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Electric or Diesel-Electric Hybrid propulsion conversion viability


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IMO, the way of the Future will be fuel cells. We don't see much of this technology, but it is out there and major R&D is being placed on this technology. It offers the potential of most efficient conversion of Fuel to Energy in the smallest use of space of all systems available. The big negative on any system is that every time you convert one form of energy to another, you have a loss. For Solar, the first loss is the very poor conversion of Sunlight to Electrical energy. While the Sun is free to us, we see the inefficiency as size of panel and that fact we need to track the Sun to get the best conversion efficiency. Then there is the fact of the "Dark side of the Sun" creating our Night experience ;-)
then there is the loss in the Wiring, the Regulator, the charge/discharge of the storage system, the conversion and regulation to the correct Voltage to run an electric motor, the loss of the motor and the area and weight all this things take up.
So far, the largest storage of energy is still a ltr of Diesel. Take that to a ltr of any liquid Fuel that a Fuel Cell uses and we still see the largest storage of energy converted with the greatest efficiency directly to Electrical energy and then regulated to run a Motor and all of it being light weight and a small footprint.
 

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Biggest problems currently with the adoption of fuel cells are the lack of widespread availability of the fuel and $ per Ah. Definitely have potential though.

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Must be a night mare for the rudder bearings. The general laws of physics would have to say a prop mounted on the rudder isn't a good idea.

 

I'm sure it's fine for getting in and out of berths and anchorages, the classic light weight Med cruising, but I just can't imagine motoring any distance into a seaway or head wind with the prop mounted on the rudder.

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Must be a night mare for the rudder bearings.

 I would expect that if retrofitted to something never designed to have something like this, then yes maybe. But I would have expected this one designed to take the load. However, it can't surely be as large a load as the Boat Sailing would place on it. Ruffly 10% of the lift is generated by the Rudder alone. So when you think about the load hauling your Boat along and take 10% of that, it is far more than any little drive like that is going to do.

As for the position of the drive, that places it out fairly in a vulnerable place. We don't see it a lot in NZ, but many European Marinas have solid walls you have to back up. It's one thing to bump the wall with the transom, but big damage if you bumped the wall with the prop.

 

What intrigued me was 6 hours motoring and 3 hours sailing to recharge. Look at some of the figures quoted earlier in this thread

Sailing? Surely they would mean Shore power. It simply isn't possible otherwise. That is if they are saying Fully recharged. It defies all laws of physics otherwise.

 

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I would expect that if retrofitted to something never designed to have something like this, then yes maybe. But I would have expected this one designed to take the load. However, it can't surely be as large a load as the Boat Sailing would place on it. Ruffly 10% of the lift is generated by the Rudder alone. So when you think about the load hauling your Boat along and take 10% of that, it is far more than any little drive like that is going to do.

 

 

Yeah, but when motoring, the propeller has to produce 100% of the the force to move the boat. That force has to be transferred through the rudder bearings ( and rudder stock). Having sized and assessed the loads to replace my engine mounts, I'm fairly sure that the loads to propel a boat are substantial higher than the loads applied to the rudder while sailing. Based on your 10% number, which seems plausible, I'd say 100% has to go through the prop when motoring, which would be a ten fold increase in forces on the rudder (stock and bearings).

 

Either way, I'm not too worried, because there are so many fantastic 30 to 40 year old NZ boats at really good prices, to buy, so I def don't need to worry about these crazy euro trends...

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Loads on a rudder can be huge. On my boat, the load on the rudder at 20 knots is approx 3x the weight of the boat - if the rudder is hard over. No way a small engine could produce that force.

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Ok am I missing something?? looked at various site regarding electric driven propulsion.

Not one motor seems to be able to charge the battery bank,unlike a diesel with an alternator,the keep mention how you need a good bank of solar panels or a genset?

So the question is how long can you motor for or can you motor at night(no sun for panels)or can they actually charge as they discharge? What about use of electric capstans. 

The cost seems (to me)prohibitive when you need a charging device,battery bank,what would the battery bank weight be v diesel engine?

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In my search for a yacht, I've come across a few out there that are in need of a re-power due to a dead engine or having extremely high operating hours and my thoughts have turned to the viability of an electric or diesel-electric hybrid propulsion conversion. It definitely won't suit everyone's needs but I would think that there are situations where it would be a viable option like those that do longer passages, just use the motor around marinas and moorings or anchoring, etc. I think the load would also be a factor so electrical needs, yacht size and weight will have a bearing.

 

The biggest downside to the pure electric option would be reduced range and a slightly reduced cruising speed under power to help maximise the available range. Not ideal for those that must somewhere at a certain time but for those with more flexibility with their schedules and destinations and a desire to sail it's probably not a major issue. On the plus side, you could run it just enough to remove the impact of prop drag thus gaining a little extra sailing speed or alternatively use it in the regeneration mode to put a charge back into the batteries. This wouldn't be a huge amount and is dependent upon sailing speed but it might be helpful. Obviously, there are other charging options available such as solar, wind and hydro generators. You also get an opportunity to reduce noise, vibration and smell from the diesel and reduce the number of holes in your hull. 

 

Another potential downside is for those that run desalinators that aren't 12V so a generator would be required. My thought was a small diesel generator that could power the desalinator and/or recharge the battery bank when required but doesn't always have to run when you use the motor. Also, I'd think using a generator to run a desalinator or charge batteries etc. would make more sense than running an engine used for propulsion. Yes, it would mean a diesel engine back on the boat but the usage and requirements would be different and the diesel could also be used for heating.

 

Generally, the biggest hurdle seems to be the cost of batteries, particularly Lithium Ion which means you're effectively paying for your fuel up front. The electric motors, controllers, etc. aren't that expensive, heavy or bulky and spares could be carried. 

 

Are my thoughts on the right track and what am I missing?

The energy density of diesel fuel  is 13,333 watt hours per kg . For the current best Lithium Iron technology it is approx 200 watt hrs per kg. So diesel can deliver 66 x more energy per kg than lithium iron, that's the  brutal reality of the maths , you just cant store sufficient energy. Improved battery technology is aiming at 500 Wh/kg and that gets it down to 26 ;1 much better but still brutal. The electric motor is 90% efficient, the diesel perhaps 45% if using latest technology so that helps a bit. Diesel electric does not make sense, there would be transfer losses. The motor would likely be brushless to take advantage of the latest technology, the speed controller for that will be pricey and if it fails the motor is useless. The Speed Controller will need cooling as well as the motor. This could be a fan or liquid (the sea water) so more complexity there. On the plus side it would be quiet and smooth. Perhaps a fuel cell would be a better option ? 

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Oceanvolt system seems have several systems that seem to be well developed. Sailing produces some charge in the batteries, plus solar panels but it is hard to beat the energy content of diesel fuel.

http://oceanvolt.com/solutions/systems/sail-drive

 

looks simple enough,lightish, but could you power from coromandel to Auckland non stop without a generator,relying purely on solar,running fridge/freezer,at 5 knots . Why I say coromandel to AK is every time we sail over there is never any wind when we come home,3 times last season.

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The energy density of diesel fuel  is 13,333 watt hours per kg . For the current best Lithium Iron technology it is approx 200 watt hrs per kg. So diesel can deliver 66 x more energy per kg than lithium iron, that's the  brutal reality of the maths , you just cant store sufficient energy.

Excellent description Frank. Although I think actual space taken up is as important as weight. Batteries are getting lighter in weight, but the space they take up is large and not getting smaller. So 850grams of Diesel is taking up 1 ltr of space. Looking at the area taken up by a battery and the energy available in that same space, ( need coffee before calculating in my head) and you will see that the energy available in the Diesel is much greater than the battery.

 

Ok am I missing something?? looked at various site regarding electric driven propulsion.

Not one motor seems to be able to charge the battery bank,unlike a diesel with an alternator,the keep mention how you need a good bank of solar panels or a genset?

So the question is how long can you motor for or can you motor at night(no sun for panels)or can they actually charge as they discharge? What about use of electric capstans. 

The cost seems (to me)prohibitive when you need a charging device,battery bank,what would the battery bank weight be v diesel engine?

 

 

Yep that's the points I have been making from the beginning.

The things to always remember. The laws of physics tell us that everytime we convert energy from one for to anther, we cause a loss. That even includes changing rotation speed using gears in a gearbox, or a speed controller on an electric motor. Creating motion form any form of energy, then changing that energy into any other form of energy, can result in large amounts of loss.

     Even with Solar panels taking great leaps and bounds, the industry has a very long way to go before we will ever see, if even possible, high efficiency panels. But lets just say that some new material was found to make a 100% efficient panel. Sunlight has an energy of ruffly 1000W per square meter. So even with a 100% efficient panel, it needs to be 1 sqr metre to get 1000W and it can never get better than that. Consider the amount of Fuel you can store in that same area the panel takes up. We will make the panel the exact thickness to enable a total of 1ltr of Diesel over that area. That is still 13 (there abouts) more energy than the 100% efficient panel can ever provide.

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Not sure I follow your thoughts there wheels.

Are you saying if you take an alloy framed 1000w solar panel (assuming 100% efficient) say 30mm thick, an eqivilant volume of fuel has 13 times more energy? What if you left the panel in the sun for 13 hours? And yes, panels are not and likely will not soon be 100% efficient, so it might be more like 30 hours say, but I'd imagine most boats looking at deck storing fuel wouldn't be using that fuel for a week or two until they have used their main tanks anyway.

What happens when the solar panel is in the sun for 7, or for that matter 30 days?

 

Or have I misunderstood? I dont disagree with the point that diesel is the most cost and space efficient fuel, just confused by your example.

 

Frank, an electric motor cannot charge as it discharges, was that part of your question? Would take more energy to power the charger than the charger would produce, as wheels says, every time you convert energy there are losses, you'd be going electric to mechanical back to electric. When you run an alternator off a diesel, it uses more fuel.

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Apart from the installation cost, I see these benefits.

Most of my running is short trips to the start line or out fishing (2 hr trip) This could easily be accommodated with the electric motor setup.

For my summer cruise I would just fit a suitable genset to recharge batteries as necessary on the longer legs, use it to run appliances such as microwaves and toasters etc. efficiency on these trips are not such a big factor. 

It would save on weight for club racing etc.and diesel running costs would be reduced, any engine problems would be easier to fix by removing the genset from the boat.

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Not sure I follow your thoughts there wheels.

Are you saying if you take an alloy framed 1000w solar panel (assuming 100% efficient) say 30mm thick, an eqivilant volume of fuel has 13 times more energy? What if you left the panel in the sun for 13 hours? And yes, panels are not and likely will not soon be 100% efficient, so it might be more like 30 hours say, but I'd imagine most boats looking at deck storing fuel wouldn't be using that fuel for a week or two until they have used their main tanks anyway.

What happens when the solar panel is in the sun for 7, or for that matter 30 days?

 

Or have I misunderstood? I dont disagree with the point that diesel is the most cost and space efficient fuel, just confused by your example.

 

Frank, an electric motor cannot charge as it discharges, was that part of your question? Would take more energy to power the charger than the charger would produce, as wheels says, every time you convert energy there are losses, you'd be going electric to mechanical back to electric. When you run an alternator off a diesel, it uses more fuel.

The argument gets complicated depending on what you need the energy for and the rate of delivery of the energy (Power)

Solar panels are remarkable, I Love em !.  I use Lithium battery technology in another of my hobbies electric RC model aircraft.

these electric model airplane motors are brushless and their power using Lithium Polymer (LiPo) batteries is staggering, You can see videos on youtube of electric RC cars putting out 13 HP. (remember in a small model car !) they are also incredibly efficient more than double that of the very best heat engine, plus way less moving parts, less mechanical stress, etc etc.

So you can certainly deliver say 50 Hp or more with modern electric motors and  but not for many hours if you are drawing that power from a battery. The battery soon needs recharging and the solar panels simply cant charge at a high enough rate to compensate for the rate of demand. 

Battery technology as with solar panel development is continuously improving, large corporates are pouring billions into it.

Today we boaties can have a fridge and a freezer whose power demands can be meet by a reasonably sized solar panel which was unheard off say 15 years ago. So we are reaping the benefits of rapidly advancing technology maybe one day we will be able to say the same for our auxiliary engine but its going to need some big technology breakthroughs to overcome the energy density fundamentals. Now if you want real sustainable/usable power hoist those damn sails, have a big rig and an easily driven hull :-) 

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The argument gets complicated depending on what you need the energy for and the rate of delivery of the energy (Power)

Solar panels are remarkable, I Love em !.  I use Lithium battery technology in another of my hobbies electric RC model aircraft.

these electric model airplane motors are brushless and their power using Lithium Polymer (LiPo) batteries is staggering, You can see videos on youtube of electric RC cars putting out 13 HP. (remember in a small model car !) they are also incredibly efficient more than double that of the very best heat engine, plus way less moving parts, less mechanical stress, etc etc.

So you can certainly deliver say 50 Hp or more with modern electric motors and  but not for many hours if you are drawing that power from a battery. The battery soon needs recharging and the solar panels simply cant charge at a high enough rate to compensate for the rate of demand. 

Battery technology as with solar panel development is continuously improving, large corporates are pouring billions into it.

Today we boaties can have a fridge and a freezer whose power demands can be meet by a reasonably sized solar panel which was unheard off say 15 years ago. So we are reaping the benefits of rapidly advancing technology maybe one day we will be able to say the same for our auxiliary engine but its going to need some big technology breakthroughs to overcome the energy density fundamentals. Now if you want real sustainable/usable power hoist those damn sails, have a big rig and an easily driven hull :-)

Talking about sail power, while sailing back to the mooring  on a stinking hot summer day (what happened to those ?) I was over the side getting a tow and cooling off  The breeze was light,when I saw a slight puff moving towards the boat barely even ruffling the water. I figured with the boat towing a bucket (me) it would not lift the speed at all but as it hit the sails the boat heeled maybe another 3 deg and immediately picked up another knot like I wasn't even there. It left quite an impression on me as to the power the wind on your sails generate, even in light conditions and on a relatively small boat like a Carpenter 29. 

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Or have I misunderstood? I dont disagree with the point that diesel is the most cost and space efficient fuel, just confused by your example.

No, I am not explaining it very well. But I don't think I need to either as your reply shows that many of you have a good handle on it all anyway.

But Frank has pretty much nailed the point that, it all depends. It's different for everyone because everyone has different needs.

 

 

it would not lift the speed at all but as it hit the sails the boat heeled maybe another 3 deg and immediately picked up another knot like I wasn't even there.

Yeah there has been a few that have run into a lot of trouble doing that. Darn near losing their lives.

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