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.
Respectfully there are no relevant numbers in their brochure just some highly optimistic speculations.. Which is endemic for most wind energy industry, save for few respectable vendors..
So all you can is speculate and it has same significance as my laughing at them...
Missing numbers?
1. Size of the individual microturbine ?
2. Rotor efficiency ?
3. Generator efficiency, voltage and rated power at specific wind speed?
4. Wind speed to power graph ?
All of that would be in fantastically perfect laminar flow.. so:
5. Study of turbine interference and loss of efficiency because of that.. If they claim they have a solution for turbulence problem, then comparison study how much they improved standard solution.
And yes, testing of that across whole wind speed range.
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...
Also in the study you linked in summary criteria is listed as:
"..
The criteria we developed suggest that a potential building should be:
42
Above 150 feet tall (that is a 18-20 story building)
Have a roof at least 5,000 square feet
Supported by columns which the turbine can be attached to
Taller than buildings upwind
Not in a historic district
Not in or near an avian habitat
Connected to either a spot or radial network
Preferably commercial, waterfront, or industrial area
.."
That pretty much mean cca 10 locations in a city that I live...
And if I had more time, I could go on more but I guess it will suffice to explain what I had go trough my mind when I saw it.. So based on that, I agree with Dave, and I call bullshit on this one..
This is one of those things that look and sound cool, it seems to have potential, but in reality, that money would be better spent on proven green technologies that we know that work.
With the hard data numbers that can prove it..
I'm not saying it will explode and will create no electricity at all, but I highly doubt it can generate promised specs...
If you have access to more numbers, I would like to see them and then we can calculate..
I really like idea of green energy and support it..
It's just I don't like con man and graphics designers posing as electrical engineers to pretend something works because it looks cool...
And as I already said, it does look very cool !!
Best regards!