It is a nice idea, but not all that practical - you almost have to get (or build) a dedicated generator set to do this with. For openers, the engine has to hold 1800 or 3600 RPM, so the generator holds 60 Hz fairly closely - many electronic devices do NOT do well when the power input takes major voltage or frequency excursions. And that takes a purpose designed governo r system on the engine to apply throttle as necessary to hold the prime mover running speed in a very narrow range.
There is an an air-vane governor in the average lawnmower engine, but it is a very rough control meant to deal with hitting a patch of extra heavy or wet grass without stalling the engine - and then not overspeeding the engin e past the safe redline when your grass is all cut. It will allow several hundred RPM of speed variation before reacting, when you want to stay withi n
5 to 10 RPM of ideal.They DO Make Tractor PTO operated generator sets that take the 540 RPM PTO Shaft output, wind it up to 1800 RPM with a step-up gearbox, and use a
4-pole alternator. But the average farm tractor also has a fairly sensitiv e engine governor built in, and will hold the speed for 60 Hz power generatio n tight enough for most uses. And you just took the tractor out of service a s a tractor for use on generator duty when you might need it most as a tracto r- like digging yourself out of the Blizzard Of The Century.
You can build up a generator set yourself out of a salvaged car engine, but you'll spend a few hundred bucks on the controls and the special governor. Much easier to buy what you need, and just run it every month to keep it i n good shape.
2) As another take on the same residential emergency power backupThey already make Solar inverter systems that can be fairly easily switched over from "Online Utility Tied" to "Offline battery bank with Auto-Start Generator Backup" modes manually with a few switches and a few minutes work , and you can be totally free of the grid. But it has to be manually initiated for safety reasons - the Utility won't let you tie it in directly and automatically without that precaution. You need safety switches betwee n the Utility and your solar system, and manual Lockout/Tagout procedures so there's no way you can backfeed power toward the Utility and shock a few unsuspecting linemen...
One of them that I have researched is the Sunny Island series from Sunny Boy, I'm certain there are others. And they do cost quite a bit more than a purely Online system from what I'm told, plus buying the bank of Lead-Acid storage batteries it will need to run with is a non-trivial cost - you need several hundred to a few thousand amp-hours of tank-cell batteries at 48V nominal. (Gee, a 26-cell string, just like a telephone Central Office...)
Not to mention building a sturdy battery rack (seismically reinforced where necessary) and isolating it from children and pets in a dedicated and secured room for safety - that's a lot of Sulfuric Acid. You would need to partition off one side of the garage for the battery room, or fill half the basement if you have one.
If you live somewhere that the utility power grid isn't all that reliable, it would make sense to spend the money and upgrade.
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