Author Topic: Converting heat to electricity  (Read 12056 times)

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The Crazy Noob

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Converting heat to electricity
« on: January 21, 2006, 11:41:51 AM »
Hi


I would like to know what the best but also the cheapest way to convert heat into electricity is. The goal is to buy a few cheap page-magnifiers (fresnel lenses) and aim their focal point at the same spot. If the sun then shines into the lenses, the spot where they're aimed at will get quite hot (~300-400degC ?).

I had a few things in mind to convert this to useful electricity:



  • A series of thermocouples (2 different types of metal) but I think that this won't produce much power.
  • A (DIY) steam engine but this is harder to make and has rotating parts that wear out after a while.
  • Just using the lenses to focus the sun on a PV-panel (but because i don't have one and don't feel like buying one; this isn't an option)


From these options I prefer the first one (thermocouples) because it seems to be the most simple, low-cost solution.


If anyone has a better way (efficienty vs. cost) to achieve the same goal (heat -> electricity) please say so.




The Crazy Noob

« Last Edit: January 21, 2006, 11:41:51 AM by (unknown) »

wooferhound

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Re: Converting heat to electricity
« Reply #1 on: January 21, 2006, 06:57:39 AM »
I don't think you can aim multiple fresnel lenses at a single spot


Better to search on "thermopile" which are clusters of thermocouples in one unit.

Or here are some excellent Links...


http://www.thermonamic.com/Pspec.html


http://www.varmaraf.is/engl/prod.htm


http://www.powerchips.gi/


http://www.dts-generator.com/


http://www.hi-z.com/


http://www.remote-site.com/thermo.html

« Last Edit: January 21, 2006, 06:57:39 AM by wooferhound »

Norm

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Re: Converting heat to electricity
« Reply #2 on: January 21, 2006, 06:57:50 AM »
 try this one....

http://www.rotarystirlingengines.com/rotacola.htm

wouldn't necessarily need a fresnel lens.

                  ( :>) Norm.
« Last Edit: January 21, 2006, 06:57:50 AM by Norm »

The Crazy Noob

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Re: Converting heat to electricity
« Reply #3 on: January 21, 2006, 09:17:01 AM »
try this one....

http://www.rotarystirlingengines.com/rotacola.htm

wouldn't necessarily need a fresnel lens.





I like the simplicity of that one, especially when balloons are used as reservoirs ( http://www.rotarystirlingengines.com/sexbaloon.htm ). Has anyone got this style of engine driving a (small) generator? The engine they use maybe produces 0.5-1W; if you would make one with 20 of even 30 cans, you may be able to squeeze out 5-10W!


Thanks for the great link!

« Last Edit: January 21, 2006, 09:17:01 AM by The Crazy Noob »

Texas Al

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Re: Converting heat to electricity
« Reply #4 on: January 21, 2006, 09:33:42 AM »


From these options I prefer the first one (thermocouples) because it seems to be the most simple, low-cost solution.


Has anybody actually seen low-cost thermocouples? From my searching even small ones used for CPU-cooling are pretty pricey relative to what they could generate.


I'd also like to repeat and broaden an earlier poster's question about Stirlings...


Do any of you have a working Stirling engine, and how much energy is it putting out, on how much of a heat-difference?

« Last Edit: January 21, 2006, 09:33:42 AM by Texas Al »

willib

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« Last Edit: January 21, 2006, 09:37:20 AM by willib »
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hvirtane

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Re: Converting heat to electricity
« Reply #6 on: January 21, 2006, 09:47:25 AM »
Do any of you have

a working Stirling engine,

and how much energy is it putting out,

on how much of a heat-difference?


Please see 'WindstuffEd's site:

http://www.windstuffnow.com


- Hannu

« Last Edit: January 21, 2006, 09:47:25 AM by hvirtane »

ghurd

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Re: Converting heat to electricity
« Reply #7 on: January 21, 2006, 10:22:51 AM »
They make them different for generating power than for cooling. Not sure how great the difference is.


The price is going down. Brand new 66W for $8~9 is the best I have seen, but that was just the device, no heatsink etc.  I'd like 1 amp at 12V out of the woodstove.

G-

« Last Edit: January 21, 2006, 10:22:51 AM by ghurd »
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Texas Al

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Re: Converting heat to electricity
« Reply #8 on: January 22, 2006, 10:33:03 AM »
Those look like model projects that put out just a few watts, and the site doesn't specify how many. I've still to see any individual building a Striling that puts out power that's anywhere close to wind, hydro, or photovoltaic.


So I'm wondering what the limitation is? Is it simply because it's less cost effective than PV? Or are there some fundamental limitations on how much a Stirling engine can scale?

« Last Edit: January 22, 2006, 10:33:03 AM by Texas Al »

asheets

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Re: low cost thermocouple
« Reply #9 on: January 23, 2006, 10:23:39 AM »
Get yourself a copy of an old Gates Rubber Company (GRC) technical handbook.  My copy (which predates me, by the way), has a wonderful section on thermocouple/thermopile/peltier/seebeck-effect, including the various temperatures and output voltages of many different metal combinations.


I wish I could find an equivalent list somewhere on the Internet, but so far my search has come up empty (and I don't have my GRC book with me at the moment).  But you might want to try something as simple as twisting together a piece of copper with a piece of aluminum, then heating that puppy up while connected to a sensitive voltmeter.

« Last Edit: January 23, 2006, 10:23:39 AM by asheets »

Texas Al

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Re: Converting heat to electricity
« Reply #10 on: January 24, 2006, 07:43:40 AM »
Where did you see these being sold?
« Last Edit: January 24, 2006, 07:43:40 AM by Texas Al »

Texas Al

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Re: low cost thermocouple
« Reply #11 on: January 24, 2006, 07:44:57 AM »
What's the ISBN number on that book? And are you sure it isn't the Chemical Rubber Company, CRC? Because I've seen a lot of technical manuals by CRC, but never heard of GRC.
« Last Edit: January 24, 2006, 07:44:57 AM by Texas Al »

The Crazy Noob

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Re: low cost thermocouple
« Reply #12 on: January 24, 2006, 08:37:32 AM »
« Last Edit: January 24, 2006, 08:37:32 AM by The Crazy Noob »

ghurd

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Re: Converting heat to electricity
« Reply #13 on: January 24, 2006, 08:46:59 AM »
Maybe Circuit Specialists?
« Last Edit: January 24, 2006, 08:46:59 AM by ghurd »
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asheets

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Re: low cost thermocouple
« Reply #14 on: January 24, 2006, 10:12:37 AM »
Yes, you are right -- it is CRC, not GRC (I have a contract gig at Gates Rubber next week -- that's why I've got them on the brain).  GRC makes fan belts and radiator hoses -- I'm surprised you've never heard of them.


My copy is too old to have an ISBN (like I said, it predates me), but the 86th edition of the CRC Handbook of Chemistry and Physics is out right now -- http://search.barnesandnoble.com/booksearch/isbnInquiry.asp?userid=ve3iBWSCFy&isbn=0849304865&am
p;itm=1 -- ISBN: 0849304865 -- a true bargain, IMHO, at $101.

« Last Edit: January 24, 2006, 10:12:37 AM by asheets »

Clifford

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Re: Converting heat to electricity
« Reply #15 on: January 25, 2006, 09:44:18 PM »
Adding multiple lenses could be done with mirrors or prisms above or below the Fresnel Lense.


There is no reason why the "Fresnel" technology couldn't be made to be assymetric to allow an offset focus allowing the incorporation of multiple lenses.  But, in reality, this would be about the same thing as just starting with a larger lens.


Can you buy a parabolic Fresnel Mirror?


That brought up another idea...


http://www.klimaschutz.com/synth/sfc021001.htm


By using strips of flat mirrors (or strips of prisms), one could heat a long pipe rather than heating a single point.


It might make it easier to design your heating element.


BTW...  you would almost need to add a solar tracker.

« Last Edit: January 25, 2006, 09:44:18 PM by Clifford »

zyewdall

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Re: Converting heat to electricity
« Reply #16 on: February 13, 2006, 03:39:28 PM »
I've fooled around with the peltier junctions trying to generate electricity from woodstoves.  You can probably get a few watts from a "65 watt" peltier junction, but they're not that efficient.  Or easy to control without accidentally cooking them.  I still think it's the way of the future, but right now, its hard to get anything to live up to the theory.


What I would recommend, as a working solution, is a small steam engine (like the toy ones you used to be able to buy, back in the 50's), turning a DC motor as a generator.  Probably get a few watts out of that too, for less headache than the peltier junctions. More moving parts, yes.

« Last Edit: February 13, 2006, 03:39:28 PM by zyewdall »

sjwartist

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Re: Converting heat to electricity
« Reply #17 on: April 27, 2007, 09:51:25 AM »
It seems to me that this is the area lacking most behind in development.  The potential is huge. Both Solar PV's and Heat conversion could be used together to increase output and counter the lack of sunlight.  Heat can occur with or without sunlight.  As far as my understanding goes no one has developed a viable and effecient way to take advantage of it.  There must be and effective way according to the laws of physics and energy conversions that occur naturally in nature.


I know just from my minor experiments growing up that certain chemicals mixed together can generate enormous amounts of heat.  The trick would be finding ones that don't degenerate. Heat also excites electrons and causes different elements to change and move.  There has to be a way other than with steam, gasoline explosions and moving parts to take advantage of this molecular reaction and convert it to electricity.  Take the lithium-ion battery for example.  It stores energy and can be recharged based soley on chemical reactions and the introduction of an external stimulant.  


What about EM, gravity & thermocouples?  Why can't the three forces be used together?  When traditional ferrous magnets are put in a spin they stabilize enough to maintain a stationary position, active electronic stabilization This counters Earnshaw's theorem.  When they are not spinning they are extremely sensitive to external conditions.  Even static electricity throws them off balance.  If we had a room temperature superconductor that wouldn't require super cooling this would be a lot easier, permanent and cost effective, considering the effect they have with diamagentics.  


If multiple microscopic thermocouple threads were bound together into a cable and encapsulated in the correct chemical, I would think it would increase the charge that could be generated.  Similar to how the effect of cupris oxide on copper effects the amount of photons captured and converted into electricity in the appropriate liquid, i.e saltwater, vinegar.


Now based on the sensitivity of ferrous magnets, and heat generated in a variety of ways, i.e. fresnal lens to magnify and concentrate sunlight onto the thermocouple twist even with only a minimal charge which would still increase based on the amount of heat, wouldn't it be enough to affect the N,S magnetic attraction and reppeling of ferrous magnets, acting like an electromagnet. Combine that with gravity and with no prior movement, or other external electrical current a constant spin should be viable.  That's the problem with modern motors and generators they typically require an external power source like a battery or electricity from an outlet.  The electro-magnetic force causes the N,S, poles to attract and repel in turn creating the spin wich turns whatever it's hooked up to.  I don't see why this couldn't be done on a nano-molecular level or any other level for that matter with multiple spinning magnetic discs all tied together.  Anyone tried or trying any of this?


What do you think?

« Last Edit: April 27, 2007, 09:51:25 AM by sjwartist »

dinges

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Re: Converting heat to electricity
« Reply #18 on: April 27, 2007, 11:40:20 AM »
"What do you think?"




« Last Edit: April 27, 2007, 11:40:20 AM by dinges »
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allthumbs

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Re: Converting heat to electricity
« Reply #19 on: September 22, 2007, 07:34:29 PM »
There is a company that is doing just what you propose with fresnel lenses.  I went to a alternative energy seminar in Tucson, AZ.  One of the booths was demonstrating a fresnel holographic panel that produces more energy for a lower cost per panel and a longer life.  With this technology a fixed panel tracks the sun by bending the light rays and uses only the part of the light spectrum that is useful for solar energy. Their website is:  http://www.prismsolar.com/  They are building a factory in Tucson. Unfortunately they do not sell to home owners.

AT
« Last Edit: September 22, 2007, 07:34:29 PM by allthumbs »