electic kW / diesel kW

[horry_bv]

hy
i am looking forward for an hybrid drive for an sailboat. i have seen on many articles from electric motors, that for example an electric motor of 10 kW can easely replace an diesel up to 40 kW.

I just can't find the right answer for that... ?

i just think maybe if the electric motor is forced and overheated, otherwise i can not see how an electric motor of 10kW to give the power of an diesel of 40 kW..

[brian eiland]

Use the 'search button' and look up "diesel electric" in quotes. It will surprise you with the amount of material.

For instances
http://www.boatdesign.net/forums/hybrid/diesel-electric-propulsion-sailboats-9310.html

Welcome to the forum

[gonzo]

Kw is a unit of power. It doesn't matter if the propulsion unit is electric or diesel. The power applied to the propeller is the only calculation that is important to calculate the size of the motor. The rating of the motor is another variable to consider. That is, if you want to have reserve power or run it at its maximum.

[marshmat]

Hi horry_bv, welcome aboard :)

The simple answer is that a kilowatt is a kilowatt. The thing on one end of the shaft (a propeller) has absolutely no idea what is on the other end of the shaft, nor does it care. All it cares about is that the shaft is delivering the proper torque at the proper RPM.

This perception that an electric drive can have a lower power rating than a diesel or gas engine exists for several reasons. One is that most people won't run an engine at full throttle, and most designers and engineers will choose an engine so that, at cruise speed, it's running well below full throttle. 1/2 to 3/4 of WOT is where most people tend to run their boat engines. (Note that if you size the electric motor for full power at your cruise speed, you won't have the reserve power that the final 1/4 of the throttle arc gives you when you need to claw off a lee shore or whatever.) Now, that engine is also turning auxiliary gear- alternators, maybe a hydraulic pump- that can sap a fair bit more power. In the electric boat, these loads draw directly from the battery (which must be sized accordingly).

The types of electric motors used in hybrid drive systems tend to produce very high torque at low RPM. Thus, in manoeuvring situations, an electric can 'feel' like it produces as much thrust as a diesel with a higher peak power rating. Of course, if you push the throttles of both the 10 kW electric and the 30-40 kW diesel boat fully forward, the difference will become quite apparent.

A rule of thumb sometimes used to determine whether a hybrid system is worth considering is:

Calculate the total energy demand of all your onboard systems, based on their power demand and how much you use them: lights, instruments, radar, watermaker, A/C, whatever. You'll get a number probably in kWh per day, or per week.

Now calculate the energy demand of your propulsion system. How many kilowatts of power, for how many hours. Use the power setting you actually run at (it'll probably be an educated guess), not the peak power of your installed engine. Consider how long you run under engine, and get a figure in kWh/day or kWh/week.

Now, if these two figures- house (or hotel) load and propulsion load- are somewhat comparable, or if house load is higher, then it's possible- BUT NOT FOR SURE- that diesel-electric or some other hybrid system could work for you. Cruise ships, for instance, tend to fall in this camp, and reap very substantial cost savings from their multi-diesel-generator, multi-electric-drive-pod systems.

If, as is the case for many leisure craft, the propulsion load outstrips the house load by more than an order of magnitude, it is highly unlikely that electrifying your drivetrain would yield efficiency improvements commensurate with the cost and weight of the equipment. Indeed, a hybrid drive in such a boat could very well be noticeably less efficient than a straight shaft with a good gearbox and prop.

There are, of course, exceptions- folks who want silent running, or travel on restricted waterways that don't allow engines, will obviously go electric even if it is heavier and/or more expensive.

[mydauphin]

Also remember these Murphy's law,
A diesel is lot easier to keep dry than a electric motor...
A diesel fuel tank never loses charge...
The bad weather will invariably happen when your batteries are low, and you will wish the extra speed a diesel would have given you...
A diesel engine boat will always find a buyer and home port...

[Guest625101138]

hy
i am looking forward for an hybrid drive for an sailboat. i have seen on many articles from electric motors, that for example an electric motor of 10 kW can easely replace an diesel up to 40 kW.

I just can't find the right answer for that... ?

i just think maybe if the electric motor is forced and overheated, otherwise i can not see how an electric motor of 10kW to give the power of an diesel of 40 kW..

A diesel engine rated at 40kW will produce that power at its shaft at the rated rpm. This will not align with its peak torque. The peak torque will be at roughly 80% of rated rpm. The torque available at lower rpm will be considerably lower. Also some IC engine ratings are given without allowance for auxiliary loads such as water pump, oil pump, fuel pump and generator. The power available at the shaft is less than the rating. All IC engines start wearing at day one and, apart from a brief period of freeing up, they are on a downhill slide until they are overhauled. So in operation they only delivered factory rating in the first few hundred hours. After a few thousand they will be down by maybe 10% and fuel consumption up by even more.

In matching a propeller to a diesel engine it is usual to target peak power to be delivered close to peak rpm in calm conditions. The engine will not be able to deliver peak power once the prop loads up in heavy weather. It could even be that the engine will not get to peak torque but this would be unusual and likely the boat overpropped to get efficiency.

Typical electric motors are able to deliver 2 to 3 times rated torque through their rev range. Some are built to get over 5 times rated torque for certain applications but they will be heavy. Electrics motors maintain their power output throughout their life. The rating is based on the ability to keep the frame cool. Usually this is based on 40C ambient in still air. In cooler locations with forced ventillation the available power increases. The power rating is what will be delivered; no auxiliary loads rob power.

So electric motors have some advantages in terms of comparison with IC engines from the nameplate rating. Saying 40kW IC is equivalent to 10kW electric cannot be a blanket statement. It has to consider the basis of comparison.

As an example you will see electric dragsters with a fraction of the rated power of IC dragsters doing better times as this sort of application brings out the huge torque advantage of an electric motor. You only need a motor with enough torque to spin the wheels, set the current limit to produce that torque value, have enough voltage to get the required top speed and you can have the wheels on the verge of spinning throughout the time it takes to cover 1/4 mile. The IC has to be revved, clutch dropped in the most uncontrollable fashion and possibly a gear change at some point in the 1/4 mile.

Rick W

[M-Sasha]

A diesel engine boat will always find a buyer...

If I may add:

and home!

Sasha

[COOL Mobility]

Due to the constant power of an electric, larger diameter props with higher pitch are used. These are more efficient, with less slip so power is delivered with much les losses (including the ones listed above).

If you put the same prop on a diesel, it would not get up to its reasonable torque band efficient range. Hence performance is much better KW for KW due to the contant high torque.

With IC motors, same Hp motors may develop different torque curves that show that torque and power are not directly linked.

Go with non smelly electric and your yacht will not have that distinctive aroma of diesel fuel!

Colin

[Questor]

Due to the constant power of an electric, larger diameter props with higher pitch are used. These are more efficient, with less slip so power is delivered with much les losses (including the ones listed above).

If you put the same prop on a diesel, it would not get up to its reasonable torque band efficient range. Hence performance is much better KW for KW due to the contant high torque.

With IC motors, same Hp motors may develop different torque curves that show that torque and power are not directly linked.

Go with non smelly electric and your yacht will not have that distinctive aroma of diesel fuel!

Colin

This leads to the question, How easy is it to find propellers that are optimally designed for electric drive ?

[marshmat]

This leads to the question, How easy is it to find propellers that are optimally designed for electric drive ?
Assuming you're talking inboards, and not outboard motors like the Torqeedo: As easy as it is to find propellers for any other inboard engine. If you have a particular boat that needs __ kN of thrust at a boat speed of __ knots, with a maximum diameter of __ cm and a prop shaft that spins at __ rpm, it doesn't matter whether that shaft is spun by an electric motor, or by a gear reduction from a diesel, or by thousands of hamsters in little wire wheels. The prop will be the same.

What can be hard to find, at times, is large diameter, low RPM, low power props. There are some efficiency gains to be had by going to large diameter and high-aspect-ratio blades in some low power applications, but since there are so few low-power boats around that can swing such large props, they are not necessarily easy to find. Rick Willoughby has built a few such props for his own experimental boats.

[FAST FRED]

"multi-electric-drive-pod systems."

Also figured into the ships DE "savings" is the lack of need for tugs to assist berthing and departing every day with the az-pods.

"Due to the constant power of an electric, larger diameter props with higher pitch are used. These are more efficient, with less slip so power is delivered with much les losses (including the ones listed above)."

IF a vessel is designed to be fitted with large diameter props , the diesels are easy to fit a 6-1 or deeper reduction gear.

Big problem is on a sail boat there are not folding props , so the more expensive CPP would be required.

While "co generation" can be done the drag from a 36 to 60 inch prop would be similar ( But worse) to sailing with a drogue that diameter.

FF

[COOL Mobility]

There are no opimal props, apart perhaps from the Torqueedo prop, which is much larger diameter than other 'trolling motor props" they are up to 12" diameter with two to three blades with considerable surface area and pitch. The only way is trial and comparison as the rules are new and too many variables like hull speed and force required to reach close to hull speed.

As you'll see on Electric Boats Forum, you want to turn as big a prop as you can, dependant on gearing, motor and drive, with a high pitch, sometimes pitch close to diameter.

It depends upon many factors such as boat length, displacement etc, but an IC and their clutched gearboxes are much less efficient at turning a KW of energy input into a %KW output. Like a car, it is power ar the wheels that counts. A larger diameter, surface area & pitch prop has less slip in the water, hence better efficiency by far. An IC engine could not get a prop that large turning at its low power low revs, whereas an electric with basically a flat power curve can - hence why a smaller rated electric can equal a larger output IC.

Note though, this is for up to hull speed only, for planing speeds, an IC Wins!

[apex1]

An IC engine could not get a prop that large turning at its low power low revs, whereas an electric with basically a flat power curve can - hence why a smaller rated electric can equal a larger output IC.

Note though, this is for up to hull speed only, for planing speeds, an IC Wins!

Thats quite not the full truth!:D
The CPP is the (close to) perfect prop when DE doesn´t make sense. (and it never does in a yacht)

Regards
Richard

[Questor]

There are no opimal props, apart perhaps from the Torqueedo prop, which is much larger diameter than other 'trolling motor props" they are up to 12" diameter with two to three blades with considerable surface area and pitch. The only way is trial and comparison as the rules are new and too many variables like hull speed and force required to reach close to hull speed.

As you'll see on Electric Boats Forum, you want to turn as big a prop as you can, dependant on gearing, motor and drive, with a high pitch, sometimes pitch close to diameter.

It depends upon many factors such as boat length, displacement etc, but an IC and their clutched gearboxes are much less efficient at turning a KW of energy input into a %KW output. Like a car, it is power ar the wheels that counts. A larger diameter, surface area & pitch prop has less slip in the water, hence better efficiency by far. An IC engine could not get a prop that large turning at its low power low revs, whereas an electric with basically a flat power curve can - hence why a smaller rated electric can equal a larger output IC.

Note though, this is for up to hull speed only, for planing speeds, an IC Wins!

The more I look into this subject , the more it appears that trial and error is the rule. Even an issue as basic as batteries is mind boggling. I looked up the performance of a battery described as 1225 Amp and found that the 1225 Amps is for only 5 seconds. When I buy batteries at my favorite automotive shop a 400 Amp battery will deliver 400 Amps for 20 minutes. If I buy a 225 Amp battery at my favorite industrial supply it will deliver 225 Amps for 1 hour. According to a convincing report I read this morning a lead acid battery delivers a maximum 20 watts per kilo for 1 hour while the latest state of the art battery delivers up to 140 watts per kilo for 1 hour. Most of the other battery technologies described seem to fall between 70 and 100 watts for 1 hour per kilo.

The next mind numbing battery issue is charging. If you don't charge your batteries with the proper peak Amperage as part of each charging cycle you could destroy them in less than a month.

The third issue of concern to me is maximum safe point of discharge. I have an unserviced cabin in the country. I bought a 12 volt to 110 volt power converter so I could use deep cycle auto batteries to watch movies there. The salesman assured me that the battery protector would trip the circuit before the battery could be damaged. After 2 evenings the battery was a stone that refused to charge. I tried a second battery and it did the same thing becoming a total stone after only 2 evenings. ( The two batteries in question came from a 1 ton diesel truck I parted out. The batteries were in reliable daily use in the truck up to the day I removed them for use at the cabin. ) That ended movies at the cabin.

[CDK]

I have an unserviced cabin in the country. I bought a 12 volt to 110 volt power converter so I could use deep cycle auto batteries to watch movies there. The salesman assured me that the battery protector would trip the circuit before the battery could be damaged. After 2 evenings the battery was a stone that refused to charge. I tried a second battery and it did the same thing becoming a total stone after only 2 evenings. ( The two batteries in question came from a 1 ton diesel truck I parted out. The batteries were in reliable daily use in the truck up to the day I removed them for use at the cabin. ) That ended movies at the cabin.

Too much confusion.
First of all there is no such thing as a deep cycle auto battery.
Your two batteries were old automotive ones. They were usable in the truck because all they had to do was deliver starting current for a few seconds; their capacity may already have been reduced to 10% of what is printed on the label.

If you draw more than 1/10th of a battery's rated capacity, there is a 2-way penalty: the capacity is reduced and so is the life expectancy.

I have a backup system because there are many blackouts and I don't like sitting in a cold and/or dark house.
So I use a 200 Watts solar array, 250 Ah battery, an inverter and an automatic charger that delivers 25 Amps whenever the voltage reaches 10.5 and the power grid is working. The central heating always gets its power from this system, TV and lights normally use the grid.

I use good quality car batteries, but the discharge cycle are in fact to deep, so there is a lot of wear. After 4 years I replace them; they still work but have lost so much capacity the inverter starts buzzing if I switch on the TV and lights. But I can still use them to start a car!

[Questor]

Too much confusion.
First of all there is no such thing as a deep cycle auto battery.
Your two batteries were old automotive ones. They were usable in the truck because all they had to do was deliver starting current for a few seconds; their capacity may already have been reduced to 10% of what is printed on the label.

If you draw more than 1/10th of a battery's rated capacity, there is a 2-way penalty: the capacity is reduced and so is the life expectancy.

I have a backup system because there are many blackouts and I don't like sitting in a cold and/or dark house.
So I use a 200 Watts solar array, 250 Ah battery, an inverter and an automatic charger that delivers 25 Amps whenever the voltage reaches 10.5 and the power grid is working. The central heating always gets its power from this system, TV and lights normally use the grid.

I use good quality car batteries, but the discharge cycle are in fact to deep, so there is a lot of wear. After 4 years I replace them; they still work but have lost so much capacity the inverter starts buzzing if I switch on the TV and lights. But I can still use them to start a car!

Diesel powered trucks are equipped with deep cycle batteries. I've used and sold a lot of used ones from the vehicles I've salvaged and I've bought them new when I had to. Over the years I have known many people that have bought them new for solar applications and quickly destroyed them because either their protector failed to shut down before they were too deeply discharged or their solar system couldn't deliver high enough charges.

The original poster's original question addresses the fact that there is a lot of confusion out there as a result of the multiple ways in which outputs and capacities are described. I believe unscrupulous retailers and manufacturers are deliberately creating the confusion so that they can market inadequate products to the gullible. I am reminded of a light roof top boat with a battery powered electric trolling motor my father bought many years ago for hunting. He and his friend proudly cruised across a lake with it to previously inaccessable areas.On the way back there was a heavy wind and they couldn't get 20 feet from the shore with it. Unwilling to leave his new thousand dollar toy behind they jumped into the swampy water and towed it across the swampy edges of the lake. Several hours later they came home frozen and covered in mud. Over the years since them I've met at least a dozen other hunters that have shared his experience.

I do believe that there are alternative technologies out there that could significantly reduce fuel waste but there are also a lot of totally useless products in the marketplace that are being grosslly over rated by retailers as well. I have acquired a lot of them over the years.

[CDK]

I believe unscrupulous retailers and manufacturers are deliberately creating the confusion so that they can market inadequate products to the gullible.



There are plenty of sites explaining battery behavior. A true deep cycle battery cannot be used to start engines.

But I looked at the Exide website and see many types for North America that are sold as dual purpose. The "deep cycle" label justifies a higher price, nothing else. So your above statement applies to these products as well.

In my opinion, only Exide Orbital and Megacycle are true deep cycle batteries. You'll never find these in a truck.

[Questor]

There are plenty of sites explaining battery behavior. A true deep cycle battery cannot be used to start engines.

But I looked at the Exide website and see many types for North America that are sold as dual purpose. The "deep cycle" label justifies a higher price, nothing else. So your above statement applies to these products as well.

In my opinion, only Exide Orbital and Megacycle are true deep cycle batteries. You'll never find these in a truck.

There are major differences between conventional auto batteries and deep cycle diesel batteries.I've handled thousands of them and seen many of them after they have been broken open. Some car batteries have only a thin filament printed upon a plastic insert. Others have tissue thin plates that crumple as easily as tin foil. Deep cycle diesel battery plates appear to be 10 to 40 times thicker than what I see coming out of the average car.When I take automotive batteries in for scrap to my chosen broker I get between $6.00 and $30.00 each for them. The broker tells me he sometimes loses money on the six dollar minimum per battery he pays but his margin on the heavier batteries more than compensates for losses on light weight batteries. The value of the scrap battery is in the lead.

There are major differences between deep cycle diesel batteries and the average car battery. Whether the term deep cycle is a misnomer or not I don't know but I do know there is a very substantial difference between the two.When I find broken open deep cycle marine batteries they seem to have the same heavy plates as the deep cycle diesel batteries.I can't visually recognize alloy differences but apart from that they look and weigh the same.

[marshmat]

I do believe that there are alternative technologies out there that could significantly reduce fuel waste but there are also a lot of totally useless products in the marketplace that are being grosslly over rated by retailers as well. I have acquired a lot of them over the years.
Yep, Q, you're probably right about that. There is a lot of junk out there, mixed in with a few really well-engineered gems, and it becomes hard to pick the wheat from the chaff.

It's also probably worth noting that good engineering (for a particular purpose) plus misguided marketing usually results in perceived sh*tty engineering. The trolling motor is a perfect example- it's perfect for what it's meant to do (pull an 18' sport boat along at 0.8 knots for an hour or two) but is easily mis-marketed into disaster (as in Q's story above).

[jonr]

Maybe people should buy batteries by weight or by density.

[FAST FRED]

"Maybe people should buy batteries by weight or by density."

The best is to purchase the batts FOR the Service needed

Starting batts excel at creating loads of amps , with small voltage drop for a few seconds. Discharge starts below 60% full and you have FOREVER decreased their service life and capacity.

Deep Cycle , golf cart or industrial fork lift batts can be regularly discharged 50% of their 20 hour rate .

BUT they should be recharged soon.

Batts MUST be recharged to 100% full, (either style) or they will loose capacity and service life.
This is always a slow process for the last 15% to get pushed in.

FF

[apex1]

There are major differences between conventional auto batteries and deep cycle diesel batteries.

Thats true, there are significant differences beween a ordinary starter battery (what you name "auto battery") and a deep cycle battery. (diesel batteries are not on the market).

But you have not seen a single one of the latter in any truck you are referring to! No matter how many thousands of them you have seen or replaced, they ALL have been simple starter batteries (most probably of different quality), not deep cycle! A deep cycle does not fit to start your truck (and a starter battery does not bear with your hotel load).
Therefore your "deep cycle diesel" battery is either a marketing gag or just phantasy.

To get a better idea about the topic you might like to have a look here:
http://www.victronenergy.com/support-and-downloads/white-papers/
download "energy unlimited" and enjoy a good read.

Regards
Richard

[sparky_wap]

These are true deep cycle batteries. Not too hard to get 10kw out of one of these packs for an extended time. Will weigh a couple of tons but not expensive second hand (like EBay). I understand the (home) solar community is using these because of cycle life and their low second hand cost. Cost seems to be under $0.10 US. Proven, but heavy technology. Also, they do release hydrogen - be careful.

[FAST FRED]

Deep cycle batts will indeed start a diesel . The difference is the plate surface area.

The D-C have few quite thick plates to handle the cycling so their surface area is limited.

However as house batts there are usually a number of batts , so the combined surface areas is similar.

It may take 6 deep cycle batts to have the plate area of two start batts , but folks with trucks or boats that LIVE off the house set have them anyway

For years we operated with NO starts , hust a big house set with no problems.Startibng a 6-71 with the house at 50% or less.

Today it could be more difficult as the engines with electronic injection MUST have great voltage to operate.

On trucks its (2) Series 31 that is usually chosen.

The simpelest way to decide what the Mfg thought the batts were for is to read the rating.
If its CCA (cold crank amps) its a start batt ,
If the rating is a "20 hour rate" its a deep cycle.

Deep Cycle Batteries
www.trojanbattery.com or www.dcbattery.com/rolls.html


Or from the charger site,

2.3.3. The flat-plate automotive battery (flooded) This is the battery used in cars. Not suitable for frequent deep discharging as it has thin plates with a large surface area – designed purely for short-term high discharge currents (engine starting). Nevertheless flat-plate heavy-duty truck starter batteries are often employed as house batteries in smaller boats.

2.3.4. The flat-plate semi-traction battery (flooded) This battery has thicker plates and better separators between the plates to help prevent buckling of the plates and shedding of the active material under cyclic use. It can be used for light duty cycling and is often referred to as a ‘leisure’ duty battery.

2.3.5. The traction or deep-cycle battery (wet) This is either a thick-plate or a tubular-plate battery. Used for example in forklift trucks, it is discharged down to 60-80% every day and then recharged overnight – day after day. This is what is referred to as cyclic duty. The deep-cycle battery must be charged, at least from time to time, at a relatively high voltage. How high depends on chemical and constructive details and on the charging time available.

FF

[Mr. Know-It-All]

Your replacement for a 40 kW diesel would be (more or less) a 40 kW electric engine. Fortunately, for the electric engine salesmen, physics do not apply to their engines. But physics might apply to yours!

[COOL Mobility]

Mr Know It All, you are under the incorrect information.

Electric engines are so much more efficient than IC, especially regarding torque, that comparison of horsepower ratings have little relevance.

For example, on "Lean Green Machines" TV show, a worked modern V8 RangRover 4x4 couldn't accelerate over 100m or handle a rough track climb as fast as an old Land Rover with a 20HP rated electric motor! Suck on that comparison and over 250 HP in a modern suspension 4x4 is beaten in torque challenges by 20HP of electric motor. The Range Rover did beat the Land Rover 'just' in the twisting track and rock climb race and the articulation challenge, where its modern suspension and handling made a huge difference.

HP and Torque are different values. Efficiency and relevance to the task is the reality. Electroic boats turn large high pitch props that an IC (diesel or petrol) would stall trying to get turning. These props have much less 'slipage' or cavitation in water and are quantum amounts more efficient.

You need to learn more about motors used to drive Electric Vehicles on land or water, then you will not be so classicly misinformed...

[FAST FRED]

For example, on "Lean Green Machines" TV show, a workled modern V8 RangRover 4x4 couldn't accelerate over 100m or handle a rough track climb as fast as an old Land Rover with a 20HP rated motor!

IF its an old gas motor the "hp" rating has no reality , it was a con for the TAX MAN.

FF

[COOL Mobility]

I give up on you guys. You are fixated on your misapprehension that "Gas is good, electric -bad!. Grunt, grunt!"

Trying to reason with you about the benefits of electic drives is hopeless. The fact that modern cruise liners, with their tight budgets, use diesels only to make electricity for the ship and their MORE EFFICIENT electric pod motors is lost on you..

Just remember that the world isn't flat anymore either!!

[apex1]

The fact that modern cruise liners, with their tight budgets, use diesels only to make electricity for the ship and their MORE EFFICIENT electric pod motors is lost on you..!

That statement is wrong, sorry.

Cruise ships have a very high Hotel load which makes it sensible to go DE, nothing else.

Regards
Richard

[Mr. Know-It-All]

I almost never do rough track climbs with my boat and must admit I don't know if an electric motor would propel it better in that situation.

I like sailing and hate the diesel engine in my boat. It is noisy, smelly, need a lot of maintenance, etc. Some electric motors are maintenance free. The problem is that I cannot buy reasonably priced batteries and my extension cord is only 100 feet long. So I end up with an IC anyhow. Connecting the IC directly to a propeller (via a gearbox), is the best solution for me, since it requires the least maintenance.

Despite that I want to replace my engine with an electric motor, I don't resort to wishful thinking.

I think you don't understand what torque and horsepower is. They are DIRECTLY related, i.e., if you know the torque at a certain RMP, you can calculate how much power the engine is producing at that RPM.

The props you are referring to is only a bit more efficient. Also very large props don't fit on many sailboats. A gasoline or diesel engine have no problem turning them. It is only a matter of gearing.

I will also try to explain WHY an electric motor can accelerate so well. Since the torque (at the RPM) x RPM is the power, if the V8 is not allowed to reach high RPM, it will not produce high power. The electric motor may reach it's 20 HP at low RPMs and hence the average power over the competition might be equal for the V8 and the electric motor. If the V8 had a different gearbox (such as CVT), it could run at an RPM where it produces more power. You must remember that there are many other factors affecting speed as well, traction, weight, etc....

In my boat, my diesel is allowed to reach the RPM at which it produces the maximum power. I need (but very seldom) the maximum power in certain situations and if I replaced my diesel, I have to buy an electric motor with the same MAXIMUM power.


Efficiency and torque have no direct relation. Efficiency is how well you convert energy, such as the energy in diesel to movement, or energy in batteries to movement.

If you read my post thoroughly, you will understand why "high torque" is more important for cars than for boats.




Mr Know It All, you are under the incorrect information.

Electric engines are so much more efficient than IC, especially regarding torque, that comparison of horsepower ratings have little relevance.

For example, on "Lean Green Machines" TV show, a worked modern V8 RangRover 4x4 couldn't accelerate over 100m or handle a rough track climb as fast as an old Land Rover with a 20HP rated electric motor! Suck on that comparison and over 250 HP in a modern suspension 4x4 is beaten in torque challenges by 20HP of electric motor. The Range Rover did beat the Land Rover 'just' in the twisting track and rock climb race and the articulation challenge, where its modern suspension and handling made a huge difference.

HP and Torque are different values. Efficiency and relevance to the task is the reality. Electroic boats turn large high pitch props that an IC (diesel or petrol) would stall trying to get turning. These props have much less 'slipage' or cavitation in water and are quantum amounts more efficient.

You need to learn more about motors used to drive Electric Vehicles on land or water, then you will not be so classicly misinformed...

[CDK]

Efficiency and torque have no direct relation. Efficiency is how well you convert energy, such as the energy in diesel to movement, or energy in batteries to movement.



Wrong!
IC engines have max efficiency at max torque. Electric motors, series wound or permanent magnet types, have zero efficiency at max torque (blocked state).

[Mr. Know-It-All]

Wrong!
IC engines have max efficiency at max torque. Electric motors, series wound or permanent magnet types, have zero efficiency at max torque (blocked state).

Well, an electric motor usually have it's efficiency peak at 75 % of max RPM. Max power is usually produced at 50 % of max RPM. For IC:s, the maximum efficiency is usually in the neighborhood of 70%-80% of peak torque.

[CDK]

Please explain these figures.
At least you contradict yourself here.

[Mr. Know-It-All]

The efficiency of a motor is how well it converts input power to output power. Here is an example which I found on Google: http://www.engineering.sdsu.edu/~hev/motor.html

Assuming the motor revs up to 12000 RPM, the efficiency peak for this motor is reached at 70%, which is close to 75%. Peak power is reached at 50% of max RPM. I said torque and efficiency is not directly related. And they are not.

The power for an electric motor is (usually) not increased if you rev it beyond a certain point. That is because there will be a linear drop in torque if you rev it. Torque will decrease at the same rate RPM increases, so no net gain in power.

For an internal combustion engine, you will usually see a decrease in torque as well if you rev it high enough. Some engines may produce LOWER power for a higher RPM, but that is usually only true if you are close to maximum RPM.

Lastly, we have the efficiency for an internal combustion engine. Again, there is no direct relation, but a rule of thumb, and these are always subject to change. Here is a chart: http://ecomodder.com/imgs/geo-1L-bsfc-chart-reconstruction.gif (they were hard to find) describing torque, v.s., RPM, v.s. fuel consumption for a specific engine. As you see from the chart, there is no direct relation. Clearly the peak torque is reached at 3300 RMP and the best fuel consumption is around 2700 RPM. That is, max efficiency is reached around 80 % of the RMP where peak torque is produced.

[mydauphin]

Also remember these Murphy's law,
A diesel is lot easier to keep dry than a electric motor...
A diesel fuel tank never loses charge...
The bad weather will invariably happen when your batteries are low, and you will wish the extra speed a diesel would have given you...
A diesel engine boat will always find a buyer and home port...


I can't believe this thread is still going. But let me add there should be a big difference between Marine and Non-Marine batteries. Marines batteries should be better built and take the inevitable pounding that a car or golf cart battery might not take. Remember you still need to charge your batteries. If anyone is serious about an electric boat you need something similar to what a Hybrid car has except regeneration circuits that wouldn't work. You need high voltage systems and batteries beyond just deep-cycle.

[CDK]

Lastly, we have the efficiency for an internal combustion engine. Again, there is no direct relation, but a rule of thumb, and these are always subject to change. Here is a chart: http://ecomodder.com/imgs/geo-1L-bsfc-chart-reconstruction.gif (they were hard to find) describing torque, v.s., RPM, v.s. fuel consumption for a specific engine. As you see from the chart, there is no direct relation. Clearly the peak torque is reached at 3300 RMP and the best fuel consumption is around 2700 RPM. That is, max efficiency is reached around 80 % of the RMP where peak torque is produced.

When discussing electric motors, the drawing board figures from a company like AC-Propulsion have little meaning; these guys love to mix peak pulse currents with no load voltages. They either do that on purpose to impress the reader with large numbers or they don't know what they are talking about. You might as well use the Enterprise's warp drive to make your point.

As for IC engines, here is a graph for a modern diesel engine as built by Steyr in Austria. The point of peak efficiency is exactly where any engineer would expect it to be in a well tuned engine.

[Mr. Know-It-All]

From the diagram in your own example, peak efficiency is at 2500 RMP. For me it looks like peak torque is reached at 3250. Maximum efficiency is at 77 % of peak torque. I think you are reading the diagram in the wrong way. Peak efficiency is were the engine consumes the LEAST fuel per unit of power produced, i.e., in your diagram at 2500 RPM.

For the electric motor, 75 % of max RPM is only a rule of thumb.


When discussing electric motors, the drawing board figures from a company like AC-Propulsion have little meaning; these guys love to mix peak pulse currents with no load voltages. They either do that on purpose to impress the reader with large numbers or they don't know what they are talking about. You might as well use the Enterprise's warp drive to make your point.

As for IC engines, here is a graph for a modern diesel engine as built by Steyr in Austria. The point of peak efficiency is exactly where any engineer would expect it to be in a well tuned engine.

[Mr. Know-It-All]

I can't believe this thread is still going. But let me add there should be a big difference between Marine and Non-Marine batteries. Marines batteries should be better built and take the inevitable pounding that a car or golf cart battery might not take. Remember you still need to charge your batteries. If anyone is serious about an electric boat you need something similar to what a Hybrid car has except regeneration circuits that wouldn't work. You need high voltage systems and batteries beyond just deep-cycle.

To hopefully kill of the thread, I will post a table containing energy densities: http://en.wikipedia.org/wiki/Energy_density

If you look in the table, diesel contain 46.2 MJ/kg. Lead acid batteries is at 0.13 MJ/kg. It it not feasible to use lead acid batteries. It never will be. If you can use 25% of the energy in diesel, it is still, by weight, 100 times the energy stored in a lead acid battery. You clearly need Li-ion batteries or better. These batteries will probably not be available, at reasonable prices, for a very long time.

[FAST FRED]

The problem with the Styer info is there is no info on weather the 2500 fuel consumption number is for max load at that rpm , or the minor power of the prop graph.

Big difference between having 80 hp for loads or 36hp.

Again a Fuel Map or BMEP graph is needed , not a prop graph.

FF

[Mr. Know-It-All]

As you say, optimize everything is not possible using this information. Since you know the torque (from the diagram) at the maximum efficiency, you know the power output. The engine will only run maximum efficient at that power output.

It is also impossible to say if 2500 RMP:s is most efficient for your particular boat. So this information alone is quite useless.

The problem with the Styer info is there is no info on weather the 2500 fuel consumption number is for max load at that rpm , or the minor power of the prop graph.

Big difference between having 80 hp for loads or 36hp.

Again a Fuel Map or BMEP graph is needed , not a prop graph.

FF

[apex1]

Anyone remembering the original question?

hy
i am looking forward for an hybrid drive for an sailboat. i have seen on many articles from electric motors, that for example an electric motor of 10 kW can easely replace an diesel up to 40 kW.

I just can't find the right answer for that... ?

i just think maybe if the electric motor is forced and overheated, otherwise i can not see how an electric motor of 10kW to give the power of an diesel of 40 kW..

The simple answer was:

the statement is false, and hybrid systems on boats are not feasible at present.

Period

[COOL Mobility]

Well that would be a surprise to the many members of the Electric Boats Forum http://groups.yahoo.com/group/electricboats/ of which many have successfully converted their stinky deisel yachts to clean electrics. These range from small yachts to 50 foot catamarans in the Bahamas, clean, green and fully tested and functional.

Established in 1998, it now has nearly 4,000 members and a wealth of information in over 15,000 postings.

Have a read and you'll find many 30' yachts with 5KW to 20 KW motors that are now electric powered. Some use the numerous commercial kits, other home built but real functioning examples, with pictures and performance data. If they were not feasible, why are people with full electric and hybrid (using gensets) yachts happy?

Also how are the various manufacturers of commercial systems surviving, let alone thriving?

Lead Acid batteries are the norm, but some have invested thousands in LiFePO4 battery packs.

Read their stories, look at photos and videos and decide for yourselves.

[apex1]

That is all nice.

And all worthless.

None of these boats have a comparable performance to IC engines.

But it is mute to discuss Hybrid systems again and again.

There are the believers which simply ignore the fact that it is impossible to store enough energy on board, and the professionals which are not as blind.

Hybrid propulsion does not exist on boats capable of coastal cruising. period

Regards
Richard


Well that would be a surprise to the many members of the Electric Boats Forum http://groups.yahoo.com/group/electricboats/ of which many have successfully converted their stinky deisel yachts to clean electrics. These range from small yachts to 50 foot catamarans in the Bahamas, clean, green and fully tested and functional.

Established in 1998, it now has nearly 4,000 members and a wealth of information in over 15,000 postings.

Have a read and you'll find many 30' yachts with 5KW to 20 KW motors that are now electric powered. Some use the numerous commercial kits, other home built but real functioning examples, with pictures and performance data. If they were not feasible, why are people with full electric and hybrid (using gensets) yachts happy?

Also how are the various manufacturers of commercial systems surviving, let alone thriving?

Lead Acid batteries are the norm, but some have invested thousands in LiFePO4 battery packs.

Read their stories, look at photos and videos and decide for yourselves.

[mydauphin]

Dude even electric bow thruster are more unreliable than hydraulic. There is a difference between boutique boats and crossing open bodies of water and surviving the inevitably little storm.

[marshmat]

Has this thread jumped the shark yet?

What started as a straightforward engineering question with a straightforward technical answer has turned into name-calling and accusations of stupidity and ignorance. Please, guys, we're all above this sort of bickering.

It was established within the first six posts that electric drive can work if well engineered, that it has certain limitations that must be understood, that it's ideal for some applications and useless for others, and that a kilowatt is a kilowatt regardless of what type of device is connected to the shaft.

Let's stick to logical, technical discussion on the thread and take the bickering to private messages. OK?

[apex1]

Have not seen name calling here Matt.

[kerosene]

HP and Torque are different values. .

Do you know what is the relation of hp and Nm - as in relation of power adn torque? By definition?

torque*multiplier(for correct units)*rpm=power

It really is that simple. That means BY DEFINITION that exact same torque can be geared for output from different sources regardless of their shaft torque if they have same power output.

The only aspects that benefit electric in the comparison:
- e-motors often rate for 24/7 output and if well cooled they can temporarily produce way over rated hp. Assuming the controller etc. can provide the juice.
- in some applications the current IC setup has very inefficient gearing so the motor works in a rpm range where it cannot provide even near its rated power.

[COOL Mobility]

Power curves for Internal Combustion Engines are not fully linearly related to the torque curves and vary dramatically over the rpm range of an ICE. This is why there is such a "sweet range" of ICEs where power and torque are optimal, but at lower revs the torque is severely impacted and the power decreases. At very low revs of below around 600rpm the motors stall.

Electric motors tend to have much flatter power and torque curves giving them the ability to turn a reasonable diameter prop with high pitch that a similar powered ICE would stall in trying to rotate. This rotation can be very controlled to hardly turning or full revs to reverse in very short tiimes that make docking with electric motors much more controlled. See an example power curve for a 5KW BLDC MOTOR http://goldenmotor.com/hubmotors/48V5KW-09052602-3800RPM%20Performance%20Curve.jpg where you will notice subtle curve in the power output but nowhere nere the mountain shape of an ICE curve.

[kerosene]

of course - you are totally right - if you have a ICE rated for lets say 100hp/4500 rpm and you put it in application where you are going to run it at 800rpm you will not be very pleasantly surprised. The question is who would do that? It would be idiotic.

However using constant rated diesel engine of lets say 10hp will perform very well in an application where 5-10 hp is needed. And you cannot replace it with 3hp electric engine and expect same performance.

Electric motors tend to have much flatter power and torque curves giving them the ability to turn a reasonable diameter prop with high pitch that a similar powered ICE would stall in trying to rotate.

If the ICE stalls then the gearing is totally wrong. Show me a prop and tell me how fast it needs to spin and show me an electric engine that can do that and I will show you a diesel that can be geared to do exact same task - assuming rated powers are in line.

Also I hope you are aware that running e-motors at high torque at very low rpm is very inefficient and mostly creating heat.

http://www.redshift.com/~gordis/motorcycle/Dyno3curves.jpg
Here is a power curve of a 1000cc v-twin sports bike. The flatter curve is torque and power curve is the one that keeps climbing. As its pretty high performance engine it needs relatively high RPM to be "in the range" - however note that despite being a 100hp/liter sports touring engine it has very flat torque curve any speed above 3500 rpm to the redline.

Show me an electric engine busting out 100hp on shaft and I will gear this engine to do the same exact task.

[kerosene]

Power curves for Internal Combustion Engines are not fully linearly related to the torque curves


That statement is blatantly wrong. They are exactly related - on any chart that you can see a torque and rpm you can plot the power.

You CANNOT have two charts with same torque values but different power values. Unless you cheat of course. You fail to acknowledge that in its simplicity:

torque * RPM * 1/5250 = hp

or the other way round

hp = (torque * RPM) / 5250

(this is with lbft for torque - with Nm the multiplier is different)

[COOL Mobility]

Theory is fine but reality of power to a prop is different especially for slow reving diesels that we are talking about comparing to electric options, not gas powered sports engines.

Marine diesels have a very narrow power band and are pretty gutless below 1500rpm.

In yachts most users are replacing their old stink pots with 5KW to 20KW motors with considerable success. Easier docking under very fine control and plenty of power up to hull speed. For planing an ICE will always be better, but that was not the theme of this string.

[latestarter]

i have seen on many articles from electric motors, that for example an electric motor of 10 kW can easely replace an diesel up to 40 kW.


Were these car related articles?
In which case there is an element of truth.
I got interested in converting a car to electric drive a couple of years ago.
One of the recommended books on the subject is "Build Your Own Electric Vehicle" by Seth Leitman and Bob Brant.

In table 4-2 they list options for conversion based on cost

OK: Van with 19 hp
Ideal: Pickup truck with 22 hp
Best: Car with 30 hp
Unlimited money: Custom built Starship Electrocruiser with 50 hp

The factors that make these vehicles practical compared to the power of the IC engines they replace appear to be:-

1. the existing vehicles are over powered for the way they are used.

2. Running an electric motor at its rated power is pleasant, an IC engine at max revs is not accepted in a car.

3. Batteries are the limiting factor so drivers are willing to forgo performance in favor of increased range.

4. the torque at low revs is so high that you can keep up with or go ahead of city traffic.
I was at a seminar on battery vehicles last year, one guy had a small pickup that he could spin his wheels in
third gear.

5. for short periods you can get much more than the rated horse power from the electric motor.

This does not transfer to boats.

Displacement boats are not generally overpowered. Running the engine at the upper end of its rev range is more accepted. Boats usually run at a constant speed so having the option of a short burst of extra power is of little value.

Having researched electric car conversion I decided against it due to living in a hilly area and would not use it enough.

[Mr. Know-It-All]

You still need the stink pot to generate power to your electric engine. So what is the gain?

If you do the thought experiment below, maybe you could stop posting messages about torque being nonlinear.


Imagine that the engine in the example above (http://www.boatdesign.net/forums/attachments/hybrid/47140d1283498595-electic-kw-diesel-kw-new-1.jpg) has a crankshaft having a crank of 1 meter. At 2000 RMP the engine can produce up to 300 Nm. In SI units, power is measured in Nm/s, which is called Watt. So how many Nm/s can we produce? Well, if we crank on the crankshaft, we travel in a circle having a radius of 1 meter. How far is that? It is pi * 2 * 1 meter. How many meters do we travel per second? 2000 RPM is 2000/60 RPS = 33.333333 RPS. So now we crank on the crankshaft (using 300 Newton force). We travel 33.33333 * pi * 2 = 209 meters every second. So the power would be 209 * 300 = 62 700 Nm / s = 62 kW.

Now this power is available to the gearbox. Assume we have 10 % loss in the transmission. 56 kW is available to turn the propeller shaft. If you do the thought experiment backwards, you can calculate the torque the gearbox can apply to the propeller at a certain RPM of the propeller shaft. High power allows for high torque at the propeller.

In reality, gearboxes have limited gear ratios, for boats usually one. This complicates matters. Torque is still torque
and power is still power. It always will be.



Theory is fine but reality of power to a prop is different especially for slow reving diesels that we are talking about comparing to electric options, not gas powered sports engines.

Marine diesels have a very narrow power band and are pretty gutless below 1500rpm.

In yachts most users are replacing their old stink pots with 5KW to 20KW motors with considerable success. Easier docking under very fine control and plenty of power up to hull speed. For planing an ICE will always be better, but that was not the theme of this string.

[apex1]

Theory is fine but reality of power to a prop is different especially for slow reving diesels that we are talking about comparing to electric options, not gas powered sports engines.

Marine diesels have a very narrow power band and are pretty gutless below 1500rpm.

In yachts most users are replacing their old stink pots with 5KW to 20KW motors with considerable success. Easier docking under very fine control and plenty of power up to hull speed. For planing an ICE will always be better, but that was not the theme of this string.

Not to bother you, but that statement is wrong again. You are too broad in your way of looking at the topic. A medium speed marine Diesel for example has a max rpm of around 500 - 800rpm. and starts living at 120rpm.

Of course in a sailboat we don´t find them. But even the average sailboat engine has a relatively wide power band (more important a wide torque band), in comparison with the same engines setup for car use.

The El motor does not, and cannot replace a IC engine if not able to crank out the same power! The ONLY advantage of the El. motor is the fact, that it provides relatively high torque at low rpm, therefore allows for better maneuvering at slow speeds. Thats it

The obvious disadvantage is the fact that you have to carry several times the weight of a IC engine setup (incl. tanks) when going El. to the same properties. There is no way around it and there will be no way around for the next 15 -25 years, no matter how nice one cheats the comparison.

By so far there is not one single boat on earth propelled electric to the same weight, performance, endurance and speed as a IC propelled sibling.

The actual state of the art el. energy storage is still lightyears away from a diesel tank and there is not one, not a single one, system in discussion at present which would be able to change the situation substantially. We know that there are about 15 or more years between studying/discussing a new technology and mass production, right? Then there are another 5 - 10, sometimes 50 years from mass production to marine application.

So, where is your El. propulsion?

In dreams and cheating comparisons, thats all.

Regards
Richard

[Alik]

Not to bother you, but that statement is wrong again.

...

In dreams and cheating comparisons, thats all.


Fully agreed.

'Advantage' of using more torque at lower RPM requires huge diamter of propellers that are not likely to fit in any real boat, with limited draft. If we are talking about speeds of 3-4kts on 40' boat it is true and it works (but such speed is hardly acceptable outside of marina). Once we need higher speed the required propeller diameter will be over 1m :)

There is a lot of advertised fiction and brainwash about electrical propulsion. I used to say to my customers clearly: we do not design electrical propulsion on offshore boats. On lakes - yes, we do :)

[CatBuilder]

I haven't finished reading this thread yet, but I'm providing input on the question of a "diesel battery" vs deep cycle vs starting battery.

I have experience with all three, and all three do exist.

1) What people are calling a "diesel" battery is a battery that is somewhere between a starting battery and a deep cycle battery. The "diesel battery" is a starting battery with thicker plates, though not so thick as a true deep cycle battery. These "diesel batteries" can be discharged to 50% just like a house battery, but have less service life. They also start engines. I would know. My Sprinter came with one as standard equipment and it's still working well. The previous owner of my Sprinter had an inverter hooked to the thing.

2) House batteries can start diesel engines, if you have a good bank. I have a set of 4 Trojan T-105's I am using as a combination house and starting bank. Mostly, they are used as house, but they start a Mercedes Diesel Straight 5 engine without any trouble, even when they are at 50% discharge. (I've never taken them below 50%, so I can't comment as the charge is reduced)

[COOL Mobility]

The obvious disadvantage is the fact that you have to carry several times the weight of a IC engine setup (incl. tanks) when going El. to the same properties. There is no way around it and there will be no way around for the next 15 -25 years, no matter how nice one cheats the comparison.

By so far there is not one single boat on earth propelled electric to the same weight, performance, endurance and speed as a IC propelled sibling.

The actual state of the art el. energy storage is still lightyears away from a diesel tank and there is not one, not a single one, system in discussion at present which would be able to change the situation substantially. We know that there are about 15 or more years between studying/discussing a new technology and mass production, right? Then there are another 5 - 10, sometimes 50 years from mass production to marine application.

So, where is your El. propulsion?

In dreams and cheating comparisons, thats all.

Regards
Richard

No real Electric propulsion yet or for over a decade! It's here already.

You obviously have not heard of the "Planet Solar" Project where an electric cat has been built to sail non-stop around the World - Any diesel boats of comparable size able to do that???

PlanetSolar is a multlihull vessel topped by a large array of photovoltaic solar panels, constructed by Knierim Yacht Club, in Kiel, Germany. Built in 14 months, the biggest solar boat ever built has impressive dimensions and is yet both silent and clean. Also uses Li Ion batteries. The goal is to navigate around the world at an average speed of 7.5 knots — no mean feat for a solar-powered craft.
http://www.planetsolar.org/images/news/news-20100512.jpg

See project at http://www.planetsolar.org/bateau.en.php and actual photos and videos at http://www.planetsolar.org/multimedia-photos.en.php
Note the five bladed props/"wheels" at rear of each pontoon with a huge diameter and surface penetration (only half submerged) for efficiency.

[Mr. Know-It-All]

I think no one on this forum can afford that boat.

No real Electric propulsion yet or for over a decade! It's here already.

You obviously have not heard of the "Planet Solar" Project where an electric cat has been built to sail non-stop around the World - Any diesel boats of comparable size able to do that???

PlanetSolar is a multlihull vessel topped by a large array of photovoltaic solar panels, constructed by Knierim Yacht Club, in Kiel, Germany. Built in 14 months, the biggest solar boat ever built has impressive dimensions and is yet both silent and clean. Also uses Li Ion batteries. The goal is to navigate around the world at an average speed of 7.5 knots — no mean feat for a solar-powered craft.
http://www.planetsolar.org/images/news/news-20100512.jpg

See project at http://www.planetsolar.org/bateau.en.php and actual photos and videos at http://www.planetsolar.org/multimedia-photos.en.php
Note the five bladed props/"wheels" at rear of each pontoon with a huge diameter and surface penetration (only half submerged) for efficiency.

[apex1]

I haven't finished reading this thread yet, but I'm providing input on the question of a "diesel battery" vs deep cycle vs starting battery.

I have experience with all three, and all three do exist.

1) What people are calling a "diesel" battery is a battery that is somewhere between a starting battery and a deep cycle battery. The "diesel battery" is a starting battery with thicker plates, though not so thick as a true deep cycle battery. These "diesel batteries" can be discharged to 50% just like a house battery, but have less service life. They also start engines. I would know. My Sprinter came with one as standard equipment and it's still working well. The previous owner of my Sprinter had an inverter hooked to the thing.

2) House batteries can start diesel engines, if you have a good bank. I have a set of 4 Trojan T-105's I am using as a combination house and starting bank. Mostly, they are used as house, but they start a Mercedes Diesel Straight 5 engine without any trouble, even when they are at 50% discharge. (I've never taken them below 50%, so I can't comment as the charge is reduced)

True there are different "tastes" of starter batteries.

But as it is in all businesses we have a clear terminology in marine applications.

Starter batteries are not tagged as deep cycle, because they are not.

Of course a deep cycle house bank can crank a starter when sized appropriate, but that is not what they are designed for and it does not make sense to use them that way.

And then, we are a bit off topic discussing battery properties here.

Regards
Richard

[COOL Mobility]

Further info on Planet solar boat and its

http://plugboat.com/2010/03/04/planet-solar-yacht-plans-to-circle-the-globe/ The props are clearly seen here.
http://plugboat.com/wp-content/uploads/2010/03/planet-solar-electric-yatcht-props-600x402.jpg

Also Scientific Amerian website http://www.scientificamerican.com/article.cfm?id=worlds-mightiest-solar-boat

"On board, the world's largest lithium-ion battery, a 13-tonne monster capable of storing 1,300 kilowatt-hours of energy when fully charged, will allow the boat to slice through the water at an average speed of 13 kilometers per hour for three days straight in complete darkness before its charge is completely exhausted."

"The ship is designed, however, to operate at sea indefinitely, and under normal conditions its 38,000 solar cells average enough power production to muster the 20 kilowatts of power needed to keep the boat cruising along at its average speed. The maximum electrical output of all the cells together on a sunny day is about 100 kilowatts."

* Length: 31 m
* Width: 15 m
* Length with flaps: 35 m
* Width with flaps: 23 m
* Height: 6.1 m
* Weight: 85 t
* Surface of solar modules: 536 m2
* PV panel efficiency: 18.8 %
* PV installed power: 93.5 kW (127.0 HP)
* Average engine consumption: 20 kW (26.8 HP)
* Average speed: 7.5 kt (14 km/h)
* Maximum speed: 14 kt (25 km/h)
* Crew: 3 - 4 skippers
* People that can go onboard: 40
* Autonomy: Never-ending solar navigation


To me 20 KW of electric power to propel a 100' cat weiging 85 tons at over 7.5 knots continuosly up to max of 14knots indicates more efficiency than possible from Internal Combustion engines - could two 10KW (13.5HP) ICEs move this boat at any speed, let alone at cruising speed? I don't think so...

I rest my case with you narrow minded, fuel sniffing, ICE biggots. Open your minds and consider the potential instead of being so closed minded.

[apex1]

"The ship is designed, however, to operate at sea indefinitely, and under normal conditions its 38,000 solar cells average enough power production to muster the 20 kilowatts of power needed to keep the boat cruising along at its average speed. The maximum electrical output of all the cells together on a sunny day is about 100 kilowatts."



To me 20 KW of electric power to propel a 100' cat weiging 85 tons at over 7.5 knots continuosly up to max of 14knots indicates more efficiency than possible from Internal Combustion engines - could two 10KW (13.5HP) ICEs move this boat at any speed, let alone at cruising speed? I don't think so...

I rest my case with you narrow minded, fuel sniffing, ICE biggots. Open your minds and consider the potential instead of being so closed minded.

How do you calculate 127hp equal to 20KW ??? The 20KW do NOT propel the vessel to top speed!

What do you guess, how long is 13 tonnes of fuel driving a 127hp Diesel?

No, sorry mate,

you are biased and misinformed. You compare apples and oranges (as ALL your collegues), and then you call us closed minded.
You are the closed minded, trying to cheat yourself with mad comparisons.
Grow up and see the reality!

What dou you think? We are doing our jobs in blissfull isolation?
If NA´s and boatbuilders are not at least well informed about new technologies, they are out of business in short time.


To make it short:

Hybrid systems with equal properties to well designed diesel propulsion, do not exist in the marine market. period

[Alik]

To me 20 KW of electric power to propel a 100' cat weiging 85 tons at over 7.5 knots continuosly up to max of 14knots indicates more efficiency than possible from Internal Combustion engines - could two 10KW (13.5HP) ICEs move this boat at any speed, let alone at cruising speed? I don't think so...

I rest my case with you narrow minded, fuel sniffing, ICE biggots. Open your minds and consider the potential instead of being so closed minded.

Given same power, both ICE and electrical motor will move same boat at same speed. Period. This is just physics, this is evident.

Open Your mind not only to advertisement booklets, but to serious reading on propulsion and propeller design.

[Mr. Know-It-All]

That battery (1300 kWh) is equivalent to 26 gallons of diesel. Many boats have more fuel than that. Even if you can use only 33 % of the energy (and 100% energy from the battery), the 13-tonne monster is only equivalent to 75 gallons of fuel.



Further info on Planet solar boat and its

http://plugboat.com/2010/03/04/planet-solar-yacht-plans-to-circle-the-globe/ The props are clearly seen here.
http://plugboat.com/wp-content/uploads/2010/03/planet-solar-electric-yatcht-props-600x402.jpg

Also Scientific Amerian website http://www.scientificamerican.com/article.cfm?id=worlds-mightiest-solar-boat

"On board, the world's largest lithium-ion battery, a 13-tonne monster capable of storing 1,300 kilowatt-hours of energy when fully charged, will allow the boat to slice through the water at an average speed of 13 kilometers per hour for three days straight in complete darkness before its charge is completely exhausted."

"The ship is designed, however, to operate at sea indefinitely, and under normal conditions its 38,000 solar cells average enough power production to muster the 20 kilowatts of power needed to keep the boat cruising along at its average speed. The maximum electrical output of all the cells together on a sunny day is about 100 kilowatts."

* Length: 31 m
* Width: 15 m
* Length with flaps: 35 m
* Width with flaps: 23 m
* Height: 6.1 m
* Weight: 85 t
* Surface of solar modules: 536 m2
* PV panel efficiency: 18.8 %
* PV installed power: 93.5 kW (127.0 HP)
* Average engine consumption: 20 kW (26.8 HP)
* Average speed: 7.5 kt (14 km/h)
* Maximum speed: 14 kt (25 km/h)
* Crew: 3 - 4 skippers
* People that can go onboard: 40
* Autonomy: Never-ending solar navigation


To me 20 KW of electric power to propel a 100' cat weiging 85 tons at over 7.5 knots continuosly up to max of 14knots indicates more efficiency than possible from Internal Combustion engines - could two 10KW (13.5HP) ICEs move this boat at any speed, let alone at cruising speed? I don't think so...

I rest my case with you narrow minded, fuel sniffing, ICE biggots. Open your minds and consider the potential instead of being so closed minded.

[CatBuilder]

Apex1: Reading the Scientific American article, there are some interesting local points about the solar powered boat for you.

"unveiled for the first time in a ceremony at a shipyard in Kiel, Germany" - a shipyard you know, perhaps?

"PlanetSolar will be tested in the water for the first time later this month, and by early 2011 its captains hope to be on their way, with stops including Hamburg, " - you can go see this boat!

[apex1]

Apex1: Reading the Scientific American article, there are some interesting local points about the solar powered boat for you.

"unveiled for the first time in a ceremony at a shipyard in Kiel, Germany" - a shipyard you know, perhaps?

"PlanetSolar will be tested in the water for the first time later this month, and by early 2011 its captains hope to be on their way, with stops including Hamburg, " - you can go see this boat!

Thank you Mate,

yes I know the yard (Knierim), and have read some of the hype.

It does not change the plain facts.
There is no hybrid propulsion for ships and boats and yachts. period

A vessel built with massive subsidies, operated in restricted use and areas, with a idiotic low payload and as idiotic shape, does not change any fact.
It is just proof that you can promote every premature concept successfully.

And just for the records:
she failed already on her first voyage, and had to "refuel" in Leixoes after crossing the Bay of Biscay in cloudy weather!!!
Mature concepts look different.

Regards
Richard

[kerosene]

I am not so pessimistic as you richard. Concept and early prototypes are not proof of technology being mature for sensible us but they are important in developing interest and in taking the 1st steps in new tech.

Of cours stuff like ocean crossing solar boat is impractical and provides really no real practical solution. Sails would becheaper and allow for mor seaworthy vessel.

There are situations where electric powertrain already works fine. If you need regularily limited amount of capacity like shrtish commute a small e-vehicle already makes sense. A sailboat used one a week can get away with e-motor for getting in and out of harbor. For motor sailing or any application where there is/might be need for hours of operating it makes no sense.

Key issues for e-power to make sense
- regular use needed to cover investment to batteries
- said use limited to <10 kWh per day and consistently about the same energy need per day
- no quick charge needed

- no need for exceptions like one day need to ride triple the distance. Carrying spare capacity like this is not feasible.

[apex1]

I am not so pessimistic as you richard.

I am not pessimistic, I am realistic.

The entire Hybrid hype is just plain nonsense on yachts.

I made my commercial tickets mainly on a Icebreaker in the Baltic. We had Diesel electric propulsion for a simple reason: always low operational speed, and always high torque demand. We could have operated three, much bigger freighters full speed with our fuel consumption.

Everytime when the D/E topic came on the table in the past 35 years, some people immediately called that a clever solution for their boats!

I guess half of these idiots still believe what they will belive. I gave up on them.

Same is valid here.
There was a simple statement by Alik, few posts ago. Do you assume that our believers here buy that? No, it does not fit in their well established preconception.

Of course we need new ideas and concepts, no doubt. And we see that some of them work well to some extend. Hybrid cars for example. Far from being perfect and not very efficient by now, but a step towards the right end. That took 20 years from concept to market acceptance.

But these systems cannot work on boats as we all know.

So, when such concept hardly works in a car (the battery capacity is still extremely far from good even there), which is just about 15 to 20% as power demanding as a boat. Which has the big advantage of intermittend power demand. Which has the very big advantage of recovering brake energy.
When we count all that, and then look at the upcoming battery developments (there are none really promising at present), we must come to the conclusion, it is not worth talking for the next several years. I guess we will not see any competitive hybrid propulsion in the next 20 - 25 years.

The solar junk is a expensive and worthless gag, and failed at the first attempt. Not worth to waste any further comment on that.

Thats it.
Richard

[COOL Mobility]

How do you calculate 127hp equal to 20KW ??? The 20KW do NOT propel the vessel to top speed!

If you read it properly, there is 127hp of solar collector cells, but the motors only generally output 20KW of power
* PV installed power: 93.5 kW (127.0 HP)
* Average engine consumption: 20 kW (26.8 HP)

[apex1]

If you read it properly, there is 127hp of solar collector cells, but the motors only generally output 20KW of power
* PV installed power: 93.5 kW (127.0 HP)
* Average engine consumption: 20 kW (26.8 HP)

You are right I have missed the "PV" and only noticed the "installed power"

Nevertheless the "average consumption" is a cheating point again. These 20kW do not provide the proudly advertised top speed.

But that is valid for the entire article. PR drivel. We have seen how much the "indefinite range" was worth.

And after all, she is useless and she failed.

[mydauphin]

Anyone that studies solar panel discover many flaws very quickly.
Heres is the top 5.
1. They angle to sun greatly effects power generate, and I mean greatly. So no matter what you do you never get 100% and only have full power 4 hours a day.
2. The panels get hot and power drops quickly.
3. The panels with higher densities are higher voltage panels and require expensive charge converters
4. By the time you ad solar panels, batteries, wiring and charges, inverters, electric engines their weight is much great than an equivalent diesel, fuel tank, transmission etc.
5. Marine environment, specially pounding is especially hard on all thee electronics especially panels.

[mydauphin]

This from a guy that has 4 solar panels, two 180 watt and two 30 watt. I used for house power and emergency power.

[CDK]

And from the guy that has 10 panels and sold several 1000's:

Bird ****, a fallen leave or the shadow of a rope dramatically reduces performance. Cover one cell from a 36 cell panel and the output is almost nothing.

I mainly agree with Mydauphin's evaluation except #5.
Well constructed panels are quite at home in a marine environment. Many beacons at sea are equipped with solar panels, surviving extreme weather conditions when even large ships seek shelter.

[COOL Mobility]

PV panels are fine in Australia where we get so much sunshine, but even here wind gens with ~300W output are the general companion as wind (real or apparent) are what rives both the yacht and gen/alternator.

Belt and braces and you don't need to rely on shore power.

300W of Wind gen is cheaper than 300W of PV but not silent!

[apex1]

300W of Wind gen is cheaper than 300W of PV but not silent!

True, very true.

But not very handsome. The wind gen is not the big winner while under sail. (physics)
And he is the looser when not.

Where do you drop anchor? In the windy corner of the bay? Ahh, you see?

When you sit in port on a stormy day the wind gen might look as a winner, assumed there is no shore power, he is.
But thats not sailors paradise.

On the barefoot route I have seen a guy with a fire axe, getting rid of his landscape ventilator at 2.00 at night.

Ask the circumnavigators about wind gen, and PV panels, you get enlightening replies!

There are many things in our maritime world which seem to be a good idea. Few stand the test of time though.

I agree with CDK, it is hard to kill a PV panel when proper installed, but unfortunately it is as hard to draw some juice from it.

Regards
Richard

[mydauphin]

I mainly agree with Mydauphin's evaluation except #5.
Well constructed panels are quite at home in a marine environment. Many beacons at sea are equipped with solar panels, surviving extreme weather conditions when even large ships seek shelter.

It is not the panel that fails but the mounting. The swinging and pounding of boat will either crack the fiberglass it is attached to, or bend the panel and crack it. Sure it can be mounted better but most people are trying to save weight or mount it out of the way. Just imagine the structure to hold 10 or 15 panels.

Also lost several chargers to Marina power surges caused from crappy marina wiring. That is why I went 100% for charging batteries. Solar charges like outback Flexmate 80 solar charge controller are expensive but needed to maximize power output. CDK you know something cheaper? My panels make 48 volts, they are the BP180.

[CDK]

Mydauphin, we are talking about different animals here.
The panel I sold and still use are Siemens, aluminum frame, Corning tempered glass. Laid up on both ends a man can stand in the middle and jump: no damage. Mounting is done with a rubber grommet and a stainless bolt.

The panels you have must have come cheap, you do not need 48 volts.
I would not buy anything but make a switch mode down converter. Most of the parts you need are in any computer supply and these cost almost nothing nowadays. If you don't want to make anything, buy 3 small PC supplies, wire both the panels in series for 96 volts and the 5 volts outputs to get 14V to charge your batteries (adjust the +5V just a little bit).

Is that cheap or isn't it?

[mydauphin]

Mydauphin, we are talking about different animals here.
The panel I sold and still use are Siemens, aluminum frame, Corning tempered glass. Laid up on both ends a man can stand in the middle and jump: no damage. Mounting is done with a rubber grommet and a stainless bolt.

The panels you have must have come cheap, you do not need 48 volts.
I would not buy anything but make a switch mode down converter. Most of the parts you need are in any computer supply and these cost almost nothing nowadays. If you don't want to make anything, buy 3 small PC supplies, wire both the panels in series for 96 volts and the 5 volts outputs to get 14V to charge your batteries (adjust the +5V just a little bit).

Is that cheap or isn't it?

Interesting Idea. But what 3 step charging...

[mydauphin]

I also don't understand PC power supply idea. It is very intriguing especially since I have a bunch of them. The panels produce 48 Vdc, I put in series and they put out 96 vdc. So far so good. But Pc power supply is expecting 110 vac, therefore it has transformer, wont work with Dc, to reduce voltage, then diodes or something like it to convert to DC. I am sure you know what you are talking about but I don't see anything here to reduce 96vdc to 14vdc. My solar Bp 180 Watt solar panels were State of the Art 5 years ago, did get them for free when a hurricane blow them off a top of a building unto my house.

[CDK]

The PC power supply is a switch mode device. It has no primary transformer and accepts both AC and DC. It also compensates for the lower input voltage of the PV panels.

[mydauphin]

The PC power supply is a switch mode device. It has no primary transformer and accepts both AC and DC. It also compensates for the lower input voltage of the PV panels.

Really!!!. Ok so I rig 2 PS in parallel feed then 96 volts and it is going to convert them to 12vdc and 5vdc. I know i got something wrong

[kerosene]

yeah if that's correct its pretty sweet - esp. if efficiencies are not terrible

[CDK]

Really!!!. Ok so I rig 2 PS in parallel feed then 96 volts and it is going to convert them to 12vdc and 5vdc. I know i got something wrong

These supplies make 5vdc, precisely stabilized, very efficient and able to handle heavy loads. The other voltages are byproducts with much lower currents.

A minimum load must be present to start the circuit, so if you do the experiment and there is no output voltage you might think I fooled you.
A small light bulb (12v, 10 or 15 watts) is enough. When used as a battery charger you do not need it of course.

There is a small trimming pot on the circuit board to adjust the 5vdc output. If you can turn that up to 7 volts you need only two power supplies to charge 12V batteries.