Triskel power generation system on Distant Shores III

[a64pilot]

Originally Posted by john61ct

Yes, that is completely false.

Load on the engine is nearly zero once there are no further demands for energy

Well not zero. I believe the number for drag racing was a belt cost 3 hp, and that was turning nothing at all. But that was also at drag racing RPM so on a sailboat it’s less.
However an alternator’s load of course varies with power generated, tremendously.

However to use a prime mover as a real significant source of electrical generation will require a variable speed drive or a variable pitch prop, or you will be underpropped most of the time, because we all know how bad being way overpropped is, and if you draw off 5kw or more of power off of an average engine, that along with the normal prop load will overload the engine, so your only real choice is to prop correctly when the alternators are loaded down, and just be underpropped when they aren’t.

So far as the Tach “problem” using an alternator as a signal for a tachometer, is well cheap and ignorant. If you need a tach, install the very much more accurate Hall effect tachometer, just a few bucks more, any engine manufacturer using the alternator should be embarrassed. Know of any cars or motorcycles that do? Me either.
It’s at best a sloppy, inaccurate kluge.

[john61ct]

Originally Posted by a64pilot

Well not zero

Near zero is what I said, certainly not worth "clutching" beyond depowering the field current.

3HP is well over a kW, so (if true) the drag racing stat is ridonculous for a puttering primary engine.

Prop issues are important of course, and require pro help for most,

and ideally the right engine is matched to the intended usage.

> to use a prime mover as a real significant source of electrical generation

is done all the time.

Yes, dynamically, auotomatically optimizing for the propulsion power currently required, while concurrently delivering as much electricity as possible, and **also** optimizing for engine health and fuel efficiency, is the big challenge that inTEGrel has taken on, very exciting!

Even more so, to me, would be a design allowing less well-funded boats to get much of the benefits, at a fraction of the Triskel investment.


> your only real choice is to prop correctly when the alternators are loaded down, and just be underpropped when they aren’t.

Wut? when maximum propulsion power, and/or better efficiency is required,

power diverted (= charge current demanded) can be regulated downwards or eliminated, by e.g. Wakespeed/American Power CAN-enabled VR

Thus allowing the prop setup to be optimized for peak efficiency when the alt is completely unloaded, or at very low power diversion to electricity.

Say only 1-2 hours every 4-5 days fully replenishes your LFP bank. This would allow you to only draw electric charging level during times when lower efficiency in propulsion is acceptable.

I also imagine, completely disabling power to the prop would not require an unusually high-tech solution?


> It’s at best a sloppy, inaccurate kluge

As is any attempt to get champagne out of a beer budget 8-)

[a64pilot]

Another thing that keeps being either ignored or forgotten is that I believe an alternator is much less efficient than an AC generator.
You see an alternator is an AC generator that converts AC power to pulsed DC power with diodes, and these diodes generate a lot of heat, and this heat is wasted power of course, and it’s not an insignificant amount of heat. Point being is that 5 KW of alternators will really load down an engine maybe more than you would think if they are making 5 KW. My SWAG is about 15 HP.

My 44 HP motor is making about 17 HP at my normal cruise rpm of 1800, and about 6.5 kts. To add an additional 15 HP to that takes me to 2700 RPM and I’d need to be propped so that 2700 RPM still only gives me 6.5 kts to keep from overloading the engine.

It amount to the simple fact that there is no free lunch.

Now for engines well over 100 HP, maybe throwing an additional 15 on it isn’t so bad, less percentage of load.

If 5kw is what your after, the Nexgen gives it to you for 230 lbs, 270 I think with a sound shield.

The aircraft argument doesn’t play in any of this, the aircraft argument is if an engine quits, the other one can get you home, however statistically more are killed from an engine failure in a twin than a single. The reason is the average civilian pilot in truth isn’t that well trained and when one quits, its often followed by loss of control. And that isn’t often survived. If the single engine quits, you still have control and a vote in where and how the crash will occur.

Now on a boat if one quits, you don’t likely lose control, so having a get home motor is logical if you really need that.

In my opinion and realize this is my opinion, but having a generator to do what it is designed for, which is to generate power, and also having a robust alternator mostly as a backup for that generator is likely a good option, that gives you greater redundancy than massive alternators on your prime mover engine, and no generator.
Assuming of course your boat for whatever reason is a power hungry boat and you don’t want Solar or Solar isn’t enough by itself.

The little Nexgen are relatively cheap and weight wise, it’s the same as adding a crew member, most boats can handle the weight.

Now what would be interesting to me would be an electric get home motor, one run off of AC power that would load a decently large generator and was maybe similar to a trolling motor in the way it mounted.
That could be a get home motor for say an Artic boat that wanted another means of propulsion other than sails and was way too far away from help to just call.

That would give you both a redundancy of power generation and a redundancy of propulsion, likely pretty meager though, maybe 4 kts?

[a64pilot]

A big motor on a big boat with a Hunstead controllable pitch prop and an exhaust pyrometer could make the propulsion engine into a sometimes big generator, and not overload anything and not be overpropped when generating and under propped when not.

[john61ct]

I guess if you already have a big bank capable of propulsion over a decent range, the ideal for redundancy would be a single ICE engine designed to be the default propulsion motor, which also is capable of refilling the LFP bank in say 2 hours.

And an ICE electric generator, capable of driving the electric backup propulsion setup, perhaps inefficiently but at least at a reasonable limp-home speed.

Solar panels, wind/hydro galore for reducing fossil fuel usage when the usage pattern allows.

Not cheap nor KISS by any means, but blue-sky spitballin'. . .

[a64pilot]

Everything except the electrical propulsion thing would be cheap, is standard stuff, no science experiments and already on many boats
All we are talking about is a bog standard generator and a school bus alternator on the propulsion engine. Not sure where two hours comes from, some with big boats have pretty huge power demands.

Assumption is that if you desire some huge power generating capacity, then your demands must be large, or all you need is a Honda and a decent alternator, or just Solar if your use is low and the weather cooperates.

From a money perspective I bet that an inexpensive generator run very frequently and replaced every few years comes out cheaper than exotic generation systems and huge lithium banks.

The get home electric propulsion system was just me thinking in print, it would only be viable if there is some kind of trolling motor type of thing in existence, something that lived in the Lazarette until needed.
It would be a way of having a back up propulsion system without another motor dedicated just for that.
I believe that it’s not uncommon at all for larger more expensive trawlers to have a get home motor and folding prop in the event the single propulsion motors breaks.

[john61ct]

The "reduce fuel usage" part also appeals for me, when not on any schedule.

[a64pilot]

Originally Posted by john61ct

The "reduce fuel usage" part also appeals for me, when not on any schedule.

Except I bet it doesn’t.
Put simply there is no such thing as a free lunch, if you extract 15 additional HP from an engine, you will burn 15 HP worth of fuel to do it.
Now of you run a second engine to get that 15 HP theoretically you will burn more fuel as there is more friction and your running another water pump etc.
but the difference is I bet very small, surprisingly small.

One truism in aircraft is that the slower you turn an engine, the more efficient it will be due to less internal engine friction and a more efficient prop. Prop increases pitch to keep thrust the same at lower RPM.
It’s an absolute truth that can be proved on paper.

Well I tried it out of curiosity, on my airplane I had extremely accurate instrumentation to include a fuel flow meter calibrated down to .1GPH
You slow the RPM, but increase manifolds pressure to keep power output the same, within capabilities of course, guess what. It made no difference that I could measure.

Diesel engine fuel burn for HP extracted for engines the size of ours is pretty flat, meaning that to extract 40 HP from a 100 HP motor or a 60 HP motor the fuel burn is almost identical.
As much as I wish that common rails would be much more efficient, unfortunately they aren’t much.
Turbo’s are slightly more efficient as they make use of what is otherwise wasted heat, but it’s not by much.

Now taking power from a propulsion engine to make electricity will in fact I believe burn more fuel. The reason is as I said earlier you have to prop for that load, and when that load isn’t there, your tuning the motor at excess RPM to achieve the Cruise speed and therefore burning more fuel.

Back to there just ain’t no such thing as a free lunch, unfortunately.

You want to save fuel? Slow down, and of course ideally sail.

[john61ct]

I meant enjoying hanging around for the "alternative" non-ICE sources to give me another few hours' motoring energy.

But these topics have been well covered elsewhere, let's continue in a different thread if you want, we've derailed this one enough IMO

[Dockhead]

Originally Posted by a64pilot

Except I bet it doesn’t.
Put simply there is no such thing as a free lunch, if you extract 15 additional HP from an engine, you will burn 15 HP worth of fuel to do it.
Now of you run a second engine to get that 15 HP theoretically you will burn more fuel as there is more friction and your running another water pump etc.
but the difference is I bet very small, surprisingly small.

One truism in aircraft is that the slower you turn an engine, the more efficient it will be due to less internal engine friction and a more efficient prop. Prop increases pitch to keep thrust the same at lower RPM.
It’s an absolute truth that can be proved on paper.

Well I tried it out of curiosity, on my airplane I had extremely accurate instrumentation to include a fuel flow meter calibrated down to .1GPH
You slow the RPM, but increase manifolds pressure to keep power output the same, within capabilities of course, guess what. It made no difference that I could measure.

Diesel engine fuel burn for HP extracted for engines the size of ours is pretty flat, meaning that to extract 40 HP from a 100 HP motor or a 60 HP motor the fuel burn is almost identical.
As much as I wish that common rails would be much more efficient, unfortunately they aren’t much.
Turbo’s are slightly more efficient as they make use of what is otherwise wasted heat, but it’s not by much.

Now taking power from a propulsion engine to make electricity will in fact I believe burn more fuel. The reason is as I said earlier you have to prop for that load, and when that load isn’t there, your tuning the motor at excess RPM to achieve the Cruise speed and therefore burning more fuel.

Back to there just ain’t no such thing as a free lunch, unfortunately.

You want to save fuel? Slow down, and of course ideally sail.

The numbers don't lie -- just get a fuel map for your engine and see for yourself.


Saving tiny and most likely unmeasurable amounts of fuel with slightly different engine regimes is not going to change the weather in anyone's cruising budget.


The big dollars are in engine hours -- maintenance, amortization. It is true that generating power from the main engine WHILE you are also doing propulsion with it costs less fuel -- that's because you pay the MARGINAL and not AVERAGE fuel consumption for the incremental extra power you need for the alternator.


But you are saving the same number of engine hours by combining the tasks of generation and propulsion. THAT'S where the big savings are.


Also remember that recreational diesels are often timed out before they get worn out. So even using the main engine for generation without propulsion may save you money because you are getting hours out of the engine which you might not get out of it before it times out anyway. The little bit of extra fuel you might burn (see fuel map for exact numbers) because you are loading the engine so much less is peanuts in comparison.


Now one caveat is you do need to keep at least enough load on it to keep the cylinders warm. Otherwise you can damage the engine early in its life. But that's not necessarily so much harder to avoid than it is with a constant speed generator, because using the main you can modulate the RPM.

[a64pilot]

I think no recreational Diesel times out as there is no TBO requirement, Maybe you mean they die of old age? To that I’d say they die of poor maintenance, my motor is 32 yrs old and if it’s properly cared for what will kill it is non availability of parts, if parts are available it should last another 32 years, but then I fly a 1946 airplane that will I’m certain if I don’t crash, it outlive me.
An engine if properly maintained doesn’t really age much, rubber components do of course, but in a fresh water cooled engine there is very little corrosion, that occurs in the heat exchanger of course.
They wear out from running hours.


But anyway I digress, yes running time is what cost you money in a boat that you intend to keep for a long time.
And based on that I’d rather put hours on my $5,000 generator than I had my $25,000 propulsion engine. Actually in my case I am very often running my $1,000 Honda specifically to save hours on the Diesel, but to run your Propulsion engine to make power is I think money foolish.

It’s a good idea for it to be able to supply a enough power to run the boat and charge the bank, but as a prime generator I don’t think that is logical.
If you can get 2.5 KW from a School bus alternator, surely that’s enough to run the boat and charge the bank, maybe not rapid charge a bank, but enough to significantly charge one.
But if your at anchor and want to run Airconditioners or something, run the generator, you’ll be ahead if you do.

But again I’ll state that to put a significant load on a motor if your motoring, you will overload the engine, unless you can decrease the prop pitch, and that’s big money and not even possible on smaller boats.

[Dockhead]

Originally Posted by a64pilot

I think no recreational Diesel times out as there is no TBO requirement, Maybe you mean they die of old age? To that I’d say they die of poor maintenance, my motor is 32 yrs old and if it’s properly cared for what will kill it is non availability of parts, if parts are available it should last another 32 years, but then I fly a 1946 airplane that will I’m certain if I don’t crash, it outlive me.
An engine if properly maintained doesn’t really age much, rubber components do of course, but in a fresh water cooled engine there is very little corrosion, that occurs in the heat exchanger of course.
They wear out from running hours.

If you query yards who do much repowering, they will tell you that most recreational boats are repowered because the engines are aged out, not worn out -- rusty, unavailable parts, troublesome. I think relatively few get overhauled; mostly they get pulled out and replaced. At least in this part of the world.



Even I only put less than 300 hours a year on my main engine; it would take a long time for it to be gone from too many hours.

Originally Posted by a64pilot

But anyway I digress, yes running time is what cost you money in a boat that you intend to keep for a long time.
And based on that I’d rather put hours on my $5,000 generator than I had my $25,000 propulsion engine. Actually in my case I am very often running my $1,000 Honda specifically to save hours on the Diesel, but to run your Propulsion engine to make power is I think money foolish.

It’s a good idea for it to be able to supply a enough power to run the boat and charge the bank, but as a prime generator I don’t think that is logical.
If you can get 2.5 KW from a School bus alternator, surely that’s enough to run the boat and charge the bank, maybe not rapid charge a bank, but enough to significantly charge one.
But if your at anchor and want to run Airconditioners or something, run the generator, you’ll be ahead if you do.

But again I’ll state that to put a significant load on a motor if your motoring, you will overload the engine, unless you can decrease the prop pitch, and that’s big money and not even possible on smaller boats.

YMMV indeed if you have a cheap generator. In your case, that's a good plan. In my case, main engine and heavy duty generator are about the same cost.


If I were going to build a boat without a separate generator, I would certainly not rely on one 2.5kW school bus alternator for all my power needs. I would use one of those big Humvee alternators with a clutch. With a big lithium battery bank and giant alternator, you radically reduce the number of hours you need to run the generator, to make your power. If the bank is big enough, you could even run A/C off of it so you're not running the generator every hour you need A/C, which seems terribly wasteful to me.


I don't really know anything about it, as air conditioning is a vague memory up here; we heat year round and no one has or needs A/C. When I cruised U.S. and Caribbean waters, we did have A/C but we used it only on the dock off shore power. Running A/C from a genset is a challenge I haven't given much thought to. Doesn't actually sound all that pleasant, running genset and A/C at anchor somewhere.

[OceanPlanet]

While we were at the Annapolis Sail show, we got to spend some time with one of the early Integrel system users (engineer friend of Nigel's, system installed on his own Hunter), and learned some interesting stuff.

In hot summer coastal cruising, he would run the aircon (via batteries/inverter) while motoring to the next evening's destination. If they had at least a few hours of motoring (not uncommon), the interior of the boat would be fully cooled by the time they were moored. With the boat already cooled, they could run the aircon all night long and only use up 15-20% of the house battery capacity by morning. I forget the size of his house however it was nothing extravagant.

Being an engineer and working closely with Nigel, he had fairly accurate fuel use monitoring. Apparently adding the load of the inverter/aircon while motoring DID increase fuel use, but only by a tiny amount; about .1 or .2gal/hr, IIRC.

He had also done some load testing and figured out that if the boat was hot to start with, it would take nearly 5kWh of energy (400+Ah from a 12V battery bank) to get the interior cooled down. So, by cooling while motoring, a large amount of battery use was averted. If found this very interesting, and now it seems obvious, however hadn't thought of this use pattern before.

FWIW, the Integrel uses either CANbus data from the engine, or a programmed rpm/load curve, to regulate the charging load so as to not overload the engine.

[mcarthur]

I'm getting the feeling that, with a powercat having 2 x 135hp diesels (mid-size), if (big if!) we wanted to remove the genset we'd be better off using 2 larger alts (one per engine, say 125A+) combined with solar, maybe lithiums, rather than Integrel.

It seems more directed to smaller motors (is than <40hp or so?) run irregularly (sailing predominates)… Oh, and given the only pricing I've seen is A$18,000 or about US$12,000 not installed, I'd amend the beneficial conditions with something like "and is a new build or your genset is dead/dying"!

[OceanPlanet]

"and is a new build or your genset is dead/dying"! - yes, upgrading to such a system definitely makes more financial sense in these cases.

Note that we wouldn't consider125A x 14V a large alternator. That's only 1.75kW (at most, usually much less). Whereas the following examples are the more common alt upgrades we do (in order of output):

1) an MGDC small case 220A x 14V with remote rectifier, for @200A x 14V continuous is around 2.8kW.

2) an MGDC J180 mount shortened lg case 250A x 14V, with remote rectifier, for 240 x 14V continuous, around 3.3kW.

3) an APS HPI 360A x 14V super compact can fit into the stock alternator position, and output 300A continuous, or around 4kW, without an external rectifier. Note that going this power @14V requires very large cabling & fuses.

4) an APS HPI 185A x 28V (same size as the 14V, for 160A x 28V continuous; around 4.4kW

5) an APS 55i large case 300A x 28V (as added unit, won't fit in stock position) for 250A x 28V, around 7kW

The Integrel system can output 8kW or more, around 150A x 56V, and has a very advanced regulation system to automatically maximize output without overloading the engine.

Obviously some of the above are completely overkill for boats that aren't running aircon or other high continuous loads. But for those that do have the loads, going with a high output alternator is a worthwhile option to consider, vs a generator.