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Green Building Bible, Fourth Edition
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    • CommentAuthorJoiner
    • CommentTimeSep 5th 2011
     
    It appears on the Action For Renewables website. The username is 'And'...



    To Mike H and the supporters and detractors of the 19th century Wind Turbine structures that are not fit for the Twenty-First Century or, indeed, the Third Millennium.

    Your concerns are coming to a conclusion, because a completely revolutionary Wind Turbine structure has been developed the prototype of which was set in motion on Saturday, September the 18th, 2010.

    The basic structure will produce at least six times the power of the largest Wind Turbine in existence. It suffers from no Amplitude Modulation (or other noise defects) because of the way it works. It will last for a minimum of fifty years (with three to six month maintenance inspections) and takes up a quarter of the land foot print of the existing structures; it is intended for brown field sites. The height of the full scale structure would be no more than one hundred and thirty feet. Most important is the sensitivity of the structure in that it starts to move at a wind speed of less than five miles per hour.

    All this is without the modifications and booster mechanism that will make a very powerful wind turbine beyond anything that can be envisaged at present.

    The aim is to remove the need for fossil fuel power stations altogether.

    The inventor of this structure has stated that with the modifications to the turbine, the amount of power produced would be such that if there were 500 of the modified wind turbines placed on the Atlantic side of Tierra del Fuego (an area that is always windy) at the southern tip of South America and another 500 on the Pacific side there would be enough power generated to cover the electrical power needs of the South American continent.

    So, Mike. H, you may wonder if a certain organization that you have been having dealings with knows about this structure. Well, at a business update meeting held in the May of 2010 it was mentioned to the Founder of the Company and its C. E. O. and both said they were interested. Exactly one year later an e-mail was sent asking if they would be interested in seeing a presentation with a video taken on the above day of the prototype in action. No reply was the result. Consequently, the inventor and I turned up on their open day and one of the managers said that the reason why there was no reply was because they only used “tried and tested technology”; a state of denial maybe?

    I have news for those that imagine such modified “tried and tested” 19th Century technology is somehow the best that can be achieved: It isn’t. Just look at those three bladed structures. When did you ever see such a primitive technology equivalent in any other field of technology? Green they are not. If they were they would be on brown field sites or, better still, placed on decommissioned power station sites; this is a structure that has power station status.

    I haven't covered the economic advantages, but I think you will not need much thought to realize what this must mean in terms of affordable power in the medium to long term.

    A letter of validity from one of the world’s leading authorities on mechanics and aerodynamics was given on viewing the presentation, patents are pending and a consortium is being set up.

    For all those that like their three bladed Wind Turbines, I am sure that there will be good science and technology museums that will take a few of them.

    Finally, it is not for nothing that I mentioned the Third Millennium at the beginning, because, with the use of appropriate materials as specified by the inventor and the necessary regular inspection and maintenance requirements, the structure can last a very long time.

    Yours,

    AND
    • CommentAuthorTimber
    • CommentTimeSep 5th 2011
     
    Snake oil?
    •  
      CommentAuthorJSHarris
    • CommentTimeSep 5th 2011
     
    Has the inventor actually heard of Betz?

    I think not, or else he'd realise that getting 6 times more power from a given size of wind generator wasn't physically possible.

    To be sure, we'd need to know the claimed power and swept area, as then it's easy to see whether the claims are anything close to reality. Why is it that renewables are a breeding ground for wild claims and inventions?
  1.  
    From the reference to low wind speed I think they could be talking about this

    http://en.wikipedia.org/wiki/R%C4%99bielice_Kr%C3%B3lewskie_Wind_Turbine
    •  
      CommentAuthorJSHarris
    • CommentTimeSep 5th 2011
     
    If it is that unit, then it isn't really any different to any other wind turbine in terms of its ability to extract power from a given area of wind. The Wikipedia reference also seems a little awry when it comes to facts.

    quote from Wikipedia: "It has a rotor with 32–33 metres diameter and a total height of 53–54 metres.[1] It delivers 35 kW at a wind speed of 2 m/s and 2000 kW at a wind speed of 14 m/s[citation needed]."

    The theoretical power in the air mass flowing through a 33m diameter disc is:

    Swept area = 16.5² x pi = 855m²

    Power in the wind at 2m/S (ignoring Betz limit) = 0.5 x rho x A x V³ = 0.5 x 1.225 x 855 x 2³ = 4.189kW

    Assuming machine is capable of operating at the Betz limit of 59.3% efficiency, then the mechanical power extracted from the wind to the generator shaft will be:

    4.189kW x 0.593 = 2.484kW

    Assuming a generator efficiency of 90%, then the electrical power delivered by the unit at 2mS wind speed would be:

    2.484 x 0.9 = 2.236kW

    How come they claim 35kW at 2m/S from this machine?

    It's this sort of lying about basic performance that gives renewables a bad name. Quite how we stop these charlatans from trying to extract investment funding that would be better spent on realistic projects I don't know.
    • CommentAuthortiimjp1
    • CommentTimeSep 5th 2011
     
    Surely if it was built in 2003 there are statistics rather that theory, on its output.

    I would have imagined some boffin involved in renewable wind turbine energy would have investigated, wouldnt really be a costly exercise would it?

    Or am i being to simplistic lol
    • CommentAuthorJoiner
    • CommentTimeSep 5th 2011
     
    Hmmm. Well it's obviously something to do with design. :wink: Wonder if it could be along these lines?

    http://cleantechnica.com/2011/09/02/wind-lens-triples-turbine-output/
    •  
      CommentAuthorJSHarris
    • CommentTimeSep 5th 2011
     
    <blockquote><cite>Posted By: tiimjp1</cite>Surely if it was built in 2003 there are statistics rather that theory, on its output.

    I would have imagined some boffin involved in renewable wind turbine energy would have investigated, wouldnt really be a costly exercise would it?

    Or am i being to simplistic lol</blockquote>

    The problem is that few people can seem to be bothered to check up on wild claims, even when they exceed what is physically possible by a large margin.

    The power in any given cross section through the wind is easy to calculate (it's given by P (in watts) = 0.5 x 1.225 x swept area of turbine (in m²) x wind speed (in m/S)³).

    The maximum power that can be extracted from any given section through the wind will be less than the Betz limit of 0.593; allowing for this and the blade and generator efficiency it is unlikely that any wind powered generator can extract more than around 30 to 40% of the available power in the wind.

    One thing this exercise shows is just how flawed Wikipedia can be as a reference source!
  2.  
    Posted By: tiimjp1Surely if it was built in 2003 there are statistics rather that theory, on its output.

    I would have imagined some boffin involved in renewable wind turbine energy would have investigated, wouldnt really be a costly exercise would it?

    Or am i being to simplistic lol


    Totally agree with this. I much rather go on actual output then quote Betz as a reason to doubt the claims. People forget the assumptions made by Betz in his calculations.
    •  
      CommentAuthorJSHarris
    • CommentTimeSep 5th 2011 edited
     
    <blockquote><cite>Posted By: Joiner</cite>Hmmm. Well it's obviously something to do with design.<img title=":wink:" alt=":wink:" src="/forum114/extensions/Vanillacons/smilies/standard/wink.gif"></img>Wonder if it could be along these lines?

    <a rel="nofollow" href="http://cleantechnica.com/2011/09/02/wind-lens-triples-turbine-output/">http://cleantechnica.com/2011/09/02/wind-lens-triples-turbine-output/</a></blockquote>

    This, at least, has a basis in well known facts about blade performance. The convergent duct around the turbine does three beneficial things and one decidedly non-beneficial thing. It increases the effective blade swept area to that of the diameter at the mouth of the duct, rather than the diameter of the turbine blades, so increasing the mass flow of air through the turbine, which in turn increases the potential power that the turbine can deliver. It accelerates the air flow through the duct, so that the turbine blades see a velocity greater than the wind velocity (see Bernoulli's Principle to understand why this happens), allowing it to better utilise low wind speeds. Finally, the duct limits blade span wise flow and hence tip vortices, which are a significant source of blade inefficiency and also a source of noise.

    The downside is that the duct very significantly increases the mast loading in high winds, because it adds substantial drag area. As the drag load from the wind is proportional to the square of wind speed, in very high winds this may pose a significant challenge in terms of the physical strength of the mast and its foundations. This may mean that there is a practical upper limit on the size of such a unit.
    •  
      CommentAuthorJSHarris
    • CommentTimeSep 5th 2011 edited
     
    <blockquote><cite>Posted By: renewablejohn</cite>Totally agree with this. I much rather go on actual output then quote Betz as a reason to doubt the claims. People forget the assumptions made by Betz in his calculations.</blockquote>

    I agree that Betz made some questionable assumptions, however, to misquote from a well known Scots engineer "ye canna beat the laws of physics, captain"

    Even ignoring Betz and assuming there is no limit to power extraction efficiency, there simply isn't enough energy in the mass flow of wind through that size of disc at the quoted wind velocity to get anything like the claimed performance. Unless someone knows of a way to beat the basic laws of physics, the claims are simply not credible, with or without involving Betz.
  3.  
    Posted By: JSHarris
    Posted By: renewablejohnTotally agree with this. I much rather go on actual output then quote Betz as a reason to doubt the claims. People forget the assumptions made by Betz in his calculations.


    I agree that Betz made some questionable assumptions, however, to misquote from a well known Scots engineer "ye canna beat the laws of physics, captain"

    Even ignoring Betz and assuming there is no limit to power extraction efficiency, there simply isn't enough energy in the mass flow of wind through that size of disc at the quoted wind velocity to get anything like the claimed performance. Unless someone knows of a way to beat the basic laws of physics, the claims are simply not credible, with or without involving Betz.




    So where is the physical data to prove or disprove these claims especially as it is one of the oldest turbines in Europe actually dating back to 1932.
    •  
      CommentAuthorJSHarris
    • CommentTimeSep 5th 2011
     
    <blockquote><cite>Posted By: renewablejohn</cite>
    So where is the physical data to prove or disprove these claims especially as it is one of the oldest turbines in Europe actually dating back to 1932.</blockquote>

    Just look at the physics!

    The total power available in any given fluid flow is given by this equation:

    P = 0.5 x rho x A x V³

    Where:

    P = power in watts
    rho = air density in kg/m³
    A = the swept area of the turbine
    V = the wind velocity in m/S

    This equation gives the absolute maximum amount of power that is in any given flow of wind (or any other fluid that incompressible in the particular flow regime being considered).

    The turbine in question has a swept area of 855m² and the claim is that it delivers 35kW at a wind velocity of 2m/S. This is patently rubbish, as the total power in the wind at this speed and over this swept area is only 4.189kW. The claim is that this wind turbine extracts 35kW from a power source of 4.189kW, hence my flippant quote about the laws of physics (in this case the claim is that this machine breaks the first law of thermodynamics, by having an energy output that is many times the energy input).

    I agree, some test data would be useful, if only to give the true conversion efficiency, which I suspect will be down around 20% or less, based on the high drag that a multiple small blade design will give. My WAG is that it would give less than 1kW in 2m/S, rather than the claimed 35kW.
    • CommentAuthortiimjp1
    • CommentTimeSep 5th 2011 edited
     
    Maybe Wikipedia forgot a decimal point it might be simply 3.5kw

    but then again 2000kw @ 14m/s sounds even more unbelievable
    • CommentAuthorJoiner
    • CommentTimeSep 5th 2011
     
    And to save anyone else having to follow up... http://en.wikipedia.org/wiki/Betz%27_law

    And to quote a well-known ship's captain: "Beam me up, Scottie." :shocked:
    •  
      CommentAuthorJSHarris
    • CommentTimeSep 5th 2011 edited
     
    Just looking at the power in the wind, and ignoring the efficiency with which any wind turbine can extract it as useful electrical (or mechanical) power, then we can calculate the swept area needed to get the quoted performance for the two wind speeds given in that wikipedia reference.

    For the 2m/S case, delivering 35kW at 100% efficiency:

    rearranging the power equation to determine area gives:

    A = P/(0.5 x rho x V³)

    rho = 1.225 kg/m³
    V = 2m/S
    P = 35,000W

    therefore A = 7143m² and the turbine theoretical swept diameter is 2 x sq rt(A/pi) = 95.4m

    Now let's look at the 14m/S case, delivering 2000kW:

    The turbine theoretical swept area for 100% efficiency would be 1190m² and the turbine theoretical swept diameter is 38.9m


    If efficiency was 50% then the actual turbine area for the 2m/S case would be 14,286m² and the diameter 134.8m and for the 14m/S case the turbine area would be 2380m² and the diameter 55m.

    One conclusion from the above is that the quoted performance figures don't really stack up for a single turbine of any size, which leads me to suspect they were plucked from thin air.
    • CommentAuthortiimjp1
    • CommentTimeSep 5th 2011
     
    or very powerful "THICK AIR" me thinks
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 5th 2011 edited
     
    Is it a case of getting kW and kWh mixed up, I am not going to check any of it out as its rubbish.
    You can make a large turbine that can extract useful energy at low wind speeds, it will also work at high wind speeds, just that efficiency drops, in certain situation this may produce more kWh (basically low windspeed places, but not built up ones) than one that has a higher cut in speed. It is why a wind survey is always done for large turbines. The turbine is matched to the windspeed distribution at that site, it is not a case of using averages (though the distribution can be modelled using the mean and a 'correction factor').
    Too many people think that RE stuff has some hidden gems, it don't, it just uses the laws of physics, just as FF stuff does.

    As for Betz's assumption, this will increase the efficiency not decrease it.
    Almost every year in my old Science Department, someone would come along with a perpetual motion machine, usually involving water, but sometimes magnets, they were usually showed the Laws of Thermodynamics and they did not come back.
    There is also a mindset amongst RE students (and the RE industry) that a MWh generated by renewables is a MWh saved from burning fossil fuel. Wish it was true, but with the UK's incredibly reliable and consistent electrical grid there is always a need for backup and balancing. RE generation alone cannot guarantee this for the foreseeable future, hence we will be burning coal and gas for a long time, hopefully with CCS.
    I was reading on the weekend about CCS and seems that one of the drawback of it being acceptable, other than where to store the CO2, is the higher energy needed to capture the CO2, this translating to a 25-30% cost. The analysis seemed to think that this wholesale cost would translate to a 10% retail cost for domestic users. So less than 5 of the large 6 producers/distributors has already put prices up by. Seems cheap technology to me.

    Look at this site about scams:
    http://www.nlcpr.com/vertmill.php
    •  
      CommentAuthorJSHarris
    • CommentTimeSep 5th 2011
     
    It could be just sloppy reporting in wikipedia, with kWh per 24 hour period for a given mean wind speed being quoted, although the efficiency (ignoring Betz) is still a bit high.

    35kwh gives about 1.46kW per hour over 24 hours (for the 2m/S mean wind velocity case), which equates to a system efficiency of about 35%, which is perhaps possible for a reasonably good wind turbine, but higher than I would have thought for this design, with it's inherently high drag losses.
    • CommentAuthorJeff B
    • CommentTimeSep 5th 2011
     
    Joiner - rather than initiate a 5-pager "speculation" thread on this, why not simply go onto the Renewables forum in question and ask "And"?
    • CommentAuthorJoiner
    • CommentTimeSep 6th 2011
     
    Oh, I don't know Jeff. It's provided some interesting diversion for a few people and also informed the rest of us of the truth of that old adage, that what appears to be too good to be true, probably is too good to be true!

    Although you do find that the older you get the truer it seems that good old Will S got it about right:

    Horatio: O day and night, but this is wondrous strange!

    Hamlet: And therefore as a stranger give it welcome.
    There are more things in heaven and earth, Horatio,
    Than are dreamt of in your philosophy.

    Funny thing about this forum is that at first it's tempting to have a go at the clever buggers who reduce everything to numbers, but it doesn't take long to realise that a) they do it to explain a complex world, b) in time it all seems to start making sense and if it doesn't, those areas you're having a problem with are happily explained without condescension, c) contrary views are hammered out between the opposing views leaving you informed enough to make a choice between them and come to your own conclusion, not that of the author of the article making the claims you're not quite sure about.

    So, you start a thread not really knowing where it's going to go; it may even end up as a 5-pager "speculation", although this one has quite a way to go to get there. :wink:
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 6th 2011
     
    5 pages of numbers, easy :cool:
    • CommentAuthorJoiner
    • CommentTimeSep 6th 2011
     
    :bigsmile: Stirrer.
  4.  
    OK if you like numbers then please explain why this involute shaped wind turbine gets better results then predicted by Betz.

    http://www.fundamentalform.com/html/wind_power_analysis.html

    Normally I treat such designs with a pinch of salt but this guy is a respected biomass furnace engineer producing some of the most efficient furnaces in the world.(Even Brian would be pleased with the ultra low emissions)
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 6th 2011 edited
     
    Had a quick look, and just guessing a bit before I can have a proper look.
    Do the vanes that direct the air increase the catchment area? So what is claimed to be a turbine diameter isn't?
    Not really got time to look in detail at the moment, but funnels, venturi, odd shaped blades and the like have all been tried before and we end up with a 3 blade design.
    •  
      CommentAuthorJSHarris
    • CommentTimeSep 6th 2011 edited
     
    It may well work like a convergent duct, as I mentioned earlier in this thread, so I think you are possibly right, ST. If so, then the effective swept area is significantly greater than the actual swept area, allowing greater energy capture.

    There are several ways in which the performance of any wind driven system can be increased to exceed the (somewhat questionable) limit proposed by Betz. Even simple things, like positioning arrays of conventional turbines on ground that is profiled so as to accelerate the velocity at the blade swept area will give enhanced performance over that predicted from measuring wind velocity at a fixed height and calculating the gradient, as would normally be done.

    Some of the stuff in that paper is very questionable in terms of basic physics, but nevertheless there may be merit in some of it. For example, the author clearly doesn't quite grasp why spanwise flow on blades causes losses, and makes a comment about the blades "flinging the wind outward".

    The truth is that it is at the blade tips where the major losses occur, as the flow from the high and low pressure sides of the blade, flowing somewhat radially along the blade span, mixes at the tip and produces tip vortices. These vortices are highly energetic, so, because of the first law of thermodynamics, remove energy that might otherwise be captured and used. They are also the primary source of noise from blade airflow.

    Reducing tip vortices can be achieved by using long, thin, high aspect ratio blades, adding tip winglets, or using a duct as previously mentioned.

    Edited to add:

    Having now read the whole of that chaps writings on his conical VAWT, I have to say that there is very little evidence that it performs as well as a similar sized axial wind turbine, let alone exceeds it. There doesn't seem to be anything in the way of hard evidence, or even some basic performance predictions using known data. The chap seems to be a keen amateur experimenter (and all credit to him for that) but without either hard data or a validated performance model I'd have to say that I doubt many of his apparent claims.

    The big wind turbine manufacturers have done a lot of R&D and now produce machines that are pretty effient, although they are encumbered by the need to be on rotating masts to some extent. If any VAWT design came close to an axial design you can be sure that it would have been picked up commercially, as VAWTs have a number of practical advantages when it comes to installation and maintenance. Unfortunately all VAWTs are inherently less efficient than axial flow turbines, by enough of a margin to overcome the practical advantages they can offer.
    • CommentAuthorJeff B
    • CommentTimeSep 6th 2011
     
    <blockquote><cite>Posted By: Joiner</cite>Oh, I don't know Jeff. It's provided some interesting diversion for a few people and also informed the rest of us of the truth of that old adage, that what appears to be too good to be true, probably is too good to be true!

    Although you do find that the older you get the truer it seems that good old Will S got it about right:

    Horatio: O day and night, but this is wondrous strange!

    Hamlet: And therefore as a stranger give it welcome.
    There are more things in heaven and earth, Horatio,
    Than are dreamt of in your philosophy.

    Funny thing about this forum is that at first it's tempting to have a go at the clever buggers who reduce everything to numbers, but it doesn't take long to realise that a) they do it to explain a complex world, b) in time it all seems to start making sense and if it doesn't, those areas you're having a problem with are happily explained without condescension, c) contrary views are hammered out between the opposing views leaving you informed enough to make a choice between them and come to your own conclusion, not that of the author of the article making the claims you're not quite sure about.

    So, you start a thread not really knowing where it's going to go; it may even end up as a 5-pager "speculation", although this one has quite a way to go to get there.<img title=":wink:" alt=":wink:" src="/newforum/extensions/Vanillacons/smilies/standard/wink.gif"></img></blockquote>

    Joiner - I know what you are saying. My response was not a personal dig - it just seemed to me to be the simplest solution! Clearly my prediction of a "5-pager" is somewhat wide of the mark, at least as yet. I guess my rather flippant comment was based solely on the fact that I haven't the faintest idea about wind turbine design and all this Betz's stuff, so I can't contribute anything even remotely interesting on this subject!

    Jeff
    • CommentAuthorJoiner
    • CommentTimeSep 6th 2011
     
    Actually, Jeff, just by being a member of the "audience" you're contributing to the performance. As a result of that passive role I now know a damn sight more about turbines than I knew when I read that link. :wink: :bigsmile:
    • CommentAuthorGavin_A
    • CommentTimeSep 6th 2011
     
    This very much is beyond my ken, but I was having a related discussion with someone who knows about such stuff in vast amounts of detail, about a prototype turbine for use in a certain location for a certain function* that made no sense to me based on my more basic understanding of how wind turbines function (stuff like betz etc. )

    As I say, I had to give up in the end because my head was imploding trying to work it out, but the general concept seemed to be related to the careful use of vortexes, low and high pressure zones to do something clever to multiply the power available, but I really didn't understand it tbh as I think I mentioned earlier.

    It won't be this product though as this was a small scale design for a specific location, but could be a related concept.




    *IIRC a non disclosure agreement is in place, so I probably shouldn't actually say anything at all, but being as this post is clear as mud anyway...
    •  
      CommentAuthorJSHarris
    • CommentTimeSep 7th 2011 edited
     
    I always find it helps to go back to basics and start with working out how much potential energy is available from the source, be it wind, solar or whatever. Knowing that, this then sets an upper limit on the amount of power that any device can extract. If people are claiming that their device can extract more energy than is available from the source then they are wrong, plain and simple, unless they have found a way to beat the First Law of Thermodynamics (which states that energy cannot be created or destroyed, only converted from one form to another).

    There are ways to improve the efficiency of wind powered devices, some practical, some less so. Betz worked out that you could never extract all the energy from the wind, as to do so would mean that the wind velocity downstream of the turbine would be zero. Zero velocity downstream implies no air movement which implies no movement of the wind turbine either.

    There are some disputed assumptions behind the Betz Limit, but in essence his limit of 59.3% of the available energy being the most that could be extracted is probably close to reality for pretty much all practical devices. Over and above the Betz restriction, there are other inefficiencies in any wind turbine. All wind turbines have a certain amount of drag, both aerodynamic and frictional, which will reduce efficiency. Electrical generators and power conversion/transmission systems also have losses, so further reducing efficiency. At the moment, getting a peak of more than about 40% of the available power in the wind from any wind generator is considered to be pretty good, although most wind generators have a marked variation in efficiency with wind velocity and so will have an average efficiency that is considerably lower than this.
   
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