# Help Mini-Solar Updraft Tower

1. May 3, 2010

### MightyJayJay

Help!! Mini-Solar Updraft Tower

I need to design and build a "miniature" solar updraft tower and generate the maximum power possible. The only constraints are that there will be a 500W lamp placed 1ft from the ground and 1ft from the chimney oriented at a 45 deg angle. My question is basically about what materials should be used and if the collector area should be 360deg around the chimney or just a section because the light source is fixed? All this while minimizing COSTS.

For the collector area I'm thinking of using a clear plastic so that light can come in without problems to create a greenhouse effect. For the baseplate I think I will use wood with a reflective surface like aluminum foil on top so that it does not absorb too much energy, because I'm not looking for a capacitance effect. For the chimney I'm still looking for accessible materials with low surface roughness. Should the chimney be a thermal conductor or an insulator?? And what method can I use to determine the diameter and height of it. I think I should balance the losses due to pipe friction while maximizing the pressure difference but how can I if I have no idea of the velocity of the air inside the chimney? (Should I just assume certain values?)

Any ideas and comments are welcome, THANKS!!

2. May 3, 2010

### RTW69

Re: Help!! Mini-Solar Updraft Tower

Do a Google search on "Solar Chimney" this idea was used to passively cool greenhouses. the physics is very similar to chimney design for wood stoves, boilers etc. Only the side facing the solar source is glazed, the inside is smooth and painted black. You may want to focus the light source on the collector with some sort of a reflector. The energy from the light source heats the air causing a density difference. You might be able to model this as a vertical pipe with internal heat generation equal to the amount of energy captured by the collector. You should be able to calculate the air velocity and mass flow rates. You may also want to place a fin on the pipe to maximize the heat collection surface.

3. Jul 15, 2010

### swagatam

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