How big would a solar chimney need to be for 2 kW per day in California?

[NoTime]

http://alt-e.blogspot.com/2004/11/solar-chimney-for-california.html

Anybody have some idea of the calculations that go into designing something like this?

I'm kinda wondering how big it would need to be to get 2KW a day out of it.

 

[Rach3]

There are no kilometer-high (3200-foot) towers in the world. Can you think of why that might be?

 

[russ_watters]

We've discussed this before and my perception of the idea is that it is just plain a scam for bilking money out of the government and gullible investors. The proposal for Australia is far behind where they said they'd be and near as I can tell, they haven't done anything other than issue press releases (I waded through a couple of annual reports a year or so ago and there was nothing of value being done). There is no engineering being done to conquer the monumental (pun intended) problem of building a 1km tower.

 

[Artman]

http://alt-e.blogspot.com/2004/11/solar-chimney-for-california.html

Anybody have some idea of the calculations that go into designing something like this?

I'm kinda wondering how big it would need to be to get 2KW a day out of it.

What you are dealing with to calculate this is stack effect. Design your turbine, figure out how much air movement you need to turn it, then calulate the cfm of air motion from stack effect to determine the temperature difference and height requirements to create it.

Here is a stack effect calulator and calculation.http://www.chuck-wright.com/calculators/stack_effect.html"

 

[Artman]

Easier still, look up some cfms of fans and the watts required to produce that cfm.

For instance, the 4500 cfm fan mentioned in the link I gave uses approximately 200 watts. It would require approximately 4 square foot chimney 200 feet high to move that much air when it is 100 deg F in the building and 70 deg F outside. And that will only generate 200 watts.

As Russ was saying, to build a structure large enough to produce enough power to make it worth while, is probably currently not possible.

 

[NoTime]

Does the one they claim in spain exist?

 

[NoTime]

Easier still, look up some cfms of fans and the watts required to produce that cfm.

For instance, the 4500 cfm fan mentioned in the link I gave uses approximately 200 watts. It would require approximately 4 square foot chimney 200 feet high to move that much air when it is 100 deg F in the building and 70 deg F outside. And that will only generate 200 watts.

As Russ was saying, to build a structure large enough to produce enough power to make it worth while, is probably currently not possible.

Thanks for the BOE and calculator.
Doesn't look too promising.

 

[NoTime]

There are no kilometer-high (3200-foot) towers in the world. Can you think of why that might be?

Any particular reason it has to go straight up?
Lots of nice handy mountains around.

 

[russ_watters]

The plant in Spain exists and produces 50 kw.

The idea probably wouldn't work all that well along the side of a mountain - the extra distance and terrain would vastly reduce the airflow.

 

[Artman]

The plant in Spain exists and produces 50 kw.

The idea probably wouldn't work all that well along the side of a mountain - the extra distance and terrain would vastly reduce the airflow.

I was thinking that the air would cool too much and also reduce the air flow.

 

[NoTime]

The plant in Spain exists and produces 50 kw.

The idea probably wouldn't work all that well along the side of a mountain - the extra distance and terrain would vastly reduce the airflow.

If you walk south along the border between Nevada and Cali at the top Heavenly you get a very nice view of the Nevada desert a mile or 2 below.
The drop is probably less than 30 degres off vertical for a few thousand feet.
A little digging might do quite a bit better than that.

According to the web page the effect of extra height is exponential.
I'm thinking that for small tilt angles the reduction might be more on the linier side.

Some mines are several miles deep so it probably isn't out of the question to bore straight down inside a mtn.

I have no idea about what the relative costs of any of this might be vs just building a tower. Just curious.

 

[NoTime]

I was thinking that the air would cool too much and also reduce the air flow.

This is from your calculator website.
Any idea of why this might be so?
Is it related to your idea of cooling?
Of course, most buildings arn't that high, so that could be a factor.
Edit: Ususally push is as good as pull, so why would heating the top make a difference.

An interesting variation on this theme is the so-called "solar chimney". Imagine that at the top of the building, air flows through a duct that is heated by the sun. The added height and temperature difference could combine to significantly increase air flow, if designed carefully.