As I like to play around with teknical devices I was fascinated by peltier elements too. Started with a plan for CPU cooling - wanted a silent high performance machine.
To make a long story short: If not manufactured by specialists and priced for military use then these peltiers are plain shit. I would not trust them for 10 minutes if running on more than 50% performance. The reachable temperature difference maybe 40°C if you stage them you soon will need ya own power plant to feed and a little river to cool them. As UEMURA said: the machinery needed to make them work only a little bit is enourmous and will fail by Murphy´s law.
A nice idea - but no way. Forget it.
The magnetic cooling is just the same.
New/old ways that work are: for cooling down to -70°C and if you have an supply of pressured air: the "Wirbelrohr", aka "vortex tube" aka "Ranque-Hilsch Resonator". Quite noisy if not properly insulated, but ya need only an compressor. No moving parts at all. How it works? Answer the question and get the Nobel-Price..... (this is no joke!)
The "Stirling-Engine" is perhaps the best cooling/heating device known. Reachable temperatures are at 2,5°K if staged. Used in gas liquidification by industry and science. Not quite cheap but if you count all costs of peltiers this might be cheaper. Stirlings are the HIT! One side cold the other hot, I believe a well buildt midrange Stirling would satisfy all laboratory needs and more. Like ice for your cocktails.
Peltier - an expensive way for loosing faith in HighTek
ORGY
"I hope I'm becoming more eccentric. More room, you know.
More room in the brain."