06 Jan. 2009
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PriUPS Project

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Arguing Over PriUPS

New Old Years

Paul and Deb substituted their relentlessly cheerful years pursuant to my invitation.  If you had a year of the better-than-blah persuasion, it's not too late to add it.

A Few Arguments About PriUPS

Every once in a while the mainstream press catches on to the fact that a Prius can be used for emergency power.  Although there have been a number of press reports on my specific project, it so happens that New York Times reporter Kate Galbraith picked up and blogged on an article in the Harvard Press about one John Sweeney, who

took a characteristically green approach to powering his home during the storm. He reported his achievement in an e-mail, saying it was no big deal, but that his wife thought it an impressive tale worth sharing: Sweeney ran his refrigerator, freezer, TV, woodstove fan, and several lights through his Prius, for three days, on roughly five gallons of gas.

“When it looked like we were going to be without power for awhile, I dug out an inverter (which takes 12v DC and creates 120v AC from it) and wired it into our Prius…These inverters are available for about $100 many places online,” he wrote.

The device allowed the engine to run every half hour, automatically charging the car battery and indirectly supplying the required power.

Several people pointed me to the Times article, and I added my own comment in the place provided.  But two things struck me about this event of reportage besides (boo-hoo) the failure to mention my PriUPS site.  The first was that the subject of the article didn't do anything that millions of others haven't done alreadyhe connected an inverter to the 12V power system that's present in every car, and got 120VAC power from it.  The other, more significantly, was the welter of comments this short blogitem in the Times accumulated.  Mine, posted the same day the article was published, turned out to be #75!  As of today, two weeks later, there are a total of 158 comments.  Not only was the quantity unusual, but the quality, at least of the sane posts, was unusually good, with many thoughtful respondents arguing the concept's pros and cons. 

I rarely engage in actual arguments over the merits of my PriUPS system.  The fact that I have electricity when the utility isn't providing it is enough for me.  But people coming to it for the first time often don't "get it" and come up with some really silly arguments.  Of course there are good arguments as well, and the comments in the Times included some of them.  For that reason, I thought I would, Snopes-like, spend a blogitem covering some of the reasons why using your Prius to power your house is (or isn't) a good idea.  (For the other reason:  It will save me a lot of writing in the future when people have comments and questions, and if someone comes up with a new one I shall add it to the end.) 

New York Times Green Blog About Prius Power:  Comments, Discussion, Arguments

Argument/Comment Status Discussion
yessss.. let us start thinking creatively again. and give science the respect that it deserves.— torontonian
True! Amen.
Well, you sure got my attention as the owner of a hybrid Camry. I’ve not heard of such an inverter before. Can you share the source for this marvelous device so I could purchase one and have it in hand in case of a similar emergency?— Neil
Q! Standard 12VDC to 120VAC inverters are available "everywhere."  Auto supply shops are a good source.  High-power inverters are much more expensive and harder to find, but eBay often has incredible bargains.
You can buy a real emergency generator for a modest sum. Next question….— el Rey
True! Here's a comparison.  More, much more, later...
The part about this story that caught my attention is the fridge: Isn’t it silly that we need to consume electricity to chill our refrigerators when it’s freezing cold outside...— Evan True! Not quite that simple, but certainly true in part.  One of the intelligent comments, but off topic, so I'll drop it.
Couldn’t you do this with ANY car if you had a dc/ac inverter? All cars generate 12v dc current. What’s the advantage of a hybrid in this situation?— Jack Davey
True.. but! But:  The Prius is MUCH more efficient.  For one thing, the gas engine doesn't run all the time.  For another, it's much more efficient when it is running.
I suppose the next thing you’ll be trying to tell us is that there’s energy in the “wind” and the “sun” and that we can “harness” this magical energy. –Dick Cheney — osisbs
Hmm. Did I mention that a lot of the comments were intelligent?
The overall efficiency of an automotive gas engine is about 20 percent. The overall efficiency of a power plant is about 40 percent.
Charging a smart grid via hybrid cars would waste a lot more fuel and dump a lot more carbon into the atmosphere, but the important part (the symbolism and CHANGE) overrules reality, as usual.— A. Gondring
This is a "straw man" argument.  Nobody is realistically suggesting using hybrid cars to "charge the grid."  Certainly big power plants, especially nuclear and alternative energy plants, produce less carbon than millions of car engines.  The "V2G" concept is to allow hybrids to provide occasional, peak power needs.  Which is more efficient than having to build and operate more power plants.
The reporters of this story apparently never talked to an electrician before reporting this. What this guy did (and yes any 12 v. DC supply inverted to AC can do it) is “back feed” the electrical grid. This can get a utility worker killed.
Unless you really know what you’re doing don’t try this.— Whiskey Tango Foxtrot
Yes, you can kill utility workers if you feed power to a section of the grid they are working on that they assume is unpowered.

No, the article never suggested the inverter was feeding the grid.

Yes, unless you really know what you're doing, don't try this!

The amount of current a car battery can generate is trivial compared to what one needs in a home. The electrical appliances able to use automibile current are quite few in number. However, my hybrid has a household current plug (120V). That’s the advantage of a hybrid!— Ken
A car battery/inverter can supply about a kW.  A PriUPS system about 3kW.  A lot more, true, but 1kW isn't "trivial." 

Some hybrids, e.g., the Ford Escape, do have 120V outlets.  But the Ford's, for instance, is only rated at 150W.

Please caution your readers that running the “Prius” in an enclosed area like a garage, or any form of combustion, even with an engine as efficient as the “Prius”, still creates carbon monoxide gas that has been known to seep into the house when not ventilated properly.— Duartean
Small portable generators are excellent carbon monoxide generators, even outdoors.  See, for example this excerpt from Science News.

The Prius, I'm sure, generates some CO.  But my meter measured it to be "zero."

Wow!  That's just the first page (out of seven) of excerpted comments.  Let me get this on the web and I'll finish up later.
The issue of power depends to a great extent on the wires coming from the battery. For 1.2 kW output the inverter draws 100 A from a 12V battery and gauge 4 or so short wires are necessary lest you want to turn the battery power into heat.
Definitely a solution to consider, relatively easy to implement and not that expensive.— Ladislav Nemec CA
True! In my project I used welding cables.  When drawing power from the 12V battery it's even more important to use thick wires, since the relative voltage drop from 12V is a greater percentage than the drop from 220V.
Everyone quick go out and by a Toyota and help them and their government kill more whales.
Maybe Japan and Toyota can come out with whales skin seats on their autos.— Larry
??? Whale skin seats are terrible in hot weather since they're waterproof.  (How did he get the Times?)
A “smart grid” connection will sense when the power is back on from the grid and do an auto disconnect.— R. Frazier
True! But try to find an inverter that both does this and also will run without a grid connection.
It is not the battery that is providing the power in this case but the gasoline engine. The battery just makes it a little more effecient but if this was a practical means we would all have been powering our houses with our cars long ago.— Stardreamer
True! Something worth remembering if you get too enthusiastic.
The only battery the Prius has that is charged by the engine is the small starting battery. That battery wouldn’t run all those appliances mentioned. The big batteries are charged by the wheels “coasting”. The wheels obviously weren’t in motion when the Prius was being used as a generator.
— Collier Perry
False! Very, very fortunately untrue.  The gasoline engine charges the big battery even when the car isn't moving.  (If it didn't, every traffic jam would result in a Prius-logged disaster.)

I think he's right about "wouldn't run all those appliances mentioned."  Certainly not all at once!

I’ve used my Prius this way. The advantages are that 1) it’s quiet, 2) it’s always ready to go, 3) you don’t have to own and maintain yet another small gas engine, 4) the ten gallon gas tank lasts a long time. The quietness is the biggest advantage. The car just idles the engine for a few minutes every hour, depending on the load. After I used my Prius as a generator once, I gave away my stand-alone generator. Who needs the noise?— Christopher Hogan
True! A tron after my own spleen!  The rest of his lengthy comment is well worth reading.
Of course, when you lose your home to foreclosure, the technical aspects of hooking into the smart grid won’t matter as much, since you’ll be living in your Prius. Refrigeration won’t matter much either when your primary “fine dining” is beef jerky.  Jetsons? Ha!— Greg
False! At least I hope it is...  I'd like to think that Prius owners have saved so much on gasoline that they can afford to pay their mortgage.
For now, and as correctly mentioned earlier, stationary natgas and propane emergency generators with automatic transfer switches have reached a very reasonable price point, and should be a top consideration for any homeowner looking for energy security.- gtr
True! I am enthusiastic about PriUPS, but not dogmatic.  Although there are good arguments for using the Prius, there are also good arguments for a true emergency generator.  You're not going to go out and buy a Prius just for this project.  (Unless you're me.)
You could use a regular car to generate electricity only while it is running. When you shut it off that inverter load will discharge your battery and make it impossible to restart the car.
I suppose the Prius somehow avoids this small problem?— Bob Morley
True! Of course he's correct.  So don't shut it off!
Hmmmmm…. if a Prius can cycle on and off when the battery needs a charge… what if you drive it into your garage with battery power and forget to remove the key… and it kicks in in the middle of the night and kills your whole family? I guess this will happen as the number of hybrids increases.— Ochsucker
False! But good thinking nonetheless.  The duty cycle of the Prius is much more frequent.  It's unlikely to go as much as an hour without starting.  Even so, and even though this can happen regardless of whether you're using it for power, the Prius emits very little CO and is unlikely to be a threat except under extraordinary circumstances.
I bought an inverter at WalMart for $17 that ran my computer, TV and internet during the 6 days of power outage from the recent ice storm. (I put the food from the refrigerator outside in the cold.)
You can learn about these things, folks. It’s not hard. An hour at the library or on a FACTUAL part of the internet (not comments or blogs) will give you some tools for living. And some self-esteem. Or would you rather rest your brain and watch Wheel of Fortune?— Tom o’Bedlam
I can tell when it's time to end this blogitem. If I can't, Mr. o'Bedlam is here to help.

I will confess to occasionally (but never deliberately) watching Meredith Vieira and Millionaire.

<IRONY>My next crusade will be to ask everyone who puts anything on the internet to label it <FACT> or <FICTION>.</IRONY>

You can read the rest of the comments yourself, but they're getting largely duplicative.

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