I need some help with TECs....

maxSaleen · 03-11-2006, 10:48 AM

I'm working on a project to generate energy from a very hot liquid... its for school (UCF engineering)

The goal here is to generate electricity by having a high temperature loop heat up one side of a TEC, while having a low temperature loop cool the other side. This, in theory, should generate electricity. I've had a hard time finding equations showing how much energy could be generated. Here's what I'm working with:

TEC: 62x62 mm, 270-350w, 0-15v, 0-30 amps, operating range of -60C to 180C

Assume that the cold plates will have a very low C/W (.1 not hard to achieve in this application).

Assume that the cold side runs at 30C and the hot side runs at 180C. How much electricity will this thing generate?

Thanks in advance.

bobo5195 · 03-11-2006, 11:27 AM

Look into thermal couple and the equations which govern them (i can't remember the names of the top of my head).

There is quite abit of research into this area for micro power generation. I believe that stirling engines are far more efficent than thermo electric effects for converting heat into power. British gas in the UK is introducing stirling engine boilers for use in power generation in homes which is one nice app for your report.

TerraMex · 03-11-2006, 12:42 PM

Peltier-Seebeck effect?
http://www.peltier-info.com/tims.html

pilsn3r · 03-11-2006, 01:08 PM

Thermoelectric effect
You then need the material properties of your TEC. Exact material, size of cells and number of cells in series.
Your calculations wont be exact though because of thermal shorts, cooling/heating of liquid and imperfections in components and mounting.

maxSaleen · 03-11-2006, 08:38 PM

Thanks for the help so far guys.... keep the info coming.

What I've seen so far is that electrical generation is roughly 3% of the energy that is transferred accross the thermocouple. Does that sound on par to you guys? Could I take that to mean that the said 350w TEC would only produce 10.5w at the maxes of its operating temps? Thanks again.

Still reading....still learning...

maxSaleen · 03-11-2006, 09:25 PM

Allright, here are some details on my project....

I'm to figure out a way to recover energy from a kitchen. We are told:

Flow of air through the stove's "hood" 150 liters per second
Temperature of air 422 degrees kelvin
Temperature of ambient air 294 degrees kelvin

My initial (flawed) calculations (assuming hot side remains at 422K and cold side at 294K):

q=m c delta T
m=150L x 1.3g/L (mass of air)= 195g= .195kg
c= 1.009KJ/Kg x K
deltaT= 128K

This gives me 25.18 KJ/sec = 25,180w/second

If a TEC array can transform this at 3% that's 755w/second
At 1% ( ballpark, taking into account losses accross the cooling circuit, inability to absorb all of the heat from the exhaust) that's 251.8w/second or .069w hour.

Does that all seem right? Did I screw anything up?

pilsn3r · 03-12-2006, 03:53 AM

3%eff. seems normal.
Btw. RTGs are using the seebeck effect using heat from decaying radioactive materials.

Put a turbine (or prop) in the hood instead

maxSaleen · 03-12-2006, 02:37 PM

Thanks pilsn3r.

The problem with using the fan is that it would be converting mechanical energy (which is ironically produced mostly by the fans in the hood). We were instructed to convert the heat into electricity. Sterling generators are far more efficient at this, from what I've read, the only problem being their complexity. The TEC approach should be much simpler (if less efficient).

Thanks again for everyone's help. Keep it coming.... I could always use more info.

03-11-2006, 10:48 AM	#1
maxSaleen Cooling Savant Join Date: Dec 2004 Location: Orlando, Florida Posts: 383	I need some help with TECs.... I'm working on a project to generate energy from a very hot liquid... its for school (UCF engineering) The goal here is to generate electricity by having a high temperature loop heat up one side of a TEC, while having a low temperature loop cool the other side. This, in theory, should generate electricity. I've had a hard time finding equations showing how much energy could be generated. Here's what I'm working with: TEC: 62x62 mm, 270-350w, 0-15v, 0-30 amps, operating range of -60C to 180C Assume that the cold plates will have a very low C/W (.1 not hard to achieve in this application). Assume that the cold side runs at 30C and the hot side runs at 180C. How much electricity will this thing generate? Thanks in advance.

03-11-2006, 11:27 AM	#2
bobo5195 Cooling Savant Join Date: Aug 2005 Location: uk Posts: 400	Re: I need some help with TECs.... Look into thermal couple and the equations which govern them (i can't remember the names of the top of my head). There is quite abit of research into this area for micro power generation. I believe that stirling engines are far more efficent than thermo electric effects for converting heat into power. British gas in the UK is introducing stirling engine boilers for use in power generation in homes which is one nice app for your report.

03-11-2006, 12:42 PM	#3
TerraMex Cooling Savant Join Date: Nov 2002 Location: Portugal, Europe Posts: 870	Re: I need some help with TECs.... Peltier-Seebeck effect? http://www.peltier-info.com/tims.html __________________ "we need more cowbell."

03-11-2006, 01:08 PM	#4
pilsn3r Cooling Neophyte Join Date: Sep 2002 Location: sweden Posts: 17	Re: I need some help with TECs.... Thermoelectric effect You then need the material properties of your TEC. Exact material, size of cells and number of cells in series. Your calculations wont be exact though because of thermal shorts, cooling/heating of liquid and imperfections in components and mounting.

03-11-2006, 08:38 PM	#5
maxSaleen Cooling Savant Join Date: Dec 2004 Location: Orlando, Florida Posts: 383	Re: I need some help with TECs.... Thanks for the help so far guys.... keep the info coming. What I've seen so far is that electrical generation is roughly 3% of the energy that is transferred accross the thermocouple. Does that sound on par to you guys? Could I take that to mean that the said 350w TEC would only produce 10.5w at the maxes of its operating temps? Thanks again. Still reading....still learning... Last edited by maxSaleen; 03-11-2006 at 08:46 PM.

03-11-2006, 09:25 PM	#6
maxSaleen Cooling Savant Join Date: Dec 2004 Location: Orlando, Florida Posts: 383	Re: I need some help with TECs.... Allright, here are some details on my project.... I'm to figure out a way to recover energy from a kitchen. We are told: Flow of air through the stove's "hood" 150 liters per second Temperature of air 422 degrees kelvin Temperature of ambient air 294 degrees kelvin My initial (flawed) calculations (assuming hot side remains at 422K and cold side at 294K): q=m c delta T m=150L x 1.3g/L (mass of air)= 195g= .195kg c= 1.009KJ/Kg x K deltaT= 128K This gives me 25.18 KJ/sec = 25,180w/second If a TEC array can transform this at 3% that's 755w/second At 1% ( ballpark, taking into account losses accross the cooling circuit, inability to absorb all of the heat from the exhaust) that's 251.8w/second or .069w hour. Does that all seem right? Did I screw anything up? Last edited by maxSaleen; 03-11-2006 at 09:33 PM.

03-12-2006, 03:53 AM	#7
pilsn3r Cooling Neophyte Join Date: Sep 2002 Location: sweden Posts: 17	Re: I need some help with TECs.... 3%eff. seems normal. Btw. RTGs are using the seebeck effect using heat from decaying radioactive materials. Put a turbine (or prop) in the hood instead

03-12-2006, 02:37 PM	#8
maxSaleen Cooling Savant Join Date: Dec 2004 Location: Orlando, Florida Posts: 383	Re: I need some help with TECs.... Thanks pilsn3r. The problem with using the fan is that it would be converting mechanical energy (which is ironically produced mostly by the fans in the hood). We were instructed to convert the heat into electricity. Sterling generators are far more efficient at this, from what I've read, the only problem being their complexity. The TEC approach should be much simpler (if less efficient). Thanks again for everyone's help. Keep it coming.... I could always use more info.

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