The viability of using automobiles as generators.

Audiomaker

Hi all,

I have created this thread to discuss the viability of factory, as well as slightly modified or fully purpose built automobiles filling the role of generators in our power systems.

As we all know, there are different roles that a generator needs to play in each person’s own situation.

Some are devoted as emergency backup devices only, others supplement off grid or grid-tie systems, while others are the full time prime mover and power source for the user.

What I would like to do here is to is to make a comparison of advantages, and disadvantages of using an automobile instead of a “real” generator in various environments.

I would like, for the sake of this discussion that one may use a factory automobile as their base, or one that has been (virtually) customized specifically for this application, however the idea is to use the vehicle’s engine to produce the lion’s share of the energy.

Some considerations might be:

1. The cost of the automobile, or in the case of a custom vehicle, the cost and difficulty of the project vs a suitable generator.

2. The fuel consumption at the required output vs a generator of similar duties.

3. The longevity.

4. Maintenance frequency, cost, and ease

5. Space considerations

6. Environmental considerations (noise, pollution, visual impact..etc.)

7. incidental advantages or disadvantages of both (insurance, mobility, alternate uses)


So can you replace your generator with a car/van/other, and if so… what would you use or build and why?

techntrek

Re: The viability of using automobiles as generators.

Well, as discussed on your other thread you know my answer. My Prius + UPS system is my primary generator during outages since it burns 0.13 gallons/hr, gives me 4000 watts continuous 6000 surge, is very quiet and doesn't smell like a generator.

Degree of difficulty to do this is fairly high for your average Joe, although your average Joe can install a 1000 watt inverter on the 12 volt system easily (the 12 volt system can do 1000 watts continuous).

For backup uses longevity and maintenance are negligible. Primary power wouldn't be much of an issue IMO.

Audiomaker

Re: The viability of using automobiles as generators.

TechnTrek,
I for one find the use of a Prius (or other hybrid) as a backup generator fascinating. You do however list 2 other generators in your signature so are you ready to sell those off?

Also, the Prius is a pretty fine niche with it's factory included propensity to charge batteries so I don't want to give anyone the idea that this thread is about how to build or buy a Prius. In addition, for someone looking for a generator, the price tag is such that I don't think many people are going to choose one as a dedicated solution vs other options. I mean, you still drive yours right? You don't just park it to charge your house bank correct?

I think for the sake of this discussion, that i would be interesting to see what people would build if they never intended to drive the automobile except in the case of an emergency backup to their vehicle (as sans to their generator).

As an example, I'll tell you what concept I'd be thinking of (and have thought of) when considering buying a nice generator vs building a dedicated vehicle instead.

First, I like the van, or mini van idea.

Before going too far, I would help out the suspension by adding HD springs (or air springs, but they don't like to sit).
I would fill a good portion of the cargo area with about 500ah @ 24v of batt's (even if I had house batteries I could charge). This would allow it to be completely self contained.
I would add a good sized inverter to the interior. In my case, a 6kw split phase inverter, but people could size these as their budget and needs allowed.
I would install (if space allowed) 2 200a commercial truck alternators. You can get these in 24v of course, and that would be a choice to make.
I would replace the belts with serpentine if not already equipped and take a hard look at if there were anyway to drive an alternator with the flylwheel/flexplate, but that's more involved.
Because the engine is already presumable well over powered for the 4.8kw this pair of alternators could produce, I would size the pulleys down to obtain the required alternator RPM at near idle.

I would create or modify a governor to keep the engine at idle RPM (or whatever RPM was required). Possibly this can be done electronically (it is on most modern engines).

I would add an automatic generator start to the engine. Magnum makes one that would work (I've used one).

I would insulate (wrap) all exhaust and likely add a second muffler (cheap).

If space allowed, I would increase the fuel capacity by adding an additional fuel tank.

I'd also throw a small portable generator in there for field work (something that could be carried places the van couldn't reach)

I would add external connections for reverse shore power, and also DC so one could charge a house bank (in a house).

I would keep an eye on things like oil pressure and water temperature to see if things like a HV oil pump, or additional radiator would be required.

I would consider adding an oil "spinner" to keep the oil cleaner than the filter can (big rigs use these).

...and finally, I would mount 4 PV panels to the top of the van...with charge controller...etc.

My vision of this "portable power station" isn't very creative. The idea is essentially to take what you might find in an off grid cabin, and stuff it in a van instead.

Why? Because a good backup generator can run upwards of 10 grand (think Onan/Generac/etc).
I believe I could build something like this for less than that, and my power requirements are such that I don't need 10-15kw in an emergency, nor to charge house batteries in a non-emergency.
I also think that because you are creating an "inverter generator", that fuel consumption could be lower than gensets forced to run at 1800, or 3600rpm continuously no matter what the load.
In addition, I believe that the modern car engine is better designed than almost any factory generator engine, and that as long as you maintained oil pressure, that one would last longer starting with used, than a new generator motor.
For myself, I'd look for a good fuel efficient Honda or Toyota mini van. A VW like the Eurovan can be had in diesel. I'd have to look into the full sized van idle fuel consumption numbers to see where they land because those American vans can also be gotten in diesel.
In the end though, I am less biased towards diesel in this application than I am with small generators. Gasoline engines are reliable, small gasoline generator motors generally are not up for long term tasking.

All of this said, someone else might have a smaller, or larger concept. Theoretically you could empty out a Honda Civic and perhaps end up with a suitable and even more fuel efficient rig.

Thoughts?

mike95490

Re: The viability of using automobiles as generators.

Any "conventional" auto, even HD trucks, only have 100 - 150A alternators in them.

At idle speeds, they may put out 30% of max, so you are idling a V-8 or 6 cyl for a 50A power source.

At 12V, that's a whopping 650 Watts. Till the alternator overheats and dies. What's your gas mileage stopped and at idle ? Lousy.

It's an OK - jury rig for once in a while, since 12V inverter systems are pretty much limited to 1Kw.

BB.

Re: The viability of using automobiles as generators.

Balmar is known for Marine/heavy duty alternators:

http://www.balmar.net/

And they have charge controllers that are designed to charge lead acid battery banks (multistage chargers).

-Bill

Audiomaker

Re: The viability of using automobiles as generators.

mike95490 wrote: »

Any "conventional" auto, even HD trucks, only have 100 - 150A alternators in them.

At idle speeds, they may put out 30% of max, so you are idling a V-8 or 6 cyl for a 50A power source.

At 12V, that's a whopping 650 Watts. Till the alternator overheats and dies. What's your gas mileage stopped and at idle ? Lousy.

It's an OK - jury rig for once in a while, since 12V inverter systems are pretty much limited to 1Kw.

That Mike, is exactly what we're looking at here.

My experience with small portable generators (say 2.5kw Hondas and such) vs idling a small car with a 4cyl engine is that the car uses a similar amount of fuel overall when tied with an inverter/batt system, and costs about the same.

In it's most basic formula, I could present this for critique:

1. Brand New Honda EU generator = $1000

1 Used, maybe ugly Honda Civic plus 3kw inverter and a pair of deep cycle batt's = $1100 ???

I personally would like to see that head-to-head battle. My money would be on the car, since after all, it was maybe a $10,000+ machine at some point, with all the tech' that goes with that.

I would also bet that the used (say 100,000mi) water cooled engine will outlast the brand new Honda generator engine @ idle, or at whatever it takes to produce the same 2.5kw as the portable.

I'd also argue that the tech' of the car engine allows it to get better fuel economy per hp even though it suffers from larger parasitic loads (such as power steering pumps) and indeed it's own rotating mass and friction, basically making it a wash.

A little net research at first glance seems to reenforce this idea with Honda Civic's having idle GPH rates at .11 to .13 gph. This allows a bit of a buffer even adding a few horsepower of alternator to the mix in order to reach typical generator fuel consumption numbers (our moderator gives us 1600w @ .25gph. My own diesel gives me 1750w @ .16gph). So the Civic in this case has somewhere between .03 and .05 gph to spare towards electric generation to reach *my* generator's numbers (which is unfair because diesel has more BTU per gallon), and more than double to reach a darned good little generator's (EU2000) spec's.

There is no question about one thing. The GPH at required kWh are going to matter a lot. There is not going to be much question that idling a Detroit Diesel 6-71 to create a couple kw to compete with a pull cord portable is going to be an inefficient endeavor (or even a V8, or V6..etc), but there are pretty fuel efficient 3 and 4 cyl car engines out there that wouldn't flinch at running a reduced pulley diameter alternator.
As far as car alternators burning up, there are many grades of alternator, and many can be had in "severe service" forms.

BB.

Re: The viability of using automobiles as generators.

If you have an ODB or ODBII equipped car and an ODB meter for older cars--You can read the mass air flow from the car's computer and calculate fuel flow:

http://www.windmill.co.uk/fuel.html

That would give you some better instantaneous estimates of fuel usage for testing.

-Bill

Audiomaker

Re: The viability of using automobiles as generators.

Here's another link.

24v alternator @ 80% efficiency.

http://delcoremy.com/Alternator-Models/55SI-High-Output-Brushless-Heavy-Duty-Alternator.aspx

KenZ71

Re: The viability of using automobiles as generators.

I have no facts to back this up, but...

Given how long hybrids have been on the market it should be fairly easy to find one in a salvage yard with extensive body damage due to an accident that could function as a generator. Of course you would lose the portable component.

Blackcherry04

Re: The viability of using automobiles as generators.

I guess where you lived would depend on some requirements. The Po Po would be on you, a vehicle has to be inspected, licensed, have at least Liability insurance to be on your property where I live. You'd be in the hole $300 a year before you started with a junker. On the other hand, if it was driver and you could get the output you need, why not. I have a Toyota Camry engine pulling a 20 KW head that uses 2 gph @ 1800 rpm and that ain't cheap.

Audiomaker

Re: The viability of using automobiles as generators.

Blackcherry04 wrote: »

I guess where you lived would depend on some requirements. The Po Po would be on you, a vehicle has to be inspected, licensed, have at least Liability insurance to be on your property where I live. You'd be in the hole $300 a year before you started with a junker. On the other hand, if it was driver and you could get the output you need, why not. I have a Toyota Camry engine pulling a 20 KW head that uses 2 gph @ 1800 rpm and that ain't cheap.

Am I understanding that you have a Camry engine in front of a regular 20kw generator head governed @ 1800rpm?

If so, 2gph might not be bad at all depending on how many kw it was producing.

I believe I saw once, some newer model import car motors being used on stand alone generators (a company was making them). I'll have to track that down.

Sometimes I feel like there's this wall of denial that for the most part, a generator is just an engine strapped to an alternator. Just as in stand alones, the two need to me matched, and are scalable for output, but also as in stand alones, a large engine is perfectly happy powering a small load (my 7kw gen set putts along producing 1k all the time).
I don't think the engine/alternator combination really cares if its on a cart, or a trailer, or built inside a car or van, in fact... a $500 Astro van cargo area is by far more elaborate than most generator "quiet" enclosures.

Most generator companies use what amounts to tractor engines. I think this is due to cost, but simplicity is a plus too. Of course if you put that same output tractor engine in your car, it would probably get lousy fuel economy and the EPA would be screaming...etc.
I just don't think putting late model car style engines (read high dollar tech engines) in generators is viable to the generator manufacturers. I think it is cost prohibitive (adding many thousands of dollars to the cost over a tractor engine).

That doesn't mean we can't.

inetdog

Re: The viability of using automobiles as generators.

Audiomaker wrote: »

but also as in stand alones, a large engine is perfectly happy powering a small load (my 7kw gen set putts along producing 1k all the time).

True unless the engine is a diesel.
Also, running with the throttle nearly closed will not be as efficient as running at a higher power output. Not a big deal, but a smaller engine will more efficiently supply a smaller load.

techntrek

Re: The viability of using automobiles as generators.

Audiomaker wrote: »

TechnTrek,
I for one find the use of a Prius (or other hybrid) as a backup generator fascinating. You do however list 2 other generators in your signature so are you ready to sell those off?

Also, the Prius is a pretty fine niche with it's factory included propensity to charge batteries so I don't want to give anyone the idea that this thread is about how to build or buy a Prius. In addition, for someone looking for a generator, the price tag is such that I don't think many people are going to choose one as a dedicated solution vs other options. I mean, you still drive yours right? You don't just park it to charge your house bank correct?

I think for the sake of this discussion, that i would be interesting to see what people would build if they never intended to drive the automobile except in the case of an emergency backup to their vehicle (as sans to their generator).
....

Actually, yes. I've mentioned here before if I had to do it all over again I wouldn't buy the big Generac. I originally bought big to power one of my 2-ton A/Cs (which I've never needed to do). With no Prius in the picture I would buy one cheap 6-8kw contractor screamer to run my well pump and water heater, which would only be used 2-3 hours per day. It would also be my backup for the smaller genset. Then I would buy the Honda inverter-genset I have now, maybe just the 2000 watt model, for the base loads 24/7.

The Prius is great for a backup power supply because I don't have to pull it out of storage once a month to exercise it, or service it separately. It gets exercise every day and maintenance when it goes to the auto shop.

I have considered converting a wrecked Prius as a dedicated generator, which I've mentioned here before, but I've also talked someone else from trying it because there are too many variables to get it to work right. It would be much easier to build your own with a standard generator, battery, inverter, charger, and then your own control system.

I would not convert a standard vehicle for generator use, though.

Audiomaker

Re: The viability of using automobiles as generators.

techntrek wrote: »

I would not convert a standard vehicle for generator use, though.

Might I ask why? I mean, you have a unique perspective, but what if you couldn't go the Prius route. Would you still not convert a standard vehicle after appreciating the advantages you have had?

inetdog

Re: The viability of using automobiles as generators.

I would suggest that the standard vehicle is not designed for frequent automatic start-stop operation of the engine.
Just one example: On the Prius, there is a pump to store hot coolant in an insulated container when the engine is stopped, so that it will get to efficient operating temperature sooner when restarted.

Audiomaker

Re: The viability of using automobiles as generators.

inetdog wrote: »

I would suggest that the standard vehicle is not designed for frequent automatic start-stop operation of the engine.
Just one example: On the Prius, there is a pump to store hot coolant in an insulated container when the engine is stopped, so that it will get to efficient operating temperature sooner when restarted.

Hmm... could one add that?

I dunno, my RV generator (which is powering an inverter/charger) automatically runs a cycle about 5-6 times a day.

My Astro van (ie, my current daily driver) is getting started and run around town more like 10-15 times a day.

inetdog

Re: The viability of using automobiles as generators.

Audiomaker wrote: »

My Astro van (ie, my current daily driver) is getting started and run around town more like 10-15 times a day.

And that is pretty heavy service in terms of engine life.
Each time you start it and warm it up you are getting extra wear and tear on the engine parts compared to the same total length of time in one run.

Audiomaker

Re: The viability of using automobiles as generators.

inetdog wrote: »

And that is pretty heavy service in terms of engine life.
Each time you start it and warm it up you are getting extra wear and tear on the engine parts compared to the same total length of time in one run.

I completely agree, but it did go over 200k before needing to swap a 350 TBI into it

john p

Re: The viability of using automobiles as generators.

I would suggest that the standard vehicle is not designed for frequent automatic start-stop operation of the engineBut most survive this no problems..Example a taxi would be restarted as many as 120 times every 24 hrs.In Australia as example where up until recently most taxis were ford s using a 4 litre 6cyl engine ..The usual end of life is 1 million klms . on one engine no rebuild..I have a 17 yr old Mitsubishi strada/strada, 4cyl 2.5 l diesel over 200000 klms and its been also used 500 hrs as a 12 v generator when no sun for solar panels.. still un rebuilt engine and only this month replaced alternator.. .

Audiomaker

Re: The viability of using automobiles as generators.

Well the root of all of this for me, is that more than once in my time I've survived on the power from a car.

Usually (almost always) it was because my backup generator had failed (and decent generators too...usually Honda).

It's like, crap, the generator just burned up and I need to hook up my inverter and couple batteries while I try to fix it.

The repeated feeling I remember once getting another portable generator, or getting the one I had fixed, is that I kind of didn't want to go back to the portable.

During those low energy consumption hours, I've spent many hours enjoying the peace and quiet of powering my minimums via vehicle, and also daydreaming about how I wish it (the car) could do this, or that a little better...etc.

For instance, I'd wish for a more powerful alternator, and since I was turning the car off at night to save fuel and making due with a couple grp 31 batt's, I'd wish that it had a bigger bank of batt's and automatic start/stop.

I also made note that I wasn't spending much of a difference on fuel weekly, I just wasn't filling 5gal tanks and refilling as often, but at the time I was poor enough to notice if suddenly I was spending twice on fuel. I wasn't.

At the same time, I was still generator minded, so I was shopping continuously and you're sitting there on Craigslist going "$900?? That's more than that mini van powering this computer is worth"

I've also had my portables refuse to start with their little cheaply made carb's, but that darned mini van with it's EFI would start after sitting for 6 months...with 6 month old gas.

I owned and ran portables in the 2.5kw to 10kw range. Some electric start, some not. It was a big PITA to go out to my home made enclosure and shut off the generator when 10pm rolled around, and it was a pain to fill them every day (sometimes more than once), and when all was said and done, I wasn't using 10kw most of the time... not even 2.5kw most of the time.
In fact, in my current RV setup, my 7kw diesel only uses about 2.5kw to "bulk" the battery bank, and with a 6kw inverter charger hooked to that, it's very livable.

For this reason, I feel I could get by with 2.5kw of generator as long as I had a battery bank large enough to store it up.

Add to this math that I feel a 50-90hp car engine should have no struggle turning a 100a 24v custom installed alternator, that 2400w seems like a workable amount of power.
Remember, we're not talking about driving the vehicle while it generates power (although it could be done). The only fuel economy numbers that matter are those while stationary.

This "power station" vehicle is a project that I'd like to take on this year. Gathering opinions and experiences from other people is certainly helpful. There are a lot of choices that can be made (model of van..etc).

solar_dave

Re: The viability of using automobiles as generators.

Now that the Chevy Volts are coming off warranty perhaps someone will try a direct attachment to the LI battery in one of those. I have one of ours rigged with a 12V setup off the regular battery and it works pretty darn good and engine cycling is minimal. The engine/generator capability is pretty large if I remember correctly.

bendorfold

Re: The viability of using automobiles as generators.

BB. wrote: »

If you have an ODB or ODBII equipped car and an ODB meter for older cars--You can read the mass air flow from the car's computer and calculate fuel flow:

http://www.windmill.co.uk/fuel.html

That would give you some better instantaneous estimates of fuel usage for testing.

-Bill

Even easier, plus you won't have to pay (for those who do) to get your code cleared, is the UltraGauge ( http://www.ultra-gauge.com/ultragauge/ ). It has Instantaneous and Average G/H, TTE (Time To Empty) plus many others (depending on your vehicle). Plus you get $9 back if you send (mail) them your cars information (that's how they gather new data, they pay you for it). I set my 'Fuel Display' panel like this: