DIY inverter generator

[bryanb]

I am in the process of putting together an 8 kW micro-cogenerator.  It is only a single phase 120/240 generator so once the 240 is rectified, I should have ~300VDC which will go into the inverter.  The inverter will be a solar string inverter accepting 150 - 600 VDC. 
The purpose of this setup is NOT for electricity!  It is for heat.  The generator RPM will be controlled by the heat demand of my greenhouse.  The generated electricity will just be a bonus. 
I believe I have most of the details worked out except for ...
  as the RPM varies (and thus the voltage), the voltage regulator will not be happy. 
Do I just disconnect the regulator?  What happens when you run a generator without a Voltage Regulator?  The inverter doesn't care what the voltage is, because it has MPPT and adjusts accordingly.
Anyone have experience with this???

Thanks for any and all advice.

[bryanb]

So I finally found some proper information on voltage regulators.  My understanding at this point is that I can pull out the AVR and excite the field with a fixed DC voltage similar to what they call "flashing" when testing the generator.  I don't know what voltage would be appropriate so I will start with 9vdc as mentioned in the "flashing" instructions and go up from there while monitoring the generator output.
I will post back my results when I get a chance to try it ...

Wish me luck!

[LowGear]

Sounds pretty edgie to me but I read the instruction manual once in a while before breaking something.  I'm thinking heavy rubber soles might be the smart first step.

And Yes!  Good Luck.

[mike90045]

The inverter will not be happy with varying RPM/Voltage and the DC rectifier will create lumpy DC from single phase AC

Why not figure what the raw/wild AC voltage is and use that as your heating source and not try to rectify and reinvert  ?   Use a fixes 240V heater element and reduce engine speed (voltage & Hz) as you need less heat ?

[bryanb]

The inverter will not be happy with varying RPM/Voltage and the DC rectifier will create lumpy DC from single phase AC

Why not figure what the raw/wild AC voltage is and use that as your heating source and not try to rectify and reinvert  ?   Use a fixes 240V heater element and reduce engine speed (voltage & Hz) as you need less heat ?

I will be using a solar string inverter which is designed for a variable input of between 100VDC to 600 VDC
The lumpy DC from the single phase will be smoothed with adequately sized capacitors. I am on the hunt for a 3 phase genset though ...

That is a really good idea to use the raw/wild AC in a heating element, didn't think of that.  But the purpose of this system though, is not to use the electricity for heat but to use the waste engine and exhaust heat. The electricity will be grid-tied and used for other than heating uses with any excess being sold to the grid.

thanks for the input and idea though!

[BruceM]

Be aware that trying to slam huge amounts of power directly into capacitors as is done for  small power supplies is going to give you crap power factor, meaning fuses/breakers popping or generator windings fried.  Instead, use a choke filter, around 5 mH, as the first element.  That will restore your PF and smooth out the current waveform. It's going to be a monster, though.  Gapped toroidal transformer cores make nice chokes for this purpose and any of the custom transformer shops can make one for you.  Hamilton makes big power  E-I cored chokes of this sort also, and you can occasionally find them used on ebay. 

Using ICE to generate heat is a lot of moving parts to maintain for what could be done more efficiently and with far fewer parts with a good burner, and some like the Babington can burn any kind of oil.  You aren't the first to attempt this, even on this forum, but the operating cost of using an engine as a heater is not going to work out well economically.  The exhaust heat is about 1/3 of the total and is a PITA to collect due to service/maintenance issues. 

A fun project though, certainly.

[bryanb]

Be aware that trying to slam huge amounts of power directly into capacitors as is done for  small power supplies is going to give you crap power factor, meaning fuses/breakers popping or generator windings fried.  Instead, use a choke filter, around 5 mH, as the first element.  That will restore your PF and smooth out the current waveform. It's going to be a monster, though.  Gapped toroidal transformer cores make nice chokes for this purpose and any of the custom transformer shops can make one for you.  Hamilton makes big power  E-I cored chokes of this sort also, and you can occasionally find them used on ebay. 

Using ICE to generate heat is a lot of moving parts to maintain for what could be done more efficiently and with far fewer parts with a good burner, and some like the Babington can burn any kind of oil.  You aren't the first to attempt this, even on this forum, but the operating cost of using an engine as a heater is not going to work out well economically.  The exhaust heat is about 1/3 of the total and is a PITA to collect due to service/maintenance issues. 

Thanks for the choke filter info! I will do some more research ...   Do you have any recommendations on how to size the choke and I assume, some capacitors?
I will be using Waste Vegetable Oil for the fuel, so fuel cost will be minimal (just collecting / processing costs).  There will be maintenance and service costs associated with the heat exchanger which I have designed and budgeted for.
By the way, I will be using a waste oil burner (boiler) as my backup.

Bryan

[glort]

Been there, done that, have the Vids on YT.

The problem with using a GTI is the MPPT will always be trying to find the sweet spot loading up and unloading the engine. Which will make the engine governor open up and then close down and the 2 just see saw back and forward.
The only way I know to minimize this is to run the inverter flat out with an engine considerably larger than it needs so it can drive ( overdrive) the inverter all the time.
IF you are back feeding it -may- be possible to eliminate the Governor and set the engine speed so it can't move. This would depend on the inverter being driven flat out and the circuit it was connected to also being pretty stable, IE, Heavy wire back to the board rather than on a normal circuit with intermittent loads kicking in and out.  Again, you'd want an engine with plenty of head capacity.

Capacitors are going to make zero difference. Been down that road too. Unless you can access a broom cupboard full of them, they won't have the capacity to provide the smoothing needed.

I'm not sure if your motivation for the project is Fun or profit but if it is profit, let me tell you you are going down the wrong track. you CANNOT make power as cheap as you can buy it from the grid.  Trust me, I have been mucking round with veg oil and running everything I can on it for 16 years now but it takes more than free fuel to make your own generation worth while.  your investment in the equipment alone and the return you get for what you spend will never be repaid.

You mention selling to the grid. If you are going to do this legitimately which you can't because they won't accept it, you are kidding yourself if you think you can make money at 8 or 11C Kwh which is what they will pay, .20 if you are lucky but they won't be buying it off you generated that way.
Maybe you have a solar system and are going to do a dodgy by back feeding it into that.  My moral opinion on that sort of shady practice is ..... Good on you!
Problem is it won't work.  it's going to cost you.

Maybe you are going to do something " illegal" Like spinning your power meter backwards. If you need any  advise on that let me know! :0)
Thing is on both accounts an engine is not the way to go.
Blowing my own trumpet there is not a lot of people that know more about running engines of free fuel than me and even though I have a shed full of engines, I don't bother to use them to back feed. It is not worth it.
What I do have is a virtual Solar farm with almost 20 Kw ( and adding) worth of panels. 
THAT  IS worth it!

I am also just a little knowledgeable in burning waste oil. built loads of the things and am presently modifying a 100Kw spa heater to heat the house this winter.  Still NO engine.  There are too many problems if you think it through as well as impracticality's.
I use second hand panels to make power that spins my meters backwards.  in winter when teh solar falls through the floor I will use the oil burning heater for warmth instead of the  Ducted AC or at least to supplement it.  Don't expect Mrs to go light the thing at 6am on a winters morning, she can hit the air but at night she will be able to come home to a toasty house thanks to the burner.

Engines make noise, you have to attend to them, you have to find somewhere to put them that's close enough to the house not to loose all the heat you get but not too close they drive you nuts or make the place look like a scrapyard.  Burner is much easier to locate and easier to attend to.
Mine will heat water which will be circulated through a radiator with fans I'll probably mount in a window to start with and push the air into the house like that.
I'll incorporate a 2 stage thermostat and have the burner stepped between idle and heat.  Easy to have a fuel pump for the oil and a blower for air on a Pwm controller and switched with a DPDT relay between the modes.  I am also thinking to have a Dump radiator before the spa heater so if things get too hot fans will come on that and pull the excess heat. I will have a non sealed system with a header tank on the roof probably so the thing will never really be able to boil dry and there will never be any pressure in the system.

If you use an engine on veg you WILL have to run a water injection system. Another thing I have done a lot with. If you do not the exhaust will coat the inside of any HE in hours or less and your efficiency will fall through the floor.  you will also probably have to clean the thing almost daily to stop that buildup clogging the HE all together. Hot Diesel exhaust condensing in a Cold HE is NOT a good Idea my friend.  Honestly i'm not even sure WI would be able to offset the problem but you sure as hell won't be able to do it without that as a minimum. You may need to inject water behind the exhaust outlet of the engine as well.  WI will also be a very good safety factor in Running Veg in any diesel.  I wouldn't run an engine without it.

If this is a practical exercise, I would strongly suggest a re think.
If it's for fun, well nothing much matters other than learning.

[bryanb]

1) Been there, done that, have the Vids on YT.
2) The problem with using a GTI is the MPPT will always be trying to find the sweet spot loading up and unloading the engine. Which will make the engine governor open up and then close down and the 2 just see saw back and forward.
3) Capacitors are going to make zero difference. Been down that road too. Unless you can access a broom cupboard full of them, they won't have the capacity to provide the smoothing needed.
4) you CANNOT make power as cheap as you can buy it from the grid. 
5) I have been mucking round with veg oil and running everything I can on it for 16 years now but it takes more than free fuel to make your own generation worth while.  your investment in the equipment alone and the return you get for what you spend will never be repaid.
6) You mention selling to the grid. If you are going to do this legitimately which you can't because they won't accept it, you are kidding yourself if you think you can make money at 8 or 11C Kwh which is what they will pay, .20 if you are lucky but they won't be buying it off you generated that way.
7) Maybe you are going to do something " illegal" Like spinning your power meter backwards.
Blowing my own trumpet there is not a lot of people that know more about running engines of free fuel than me
9) I am also just a little knowledgeable in burning waste oil. built loads of the things and am presently modifying a 100Kw spa heater to heat the house this winter.
10) I use second hand panels to make power that spins my meters backwards. 
11) If you use an engine on veg you WILL have to run a water injection system.

1) Would love to see your videos!  Can you share a link?

2) The generator will NOT be throttle controlled by load.  The throttle will be controlled by the boiler water temperature, so in other words, the heat demand.  So there should not be any feedback loop or any see-saw.

3) I am investigating the choke filter idea that BruceM suggested but if that doesn't work out I may look at getting a 3 phase generator instead.

4) I agree with you about not being able to generate power as cheaply as I can buy it from hydro, but that is not the main function of this installation.  The main function is as a heater, and the electricity is a byproduct.  Granted, an engine is a lot of moving parts and maintenance compared to a boiler, but if you consider the heat output and the electricity, it starts to look better.

5) What motors do you run with veg oil?  And what conversion systems did you use?  Do you have videos of those as well?  I have noticed the newer engines (tdi) burn much cleaner with less soot and am hoping the heat exchanger will not carbon up THAT fast.  We will have to see ...

6) As to the legitimacy of Grid-tie, I already have approval from BC Hydro for the Veg Oil Generator but all I can do is offset my yearly hydro bill.  I will not be able to be a net producer over a full year.  I have sized the generator to deliver my yearly capacity over the heating season  (winter).

7) So I will be spinning my meter backwards during the heating season and building up credits to be used in the summer when the generator is not running.  Not illegal.

Would love to know more about the veg oil fuel conversions you have done!  Links?

9) The spa heater project sound awesome! What type of burner are you going to use?

10) Where did you get second hand solar panels?  I am interested!

11) I am also very interested in the water injection systems you used and the effect on the system.  Do you have links or could you elaborate?

Thanks so much for the feedback!!
Bryan

[BruceM]

Using a big choke as the first stage of filtering (BEFORE capacitor) requires what is known as ''critical inductance''.  You can google that and find the equation.  Other than that, you just need a choke rated for at least your max current.  20,000 uF and 5 mH will probably be adequate.

3 phase would be vastly better for making DC, and would require a smaller choke and less capacitance.  Depending on the inverter, nothing but a 3 phase rectifier may be needed (6 diodes).

I've read about the cyclic loading from MPPT inverters which Glort refers too, but have no first hand experience to be able to suggest solutions beyond the one he suggests which effectively bypasses any MPPT hunting.  The problem he reports I've read of several times from different sources.

Glort will have some words with you when I list this about BC power rates:

Under the Residential Conservation Rate, customers pay 8.58 cents per kWh for the first 1,350 kWh they use over an average two-month billing period. Above that amount, customers pay 12.87 cents per kWh for the balance of the electricity used during the billing period.

Canadians have it pretty soft if BC Hydro lets you store up back feed credits for use 6 months later!  They must be zinging you with a ferocious monthly fee or I can't see how they can manage.  Otherwise you have a free battery service, in effect.  Sweet for you if true.  

[glort]

1) Would love to see your videos!  Can you share a link?

https://www.youtube.com/watch?v=HUE1RQRAXlg

This was Running a 3 Phase Induction motor as a generator by adding caps in a C2C configuration.
I was going to suggest this in my last post but forgot.  I agree with Bruce, 3 phase is the way to go. Induction motors are a lot cheaper  and easier to find ( here at least) than gen heads. If you don't have the genny already, I'd be looking at that.

This is another vid using the induction Genny Direct on a load.

https://www.youtube.com/watch?v=tqy4nJ4cZ5A

The BIG advantage in this situation with a 3 phase induction motor over a genny is you DON'T need the GTI. Hook the 3 phase to the mains power, spin it up and it will be frequency locked and once you get over about 10% rated motor speed, it will start pumping power back to the grid.  Direct connection, no inverter, capacitors or anything else and you will have a stable load that won't hunt the engine.
The only thing will be you have to keep the engine speed above the nameplate rating of the motor which isn't hard if you gear it so " idle" is still producing a little power.  The faster you rev the engine the more power it will make.

2) The generator will NOT be throttle controlled by load.  The throttle will be controlled by the boiler water temperature, so in other words, the heat demand.  So there should not be any feedback loop or any see-saw.

Sitting here doing the mental arithmetic on how this will play out, I guarantee there will be HEAPS of see sawing of the engine.

The GTI will ramp up and down it's demands trying to find the sweet spot where it makes the best power. The fluctuating load on the engine WILL cause it to ramp up and down. It can't do anything else.  you are going to set it to heat demand and the GTI will be trying to get the power it wants. Anything below max capacity it will be looking for more and ramping it's demand up and down which will be loading and unloading the engine and it will see saw.

I won't not go this way at all for your purposes. Direct tie a 3 phase motor, overdrive it and you are there. that simple and problem free.

investigating the choke filter idea that BruceM suggested but if that doesn't work out I may look at getting a 3 phase generator instead.

As mentioned, just go for a 3 phase induction motor.  Cheap and easy to find loads of the things. I found 3x 30Kw units couple of weeks ago. They will give me an easy 15Kw or 5 Kw per phase. more than enough to drive my big 3 phase air con.
The 3 phase can be setup in a C2C configuration to give single phase as well. I think that is what I did on the 2nd Vid.

4)  The main function is as a heater, and the electricity is a byproduct. 

Then I'd just use a heater. :0)

5) What motors do you run with veg oil?  And what conversion systems did you use? 

I run mechanicaly injected diesels. Vehicles, small engines.  All the same.
NO conversion Needed. Don't even get me started on that!  Conversions with heating the oil are all complete and utter bullshit other than for the purpose of keeping the oil liquid.  All the garbage about having the oil hot so it sprays better through the injector is complete and utter crap and an insult to a thinking persons intelligence.  I have run Vehicles for over 10 Years with NO heating of the fuel at all save for sitting the metal filter on the exhaust manifold to put a bit of warmth in teh fuel to dissolve any fats that may have dropped out.

There is a LOT of crap about running veg oil. most of it is by people who never got thier hands dirty doing a conversion and just did what the guy before them did who followed somone else who copied the guy before who.... and not one of them stopped to think why the heck they were doing any of it, how it applied to their situation and what the purpose of what they were doing was. The blind leading the dumb and everyone insisting that is how it needs to be with not one single person thinking about it let alone ever doing some actual testing.

All you need to do is filter and DRY the oil and put it in the tank. If it's cold add 5-10% ULP and that's it.  If the fuel flows and you have processed it properly, that is all that's needed. If you are where it snows, keep the oil at or above about 30oC to keep the fats melted and you are there. In stationary use there should be no problem getting the oil fat free to start with as the engine and the oil should be at the same temp all the time.

Do you have videos of those as well? 

Not many engines on my chanel but there are about 80 boring Vids of me being an idiot so have a look through the channel.

I have noticed the newer engines (tdi) burn much cleaner

This worries me.
How much experience and knowledge do you have of Running veg oil?  It seems not as much as might be advantageous in this project.
I have been doing it 16 years+ and I do things others wouldn't think of and make it work but running a TDI engine on veg is something I wouldn't even dream of!

The Fuel systems are absolutely the worst to use with Veg and are trouble and finicky enough on Diesel.  The VW and Toymota engines also have big problems with EGR recirculation that blocks the inlet manifolds and even can stuff the valves. Using veg only makes that 100X worse. You would probably get past that with WI but it's sure not going to make the weak fuel systems any more resilient.

I would Highly recommend you have a serious rethink about going near a TDI with Veg oil. I wouldn't and I'm wreckless by most pedantic veg oil user's standards.

6) As to the legitimacy of Grid-tie, I already have approval from BC Hydro for the Veg Oil Generator but all I can do is offset my yearly hydro bill. 

Lucky you!
Wish we had that sort of ability here.  Could only dream of such things.
I'm going to do another swifty and carry over my autum accumulation to winter by locking my meter box at read time. They will send me an estimated bill and probably a whining letter about having access to the box but it will allow me to build up some generation credit in advance.

7) So I will be spinning my meter backwards during the heating season and building up credits to be used in the summer when the generator is not running.  Not illegal.

I do it the other way round, Credits with stronger solar in summer/ spring / Autum and struggle by in winter. Trying to hedge my bets as above this winter though.  Been 40C+ here for the last week. winter seems unimaginable right now!

Would love to know more about the veg oil fuel conversions you have done!  Links?

No links, no conversions to link! :0)  hae a look though my channel for some oil processing Vids. that's the important bit. Conversions are complete and utter bullshit. If the engine is fit to run on veg, it does not need a lot of He's and change over valves and all that crap. Been there, done that, life was much better when I woke up and threw it all away. the only conversion needed is the fuel with a bit of blending.  Use petrol NOT diesel. Petrol thins the oil and makes the ignition timing of the fuel much closer to that of Diesel. Blending with diesel just makes thick Diesel. you can't effectively thin something starting at the point you want to finish at.  10, maybe 15% ULP if it's snowing cold is all you need to do to convert an engine and make sure the fuel is properly filtered and DRY.
There are Vids on my channel of how to dry your oil which is mega important and about 99% over looked.

9) The spa heater project sound awesome! What type of burner are you going to use?

Forced air type as I favour on my channel. Probably go for a Horizontal slit type to better replicate the gas burners that I pulled out and spread the heat a bit instead of having it like a concentrated blow torch. I have also been eyeing off the original gas burner and thinking I could probably sit an extinguisher type bottle over the burners and use it like a vaporiser to direct the oil vapor into the original burner.  Start the thing on gas, add oil, off we go. Would just have to play with the jetting perhaps but I don't think so.  Something I might look at.

10) Where did you get second hand solar panels?  I am interested!

Second hand site called Gumtree mainly. I believe it is similar to your Craigslist. Fleabay would be another source. there seems a lot more here than in the states but I don't know what the availability in Canada is like.  I don't pay more than $100 Kw for panels here and usually less.

11) I am also very interested in the water injection systems you used and the effect on the system.  Do you have links or could you elaborate?

Don't think I put up a vid on the WI. I remember filming at least one but Might have lost or not published it.

For stationary use all you need is a constant infusion of water into the engine intake. You do NOT need mega fine mists, ultra high pressure pumps and other expense and complication that you will be brainwashed with on the net.  A steady drip is all that is required.  Many different ways to go about that, all you need to do is make sure the water stops when the engine does. Could be as simple as a relay that activates a small pump or a solenoid valve and shuts off when teh engine stops as in powered from an alternator.

Amount of water is not critical and don't get concerned about hydrolocking the thing. You'll know well in advance if there is too much water by the engine stumbling and steaming out the exhaust a LONG time before she locks.  Never tried it but I highly suspect unless one dumped a load of water in the intatake it would be near impossible to keep an engine running with a stream of water and get it to compression lock on water. The fire would go out way before.

As a rough guide i'd say 300 to 500Ml would all that would be needed to keep an engine deposit free. For vehicle engines I have found 300 ML a MINUTE max delivery on a 3 Litre engine works well. That's not constant though, I set that up when the engines are under at least 50% load. I have run a lot more than that for performance purposes but for cleaning, can't clean whats not dirty so that is well adequate.

For stationary use, regular feed is better and does not need a lot, just enough to keep deposits building up. Mind you, if water is close and easy to full a good size tank, A litre an hour wouldn't be bad either.

Thanks so much for the feedback!!

You're welcome. Give me some insight as to what your veg oil experience is.  A lot will be riding on your knowledge with that for the success of this project.

[bryanb]

Very helpful input. Thanks!

BC Hydro monthly fee is only $6.  Yes, that is cheap for the use of the grid to build credits for the other half of the year.

I have been only mucking around with veg oil for 4 years and only in a heating system.  I have diesel vehicles but have not used veg oil in them yet.  You have encouraged me! I have not bothered with drying the veg oil for the boiler as it is not really necessary for a burner but I will have to build a system like in your video. Thanks!

It also turns out that I have a couple of larger 3 phase induction motors kicking around.  I am definitely going to check this out!  Don't know what C2C configuration is but sounds like that is what you did to get single phase out of a 3 phase motor.  Could be useful for other projects.  I will do some more research.
Are the capacitors on your induction generator for smoothing or for excitation starting?

I don't understand how your induction generator locks the frequency when you back-feed to the grid.  I don't have any intention of doing that in this system, just interested. 

Cool videos by the way ....

[BruceM]

The induction generator is self syncing when doing grid backfeed, you just increase rpm slightly above operating rpm and watch the backfeed current as you pour on the power.  Much cleaner and simpler setup for you, better efficiency.  No load specific capacitors needed for this application, and it automatically stops when power shuts off. 

[bryanb]

In my case, generating to feed the inverter, or as a standalone generator, will an induction geny self excite?

[bryanb]

I doubt BC Hydro will allow a direct backfeed from an induction generator such as this because of anti-islanding and safety rules. But as a standalone backup generator, I am excited! (pun intended)