emergency power system for cooling insulin

[inetdog]

Thanks Inetdog,

I'm not sure what the threshold is for temp variations. I'm sure the pharmaceutical boys know the degradation curves on stuff like that. Less is better obviously. That what the aluminum or copper heatsink idea was for; to moderate any temp spikes and "hold the cold" as long as possible. I was even planning on rolling my own digital thermostat. There's plenty of gadgets on eBay for that.

I've never looked into phase change technology; I'll make it a point to do so. Are we talking something like ammonium nitrate?

I can't say specifically, but I know from seeing commercial products that it is possible to generate a mixture of ingredients with a phase change in the 35 -45 degree F range, just not necessarily water-based.

[spectraThug]

Just interjecting my two cents: I've been impressed by the stats on the Steca line - the PF-166 states it will use only 70 watt/hours per day, keeping the interior at 3C in ambient temperatures of 20C outside; 165 whr/day to lower to 3 from 30, straight draw from 12 or 24 volts.

It's the item I am leaning towards purchasing for the new home.

That would definitely do the trick. Straight DC high efficiency compressor. Add peltier coolers in case the motor gives up (this would take a little work obviously). That cooler + heatsink or phase change material + battery/solar backup would definitely place me firmly in the Department of Redundancy Department. Right where I like to be when it comes to stuff like this.

[Naptown]

Don't be looking for any quantities of Ammonium Nitrate. If a compressor leaks or the casing fails you will have a nice bit of explosives on your hands. Not to mention probably a visit from ATF or FBI

[Sunking]

Spectra when you really want to know how to do this for reasonable cost let me know and I will set your feet back on the ground with something you can actually do and afford.

[Vern Faulkner]

That's what the aluminum or copper heatsink idea was for; to moderate any temp spikes and "hold the cold" as long as possible.

The best substance for "holding the cold," which in more accurate terms, requires the greatest amount of heat energy per unit mass (heat capacity) to increase in temperature is not a metal. Aluminum's heat capacity is .902 J per gram-degree; copper is atrocious at .385.

It's an interesting substance, somewhat problematic to handle because it is a liquid at normal room temperatures, yet is also a solid when chilled. Lovely stuff, with a specific heat of 4.18 J/gC liquid (resisting changes in temperature four times better than aluminum) or 2.03 J/gC when solid (still twice as good for keeping your freezer cold than alumnimum). It's called dihydrogen monoxide, also known as ...

... water.

Freeze a few slightly-less-than-full one-gallon milk jugs of good ol' tapwater. That'll hold the temperature better than any other substance known to science.

[spectraThug]

Don't be looking for any quantities of Ammonium Nitrate. If a compressor leaks or the casing fails you will have a nice bit of explosives on your hands. Not to mention probably a visit from ATF or FBI

@Nap,

No worries, AN is really safe unless you mix with a fuel like diesel and/or aluminum powder and shock it really hard and really fast with a projectile or blasting cap.

[Delnorin]

He lives in AZ, there are no basements in AZ. YOu do not dig in AZ, you drill, jack-hammer or use dynamite.

You are 100% correct on that. I live in AZ also and am working on a much more simple option. Kooltron 28 quart 12 volt dc fridge... 120 volt panel, a 30 amp controller and 1 marine battery. Should be simple/good enough for just the 1 small fridge. I'll add on more later but issue #1 is being sure I can keep my daughter's insulin cold.