# The New "Freedom Tower" Design: Mechanics And Renewable Energy?

In the local paper this morning, the Pittsburgh Post-Gazette, the lead picture and headline shows the artist’s rendition of the latest replacement for the World Trade Center, the Freedom Tower. In the caption it mentions that the first 70 floors would be habitable, and then the rest of the height of the tower would consist of cables and windmills, topping off with an antenna to be the world’s tallest building.

Immediately I thought, “Windmills? How odd.”

Then my second thought was, “Windmills, eh? What a wonderful idea.” This seems to be a successful marriage of mechanics and alternate power sources, assuming that the windmills would be there to provide some power to the massive structure. The idea seems obvious now, since there is more wind at higher altitudes.

Driving down desolate sections of highway, I am always pleased to see a lighted highway sign (keep reading) that is powered by solar panels on top of it. I’m pleased that the manufacturer desiged these signs with an alternate energy source in mind, but in the back of my head I always know that this idea was born out of cost savings and laziness. Otherwise, they would have to spend the money to run a power cable for miles just to light that sign, or pay some poor guy to drive out there daily and refill the gas generator.

So, my questions are:

Does anyone know if these windmills in this proposed Freedom Tower are designed to actually provide power to the structure?

How much power does a “normal” windmill provide? And is this power relatively reliable?

Is there an equation that says, basically, “A windmill with X amount of wingspan will power X amount of office floors?”

Are there any buildings that exist today that use this idea of renewable energy?

It is estimated that the Freedom Tower windmills will provide about 10-20% of the building’s power. I dunno how to calculate how much energy a windmill produces; obviously it depends on the wind conditions at the time.

I don’t think there are any solar-powered street lights. The solar cells you see near some of them are just for detecting when it becomes dark.

According to this NewsDay article,

Necessity may be the mother of invention, but cost savings and laziness are its doting uncles.

Check out the Buffalo Mountain Windmill Power Calculator.

I would think the results would be close as the calculator takes into account humidity (NY being more “tropical”).

I ponder the cost effectiveness of the whole situation. A minor amount of a windmills will cause a higher per unit repair and operating cost. This isn’t exactly a windmill farm they are putting up.

The symbolic importance of showing dedication to a renewable resource for our energy needs may outweigh project-specific cost analysis. The building will mean much more than simple restored office space.

Can’t they just make all the windows, say the top 30 floors, all solar panels?

Chicago Faucet: Cost-saving and laziness are the two biggest drivers of peacetime technological advances. To a lesser extent they drive wartime technology, but the factor of not getting our asses whooped steps into a prime role.

Remember: The wheel was invented by people who got damned tired of dragging sledges around, and writing was designed by people too lazy to remember everything.

Since solar panels are opaque, they aren’t very suitable for windows.

Excellent link Vezer, although I had to switch my brain to metric. I estimated an average robust speed of 15 meters per second at that altitude (about 34 miles per hour), at 5 degrees Celsius (pretty cold: 41 degrees Fahrenheit), and 50 percent humidity (we would be getting close to the clouds at that height).

The results were that three turbines in a year would produce 15.41 million kilowatt hours. That seems lot a whole lot, but I’m not going to run and find my latest power bill to compare it.

The weird thing is that this calculator automatically assumed a height of 3500 feet. Way too high. Actually, almost exactly twice as high as the tower would stand. So I don’t know why that height was assumed, or how much it skews the results. Nor does it state how big the turbines would be.

Then again, they mention “turbines,” not, “windmills.” Unless this is a simple difference in terminology (how does one convert a turbine to a windmill? What is a metric windmill?), how would we know what the difference is?

I’m glad you found my page interesting and/or useful. I guess maybe it’s
not clear enough that the calculator is customized to the actual elevation
of TVA’s power plant location on Buffalo Mountain in Tennessee (and the 3
particular Vestas model V47-660 kW turbines/windmills). 3500 feet is the
approximate actual elevation at the rotor, which is at the top of the
tower, about 200 feet above ground. These turbines have blades (3 each)
that are about 75 feet long.

I think “windmill” is used to invoke farm-like imagery, and “turbine” is
used to sound more modern and high tech. The only reason for using metric
units is that’s what the reference information came with (from Denmark):

http://www.mensetmanus.net/windpower/calcbasis.shtml

TVA would be ecstatic to produce that much in a year. They were hoping for
about 6 million kilowatt hours, lowered the goal to 4.6, and have
actually done less than 4.

Regards,

Bob

There are such things; I have no idea how good they are.

Isn’t it the case that a structure bearing windmills will have to be engineered to withstand greater wind shear forces (as the windmills are acting as sail surfaces, rather than the building being designed to let the wind slip past as easily as possible)?