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Forum Index : Other Stuff : Advice generator

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nickskethisniks
Regular Member

Joined: 17/10/2017
Location: Belgium
Posts: 97
Posted: 11:08am 22 Nov 2019
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Hello,

I expect we need some extra energy source beside our solar array. So I want to buy a generator for those extra clouded days.

Our power needs are about 7-8kwh/day, normally with our energy input of the solar arra it's enough. Even if I see the total hours of sunlight in december/january there would be enough sun to cover our use, unless we have 5-6 days of dark weather in a row.

That's why we probably need a generator, first I was thinking to make a backup battery and charge it at my parents place, they only live 5km away. But that would be to much hassle.
So a generator, it would be nice to recover some heat, and use it to heat water for my floor heating? But a watercooled diesel engine is way above my budget at this moment. I don't know if heat recovery is worthwile on the exhaust?

I think I need a generator that could sustain about 1kVA continous. Maybe less than 100hrs / winter.

Option one:

Buy one, diesel or petrol? Closed enclosure or open frame? I suppose open frame is nice for doing maintenance and stuf like that. Maybe more handy if I want to ad some copper tubing for heatrecovery.

I was thinking of this one:
https://www.hbm-machines.com/producten//hyundai-hy3200sei-generator-invertor-3200w-met-benzinemotor

https://www.hbm-machines.com/producten//hyundai-dhy8500ae-t-standby-70kw-dieselkrachtstroom-generator

Option two:

Make a generator my self, buy a higher quality diesel or petrol engine. Hook it up with a belt to an alternator.

This would be ideal but maybe just to expensive:
https://www.halvewerk.nl/Webwinkel-Product-94676167/PTM350DPRO-7pk-dieselmotor-(professional-series)-by-Loncin.html

This is a better fit for my budget:
https://www.halvewerk.nl/ptm-200-professional-19-05-mm-as-e-start

What I was asking myself, do they need some kind of flywheel?

I have a few 3 phase ac synchronous servo motors, (permanent magnet rotor) that I could easily rectify and put in one of my solar buck converters. @ 2000rpm they give 120hz and +/- 150vrms AC. The right gearing would be needed. I think they were about 6kVA. But I would use it between 500-1000VA.
Maybe they give to much vibration because the way they are build.


I also have a 5kw 48Vdc 3phase induction motor I could use, but I understand it's verry difficult to get the settings right.
Edited 2019-11-22 21:16 by nickskethisniks
 
renewableMark

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Joined: 09/12/2017
Location: Australia
Posts: 1432
Posted: 08:49pm 22 Nov 2019
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Option two with the second engine should be fine, maybe hook up one or two treadmill motors like here
If you can try and get two identical so you can run them as a matched pair if needed.

If you have an mppt that can handle higher volts you could feed it with the output from that.  Not too sure if it would load it up and make the engine sag or stall.

Otherwise just hook them up and not run them full speed
Cheers Caveman Mark
Off grid eastern Melb
 
Warpspeed
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Joined: 09/08/2007
Location: Australia
Posts: 2959
Posted: 10:39pm 22 Nov 2019
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I am going through all this myself right now.

Originally bought an ex hire 20 amp 240v standby generator, single cylinder 12Hp Wisconsin air cooled engine, for $50 on e-bay. The type of thing you often see at building sites.
Not working obviously, and there was no carburettor or inlet manifold with it.

Anyhow, bought a Chinese carby and it then ran well, but it has to be run at 3,000rpm to reach 50Hz, and being air cooled was very noisy. Rather nasty rope start on it as well.

Next step was to fit an electric starter and car alternator, a 12v battery, and a proper (non magneto) ignition system to it. That turned something rather horrid into something much nicer at very little cost.

The 240v alternator then suddenly decided to fail due to an open circuit field winding. I could have rewound it myself, but decided to junk the whole alternator and fit a treadmill motor instead.

The engine can now be run at only 1,100 rpm and it just purrs at that speed, which is really just a fast idle, and with a huge exhaust muffler, its almost silent. With the garage door shut it cannot be heard beyond.

If I was going to do it all again, I would start with a small four cylinder water cooled car engine. That will run very quietly and it will already have electric start, alternator, and probably EFI. When run at low rpm it should last forever and be very reliable.
Cheers, Tony.
 
Davo99
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Joined: 03/06/2019
Location: Australia
Posts: 330
Posted: 11:48pm 22 Nov 2019
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What you are saying dosen't seem to add up.

7-8 Kwh day consumption.
Want a 1 Kva Generator.
Why are you looking at units so large then that could supply your total daily consumption in 1 hour?  I think there are cheaper alternatives that would do what you want.

Suggestions.

More panels.
If you can go 5-6 days on what you have, increasing that by 50% should get you through unless where you are it rains for a fortnight solid. In that case double your panels and even if you are only making 2-3 KWH day you will be fine. You should be able to get weather data on the amount of sunny/ overcast and wet days where you are to give you an idea of the reserve you might need. Used panels are cheap and you can put any amount on a charger/ Inverter providing you don't exceed the voltage rating.
Charger will take what it needs and be happy. If you have excess you could divert it to other loads. 8 kwh a day isn't hard to make even on a wet day.


Just get a cheap petrol Generator.
Lots of 2.8 Kw petrol gennys around and you could always pick one up used. Pick up a second for a spare and you are laughing.
I have had one of these for about 10 years and had no problem other than the carb leaks if I don't turn the fuel off. It's done some reasonable hours now. Dragged it out the other week after having not touched it for 3 years and the thing fired right up on the petrol that was in it. Filled it up some more and it ran 6 Hours with no trouble at all.

When I first got it the thing would run about 6 hours a day most weekends and did that for about 3 years. Only ever changed the oil and checked the air filter. I did also adjust the carb to give the right frequency a couple of times.



Get a used small petrol/diesel stationary engine and hook that to a treadmill motor/ induction motor / 48V alternator.
You can make an alt from a F&P washing machine motor that will do the output you want well and truly.
5-6 Hp motors are plentiful and would give around 3Kw  so plenty of output. Should take around an hour to give you the power you want given you'll only be making up a shortfall.


Car engine as Tony suggested.  Given the price of that diesel you linked to, you should be able to get a car engine way cheaper.  If you need you could get one of those electronic governor kits but as you will be battery charging I doubt you need that much regulation.  Even at a fast Idle they would put out 5-10 Hp so you could drive whatever you wanted.



For the power you want, I don't know going to the trouble of a co gen system would be worth it. Time everything got warmed up wou'd be ready to shut the engine down. The mean heat output given the running time and fuel burned would not be much either.
Otoh, You could use the power the engine was generating and the heat to warm the place. Get a water heater element and put that in the cooling circuit to boost your heat output.
Probably only economical if you are running a diesel engine on veg or waste oil.

I wouldn't dismiss the small petrol generators too quick particularly if your budget is limited. For the power you need and the time they would be running, with a bit of basic care they should last pretty well.

As it seems you might be in the early stages of off gridding, getting a cheapy generator till you get a better idea of what your demands are really going to be would seem wise. No use spending a fortune on an over kill machine.
 
Warpspeed
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Joined: 09/08/2007
Location: Australia
Posts: 2959
Posted: 01:44am 23 Nov 2019
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Mine is only a small system, 5Kw of panels and a 6Kwh battery.

Once the sun comes up, the battery has reached full charging voltage in about one hour, and over about the next three hours the charging current tapers right down to zero.

There is no real point running a generator for hours and hours just to get the last 1% of charge.
Its far more efficient to have a smaller generator and run it at full load for several hours, then as soon as the current begins to taper off, shut it down.

The slower you charge, the higher the percentage of full capacity can be reached before the current begins to taper off.

So with a 6Kwh battery that is 60amp hours at 100v.  
A ten amp generator will be quite sufficient as the battery usually never even gets down to even half overnight.

A 2.5Hp tread mill motor is rated something like 180v, 10 amps at 4,200 rpm.

If I run my engine at around 1,100 rpm, eight inch to three inch pulley will spin my treadmill generator to 2,933 rpm.
That is 70% treadmill rpm, which should generate 70% of 180v or 126 volts.
Should be just about right to charge a 100v lithium battery to 103.5v.

What I don't yet know is how much throttle opening and engine vacuum that represents.
Still have some pulleys on order, so have not yet been able to test it.
Cheers, Tony.
 
nickskethisniks
Regular Member

Joined: 17/10/2017
Location: Belgium
Posts: 97
Posted: 08:34pm 23 Nov 2019
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Yes I was planning to add more solarpanels, but I need to spent time to search for them, sometimes there are 250w panels for 50€. That's the cheapest I could find, and another 25€ for mounting stuff/panel. But I need more roof, I don't have anymore space on my house, just on the northside. But that's not something I want to do in the winter.

At this moment a generator will be cheaper and if I buy one, faster, the wife don't want me to work at projects the coming months with the new baby. She said "just buy one", we saved 1400€ on gas and electricity this year, so you can have 500€ to invest"...

I was looking at bigger units, because they can start on a battery. Would be nice to hack it, so they start when there is a low voltage on the battery. Maybe bigger generators run much quieter at the same powerlevels.


I found out I still have a motor laying around...
I forgot it completely, removed it 2 years ago in an attempt to convert my lawnmower to electric. It already has a charging coil and electrical starter



Just tested the ac synchronous motor, it likes more to be loaded on all the 3 phases the same way, no vibration then. When spinning with a powerfull cordeless dril, I fed the rectified sinewave in to a heater, that gave me 500w. So not bad.

It would cost me about 100€ to buy the right timming belt and puleys. And a weekend of time to weld somekind of frame and put it together.



I think I need to sleep on it for one more night to make a decision.
 
Warpspeed
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Joined: 09/08/2007
Location: Australia
Posts: 2959
Posted: 09:06pm 23 Nov 2019
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That looks like an 8mm pitch timing belt.
Many overhead cam car engines use 8mm pitch belt and gears.
Typically 24 teeth on the crank and 48 teeth on the cam.
Should be able to scrounge something very cheaply from an auto graveyard.
Cheers, Tony.
 
Davo99
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Joined: 03/06/2019
Location: Australia
Posts: 330
Posted: 10:53am 24 Nov 2019
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Saw the Pic and was thinking exactly the same thing. I have a collection of Timing gears and Idlers off cars.  They can be very strong. Takes a lot of energy to actuate the valves on a quad cam engine turning 6K rpm.

Belts are usually better at higher RPM for the load they can carry but I think they would breeze this in. Belts are changed pre maturely on cars anyway so what would be replaced for automotive use would probably give you hundered more hours use in this setup. You can easily tell the condition just by looking if the writing has worn off and if there are any cracks on the back or missing teeth. They are really shot when they get to that but generally they are worn but not damaged.

The other thing you might get cheap from Vehicles is the Micro V or flat multi rib belts.  You should be able to get a variety of pulley sizes from different cares, just check if they run 6 or 8 groves. On 2 Pulleys with a tensioner, these things can turn 20HP without much trouble.

Being a vertical shaft engine, you'll have to turn the motor the other way as well.
You could tension the belt conventional with a slotted and pivot mounting point but these days idler tensioners are on everything and not even expensive to buy new off fleabay. That way you always know the things are going to be right and don't have to worry about adjustments.

What is the rating of that Motor? Doesen't look very big and is an unusual layout.
Running a 15 Hp engine on that motor  even if you gear it up 3:2 looks like it would  be pretty severe over kill.  Perhaps you could find another larger motor cheap at the scrap yard?  I see them all the time at my local place and often there is nothing wrong with them.  Easy to check with an ohm meter anyway and if you can get them for a few euro above scrap value, you won't pay very much.

I would also look at putting a car muffler on the engine and getting a header made to suit. The OEM mufflers are terribly restrictive for packaging and silencing purposes and do nothing for engine cooling or fuel efficiency. A car Muffler will not only give the thing a quieter note but also let it breathe better and run cooler.
The main noise you will get with one of those engines is mechanical clatter.

Not easy to do much about on an air-cooled engine but double open surrounds will help.
 
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