hybrid tour boat-gctid820742

[green650]

A local builder here is building a hybrid ship for a San Francisco based tour company. Cant wait to see how it works out.

http://www.bellinghamherald.com/news/local/article166372237.html

[Norton_Rider]

The problem with Hybrid boats is that there's no such thing as regenerative braking on the water. So the batteries can only be replenished using some other external source such as solar cells, generator, etc.

[JThiessen]

Not necessarily - you have water flow that could be taken advantage of, as well as wind.

I'd sure like to see it developed and passed down to smaller craft.

One thing that I think will be a bit tough is the lack of motor noise as a safety item - another boats sound is often the first thing that makes you notice it. And in fog conditions it would be interesting

[Solandri]

"Norton Rider" post=820751 wrote:
The problem with Hybrid boats is that there's no such thing as regenerative braking on the water. So the batteries can only be replenished using some other external source such as solar cells, generator, etc.

Most engines operate most efficiently at a specific RPM and load. Pairing the wheels/propeller up with an electric motor and a battery can allow your engine to spend most of its time at its favorite RPM. When you need less power (maneuvering), you keep the engine off and run entirely off of the battery. When you need more power (transient power spikes due to pushing up against large waves, or on smaller boats the power hump needed to get up to plane), the electric motor adds its power output to the engine. You pick the engine size so its most-efficient RPM generates a little more power than is needed at cruise. That way the engine slowly recharges the battery while at cruise. When the battery is full, the engine shuts off and the boat cruises on battery for a bit to deplete some of that charge. Then the engine switches on again to recharge again.

The drawback is the additional weight of the batteries. So this is unlikely to be very effective for weigh-sensitive craft like a planing boat. But i could see it working for a displacement boat. Which seems to be what the boat in the link is.

[Norton_Rider]

You can't get something for nothing. The mechanical and electrical loses make a hybrid boat less efficient that a conventional one. A year or so ago Passagemaker Magazine had an in-depth analysis that showed that a conventionally powered boat was more efficient than a hybrid.

[Solandri]

You're not getting something for nothing. You're taking engine operating time at a low-efficiency RPM, and shifting it to a high-efficiency RPM. The higher efficiency means some of the energy in the fuel which would normally become heat, is instead available to do mechanical (or electrical) work.

https://www.researchgate.net/figure/260908987_fig6_Figure-6-Variation-of-thermal-efficiency-with-fuel-blend-and-engine-speed

You capture that extra energy in a battery. You then use it to drive an electric motor in lieu of or in addition to the engine, all to keep the engine at its efficiency peak for longer.

The question of whether this is all worth it depends on how much energy you gain via improved efficiency, vs how much you lose due having to carry around the extra weight of the battery and hybrid motor. It's a bigger deal for cars because they typically only need about 25 hp to cruise at highway speeds. So most of their operating is done far down in the engine efficiency curve. A hybrid powertrain helps a lot by allowing you operate the engine at higher power close to its efficiency peak for a short time, then run off the electric motor for a while until you need the engine again. (This is also part of the reason diesels get better mileage. Their operating RPM at highway speeds and loading is closer to their efficiency peak than for a gasoline engine.) Boats OTOH need a lot more power to move, so cruise at close to their efficiency peak. So there's a lot less energy to be eeked out from a boat engine. Nevertheless it is there, especially if you operate the boat a lot outside its peak efficiency range.

(Electric motors have their own efficiency curves too, but they tend to be a lot flatter, and peak around 90%-95% efficiency so drops in efficiency don't hurt as much.)

[Papa_Charlie]

I think with computer controlled technology today this is a viable option and very efficient. The military often uses electric drive vessels as do trains. The efficiency at the shaft is much higher than an engine as there is immediate torque provided to the shaft at any speed. Not so with a reciprocating engine at different speeds. Operating an engine at constant, most efficient speeds will require the least amount of fuel and prolong engine life. Keep in mind, that tour boats in SF Bay are constantly battling winds and currents as they dock and undock regularly. This requires a lot of engine thrust and that burns fuel. With electric drives they would eliminate the excessive fuel burn for high RPM required maneuvers.

They may not be the electric cars of today, but for a large vessel that burns a ton of fuel, these electric drives could be a very efficient alternative.

[Norton_Rider]

Here are a couple of articles with a lot of details. They address the efficiency issue:

https://www.passagemaker.com/technical/hybrid-science-part-1

https://www.passagemaker.com/technical/the-science-of-hybrid-propulsion-part-2

[green650]

The article did not go too in depth about the engineering of the boat. Maybe it's just going to have s couple of solar panels to help charge the batteries for the bow thruster??? And that might be all that's needed for marketing to call it hybrid and charge double the fare. Call it a hybrid, and they will pay extra.