively delineated in this video: www.youtube.com/watch?v=C3a6LAzNsds). It all sounded logical to a lay-person like me, but maybe you have an opinion?
Great article! Finally something debunking these perennial dead ends. The one case I would disagree on is the Makani Wind flying turbines. I suspect the reduced costs and speed of installation, flexibility of changing sites and ease of scaling will help it succeed (along with Google's cash). Of course the sites for these will be in deserts and in the ocean because of the issues mentioned, but that is just fine because there are plenty of both.
Wow, best article I have ever read about wind energy, or just about any topic for that matter! Three investigative techniques really impress here.
1) The review questions is something actually new! Google has made patent searches so easy we should all be doing them.
2) The review questions whether the something is actually useful!
3) The review looks for coroborating 2nd source info for the new useful something. And if that is not available, at least compares claims back to basic public info.
Thanks so much Mike Barnard!!! Keep up the phenomenal work.
Blackhawk has an excellent video. Very informative and it appears correct without exaggeration. This is a conical vertical-axis lift-type (Darrieus) wind turbine. I lived on a sailboat for eight months, so I very much liked the sailboat analogy.
A couple down sides: one is the complexity of the mechanism; can it be made at a reasonable cost? and how long will it last between maintenance? (More parts is not necessarily a bad thing. Adding parts can increase the dependability of a mechanism. But more moving parts can mean more maintenance.)
The biggest downside right now is the "Account Suspended" I get when I try to go to their web site.
What I am skeptical of is this article. In particular, item #1.
Don't misunderstand me: before we go overthrowing established "laws", we do need good EVIDENCE that the phenomenon is real.
But what we should NOT do, is ignore empirical evidence simply because it SEEMS to violate existing "laws". Remember, those laws themselves came to be because someone overturned previous knowledge. And that process continues, whether you like it or not.
I am not accusing the author of falling into that trap. Maybe, maybe not. But I am warning people that what has often passed as "skepticism" lately, on both sides of many arguments, has instead been been just automatic rejection of new ideas because they contradict the old. That's not "skepticism", that's denialism.
To be clear, and to put this concept in simple terms: an objective judgment has to be based on EVIDENCE. Rejection of evidence because it contradicts prior knowledge is not "skepticism". If it were, science would never advance.
The Blackhawk VAWT is not in production. Latest information on it is at http://www.boatnerconsulting.com/index.html#blackhawk, but I talked with Bruce Boatner on the phone and there are no current plans for production.
A good article, but with a couple of mistakes. First, LCOE stands for Levelized Cost of Electricity, not Lifecycle, and does not generally include decommissioning costs. (We've corrected this error. Thanks, Ed.) Second, even buyers of nuclear power plants recognized the need for storage -- they built over 20 GW of pumped hydro storage in the U.S. alone primarily to allow non-variable nukes to service a variable power demand. And nukes have far less need for storage than wind does. Wind proponents have been denying the need for storage for many years with arguments that are dubious, at best. We will never achieve the full potential of wind (and solar) energy until large-scale storage is accepted as a critical system component.
Mike, I just what to join in with the chorus of appreciative readers for a well considered clear-eyed overview of the often superhyped field of wind generation!
Anne Ominous has it right. What Anne did not elaborate is the damage you and people like you do the whole blogger community. It is articles like this that make us all look bad. Please come to your common senses. Review the credential of the people involved in these companies, the very companies that Mike has totally dismissed. They may not have the answer to all Qs, but who does when starting a new idea. These people are highly educated with much success under their belt. Sitting in front of TV and writing this trash on them does not do anyone any good. The only damage is to our own blogger community. I hope others read this kind of information and as they check the companies with new ideas, they check the author and ask the right Qs. For example, what are his credentials?
Mike writes about Betz limit as if he has read the paper and knows the assumptions that have gone along with it. If he would have done his literature review, he would have found out that many researchers in academic (not those who are rolling new ideas out), researchers at respected universities around the globe have written on Betz limit that has its limitations and does not apply to all cases. But that is to the side, if someone claims they generate more energy it does not mean they must violate any law of physics of other theories to do so. For example, lowering the cut in speed will result in significantly more energy output, and this has nothing to do with Betz limit, for example.
I too want to praise the quality and relevance of this article, which had summarized cleanly information it is hard to get otherwise without going to half a dozen places and reading a lot of technical stuff.
Does this mean that from now on when Gizmag has an article on a new turbine design, it will properly assess its real-world potential?
Also i have a real soft spot for high altitude designs. 'Offshore' doesn't have to mean 'niche', right? Since once upon a time airships were filled with hydrogen, doesn't that mean hydrogen could be used with them, too? Surely there is a lot of space for not-so-incremental improvements in their design. HAWTs are getting higher, but there will always be a major difference in the altitudes and thus the wind speeds a HAWT can reach compared to a tethered device. Personally, i'd love to see an article on that subject specifically, since i lack an engineer with expertise in the area that i can bug.
Great to dispel the sales hype. JBar, nuclear is far from simple, and all nuclear does is boil water, just like coal. It cost more too (most coatings, like coal, do not include waste disposal and then there the government subsidies)
That said who really cares about Albert Betz limit. There is plenty of wind out there.
The most important thing is $$$ and resources. Get the most power with the lowest capital investment and running cost is key.
If something is 10% more efficient but cost 200% more who cares.
Watts per dollar is what matters everything else is completely pointless.
No I don't care what it looks like, if there are vibrations, if bird are killed, none of that matters to me at all. Trains cause vibrations yet environmentalist advocate for mass transit. Windows kill birds but leftist always boast about natural light.
Alternative energy needs to be profitable.
@Jim Fiske: thanks for the catch on LCOE.
Please note two things about storage:
1. I wasn't writing about generalized grid backup, which is required in amounts at least equal to the largest generation unit in the event it or its transmission lines fail, but specifically about storage integrated into a specific generation unit or tied uniquely to it.
Wind has reached penetrations of 25-50% of demand in jurisdictions such as Texas, Spain and South Australia without specialized storage being required. Carbon neutral storage is a serious component of a carbon-neutral grid, but we are a long way from that moment, unfortunately. At present, grid interconnectedness allows electricity to slosh around between jurisdictions, occasionally even at negative prices, and all forms of generation to support one another. Coal generation is usually the first to be priced out in most market schemes, which is good, but inadequate. Note that storage is only one of the forms of grid backup.
Good correction Jim.
In addition to the error on LCOE, there are so many more things wrong with this article. Basically it does not make an engineering or scientific argument, all it does claims that 3-bladed system with 100 meter diameter on the top of 125 meter tower is the optimum way of converting kinetic energy of wind to electrical power. If that was true, why is it that after 30 years, wind industry cannot survive without government subsidies? Why is it that most investors in wind space lost their shirt? Why is it that most large wind developers and equipment manufacturers are going out of business or have cut their work force and facility by 50%? Of course the current system does not make sense. Just use common sense. In a 700 MW natural gas or coal power plant, there are 2 to 3 large generators. In the case of 700 MW onshore wind power plant, there are 200 to 350 turbine generators. Wind industry has tried to compete with fossil fuel by equipment concentration that has turned to be inefficient and costly. Do we even have any idea how large 125 meter rotor is? The wing span of 747 is about 72 meter. 30 years ago, if someone would have told us one day we will have the largest rotating structures ever, bigger than 747, be mounted on the top of 125 meter tower (as big as 40 story building), we would have said no way. This trend has been a wrong one from day one.
We do need new ideas. Many of these ideas have certain application, even though there is no universal solution yet. One thing is clear; the current wind industry is where main frame computers were in 1940s. They can support many bloggers to shut down all the new ideas, but the reality is that their time is up. We do need a new mouse trap and must encourage those who are braver than us to give it a try; instead of becoming only a no, no, no people, like the current congress.
The worlds helium supply is not running out.
Lighter than air is not helium dependent, hydrogen provides more lift but leaks more and ammonia and methane leak less bur require more volume for the lift.
re; FrankForst / Anne Ominous
Extraordinary claims require extraordinary evidence. Therefore extraordinary claims should raise red flags.
Hmmm. Decent article. Still disagree with item #1, but then again, no wind machine has shown outside of a lab and/or controlled test to exceed .593, although water turbines do it routinely-Hydro baby-is the Big Daddy Renewable Energy Machine, but flow and volume are controlled and finite unlike the wind space.. get it ...controlled flow and density change.
100% disagreement on GE. Nothing brilliant about their machines at all, even with storage, only brilliance is their virtual monopoly on Big Wind in the US. How did they acquire it? They bought the wind turbine line from Enron, who had acquired it previously from Zond.
For every wind turbine GE makes, they sell 5 gas turbines. GT's that are used in onshore/offshore hydrocarbon extraction, natural gas facilities, coal mines..yeah...how about them facts. None of their manufacturing facilities domestically are powered by renewable energy sources. That means the larger the project, the more emissions they put into the atmosphere. Those wind turbines they sell take 2-3 years to offset the CO2 that went into making them...'effn Brilliant. Offsetting CO2 is not a sustainable or renewable process. All the while the GT's that they sell are spewing Sulfur oxides, Nitrous Oxides, CO, (the other GHG's) Particulate Matter, VOC's that are just as lethal as CO2, if not more. How again is it that you surmise that GE is a renewable or clean energy company again? They may as well just stop making wind turbines, because they sell more GHG emissions machines, which are far more profitable. If you are going to give them credit for an expansive wind turbine line, then credit them also as the largest GHG purveyor in the US. Last time I checked VESTAS make only wind turbines as do most other top 10 wind turbine manufacturers-non US. Fact check me pls.!
Nothing brilliant about GhgE!
Nice writeup, but do I detect a whiff of special pleading? The down sides of HAWTs (avian death, disrupted migratory pathways, etc.) are now well known. In the midst of all the hype about new generation technologies, I wish gizmag would at least *consider giving equal time to the far-more-promising technologies of conservation. A GW saved is a nuclear plant unborn. For obvious reasons (cost, carbon footprint, waste storage, potential disasters) this is a win for us all.
Lux Wind Power happens to be one of those companies claiming to have a better machine to extract power from the wind. If we make assumptions that the status quo is great and change is not necessary because big companies are hugely innovative and must be doing it right, then we are in big trouble.
Thirty years ago, three bladed turbines were small and expensive to build. While energy prices were soaring, many researchers were looking for the perfect machine to extract power from the wind. The horizontal axis wind turbine did not pop up as ‘a great design’, but more like ‘lets use it because nothing else works’.
The problem then, as it is today, is that the tower and the three blades are cantilever beams. Cantilever beams are supported at one end only and therefore, require excess material to withstand the external forces exerted on them. Try operating a broom with only one hand at the end of the handle. This is simplistic, but describes exactly the fundamentals of cantilever beams and why they are rarely used.
Thirty years later, we are still using a bad design and you are telling us that we should not try to do better! The large rotors, positioned high in the sky, is the result of billions of dollars of research. Engineers have done a wonderful job lowering the LCOE using this design, but that should not preclude innovative thinking and the search for the best machine possible.
I agree with the points mentioned in the article, that the majority of the articles written about new turbine designs are clearly unproven and wildly exaggerated as scientific breakthroughs. I could also be accused of exaggerating unproven claims, at luxwindpower.com, however, when all the research points in these directions, is it wrong to suggest that these attributes are possible? Is it wrong to state that our turbine is anticipated to be 1/2 the cost mainly because the weight is 1/3 the weight of a conventional turbine, delivering the same power output annually?
Can we prove these advantages beyond any doubt? Of course not, because our largest prototype is under 100KW and the proof will only come when larger models are built and tested. People viewing our website will draw their own conclusions just like I do when I visit other websites. I believe our research is important and we will continue to explore all possibilities despite being categorized as ‘Dodgy wind’.
So let's fact check the mobile un-ducted turbine system that appears to be the "good bet"
Patents - check
Design - check & un-check (STAR does show a 12% improvement over Zond turbine blades where they were tested @ 50meters diameter!!! not at the small scale shown for the Mobile system. BTW Zond blades are c. 1980 turbine blades, so new planforms with sweep and twists can also outperform the old Zond as well. Most newer blades can outperform a Zond.
Design Team: AOK
Independent Certification @ the scale of the mobile system featured-un-check.
Where is the independent testing and cert on the small scale mobile system. Cant find the swcc certification for it. Post the link pls.
Cost: $240,000 USD for 50KW mobile systme - uncheck
Yes, we have successfully integrated a lot of wind power into the grid, but we need much, much more. Making that work will require an immense amount of back-up power from various types of plants. It's not generally known that bulk energy storage is not only technically superior to fossil-fueled power plants at providing that back-up (it ramps far faster than even simple-cycle combustion turbines and throttles over a far wider power range), but also much less expensive. It's also carbon-free. If you want to see what I mean, take a look at the storage systems described at www.gravitypower.net. If you would like to learn even more about those systems, let me know.
@MAC- Spot on. Conservation is key. We as a culture (US) have to fundamentally shift our way of thinking on consumption. It is the simplest way to reduce GHG and the cost of electricity whether they be from non renewable or renewable sources.. What's the LCOE on conservation $0. It costs nothing. Look at the average household electricity consumption in the US,
it's disgusting and there is simply no need for such gross consumption. I reside in New England, MA to be exact- the lowest regionally in the US. My household consumption this mo. was 275kwh for an average single family home 2.5 stories. I have the best smart meter installed...fingers that turn off lights, appliances, etc. There should be no need for expanding fossil fuel power sources or renewable power source. It is to be quite frank, a pointless vicious cycle that has no return. The energy shell game. Despite the global uprising in renewables, GHG charged to 400ppm last month like a bull in a "China" shop. Absurd!
Open the windows and turn off the damn lights! It doesn't hurt to sweat
And to the machines: Kudos to Altaeros Energy for making that bad-ass machine fly, in -10 degree Maine weather, Great job to FloDesign for pushing the bounds of physics and re-introducing the ducted turbine with mixer ejector technology and putting up on Deer Island so we could all see it "work", even if not to spec., To Makani-Aloha Nui, space cowboys - get that bird to work! @ the author- your not an expert in aerodynamics, fluid dynamics or hydrodynamics
@ Lux: OK here's a cursory comparison from all I could find on your site.
(1) the cost is low if you build at ground level. That needs good ridge siting where most good sites are already in use. Also bird strikes are more common at low to the ground level. Pillars to obtain clean, higher airflow might be better but raise the cost per turbine.
(2) wire stability was used in biplanes at an aerodynamic cost that was quite high. Hence modern aircraft, even at slower velocities are most efficient as internal structure cantilevers. We do have a lot of experience building such structures.
(3) So you say build more turbines per square hectare? Where then is the cost savings if you have to build four turbines at ground level to produce the output of one large, high turbine even if your turbines are just half the cost per unit?
I don't think I will be investing soon, though I would love to be proven wrong once you scale your design into the same regime. Good luck.
Thanks for the comments and I do understand why you are sceptical. The total concept is difficult to explain in a few sentences but I will try.
First of all, our rotors are inexpensive to build because they only consist of aluminum extruded blades and cables. So building a rotor with a larger swept area does not significantly increase the total cost. The goal is a low cost/kwh, which does not necessarily mean high efficiency.
Secondly, the aerodynamic drag from the cross cables is not a significant factor, as most people believe. We were reluctant to try the use of cross cables, for the reasons you mentioned, but after a few experiments, their benefits were clearly obvious.
Our turbines reach the nameplate output at 9-10m/s. The annual power output at all average wind speeds is increased substantially by using a larger than usual swept area for each turbine size.
You are right about building turbines at ground level. If they are not cost effective, building more will not remedy the situation. We believe it is possible to build large turbines 2MW and bigger, in close proximity, therefore capturing more power per given area. The benefits from Dabiri's work on this topic is quite clear and should not be dismissed without careful consideration.
Our 2MW turbine has an expected equator height of 85 meters which is close to the hub heights of other turbines. All of our calculations take into consideration hub and equator heights, so these should be true comparisons. Accordingly, our 500KW turbine has a much lower LCOE than the largest HAWT built today.
The benefits of this design are clear to us and it is our duty to provide the proof. I do not expect everyone to be a believer, but I do ask people to keep an open mind.
HAWT designs (of GE etc) are good but they still need big improvements:
1) Make them gear-less because as the article pointed out gearboxes add huge cost (both up-front and for maintenance).
2) Make them able to work at high winds because those are the times which can produce most power.
@LUX. One item to consider to, and I am sure, you have, is to increase the thickness of the foil, or actually incorporate a foil into your design. A simple non-proprietary foil developed by Russian aerodynamicists, Joukouski (and FX series), are quite easy to replicate. Start at 15% camber thickness as a baseline and then optimize the foil geometry based on the local wind speeds at your test site. The challenge of the Darrieus design has been been in overcoming the lead/lag drag function of the blade travel which typically , although not always, limits the tsr >>>to overcome the lead/lag governing that of course limits the rotor rpm of the eggbeater design. Plant some solar panels at the base to power the pumps or pull power off the grid. The advantage may be to keep the tower height down-keep the cost down- by reducing the amount of CO2 intensive steel needed for taller towers, not to mention shipping costs, etc. Just a thought!
@author--Frederick Lanchester (UK)first derived the maximum efficiency of power extraction from a propeller or airscrew in 1915, Betz (Deutschland) did it in 1919, followed by Nicolas Joukouski (Russia) in 1919/20. WWI is the reason it's not called the Lanchester Limit. The correct scientific term is the Lanchester-Betz-Joukouski limit.
So a Russian, German and an Englishman walk into to a bar....
@LUX. The solar panels are to power the dc micro air pumps that could be embedded in the blades which is active circulation control wing technology, ACC may provide an advantage to the Darrieus design in overcoming lead/lag rpm governing of the blade which limits the eggbeater tsr. Just a thought.
Great article thanks! I'm going to flick this URL to a bunch of people. I understand that it's got a few inaccuracies but overall, I'm impressed.
@ FrankForst - you lost me from the start with that "this gives bloggers a bad name" stuff. That is an outlandish, unreasonable statement. Frank, articles like this are the antidote to bloggers who loudly sprout unsubstantiated stuff. Few articles, no matter how well researched, will be devoid of errors. For a non-peer reviewed research paper, this author has done pretty well. Gizmag is a broad church that hasn't run anything stupid in the time I've been reading it. They're happy to run speculative stuff but you're never in any doubt about that. And I like speculative stuff! Even ideas with little potential to succeed can be critically important to others that will. I actively seek out lively, even heated discussion but your comments are not helpful.
Finally! This is certainly the best article on wind energy this magazine has published so far. It was quite clear that the likes of Anne Ominous would jump up immediately and voice their concerns regarding the accuracy of Betz's limit. Let me tell those, that Betz has it right, at least accurate enough to test new designs against it, and most important: Other than most 'inventors' of 'superior' wind turbines, he fully documented and published the concept and the math! So in case of doubt: Look it up, and do the math yourself. So far, Betz has not been proven wrong in a century, ant that makes his limit a de facto law.
Please Gizmag, follow this article up with one "Betz in a nutshell" article to make it clear to all the Annas out there.
Even though VAWTs are not as effective in generating electricity as HAWTs, research by Caltech suggests that "because VAWTs can be placed closer together, they're capable of generating ten times as much energy per square meter than HAWTs ..." (http://www.ecogeek.org/wind-power/3555-caltech-study-says-vertical-axis-wind-turbines-10x).
What is your comment on this.
The Betz limit relates to an energy extraction system operating in an open air system. Study it closely ... and understand the maths behind what is physically happening, and you'll see why Betz was right.
As a non-injineer (!) but an avid offshore sailer, I'm interested. And there's a worldwide market for small DC power generation devices that reliably recharge the boat's batteries. Long-distance racers are experimenting with fuel cells and hyro-generators, but these are expensive - albeit commercially sponsored - and not yet sufficiently reliable. See the recent Vendee Globe, OSTAR, and Route de Rhum races.
Reliability in a tough environment is now key. The majority of folk with cruising/racing boats fit PV panels in various configurations, self-funded, so there is an income stream for successful manufacturers. I'm part of that potential income stream and waiting for the next 'best product'.
Thanks for a lovely article. I do like the more critical approach to looking at wind turbines but surely this is more of a pled to Gizmag its self to do better reporting? That is if someone is talking about a shrouded design either get the people reviewed to say why this is better than just building longer blades or point it out in the text (surely it's the job of the reporter to do this).
I would like to know which high altitude systems are going for 1-4km long cables? Most to my knowledge claim 800m as the maximum length, could you point me in the direction of the 1-4 km long ones and why you think they are more representative.
Like you, I think some of the important advances are in the unsexy areas of gear boxes, drives, but I'm not convinced that we have the right HAWT as the basis. Most production machines seek to minimise financial risk thats why we tend to go with the best-first technology and begin scaling. Do this often puts the second best technology in dominate position. The QWERTY keyboard is a case in point, its designed to deliberately be slow which was good for old fashioned ribbon type writers but is just a drag for modern electronic keyboards, but its far to late to change. We still have time to get the 'best' device before its too late.
Personally I do think we need some huge innovation in wind turbines, you mentioned some. David MacKay in his book 'with out hot air' points out that it is the inter-turbine spacing which will limit the total amount of energy we can get, We need some radical ideas to fix this. Given the number of people objecting to windfarms in the UK I think we also need artists and architects to work with turbine engineers to build either aesthetically pleasing or more visually acceptable wind turbines.
Look back at the comments Mike - and know you have really well with this excellent article.
Do expect that in the energy field, there you will find all kinds of pitch for investment cash, ranging from the outright fraudulent citing patents that take time to decode sufficiently to figure out they are Cargo Cult science, all the way to plain fantasy. Along the way are some sincerely held beliefs that are just wrong!
We know that the we use the grid energy within microseconds of it being generated, even if it is apparently "owned" for re-sale on the way. If enough is contributed by wind turbines, then even a small change in the wind will give stability problems in providing for the grid. I too am skeptical about "storage" unless it is the sort used to pump water up to a higher altitude lake.
@ FrankForst .. Pointing out in a that there is a limit to how much energy can be extracted from air molecule momentum by slowing down the air flow, using weightless, frictionless, infinitely thin blades (Betz limit) is not words to be diminished simply because they appeared in a "blog".
Apricor, the study you are referring to applies to the increased efficiency of land use for wind turbines, not an increase in the efficiency of the turbines themselves. Lux Wind makes the same argument on their web site. It is valid for large expanses of open land (or water) for wind farms.
oldbilbo, when you are moving, a towed propeller generator works better than wind or solar. Doesn't work at all when at the docks, but unless you have a lot of money for solar panels and a large wind turbine, neither does wind and solar. I had a small wind turbine and just one solar panel and my battery was usually dead when I was docked. And the only things I ran with them were lights and sometimes the radio.
@jeronimo. know the limit well. here are some teaching points for you
-frictionless, infinitely thin blades or actuator disk-idealized prop/airscrew,
-uniform pressure distribution through the system
-prop acts like a brake to airflow, slowing the velocity of the fluid, inducing pressure rise (Bernoulli) on the backface of the disk
-derived from basic momentum theory
-flow field signature follows a bell like shape, flow narrows as it approaches the prop then is diffused, in an irrotational, expanding wake flow
-flow is unperturbed upstream and downstream of the actuator disk nothing acting on the freestream flow or the wake flow, far ahead or far wake
your right-it is an open system, so the limt is challenged on closed systems that perturb the flow upstream and downstream or on machine induce suction, in other words on machines that alter the flow upstream and downstream. the limit can be challenged on any system that perturbs the flow.
I am sorry to see the FloDesign ducted turbine held up as an example of impracticality. This project has serious technical talent behind it and its performance is substantiated by independent wind tunnel testing - at MIT no less. If any ducted turbine makes the big time, it will be this one.
I have the feeling that the three bladed wind turbine is equivalent in some way to the petrol engine. You can keep refining it all you like, but it is still inefficient. I think we need something completely different. I do have such an idea, but I don't know who to discuss it with.
I also have a water operated system.
Call me dumb, stupid or just plain ignorant, but I am one of those who think we are approaching wind in the wrong way.
I am trying to generate power at the perimeter and connect the wing tips to create a linear motor / generator with no gearbox. And, rather than making everything as light as possible using expensive materials and processes, I want to incorporate weight into the design to act as a flywheel and take advantage of any gyroscopic effects for a stable high wind turbine.
The whole system is magnetically levitated at the perimeter and would incorporate the passive Induct rack system as well as variable pitch blades and a weight elevator system in the blade shafts to utilize gravity.
This may seem very complex, but it would eliminate the main shaft, central bearings and the gearbox and the need for lubrication to create a low maintenance, long lasting turbine.
I would also like to incorporate a compressed air storage system in the support structure.
Lastly, how many raptor and bat deaths are too many for all of us to ignore?
Check out harmonicwind.com
I respect many of the opinions on this blog and anxious to get some valuable feedback.
They just finished refurbishing a power dam on the Ottawa river in Ontario a couple of years ago - first time in 80 years - that is what we call real renewable energy. Alternate energy is not equivalent cost energy. If you have to live out in the mountains where there is no grid, you have no choice. Otherwise do the math and the testing to prove your opinions opposing this article first. Also make sure you aren't killing birds or pissing off your neighbours when you test your ideas. In Ontario a Court has stated that neighbours have the right to sue for up to 55% of the value of their land if they believe wind farms have devalued their property.
It's a pity that a straight-forward, factual article that stands as a useful antidote to the BS that often accompanies "breakthrough" wind turbine designs gets faulted by folks with an axe to grind.
For those confused about the Betz limit, please check out: http://en.wikipedia.org/wiki/Betz%27_law for a thorough explanation. This limit is not a reason to cease R&D on wind energy extraction but it merely stands as a precaution against the wind shysters who prey on the ill informed.
As was mentioned above, what really matters is LCOE, or more simply put, kWh/$. An inexpensive system that safely and reliably generates power is a winner. Furthermore, any innovation that reduces manufacturing cost or increases longevity is desirable.
However, the progress that have been made in HAWTs over the last decade is quite remarkable both in reduced cost and in efficiency. If there were economically viable alternatives, project developers would be using them.
@AeroFox - Thanks for the advice on how to improve performance of a Darrieus type turbine, however, this may go against our design protocols. From day one, my mission was to build a turbine that would produce low cost energy, not to be confused with building an efficient turbine.
Using long narrow aluminum extruded blades is one way to guarantee a low cost rotor. Do you think, having a blade with a continuously changing profile will be cost effective? This is one of the reasons HAWT blades are difficult to make.
Our turbine rotor will never win a contest on efficiency, but we do not believe it matters. When we compare turbines of equivalent annual power output, ours usually wins, but the swept area is also much higher. The cost for the larger swept area is not a significant factor because of the inexpensive blades and cables.
The larger rotor increases the equator height but it also decreases the rotational speed which is not an attractive attribute. However, our prototypes use a steel on steel traction drive, which are also low cost and eliminate the need for a high gear ratio gearbox. We do not eliminate the gearbox completely, but we eliminate the low speed, high torque component.
Sorry for the lecture. By the way, the predicted power outputs of the larger turbines are a combination of the work done by the Institute of Aerospace Research, in Canada and from the power outputs of the prototypes. The IAR used computer models, over a two year period, to predict the outputs and life expectancies.
Great article. But small wind chargers such as those used on sailboats was left out. One or more of those on roofs could supply electricity to a house, charge electric cars, etc. If connected to the grid, they could actually make your electric meter run backwards in times of low energy demand and use the juice from the grid in times of high energy demand. It would be an elegant decentralized solution that could free us from the Big Energy companies.
Coanda, originally, and Dyson, recently claim entrainment of up to 15 times as much air! Is anybody working with this?
@LUX. Your machine your design your principles. I like lectures, it's the best way to learn. But a slight disagreement, on changing blade profile-it's more an optimization scheme to adjust to varying wind speeds. No fixed blade can be optimized passively, which is why ACC Is suggested for lower wind speeds. Yes it does add complexity, but honestly, micro dc air pumps are very inexpensive, but do need a thicker foil as housing-which camber as well-is beneficial in lower speed wind regimes. The Caltech research is solid as well as the research you have done. I am sure you are aware of ACC and its benefits. Check out the work done by Georgia Tech on circulation control wing and others. it's fairly mature tech. No doubt your CFD is tight. Best of luck to you and hope to see your machine spinning renewable electrons!!
So, what are the best efficiencies of large commercial HAWTs, compared to 59.3% Betz?
T N Args
I'll believe windpower has arrived when the newspapers include
windspeed (average power-per hour at 200 foot elevation) in
their daily weather reports.
One serious advantage for all wind-power devices: they don't require vast quantities of water for cooling. Theres rarely a lot of water available on a mountain ridge, or a windy plateau.
Although Chicago is known as the windy city, it's unusual to find densely populated, high wind areas.
Useful article. Neglects statistics regarding lightning strikes on existing wind-farms. System safety records (fires, tower collapse, flung blades) aren't promulgated. Generally the VAWTs will be the tallest structures in the local area.
So far the money is extracted from the taxpayers and the utility's customers. The money goes to the bankers, lawyers, venture capitalists, and selected manufacturers. Design life is still unknown.
Caution. Accelerated depreciation, and subsidies vary from state to state, and year to year. So far, most american utilities have had a free ride. They're required to purchase (conforming) wind-power generated electricity, generally at retail rates, but are permitted to pass through the cost to their customers. Even better, they are permitted to charge customers (that want to improve their green image, or that are required to off-set their CO2 footprint) extra.
Aaahhhh wind -- so free, so useless. Even the recent Harvard meta-study demonstrated how poor a power source wind would be if rolled out as boosters would like... http://tinyurl.com/b7uboqe
http://iopscience.iop.org/1748-9326/8/1/015021/ (video read graph axes)
But subsidies from the many to the few do attract!
Problem is that wind's potential of maybe 1-10 Watts per square meter (of co-opted land) is absurd, given the resources consumed. A single, 1.5MW windmill tower contains more steel than a 1GWe nuclear reactor vessel. Throw ina few more windmills and you have the whole plant, delivering power 24/7 at >10kW/sq meter.
Or just install solar panels on exposed building surfaces and, for no land, gain 200Watts/sqm when the sun's out.
The sad reality is that wind has no advantage over geo, hydro or nuclear on lifetime CO2 emissions, and consumes vast amounts of land and mainenance resources, while being unreliably variable and even subject to climate change, as the Chinese have begun to experience...
And, windmills kill...
Our descendents will have one more reason to hate us -- decrepit wind 'farms' all over our nice lands...
Wind -- proving day by day that not all "hot air" is hot.
Dr. A. Cannara
The taxpayer/subsidizer of monopoly utilities is paying for bureaucratic guesswork. That's not a practical way to develop new technology. We will never be able to calculate the cost of such inefficiency. The benefits, little as they may be, are seen. Therefore, this waste will continue until the private sector can no longer subsidize the public.
The solution is to stop govt. meddling in products/services. Centralized control of science is slow death.
Dr. Amory Lovins (Rocky Mountain Institute) has said the energy problems would be all be solved quickly if a level playing field were allowed; if govt. would just get out of the way. That will never happen if govt. power is not diminished by public outcry. We must demand an end to monopolies, i.e., govt. granted special privilege businesses. The govt. tells us monopolies are necessary, but the facts tell us otherwise. No debate is allowed. Monopolies are forced upon us. The initiation of force is never necessary or moral.
Wind energy without energy storage will never be a good way to power the grid because even when the wind is blowing turbulence in the airstream is going to cause spikes and dips in the windmill's output and thus putting the energy into the grid costs a fortune. If all the turbines in a wind farm were generating a store of mechanical energy (compressed air or lifted water) the generated electricity is steady and clean and also on demand not when the wind blows.
@Don.. The most amazing advancements of the past 60 years have been due to government involvement. You think Apple made the iPhone on their own? If you break it down into components and technologies, almost every piece of that thing is a result of government involvement, whether military or civilian research.
And at the other folks who think that wind isn't making money - maybe not, but because fossil fuels are cheap (especially due to fracking) doesn't mean we should continue using them. The world should bite the bullet and discover that the right thing costs more. Produce in the grocery store should cost more to support properly compensated workers, and energy (for cars, electricity, heat, etc..) should cost more as well. We've been growing way too fast on the cheap and the result is suffering - today and tomorrow. People and the environment being treated poorly so someone can get rich quick.
After you have raised all the prices, you have to raise all the wages so people can afford the basic necessities and your right back to where you were before except that nobody expects the money to retain its value, and you have the makings of the Weimar Republic.
wind (and solar) has the serious disadvantage to the grid that it's effectively unpredictable AND inputs come from all over the place.
Current grids are designed aorund large point sources and need massive overbuilding to cope with the new supply model. In addition wind in particular requires significant peaking capacity to back it up (solar profiles are on-average predictable and you can ramp up output of a CCGT systems in a preplanned manner).
With a few exceptions, wind farms are mainly subsidy suckers, making more money from grid operators paying them NOT to connect than from actual power generation.
Unless and until storage systems are developed to match wind systems, they'll remain in the realm of "useful for offgrid connections", but annoyances for major operators.
If the amount of money put into "green renewable resources" had been put into Thorium and Molten Salt Reactor systems they'd be widely deployed by now. As it is, the USA, UK, France, Japan and Russia are stuck using intrinsically dangerous nuclear generation systems, whilst the Chinese are forging ahead with research based on promising systems the USA abandoned 40 years ago because they couldn't produce weapons-grade plutonium - despite their throttleablilty and intrinsic safety (nothing to catch fire, pollute the local waterways if it escaped, or explode due to overpressure/hydrogen and spread hot-n-nasties around, and they don't need to dump heat into local waterways or throttle down on hot days)
Yes, windmills are a nice idea, but unless they're in places of near-constant wind, they're not economic - such places simply aren't that common. If there was some way of matching load with generation then they might be more justifiable but that requires a degree of coordination between producers and consumers that is unlikely to ever occur.
Why are you bring such a hater? If someone wanted to make a con they will invent a perpetual motion machine or some elaborate investment fund scheme, but this people are trying to save the world! I myself am an inventor and I'm working on a wind turbine design to save energy and relieve us from consuming fissil fuels and yet we are reviled, attacked and lambasted in both the engineering and start-up community, whereas texting and image sharing apps are being sold for dozens of billions of dollars!!!!!, it's time to realize that we're trying to create clean energy and save the world...