Electrical motor maths: 25HP=8HP?

[Guest625101138]

Originally Posted by jehardiman

That statement is absolutely wrong. Biofuels are far more viable today than solar for a marine prime mover. Plants are far more efficient converting solar energy than even 3rd generation cells as well as being carbon neutral. And existing ICE technology fully supports it. Liquid fuels are here to stay Rick, get with the program instead of being one of those toxic polluting electric dinosaurs... .

So you are one of these people wanting to take essential food production from the starving billions. These crops need huge water resources which is now having to be produced using desalination in many parts of the world. My understanding is desalination is not too far off on the west coast of USA either. Hard to have biofuels when there is no water for crops.

Solar energy production is the long term future. I am just staying ahead of the game. Besides I like the music of modern electric over the thud of crappier technology.

Rick W

[jehardiman]

Originally Posted by Rick Willoughby

So you are one of these people wanting to take essential food production from the starving billions. These crops need huge water resources which is now having to be produced using desalination in many parts of the world. My understanding is desalination is not too far off on the west coast of USA either. Hard to have biofuels when there is no water for crops.

Sighhhhh,


One word....algae!

[Guest625101138]

Originally Posted by jehardiman

...

One word....algae!

Now you're just plumbing the murky depths to sustain an implausible position.

Rick W

[jehardiman]

Originally Posted by Rick Willoughby

Now you're just plumbing the murky depths to sustain an implausible position.

Rick W

LOL, no, now you are then one who won't accept the correct answer because it doesn't fit your narrow view/expectations.

But, you don't have to believe me....

Here is a nice explaination from an academic sourcehttp://www.unh.edu/p2/biodiesel/article_alge.html

Or here from a more hyping commerical one...http://www.oilgae.com/

Don't trust me, do the numbers yourself. I could use a liquid fuel with half the BHU's in an ICE 2/3 as efficient and still be cost, weight, volume, energy and carbon balance ahead over a battery-solar cell system of the same power. Vessel efficiency is all about weight and volume and locking youself into preconcieved ideas about what is better takes alot of tools out of the toolbox.

[Guest625101138]

The electric is all eminently feasible now. Your algae gobbler is many years away I expect.

I can harvest wind and sun anywhere on the ocean right now.

Rick W

[Guest625101138]

Originally Posted by jehardiman

Here is a nice explaination from an academic sourcehttp://www.unh.edu/p2/biodiesel/article_alge.html

Or here from a more hyping commerical one...http://www.oilgae.com/

These fuels do not suit pleasure boating as well as solar-wind power but they certainly offer promise for heavy duty transport.

These are the sort of projects that USA should have got into seriously about 9 years ago rather than continuing to make terrorists wealthy.

Think how much self-reliance you would have on fuel production if you had started farming algae instead of going to war with the terrorists about a decade back.

Rick W

[FAST FRED]

"Think how much self-reliance you would have on fuel production if you had started farming algae instead of going to war with the terrorists about a decade back."

Over 85% of USA avaliable energy just waiting to be drilled or dug is "Off Limits" because of an insane congress.

Now they are busy putting solar in the middle of deserts , and wind farms as well OFF LIMITS .

'Fraid we will be funding terrorists far into the future.

FF

To be energy independant all the US needs is "permission" and a shovel.

FF

[jehardiman]

Originally Posted by Rick Willoughby

The electric is all eminently feasible now. Your algae gobbler is many years away I expect.

I can harvest wind and sun anywhere on the ocean right now.

Originally Posted by Rick Willoughby

These fuels do not suit pleasure boating as well as solar-wind power but they certainly offer promise for heavy duty transport.

Algae fuel is available today, and is a vaiable candidate for a main propulsion energy source where solar is not (for me wind power = sails not a generator). I think the difference is that I do not see electric propulsion as a viable prime mover execpt in vessels where the hotel loads dictate the over-installation of power (such a cruise ships or drill ships).

For pleasure craft IMHO, they divide into two main types: a) fast mechanical powerboats which need power dense prime movers i.e. liquid fuels and b) "slow" sailboats which use wind power and only have small auxillary propulsion and hotel loads. In case b), you could make arguments for both power dense systems to save space and weight or weight innefficient systems such a electrics and have synergy with ballast requirements.

Like many things in vessel desgn there is no one "best" answer, there are only better choices based upon what you need to accomplish.

[Guest625101138]

Originally Posted by Joakim

Thanks Rick. Is this the same motor you said would have 27 Nm at 400 W? If so and it would really produce that 28 Nm at 600 W, the efficiency of the power system would be about 70%, which is more than I thought.

So it can produce almost the same torque (28 Nm) at 600 W electrical power compared to Yanmar 2YM15 (not 2YM20 as you wrote earlier), which can produce 32 Nm at 1800 rpm thus producing 6 kW of power and consuming probably about 20 kW worth of fuel.

I don't quite know how to compare these two motors. They have about the same maximum power (10 kW vs. 9 kW) and about the same maximum torque (or is this 28 Nm about the maximum?). For propeller applications you don't need a lot of torque at low rpm, thus this benefit of a electric motor (or more of its controller) is not much of use. Probably it revs up much quicker while manoeuvring, but that is really not a problem for most marine diesels.

Joakim

Jaokam
It was pointed out to me that the relationship for power would be to the power 2 rather than linear. At the bottom end the controller voltage drop tends to linearise the relationship.

I did some cycling of the batteries to liven them up this week and have now got them producing 20A before stall. With this I was able to get 15Nm with a power input of 390W. The actual test data is attached as a photo. I also measured the weight of the torque arm and included half of this in the load for torque calculation. It weighed 0.3kg and is 505mm long.

The outcome is that it requires more like 1100W to produce twice rated torque because it is not linear.

Rick W