Producing a Generator With a Car Engine

Depending on your application, using an automotive engine to drive a generator might not be the best choice. Automotive engines are not intended for long-term continuous duty application. This often surprises people, since cars last "a long time," but almost all of that time is spent just sitting "parked."

Automotive engines are designed for a total operating lifetime of less than 6000 hours (150,000 to 200,000 miles at an average speed of 30 miles/hr), which is equivalent to about 9 months of continuous operation. Commercial generators are built using diesel engines that are specifically designed for long life.

Well, I've read 20 odd posts here and it's obvious there is lots of engineering talent here and not a lick of financial sense. The question is not how much longer a diesel lasts than a gas engine, but the relative cost-efficiency of the two types. Given the high cost of diesel fuel and the much higher cost of a good diesel engine than say an endless stream of cheap V-8 Detroit small block engines from junk yards or rebuilts from Kragen, the question is, "which is more cost effective given your use?".

If your use is as an emergency backup generator and that is a rare occasion, the capital cost of the diesel alone puts it at a big disadvantage. Get the fuel specifics curve for the target engine operating at the target load and that will determine the fuel costs. My guess is the fuel costs will be comparable. Fuel-injected gas engines have better fuel specifics, last longer, and produce more power. Longer stroke engines will give better torque curves, but again, figure out your target loads and uses first. Then sit down and do the cost-benefit analysis. Except as a science project, your goal is to generate power for the lowest cost, not have the coolest diesel on the block.

Hi guest,

• The question is not how much longer a diesel lasts than a gas engine, but the relative cost-efficiency of the two types.

Looking at problems from a purely cost effective basis is what got us into this global warming mess. Unfortunately the true cost of burning fossil fuels is many times greater than we are currently paying as it doesn't reflect the costs that everybody is going to get hit with as a consequence of burning fossil fuels. If the Antarctic and Greenlandic ice sheets melt the 70 metre rise in seal levels is going to wipe out all but a couple of the worlds major cities. How much do you think it's going to cost to rebuild the likes of New Your, London, Las Angeles, San Francisco, the entire state of Florida, Sydney, Melbourne, Auckland, Wellington, Hong Kong, thousands of Pacific Islands including the Hawaiian Islands and so on. Add that into the cost of fossil fuels any you will be paying thousands of dollars a barrel for crude not the miserly US$100 we are currently paying.

The only question we should be asking is which is the most energy efficient and environmentally neutral way of generating the energy. The cost effectiveness should be either at or pretty close to the bottom of the list of factors for consideration.

I agree with Steve petrol engines out of a car just don't have the life expectancy or economy to be viable. It depends on the amount of power you want to generate but generally for household quantities a diesel would be the way to go. You may be able to pick up an old marine diesel that would work.

Diesels in general are:

more fuel efficient than petrol engines

more reliable than petrol engines

work better at a constant speed

produce better torque at lower revs

safer as diesel fuel is less volatile than petrol and won't burn by itself

don't require electric ignition systems like petrol

You asked about a car engine so the diesel would be the first preference but don't overlook gas turbines. There are some small and very powerful gas turbines around now and may be worth looking at. I read an article recently about a gas turbine that was about the size of a medium coin with a diameter of about 15mm.

One more plus - diesels respond better to sudden loads.

A little minus - they require more and pricier speed control apparatus - although not if you're going to be asking for precise AC frequency control.

As to life expectancy, the biggest single factor in lowering the internal life expectancy (in number of operating hours) of a gasoline engine is turning it off - gases condense and it starts to rust - ok oxidize - inside. Ford used to run them for a million miles in the sixties to show how durable their engines were, but it was as close as possible to one continuous run with "dynamic" oil changes. They may have been shut off for plug changes, but off-time was minimal.

On the other hand, if, like me, you have gasoline engines there is a lot to be said for things that are effectively free.

MASU is mostly correct, but Diesel can burn if raised to its flash point - about 62°C and a spark occurs. The flashpoint for Petrol is about -45°C. 107°C difference!

BUT - Diesel will autoignite at a lower temperature (as it is designed to do!) than Petrol, 210°C as against 245°C for petrol.

See Wikipedia for a better and fuller explanation if needed.

Diesel is still better and far safer in 99% of the possible applications!! Only in very low temperature environments is Diesel slightly more problematical, but these problems can be addressed and fixed.

When I was young my father put together a generator set up with a Voltswagon Rabit diesel and a farm generator designed for a tractor PTO. It worked but he never ran it for long periods.

Please excuse me for straying off subject. I've seen a 4 cylinder Voltswagon engine modified into an air compressor. I.e. 2 cylinders powered the engine, while the other 2 cylinders compressed the air. I was very impressed with the contraption. Although I don't know how its performance rated over time. I think conversion kits are available. But I'm not sure Who or how much.

That's pretty neat. I wonder how it compares in efficiency to using the driveshaft to run a compressor?

It definately had a high volume supply. The owner used to power a 90lb jack hammer with it. The engine was out of a Super Beatle. It ran slightly above idle. He said it was easy on gas.

I love it when the McGyver in people comes out!

hey, I want to do the same and was wondering if you remember how many kw the pto generator head was. or anything else that might help thanks

A company called Tecogen (also known as Tecochill) did just that about 15 yrs ago. They used a marine engine based on a GM 454 modified for natural gas. The engine was supplied with a larger oil reserve and operated at a higher rpm than a small Caterpillar or Cummings engine would operate. I believe they were claiming about 16,000 hours between overhauls (which meant getting a new engine -- which might be cheaper that doing a top end on a diesel based engine). I cannot remember the power capability, maybe 150 kW.

They have a web site.

Diesels can also burn vegetable oil, household heating oil, or kerosene-motor oil mixutures in a pinch. Biodiesel is only complicated when you try to recover USED oil.

Actually, I thought the problem with vegetable oil is that it contains glycerin, which doesn't burn well, smokes, and gums up the engine. While "in a pinch" might be OK, prolonged use would be a problem.

The biodiesel conversion process replaces the glycerin with alcohol to eliminate that problem. See this CR4 post for more information.

also you can heat the oil to thin it to the proper viscosity This is also a time proven method and is very easy to setup for a generator.. Used oil works just as well as new however used oil must be free of water and particulates. Settling in a sealed container can seperate most of these contaminates very easily. there is lots of information on converting an automobile this way. Greasecar.com is a site that comes to mind

Thanks a lot,right now i am writing my first semester examination.I will get back to you when i am through with my exams.But i will like to know your phone number or address so that we can be keeping in touch.THank you for your concern.

You can build an AC or DC generator from any engine. period. what you have to do is define what type of generator you need and for which application. Emergency or continues service etc. The basic difference between an engine designed for a car and the one designed for a generator is the speed vs. load control. As you probably know Alternating Current (AC) frequency is RPM dependent, and so is the torque. If you want to keep your Alternator running and producing a constant voltage regardless of load , you have to control your engine speed. This is achieved by a GOVERNOR and there are several types of governors. Most AC generators use standard SAE coupling, or direct shaft couplings (lower power generators) so there is no problems in attaching them to the engine, take the gearbox of and bolt your generator on. Most Home Depot emergency and small generators are gas engine driven for price consideration. Diesel engines by nature are much more expensive, although they are coming down in price every day. BTW: I have played with the idea of installing cruise control system as a mean of controlling engine RPM, but due to lack of time I didn't pursue it. If you feel like go ahead and try it. no rights reserved here...

Hope it helps.

Wangito.

Without knowing how much power and how long it is needed makes the task very difficult. A simple inverter could be used for short time periods and under 2000 watts of power. For larger applications i would not recommend a conversion unless you have unlimited resources. best of luck Stoneman

SO...I was looking into the feasability of using my F350 diesel truck as a 110 AC generator. These posts have been very helpful. Keep in mind I will want to keep using it as a truck as well. Wangito's post gave me the most insight. Seems like I would want to disconnect drive belts and connect an alternator. Hey what about using the existing alternator?

Since the 7 plus liter engine was designed for other purposes would it be ineffecient/mechanically problematic/prone to say overheating. My goal would be say to go somewhere for a week and be able to use the truck as a generator whilst parked. Silly?

Make more sense to throw a portable generator in the back? I'm sure.

How bout just going from batteries (setup with two 12 volts) to a heavy duty inverter seems simple and of course I already do this for small appliances with a little inverter.Looking for enough juice to run lights and an Air conditioner in my trailer.

How much power @110AC do yo want? Up to one KW , no problem, just fit another belt driven alternator if you can, and connect a 12/110V transformer directly to the alternator output (12V to the alternator side)by-passing the diodes assembly, and at the other side of the transformer you get 110VAC. How much power? that will be the alternator current capacity times 12V. For instance a 75Amp alternator will give you 900W. If you don't care about pure AC, and if you are not going to operate frequency sensitive equipment you'd be OK. But than again, you will need to control your engine RPM. and don't forget, the 12/110V transformer must be the same wattage as your alternator.

And as final word, YES, it is much simpler to just throw in a small generator, and it maybe even cheaper...

Wangito.

Hey,

I'm an aerospace engineering student working on my senior design project. Our group is trying to design a vehicle that can fly as well as drive low-speed on the road (35km/hr). We'd like to use the aviation engine (200 hp diesel, lots of torque) as the powerplant on the road. What do we need (equipment or weight-wise) to convert that physical torque into power, then use it to drive the wheels with electric motors? I have no idea if this is possible / would be lighter than a transmission, but man those trans weigh a lot...

Hi guest,

An interesting project but if you have any chance of changing what you are designing to something else then I would advise ditching your current design and starting over.

Over the past 75 years or so there have been numerous attempts to produce a motor vehicle that can also fly and the one thing they all have in common is their abysmal failure at being either.

The problems stem from the design parameters and there are way to many areas where the two concepts are incompatible. You would also find it impossible to get the dual certification required for aircraft and road vehicles simultaneously. If you read through the appropriate standards you will find there are so many examples of standards that preclude the other application that you would end up building two separate vehicles with no commonality other than the bits that clamped them together.

One problem area is the power plant. Aircraft engines are designed to operate at constant settings for lengthy periods of time and do not take kindly to the sort of continual throttle variations required for a road vehicle. When you go the other way the engines from vehicles are not designed to operate at constant speeds for lengthy periods and do not have the redundancy required for use in an aircraft. To start with the only mass produced car engine that had a dual ignition system was built by Nissan and was scrapped after less than a year due to the high cost of maintenance. Then you get to the propulsive force, an aircraft uses thrust while a vehicle uses friction of the wheels against the road.

You and up needing to double up things all the time and with an aircraft you can't afford to double things up as you seen end up with something that is way to dense to get off the ground.

The big problems comes from the way loads are applied to each. As you are no doubt aware aircraft are only subjected to distributed loads when flying which lends nicely towards the use of monocoque design concepts. On the other had a road vehicle is subjected to point loads where the wheels attach to the sub-frame or chassis.

If you have no option but to continue with the concept then I wish you luck, but be warned, many have tried before and so far nothing even close to being practical has ever come out of it.

Well this thread sure veered from the original question, now its flying cars. I want one.

I ended up, in a round about way with what wanted. I have a hugh stepvan that came equipped with a high output alternator, a idle control and a dynamic inverter.....it happens to be a turbo diesel. So now I just start up the vehicle, push a button the engine revs up a bit and I have 4000 watts ac 110 on a 30 amp circuit. pretty cool and practical. I can run a chopsaw and a table saw at the same time. It may not be as efficient as some setups, but it sure does the trick. has any one answered the guys original post? doesnt he just need an alternator and an inverter something to control rpm in addition to all that will make whatever engine go?

Now my setup would have cost like 4 grand in parts.....thats what i paid for the van and it was a bonus that it came with this. I could buy a hell of a generator for that. I think the og guy was looking for on the cheap.

A car engine will last forever as long as you keep the engine horsepower no more than half on it's rating. For example a 2.0L 4 cyl engine designed to produce 140Hp in a car should be run at no more than 70 hp or the best at 50 hp.

An engine derated to that level will last forever not as long as a diesel engine but much longer than 6000 hours quoted by someone. Do not forget if you run the engine continuously it's better than cold start many time everyday in a car application. Plus a diesel engine run infrequently will develop problems ask boat owners with diesel engine.

Stick with a car engine and derate the engine I'm sure you will be surprised.

what if i were to adapt an ac clutch pulley to the electric motor of a gas powered generator. idling at 700 rpm and even at cruising speed (70 mph at 2200 rpm) i should have no trouble generating enough dc power to power whatever i want and i could switch it off and on top of that i wouldn't have to rely on any inverters or extra batteries. is it possible?

It's possible, but challenging. I assume you want to use the full power of the engine, not just the normal 14.5v DC alternator and an inverter. You would then need a large alternator, probably at least 50kW if you were using a chevy V8. Then just find a way to keep the alternator going at 3600 RPM (or 3000 if your using 50hz power). If you wanna run the engine at 3600 you could direct couple it which would be the easiest, or gear the engine down at a 1.5:1 ratio so you can run it at 2400, which would give you longer engine life. Would be a fun project. Probably the most expensive part would be the alternator, big ones don't come cheap. Cheaper to just buy a generator outright, but what's the fun in that? :)

G'day gals, guys & gurus,

This post has been dormant for some time, but I'm glad it's started up again as there are some interesting developments that may be relevant to this thread.

Currently we are looking into having what in Australia is referred to as co‑generation. In our situation we will be using solar panels mounted on the roof of our house to generate DC power. The DC from the panels is then fed into a solid state inverter that is synchronized with the grid and turns it into the standard 240 Vac 50 Hz power everything here runs on.

The resultant power is generally used in the same building, but any excess generating capacity is fed back down the power lines and onto the grid where it is distributed to wherever it's needed. At the moment the electricity utilities are pushing this technology big time and will purchase any excess capacity for 60 cents per kilowatt hour. That's about twice the cost peak usage time electricity and it's not too difficult to drastically reduce you electricity costs.

Anyway, the main reason I'm bringing this up is the inverter. Because the inverter utilizes a DC input it doesn't matter that much how it's generated and provided it's within certain limits it can be fed from wind turbines, solar panels, hydroelectric, etcetera.

In this instance I would use an alternator or AC generator attached to the car engine to generate raw AC power. This is then fed into solid state rectifier with the resultant DC output being fed into one of these solid state inverters that give you usable AC power.

There are several reasons for this:

1. Design Simplicity: The solid state inverters are now readily available and can be purchased off the shelf. This makes the design much simpler and reduces the overall cost of the system.
2. Alternators: You can now get alternators or AC generators that have no brushes or commutator. This reduces the maintenance required to keep the system operational and therefore makes it more reliable.
3. Grid Synchronization: If you are running a stand alone or off the grid system then this isn't that important, but it does remove the problems of keeping the frequency and voltage of the power to the acceptable voltage and frequency. It also negates the need for complex control systems that would be required to keep the engine and generator rotating at the correct speed to give you the correct frequency. It also means that even if you do connect the system to the grid you have a way of recovering some of the cost of the system by selling surplus electrical power.

Regards, masu

Hi I am a secont generation retired mechanic ,I read all the coments but I wanted to sayy one thing, I live in florida now whre you really do need a generator and these portable ones that are sold are not practicle because you can run maybe a few lights ,a portable a/c window unit and watch a little tv but the bigest problem is when there is no power then you can not get fuel of any kind, in 2005 me and my neighbor made a fuel/milk and ice run leaving here five am in the morning to go 400 miles north where there was electric because all the fuel stations here were closed ,no power, no fuel, the only thing availabe was propain, my buddy works for chevy and he took and old carburatered chevy engine that he rebuilt and runs it on propain to power his whole house including his central a/c and the engine just runs at idle which does not make much noise because he put a muffler on it ,this is a chevy 350 out of an old nova he had ,the car was toasted but he kept the engine, now when he first used it he mounted it on a stand rewired it to a push button strat using a self accelarating alternater and he used a 20 fuel tank from another vehicle he got from the junk yard, he told me at idle because he does not like to store gas he ran it until the fuel was used up which he states took 17 days 24/7, thats pretty good ,I would like to do the same but use propain which is available all the time ,in fact I came across a 450 gal tank which is not very big in size ,its like as round as a 16 inch wheel and only waste high ,the propain people told me that would last about 2.5 weeks if a ran it non stop but the last stornm we had here, we had no power for 6 weeks ,the worse part was my mother came to stay during this because she was afraid also she is on oxygen 24 hours a day, she has a machine that is powered my electric and she has some big tanks for emergency ,my point is not to bust your bubble butwe sucked fuel out of every vehice we could to keep her machine going because the oxygen tank companies would not deliver because they had no fuel for there trucks so every morning we made a run 400 miles north were there were no gas or electric problems and filled up as many tanks as we could carry so I don't think going with anything that requires fuel from a gas station is reliable depending on what state you live in ,im from the big apple i'm here to take care of my mother ,not to insult any florida people but things are done slow and backwards here compared to up north and the reason for that is because most companies like sanatation or any other major companies are run by the state not by private companies like here also the union keeps thingss going ,do you know to be a garbage man in newyork you have to take a test ,its the highest pade job ,my uncle is a police captain and makes less then the garbage men, they make anywhere from 150 to 180k per year but keep in mind there also responsible for cleaning the streets-plowing the snow and ice while your still sleeping this way when you wake up the roads are ready to be used

G'day gals, guys, gurus & guest,

Hi Guest, I turned blue in the face and nearly passed out from asphyxiation while I was reading your post.

I've got the perfect birthday/Christmas present for you, its called a full stop or colon ".". Try a smattering of them in your next post, it will prevent your readers from passing out due to lack of oxygen.

You may also want to try hitting the "Enter" or "Carriage" Return key on your computers keyboard one in a while.

Sorry about that I just couldn't help mysefl so frivolity aside lets look at your problem.

It sound like you're living well off the beaten track. Having some way of generating electricity for 24 hour a day 7 day a week isn't a simple task and requires some serious engineering if you are going to do it properly.

The way I would go about is would be to get hold of one of the solid state inverters I mentioned in my previous post. You can then use a whole host of different technologies to generate DC power that is then fed into the inverter and turned into AC with the appropriate frequency and voltage.

Because these units can take raw DC from a hole host of sources you can then build a system that is suited to your location.

For example, since you're in Florida I would hazard to say that you have more than enough sunlight to generate the bulk of you electricity needs during the day. Then at night you could switch back to running the generator to give you electricity at night. You may also be able to use wind and or a small hydroelectric generator if you have access to a running stream of water course. The idea being is that all these technologies get their energy for free from the environment so it will dramatically reduce you're dependence of liquid or gaseous fuels.

It would be interesting to see what you end up doing so may I suggest you join CR4 and keep us posted with your progress. You will also find a wealth of expertise here on CR4 that will more than likely save you from the numerous pitfalls that are involved with the generation of electricity, especially when it needs to be a 24/7 supply.

Regards, masu

Here is how one person did it http://www.youtube.com/watch?v=5tXpUKQ8PMI

If I find future videos then I will put them on a "alternative energy" playlist on youtube at www.youtube.com/radioemergency

Does anyone know of other videos? What are the draw backs of this particular system? What could he do differently? I already read the positive and negative characteristics of gas verses diesel so please do not comment on that. I would prefer to use the innumerous free gas engines at junk yards and family relatives' yards. Could I set up 10 alternators on the same engine and hook them up to the same battery bank?

Initially I thought that trying to get a belt to drive a 10 kW generator was a bit of a push but when I did the maths the force needed to drive the generator with a roughly 15 mm Ø (6 inch) pulley wasn't anywhere near as high as I thought and well within what a single V belt could produce.

Mind you, taking an engine that is probably designed to produce 70 kW plus to drive a 10 kW generator at not much more than idle speed probably wouldn't be that efficient, but I could be wrong so I would like to see some numbers on the fuel consumption and overall efficiency of the setup.