electric powered drive boat

[systemsEngineer]

We like to get more information on system that will work in side a small boat -150 Hp
The system will have [2] electric motors direct connected to the propeller's of the boat The power to operate the motor's will come from a generator on board
All the systems need to be safe and waterproof

 

[harrisj]

Interesting project - of course diesel-electric and turbo-electric is common on bigger ships but I guess you're looking at 20 - 30 foot range here.

You could start by looking at some excellent threads in automotive such as 'Hybrid strategy' in 'Engine & Fuel' for new motor technologies.

However, driving a propeller has different characteristics to automotive applications - no low speed high torque requirement, but no light load / high speed cruising either. May need shunt wound rather than series wound motors. You could look for info on mini-submarines and ROV submersibles for motor ideas in this power range.

You're right in considering safety very seriously. The quest for efficiency drives you to higher voltages but I wouldn't go above 50 volts in a small boat - they always get wet where you least expect. And apart from fire / electrocution, unexpected loss of power in a boat can be catastrophic. For the same reasons, diesels are much safer than petrol/gasoline engines in boats.

Finally, there's usually a lot of electronic gizmos even on a small boat. Beware of EMC problems if you're controlling high currents with switch mode techniques.

John

 

[ccfowler]

In this size/power range, it is hard to imagine how an electric drive can be preferable (economically or physically) to the commonly available (and well developed) mechanical drives. Weight issues alone would seem to be excessive without even considering the matters of cost and efficiency.

Are there some compelling configuration considerations?

 

[harrisj]

Well yes there may be ......

A conventional pleasure boat layout puts engines where you don't want them, and ends up with a prop shaft angled downward to avoid having UJs in the drive line. This reduces prop efficiency. Also, the propshafts are difficult to integrate into hull shapes, and intrude on accommodation space. They don't like flexible structures (such as fibreglass hulls).

An outdrive (Z-drive) overcomes this but drives through bevel gears which are not efficient.

Most boats have 2 engines, 2 transmissions and 2 props. This is good for redundancy but diesels are reliable and you don't need to duplicate here. One engine and 2 props is a useful system but difficult to configure mechanically. Apart from the redundancy issue, electric drive could do this easily, and provide infinite control over both props.

Ther are a lot of other high power devices on boats (bow thrusters, winches) which rely on generator / battery systems. Many boats also have an aux genset. You wouldn't need all this generator capacity if your single engine was just driving a big generator.

All in all, electric drive is an elegant solution. However, cost and safety are issues on small boats, so I think you're rignt in expecting to see mechanical transmissions for a while yet. Don't think weight's too much of a problem.

Systemsengineer - tell us more about the boat.

Regards - John

 

[Cyclefrog]

Under about 200' the cost of the electrical control circuitry for a diesel-electric drive kills you. As an estimator and project manager in a company building yachts in the 55 - 150 ft. range, I've found that so far there is nothing out there that is as cost-effective as a conventional mechanical drive.

Having said that, some other things we do that provide some of the features Systemsengineer may be seeking:

1. With a clutched hydraulic pump on the front of the genset(s) we have hydraulics to drive the shaft at reduced speed via a Charlynn 6000 or 10000 motor and a hefty roller chain in the event the main engine poops.

2. Hydraulic bow and stern thrusters give better low speed maneuvering capability than twin screws. In our vessels the propeller and rudder are protected by the keel and skeg, which isn't as practical to accomplish with twin screws. Also the single engine sits lower in the hull than twins would, giving better stability.

3. A good naval artichoke should be able to design a vessel arrangement that locates the engine in the belly of the boat and still maximizes the usable living and/or cargo space. Check out Lynn Senour's work for some really efficient space utilization.

 

[MotoGuzzi]

Why not try a diesel hydraulic drive. Have your prime mover drive a hydraulic pump on one end and an alternator on the other for ship's power.

 

[acadien]

So 150Hp = 112 Kw, you need a generator this size plus hotel load. I toiled with this idea to place in my "imaginary" boat (I dream a lot)... I would have used 2 X 600VAC motors with 2 AC drives, in your case 2 X 75HP motors at 600VAC that's 75Amps (check the tables.. just a rule of thums 1hp at 600VAC = 1Amp) and 2 X 75Amps drives (these babies are pretty expensive) Plus control system (PLC, HMI buttons, Control Panel, joystick etc...) a nice Flat touchscreen panel besides the Capt'n chair would look pretty neat.

What I liked is that you have more options for the placement of the generator. Since you have a control system you can access all sorts of data, you can have a "steer by wire system", you can build an auto-pilot, tie-in all engine data and control, lights... instead of having a dash board full of guages, knobs and what not, you can have your own IMCS (integrated machinery control system) you can control water, pumps, heat whatever... as you can see I LOVE CONTROL.

For larger ships you can go to medium voltage systems 2KV+ I only looked up ABB, they manufacture MV drives but no less than 3000KW (4023HP)perhaps other companies manufacture MV drives in the range of 150KW.

 

[arto]

Elco has some really nice ones, but only ~8HP:

http://www.electriclaunch.com/

[They made JFK's PT-109]