The manufacturing is quite clever with the PCB integrated generators (commonly done for low cost motors) and the moulded plastic parts. It would have been interesting to experiment with a PCB inductions generator rather than the permanent magnets. Building these in volumes would be cheap and easy, it may well be a real innovation if you can add cheap wind generation capacity to the growing home DC infrastructure.
The manufacturing is quite clever with the PCB integrated generators (commonly done for low cost motors) and the moulded plastic parts. It would have been interesting to experiment with a PCB inductions generator rather than the permanent magnets. Building these in volumes would be cheap and easy, it may well be a real innovation if you can add cheap wind generation capacity to the growing home DC infrastructure.
Again, 8 meter diameter, 270W average power (and that is as stated by them, with no number whatsoever to substantiate it..)
They don't even say what is power rating per individual microgenerator.. Not to mention, the tree will see only turbulence, even in good laminar wind, because of turbine interaction...
That is an art installation. I even like it as such, nice symbolism etc.. But as serious power generation device it's a joke..
From brochure :
"Producing an average of 2400 kWh annually, depending upon its loca-on"
That is average power of 277.7 W for a tree of 8 meter diameter...
From brochure :
"Producing an average of 2400 kWh annually, depending upon its loca-on"
That is average power of 277.7 W for a tree of 8 meter diameter...The numbers are all there, lets pull them out.
Installed capacity of 1 "tree" unit of turbines, 4100W
Around 60 "leaves" (turbines) on the pictured tree, ?70W each
Estimate of 2400kWh annually, which is a annual load factor of 13%
which is all very believable for such a system.
Yes, wind is a scarce resource in the urban jungle but you could put these in more favourable locations. But lets return to convenient rooftop installation:
http://web.wpi.edu/Pubs/E-project/Available/E-project-050410-163916/unrestricted/mc_rd_an_js_Rooftop_Wind_IQP_Report.pdf
Suggesting a 5% typical load factor in a urban environment.
5% annual load factor on 70W is 15kWh/year
My off the cuff estimate of a buy price @ $50 per leaf seems right on the mark if you can use them in better than average locations.
Some of us are about engineering and supporting good ideas, rather than rubbishing them without actually looking at the figures.
Funny numbers:
6. First they say solution scales from 500W to 3 kW, than tree has 4.1kW. Which is it?
7. Estimate of 2400kWh per annum correlates with a single, high efficiency (40% something) high speed vertical turbine with 8m diameter with good airfoil running at 10m/sec wind. They cannot achieve that efficiency, period, and 10m/sec is a speed that borders with a very bad weather with storm warning (that is between 5 and 6 on Beaufort scale).. No such wind in cities, except in gusts at storm time..
8. Their generator they are so proud of, is not very good exactly because of use of a PCB winding.. Classic winding has much better packing factor .. And voltage generated will be very low, few volts at best with huge currents, when you're lucky it actually generates something..
9. 2 m/sec is funny too.. at that speed I see those kid rotating toys spinning too.. But they are not creating energy, just overpowering friction... Wind energy is proportional to wind speed to third power, so if you have say, 125W turbine rated at 10m/sec, at 2m/sec that 5*5*5 less that 125.. Wait, that is whole 1 Watt!! ....... That is the reason no respectable vendor even bother with anything below 4-5 m/sec..
There is no energy to be had at that speed, so they optimize for better efficiency at higher speeds...
6 ) they didnt explain the lower end of the scaling, but as with grid connected solar you have some lower point where the economics dont work. You can buy solar panels of a few watts, residential solar installs are typically built with 200W panels, but they dont offer 200W systems for sale.
7 ) the 13% annualised load factor they imply is believable with good siting, I even think it'll pay in less ideal conditions. Its not assuming a wildly efficient system with the full swept area but something realistic like:
Lets pull some well known and relaiable numbers from "Sustainable Energy – without the hot air" for 6m/s wind (the average daily wind speed where I live) they estimate 140W/m2 available power and we can guess a typical efficiency of the cheaply made turbine to be say 25%. So with several square m of swept area the claim of the installed capacity being 4100W is believable and would only need a peak wind speed of 60km/h (believable). Oh look at 6m/s steady, that comes up with 1200kWh annual, contradicting your claims it needs all of more area, higher efficiency, and higher wind speeds than believable all at the same time to achieve the numbers. Back with "Sustainable Energy – without the hot air" they come up with an optimistic 600kWh annually for 1m2 of swept volume, so the 2400kWh annual for a tree install seems right on the money.
8 ) the PCB design is about cost reduction, this is the clever part. They're reportedly delivering systems for $500/leaf as art installations, so the guess of $50 in volume production I'm suggesting is again believable.
9 ) you on one hand dismiss that they havent shown and power profiles and then poke fun at the data they do provide, we've now got the cut in point for the profile, of course it produces very little power as does the cut in point of all wind generators.
The numbers are all within believable ranges, once they produce/share some more technical details it will be interesting but there is nothing here that is wildly difficult or impossible to achieve. The big innovation is building it cheaply in volume.
7 ) the 13% annualised load factor they imply is believable with good siting, I even think it'll pay in less ideal conditions. Its not assuming a wildly efficient system with the full swept area but something realistic like:
Lets pull some well known and relaiable numbers from "Sustainable Energy – without the hot air" for 6m/s wind (the average daily wind speed where I live) they estimate 140W/m2 available power and we can guess a typical efficiency of the cheaply made turbine to be say 25%. So with several square m of swept area the claim of the installed capacity being 4100W is believable and would only need a peak wind speed of 60km/h (believable). Oh look at 6m/s steady, that comes up with 1200kWh annual, contradicting your claims it needs all of more area, higher efficiency, and higher wind speeds than believable all at the same time to achieve the numbers. Back with "Sustainable Energy – without the hot air" they come up with an optimistic 600kWh annually for 1m2 of swept volume, so the 2400kWh annual for a tree install seems right on the money.
Funny that.. from that same place "Sustainable Energy – without the hot air" , a quote :
"...Chapter B (p263) explains how to estimate the power per unit area of a
wind farm in the UK. If the typical windspeed is 6 m/s (13 miles per hour,
or 22 km/h), the power per unit area of wind farm is about 2 W/m2...""
that exactly correlates with my numbers and your 140W is a bit high...
7 ) the 13% annualised load factor they imply is believable with good siting, I even think it'll pay in less ideal conditions. Its not assuming a wildly efficient system with the full swept area but something realistic like:
Lets pull some well known and relaiable numbers from "Sustainable Energy – without the hot air" for 6m/s wind (the average daily wind speed where I live) they estimate 140W/m2 available power and we can guess a typical efficiency of the cheaply made turbine to be say 25%. So with several square m of swept area the claim of the installed capacity being 4100W is believable and would only need a peak wind speed of 60km/h (believable). Oh look at 6m/s steady, that comes up with 1200kWh annual, contradicting your claims it needs all of more area, higher efficiency, and higher wind speeds than believable all at the same time to achieve the numbers. Back with "Sustainable Energy – without the hot air" they come up with an optimistic 600kWh annually for 1m2 of swept volume, so the 2400kWh annual for a tree install seems right on the money.
Funny that.. from that same place "Sustainable Energy – without the hot air" , a quote :
"...Chapter B (p263) explains how to estimate the power per unit area of a
wind farm in the UK. If the typical windspeed is 6 m/s (13 miles per hour,
or 22 km/h), the power per unit area of wind farm is about 2 W/m2...""
that exactly correlates with my numbers and your 140W is a bit high...2W/m2 of land area, right now you're the one with the figures out by an order of magnitude or more. Do you want to have your debunking stamped with a "FAIL" ?
Aeroleaf looks plausible and more data will be interesting.
I apologize for that omission.. You are correct in that that I quoted wrong... But your 140W is also very wrong.. That is theoretical power of wind at 6m/sec.
Betz's law say you cannot extract, ever, more than 59% of that energy.. In real life for best of vertical, large high speed turbines is a bit over 40%..
Savonius vertical rotor (this is a variant) is usually 20-30%. So we are talking about 25-45W.. 3 to 5 times less than you stated...
we can guess a typical efficiency of the cheaply made turbine to be say 25%. So with several square m of swept area
In addition to that you can't dispute other 100 sentences I wrote
And I really dislike people losing energy in trying to discredit something or somebody based on hate, prejudice and such..
They don't even say what is power rating per individual microgenerator.
They don't even say what is power rating per individual microgenerator.
They do, and even have a graph.
I have not run the numbers yet, but my guess is that unless you have say >10-12kmh wind for a good lot of the day, these things aren't going to cut the mustard for bang-per-buck.
Actually, I guess that regardless of wind speed these thing won't offer viable bang-per-buck for anything but arty type installations, or other dense urban installs.
But then, why not integrate this into a whirlybird for your roof and get roof cooling and generation into one. There is probably a reason hasn't caught on.
Quote from: EEVblog on Today at 10:05:53 PM
Quote from: 2N3055 on Yesterday at 07:10:24 PM
They don't even say what is power rating per individual microgenerator.
They do, and even have a graph.Quote
I have not run the numbers yet, but my guess is that unless you have say >10-12kmh wind for a good lot of the day, these things aren't going to cut the mustard for bang-per-buck.
Actually, I guess that regardless of wind speed these thing won't offer viable bang-per-buck for anything but arty type installations, or other dense urban installs.
But then, why not integrate this into a whirlybird for your roof and get roof cooling and generation into one. There is probably a reason hasn't caught on.
Thank you for that.. I didn't look hard enough I guess... So pretty much not useful as power generation.. If considered energy harwesting, I might even use it for some telemetry low power thing if they will sell it for a good price..
I have not run the numbers yet, but my guess is that unless you have say >10-12kmh wind for a good lot of the day, these things aren't going to cut the mustard for bang-per-buck.
Actually, I guess that regardless of wind speed these thing won't offer viable bang-per-buck for anything but arty type installations, or other dense urban installs.
But then, why not integrate this into a whirlybird for your roof and get roof cooling and generation into one. There is probably a reason hasn't caught on.
I too saw these on Facebook and my first question was can I buy them individually and how much power do they produce. I think I did work out the 70 watt figure based on the figures they did give on their website but their website is more of a flashy advertisement than giving any technical detail. I too don't see these as being any more useful than an art installation unless you can buy the individual leafs quite cheaply as they could be quite easy to install for hobbyists.