Solar updraft tower - PeachParts Mercedes-Benz Forum

Mister Byrnzoil · #1 09-10-2008, 01:42 PM

I'm intrigued by this idea...

http://en.wikipedia.org/wiki/Solar_updraft_tower

A German company actually built one in the 80's in Spain thats 200m tall...

http://www.sbp.de/en/html/solar/aufwindkraftwerk.html

Anyway, I'm designing a desert home and I'm trying to incorporate one that is made out of 55 gallon oil drums that would be about 45 to 50 feet tall w/ a 40' x 10' collector.

Anyone with the brains to figger out the practical possibilities of such a system mathematically is invited to comment.. please show your work

the diameter of a 55 gallon drum is 23"

I'm still working on the specifics of the collector, but it would receive both direct sunlight and reflected light from the bldg in an attempt to increase the heat.

kknudson · #2 09-10-2008, 06:09 PM

I've had the same idea,

I would use brick painted black / dark to create the chimmney, holds heat better.

Also considered mirrors around it to reflect more heat

Botnst · #3 09-10-2008, 06:14 PM

Quote:

Originally Posted by Mister Byrnzoil

I'm intrigued by this idea...

http://en.wikipedia.org/wiki/Solar_updraft_tower

A German company actually built one in the 80's in Spain thats 200m tall...

http://www.sbp.de/en/html/solar/aufwindkraftwerk.html

Anyway, I'm designing a desert home and I'm trying to incorporate one that is made out of 55 gallon oil drums that would be about 45 to 50 feet tall w/ a 40' x 10' collector.

Anyone with the brains to figger out the practical possibilities of such a system mathematically is invited to comment.. please show your work

the diameter of a 55 gallon drum is 23"

I'm still working on the specifics of the collector, but it would receive both direct sunlight and reflected light from the bldg in an attempt to increase the heat.

Might be a good idea to think about the weight of each barrel. And the --- what, Young's Modulus? I forget. Anyway, under what weight will the bottom barrel deform.

Then think about wind.

Walgamuth is an architect. Bet he can steer you right.

B

Mister Byrnzoil · #4 09-10-2008, 08:12 PM

Thanks Bot, I have considered the wind, but hadn't considered the weight..

a drum weighs about 40 lbs and I'd need 17 of them. The stack will not be free standing, and I believe that sufficient reinforcement could be added to the bottom barrel(s).

Medmech · #5 09-10-2008, 08:17 PM

Check this out.

http://www.youtube.com/watch?v=1dTt2s6YwJ8

Botnst · #6 09-10-2008, 08:21 PM

Quote:

Originally Posted by Mister Byrnzoil

Thanks Bot, I have considered the wind, but hadn't considered the weight..

a drum weighs about 40 lbs and I'd need 17 of them. The stack will not be free standing, and I believe that sufficient reinforcement could be added to the bottom barrel(s).

Back in ancient times I took a calculus course in which we had to demonstrate that weight-for-weight, a cylinder is stronger than a solid column. I (mercifully) have forgotten the intricacies but I'll bet an engineer somewhere has provided, on the Internet, a method for determining the deformation of a barrel under stress in 1 direction.

The reason I mention wind is that I can imagine that a combination of lateral thrust and gravity is pretty serious. I'm guessing a function to the 3rd or 4th power. Is there an M.E. in the house?

Mister Byrnzoil · #7 09-10-2008, 08:22 PM

Quote:

Originally Posted by kknudson

I've had the same idea,

I would use brick painted black / dark to create the chimney, holds heat better.

Also considered mirrors around it to reflect more heat

Definitely BLACK!

I also considered a secondary stack behind the main stack made of barrels split lengthwise with the inside painted silver and making a vertical reflective 'cradle' (for lack of a better term) so that the main stack gets max heat.

Anyway, I hope TW chimes in.

TMAllison · #8 09-10-2008, 09:14 PM

680lbs is very little weight. I've seen 3000lb pallets stacked on top of an empty drum. Pretty sure they stack full drums at least 6 high.

A T collar or other way to support the welded connections and keep them perfectly plumb would be very important; as would cables or attaching to your structure. Might want some sort of barrier around the base so someone couldn't accidently dent the bottom couple of barrels.

So the Jones are going to 4 stories now?

Larry Delor · #9 09-10-2008, 10:50 PM

Would it help any to have the bottom of the barrel flared (like an upside down velocity stack) ? Wouldn't you want the entire stack to be smooth inside?

Botnst · #10 09-10-2008, 11:16 PM

Quote:

Originally Posted by Larry Delor

Would it help any to have the bottom of the barrel flared (like an upside down velocity stack) ? Wouldn't you want the entire stack to be smooth inside?

Bet that depends on the velocity of the draft. If lits low velocity then turbulence is less important. If it's high velocity then you have all of those issues with laminar flow and viscosity.

Larry Delor · #11 09-10-2008, 11:30 PM

Makes sense.

Well....I'd be curious to hear what the average velocity is, and if there might be any benefit from having a 90 degree elbow at the top, to take advantage of any wind, and the suction it could create.

mpolli · #12 09-10-2008, 11:57 PM

The point of those is to drive turbines to generate electricity. Is that what you are going to do? I think you would need more height. Sorry no math for you. The idea is the same as a dam except upside down. So bigger drop/rise = more energy. And in this case the hotter the air at the bottom the better (obviously). I think that is why in the drawing they show large heat collectors at the base. The tower itself is not the collector.

Botnst · #13 09-11-2008, 07:23 AM

Quote:

Originally Posted by mpolli

The point of those is to drive turbines to generate electricity. Is that what you are going to do? I think you would need more height. Sorry no math for you. The idea is the same as a dam except upside down. So bigger drop/rise = more energy. And in this case the hotter the air at the bottom the better (obviously). I think that is why in the drawing they show large heat collectors at the base. The tower itself is not the collector.

Makes sense.

Mister Byrnzoil · #14 09-11-2008, 09:52 AM

Quote:

Originally Posted by TMAllison

680lbs is very little weight. I've seen 3000lb pallets stacked on top of an empty drum. Pretty sure they stack full drums at least 6 high.

A T collar or other way to support the welded connections and keep them perfectly plumb would be very important; as would cables or attaching to your structure. Might want some sort of barrier around the base so someone couldn't accidently dent the bottom couple of barrels.

So the Jones are going to 4 stories now?

I am a welder, I have built some large steel structures, Plumb is my middle name. I can build anything and make it strong enough to withstand 80mph winds, (Palm Springs CA area bldg code) Anyway, the Joneses are going as high as they can.

My issue is the height and diameter of the stack versus the velocity of the airflow in relation to the collector and turbine... Perhaps I should be using 35 gallon drums with a diameter of 14" to decrease air mass and increase velocity... but I'm not smart enough to apply whatever field of mathematics this entails to the problem at hand.

Mister Byrnzoil · #15 09-11-2008, 10:06 AM

Quote:

Originally Posted by mpolli

The point of those is to drive turbines to generate electricity. Is that what you are going to do?

Thats it precisely

Quote:

Originally Posted by mpolli

I think you would need more height. Sorry no math for you. The idea is the same as a dam except upside down. So bigger drop/rise = more energy. And in this case the hotter the air at the bottom the better (obviously). I think that is why in the drawing they show large heat collectors at the base.

Sadly I think 50ft might be the upper legal limit, so perhaps I need to massage the other pertinent factors/numbers to observe this limit.

Quote:

Originally Posted by mpolli

The tower itself is not the collector.

Thats correct, but we certainly don't want any cooling to take place in the stack itself, indeed more heat in the stack should equal some added acceleration of the airstream... at least this is the logic formulated by my admittedly limited brainpan.