Automotive engine for an electric generator?

[Pleiades]

I have a diesel Nissan Vanette that was recently involved in a little ‘accident’ and will probably not pass its inspection next year, the engine however is in good condition. I have this crazy idea that I could take the engine out and couple it with a generator head to make a generator set.

 

I have a feeling this is gong to be a biggish project but I can’t bear to throw out a perfectly good engine. I did some searching and I found that a 30 kW generator set costs around $10,000, but a 30 kW generator head only costs $1,000 - $2,000. So I want to use the engine to make a relatively cheap generator set.

 

My biggest concern is the governor mechanism (voltage regulator): in order to make electrical power a the right voltage and frequency, the head has to be running at its rated rpm, the engine needs different amounts of fuel to produce the same rpm under different loads, so I need a governor to adjust the fuel to the engine so that the engine speed remains constant. Does anyone know how or where I could get such a mechanism, and how I should modify the engine to accept the governor? Is this beyond the average persons abilities, or can it be done?

 

I looked at the engine and it’s labeled as a “LD 20”, information on the internet is scarce, but I found this page: http://www.jescoweb.com/LD20.htm that gives some info. I figure it should be able to handle a 15 kW generator head with room to spare, which is certainly enough for my home (even with the water heater and all the air conditioners!)

 

Any info on putting together a generator set would be greatly appreciated.

[YT2095]

Hmmm.. Ive done it several times on a Small scale, using 80amp car alternators for 12v out with electronic regulation, but for something of this scale, presents a new set of problems all together!

you obviously don`t want to "ride the clutch" either.

there Are centripetal govenors though, you can even make them youself with a little skill, and in effect as the rotational speed increases the weights want to "Fly outwards" and that in turn pulls a plate up, a plate movement that could easily operate a throttle.

 

I`ll have to think a little more about this, Nice Question!

[Pleiades]

I’ve been doing a bunch more searching and thinking, and I’ve found a few products that will govern an automotive engine to a set rpm, unfortunately the site is under renovation, so I can’t find out anything else about it.

 

The simplest way may be to just build an old steam style governor and link it to the accelerator pedal (the engine won’t be in the van, but I might save the pedal), then I’d just have to play with the weights and linkages to get the right rpm, like this: http://www.history.rochester.edu/steam/thurston/1878/f29p115.gif . I’m not sure if it will be accurate enough however.

 

This page was also quite helpful: http://utterpower.com/governors.htm

 

What would be really nice is if I could just find a good product for converting an auto engine to constant rpm use.

[chilehed]

Didn't the early automotive cruise controls use a mechanical control system?

[Pleiades]

I believe the early ones were mechanical, in fact many small engines still use mechanical flyweight governors, they are just far more complex than anything I could make.

 

From the bullets at the bottom of this page http://64.78.42.182/sweethaven/MechTech/Automotive01/default.asp?unNum=4&lesNum=1&modNum=5 I am starting to doubt a simple mechanical governor would be accurate enough to control a generator that will power my house.

 

After reading this page http://64.78.42.182/sweethaven/MechTech/Automotive01/default.asp?unNum=4&lesNum=1&modNum=6 I think I may be able to buy a hydraulic governor such as these: http://www.woodward.com/engine/diesel/diesel2/governors.cfm , I’m not sure which one I need, or which one will work, maybe I’ll email them.

[YT2095]

after having thought about it, the answer`s almost Too easy!

 

why not do it electronicaly afterall?

ever wondered how a CD or floppy always manages to spin at a constant rate?

also you don`t need the entire pedal assembly at all, the throttle`s on the carb (just under the air filter) you can rev it to max with your little finger, or even a little 5 volt servo!

all you need then is either a magnet or silver marker on the drive shaft and a sensor to detect this (infrared emiter/detector pair) or a magnetic detector, as the shaft rotates it sends a pulse to the electronic govenor that detects the Rate (frequency of that pulse) and then that in turn controls the throttle servo.

 

simple as

[Pleiades]

Well, it’s a diesel engine so there isn’t a carburetor, but yes the amount of fuel injected is controlled be a small lever that could easily be moved with a small servo. There are also many different ways to sense engine speed. The problem is that I don’t know enough about circuit design and feedback systems to do it properly. This is what I’ve come up with:

 

When the dc motor attached to the shaft spins it puts out voltage in proportion to its speed, when the voltage is too low to trigger either of the zener diodes, the lower relay gives power to the servo to increase the fuel. When the voltage triggers Z1, the relay turns on, cutting power to the servo, this is the balanced state. If the RPM gets too high, the voltage raises until it triggers Z2, which engages the second relay, delivering power to the servo with a reversed polarity to reduce the fuel. There are probably a dozen things wrong with this setup, but it’s a start. I’m reasonably sure this could be done better with transistors, but I don’t know how. I’m also worried that the voltage may not be enough to engage the relays.

 

Link to image:http://www.scienceforums.net/forums/attachment.php?attachmentid=1253&stc=1&d=1142466034

[Pleiades]

It seems Woodward makes a product designed to exactly what I need, the SG 2D Digital Speed Governor, midway down the page: http://www.woodward.com/engine/diesel/diesel2/electronic.cfm . Now all I have to do is wait until I can get my hands on the engine.

 

I guess we can call the issue resolved then, I could probably rig something up, but it wouldn’t be as responsive as anything I could buy, and I’m not too fond of the lights dimming when I turn on the toaster. Thanks for the input YT.

[DV8 2XL]

Correct me if I am wrong, but I think you have to govern the engine against frequency of the A/C output rather than the output voltage. I believe that's the case for most gensets.

[Pleiades]

My plan in post #7 has a lot of flaws, so you can disregard it. The engine RPM and the AC frequency output by the generator are directly tried if you keep the engine at a constant 1800 rpm, you will produce a constant 60Hz (assuming they are directly linked without gears). When you increase the electrical load, the RPM goes down as does the AC frequency, I’m pretty sure the voltage goes down as well, but I doubt the relationship between RPM and voltage is linear.

[Prime-Evil]

I have a diesel Nissan Vanette...

I think you are on the right track if you need that much power and want constant power at near the optimal specific fuel consumption. Highest efficiency is usually found somewhere around the same rpm as maximum torque, but 1800rpm is probably the easiest if you want 60Hz, or 1500rpm if you want 50Hz. Diesels have really good low end torque so 1200rpm or 1000rpm might be even better. I am not sure what power you would get maximum efficiency, but if you lean more to the quiet side of that you will get longer life.

 

A 1000/1200rpm 15kw generator seems about right. If you are using it for occassional emergency power and only need 3kw or so then you might go down to 500/600rpm and find a nice sweet spot. You should right to Nissan and get the performance curves from their dynamometer test.

 

So what is the price of diesel and electricity in Bermuda? Just curious.

 

If you had a 5kw wind turbine you could use it to produce hydrogen fuel when it is generating more power than you need and then run the desiel generator on hydrogen or hydrogen/desiel on days with no wind. I would imagine there are restrictions on such things in Bermuda. Really nice place though. Too bad about sea level rising and all that. Should be good for another 500 years or so eh. A good desiel engine should last that.

[Pleiades]

Electricity here is about 26c/kWh (yes that’s US cents), diesel is about $5.34/US gal, and gasoline is over $6/US gal.

 

Currently we have a 5kW air cooled gas gen set for emergency use (a few times a year at least, we get a few hurricanes) I want a generator that can handle 4 room air conditioners and 3 fridges, not to mention the heat pump and water heater, plus a whole bunch of intermittent loads, like the water pump, toaster, microwave, etc. we use about 40kWh/day on average.

 

We use propane for our dryer and oven, and we have a solar water heater panel, but we would still need a huge photovoltaic system, I’m having a hard time getting my family to lower our energy use.

 

I worked out the cost of an all photovoltaic system, and regardless of size, it would take about 17 years to pay for itself, since we get no assistance form the government (I’m hoping they’ll come out with cheap plastic PV soon). Also our power company is an evil monopoly that doesn’t allow net metering, in fact if you try to put power back into the system the new wireless meters they just installed will notify the company of tampering (I checked the product sheet from the company that makes them).

 

Wind power is a possibility, the island is pretty much suburban all over, I might be able to get permission for a windmill, but it would be a fight. The other problem is the wind is normally fairly low, 10-12 mph, but it can get up to damaging speeds during ma hurricane. I’m also behind a hill.

 

I’m also having a hard time finding any info on the engine I have, should I just email Nissan, or is there a better way to get detailed specs and performance curves?

[Prime-Evil]

Good details. Thanks. $10/day. Ouch.

I was in Bermuda in 1996 for Race Week at the dinghy club. Loved it.

 

I would suggest emailing Nissan, but also just finding the perfomance of any similar sized deseil engine and then scaling it to your specific specs.

 

Here is a wacky idea. You build a boat and go sailing once a week and drag paddle wheel or propellor downwind to produce and compress hydrogen by electrolysis, and then use the hydrogen tanks for your emergency generator. I understand if you convert a gas or desiel engine to hydrogen you will get higher efficiency but less power.

 

Lets see now.

40kwh/day x 3412 BTU/kwh x 7 days / 52,000 BTU/lb / 40% = 46 pounds

At 10,000 psi, 10g/litre = 10kg/m3. 10 x 46 / 2.2 = 209 cubic metre

 

I guess you would need a pretty big sailboat.

[DV8 2XL]

Currently we have a 5kW air cooled gas gen set for emergency use (a few times a year at least' date=' we get a few hurricanes) I want a generator that can handle 4 room air conditioners and 3 fridges, not to mention the heat pump and water heater, plus a whole bunch of intermittent loads, like the water pump, toaster, microwave, etc. we use about 40kWh/day on average.[/quote']

 

With a bunch of reactive loads like that you are going to have to make frequency discipline your priority. I suspect also that you will need a rather big flywheel to make up for the lack of spinning reserve.

 

Am I right in assuming that this engine has some sort of electronic fuel control unit already in place? If so then this would change the problem considerably.

[Pleiades]

As far as I know the shaft RPM and the AC frequency are directly proportional to each other; governing one should govern the other too. I’m assuming the electronic governor will have a fast enough response time. I would like to add a massive flywheel to it, but I think it might add too much complexity. The engine is oversized, so that should help.

 

I’m not sure what you mean by “electronic fuel control unit”, as far as I know the engine is totally un-computerized, as it is fairly old. I don’t know for sure, because I haven’t had the vehicle apart yet, but I assume the accelerator is connected with a cable to a mechanical device on the engine that regulates the amount of fuel pumped into the cylinders. I’m hoping I can attach some sort of actuator to the linkage on the engine, but I’ll have to wait and see.

 

Now that I think about it, it will probably be about a year from now until I can get my hands on the engine, as I will be going away to uni this fall.

 

I’m a bit wary of adopting hydrogen as a means of storing electricity at this point; the tech just seems too immature at the moment.

[YT2095]

another way you could do it (although it Is cheating a little bit) would be strip down one of these little suitcase generators, take the speed govenor out and throttle arm linkages and put that in place instead.

you can then set the rpms manualy by adjusting the spring tension to set it for your engine and away you go

[DV8 2XL]

As far as I know the shaft RPM and the AC frequency are directly proportional to each other; governing one should govern the other too. I’m assuming the electronic governor will have a fast enough response time. I would like to add a massive flywheel to it, but I think it might add too much complexity. The engine is oversized, so that should help.

 

The electronics may be fast enough - the response of the engine may not be. In most A/C systems, controllers trade voltage for frequency - that is they give up the former to protect the latter. this is because many reactive loads can stand more variation in voltage than frequency. With all the reactive loads you are planning to have, you have to consider the fact that they will be switching on and off in an uncoordinated way and this will play havoc with your system if you don't have the controller to deal with it. Unfortunately for you, this is not a trivial issue.

 

I’m not sure what you mean by “electronic fuel control unit”, as far as I know the engine is totally un-computerized, as it is fairly old. I don’t know for sure, because I haven’t had the vehicle apart yet, but I assume the accelerator is connected with a cable to a mechanical device on the engine that regulates the amount of fuel pumped into the cylinders. I’m hoping I can attach some sort of actuator to the linkage on the engine, but I’ll have to wait and see.

 

Most automobile Diesels made in the last twenty years use an electronic FCU (fuel control unit) to manage the engine, as injection-types require a bit more finesse than just opening a butterfly valve to change RPMs. All mechanical systems exist, but I would be very surprised to find that this is the case here

[YT2095]

Most automobile Diesels made in the last twenty years use an electronic FCU (fuel control unit) to manage the engine, as injection-types require a bit more finesse than just opening a butterfly valve to change RPMs. All mechanical systems exist, but I would be very surprised to find that this is the case here

 

even so, at some point there will be a mechanical interface, even if it`s only a potentiometer linked to the accelerator pedal

[DV8 2XL]

even so, at some point there will be a mechanical interface, even if it`s only a potentiometer linked to the accelerator pedal

 

You might be surprised. My old Delta 88 had the accelerator cable pulling three separate actuators. Nevertheless, I still think an all electronic control will be necessary in this case because of the load profile, regardless if it just pulls the rods. In the long run it may be better to use the motor to run a DC generator rather than an alternator and use an inverter to get the AC. That would solve a lot of problems right there.

[YT2095]

ordinarily I`de agree with you there, but for this application/scale, the cost would be prohibitive. if it were for a caravan while camping sure.

Hmmm... I wonder I wonder how these guys at fairgrounds get on, you know, the mobile (on the road) type of fairs.

they easily consume enough power to fire up several houses, and also employ very large inductive loads as well as lighting.

it might be worth a snoop around and picking some brains next time one comes to town, it`s got to better than a centrepetal slip clutch

[DV8 2XL]

Those big sets use a rotating field type of alternator with an auxiliary DC exciter controlling the flux. Also, as I said these sacrifice voltage stability for frequency stability, which is why you sometimes see the lights dim occationaly on these circuits.

[Pleiades]

Ok, an RPM governor is a good idea even if the engine can’t react fast enough right (it should react fairly quickly shouldn’t it, since it’s an automotive engine?)? So I’ll buy the governor I mentioned in Post 8 (assuming its compatible), and then I’ll include a voltage/frequency controller if necessary.

 

Now about these voltage/frequency controllers: what is the proper name for them so I can read up on them, or can you just post some links about them. Shouldn’t a controller like this be built into the generator head I’m going to buy and attach to this engine? I’m going to try and get a hold of the Engine Supplement service manual for this engine, until then, I don’t know much about it except what is show on this page: http://www.jescoweb.com/LD20.htm

 

I haven’t researched it that much, but I will probably be using a Marathon generator like this: http://www.marathonelectric.com/generators/Catalog/details.asp?IDQ=608&IDQ_MODEL=283CSL1507 , or similar. It seems this has an Automatic Voltage Regulator built in, so as long as the engine has some sort of RPM governor, the output voltage and frequency should be pretty stable.

 

Does anyone have any ideas on how I can record and graph how many watts my house is using over a few months so I can figure out exactly how much variation in the load I can expect?

 

I imagine the mobile fairs use a preassembled generator set with all the control systems built in.

 

Oh, I was slightly off on my fuel prices, I had a look at the pump today: $5.47/gal for diesel and $6.52/gal for gasoline.

 

The service manual for the engine was first published in 1983, so the engine may possibly be a pre-FCU engine, but I don’t know.

[DV8 2XL]

Well the good news is at 1800RPM you can probably set the high-idle control to that value and let the engines own regulator deal with it. The bad news is that frequency control is not that easy to maintain unless you have a good spinning reserve, which is to say that you have to run the alternator such that you always have 20% more power available than what you are actually loading at any given time. This is not a trivial problem.

 

Watt-hours of usage you should be able to find from the existing meterage on you house - graphic display devices are on the market and some utilities will install one on your line as a service - check with your power company.

[YT2095]

you COULD buy a clamp on Amp-Meter (no wiring needed, it simply clamps onto your IN feed before the meter)

you`de have to check on it regularly though and take a reading, although some will have a digital output that will log usage on a PC at what ever sample rate you set.

[Pleiades]

Summer is coming and although I'll be working, but I might get some time to work on this project, so I’m dusting off this thread. Now that we have a projects subforum, maybe this thread should be moved (or maybe not, since its not really a ‘science’ project, I don’t know).

 

Oh, and does anyone know of a good forum that specializes in engines? Car forums won’t know much about generators, and generator forums won’t know much about automotive engines. So I’m hoping to find a forum about engines in general. Although, the end in mind is to put together a generator, so maybe a generator forum would be good. Anyway, Google wasn’t much help, maybe I used the wrong search terms, so if anyone knows of a good forum, let me know. I’d like to get as much input on this project as I can (not that you guys haven’t helped me already).

 

The bad news is that frequency control is not that easy to maintain unless you have a good spinning reserve, which is to say that you have to run the alternator such that you always have 20% more power available than what you are actually loading at any given time. This is not a trivial problem.

Let’s be generous and say I use 48kWh/day. That works out to an average load of 2kW. If I have a 10kW generator, then most of the time it will be running at only 20% capacity, leaving an 80% spinning reserve, which should be way more than enough. And let’s face it, pretty much anything is better than the 3600RPM, 5kW, air cooled gasoline genset that I have now.