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Thermoelectric Freezer Alarm

Use the very thing you're losing to mark it's loss
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During the recent events, a remarkable amount of equipment has failed. I understand how some devices, cars for example, respond badly to disuse. Things like oil seals dry out and let in air/water vapor etc. But while being completely undisturbed, my lab has had 2 computers and 2 freezers fail catastrophically. Computers are trivial to replace, they can often be found lying around in other labs for example, but laboratory freezers often contain things of a totally irreplaceable nature. A single DNA plasmid that took a dedicated scientist 3 months to create? We have >1000 of them. Tissue samples from the only known human family to have mutations in a certain protein? Just the permission paperwork and organization of doctors/patients on the other side of the world through 2 languages & multiple customs inspections remaining carefully frozen is a feat. Replacing them? Well, they're all dead, it's an important protein. Anyhow, let's take a look at how this problem is normally solved.

So, a lab grade -80C freezer is a hefty beast with a price tag roughly the same as a Ferrari with similar running costs and none of the glamour. Because they may contain valuable or dangerous substances, they usually come with an alarm system. This usually consists of a lead-acid battery in the bottom that powers the electronics in the event of a power failure etc. In our case, the electronics sense rising temperature and trigger a relay. This relay is wired into a whole-building alarm system that alerts a dedicated team of staff who has a list of contacts for each freezer.

This system failed. For several reasons. In one case, the alarm triggered the relay did it's thing, the alert went to the building system and... the dedicated staff retired last June. In another case, a purchase order for a new battery was placed only to be cancelled by a senior administrator* because: "freezers running on batteries, I wasn't born yesterday!"

So, maybe it is dumb to rely on a 12V lead acid battery that is doomed to fail. They should be replaced on a schedule, but science grants are costed to the penny on exciting sciencey stuff and noone ever got money for maintenance, calibration, cleaning, or... events. A walk around the floor revealed 6/28 -80C freezers with battery warning lights on. Clearly a widespread problem. A more permanent solution would be useful, so what do we have to work with? Well, a freezer makes a temperature gradient, -80C inside, +20C outside a delta of 100C more or less. That and some insulation is it really. But we can work with it.

The freezer electronics** don't need much power. This is fortunate because thermoelectric generators don't make much. But, enough. So, place a thermoelectric generator, Peltier element, Seebeck device etc, with one side in contact with the interior and one side in contact with the outside. The 100C gradient will be more than enough to power the electronics so that they can do their thing during a power failure. Solid State, no battery required. Should be more reliable.

*Same guy that decided to put 12 freezers in a "freezer farm" for organization and that "freezers make cold, not heat! Why do the HVAC guys need to be involved? We already spent a fortune on all the extra high capacity electrical outlets"

**like microwaves, designed in 1981 and never changed.

bs0u0155, May 28 2020

not this https://www.youtube...watch?v=D76jSwRIivg
a small in-fridge unit might be the way to go. [wjt, May 31 2020, last modified Jun 04 2020]

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       Can you retrofit this to the existing units? For lower cost than securing a contract for preventative maintenance?
kdf, May 28 2020
  

       Retrofit? Probably not. You'd need to cut holes in insulation etc. It's just a thing that could be built-in for a small cost.   

       Preventative maintenance isn't avoidable. -80C freezers build up ice at extraordinary rates, particularly in humid summers. They also have air filters that need to be cleaned. They're something that really should be kept on top of, but, that would have to come from someone's time/budget.
bs0u0155, May 28 2020
  

       I was mainly thinking about preventative maintenance inspections on those batteries. On first read it seemed to me that was the potential point of failure you hoped to replace.   

       Specifically at your site, what will cost more going forward? Getting your senior misadministrator to approve battery replacements when needed, or getting new freezers that include your battery-less sensors/triggers?
kdf, May 28 2020
  

       No problem can't be solved with the proper application of high explosives. Your administrator sounds like a problem to me.
Voice, May 28 2020
  

       //proper application of high explosives// Yes, and judicious use of a shovel.   

       Come to think of it, the shovel is easily acquired, has no moving parts, no traceable serial number, can be used before, during, and after the removal process... a complete job, neat and clean and plausibly deniable, for less than the cost of Big Louie the explosive expert's lunch on the way to erase* the guy.   

       *except there's always DNA spatter
Sgt Teacup, May 28 2020
  

       Thinning the lining of a box that is designed because of insulation doesn't sound sensible. A better retrofitted storage cell, charged off the mains, not unlike UPS would be my suggestion. Now days the newly inserted electronics will probably come with IoT and txt the affected people directly.
wjt, May 31 2020
  

       Widget's got the right direction.   

       I see a lucrative business. If freezers cost as much as a Ferrari you should charge at least as much as a replacement Ferrari component for these. And be sure to give them a sciencey-name for the bean counters to struggle over.
RayfordSteele, Jun 01 2020
  

       //During the recent events, a remarkable amount of equipment has failed.//   

       I blame the installation of 5G towers. I mean, why not?
AusCan531, Jun 03 2020
  

       //Thinning the lining of a box that is designed because of insulation doesn't sound sensible.//   

       In theory, you're right. I am creating a thermal path for heat energy to flow into the interior via the thermoelectric generator. But,thermal conductivity would be small via eg. a 45mmx45mm element.   

       In addition, there already is a hole through the insulation allowing free gas exchange, it's there to equalize pressure. Imagine a freezer full of stuff at -80C, you open the door and rummage around for your stuff** while room temperature air fills the freezer. You shut it and that air is cooled rapidly, the pressure drops and your door is now sealed. So they put a ~30mm hole through the door which means you can open the door and ensures the freezer fills with ice derived from water vapor in the air.   

       So I think you could build the thermoelectric generator into the vent design. Retrofit isn't going to happen, but the hole through the insulation is there to be designed around.   

       //A better retrofitted storage cell, charged off the mains, not unlike UPS would be my suggestion. Now days the newly inserted electronics will probably come with IoT and txt the affected people directly.//   

       The electronics, lead acid battery and alarm relay already function like this. The problem is somewhat institutional, I'm trying to get around the battery failure mode by putting in a solid state backup power supply that uses a large energy source inerrant to the function of the device. It's a bit like a ram air turbine (RAT) on a commercial airliner, if your aircraft has lost both engines, you need SOME electrical energy to give the pilots tools to mitigate the problem. Sure the RAT adds drag and technically worsens the glide ratio - but at that point the altitude & speed are the only available energy resources and they can at least get a radio call out.   

       *Is there a word more appropriate? It's more of a heat collector. **Global academic lab policy stipulates that there should only be one left handed cryo glove available if at all, the rest of the searching should be done with standard nitrile gloves in a race against frostbite and the rapid accumulation of frost over all the labeling that wasn't very good in the first place.
bs0u0155, Jun 03 2020
  

       //I see a lucrative business. If freezers cost as much as a Ferrari you should charge at least as much as a replacement Ferrari component for these. And be sure to give them a sciencey-name for the bean counters to struggle over.//   

       No-one usually questions big purchases. It would be nice if the layers of admin were in any way connected to some sort of performance indicator, but that's tricky in science. It's a strangely inverted power/responsibility dynamic where admin controls the people who deliver science and obtain the money to pay everyone and organize/maintain everything in between.
bs0u0155, Jun 03 2020
  

       BTW the old school back up method for power/compressor failure was a temp sensitive valve that opened allowing fairly rapid release of CO2 from an attached cylinder.   

       These aren't popular anymore, no-one likes paying for the cylinder rental, the CO2 cylinder probably gets used for an incubator emergency and not replaced, and the whole system probably buys you a few hours.
bs0u0155, Jun 03 2020
  

       Peltier junctions constructed as a layered mesh, in the 30 mm radius-ed cylinder form factor, might be a retrofit. Letting air in but still riding off heat entry.
wjt, Jun 04 2020
  
      
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