Triskel power generation system on Distant Shores III

[Dockhead]

Originally Posted by tanglewood

I think it's quite common for people to think that power generated from the main engine is "free" compared to running a generator. But in terms of fuel consumption, it certainly isn't. Your main will burn more fuel when generating 7kw vs when not, just as your generator will. Which will be more is a complex formula based on relative loading of the two motors and their respective bsfc, plus the efficiency of the electrics to generate and get the power into a usable form.


About a year ago I conducted an experiment on our boat to compare fuel burn vs power generated, looking at the main engine/alternator and the generator as power sources. For light loads (light is a relative term), the main/alternator was better. At that load, power losses in the alternator were low making it better, and efficiency in the generator engine were poor handicapping it. But for heavy loads, the generator was better. It's engine was operating at an efficient load, vs the large power losses in the alternator at high loads.



Adventures of Tanglewood: Engine Alternator or Generator: Which is More Efficient?



Now fuel consumption is only once consideration. If using your main engine lets you get rid of a generator all together, I can see that being compelling. I know other people who just want to reduce the maintenance interval on their generator, so prefer to use the main+alt.


As always, there is no "right" answer. But there can be lots of misunderstanding that will lead to bad conclusions.

Yes, but you are considering only the marginal fuel consumption. If you generate power while doing propulsion, using the same diesel engine, you are saving all of the other three elements of the total cost of the power: (a) fuel overhead; (b) maintenance cost per hour; (c) amortization of the diesel engine, per hour.



You might also be loading the engine better, which may have a health benefit for the engine. Running the main engine slowly does not load the engine well because of the nature of propeller curves.


To get a complete picture you would have to compare the total marginal cost of generating a kW/h of power while motoring, to running the generator by itself. The difference will be huge.



Amortization alone of my genset is about £3/hour on a straight line basis, assuming about 7000 hours useful life. That does not include maintenance and repairs. This is significantly more than the cost of fuel.



So if you can do a significant amount of your power generation while running the main engine for propulsion anyway, you'll save a ton of money.


What this analysis doesn't consider also is the time value of money, or aging out of diesel engines. If you use one diesel engine more intensely, rather than two diesel engines less intensely, you will save money on the cost of the capital over time, which is not reflected in straight line amortization. Also most diesel engines used in recreational boats are aged out before they are timed out, so by using them more intensely, you can get more hours out of them before they need to be replaced and reducing the amortization cost per hour. These factors add even more weight to the approach of using one rather than two diesel engines for propulsion and power generation.

[Dockhead]

My boat is 18 years old, and in my ownership for 10. I have 3400 hours on the main engine and 2100 or something on the genset.



That despite very intense use, basically in constant motion and mostly off grid for at least 4 months out of every year.


At this rate, both of these very expensive devices will be aged out before they are timed out -- I will have to replace them (or overhaul them) before they have given their full potential hours. I would much rather have saved £20 000 at the beginning, in order to have 5 500 hours on one device over 18 years, rather than 3400 on one and 2100 on another. I would be on track to replace it at 20 years or 23 years or whatever, with more or less full number of hours extracted. The saved £20 000 in the bank or the stock market would buy two new repowers by now.

[tanglewood]

Originally Posted by Dockhead

Yes, but you are considering only the marginal fuel consumption. If you generate power while doing propulsion, using the same diesel engine, you are saving all of the other three elements of the total cost of the power: (a) fuel overhead; (b) maintenance cost per hour; (c) amortization of the diesel engine, per hour.



You might also be loading the engine better, which may have a health benefit for the engine. Running the main engine slowly does not load the engine well because of the nature of propeller curves.


To get a complete picture you would have to compare the total marginal cost of generating a kW/h of power while motoring, to running the generator by itself. The difference will be huge.



Amortization alone of my genset is about £3/hour on a straight line basis, assuming about 7000 hours useful life. That does not include maintenance and repairs. This is significantly more than the cost of fuel.



So if you can do a significant amount of your power generation while running the main engine for propulsion anyway, you'll save a ton of money.


What this analysis doesn't consider also is the time value of money, or aging out of diesel engines. If you use one diesel engine more intensely, rather than two diesel engines less intensely, you will save money on the cost of the capital over time, which is not reflected in straight line amortization. Also most diesel engines used in recreational boats are aged out before they are timed out, so by using them more intensely, you can get more hours out of them before they need to be replaced and reducing the amortization cost per hour. These factors add even more weight to the approach of using one rather than two diesel engines for propulsion and power generation.

That's all correct, I think. I was ONLY measuring fuel consumption. The specific scenario that prompted the experiment was fuel/range calculations for a pacific crossing in a power boat. One friend did it without HVAC because he didn't want to burn the fuel to run the generator. Some people have outfitted their boats with enough main engine alternator power to run HVAC, so the question was then which burns less fuel, the main or a generator.


To your point, I know one guy who favors main engine power generation simply to save on oil changes for the generator.

[tanglewood]

Since this topic has re-emerged, has anyone installed a Triskel system? Any reports back?

[Cdn]

I am interested in this system to reduce the number of engines I need maintain/monitor. Its much like the one vs two engine debate on smaller aircraft (IE the PC12 vs King Air). The number one issue is the price. No way anyone would pay the same amount of money for a engine mounted generator vs a standalone generator for the same price! This package need to be at max, a $10,000 (USD) upgrade. I think as the initial research investment is paid off and Lithium batteries drop in price over the next 5-10 years, this setup will become more financially reasonable.

[john61ct]

Originally Posted by Cdn

Lithium batteries drop in price over the next 5-10 years

I doubt the price of quality LFP cells will.

BMS and other ancillary circuitry will improve in value, better quality, more flexibility at the low end of the market.

That will cut into the margins of the packaged system vendors, maybe.

But not the cells themselves

[Dockhead]

Originally Posted by Cdn

I am interested in this system to reduce the number of engines I need maintain/monitor. Its much like the one vs two engine debate on smaller aircraft (IE the PC12 vs King Air). The number one issue is the price. No way anyone would pay the same amount of money for a engine mounted generator vs a standalone generator for the same price! This package need to be at max, a $10,000 (USD) upgrade. I think as the initial research investment is paid off and Lithium batteries drop in price over the next 5-10 years, this setup will become more financially reasonable.

I agree with you entirely about PC12 vs King Air. One engine, perfectly maintained.


But you don't need anything so elaborate as the Triskell system. On the contrary, I would favor something more -- agricultural, to simplify, cheapen, and make repair and maintenance more straightforward. It is not hard to find a more or less standard alternator which produces as much as 4 or 5 kW (I've got one now which reliably produces 2.5kW, and it costs £500 to replace in its entirety and can be repaired by any third world auto-electric shop). Sort out good regulation -- also not an untrod path -- have an excellent charger/inverter or bank of them, and Bob's your uncle. This will right by itself be much cheaper than main plus genset, and you can probably add the LiFePo4 bank within your cost savings, too.

[Dockhead]

Originally Posted by john61ct

I doubt the price of quality LFP cells will.

BMS and other ancillary circuitry will improve in value, better quality, more flexibility at the low end of the market.

That will cut into the margins of the packaged system vendors, maybe.

But not the cells themselves

Sure, but we hardly care, do we? The cells are already much cheaper than lead in terms of cost per kWh stored and released.


Other than the fact that people still lack experience with it and the different electrical system architecture needed to implement it, I think LiFePo4 is kind of a no-brainer already for bulk power storage for us as other lithium technologies are for other bulk power storage applications. Do you see any electric cars any more with lead batteries?

[john61ct]

Sure lots of the DIY conversions are.

Also powering electric boat propulsion.

Not advocating that but at least in the U.S. quality lead is still so crazy cheap, that is I think a big factor holding back our developing reliable distribution channels for LFP.

But all that's bit of a diversion from the thread topic

[Q Xopa]

Originally Posted by john61ct

I doubt the price of quality LFP cells will.

BMS and other ancillary circuitry will improve in value, better quality, more flexibility at the low end of the market.

That will cut into the margins of the packaged system vendors, maybe.

But not the cells themselves

Hmmm interesting prediction.

As Yogi Bear says "predictions can be trickey, especially about the future".

My WAG is that like most other consumer items when they hit 'critical mass' they will get cheaper, probably a lot cheaper.

0f course Im sure I have atleast as much chance of calling it wrong as any expert.

They are not what I would call 'prime time' yet. But LFP cells take up is getting up a head of steam. Even if their market is grown by drop in demand.

Im not sure what you are basing your opinion on, scarcity of Lithium?

[Cdn]

As soon as the technology has been obtained by certain countries, they will then produce lithium cell batteries for a fraction of the price which will require the brand name companies to lower the price. This happens with all technology. a 300amph lithium ion battery is about 3500 today. In 5 years, it will be 2000. in 10 years, 1500 MAX!

Cheers

Nick

[Q Xopa]

Originally Posted by Cdn

I am interested in this system to reduce the number of engines I need maintain/monitor. Its much like the one vs two engine debate on smaller aircraft (IE the PC12 vs King Air). The number one issue is the price. No way anyone would pay the same amount of money for a engine mounted generator vs a standalone generator for the same price! This package need to be at max, a $10,000 (USD) upgrade. I think as the initial research investment is paid off and Lithium batteries drop in price over the next 5-10 years, this setup will become more financially reasonable.

Agreed, Im just putting a couple of new $350 24V 110A, large case truck alternators on my 4JH4-TE.

So thats around 5kW, with external regs and rectifiers.

I'll do an add up at the end but its way under $2k.

In between working away Im just putzing around with pullies, belts, mounts etc but nearly there.

I've got some pics, and I will do a bit of a write up if anyone is interested. Being a bit OCD, I document most of the details anyway.

[Cdn]

The advantage I see with the Triskel system is that once that batteries are done charging, it will reduce demand on the engine. I could be wrong, but I believe regular alternators put the same demand on the engine regardless if it needs to energy or not.

[john61ct]

Yes, that is completely false.

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

[OceanPlanet]

Originally Posted by Cdn

The advantage I see with the Triskel system is that once that batteries are done charging, it will reduce demand on the engine. I could be wrong, but I believe regular alternators put the same demand on the engine regardless if it needs to energy or not.

Alternators (and the Integrel is basically a very powerful and efficient alternator) produce energy (movement of electrons) by the spinning of the magnetized rotor inside the stator (the copper windings around the perimeter of the alternator). The magnetism of the rotor is controlled by the field current/voltage through provided by the alternator regulator.

The regulator can reduce the field to the rotor as needed when the battery voltage reaches the programmed level. Depending on the load on the batteries when they reach full voltage, the amount of current required from the alternator to hold the voltage will need to adjust.

If there is zero load on the batteries, the regulator may need to cut the field entirely. At this point the remaining physical load/drag on the engine is mainly just the cooling fan load in the alternator (pushing air through it) belt drag, bearings, etc. This is the same whether it's a smaller alternator or an Integrel.

Note that many engine panel tachometers get their rpm from the AC wave form feed from the stator of the alt. When the regulator cuts the field entirely (batteries completely full), there is often no stator signal and the engine tach reads zero. This is more common with lithium batteries that fill up more abruptly than Pb. Fortunately the cure for this "zero rpm" syndrome is simple: turn on some loads, the regulator sees the battery voltage drop, it sends field current through the rotor, the alternator produces current to the battery again, the stator signal revives, and voila...the tach reads rpm again...:-)