Gas Turbine Generator for Hybrid Trawler?

[Mastadon]

Ive been searching this forum for any information regarding the use of gas turbine generators to feed battery powered electric motors. Not finding any threads Im guessing this is not a good idea. Is there any application which such a system would be beneficial? Would be much appreciated if someone could elaborate or direct me to the right thread.

[Jimbo1490]

Small gas turbines are thirsty beats, ITO specific fuel consumption. They are used whenever a highly reliable, very lightweight, low-maintenance power source is needed, and the high acquisition cost and thirsty nature (not to mention noise :D) are acceptable trade-offs for the other three 'must have' items. Can't see why you'd ever put one on a boat or ship.

Why not buy a used one and try it out? Garrett, Sundstrand, solar, Siemens and several others supplied thousands to the world's military, and many are for sale pretty cheap on the surplus market.

Here's one I found on ebay (http://cgi.ebay.com/International-Solar-Gas-Turbine-Generator-Set_W0QQitemZ140333685861QQcmdZViewItemQQptZBI_Generators?hash=item20ac8a1c65&_trksid=p3286.c0.m14&_trkparms=65%3A12%7C66%3A2%7C39%3A1%7C72%3A1205%7C293%3A1%7C294%3A50)

Jimbo

[mydauphin]

Exactly Jim...
Also if it gets nice salt air and something explodes.... The explosion might just sink your boat. Oh it is also a fire hazard... Would love to have one anyone to hear it roar....

[Yellowjacket]

Where do we start.....

Older small turbines are indeed, for the most part, thirsty engines. Most of these engines are basically aircraft Auxiliary Power Units (APU's) that are used for a number of applications that they were never really designed for. They are loud, expensive and aren't marinized..

There are however newer turbines that have fuel consumption that is on par or better than diesels. Engines made by Capstone employ heat recovery systems and that makes the efficiency very good. Not available for the marine market, but if someone wanted to maranize one, and if it was the right power size it would work fine for this purpose. Not cheap, but a lot smaller, lighter, and far more reliable than a smudge pot...

It is a very common misconception that turbines are inherently loud. Jet engines are, because they do work by pushing large quantities of air out the back of the engine, which creates a lot of noise. Shaft turbines are, not inherently loud, since the energy is being removed from the gas by the power turbine. The remaining noise is blade passing noise and that can be absorbed very easily since it is high frequency noise. We have a 800 hp turbine that, when it is running in the test cell can barely be heard. When you hear an aircraft with a power turbine (like a helicopter or a turboprop) these engines have no sound suppression and what you hear mostly is the propeller or helicopter rotors. A properly packaged turbine is a lot quieter than a diesel. It is also inherently a lot smoother, no diesel drone or vibration.

They are, generally much lower in maintenance and have the potential for a lot longer life than a diesel. Aircraft turbines typically see lives of 10,000 hours or greater.

Turbine engines have a lot of high energy components but current design practice is to design for containment. That is, if a blade were to let go it is contained by the cases. Turbines are made of mostly nickel base alloys and stainless steels, so there isn't much corrosion in the high energy parts. Salt air is not an issue if you occasionally water wash the engine by spraying fresh water into the inlet, and turbines can ingest incredible amounts of water with no damage, so you don't have to make sure that spray stays out of the engine. Turbines can injest a lot more water than a diesel ever could.

Older less efficient turbines also have high exhaust gas temperatures. Newer designs actually have lower exhaust gas temperatures than diesels. There is more exhaust gas flow so more water is required to cool the exhaust, but there is no reason for a turbine to be a fire hazard. The engine cases (which are hotter than a diesel block) can be wrapped with insulation and air can be circulated around the engine to keep the compartment cool.

Turbines are much smaller and lighter than a diesel, and therefore can take up a lot less room in the hull, which could result in an additional stateroom when compared with larger diesels.

Turbines however don't make much sense in applications where weight isn't much of an issue. In a boat like a trawler, weight isn't an issue really, so even an efficient turbine probably doesn't make a lot of sense here.

Now, if the boat is a planing hull and you can save as much as 10% to 15% or more of the overall displacement by replacing a pair of diesels with turbines, it makes perfect sense. When you save that much weight it significantly reduces the power requirement for a given speed. Turbines make perfect sense for larger fast boats (like about 75 feet and up). In those cases the higher specific fuel consumption of the turbine is offset by the lighter weight and the fuel consumption at brisk cruising speed (30kts and above) can be as good as or better than a diesel.

Designers of fast military patrol boats are figuring this out, and in due time the civil world will get it too. Turbines are also getting better in terms of fuel consumption, and that will drive the crossover point where turbines make more sense than a diesel down into the 1200 to 1500 hp range in the near future.

[gideon]

this is a company to watch , they are developing a turbine generator with 12 to 40 kwh power 120 kilo or better
http://www.etvmotors.com/

gideon

[Steve in Alaska]

http://www.brunvoll.no/public/cmsmm.nsf/lupgraphics/RDT%20leaflet%2012-2009.pdf/$file/RDT%20leaflet%2012-2009.pdf

http://www.microturbine.com/prodsol/solutions/other.asp

Maybe this is an acceptable solution to the efficiency and fuel issue?

Steve in Alaska

[gideon]

Unfortunately Capstones turbines are to large for our use , the max capacity needed is around 40 KW per hour thanks anyway

Gideon

[marshmat]

I wouldn't be at all surprised if Capstone's micro turbine generator, or something similar, really takes off in a few years.

As Yellowjacket pointed out, the noise and fuel consumption problems that used to be big downsides of gas turbines are mostly a thing of the past. It took an awful lot of R&D money and far too many CFD geeks to figure out how to get around these problems, but the current generation of large industrial gas turbines are comparable to, or better than, their diesel counterparts in many respects. The technology is, slowly, trickling down to smaller applications.

Cost, of course, is the one aspect of turbines that we have not yet figured out how to solve- they remain tremendously expensive for their power output. Even so, a number of cruise ships now have turbines as well as diesels, and they remain the unmatched champions of power-to-weight ratio when seriously high speeds are required from seriously large boats.

[Steve in Alaska]

I was refering to the staging of the turbines to optimize fuel consumption to output. If it can work financialy for public transportation, could it work on a nice boat with combined power and heating.

[FAST FRED]

If it can work financialy for public transportation, could it work on a nice boat with combined power and heating.

It might , but it has to be a bigger boat , 80-100ft + to make use of ALL the power generated.

Co generation is a really OLD idea , in NYC the Edison DC power plants were every 2 miles or so apart.

The waste heat was sold to heat many commercial buildings , and the buildings waste heat was plumbed under the sidewalks to remove the snow.

I think the future of cheap operation will be a very small scale copy of a cruise ship.

4 or 5 small really light weight gensets will cycle on at 90% load (for efficiency and long life) as house , propulsion loads are operated.

My guess is they will be complete packages and simply returned/swoped to a dealer for trouble shooting and service.

They may not even belong to the boat ,with Run time simply purchased from the dealer.

FF

[marshmat]

An interesting idea, Fred. Makes a lot of sense when you think about it- pour all your R&D money into one small, extremely efficient, well-engineered powerplant, and just parallel a few of them if a particular application needs more power. Doing it as self contained, swap-out units might piss off a few of the hardcore cruiser types, but I think most mechanics would love you for it: go to boat, remove broken unit, insert spare unit, take broken unit back to spacious well-lit shop for repair.

Quite a few years ago, I heard a similar idea being tossed around for fuel cell cars- in order to make mass production feasible, you'd build a module of 20 kW or so that would just plug into the car with a CAN link, fuel line and DC power coupling. A one-seat commuter car would have one of the things, a family sedan three, a pickup truck six.

I wouldn't be surprised if something like this is how micro-turbines or other relatively new powerplants end up in the mass market. (A turbine's relative insensitivity to fuel type- needing only minor tweaking to convert between light and heavy fuels- could be a huge boon to boaters....)

[Yellowjacket]

The concept of a very small turbine and a group of them paralled together is logical, but there are issuse with making turbines that small. The problem is that the efficiency falls off as the turbomachinery gets very small. Things like blade tip clearance don't scale, so the losses get higher in very small sizes and the efficiency of a 20kw unit isn't going to be as good as a 40kw unit.

Moreover, while you could make a unit of about 20kw, it isn't that much less expensive than a 40 kw unit. Things like the fuel control system and lube systems are essentially the same cost if the engine is 20kw or 40 kw. The rotating parts are cast, so only the edges are finished, and it doesn't cost much more to machine the larger part, maybe 15% more when you consider setup time. That is why, as turbines get larger they are more easily able to compete with diesel engines. A 20kw microturbine is likey to be about 3 or 4 times as expensive as a 20kw diesel unit.

The Capstone units generally run about $1,000/kw for a 30kw unit. That is about twice that of a marine diesel unit including an enclosure. The efficiency is about the same, and the Capstone unit is more quiet and has less vibration, so I am not suggesting that there aren't advantages to a microturbine in a marine power generation application. The issue of cost might not be a big deal in a 80ft or larger yacht.

The issue with the Capstone units are that the rotor system is supported by air bearings. Air bearings don't have much load capacity and therefore can't take a lot of shock and vibration. Moreover, the temperature of the air increases inside of the air bearing, and if there is salt in the air you could create problems with the solids being introduced to the bearing that is riding on a film or air that is very thin and doesn't like contamination. Air cycle machines in aircraft use a turbine to expand engine compressor air and run a compressor that pressurizes the cabin. For a number of years ACM's have utilized air bearings. The air cycle machines in some fighters (notably the F18) have problems with premature bearing failure that some attribute to salt air getting into the bearings. For that reason it is likely that a microturbine in a marine application would be better off with a more conventional rolling element bearing system for supporting the shaft.

In short, a microturbine could and surely would make a very light, small, quiet and efficient marine generator. But in order to be successful, it is going to have to be specifically designed to work in the marine environment, and right now there aren't any such animals that I know of, and we are pretty tuned into this world.

The US Navy issued a request for proposals for a 40kw marine gen set for small craft that had a weight goal of 10 pounds per kw and those proposals were due in January, are currently being evaluated. I know of at least one of the proposals submitted included a microturbine solution. We will have to see what the Navy does, but if they do a turbine it could be commercially available in 3-4 years.

[mark775]

I am thankful for Yellowjacket's presence. I went through this a few years ago - trying to find the right balance of reduced weight and reduction and control to make a turbine an efficient alternative in a boat. I am all ears and hope to go this route some day... An interesting means of occupying our time while waiting... http://www.youtube.com/watch?v=bEXxkWXncuo Are these small enough (not shafts, tho)?

[Steve in Alaska]

Wilson has a 300 kWe microturbine that uses ceramic components and a unique three-stage turbine
http://www.wilsonturbopower.com/micro_overview.html

Some marine offerings here, however it looks very large.
http://www.vericor.com/power-generation.html

I had a link at one time to a site that developed staged microturbines using turbo-charger components - but I just can't find it right now.

[Yellowjacket]

The Wilson engine is interestig, but the problem with it is that it is a very low specific speed machine. This means that the parts are bigger and therefore more expensive, and there are more of them since they slowed everything down. This is necessary to get the stress down in the ceramic turbine wheels. The problem is nobody has yet been successful in making a ceramic turbine that big (13 inches diameter) yet. Most of the ceramic manufacturers start to choke at a 6 inch integral bladed wheel. The low stress is an advantage, but the wheels are still a technology challenge. I'll be more impressed if they successfully demonstrate a few thousand hours on one, but my bet is that's still a good way off.

[Steve in Alaska]

Thank you everyone, I am hopeful to use a microturbine electric hybrid in my retirement home, currently planed to be a 75' wavepiercer. This is still many years away. Capstone is doing great things with electric hybrid automobiles right now, and there are a great many different things on the internet. But I think this is going to take someone with the desire to see it done actually do it and then have everyone copy along in good engineer fashion.

[FAST FRED]

," but I think most mechanics would love you for it: go to boat, remove broken unit, insert spare unit, take broken unit back to spacious well-lit shop for repair."


This is exactially the concept used today for tour or dinner boat HVAC systems.

Heated or chilled water is circulated to every cabin or zone , but the freon unit is one of 3 to 5 modules that are self contained.
The modules are yanked and ONLY circ water is touched by the crew , all the refrigeration and heat are in each module , that a licensed freon service repairs. Having working onboard spairs is done by simply making the system have more units.

No replacing from stores while a unit merely needs to be switched on.

The BIG boat main engines currently have fuel burns that are over 50% efficient.
With enough engineering perhaps this could be done (not cheap they all use turbos) in either an air cooled version or water cooled version that becomes cheap by large production runs.

Today a 50% turbine is not in sight , but 50% diesel's are working worldwide .

FF

[eric le marin]

50% efficient diesels are very big, and very heavy...
In fact, Warstilla is over 60% right now, very impressive if you consider they are on the theorical limits of the diesel cycle, but the engine is 6m high...

But you are speaking of low speed engines (<200rpm), and I haven't seen yet a "boat" with such engines.

I don't have precise data, but I thought that the diesel we are using are just above 30% of efficiency...

Considering that, small turbines seem to be a convincing solution, especially for vibrations and noise.

[FAST FRED]

To me a gear box would be the problem ,$$$$$, turbines run at high!!! speeds and 100 to 500 is a nice shaft speed.

Even 1000rpm boat shaft would be a 30-1 to 70-1 reduction.

An old truck turbo or two with a simple carb in the intake , and a spark plug, (kerosene or diesel) and you have the turbine , but actually using the power would be a problem.

FF

[eric le marin]

Maybe...
I am used to diesel electric propulsion on the ships I design, so I didn't see the problem here. The efficiency of electric propulsion is impressive nowdays. The losses are below 5%, and that is compensated by the accuracy of the choice on the propellers speed with a constant speed on diesel engines.

But the cost issue will clearly be the problem on a trawler...

[Yellowjacket]

Tyical high speed diesels have a Specific Fuel Consumption of about .36 to .38 lbs/hp hour. That equates to a thermal efficiency of about 38-36%. Not bad at all.

It depends on what you are driving as to what kind of gear ratio you want. If you look at a typcal small 500 hp turbine you are looking at power turbine speeds of about 36,000 rpm. If you look at a waterjet that absorbs 500 hp you are looking at 2600 rpm or thereabouts. That means a gear ratio of about 14:1.

If the boat is running a prop with high cruising speeds, the prop might run a good bit faster, so it depends on what type of drive you want to use and how fast it runs as to how much reduction you need. While the shaft speeds are higher, remember, the gears are smaller and aren't as expensive. We recently did a two stage gearbox for a 500 hp tubine marine application and it was a bit more expensive than a single stage box for a diesel, but remember the gears for a diesel have to be wider and more beefy to take the pulsation forces that the reciprocating engine makes and that makes the everything in the gearbox like the bearings and shafts heavier for a diesel.

[Yellowjacket]

Maybe...
I am used to diesel electric propulsion on the ships I design, so I didn't see the problem here. The efficiency of electric propulsion is impressive nowdays. The losses are below 5%, and that is compensated by the accuracy of the choice on the propellers speed with a constant speed on diesel engines.

But the cost issue will clearly be the problem on a trawler...

If you are going with an electric drive, a gas tubine could be a pretty interesting alternative. A high speed alternator is going to be a lot lighter than a diesel powered machine. On a trawler it might not be that important. but a typical 40 kw gen set weighs about 1200-1500 pounds, a comparable small gas turbine gen set would weigh about 200 pounds and take up not much more room than a big suitcase, and fuel consumption would be close to that of a diesel. Problem is it would cost probalby twice as much as the diesel. We tend to think that might be a good trade, one stateroom for the extra $15,000 you would spend on the turbine as compared to a diesel as a gen set on say a 80 foot yacht...

[Steve in Alaska]

From what I can see, the cost in a turbine is in the blades. So how about a Tesla turbine? Ya know he had a working generator powered by one of his bladeless turbines (steam). Seems that it would also be pretty much imune to the marine environment also.

And again, I bring up the CHP (combined heat and power) concept as I feel any thoughts on efficeincy should include the reductions in those systems enabled by using a device that has as a byproduct so much heat. Even cooling can be produced from it.

Steve in alaska

[eric le marin]

Heating is a good point for Alaska...

[Yellowjacket]

From what I can see, the cost in a turbine is in the blades. So how about a Tesla turbine? Ya know he had a working generator powered by one of his bladeless turbines (steam). Seems that it would also be pretty much imune to the marine environment also.

And again, I bring up the CHP (combined heat and power) concept as I feel any thoughts on efficeincy should include the reductions in those systems enabled by using a device that has as a byproduct so much heat. Even cooling can be produced from it.

Steve in alaska

CHP is very good, but it costs a good bit if you want to get useful work out of it. Gas tubines with heat recovery are efficient (about 33%), but the temperature coming out of the exhaust isn't hot enough (around 600 degrees F) to do anything more than space heating unless you use organic rankine cycles and ORC's aren't very efficient. If you are space heating, a 1,000 hp turbine can heat or cool a Wal Mart, so unless you need process heating there isn't a lot you can do with waste heat in a marine application. Better to try to get higher power efficiency from the system.

If we are talking ground based sytems, then CHP makes a lot of sense. We are doing a DoE program with a goal of 50% thermal efficiency from a combined (gas turbine with a Rankine bottoming cycle) cycle system. The waste heat is at about 300 degrees F so you can still use it for heating or a one stage chiller. The cost goals are pretty impressive, similar to a 1,000 hp diesel.

[Yellowjacket]

From what I can see, the cost in a turbine is in the blades. So how about a Tesla turbine? Ya know he had a working generator powered by one of his bladeless turbines (steam). Seems that it would also be pretty much imune to the marine environment also.

And again, I bring up the CHP (combined heat and power) concept as I feel any thoughts on efficeincy should include the reductions in those systems enabled by using a device that has as a byproduct so much heat. Even cooling can be produced from it.

Steve in alaska

The Tesla Turbine is pretty interesting, in theory, but there's no such thing as a free lunch. In order to get high power density you want high rotational speed. Since the outer diameter of the disk is hotter than the inside the thermal growth near the rim reduces the stress in the outer part of the disk and increases the stress near the bore. In order to keep the stress down the disks need to be thicker at the bore than at the outside. This limits how many rotors you can have in your system, and increases the windage losses on the outside of the disks. The Tesla concept has thin gaps between the disks and you need a lot of disks with nothing in between them. That brings us to the next topic.

Also you have to take into consideration the shaft dynamics. You have to get the first shaft bending mode above the operating range (you can take the first bounce and the first rocking mode below the operating range with soft shaft supports). What this means is that you can't have too long a shaft and this again limits how much work you can do.

No question that the theory works, but it isn't easy to make a practical machine out of it.

Smaller turbines typically cast the blades as part of the disk, the cost of these rotors isn't bad, but you are limited to uncooled parts and that limits operating temperatures. Much of the reason that turbines are expensive is that they don't make many of them. If the production rates were higher and more automated machining and higher production rate processes were brought to bear, then the cost would come down a lot. At GM they did a lot of work in the 80's to get the cost of a small automotive gas turbine down to near that of a V8. They got pretty close, but never quite got to parity or lower cost then the recip. Turbines, once they are running are very clean, but on startup there is usually a good bit of unburned fuel that goes out of the exhaust. Startup emissions were never going to be as good as a piston engine if you wanted to start quickly, and the increasingly tighter controls on that aspect is part of what killed the program.