Using inverters for emergency power

Instapundit ^ | November 8, 2012 | Glenn Reynolds at 6:07 pm

[JDoutrider]

mark

[Ole Okie]

They beat trying to store ice form a lake all season.

Back in my youth, you just put the ice card in the window and viola! Some guy driving an ice truck would bring ice in and put it in the ice box whether you were home or not.

Beat trying to harvest that lake ice.

[PA Engineer]

Watts are a measure of the rate of energy consumption. Watts are how much energy you are using RIGHT NOW. If you use a watt for an hour, you have used a watt-hour. Maybe you have calculated how many watt-hours you use per day. But you can’t possibly calculate how many watts you use per day.

Your post reminded me of something. Every one should get a P3 International P4400 Kill A Watt Electricity Usage Monitor.



They are cheap at $17.84 and will help to design daily load calculations. Load calculations also need to take into account charger efficiency, inverter efficiency and generator efficiency. These efficiencies are all cumulative.

Just assume your average gasoline generator converts 16% of energy in a gallon of gasoline to electricity (many cheap units will only do 13%). Available energy in a gallon of gasoline ranges from 114,000 to 125,000 btus. BTUs per watt hour is 3.41 roughly. This gives you: 120,000 X .16 ÷ 3.41 = 5630 watt hours per gallon of gasoline. There are 1800rpm units that attain 19% efficiency and are much more expensive.

Now charger efficiencies need to be taken into account. At best we can use 85% because of numerous different device and charge level factors. This maybe a bit optimistic, but what I have calculated with my Trace Inverters. We now take the 5630 watt hours per gallon of gasoline and multiply it times the the charger efficiency. 5630 X .85 = 4785.5 watts.

Finally we have the inverter losses (or efficiency) to take into account. I chose my inverters for their very high efficiency ratings. Most cheap units will perform much lower. The Trace DR series run about 93% efficient, while many of the cheaper units will do 75%. For calculations I will use the Trace units. We now take the 4785.5 X .93 = 4450 watt hours of useful electricity.

This can be tweaked a bit with inverters that have pass through circuits while charging. You can take you heavy loads, such as laundry and do them during the charging period to bypass the storage and inverter losses. This is how I have been able to approach 5KWH per day critical loads or about 1 gallon of fuel.

I just wanted to throw this out there. These are rough calculations, but will help to understand and plan for fuel storage during power outages. The watt hour meter is also helpful in determining what your critical load usage is. It may be worth the investment for instance in a new higher efficiency refrigerator then storage of more fuel.

[mountainlion]

When I was a kid the old lady across the alley used a crock to put her food in and covered it with a damp cloth.

Looks like we are headed back to that.

[familyop]

"ping of possible interest...Using inverters for emergency power"

Thank you, Tainan. Sorry I'm late. [Medieval familyop cao taos and begs forgiveness.] ;-)

I agree with some who wrote that using inverters that plug into cigarette lighters might not be the best way to go for the aftermath of a weather disaster. Vehicles use much fuel, and high wattage inverters plugged into cigarette lighters could damage vehicles. A small generator would be a better way to go for that kind of setup. Then there are small PV solar plants.

There's the low cost Harbor Freight 45 watt "solar panel kit," which requires nearly no previous study (modules, controller--batteries and inverter not included). For those willing to learn more and build more powerful small systems, here are the names of a few low-cost components for a PV solar plant.

Kyocera KD140GX series 140 Watt, 12 Volt Solar Modules (12 volt, very efficient, very versatile, well built and shippable by UPS, if vendor will ship that way).

Morningstar SunSaver 15 Amp MPPT Solar Charge Controller (great for stand-alone installations of chest type DC freezers or refrigerators, e.g., the Sundanzer).

MidNite Classic Solar controllers for larger systems--greatest on earth for the cost, IMO.

Xantrex PROWatt SW series 600-2000 watt true sign wave inverters - very low cost and tough for small sign wave inverters. I've used one of those for over a couple of years. Found those by way of a tip from some yachting folks.

Study, study, study. Use the Net. It's well worth it and can be fun. For RV or non-RV home installations, learn basic electrical work--also very rewarding. Get a copy of the NEC (National Electrical Code, essential for home installations)--not all that hard, once you get the hang of it. And safety first! Memorize all of the safety stuff first, and practice it at every practical opportunity afterward.

Switch off and lock out circuits before touching anything. Read the extra precautions on PV solar modules (panels). They can cause deadly shocks. So can anything connected to them. 12-volt Batteries can also be dangerous without proper education and precautions. There's much around the Net about solar battery installation, care and precautions. Install disconnect switches for every component.

And remember: if the "end of the world" arrives (little humor there), the technically inclined will rule afterwards (serious about that part). So be kind to tinkering redneck neighbors with junk in their yards. Many of them are more skilled than most non-technically-inclined people realize. ;-)

[Disclaimer: I don't really have junk in my yard. Heh.]