Hybrid Theory

[CharlieJ]

A few thoughts:
1. I wonder why, essentially every commercial ship operating today is diesel-electric.
2. Cruise ships have a "bank" of diesel gensets that come on line to meet increased electrical load and then cycle off when the electrical load diminishes.
3. From the perspective of the gensets on the cruise ships, propulsion is just another electrical load.

[tdoster]

Originally Posted by CharlieJ

A few thoughts:
1. I wonder why, essentially every commercial ship operating today is diesel-electric.
2. Cruise ships have a "bank" of diesel gensets that come on line to meet increased electrical load and then cycle off when the electrical load diminishes.
3. From the perspective of the gensets on the cruise ships, propulsion is just another electrical load.

1. Because like diesel electric locomotives, their efficiency is based upon torque loads. Low RPM torque needed to bring very heavy loads to speed. At speed, they loose their efficiency.

2. It is the most efficient way of operating heavy craft turning large props slowly and increasing maneuverability using turning pods as opposed to fixed props. It also makes more sense on a cruise ship where the electrical loads and demands of the ship help increase the efficiencies.

The efficiency curve is almost the complete opposite of diesel by itself.

As I think the OP stated, the advantage is during maneuvering of a hybrid, but the added cost would take a long time to pay for itself unless you spend most of your engine time maneuvering. Would make sense for someone who day sails, but not a lot of sense for a cruiser AT THIS POINT IN TIME.

3. True. But the electrical demands of a floating hotel are far different from say a tanker or container ship.

[Stumble]

Originally Posted by CharlieJ

A few thoughts:
1. I wonder why, essentially every commercial ship operating today is diesel-electric.
2. Cruise ships have a "bank" of diesel gensets that come on line to meet increased electrical load and then cycle off when the electrical load diminishes.
3. From the perspective of the gensets on the cruise ships, propulsion is just another electrical load.

There are only three classes of ships that routinely use diesel-electric drives.

1) cruise ships with massive hotel loads compared to their propulsion loads
2) ice breakers with low normal propulsion loads and massive peak demands during ice breaker operations
3) nuclear power ships of all types

1 &2 also have atypical desire for azipod maneuverability that direct drive diesels can't provide.

Most commercial ships are using direct drive low rpm (1-200) fuel oil engines. About as simple a set up as possible to create.

[pdf27]

Doing a little more reading today, and found some interesting stuff on fuel cells. Specifically, both the European Union and US Department of Energy are subsidising work to build fuel cells running on road diesel and capable of producing around 4kW of electricity in an effort to wean lorries off idling their engines to produce heat and power.
The current generation of truck APUs cost around $7,000 or so, so it's reasonable to suggest that a fuel cell based APU won't be much more than $10,000 (their target is ~€1,000/kW, which they think is too hard but would be about half of this estimate). Efficiency is said to be about 30-35% and lifetime (same as time between overhauls?) is around 20,000 hours with an overall weight of ~120kg.
The Watt&Sea drive pod produces 600N thrust at 6kts on 4kW, for a useful work of 1.85 kW (they're the only people I can find who publish what actual thrust they produce - static thrust is claimed to be 850N). Trying to compare that to straight diesel is a bit of a nightmare - the best I can find is this article, which gives static thrust values of 1,900 to 2,650N for a Yanmar YM20 (which consumes 5.4 litres/hour at this speed).

Each litre of diesel contains ~11kWh of energy, so the Yanmar is consuming diesel at a rate of 59 kW at this point. For 12kW of electrical power consumption and a 30% efficiency, a fuel cell is consuming diesel at a rate of 40 kW in the same period. Overall, that's a 50% fuel saving at full power and probably rather more at part load in conjunction with a suitable battery.

All this suggests that for a boat requiring about a 7 hp engine, a diesel fuel cell coupled to a podded electric motor is going to be a plausible option in the near future, with the fuel cells apparently to be sold in the US from 2016/17. These also have a number of nice side-effects - fuel cells are quiet, have very low vibration, and make using electric outboards and cooking more of a practical proposition. Coupled with a reasonably sized battery (say 1 kWh) and solar panels it should actually make a very neat system.

[Stumble]

PDF,

Interesting possibilities. But that is a pretty heavy weight penalty. Assuming the electric drive is 20kg in addition to the fuel cell that is a total weight of around 145kg. You can pick up a 7hp Diesel engine with an electric start for 20kg.

So any boat needing an engine this size needs to allocate a lot of extra weight to the engine system. And frankly a 7hp isn't a lot of power for most boats.

[pdf27]

I think you're being a little optimistic on weight - a Yanmar 1GM10 (9hp at 3600 RPM) is 71kg dry, probably 75kg once you include oil and coolant. The Watt&Sea unit is 12 kg plus 3.5 kg for the controller, so you're looking at something in the region of a 100kg weight penalty for going fuel cell/electric. Basically the weight of an extra crew member, partially offset by needing to carry a little less diesel (a third of a fairly small fuel load).
If you are only going to need peak power for a few minutes at a time, it's fairly weight-efficient to just add a smallish battery with high current capability and go for a bigger electric pod. The fuel cell can then recharge the battery after the need for peak speed has died down a lot - as I understand it people rarely travel great distances at full throttle, it's more commonly used for short periods of time to get out of danger.

The telling factor for me is that these are first prototypes, and being designed as truck APUs probably contain things that won't be needed on a boat (robust housing, 120V inverter, possibly even a radiator and cooling system, etc.). I'd be reasonably confident of a fairly major weight reduction in the first few years, although I would agree that they are liable to be heavier than a diesel unit for the first few years at least.

[tdoster]

Weight is a small consideration in the grand scheme. Chiefly, the added complexity and initial investment would have to be amortized long after the duty-cycle numbers, which are cut much shorter in a marine environment. Without a government tax credit or subsidy, the numbers in the grand scheme rarely work out, unless the equipment is used under ideal conditions to realize the cost benefit. Just as the Prius I owned a few years ago was a bad choice for a daily 100 mile commute.

If you send me $10 and a pre paid envelope, I will send you plans for propulsion that is completely green, very efficient, and the technology is proven and very reliable. The return on investment can be realized after a single season and the product has been proven and tested for decades long continuous duty cycles.

Can't take your money... SAILS

[a64pilot]

If someone comes out with an economically viable fuel cell, it could completely change transportation, both land and sea.
Think of a car that when you weren't driving, you could power your house or office or connect back into the grid.
Or a boat that would have "shore power" where ever it was without the noise and vibration of a generator and although 7 hp may not be much, it's possible to bank that 7 hp into a massive battery for higher hp demands when needed.
Just my opinion of course, and I am not an electric drive proponent normally, but a viable fuel cell would I believe change the rules.
I wouldn't hold my breath waiting on one though

[pdf27]

Originally Posted by tdoster

Weight is a small consideration in the grand scheme. Chiefly, the added complexity and initial investment would have to be amortized long after the duty-cycle numbers, which are cut much shorter in a marine environment. Without a government tax credit or subsidy, the numbers in the grand scheme rarely work out, unless the equipment is used under ideal conditions to realize the cost benefit. Just as the Prius I owned a few years ago was a bad choice for a daily 100 mile commute.

The reason I'm interested in these truck APUs is simply that they are likely to be built in far greater numbers than any yacht motor ever will be. In the US alone there are something like 300,000 refrigerated trucks, each of which will in a few years require an APU by law (idling increasingly being banned). The whole US truck fleet is something like 2 million, and within a few years it looks like all of them will have APUs too. Given the maintenance savings from a fuel cell APU, it seems likely they will capture the whole market given time - and with a typical life of 5 years, that's 400,000 of these being produced every year. When you get to produce things in that sort of number, prices crash and they become a commodity.
The report I quoted suggested that they think they can probably manage ~$1,400/kW capital cost with next to no maintenance and a ~20,000 hour lifetime. That's for a unit bolted to the outside of an 18-wheeler driven around the US in all weathers and exposed to a lot of salt on the roads in winter, rather than kept in a nice warm and dry engine room. The marine environment - so far as an engine is concerned - is actually pretty benign compared to what this is expected to be exposed to. They're absolutely not there yet with it, but give them 5-10 years and I suspect they'll start becoming very popular for anybody who wants a portable generator capable of running a lot of hours (cheap diesel gensets will probably always win if you're only using it occasionally - in terms of duty cycle these will end up being more Northern Lights than Alibaba).

[a64pilot]

Originally Posted by tdoster

Without a government tax credit or subsidy, the numbers in the grand scheme rarely work out, unless the equipment is used under ideal conditions to realize the cost benefit. Just as the Prius I owned a few years ago was a bad choice for a daily 100 mile commute.

Explain that please as I thought the long daily drives was exactly when the Prius made sense, it doesn't make sense for the person that drives barely 100 miles a week, but does for the person that drives 100 miles a day.

[pdf27]

Originally Posted by a64pilot

Explain that please as I thought the long daily drives was exactly when the Prius made sense, it doesn't make sense for the person that drives barely 100 miles a week, but does for the person that drives 100 miles a day.

Depends on the sort of driving you're doing.

• When running at constant speed on a highway, the Prius exclusively uses the gasoline engine and all the hybrid bits are merely ballast which force it to burn more fuel to travel the same distance.
• When doing stop-start driving (e.g. in cities) the Prius switches to electric drive. That means whereas a gasoline engined care will be consuming fuel when stationary, a hybrid will use next to none. Overall, efficiency is much improved particularly as a hybrid can recover energy from braking.

[edit - see http://www.streetfire.net/video/143-...uel_180378.htm for an example of why a Prius can be pretty uneconomical when driven in a way that is inappropriate to the design of drivetrain]

This is why hybrids are typically poorly suited to marine applications - unless for something like a harbour tug they don't tend to do much stop-start driving but rather spend long periods of time at constant (relatively high) power. What efficiency gains are seen are most likely to come from the electric motor acting as a gearbox, allowing larger (and so more efficient) propellers to be fitted.

However, there are some side benefits to electric drive which may tip the equation **if** the rest of the technology gets mature enough (fuel cells are one promising way this might happen).

• Replacing propane cookers with induction hobs means one less fuel to get your hands on and has to be safer too.
• Similar logic applies to outboard motors and petrol, although that technology is rather less mature.
• Many (mostly larger) boats have a generator fitted in addition to a main propulsion engine. Going all-electric has the potential to consolidate these.
• Packaging becomes much easier if you don't need a direct mechanical linkage from your engine to your propeller. The new aircraft carriers for the Royal Navy are exploiting this to get significantly more usable internal space.

Right now a simple diesel engine is a lot cheaper, enough so to buy a tankerload of diesel fuel and more than make up for the lower efficiency. The thing is, diesel engines are a mature technology and frankly aren't going to get a lot cheaper over time. The various new potential ways of generating electricity from diesel power (microturbines, fuel cells, etc.) are not yet mature and have the potential to come down in price radically - with fuel cells being the the most promising because of the truck APU application.

[tdoster]

Originally Posted by a64pilot

Explain that please as I thought the long daily drives was exactly when the Prius made sense, it doesn't make sense for the person that drives barely 100 miles a week, but does for the person that drives 100 miles a day.

Because there are far more calculations then just the simple factors of fuel used to get from point A to point B.

You have to break it all down to actual cost per mile driven in the grand scheme. Including things like insurance premiums, maintenance, duty cycle, resale value @ particular milestones, etc. At 30 - 40K miles per year driven, the math did not work. I have a spreadsheet on every car I have owned in the past 12 years. I go through a car every year and a half and calculated the per mile costs of each.

[tdoster]

Originally Posted by a64pilot

If someone comes out with an economically viable fuel cell, it could completely change transportation, both land and sea.
Think of a car that when you weren't driving, you could power your house or office or connect back into the grid.
Or a boat that would have "shore power" where ever it was without the noise and vibration of a generator and although 7 hp may not be much, it's possible to bank that 7 hp into a massive battery for higher hp demands when needed.
Just my opinion of course, and I am not an electric drive proponent normally, but a viable fuel cell would I believe change the rules.
I wouldn't hold my breath waiting on one though

Conceptually, I am right there with you. They can convert sea water to a heavy fuel right now in the lab. Will it be economically practical for anyone but the military who is more interested in range then they are in cost per BTU? And even then, it is still at least a decade away and still theoretical.


http://www.nrl.navy.mil/media/news-releases/2012/fueling-the-fleet-navy-looks-to-the-seas

The problem is not creating electricity, the problem is there are no current breakthroughs in storing electricity. That is a huge hurdle to leap before we can turn it all from theoretical to practical.

[tdoster]

Originally Posted by pdf27

Depends on the sort of driving you're doing.
Right now a simple diesel engine is a lot cheaper, enough so to buy a tankerload of diesel fuel and more than make up for the lower efficiency. The thing is, diesel engines are a mature technology and frankly aren't going to get a lot cheaper over time. The various new potential ways of generating electricity from diesel power (microturbines, fuel cells, etc.) are not yet mature and have the potential to come down in price radically - with fuel cells being the the most promising because of the truck APU application.

Everything else was right on the money in my opinion, but they will continue to increase in costs because the Government is forcing stronger emission requirements onto off road applications.

This means we are just a few short years away from Catalytic Converters, DPF, Computer Controlled and high pressure fuel systems on our small diesels making them as complicated as a Volkswagen 2.0 TDI.

This will run many of the manufactures and especially the marinizers out of business and give us far fewer choices in the future.

The plus side is that it will force the market into newer technologies and take a lot of what is currently conceptual into reality. Many of our friends in Washington are personally vested and invested in newer technologies, so they have a lot to gain.

The negative side is we are forcing a technology revolution that is not maturing by necessity, but emotionally and theoretically. Thus the financial impact will be negative until necessity takes over. Difference in being told you need something as opposed to wanting it.

[tdoster]

Originally Posted by pdf27

Depends on the sort of driving you're doing.
Right now a simple diesel engine is a lot cheaper, enough so to buy a tankerload of diesel fuel and more than make up for the lower efficiency. The thing is, diesel engines are a mature technology and frankly aren't going to get a lot cheaper over time. The various new potential ways of generating electricity from diesel power (microturbines, fuel cells, etc.) are not yet mature and have the potential to come down in price radically - with fuel cells being the the most promising because of the truck APU application.

Everything else was right on the money in my opinion, but they will continue to increase in costs because the Government is forcing stronger emission requirements onto off road applications. Right now, is correct, but near term, it will become less and less economically feasible.

This means we are just a few short years away from Catalytic Converters, DPF, Computer Controlled and high pressure fuel systems on our small diesels making them as complicated as a Volkswagen 2.0 TDI.

This will run many of the manufactures and especially the marinizers out of business and give us far fewer choices in the future.

The plus side is that it will force the market into newer technologies and take a lot of what is currently conceptual into reality. Many of our friends in Washington are personally vested and invested in newer technologies, so they have a lot to gain.

The negative side is we are forcing a technology revolution that is not maturing by necessity, but emotionally and theoretically. Thus the financial impact will be negative until necessity takes over. Difference in being told you need something as opposed to wanting it.