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Discussion Starter · #1 ·
Hi,

Im in the infantile stages of building a hybrid boat, im currently looking to start with a 50hp outboard (no powerhead) and im considering what electric motor to run, so far the Toyota Prius is looking good (cheap and available)
What I'd like to know, is forgetting a battery bank, what hp or kVa would i need for a hybrid setup (diesel generator) going 3 phase (415v) and what inverters would be required?
For what its worth can a variable speed generator (inverter gen) be used?
All of these heat generators will be liquid cooled somewhat, to assist with efficiency (raw water via a heat exchanger)

Thank you
Regards Dan
 

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Hi,

Im in the infantile stages of building a hybrid boat, im currently looking to start with a 50hp outboard (no powerhead) and im considering what electric motor to run, so far the Toyota Prius is looking good (cheap and available)
What I'd like to know, is forgetting a battery bank, what hp or kVa would i need for a hybrid setup (diesel generator) going 3 phase (415v) and what inverters would be required?
For what its worth can a variable speed generator (inverter gen) be used?
All of these heat generators will be liquid cooled somewhat, to assist with efficiency (raw water via a heat exchanger)

Thank you
Regards Dan
Hi Dan
You are aware that the gods of engineering take a cut every time you convert energy

Engine power
Direct drive to prop - 90%
Total 90%

Engine power
Generator to electricity - 85%
Motor electricity to power - 85%
Direct drive to prop - 90%
Total - 65%

Hybrid cars usually use the engine to drive the car - with the motor only used part of the time
AND they can take advantage of regen braking
 

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You are aware that the gods of engineering take a cut every time you convert energy...
True!

Hybrid cars usually use the engine to drive the car - with the motor only used part of the time
AND they can take advantage of regen braking
Meaning that most automotive hybrids are a parallel configuration... yes, that's at least partially true. Most brands of hybrid use a parallel design. The most successful manufacturer of hybrids (Toyota) uses a power-split design (also used in many other hybrids), in which some power is transmitted from engine to wheels entirely mechanically, and some goes through a generator and motor. Very few use a series configuration (most notably the BMW i3, which has poor efficiency), and some of those that run in series normally engage a parallel mechanical power in a limited (highway) speed range (Mitsubishi Outlander PHEV and Honda Accord Hybrid).
 

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Discussion Starter · #4 ·
Thank you for your replies,
Im trying to see the advantages of EV over ICE in high load long distance use in a boat, i guess the biggest advantage to date in a diesel electric setup would be a 50kw brushless dc motor would have more torque throughout the rpm range than a 80-100kw ICE on avg torque (not peak) therefore a smaller dc motor & load would do the same approximate job.
I guess Trains have been doing the diesel electric thing well, in reality it reduces the nead of a ratio adjustable gearset on trains. Hopefully the torque will mean 20kw will do what 35kw ICE can in a outboard motor. (Obviously propping will play a huge part in this)
 

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I guess Trains have been doing the diesel electric thing well, in reality it reduces the nead of a ratio adjustable gearset on trains.
Trains and ships, but for very different reasons.
Trains (and some heavy off-highway trucks) use an electric transmission (generator plus motors) to provide a continuously variable range of drive ratios, but most importantly to provide an infinitely high reduction ratio. This is of no value when driving a propeller in water.
Ships use an electric transmission system (one generator per engine, plus one motor per propeller) to avoid very large gear transmissions, and to provide flexibility of running the number of engines needed by the load of the moment, often driving more than one propeller. None of this is of value with a small engine in a single-prop boat.

Hopefully the torque will mean 20kw will do what 35kw ICE can in a outboard motor. (Obviously propping will play a huge part in this)
I don't see the point of a comparison of peak power ratings of an electric motor and an internal combustion engine. The "20" label on the motor is not an advantage just because the engine has a "35" label on it. In each case, appropriate sizing is required. Rational comparison of the two methods of propulsion must consider the weight, size, cost, and performance of the entire system, from battery to prop or from fuel tank to prop.
 

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Hi,

Im in the infantile stages of building a hybrid boat, im currently looking to start with a 50hp outboard (no powerhead) and im considering what electric motor to run, so far the Toyota Prius is looking good (cheap and available)
What I'd like to know, is forgetting a battery bank, what hp or kVa would i need for a hybrid setup (diesel generator) going 3 phase (415v) and what inverters would be required?
For what its worth can a variable speed generator (inverter gen) be used?
All of these heat generators will be liquid cooled somewhat, to assist with efficiency (raw water via a heat exchanger)

Thank you
Regards Dan
Hello Dan I'm Edward -My background before I give you my input: I'm a Merchant Marine ET: Electronics/Power Plant Technologist: Work as a Service Engineer for Both G,E and Siemens in the "Intergraded Drive Technologies" Variable Speed Drives. My education is in both Electronics, Automation, Software and Electrical Engineering; I currently work in a 40MW plant

Now your project:: You have quite a bit of reading to do to come up to speed on the basics of Marine Propulsion; because that's basically what your project is even thought your Power Plant is small. You want to convert a 50HP outboard for a pleasure Boat is my guess; after reading your blog I have to make some assumptions. In any Engineering project I would need to know the size of the boat total weight capacity, the purpose of the boat, what speed is 90% of operation for calculating the Power Plant size.## Most Marine Power plants are series Intergraded Drive Technologies meaning Diesel Electric to Generator to Distribution System (Switch Board) to Propulsion Motor
###In Electric Vehicles the technologies such as Toyota the car manufacture uses a "Power Split Hybrid" Series Parallel Hybrid where power is split between Mechanical and Electrical the the main principle is to decouple the power; The Internal Combustion Engine or Electric Motor supplies power to the drive shaft dependent on the demand from the Vehicle operator.
Current battery technology for vehicles places the two general selections on either Lithium or Nickel Cadmium manufactures use Lithium; backyard mechanics use Nickel Cadmium in either case the Battery density is quite low.
Calculating 50HP to KVA assuming 100% efficiency Motor and a Power Factor of 80% a KVA 46.625. The KVA is the approximate amount of power for a 50HP motor weighting around 600LBS plus the controller, plus the battery for control power not propulsion power; plus the Engine; plus the Mechanical transmission/decouple
This is my input and Good Luck
Ed
 
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