Nigel Calder: Replace Your Generator by using your main engine
- Thread starter Genesis V
- Start date
Hey, Jim, no good adding to a supposed quote of Capta! He never said "600Amp 120VAC." In fact, no one did.
I just took 8kW and divided it by 13.5V to come up with 600A.
Of course, you are right. What's it they say about computers? "Garbage in, garbage out." Gotta put in all the info to come up with an answer.
If you take any quote and interject [ bracketed]. It indicates the Bracketed item was interjected by some one else for clarity or other reasons. It is called [SIC] or ...
"It is generally placed inside square brackets to indicate that it is not part of the quoted matter."
So...
@capta asked a question about Horsepower.
Since one surely knows that all Power can be converted to other Units of Power.
As most Engineers learn quickly, there is Power losses
Most Diesel Engines are fairly high efficiency engines, mainly do to high compression ratios.
They are HP sized for about 80-85% of WOT. That is their "sweet spot".
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So what does this have to do with this post?
They are proposing using that "extra HP" , not used, to be a replacement for a Generator.
As noted in my Post#6 and @kloudie1 doing his engineering homework.
So duhhhh their main engine is the Generator, or trying to steal the last bit of it HP while motoring.
They would better off charging their Super Batteries with a Wind Generator.
Jim...
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I agree. I didn't find weight info either, but from the FAQ "You really need at least 10 kWh of lead-acid batteries to optimize the system". Weight matters. A standard fixed generator will weigh hundreds of pounds, but is designed to run whenever and doesn't mandate a massive bank of batteries. (In most use-cases the installation of a generator allows the owner to reduce the size of the house bank).
IMHO, I'd rather have a massive solar array and adequate house bank, and try to get by without air conditioning. But I acknowledge there are some times/places where AC is nice to have. If designing the system to run air conditioning on the hook, adding a sound-shielded generator makes more sense to me.
Everyone is still talking lead acid batteries here. The costs for lithium ion batteries are decreasing all the time. The work function of these batteries appears to be ideal for sailing application. There is still limited information I'm finding on using that technology in sailboats and the video did mention they are working on them. Using that battery technology will be a game changer from what I can see. Optimization of lithium ion battery banks is a subject I would very much welcome. I don't know if this new generating system might just be perfect based off lithium ion batteries. But whoever breaks that nut will definitely have a highly desirable system.
dj
dj
Part of the deal with the battery bank in this system is it being able to take a BIG whallop of charge quickly.. The lithium batts are better suited for that, but the huge lead acid bank they talk about could work well with it too.. With Li batts, the entirety would be lighter than a separate stand alone generator system and probably burn less fuel overall.. except if taking the case of running a generator all night to have air conditioning.. More pertinent to us folks living in the south 90's.. (90 days of 90+F at around 90% humerditty) 
The use of this is way beyond what Im familiar with to judge how useful.. but what I see is that the solution here was about improving efficiency for electrical power generation.
Some inefficient operating points are noted. If you use the main engine to generate electrical power at low rpm, its not efficient. If you use some sort of genset at a power load way lower than rated power, its also inefficient.
But if you use a genset at near its rated loads, efficiency may not be that bad. And.. its generating AC power so if one of your loads is air conditioning, it may be fairly efficient compared to running air conditioning from an inverter off a 48 volt DC bank. Battery charging is always acceptance limited but if you can charge batteries at near full acceptance and this is matched bank size to battery charger to genset, this could also be fairly efficient.
So. what I wonder is how much Diesel is anyone using to generate electrical power? You are not stressing anything mechanical by being inefficient, you just waste some fuel. But if that particular amount of fuel is pretty much "in the noise", and you further reduce "in the noise", did it really matter. This is the part I really have no idea about.
So.. is this efficiency for electrical power generation important? Or is this a very nice solution, but there really was not a problem that needed to be solved in the first place at least for most of the applications here (recreational boating).
Some inefficient operating points are noted. If you use the main engine to generate electrical power at low rpm, its not efficient. If you use some sort of genset at a power load way lower than rated power, its also inefficient.
But if you use a genset at near its rated loads, efficiency may not be that bad. And.. its generating AC power so if one of your loads is air conditioning, it may be fairly efficient compared to running air conditioning from an inverter off a 48 volt DC bank. Battery charging is always acceptance limited but if you can charge batteries at near full acceptance and this is matched bank size to battery charger to genset, this could also be fairly efficient.
So. what I wonder is how much Diesel is anyone using to generate electrical power? You are not stressing anything mechanical by being inefficient, you just waste some fuel. But if that particular amount of fuel is pretty much "in the noise", and you further reduce "in the noise", did it really matter. This is the part I really have no idea about.
So.. is this efficiency for electrical power generation important? Or is this a very nice solution, but there really was not a problem that needed to be solved in the first place at least for most of the applications here (recreational boating).
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Yes, but the "big wallop" implies running the main engine at significant speed (way above idle) to generate that HP. I don't have AC currently but thinking hypothetically; that would wake me up (and disturb others nearby). So the system would need to be sized with adequate batteries and inverter power to run AC all night. Many of us struggle to keep up with running a small Danfoss 3Amp refrigerator on the hook, nevermind AC.Part of the deal with the battery bank in this system is it being able to take a BIG whallop of charge quickly.. The lithium batts are better suited for that, but the huge lead acid bank they talk about could work well with it too.. With Li batts, the entirety would be lighter than a separate stand alone generator system and probably burn less fuel overall.. except if taking the case of running a generator all night to have air conditioning.. More pertinent to us folks living in the south 90's.. (90 days of 90+F at around 90% humerditty)
8kw does not require 82hp. You could never put 82hp through that belt. Probably requires 12 to 16hp in the real world.
735w = 1hp @ 100% efficiency.
735w = 1hp @ 100% efficiency.
A little math.
8000 watts / 48 volts = 166.67 amps
8000 watts / 735.5 = 10.88 HP
10.88 HP / .85 (efficiency) = 12.8 HP you will need a little extra for surge loads
8000 watts / 48 volts = 166.67 amps
8000 watts / 735.5 = 10.88 HP
10.88 HP / .85 (efficiency) = 12.8 HP you will need a little extra for surge loads
Wouldn't a more practical and cost effective solution be to pair a small generator with an inverter that has a generator support option. The inverter runs in parallel with the generator. The inverter supplies power when the generator cannot keep up, like when the AC compressor kicks on. I know several manufactures offer inverters that will do this but they aren't cheap.
This would allow you to use a smaller, lighter, more fuel efficient generator. You get to keep your standard 12 volt bank and your high output alternator. You wouldn't be required to run your main engine as a generator. This system seems to have most of the benefits without all of the complex hardware. This is also a system that you could build a piece at a time and maintain it because you built it.
Could even be done with portable generator, like a Honda 2000 or 2200.
I've never built a system like this, I could be wrong.
This would allow you to use a smaller, lighter, more fuel efficient generator. You get to keep your standard 12 volt bank and your high output alternator. You wouldn't be required to run your main engine as a generator. This system seems to have most of the benefits without all of the complex hardware. This is also a system that you could build a piece at a time and maintain it because you built it.
Could even be done with portable generator, like a Honda 2000 or 2200.
I've never built a system like this, I could be wrong.
You hit the nail right on the head. I don't care about fuel efficiency. My engine is rated at 0.42 GPH at 2500 RPM (cruise is 2500 to 3000). What I'm concerned about is noise, having to attend the main engine as it's charging, and the amount of time proper charging takes. I do care about charging efficiency, to reduce unnecessary noise, and speed up the charging process.
What I would really like, and I may indeed design and implement some day, is a dual-mode engine controller. One mode is propulsion, which is normal propulsion operation, but a simple one-button start. I purchased a generator controller years ago with the intent of doing this on my Catalina. The other mode is generator, where you're sitting at anchor and just need to charge batts.
I've noticed recently that during bulk mode my bulk charging current drops off as the voltage comes up. I don't think this is a desired effect. I thought one wanted max current until you hit the accept voltage. (Max current is according to the recommended maximum charge current for the bank, with consideration for max alternator current.) I don't know why it drops off, maybe the alternator needs to spin faster for 100A at 14.0V than it does at 100A and 13.5V. Or maybe it's just a design shortfall in the Link 200-R. I'v also noticed that once I hit accept, I can slow the engine down quite a bit while maintaining the 14.8V accept voltage. So, what I think would work well is a generator mode system where neutral is sensed, for safety, and then the engine speed is controlled by the charging system, just as the field current is: controlled together, to achieve the most engine speed efficient charging possible.
I could have a pair of buttons by my electrical panel: generator on, generator off. I could also set it to run automatically, especially for when I'm sailing, and maybe even have a rotary selector to select how far I want to discharge batts before generating, and also set preferred times of day, and times not to run - like when we're sleeping. A manual lockout for when we're entertaining, or swimming, etc.
(How do you guys feel about the main engine running for generating while you're not on the boat?)
I've noticed recently that during bulk mode my bulk charging current drops off as the voltage comes up. I don't think this is a desired effect. I thought one wanted max current until you hit the accept voltage. (Max current is according to the recommended maximum charge current for the bank, with consideration for max alternator current.) I don't know why it drops off, maybe the alternator needs to spin faster for 100A at 14.0V than it does at 100A and 13.5V. Or maybe it's just a design shortfall in the Link 200-R. I'v also noticed that once I hit accept, I can slow the engine down quite a bit while maintaining the 14.8V accept voltage. So, what I think would work well is a generator mode system where neutral is sensed, for safety, and then the engine speed is controlled by the charging system, just as the field current is: controlled together, to achieve the most engine speed efficient charging possible.
I could have a pair of buttons by my electrical panel: generator on, generator off. I could also set it to run automatically, especially for when I'm sailing, and maybe even have a rotary selector to select how far I want to discharge batts before generating, and also set preferred times of day, and times not to run - like when we're sleeping. A manual lockout for when we're entertaining, or swimming, etc.
(How do you guys feel about the main engine running for generating while you're not on the boat?)
The reason it tapers off is that the Charge Acceptance Rate of your batteries drops as the charge level increases. All lead batteries have that issue, although the AGM and Firefly batteries have better (faster) CAR capabilities. There's lots of information on the web about that. Lithium batteries would accept all you can give them. Different animal.
Larry, perhaps I should have been more clear. It's not the current tapering during acceptance mode, which is expected, it's that my current tapers off during bulk mode, at constant engine RPM. I think bulk current should be constant, with voltage coming up towards the acceptance voltage.
Wouldn't want that happening on my boat. But I have a skeptical opinion of electronics on boat being sufficiently reliable to do something like that and never have a glitch.
dj
I think the acceptance rate normally does taper off during bulk charge, and also your alternator output normally declines as it heats up.