Electronics > Mechanical & Automation Engineering

I’m toying with the idea of a car engine + generator for power backup

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Jester:
Our power here is pretty reliable, that being said if it goes down during the winter, not so pleasant that happened a few years ago during a nasty ice storm, no power for about 2-3 days, I’m glad we had a conventional fireplace.

I’m pretty comfortable with auto engines as one of my hobbies is auto racing so I have assembled and disassembled plenty of engines etc.

 I have a cheap 7kW generator (Neighbour gave it to me in broken state and I fixed it), however the thing is really loud when under load. Honda makes some really quiet small generators and some sort of quiet mid size generators, but they are fairly expensive and not really quiet.

My thought of the day is to pickup a used small engine from a wrecked econo-box car perhaps 1.5 litre and mate it to a suitable generator something about 20-30kW (will depend on what is available used and cheap). I will need some sort of gear box to increase speed to generator perhaps 2:1 or  2.5:1 would allow the engine to run at about  1500 rpm. Will need to make some sort of speed control to keep the generator at 3600 rpm as load changes.

If I re-use the original exhaust and plumb it up say 8’ and away from the house I would think that it would be near  in-audible from the house. I would mount this contraption in the smallest metal shed I can find on craigslist and about 100’ from the house.

Wacky idea or fun project what do you think?

Keep in mind I’m retired and enjoy pet projects.

jpanhalt:
Here in Amish counties, that is quite commonly done.  Many people believe Amish won't use electricity as it is evil or something.  That is not so.  The prohibition is against using electrical power from public power lines.  Many of their industries generate electricity on site.  As one example, they are well known for work with canvas materials for tents/boat covers/etc.  Sewing machines don't run on diesel or horses.  Those enterprises generate on site.  Woodworking is another example.

I don't have access to any of those plans, but it is certainly not a crazy idea.  An old 4-cylinder, air-cooled VW engine might be simple.  Meeting pollution restrictions might be a problem.  Small diesels (Kubota, Yanmar, others) are another possibility, but will likely be more expensive than a used automotive engine.  Riding mower engines  (e.g., Kohler 25 HP) do not have a very good record for longevity. 

tpowell1830:

--- Quote from: Jester on December 06, 2021, 06:27:07 pm ---Our power here is pretty reliable, that being said if it goes down during the winter, not so pleasant that happened a few years ago during a nasty ice storm, no power for about 2-3 days, I’m glad we had a conventional fireplace.

I’m pretty comfortable with auto engines as one of my hobbies is auto racing so I have assembled and disassembled plenty of engines etc.

 I have a cheap 7kW generator (Neighbour gave it to me in broken state and I fixed it), however the thing is really loud when under load. Honda makes some really quiet small generators and some sort of quiet mid size generators, but they are fairly expensive and not really quiet.

My thought of the day is to pickup a used small engine from a wrecked econo-box car perhaps 1.5 litre and mate it to a suitable generator something about 20-30kW (will depend on what is available used and cheap). I will need some sort of gear box to increase speed to generator perhaps 2:1 or  2.5:1 would allow the engine to run at about  1500 rpm. Will need to make some sort of speed control to keep the generator at 3600 rpm as load changes.

If I re-use the original exhaust and plumb it up say 8’ and away from the house I would think that it would be near  in-audible from the house. I would mount this contraption in the smallest metal shed I can find on craigslist and about 100’ from the house.

Wacky idea or fun project what do you think?

Keep in mind I’m retired and enjoy pet projects.

--- End quote ---

A few observations:
1. For 2.5 gears you would need at least a 2.5, but most likely a 3 multiple for engine power. So for 30kW you would need an engine 3 X desired kW in order to run said generator. Also, those small engines do not develop power at 1500 RPM. but more like at around the 3600 RPM that you will require. You possibly could get a diesel that can do this.

2. Placing this generator so far from the house would mean large gage wire in order to carry 30kW 100' to house. This , along with the switch and protection equipment, would be expensive.

3. The ICE engine will be all but eliminated for most uses in the next 20 years, so that is a consideration as far as fuel cost and availability. Have you considered a battery based power wall, such as the one Tesla offers?

Hope this helps...

SeanB:
Probably use an old differential unit, with the spider gears welded together to make a locker, as the gearbox. That way you run the engine at around 22oo RPM, where most small engines, like the 1.4l VW engines, are reasonably fuel efficient, and low noise, but pretty far along the torque curve. 3600RPM and straight in to the alternator, probably a 2 pole version with that speed, and you will pretty much match peak torque and power of the engine easily. Not going to be the best fuel economy wise, but you will have the most power output from the alternator, and it will still last a long time in use.

bdunham7:
I would consider a 1.0L engine from an early Honda Insight, with the (IMA) Integrated Motor Assist still attached.  That motor will run quite efficiently at 3600RPM, but if you are particularly clever you can use slower speeds and the IMA to generate lower levels of power when demand is low, then spin it up to use the main generator for full loads. 

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