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 ) 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

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.

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.