Thermoelectric generator - candle and cold water

[TinselKoala]

TK likes this.
Two thumbs up!

[conradelektro]

TinselKoala & Pirate88179: thank you for the encouragement.

Magluvin: thank you for the good information (camp fire charges, aluminium boxes). I hoped to get feedback by creating a thread, and in come the great ideas. There are so many things out there which one can learn.

Efficiency: I read that NASA achieves about 7% efficiency in the latest Mars rover (2000 Watt of heat from the plutonium, about 150 Watt electricity out from the thermocouples) http://solarsystem.nasa.gov/rps/rtg.cfm . The easily available elements reach about 4%.

From this web site http://thermalforce.de/de/download/index.php?uid=f06c1126a7b53e606196e78a328e41e9&ref= (sorry, most of it in German) I learned a lot.

For electricity generation one wants a high temperature difference (100° or 200° centigrades difference), that really boosts the output (to near 4% efficiency). One also has to assure a good heat transfer from the Peltier element to the cooler/heater and they sell a lot of glues and pastes for that http://thermalforce.de/de/product/waermeleitmittel_zubehoer/index.php?uid=f06c1126a7b53e606196e78a328e41e9&ref= (again in German). I am not a sales person for this German firm but I am so happy to have found a source that sells one or two items to me.

May be some one knows US sources and info in English.

All winter from September to May I often light two tiled stoves in my house (kitchen and living room) because it creates a very comfortable atmosphere. And I want to combine this habit with a battery charger (during the day) or a lamp (in the evening) based on Peltier elements. Nothing new, but I want to come up with a simple and practical set up.

See the attached drawing for a principal lay out. The cold water container should be mounted on the outside of the house (the stove is on the inside of the wall) and two pipes lead to the heat exchanger at the Peltier elements (which are basically glued to the stove). One pipe feeds the cold water and the other returns the slightly warmer water (after it went through the heat exchanger) back to the cold water reservoir. If set up in the right way convection should start by itself.

In the sixties all water heating systems (with radiators in each room and a burner in the basement) were build to self convect. Nowadays one uses an electric pump to move the water through the pipes and the radiators because that allows for more freedom when installing the pipes and the radiators around the house.

All this is of course not new and probably not OU (but will be patented to make me rich, all rights reserved). My wish is to come up with a system that is easy to install and with commonly found (and hopefully low cost) components (besides the Peltier elements which cost about 50.-- Euros a piece). I also do not want to destroy my house or to install a really awful looking contraption. But sacrifices have to be made in order to advance science.

Greetings, Conrad

[conradelektro]

Here the camp fire charger mentioned by Magluvin (I like it):

http://www.youtube.com/watch?v=J2rA9XK_6wI (unboxing video)

http://biolitestove.com/campstove/camp-overview/features/ (2 Watt at 5 Volt)

http://biolitestove.com/homestove/overview/


Here a rather complicated description of a cooling system with two flower pots, sand, water and a paper kitchen towel:

http://www.ehow.com/how_7504579_diy-water-cooling-system.html


Greetings, Conrad

[TinselKoala]

Can these Peltier elements be completely submerged in oil? If so that would really help with the heat transfer, going in either direction. A non-pumped, convective flow of oil submerges the element and a high-efficiency heat exchanger interfaces with the environment or outside heat source/sink.
One side of the Peltier module is contacting (submerged in) one sealed oil chamber and ditto the other side of the module, one side hot, the other side cold.

[conradelektro]

Can these Peltier elements be completely submerged in oil? If so that would really help with the heat transfer, going in either direction. A non-pumped, convective flow of oil submerges the element and a high-efficiency heat exchanger interfaces with the environment or outside heat source/sink.
One side of the Peltier module is contacting (submerged in) one sealed oil chamber and ditto the other side of the module, one side hot, the other side cold.

The Peltier elements I have consist of two thin ceramic plates (non conducting) and the thermo coupled metals are sandwiched in between. Additionally there are two wires leading out from in between the ceramic plates. (See the Peltier element in the attached photo montage.)

The ceramic plates could each be a wall of a container, one container with hot liquid and the other with cold liquid. One needs a good glue (heat resisting glue for the hot side) and a suitable design / geometry of the containers.

I kind of go half there with may next design. I use a 110 mm diameter evacuation tube (PVC) with an end cap at the bottom as a cold water container. The end cap carries an aluminium plate with holes. And the cold ceramic plates of two Peltier elements will be glued over the holes. The cold water will be able to reach the aluminium plate but also the ceramic plates through the holes.

One wants the cold ceramic plate at the bottom of a cold liquid container, because the liquid which becomes a little warmer will rise being replace by the coldest liquid in the container by natural convection.

One wants the hot ceramic plate at the top of a hot liquid container, because the liquid which becomes a little colder will sink being replaced by the hottest liquid in the container by natural convection.

But in my next build I will only use the cold water container (with two cold ceramic plates at the bottom) and a candle to heat the two hot ceramic plates (two Peltier elements next to each other). In order to distribute the heat from the candle flame more evenly I will use an aluminium plate glued to the hot ceramic plates. (See the photos and the drawing in the attached photo montage.)

Greetings, Conrad

(I will travel for a week, therefore no more progress for at least a week.)