Originally Posted by marinosr
I'm really surprised that a Peltier device can pull that off. Mind you, the max temp difference between ambient and a carboy is 20F, so your house would have to be quite cold to be able to lager in a carboy. I wonder why a bucket is so much more efficient (max 35F difference)... the mass and high specific heat of the glass?
I'm very suspicious of their energy use claims though. For instance, why do their calculations assume the same duty cycle for their device and a freezer? If you're trying to cool to the rated maximum with the Peltier device (which is the only reasonable assumption given that it can only drop the temp 35F max) I would expect the duty cycle to be much higher than 25% Also, they don't include the 10W idle draw in their calculations, which would add another 65.7 kwh per year to the energy bill. Seems to me they're massaging the numbers.
Good observations. The thermal difference is only part of the equation. The more important cooling capacity is not given, iow, how many BTUs can be drawn/transported per hour.
The buckets are cooled with 2 rods, the carboy only with one. Hence the reduced cooling capacity.
Also, I can stick 4 carboys or buckets in a freezer all being cooled at the same time for the same cost, alas all at the same temperature.
Although there are some questions, no real world tests yet, and the price is steep, their product does have a lot of merit, relying on the Peltier element's capacity, heavy insulation jackets, small footprint, customizability, and portability.