In our last blog we discussed the issues and benefits of using air to cool the cold side (heat removal side) of the TEG Generator System. In this Chapter we will discuss the characteristics around using air and liquid and why liquid cooling is far superior to air cooling with minimal draw backs.
The basic differences between Liquid and air are for the most part self evident. Air is an insulator and liquid is a conductor. This fact alone solidifies liquid as the best means of removing heat from the cold side and in doing so allows a liquid cold side to sustain a very large DT even with an elevated ambient (room temperature). Liquid in fact is able to remove 1500 times more heat as compared to an average air heat sink with fan wood stove thermoelectric generator. A properly designed liquid sink with good turbulent flow and liquid that covers the same square area as the TEG modules will not only create an ideal design for maximum thermoelectic power output and exploit the full potential of the rated output of the Thermoelectric modules, but will also forgive the owner from having to run his or her wood stove at elevated temperatures to provide maximum DT.
Case and point
You have 2 Thermoelectric Wood Stove Generators. Both are designed with 10 modules. Each module is rated at 5 watt at maximum potential DT. The AIR TEG Generator with heat sinks and fan can only remove about 50% of the Heat Flux generated by each module. Reasons include elevated room temperature; air physically is a poor medium for removing heat (insulator). The heat sinks are limited in the ability of transferring heat flow from the modules source to the outer area of the heat sinks where the fan can blow the heat away (surface area of the heat sinks). A heat dam is created so the cold side heats up limiting heat flux movement (FLOW) so the modules can only produce about half of the rated output (ie. 25 watts).
The liquid unit on the other hand uses a conductor which is liquid. The liquid is moving, churning, picking up almost all the heat moving thru the modules so DT is sustained and taking the heat away very quickly to a dumping area far away from the heat source (outside) where it could possibly, be below freezing, dumping almost the entire amount of heat the was absorbed from the TEG Generator and returning that liquid at a very low temperature back to the wood stove TEG generator allowing for more heat to be picked up with almost no compression of DT. Resulting in a TEG Generator with power output of 45 to 50 watts. Twice the power performance of the air unit!!
- Liquid units take more time to set up and need to be monitored more closely, but with a good reservoir to feed the TEG. Overheating can be avoided.
- They typically cost more as the design cost more to produce.
- You have tubes running from your wood stove Thermoelectric Generator.
- Even though a pump is used our pumps are so quite you will not know they are running and run with very little power draw!
- Liquid can be used in a hydronic loop that could heat a room on the other side of the house.
- Because maximum DT is sustained the wood stove can run at lower temperatures and still produce good power!
- Power output is more constant as you do not have to worry about the room temperature heating up your cold side.
- Lastly, you could dump the heat into a reservoir to use as hot water for house hold use as long as the temperature is above 50˚C (roughly 145˚F) to avoid legionnaire’s disease.