Peltier power generator
P!-Ro
Posts: 1,189
I was just coming back from Grand Junction when I thought about using the sun and a peltier junction to create green energy. What I was thinking of is having a black metal plate on top soaking solar heat with a peltier on the bottom placed over a heat sink. Then, heat could be transferred from the hot metal·top to the cooler bottom generating electricity. I would want a prop to control everything in this process, boosting electricity levels if it is not high enough to charge the battery, turning it off if there is not enough power, and possibly switching the electricity to appliances from an inverter to the outlet depending on how much power·is available.
I'm sure much of this task will be difficult, especially the last part of switching power sources, so I thought I would ask those on these forums first before I purchased a peltier and attempted anything. Please leave any comments you please, or request clarification if necessary, and thank you to·all who post.
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PG
I'm sure much of this task will be difficult, especially the last part of switching power sources, so I thought I would ask those on these forums first before I purchased a peltier and attempted anything. Please leave any comments you please, or request clarification if necessary, and thank you to·all who post.
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PG
Comments
edit: I took out the reference, since on second thought it's a $30 purchase fee for the article. If you have a college or university access then you can probably go through there, otherwise you'll just have to take my word for it.
Post Edited (SRLM) : 8/17/2009 4:56:27 AM GMT
Also, I thought I'd mention there is a good possibility the metal can get 150+ degrees. The top will be black, it will have a wind block, and the bottom will be insulated. I might even try to put glass over the top to prevent any heat from escaping. To cool the peltier at the bottom, I'm thinking about using a funnel to work any wind to my benefit. Water is also another possibility for cooling.
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PG
With solar the bigger problem may not be collecting the heat, but rather keeping the cool side cool. Eg do you go for fins, or fins plus fan, or cold water? An interesting little experiment is to put some heat on one side and a computer fan on the other side and see if you can make enough power to run the computer fan to keep the cool side cool.
Buy one and do some experiments - it is great fun!
I also have a solar panel about the same size; it can generate ~5VDC in direct sunlight and more than 1VDC in the shade.
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--Steve
Propalyzer: Propeller PC Logic Analyzer
http://forums.parallax.com/showthread.php?p=788230
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PG
Three of them in series ($20 a pop) were enough to power a small portable (3V) radio from candle power for about 10 min, and then you had to let the whole thing cool for about 20 min before you could do it again.
I think if you wanted to go Solar-Thermal, that you would be better off with an 'external combustion' or Sterling Engine approach.
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 8/17/2009 5:36:37 AM GMT
Or why do you have more heat then light available over the year?
Nick
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Never use force, just go for a bigger hammer!
The DIY Digital-Readout for mills, lathes etc.:
YADRO
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PG
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PG
And Stirlings are much more efficient with temp.-difference.
Nick
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Never use force, just go for a bigger hammer!
The DIY Digital-Readout for mills, lathes etc.:
YADRO
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PG
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PG
<
Nick
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Never use force, just go for a bigger hammer!
The DIY Digital-Readout for mills, lathes etc.:
YADRO
I find the concept of a Fluidyne-pump very interesting ... This could be accomplished with a relatively low thermal differential.
http://www.thermofluidics.co.uk/technology.htm
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 8/17/2009 6:22:36 AM GMT
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PG
<
Or a different setup:
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Nick
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Never use force, just go for a bigger hammer!
The DIY Digital-Readout for mills, lathes etc.:
YADRO
I've been pondering heat engines for the last 10 years. I guess it is worth saying you probably are not going to discover an amazing new source of energy that no-one else has thought of. It all comes down to $/watt, and a large scale coal fired steam turbine still comes out the cheapest.
But, there are some fascinating things to research and to amaze your friends with. Stirling engine, small steam engines, low temperature stirling engines, fluidyne, numerous solar designs that use the Carnot cycle in some way. Even the elusive Carnot engine, which no-one has ever built. (Now there is a challenge you can't resist!)
Start by having a look at the Carnot cycle. Thermodynamics is one of those subjects that looks simple, but the more you study it, the more complicated it becomes. It explains things like why internal combustion engines displaced steam (and stirling) engines in the late 1800s, how power stations work, how jet engines work and all sorts of other processes.
There are some great little models you can buy on the internet from many suppliers. Eg a stirling engine that spins from the heat of your hand. But you would need a lot to power your house. And, of course, if you just wanted to charge a battery using the sun, solar panels are still the simplest method.
There is also a new fuel cell technology about to become available to the public (2009 - I hope
although this runs on natural or LP gas - it is certainly interesting and something I'd consider.
Solar cells are expensive to get any real power from and certainly require battery storage for when night falls or bad conditions prevail - batteries are really, really expensive for any serious storage capacity; given their life-span about the time you can start to get the initial return on investment for such systems, the batteries may be approaching end of life.
Have you also considered wind and/or a hybrid system that is a mix of the various technologies already proposed? This can provide a smoother power availability during different conditions; ie: no sun but wind etc.
I don't know where you are geographically but also, your heatsink could be bonded to an aluminium post buried underground to also exploit geo-thermal technologies; the ground several feet under remains at a relatively constant temp so this could amplify the heat conduction away from your peltier device(s). Perhaps watering around the post might also help dissipate the heat directly around the post (I haven't tried this but it sounds feasible)
Switching with the Propeller would be quite straightforward; depending on the amount of voltage/current; transistors, FETs or Triacs may be useful else relays may prove more economical if larger power values are involved.
The Propeller could use several pins for measusing the voltage (drop) from your input sources; this could be simple "switch" using a bias current to provide a binary value or an RC circuit to provide analogue data. A form of multiplexer could select the highest power developing device to switch into your batteries (or load). There are many "charge controllers" on the market that can take multiple input sources and/or provide performance statistics to a serial interface (could be sent to the Propeller too).
It depends on the level(s) of sophistication you want and how much you want to spend.
Solar panel prices have risen quite a bit of late ;-(
Come to think of it, A Propeller based Charge Controller would be a great project!
Cheers,
HarryE.
The amps are just bound to increase....no idea how much heat they can take but since they are silicon it
should be at LOT. Old surplus mirrors would be cheaper than adding solar cells...maybe mirrored mylar sheeting
could be used instead of mirrors.
Maybe build a device using a propeller to keep the solar cells and mirrors aligned properly to the sun.
In concept your idea has merit, but practical implementation for anything but a token amount of power is not so simple. I messed with this same concept some 15 years ago when I had one of those Pelletier DC powered coolers. One day it had been running was quite cold inside, then it was unplugged, and later I noticed its circulating fan was still running. I can't recall if it reversed direction or not. That triggered the idea of using those elements for power generation.
I sacrificed the cooler, and removed the element. Next I got a small propane torch, and put a bit of heat to one side of the junctions, making sure I did not melt the solder, and measured the output. A watt or thereaouts as I recall. Certainly enough to runs some instrumentation in remote Northern sites.
There are commercial products available that do this by burning natural gas or propane. The smallest available profide some 50 watts, and larke ones many Kilowatts. With prices to match, from a few K$ to $250,000 or bigger I'm sure. They operate at sites where no commercial power is available, and on the larger units they have converters that change the low voltage DC output to AC power.
The company I'm familiar with purchased the technology from 3M in the early 70's, and has gone through some name iterations, last one I remeber was Global Thermo Electric in Calgary AB.
But for your idea, sunshine should work -when the sun is shining of course- but ground heat/cold would also work. Lookup 'thermal siphon' to pull a small bit of heat out of the ground (in COLD climates), or push heat into the ground in HOT climates.
A few watts, sure but don't worry about switching circuitrty or powering your house, it's not practical for anything like that. At least on a small economic scale.
Have fun experimenting with this!
Cheers,
Peter (pjv)
Any way just use the generated electricity to run a fan to cool the cool side.
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Style and grace : Nil point
I'm not sure what your goals are with the Peltier but before you get too ambitious, do yourself a favor and take time to learn something about heat transfer. Peltier devices are not very efficient, so it will be a challenge to get much power out of them. Even if your Peltier exists in a sunny, cold climate, there must be "something" that continuously removes the heat from the cold side of the Peltier so that your temperature differential is maintained. If we assume that the "something" is a fan, then the fan needs power to run and so the fan will eat into your total energy output equation. If you hope to use the wind, think about how the wind is going to cool the cold side of the Peltier but somehow not cool the warm side at the same time. When it comes to heat transfer, boundary layers become one of your biggest enemies whether you use air or liquids. Even if the cold side of the Peltier is setting on top of solid ice, consider that ice is not a very good conductor of heat. Heat transfer concepts can sometimes be somewhat counter intuitive, so if you don't learn a little about them in the beginning, they might bite you in the end.
I'm not telling you this to cast road apples at your parade; it's just that I have learned in the past that a lot of people think heat transfer should be a no-brainer and yet very often they get burned by the surprise that it's not.
good luck,
Mark
As for you steam idea I have one question for you: How much money do you think I have?
@Beau--that pump looks interesting, but I can't figure out how it could create electricity. If you know of a way, please tell me.
@Dr. Acula--I'll look into it when I have more time. And no, I probably won't be able to resist.
@he1957--I was thinking of starting small and going big. Maybe start with some sun-driven power generation and then add in wind and then more farther in the future. Right now I just wish to get a simple prototype working.
@HollyMinkowski--It's a possibility but I would have to figure out how to efficiently move both the solar panel and the mirror, which I don't know how to do.
@pjv--Thanks for the insight. I don't mind if the power generation is small, but I would like it to be able to create enough that I could at least power a few small appliances with it, even if it's only for a couple minutes. Once I can get it this far, I could easily add more to the system and make it better with time.
@Toby--I'll look around and see if I can find the peltier you're talking about. As for cooling the hot side, I was thinking ditch water would be better since it is colder than the air. I just have to find the best way to do this.
@Mark--I'm sure I can figure it out, I'm used to fixing mistakes. If one plan doesn't work, you can easily expect me to make a new one.
Thanks to all your great ideas everyone, I'll look into my options a little more now.
-Derrick
-Derrick
Good luck..... but as Scottie from StarTreck said "I CANNO CHANGE THE LAWS OF PHYSICS", and it seems you are bent on proving him wrong.
As you said "how much money do you think I have?" ....and... to "easily add more to the system and make it better with time" are mutually exclusive.
Running areal appliance (toaster ?) is out of the question unless you DO have a lot of money.
Be happy with a couple of watts.... the real value is in the experimentation and that will be fun!
Cheers,
Peter (pjv)
For heavens sake dont take the fan as a serious surgestion !
Prepetual motion thoughts were afoot. A baking sun and an ice cold mountain stream would hold promise.
(over here green energy is just another tax thread)
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Style and grace : Nil point
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PG
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PG
That panel on the electric fence thing looks about the size of ones we used on some
remote sensor packages that radio data back....you can store a good deal of power
even from a panel that small.... maybe you could use those 2.5v 100 farad capacitors
instead of batteries.
There is a design for a simple wind generator that instead of blades has a mylar ribbon that flutters and moves a magnet back and forth across a small coil.
There are videos on the web... search for - flutter wind generator - and you should pick them up.
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- Some mornings I wake up cranky.....but usually I just let him sleep in -