Thiago,
Thank you for your two videos and your explanation.
I am thinking square or rectangular copper tubing 40mm X 20mm X 1000mm with the Peltier junctions attached directly between them.
Then you can build a manifold.
Copper is expensive, but you can braze or solder it yourself. Aluminum would work as well but then you need a TIG welder.
There is still a fundamental thermodynamic problem though. You have to reject 10,000 Watts of heat to get 500 watts. You cannot send that heat outside. You have to be able to use that heat. Otherwise you are throwing money outside the door. How many pellets does it take to make 10,000 Watts worth of heat? That’s the problem.
2.2 kilograms of pellets to make 10000watts of heat which makes 500watts of electric. Is that about half an Euro?
Google is telling me that LPG is €0.895/liter in Riga. LPG is the gold standard for off grid fuel because you are buying everything, fuel filter, fuel pump, uncontaminated, infinite shelf life, no electric needed, efficient burner.
1 liter of propane= 7.08kWh
Alright, I have to get out there. I have take down the firewood trees before the bugs and leaves come out.
Thank you Bruce,
I’m thinking along these lines too.
I want to buy those big gas tanks 2200kg, it will last a long time (as long as the tank lasts).
About the pellets. I’m already burning about 3-4 tons (kg) per year to heat the house/water, I will build one of these TEG plates and see during this next winter if the pellet consumption will increase and also by how much. My burner has 2 doors that I swap when I want to burn pellets (automated) or firewood that I also have stored and usually burn when there is a cold night outside if the winter.
You’re right about pellets for electricity is not the best trade, but as I already use it, if the extra burn to keep up any drop is between 0-15% then is ok since there are no moving parts and it’s quiet.
Think of it as a recovery system.
I think I did watch too much Star Trek and my property is becoming the USS enterprise, I have most systems in redundancy. Unfortunately we live in a very weird period of time in this part of the world and it’s hard to know if or when things won’t be available anymore. At the same time i have fun in learning and exploring new things.
About the “radiator” I wonder if an “empty box” or with serpentines inside. About the welding, it is a problem I do not know how to operate this type of tools yet and I was thinking of bringing the CAD design file to a shop that could make it happen to me.
Good luck with the trees there! I’m happy I’m done with this task for this season
Hello Thiago, you have an interesting project, well, exploiting heat flow and converting it into electricity has allowed humanity to develop as we know it today. Most electricity is produced with heat flow turbines, represented by steam turbines (coal-fired thermal power plants, nuclear power plants), … but you probably already know that. In 1821, the German physicist Thomas Johan Seebeck discovered the phenomenon of voltage on a metal rod when there is a temperature difference between the ends, this has now been made useful with semiconductors.
I drew a hydraulic diagram of a system for domestic use, here you can see that you waste about 8 kW of power in exchange for producing 500W, but if you were to cool the cold side with an underfloor heating system (25/30°C mode), you would produce a little less electricity, but all the heat would remain in the house.
Hi Tone, this is exactly what I’m trying to build, not sure why I’m not able to explain or express myself correctly here. It seems most comments are missing the details I’m trying to explain but yes, what you showed here is what I’m trying to do, and my challenge is how physically to create these 2 flat surfaces (cold and hot). I won’t be burning pellets just for that, so I guess the small amount of temp I would lose by pushing the hot water through the TEGs before going back to my hot system would not increase too much the pellet/wood consumption and can be dismissed since I’m already burning anyway and I have a good supply of this in my land.
My experiment was just with 10 TEGs and a surface of 80mm x 200mm x 5mm, obviously this was just for validation and it worked, I managed to charge my phone.
I don’t understand much about radiators, heat sinks and dissipation, and the flow needed, that’s where I’m looking for suggestions.
Thank you for taking the time. Finally, someone saw the full picture of what I’m trying to say.
all you are making is a heatsink.
Usually they are cast aluminum.
take a copper pipe, bend to how you want the liquid to flow through it.
Put it in your heatsink mold.
pour aluminum to make the heatsink.
machine it flat.
attach with a very thin layer of thermal paste to your TEG.
in this case, you could probably use blocks, because you will most likely need to insulate the outside of the block.
This whole thread is way beyond what my calcified geezer brain can grasp as far as TEG power production is concerned but I can chip in about the pellet stove waste heat and thermal mass is the only way to utilize waste heat from a wood or pellet burner. I have explained my heating systems before with tons of stone and concrete in the house, hydronic floors with water heated in the wood stove and a large clay filled heat storage bed locking up the heat from the rocket mass heater in the greenhouse. Despite burning full air fed fuel my flue temps in the house seldom reach 300f and are usually between 250 and 280F. The flue from the RMH in the greenhouse stays in the 70F range. That means most of that heat the stove produces is stored in the mass. I’m Still trying to figure out a way to capture waste heat from the gasifier and the generator engines, but that’s more for amusement than necessity.
I should point out that the reason I can run such low flue temps without much creosote build up is that I burn very hot and only hardwoods.
Hello Thiago, you can make a heat exchanger from a rectangular pipe, there are different dimensions, for example, if you choose a 90x30 pipe, you can install two rows of TEGs, so the wires are facing outwards and the connection will be easy, on a 1m length of such a pipe you can install 60 elements. Of course, it is necessary to close the ends of the pipe and make water connections, you can from the opposite direction this connecting pipe reaches the opposite end, this will create a “labyrinth” and you will get a fairly even temperature on the surface. Iron pipes are easy to weld, and the heat conductivity is good because here only 2 or 3 mm of metal separates the water and TEG.
Thank you for your suggestion. I was wondering about using this plus another small “box” with PCM materials. There is one that melts at 90 degrees (Celsius) and then it stays even. Anyway, I will keep my studies and I will keep things in this post. Unfortunately I’m not having much free time at the moment. But hopefully by end of summer I I’ll have a proper plan to execute during autumn and test it during winter.
