Use of Modified Sine Wave Inverter During and Emergency - strategy?

In article , snipped-for-privacy@yy.zz mentioned...

I think you might get better answers on the ng alt.solar.photovoltaic, where many people have experience with this kind of problem.

First off, there's nothing saying you can't just use bags of ice in the fridge in an emergency, to keep it cool for a long time. The 45 min cycling isn't going to help because the fridge will run for however long it takes to do the job, which may be shorter than 45 mins. Then you ask us to answer potentially liable questions about your fridge, and you don't even tell us the make and model. I say go for it, plug it in and run it for a day, and see how it works. If it burns out, you have a good excuse to buy a new one that will work okay. :-P

A lady at work replaced her old fridge with a new energy efficient one, and saved fifty bucks a month on electricity bills. Really!

So, plug the cheap fan in and see if it overheats. A lot cheaper to replace than the fridge! But you don't really need an inverter for lamps and fans, which can be the types that run directly off 12VDC. Same with the laptop. The microwave? Just put it in the gas oven and heat it up!

Sometimes I think we should all be a little less dependent on electricity. :-/

BTW, nothing wrong with a Coleman lantern. Except it has some radioactive thorium in the mantle, so don't sleep on it, or you'll start glowing too! Does anyone know why this is so? Regular incandescent lamps have tungsten filaments, how come they're not radioactive too? What does the mantle have that an incandescent lamp doesn't have? Maybe I should check out How Things Work or something..

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Tungsten is not thorium. And the gas mantles use the oxide, not the metal. Interesting stuff, these mantles. You want them to run white hot, and have some strength as well. A quick google leads me to believe they are fabric (which burns away of course) impregnated with cerium (1%) and thorium oxide (99%).

In any case they are now available 'thorium free'. See

It seems Yttrium is the replacement. See

Thomas

You may not be able to run the refrigerator at all, because of the high starting current of some motors (several times the running current). You might consider one of the thermoelectric (Peltier junction) coolers as your emergency refrigerator, as they run directly off 12 volts.

Unless you have a very large battery, or plan to run the car's engine a lot, you won't get much run-time. A typical car battery may be rated at 60 or 80 amp/hours which is the amount of power it can deliver at a low drain (20 [?] hour rate). The available power is less at higher discharge rates. A battery that can deliver 3 amps for 20 hours (60 amp/hours) can't deliver 60 amps for 1 hour even though the math appears the same, because of the underlying chemical processes.

Back-of-an-envelope math

400 watt microwave is perhaps 70% efficient, thus requiring 400/.7=571 watts input Inverter is perhaps 80% efficient, thus 571 watts out requires 571/.8=713 watts in 713 watts/12 volts=60 amps Using the microwave for 12 minutes (0.2 hour) 60*.2=12amp/hours but the actual power usage is probably 1.5 or 2 times higher because of the lower battery efficiency at high current drain. Basically, one frozen dinner will use more than 20% of the battery capacity.

As the current drain increases, the battery terminal voltage decreases because of internal resistance. The inverter may be able to compensate for some battery voltage drop by drawing more current, which will further decrease the battery voltage and its total deliverable power.

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IIRC it is due to the thorium having a useful optical emission spectrum at comparatively low tempetures.

About 40% of tungsten is a radioactive isotope! (This only tells 1/2 the story, the activity is very low).

Gas to survive in an oxidising enviroment when you turn the lamp off and also has to survive in a nasty mixed enviroment when the lamp is operating. Also it runs somewhat cooler then a tungsten source!

Regards, Dan.

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You should be able to find the answers here:

or here:

They sell big inverters and have numerous recommendations about various equipment. Not all of the world has readily available electricity 99.9% of the time - some places rely on sun and wind for all their electricity.

If you read all the linked info, you'll find that the refrigerator will draw about 15% - 20% more power (and thus probably get somewhat hotter) than it would on commercial power. This shouldn't be a problem in intermittent operation. If the room temperature is above 90F, the refrigerator might be running almost continuously, depending on the quality of its insulation.

Before experiencing a long-term outage, put a thermometer on the compressor and see how hot it gets in normal operation. Then connect it to the inverter for an hour or so and see if there is an appreciable difference. If it runs hotter than you would like, consider adding a small fan to provide cooling for the compressor.

Other links of interest:

(search for Conserv)

"Bill" wrote:

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Thanks. I think I have a much better sense of this. I'm surprised inverters are not more popular.

Bill

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Better yet, the fridges they put into RVs, trailers, etc. run off propane. No need for messy batteries, generators, or gasoline.

From what I remember about peltier coolers, they are terribly inefficient, too. They make a lot of heat, which has to go somewhere. So that has to be dealt with. If you use one indoors, then it may heat the place up a lot.

I remember moving those Servel gas fridges in the '70s and they were terribly heavy, probably twice as heavy as an electric. My mom used to make bread and put it on top of the fridge to keep it warm while it did its "rise" thing. I vaguely remember the aroma of that rising bread.

[snip]

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In article , snipped-for-privacy@yyy.yyy mentioned... [snip]

I dunno if you got my previous followup. The fridge itself controls the on-off duty cycle, so trying to control it yourself is probably not going to help. Suppose you let the fridge run by itself. It might run for 15 minutes and then shut off for 30. By unplugging it, you may be forcing it to run longer thus making it get hotter.

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My email address is whitelisted. *All* email sent to it goes directly to the trash unless you add NOSPAM in the Subject: line with other stuff. alondra101 hotmail.com Don't be ripped off by the big book dealers. Go to the URL that will give you a choice and save you money(up to half). You'll be glad you did! Just when you thought you had all this figured out, the gov't changed it:

No. It will probably make the problem worse (if there is one).

After 1 hour off the fridge might need to be on for longer to recover the temp loss. .Let the thermostat in the fridge control the duty cycle.