Efficient generator #2

Alternative energy sources
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The usual. As I have two large solar PV systems here, and my lab assistant just put one in, and others are interested in things like this, here's where that stuff goes. This is mostly for things that work now, not "gee someday a fusor will do this" -- we know that, but it's not someday yet.
The hope is to save anyone embarking on this sort of thing a lot of wasted time and money, as at least I have been off the grid since 1980 and have had a lot of practice (and made mistakes you won't have to).

Efficient generator #2

Postby Doug Coulter » Thu Sep 08, 2011 11:24 am

While sometimes you need a real serious ability to charge batteries, that's not the norm. (But see this link). Usually the sun is giving you at least a little something, one is careful not to run the batteries very far down in the first place without taking some action, and so forth. Bigger generators, like for instance my Hobart welder/generator really eat the gasoline, and in that case, aren't very efficient either. My first efficient generator, a Honda 6.5hp driving the DC generator geared so the engine is running at the torque peak, is also on the large side, producing around 100 amps @ 30v when running in efficient mode -- at the torque peak and throttle wide open for best net compression ratio and cleanest burn, least pollution due to unburned charge getting through the engine during valve overlap (in fact, it's over 100% volumetric efficient in this mode due to manifold tuning). But 100 amps is still a lot, when my campus needs say 20 or so when we're running computers and watching TV (with the other loads like the freezer etc running as required). So our active-house average is in the 500w range (it's one heck of a computer, this one, and on all day every day). I need those big generators sometimes when things have gotten real low, after all, the batteries are in the 1500 amp hour range, so a full charge from down takes awhile even with a big generator.

But that's way not the norm. More often is a situation where we just didn't quite make gain on the day, and tomorrow is going to be cloudy too, and we want to enter the next day AM with plenty in the batteries (microwave breakfast etc and just never have to worry about it). Thus, a smaller generator that just keeps up, or makes a little gain at night was needed, and of course, I want that efficient as well.

It turns out that Honda has made some advances in this field. What they have done is to take some of the new tech in IC engines and apply it to a tiny one (95 cc). This broadens the envelope over which its very efficient quite a bit. Better fuel control, spark control -- no longer the fixed timing magneto, better all around, and now, computer controlled. To compliment this, they use a DC generator, followed by an inverter, so the engine doesn't have to run 3600 rpm all the time to make 60hz AC, and the computer can simply throttle it up and down depending on load requirements. A 95 cc engine running in this mode uses one heck of a lot less gasoline per output than say, your average efficient 3.5kw generator at the same load, spinning full speed.
So that was a start on this project. I bought one of these Hondas (way high priced, but that's the early adopter fee) and took it to the testing lab of real life. For starters, I just used it like I did the 3.5kw AC generator - using a Trace (now Xantrex) inverter as the charger, which lets me adjust the load. However, the fancy charging scheme in the Trace, which varies its power requirements all over the map doesn't work well with the Honda in "eco-throttle mode" -- you get battling computers and a kind of divergent operation, and it's kind of stressful on the Honda to have the load going from max to zero to inbetween every few seconds.
HondaInvGen.jpg
The new Honda. These are stack-able, by the way, which is something else cool about using an inverter internally.

HondaFP.jpg
Front panel of the Honda


So, (and BillF found this) I ripped apart an old industrial forklift battery charger we got surplus, because its computer stuff had failed. It had a really nice ferro-resonant transformer good for 24v battery charging with about 30 amps max output when the output voltage is low. I swiped the transformer out of it, and replaced its original diodes with some nice 200 amp shottkys, and am now testing that. It seems made to order for this job so far, quiet (when under load, which it's hardwired to be), efficient, predictable load on the input, nice taper charge on the batteries, the current goes down with rising voltage a lot more than it would with an unregulated charger. The Honda nicely throttles down when driving this, and is nearly silent, while using almost no gasoline (something like 12 hours per gallon) and everything runs nicely cool.
FRCharger.jpg
The charger. Amps are low because I did this on a fairly sunny day and battery volts were high already.


I'll get some more data on this as time goes on. Another nice thing about this new Honda -- it's light and can be carried with one hand, even by my wimpy self. This should make a perfect adjunct to various things I do around here that would like portable electricity -- I have an electric chain saw I like a lot better than nearly all gasoline ones (and I have a ton of experience there, FWIW -- the torque on the electric, quiet, light -- eat your heart out Stihl or Husky, no comparison). I have an electric water pump that with my truck, gets water from anyplace there is water to get into a big tank for later use, an electric string trimmer and so forth. Most of the time, I can use all those things off either the truck inverter or a long extension cord, but the saw, not so much, and you have to at least cut the wood into sizes that can be moved, even if you're going to make it firewood and split it back at the home station. So there's a need (or desire) for power in the deep woods, and this does it great.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Efficient generator #2

Postby chrismb » Thu Sep 08, 2011 11:47 am

I was looking at generators a couple years back because our power here (on the grid, mind!) was soo bad I felt I needed some back up power just in case. (Basically, my boiler needs a bit of juice to go, so when we were without power for a few days during one cold winter, then again just a week later, the 'protect-the-family' animal instincts were kicking in as it was hitting 5C indoors, and same temp for water!!)

I went through an assortment of specs, and this Honda you got, which had just come available in Europe then, was just waay in a league of its own.

I actually hassled the elec co. enough that they did a £70k electronics upgrade on the local substation 'for me', so though I didn't buy one, it stood out as a very pricey, but eminently good value purchase that I was just about to put my order in for one or two.
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Re: Efficient generator #2

Postby George Dowell » Thu Sep 08, 2011 12:14 pm

Thanks for the updtate on the micro generator.
Looks real interesting.
I sold off my home made communications trailer which contained my 4 kW gasoline genny.R eplaced that with a 16 kW PTO driven generator for use with my Ford Diesel tractor (Ford Motor was a client).

http://www.qsl.net/k/k0ff/Trailer%20Tower/

We are on the grid but we are the last house on the line!

Geo
Last edited by George Dowell on Thu Sep 08, 2011 12:49 pm, edited 1 time in total.
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Re: Efficient generator #2

Postby Doug Coulter » Thu Sep 08, 2011 12:37 pm

Chris, for your type situation, the Champion 3.5kw (peak) AC generator is the best price/performance on the market by a good way. They go for $329 here. It uses a Chinese copy of a Honda OHV, high compression engine (and it's a high quality copy), has a digital voltmeter, starts no matter the weather, and really sips the gasoline. If, that is, you can stand to have it running at 3600 rpm all the time, even though it's pretty darn quiet. They use about a 2 liter muffler and a good silencing air cleaner. It's a bit non portable of course, and will run 12-14 hours on a 4.5 gallon fill at light loading. And that's the issue here -- that light loading really calls for something smaller running closer to full output to get the thermodynamic efficiency, unless of course, it's a diesel. Maybe we can talk BillF into posting pix of the setup he just built with that Lister diesel and big ol generator he has shown me - it's a thing of beauty that will probably outlive us all, running at a mere 900 rpm or so and using a couple of big serpentine belts to drive the gennie. If he puts on the exhaust system I'm recommending, it will be very quiet too, and of course, burn almost any flammable liquid in the bargain.

But in a situation where I have submarine batteries taking care of any and all peaks, I don't need such a thing myself, so this looked good. The proximate reason to get the high priced honda was my Champion was down for repairs (waiting on parts) right when we have the first week of darkness since last February, and the stores had all been stripped bare of the good-for-price stuff of appropriate size. Those 8hp and up guys -- no use for most people unless you're running central AC, a hot tub, electric cooking, all at once (and most around here who have those also have huge propane tanks to run them -- and only find out too late how fast they can go through fuel).

I've got a spare one of those p-51 aircraft DC generators, and a 24 hp tractor with PTO, and I've looked at doing that. It's not so special in economy, but the portability is nice. Things that haul themselves around are always nice for handling the unexpected. The p51 gennie will make over 200 amps if you can supply the shaft with enough horsepower, so it can weld pretty decently too.
The generator I made off one has flat worn out 3 honda engines (in the 10k hour each range) -- and I took the generator down as I assumed the brushes had to be toast by then. Nope, not even close! That WW-II fighter plane stuff is pretty darn hard to beat! I've been using that off and on since long before this building was here as you can see in this link: http://www.coultersmithing.com/OldStuff ... erator.htm

For those wanting quiet power (EMI wise) Xantrex makes some very, extremely nice inverters. The 4024 model (with prefix depending on age) is a sine wave output synthesized with a 3 "trit" power D/A converter. It's what runs most of my campus and is hidden there partly by the voltmeter in the picture. Just dead reliable. I have an older 3524 modified SQ wave inverter as well, which now is relegated to running my 10 hp air compressor and a couple other machine tools, it sits there in "wait for a load" mode most of the time. It makes quite a bit of EMI when running, but if anything, induction motors like that waveform better than they like a sine wave - lots more torque available. Of course, then you need batteries....I have tried locomotive NiCads, but frankly, they stink in this service -- too much voltage range over the charge range. I'm now using Rolls-Surrette lead acid batteries for the main system, and they can't be beat with any current affordable tech so far. These are box in a box -- 2v cells, and really "built", with a 25 year guarantee. I've had this batch a few years now, and they are still like-new in performance. The more common L-16's I used to use would show serious deterioration by now under the same conditions, though I've made them live 8-10 years with care. That appears to be an area where you get what you pay for, just like Solar panels. Don't go for the cheap thin-film new-tech ones -- they have a huge failure rate that's responsible for a lot of the newer companies going out of business. Google is finding out about that one the hard way. Good old thick polysilicon with thick glass, tempco matched backing, thick aluminum frames -- that's what you want. Mine are Solarex, which is owned by BP petroleum...if that tells you anything about "peak oil" -- they know! Some of my panels are going on 30 years now, still meeting spec despite hurricanes and hailstorms and daily cycling in temperature. When you look at the price of a quality window the same area, the price no longer looks so high. For a home backup, a couple of those panels, a couple gel cells and an inverter makes a darned nice UPS system -- and you can trickle charge them when you have power with a wall wart if the sun isn't doing its thing. The advantage of course is that such a system is silent in operation and has other uses.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Efficient generator #2

Postby chrismb » Thu Sep 08, 2011 1:35 pm

If I was serious about going off grid, and had enough cash, I am sure I would end up with a WhisperGen [yet another demonstration of NZ tech!...].

I can't stand noise, alomst any sort of noise gives me migraines on the wrong day, so the Stirling engine CHP WhisperGen looks to me to be as good as it gets.
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Re: Efficient generator #2

Postby Doug Coulter » Thu Sep 08, 2011 2:47 pm

You mean someone has actually gotten a practical amount of power out of a Stirling engine, not just hype and BS? This, I'd love to see a link to. That's like hearing a polywell is actually making enough neutrons to measure in someone's actual build of one in the real world -- so far, all hype, no fusion.

I just found out what happens when the sun comes out while that Honda + ferro resonant charger is running, as I was outside making a trunk fitting for the Cruze. The thing just goes to idle, as the charger stops drawing current right as the battery voltage hits 29.5 -- perfect! That one's a winner. I may make another to parallel with it for those times I need a little more juice.

This noise wouldn't bother you unless it was in the room with you, the thing is very quiet, and it's all LF, no jizzy vibrational HF at all. I could probably tolerate it indoors if I hooked the exhaust to a bellows pipe to run outside -- then I'd get the free heat too (I have done this in the past, putting the gennie in the basement, but there it was hard to do good maintenance on). That's a bit dangerous, of course, especially with something as clean as this -- can't smell the CO, but theres nothing else you can smell either in the event of a leak.

Oh, for what it's worth, the all time high hits -- still 100 or so a day, for this site, are to the original "efficient generator" page, which I just linked again above. This is evidently a hot topic or search phrase...
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Efficient generator #2

Postby chrismb » Thu Sep 08, 2011 3:57 pm

Yes, the WhisperGen is a working, well-tested unit. There was actually a mass-trial here in UK for it a few years back. Several hundred homes in Norfolk (or somewhere like that) were given the opportunity to have them fitted by British Gas (one of the main gas untility companies {obviously!} - used to be the nationalised supplier), these being gas powered units running of mains gas. They can produce around 1kW electricity and 10kW heat, or something like that. Size of a dishwasher, apparently, so they fit into a standardised slot in your kitchen and they make as much noise as a quiet dishwasher too. Just what I've heard, I can't vouch for that.

Don't know all the details myself. Just do a search for 'WhisperGen' and you should get a pile of reviews in addition to their own whispergen.com website.

Yes, the Honda 'i' generators have such a good reputation here similarly, it's why they cost almost as much for 2nd hand units as new, you can't find any for discount. Make the rest look agricultural.
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Re: Efficient generator #2

Postby Doug Coulter » Thu Sep 08, 2011 5:45 pm

Well, if you get 1kw E for 10kw calories, it's far, far less efficient than the Honda then -- that's getting right around 42% of the original energy into electricity if it's as good as my more accurately measured belt drive DC one. Yes, that's much better than an auto (20-30%), because unlike an auto, you never idle, and you run the engine at peak efficiency at all times (which is the whole point of a hybrid auto). It's right up there with the very best steam plants, as we are using a far more high end fuel - it should be. At the prices you guys pay for gasoline (about 4x here I think), I'd suspect that's pretty major to need 4x the fuel for the same output, unless you just need the heat, but burning gas or gasoline for heat is a real waste of the stuff -- wood and coal are a heck of a lot better in BTU/buck. And of course, using electricity for heat, even with a heat pump, is just totally dumb efficiency wise.

Now, living in/near London and having kids, you're probably deaf enough already not to be bothered by the noise of a Honda (or the champion) if it's not in the room with you. It's less than most dishwashers I grew up around (don't have one now, or well I do, her name is Marlene - a noisy dishwasher). Where I live the noise level is quite a lot lower than any city -- or for that matter, less than it is 20 miles from a major city, except when the insects get going. It gets down to below 40 db absolute here all the time, lower in winter, freaks some people out, and I have to turn on a fan or other small noisemaker in the visitors quarters so they can sleep! You can actually go all day long hearing no man made noise at all, unless you make it - hear your own heartbeat and stuff like that. Here, one doesn't have to raise one's voice to communicate with someone standing touching the thing while it's running. It's quieter than some room fans.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Efficient generator #2

Postby chrismb » Thu Sep 08, 2011 6:44 pm

Doug Coulter wrote:Well, if you get 1kw E for 10kw calories, it's far, far less efficient than the Honda then.

I think it is ~>90% efficient, given the 'right' mix of elec and heating requirement. That is, it can give you 1kW and some heat, say 2 or 3 kW, or 10kW of heat if you need it and 1kW power. You'd need to read the literature on it. I'm not entirely sure, but it is a CHP system so is ultra efficient, so long as your demand matches its output.
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Re: Efficient generator #2

Postby johnf » Thu Sep 08, 2011 6:48 pm

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