Hmm... Yeah, I think I can see the basic concept you're getting at. I just don't know if it would be worth all the trouble.
Another side effect of powering down the Peltiers when off-cycle comes from the idea that they aren't exactly quick about 'setting up'.
It takes a little bit to get the temp of the cold side heatsink down after initial power application. So, for whatever length of time it takes to get the sink down below the temp of the cooled chamber, it will be depositing heat into the chamber until the point of thermal equilibrium (and subsequently reversal) is reached.
This might take a good percentage of the energy that would have otherwise just have been used in maintaining the differential.
Thermodynamics is a ^#$@&, I know. LOL
I'm piecing the big picture together as I go, and so far, it's falling into place why Peltier is not more commonplace as a heat pump.
I'm pursuing it really only for a few reasons. One, and this is big, no moving parts to wear out. Two, no noise. Third, power conversion losses would be less (thinking in terms of comparing running a compressor from an inverter vs directly driving the Peltiers).
Problem is, it's already a very close call, if it even
is possible to do the job with less energy than a compressor uses. But that's what I'm here to try and find out.
One of the first things I intend on doing when I receive the modules is taking one of them, and temporarily mounting the hot side on a heatsink, and leaving the other side exposed.
I'll get (at least) two useful pieces of info out of this:
First, I'm going to find out what the absolute bare minimum power requirements are to get various temperature differences, then plot the results. There will be a knee somewhere in the curve, and that is roughly the butter zone for the most efficient active cooling.
The other, is to find out where the lowest possible power input begins to have an effect. I have a theory that I haven't really been able to confirm just yet; Once they begin to pump heat, they seem to resist heat flow better from the opposite direction. In other words, they may be able to provide active insulation (at least for themselves) from the outside temperature with even less power than what it takes to just
maintain the temperature. If I am correct, and the relationship is non-linear, small changes of a few degrees in temperature on the outside would not readily propagate to the inside through the module. With passive insulation, there is strictly a linear relationship between temperature difference and rate of transfer.
The effect of this would be that even though they may end up being less than useful for active cooling (or even maintenance), if they can provide active
insulation for the entire box for much less power than I am even seeing for maintenance, this is still very much so doable. They would need to be spread out, so we've gone full circle on that again as well...
I apologize for the 'bipolar/circular' tendency of this entire thread. Lots of variables, lots of thinking on paper, and lots of theory. I fear the zig-zagging won't stop until I can physically try some of my thoughts in real application.
Steve