Just so we're on the same page, you have observed polarities when you put them in series , haven't you???

 

Is there any way around this issue. Since my power output from the 3108 is constently flucutating, is there some other type of regulator I could use in order to sustain just 400mV or at best 1V?

What I really want to accomplish is taking a TEG and regulate its voltage, thats what my project has basically turned into. Because If i can obtain a constant output I can harvest that energy or hopefully raise the current using ohms law. Because as of right now ohms law cant come into play beause I dont have a constant power output.

No there is no way around this issue. Thermal electric generators work by using the temperature differential between the two sides. If there is no sustained temperature differential there is no sustained electrical output. It's the same concept of a battery. If there is no voltage differential between the + and - connections there is no available power to use.


Some years ago I made a simple TEG demonstrator for a local elementary schools science class. It used one 12 volt 20 watt peltier cooler from an old computer and two heat sinks. The smaller black anodized heatsink went in a pan of hot water and the larger unanodized aluminum heatsink held a handful of crushed ice or snow. As long as the pan of water was hot and the ice was melting the TEG would put out about 1.5 volts at up to an amp or roughly the equivalent output power as a common D battery.

Do you follow the concept now of how a TEG unit works? No temperature differential between the sides equals no power output. Big temperature differential between the sides equals bigger power output.

I bet that if you put an ice cube on one side of your TEG module and your hand on the other you could get your stable 5 volt output from just the first voltage converter unit until the ice cube melted or your hand got too cold.