Lagoon 420 hybrid + modern tech

[44'cruisingcat]

Yeah, it's pretty simple. Although I've seen it claimed by Torqueedo and others that electric motors have a flat torque curve, they actually don't. Electric motors have a flat power "curve".


And since power is torque x RPM, that means you have maximum torque at zero RPM, reducing in a straight line to zero available torque at maximum free spinning RPM.


In fact, it's ICE's which have closer to a flat torque curve, usually in modern engines only really lacking at idle speeds.

[myocean]

Originally Posted by 44'cruisingcat

Although I've seen it claimed by Torqueedo and others that electric motors have a flat torque curve, they actually don't. Electric motors have a flat power "curve".

Its both correct - and it depends...
For electric motors the maximum current possible is the first limiting factor. This results in maximum torque from the beginning at low speeds and it results in a flat torque curve.
Once the internal voltage has gone up due to increase in speed (voltage is correlated to the rotational speed) the current will at a certain point start going down because the total power available is limited. From that point on you have constant power, not constant torque, and the torque curve is going town.

Another way to explain this is that the power, which is calculated from (torque x rpm), will increase until the maximum available power is reached. Until this point, torque is constant.

[sparau]

It is a pity that lithium mining is a dirty operation since they are a pretty good battery.

We need graphene capacitor tech to be available, hopefully when they start to commercialise it they can keep the biodegradable part intact.

[Stumble]

So I was able to track down a side by side comparison of the Torquedo 3hp motor with the Lehr 2.5hp, and an off brand 2.5hp gas motor. Now these are 25% less powerful than the Torqueedo claims it replaces, but even still the electric couldn't compete.

http://www.lehruk.com/wp-content/upl...-Test-Lehr.pdf

Now this is dactyl the test the Torquedo should excel at, small boat driven below hull speed, where it's very large prop should help a lot. But in all test cases it was slower than fossils fuel motors.

My issue isn't that it isn't a good engine (it is), or that it has a usable profile (it does), but that it's marketing is all voodoo. HP, by law, is measured at the prop shaft for all outboards and has been for a long time. This 'equivilant' crap is just that, marketing crap, no different than any other snake oil salesman. If they would just sell their products based on what they actually are, instead of what they wish they were building it would go a long way to giving them some credibility.

[myocean]

Originally Posted by Stumble

But in all test cases it was slower than fossils fuel motors.

...and the Torqeedo motor is, together with the Hidea, a top performer for the pull test!

[rabbi]

Originally Posted by Stumble

My issue isn't that it isn't a good engine (it is), or that it has a usable profile (it does), but that it's marketing is all voodoo. HP, by law, is measured at the prop shaft for all outboards and has been for a long time. This 'equivilant' crap is just that, marketing crap, no different than any other snake oil salesman. If they would just sell their products based on what they actually are, instead of what they wish they were building it would go a long way to giving them some credibility.

+1

Originally Posted by myocean

...and the Torqeedo motor is, together with the Hidea, a top performer for the pull test!

I rarely pull somehing with my dinghy. BTW: the Hidea is just 1/3 of the price.

Looks like the Torqueedo has less power for drivin aboat than a 2.5hp engine.

[myocean]

Originally Posted by rabbi

+1
I rarely pull somehing with my dinghy. BTW: the Hidea is just 1/3 of the price.

Would be interesting to go against wind and waves with those motors.
(Power = Force x Speed)

As they say in the article - its wonderful to use the Torqeedo motor but it comes for a premium price. Hopefully there will be cheaper batteries in future!

[Stumble]

Originally Posted by myocean

...and the Torqeedo motor is, together with the Hidea, a top performer for the pull test!

Pull tests tell you very little about how the engine will operate once it is underway. It's important for tugs to get heavy ships moving but little else. And this test is grotesquely weighted towards bigger props.

What I would have been interested to see is what happens when you compare the Torqueedo side by side with a high thrust outboard, like what should be used on a non-planning dinghy.

[rabbi]

Originally Posted by myocean

Would be interesting to go against wind and waves with those motors.
(Power = Force x Speed)

As they say in the article - its wonderful to use the Torqeedo motor but it comes for a premium price. Hopefully there will be cheaper batteries in future!

I doubt that wind & waves will make the slowest motor become the feastest.

Pull test is only relevant if there is so much wind that the boat is almost stationary.

[StuM]

Originally Posted by myocean

...and the Torqeedo motor is, together with the Hidea, a top performer for the pull test!

ROTFLMAO. Are you in marketing by any chance?

It came second out of four but was as close to #3 as it was to #1
Out of the motors rated 2.5HP or more, together with the Lehr, it was a bottom performer.

In terms of pulling power per rated HP, it ranked dead last.

On the more relevant use case of cruising speed, it also rated dead last in comparison to the two lower HP rated non-electric motors. (It only managed to beat another electric motor which had less than half its rated Hp).

[StuM]

Originally Posted by myocean

Would be interesting to go against wind and waves with those motors.
(Power = Force x Speed)

So in the static pull test where speed = 0, then Power = 0?

[Santanas]

Friends, there is no more data at hand and this is a bit OFF TOPIC. Do the outboard manufacturers do laboratory tests regarding such numbers?


I am still missing the final reason why the Lagoon hybrid has been discontinued. Is it that all these electric systems have been by far too unreliable?
Because looking around in the net I find that people who have a working system, or new owners of e.g. an Ocean Volt drive, all seem to be quite happy with handling, noise and so on.

[Stumble]

Santanas,

Basically the systems generally simply didn't work as intended and there were a lot more growing pains than they ever expected. The batteries didn't provide the range they expected, running the generator was pretty much mandatory to go anywhere, basically it was a big mess. Lagoon wound up offering any of the electric owners a free swap to diesels and I think all but one or two of them took it.

The probe is the same one a number of people have espoused in thread after thread on electric propulsion. There simply isn't enough energy density in any known electrical storage device to provide meaningful range. Liquid fuel is simply immensely energy dense and competing with it has so far proven impossible.

Combined with the paltry amount of power available from solar panels this makes dealing with an all electric vessel difficult. You simply cannot place enough panels on a boat to generate a meaningful amount of power and you never will be able to. The absolute theoretical maximum solar energy is 1,000w/sq meter, and there is a conversion limit of ~33% that cannot be exceeded. So the absolute maximum electrical power we will ever get out of a sq meter of panels is 333w.

If you assume a 40' cat needs just 20kw to get to cruising speed that's an energy burn of 480kwh used in one day. To generate that much power over an 8 hour solar production day (6 is more typically used) you need 180 sq meters of perfect solar panel that always generate power at 100% of maximum efficiency and never get shaded.

That isn't to say that a diesel/electric hybrid doesn't have some interesting applications. If all you need a motor for is to get in and out of the harbor then they can work great (mine did). But of you want to be able to motor a meaningful distance it requires a massive (by marine standards) generator, because the amount of power required is pretty high. Or if battery technology ever starts to show substantial gains (5x10 times as powerful as the best current batteries) then it starts to look better.

Personally I think the most interesting hybrid technology on the market is in the diesel generators. Specifically micro diesel turbines. They are smaller, lighter, and quester than a Diesel IC engine. If these actually start to make it to market it may be possible to instal two physically small turbines, one for house loads and one for propulsion loads, at substantial efficency space and weight gains. Not to mention they are theoretically much easier to maintain. But I don't know of any that are being applied to pleasure marine use yet.

[StuM]

Originally Posted by Stumble

... There simply isn't enough energy density in any known electrical storage device to provide meaningful range. Liquid fuel is simply immensely energy dense and competing with it has so far proven impossible.
...

An excellence summary of the current "state of play",

Thank you !

[fabgo]

Originally Posted by Octopus

I've been the proud owner of a Lagoon 420 Hybrid for the last nine years and have been very happy with the propulsion system and delighted with the whole boat.

Like all boats its design is a compromise and some elements of the design were very radical. The design delivered class-leading accommodation and liveability, for its size, but sacrificed sailing and motoring performance. The boat is heavy, not just because of the twelve lead acid propulsion batteries, weighing in at 840 kg (850 lbs), but also because of the wide capacious hulls and the large superstructure.

Even so, the motoring performance at 6.5 knots cruising speed and 7.5 knots maximum in calm seas, is adequate for most occasions, partly because the class-leading accommodation makes it a joy to be aboard.


I've always been happy with the fuel consumption, so I'm not sure why you think it is poor. It's possible that some people found it poor because they went at full power all the time, because they were not content with its cruising speed. The genset uses 6.1 l/h at maximum output (17.5 kW) and about 4 l/h at cruising speed. I've always thought that anything less than a liter per nautical mile is OK for such a big boat.

The two electric motors are nominally rated at 10kW and the Kubota diesel engine that drives the 17.5 kW generator is 29HP, but together these push the boat through the water at a speed that is only about one knot slower than the 80HP non-hybrid Lagoon 420 hybrids, powered by twin 40HP engines, so it is pretty clear that the hybrid arrangement is more efficient.

It is right that the lead acid batteries are the Achilles heel of the system. This is not just because of the enormous weight, but also because of the complicated control system required to protect the batteries. I'm just waiting for my lead acid batteries to fail, so that I can replace them with LiFePO4 batteries, which will make an enormous difference. It will not only halve the weight of the battery bank, but it will double the usable capacity and I'll be able to ditch Lagoon's complicated electronic control system. It will also be more efficient, because I will be able to charge them at full power, so I'll no longer have to run a 17.kW generator at its most inefficient low-loading, just to trickle charge the batteries for the last hour of charging, to get them fully charged.

I'm not convinced about the viability of solar power to propel the boat. It's fine for re-charging the batteries and keeping up with normal loads, but not for the heavy propulsion loads, unless you are motoring on very short trips.

Some people have installed folding props to reduce the drag when sailing, but this has three drawbacks that I've been unwilling to accept. First, you would lose the ability to generate serious amounts of power under sail, which is very satisfying to recharge the batteries for free. Second, I use the prop drag under ReGen to slow the boat down, when we are going a little too fast for comfort. Third, you lose some manoeuvrability under power as you can't go straight from forward into reverse and get instant thrust. One of the real joys of the hybrid is it's outstanding manoeuvrability under power, owing to the instant torque. Note: the other great joys of the hybrid are: the silence of the whole propulsion system, the low maintenance, the side-effect of abundant AC and DC electrical power for other purposes (cooking, cooling, heating, washing, water-making etc. etc.).

Chris

Thank you Chris for your review. I wonder why hybrid electric systems are not more popular. It seems an ideal system for a sailboat.

Like you said, electric motors are much more reliable and require much less maintenance. The generator can operate very efficiently and also provides power for the rest of the boat.

Solar panels can provide enough power to run the motors for short periods such as docking.

The only downside I can see is that the techology is not as proven as diesel engines.

So why is it not more broadly in use? What am I missing.

- Fabian