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Author Topic: Mini solar tower  (Read 15555 times)

Offline Steven Dufresne

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Mini solar tower
« on: July 05, 2011, 10:41:37 PM »
Hi All,
This is something I've been trying just to see how far it can go. I have a 2'x4' fresnel lens which here in Ottawa, Ontario, Canada means I'm intercepting around 640 watts of sunlight in July. I then have a mini solar tower, basically a tube with an absorber inside it. The absorber uses the concentrated sunlight to heat the air in the tube. The hot air rises and when it exits the top of the tube, turns a turbine. Even if I end up with only 1% efficiency that means I should get 6.4 watts out. That's the plan anyway.

So far I'm done version 4 and am starting to make version 5. I haven't gotten any noticable airflow yet. In version 3 the internal temperature of the tube was only 65C (150F) but by version 4 it was at least 165C (330F). But that melted the extruded polystyrene I was using as insulation. For version 5 I bought some Roxul insulation, a mineral insulation, which should be able to take the heat.

Details at:
http://rimstar.org/renewnrg/mini_solar_power_tower_fresnel_lens.htm
along with videos for the different versions, or you could just go straight to the videos on youtube...
Versions 1, 2 and 3: http://youtu.be/v1aQ73ZdZVA
Version 4: http://youtu.be/zuLlz-YlrL8

I am having doubt's that the hot air will actually rise but instead just leave the tube from both ends, but version 5 should start giving some indications of success or failure.
-Steve
http://rimstar.org   http://youtube.com/rimstarorg

Free Energy | searching for free energy and discussing free energy

Mini solar tower
« on: July 05, 2011, 10:41:37 PM »

Offline FatBird

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Re: Mini solar tower
« Reply #1 on: July 06, 2011, 03:44:24 AM »
A better way is to shine the Hot SunLight on the Boiler of a Steam Engine, that drives a small generator.

There are hundreds of small steam engines for sale on Ebay.


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Offline FatBird

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Re: Mini solar tower
« Reply #2 on: July 06, 2011, 03:51:38 AM »
Here is a nice little Generator advertised for small Steam Engines.

.

Offline Steven Dufresne

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Re: Mini solar tower
« Reply #3 on: July 06, 2011, 05:01:00 AM »
@FatBird,
Yup, I'm aware of that option and have a stirling engine I plan on trying later once I have a mirror arrangement set up with the fresnel lens. For now I'm trying this mini solar tower idea.
-Steve
http://rimstar.org   http:///youtube.com/rimstarorg


Offline Cherryman

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Re: Mini solar tower
« Reply #4 on: July 06, 2011, 09:46:21 AM »
Hi, always nice to vids of people experimenting!

My two cents:  I think your solar tower is to short.  In order to get a better flow and pressure difference you could try more length, i do not think you will get any noticeable "torque" with such a short heating collector , which is as I understand open at both sides. 

See it as a chimney, it needs a certain length to work best.

I understand it is a proof of concept set-up, but in gthe end you might want to go for steam (1600x volume)  Or try a water cooled small solar-panel at the Fresnel focus  ;)

Free Energy | searching for free energy and discussing free energy

Re: Mini solar tower
« Reply #4 on: July 06, 2011, 09:46:21 AM »
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Offline Steven Dufresne

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Re: Mini solar tower
« Reply #5 on: July 06, 2011, 02:32:52 PM »
My two cents:  I think your solar tower is to short.  In order to get a better flow and pressure difference you could try more length, i do not think you will get any noticeable "torque" with such a short heating collector , which is as I understand open at both sides. 

See it as a chimney, it needs a certain length to work best.

Help me understand this then. There are three areas: the area where the absorber is and the air is being heated, a length of pipe below it, and a length above it. Which are you suggesting be longer? I've never worked with chimneys of any kind before.

One commenter in the video for versions 1, 2, & 3, archeryman5000, said to think of the hot air as like a balloon, I want a larger mass of it moving upward to create more lift so he suggested making the length above longer. Makes sense to me. Is that what you mean?
-Steve
http://rimstar.org   http://youtube.com/rimstarorg

Offline Cherryman

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Re: Mini solar tower
« Reply #6 on: July 06, 2011, 03:47:00 PM »
Help me understand this then. There are three areas: the area where the absorber is and the air is being heated, a length of pipe below it, and a length above it. Which are you suggesting be longer? I've never worked with chimneys of any kind before.

One commenter in the video for versions 1, 2, & 3, archeryman5000, said to think of the hot air as like a balloon, I want a larger mass of it moving upward to create more lift so he suggested making the length above longer. Makes sense to me. Is that what you mean?
-Steve
http://rimstar.org   http://youtube.com/rimstarorg

Well i'm not an expert either, but see it as reversed gravity.

If you have a long hose, filled with water, hold it vertical, the longer the hose, the more pressure there will be at the bottom, and thus force to get out.  ( At the other end a sucking force will be created )

Heated air acts the same, but the instead of going down, going upwards.

So the bottom part has to be a little longer to prefend escaping air downwards ( As you put up resistance at the top)  and the above part has to be even longer, so heat accumulates and takes up speed and "mass" before entering your generator.

I hope this makes a little sense.

« Last Edit: July 06, 2011, 04:34:33 PM by Cherryman »

Free Energy | searching for free energy and discussing free energy

Re: Mini solar tower
« Reply #6 on: July 06, 2011, 03:47:00 PM »
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Offline Steven Dufresne

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Re: Mini solar tower
« Reply #7 on: July 06, 2011, 04:10:21 PM »
@Cherryman,
Thanks for clarifying. Makes sense to me and I have just the tube, a 1 1/8" ID by 34" aluminium tube I picked up from Home Depot a long time ago. You can see it and the copius amount of Roxul insulation I recently bought in the photo below. I'll make it all today and hopefully the sun will come out sometime in the next few days to test.
-Steve
http://rimstar.org   http://youtube.com/rimstarorg

Offline ResinRat2

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Re: Mini solar tower
« Reply #8 on: July 06, 2011, 06:36:53 PM »
Hello Steven,

Thanks very much for sharing your project.

Are you basing it off the larger experimental solar towers like:

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

It looks like in these larger ones the bottom area around the tube is heated and the air updrafts into the tube naturally.

Good luck with your work, thanks again for sharing.

RR2
« Last Edit: July 06, 2011, 07:19:13 PM by ResinRat2 »

Offline Steven Dufresne

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Re: Mini solar tower
« Reply #9 on: July 06, 2011, 07:11:12 PM »
Hello Steven,

Thanks very much for sharing your project.

Are you basing it off the larger experimental solar towers like:

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

It looks like in these larger ones the bottom area around the tube is heated and the air updrafts into the tube naturally.

Good luck with your work, thanks again for sharing.

RR2

Thanks RR2.

Yup. I got the idea from those huge solar updraft towers.

I did some calcs this morning and using the aluminium tube I mentioned above and assuming the temperatures I measured with version 4 and assuming no losses I should get a stack effect draft/draught flow rate of 9.375 cm^3/s. That's a cube of air around 2 cm per side every second. It's not much but it's enough for me to continue. I got the formula from:
http://en.wikipedia.org/wiki/Chimney

-Steve
http://rimstar.org   http://youtube.com/rimstarorg

Free Energy | searching for free energy and discussing free energy

Re: Mini solar tower
« Reply #9 on: July 06, 2011, 07:11:12 PM »
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