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Old 15-08-2012, 12:06   #1
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Pod Placement on a Powerboat Refit

Hi everyone,

I am working on a project that's a bit off from the norm for this site but I also know that you guys are an invaluable source of information (and sometimes entertaining misinformation).

I'll explain more about the project as a whole in another post but the simple breakdown is that we are restoring a 126' classic steel fantail yacht built in 1929 and retrofitting it with modern technologies to prove the viability of various green techs and products for the vessel refit market. if everything goes well, we'll have a zero-fuel yacht when finished that doesn't sacrifice anything in the process to be sustainable and doesn't cost a fortune.

Aside from the predictable solar and all that, our main focus is on the propulsion systems of the vessel. Our solution is a hybrid approach witch uses a SkySails wind propulsion system for the bulk of propulsion needs and then combines this with a hydrogen-powered electric motorized propulsion system.

It's the motorized propulsion system that I'm writing about today:

Our boat currently is powered by twin 250 hp GM diesels directly driving a pair of fixed props on either side of rudder. (like this -> (not the same vessel but equivalent stern)




We will be removing the existing mechanicals and installing four electric pod drives which will also replace the mechanical rudder.

Two of the pods will be lower power and will be installed in similar positions to the original propellers. These will be fully azimuting pods that can rotate 360 degrees and turn independent of one another. Controlled together they allow for very versatile and efficient steering and also provide forward or reverse (or for that matter sideways) propulsion as needed. These pods will be in use even when under wind power on an as needed basis for steering the vessel but in most cases would operate far below their full power.

The two other pods will be mounted in a fixed position further forward and probably higher on the hull. These pods will not be used for steering but will instead be the primary forward propulsion when operating solely on the motors. They will be more powerful than the steering pods and will ideally be able to handle around 80% of propulsion needs on their own if needed.

These pods however have an important role that for our purposes is actually a bit more integral than simply propulsion. Because the SkySails system that will be fitted to the vessel produces more than enough propulsion power to carry the boat at max cruising speed, we'll have excess power that needs to be captured. This will be accomplished by using the pods themselves as regenerative power generators so that as water passes them, the propellers turn with the electric motors in the pods working as electric generators and feeding electricity back into the ship's power grid. This is one of the main ways we're getting around the usual "let's load a ship down so much with solar panels that there's nowhere to fish" approach to green yacht design.

What I need to figure out, is where and in what sort of configuration should our drive pods be placed to give us maximum regenerative potential. Because the SkySails does such a good job pulling the boat, a limited amount of added drag is not a problem if it means we can be able to hit the most power production potential off that drag.

We're not set on only having four pods or not considering some other sort option such as a retractable system as well for the regenerative approach.

Right now though, we're just trying to get a general idea of how we should basically layout this propulsion system and how much power needs to go where and of course how to best take advantage of the hull design and all that.

My question to you guys is, where in general would the ideal locations for such a system be on a boat such as this:





(Older picture -- she no longer has the NASA arrays on board)

Here are the specs:

LOA: 126'
Beam: 23'
Draft: 9'3"
Displacement: 247 tons

Currently listed cruising speed is 11 and max is 12. We are thinking that we can be somewhere between 15-20 on those numbers when we're done due to some of the techs on board including low-friction coatings, hull refinements, and the upward pulling effect of the SkySails kite.

Any ideas?
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Old 15-08-2012, 12:18   #2
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I would think the main drive/regen pods would need to be in an undisturbed path of flow for greatest efficiency. That would mean beneath the bottom of the hull ( increases draft) or out the hull sides at an angle to keep the pods within beam max ( susceptible to cavitation when rolling).
Sounds like an interesting project, I'd be interested to see if the final product can be scaled down to smaller boats.
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Old 15-08-2012, 13:45   #3
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Re: Pod Placement on a powerboat refit

This is a very interesting project. Please keep us posted.

Have you looked at flywheel energy storage systems? http://www.vyconenergy.com

I would be interested in knowing if anyone has ever tried such as system in a marine environment.
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Old 15-08-2012, 20:17   #4
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Re: Pod Placement on a powerboat refit

Quote:
Originally Posted by Heritage View Post
This is a very interesting project. Please keep us posted.

Have you looked at flywheel energy storage systems? VYCON Flywheel Energy - Home | Battery Free Power Quality

I would be interested in knowing if anyone has ever tried such as system in a marine environment.
Thanks for the lead Heritage.

I had never heard of these guys but spent a while digging through their site. It looks interesting but the website itself seems to be a bit purposefully ambiguous (it doesn't exactly tell you how it stores anything or provides capacities or anything) but could have merit on board a boat if it lives up to the ideas presented. I've sent the president of the company an email. We'll see
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Old 15-08-2012, 20:57   #5
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Re: Pod Placement on a Powerboat Refit

It stores energy by reving up a flywheel when there is a surplus of energy, then slowing the flywheel to generate electricity when it is needed. Our university has purchased one of these units for installation in a research lab. It will be next year before I know how well the equipment performs.
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Old 16-08-2012, 09:06   #6
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Re: Pod Placement on a Powerboat Refit

@Heritage,

I got an email back from the president of Vycon. He's said that their product has to be so stable that even the small amount of motion of a ship would preclude them from functioning correctly. Still a neat idea though!
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