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post #2 of Old 03-25-2012
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Re: Beta Marine - New Hybrid System!

I have said this on another thread about these beta hybrids but in my opinion, they do not make sense for most cruisers. The reason that people buy hybrids is to lower fuel consumption, lower costs, or lower noise. For the way most cruisers use their engines, it only succeeds at lowering noise in certain circumstances. Of course, there will be exceptions, but I don't feel that it makes sense for most people.

Sailboats tend to either operate for long periods of time at steady state or short periods of time in transients modes (docking). From an efficiency and cost standpoint, parallel hybrids make absolutely no sense unless it is operated as a plug-in hybrid. The problem is that at steady state, the motor/generator will be doing nothing and adding a bit of parasitic loss. If you were to use the motor to add power so that you could decrease the fuel consumption, this would mean that your batteries would be discharging. Unless you recharge them using shore power, you will need to burn even more fuel to recharge the batteries because every time energy is converted, you loose a bit. Therefore, at steady state, the motor does nothing unless you are using it as a plug-in hybrid with a large battery bank that you charge up on shore power and deplete when cruising. This could work for several hours of motoring but for people who may need to motor for 10's of hours, the battery bank would be prohibitively large. Unfortunately, we haven't come up with a denser way of storing energy than liquid fuels yet.

The reason that parallel hybrids work in cars (think prius, the volt is series), is that the cars are in a transient state most of the time and have proportionately more power. By operating in a transient state, you can use the electric motor where the gas engine is inefficient but even more importantly, you can recapture kinetic energy and store it in the batteries when slowing down. In a boat, you almost never "brake" and when you do, regen would not be enough so you will never capture any of the energy back. Also, because of consumers demand for acceleration, engines in cars operate at 5-25% of maximum power output when the car is cruising at steady state. Therefore, the engines are way too large to be efficient at these steady state power outputs. By using a hybrid system, the engine can be a much more appropriate size and the electric motor can make up for the lack of power during brief periods of acceleration. On a boat, the engine will be at 60-80% of full load where it is already very efficient and going to a smaller engine will not really help. The exception to this might be the cruiser who doesn't mind motoring very slowly but wants tons of power when docking but I have never really met this cruiser.

The person that I can see this making sense for is the one who goes on very short trips all the time and uses it as more of an electric drive than a hybrid drive. This would mean having a large battery bank that is recharged using shore power every night. Whether this makes financial sense depends on how much the person uses the system, the capitol cost, the cost of shore power and fuel costs. Environmentally, if you used the system enough to overcome the embodied energy, it would be better. The impact would certainly be effected by where you got your power from. Unfortunately, if you motor a lot, solar or wind are simply not going to be viable ways to charge because they will make up such a small percentage of your demand. You would also need to find a way to carry a lot of batteries which take up a lot of space and weigh a lot.

If you operate at steady state most of the time and have a well thought out diesel propulsion system, it will be very hard to beat because every time you do an energy conversion, your efficiency goes down. I would love to come up with a better propulsion system than a diesel but I don't think that it exists yet for a serious cruiser (electric makes sense for daysailors if they have a way of recharging). I have built 3 electric cars and 2 hybrid racecars and hybrid technology would simply not make sense for the way that my friends and I cruise.
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