Hello! Or should I say, welcome aboard! In this edition of micro gas turbines in transportation, we’re going to be looking at micro gas turbines in the marine world. Marine transportation presents its own set of unique challenges not seen in other forms of transportation; although some of the common challenges and hurdles will be seen here too. If you haven’t read the other entries, or the introduction, I highly recommend you do so here.
Out of all the different vehicles and forms of transportation that will be covered in this series, the boat as we know it is one of the oldest ways of getting about. From rowing to sailing to paddle wheels and engines, the boat has a long history of carrying every kind of good and being imaginable. Much like the topic of turbines, marine transportation can take up oceans of information; in fact you might say that it’s a whale of a topic.
This blog will specifically cover a brief history of motorized marine transportation, where/how micro turbines can be used, and the inherent advantages and disadvantages. Let’s get started!
A Brief History of Engines in Marine Transportation
Steamboats became popular in the 19th Century when the Industrial Revolution was in its early stages. Steam engines like the ones designed by James Watt were used to propel everything from small riverboats like the ones that went up and down the Missouri river, to oceangoing steamships. The engines typically drove a propeller or “screw” or a large paddle wheel like what is commonly seen on a watermill. Different steam engines in different configurations dominated marine transportation throughout the 19th century, and by the turn of the 20th century, large expansion engines began to be utilized for oceangoing ships like the Olympic-class ocean liners as well as warships.
The steam turbine began to replace these expansion engines since they were far less complex than their reciprocating counterpart and offered an excellent power-to-weight ratio. Additionally, they were more efficient than other steam engines of the time. Although they were more expensive to manufacture, they required less maintenance and as such, the cost of procuring and operating the turbine is about the same. As a result, steam turbines exploded in popularity for propelling oceangoing ships. In fact, they’re still heavily used around the world alongside reciprocating internal combustion engines.
Large gas turbines have also been utilized in different marine roles for high-speed applications such as military use. Aeroderivative and other gas turbines are commonly used in conjunction with other powerplants such as a reciprocating engine. Additionally, they are sometimes used as the prime mover when the application can take advantage of the gas turbine’s high rotational speed, such as in a high-speed ferry. Their inherent light weight and high power to weight ratios have made gas turbines an attractive option for select applications as primary movers. In the applications where they are used alongside another primary mover, these configurations are commonly called “CODOG” or “CODAG”, which stand for Combined Diesel And/Or Gas.
So what about micro turbines? Where do they fit into the scheme of things for marine propulsion?
Micro turbines have been finding their way into the marine market as an alternate source of power onboard ships for applications like auxiliary power generation; this application is suitable for turbines since the power-demand will not have sudden spikes and decreases the way that it would in propulsion.
Depending on the specific application, however, micro gas turbines could be useful as primary movers, so long as the power output is adequate, and the load is constant. At sea a constant load is easier to come by if a boat or ship is moving at a constant speed and the sea state is not volatile. This however brings us to an important consideration for turbines both large and small, which is environmental conditions.
Boats and ships are subject to a wide variety of atmospheric and meteorological conditions that can range from pleasant to downright punishing, and as such, durability and reliability are important considerations, especially for turbines that have tight tolerances, and micro turbines where tolerances will be even tighter. In marine conditions, durability and reliability will be tested as the salty air can form deposits in the components of the micro turbine, and the entire assembly can be subjected to shock conditions from waves and storms. One last consideration is fuel; ships typically utilize low grade fossil fuel that is often dirty, but also very inexpensive. Typically known as bunker-c or fuel oil, this very heavy fuel can be easily combusted in boilers or in reciprocating engines (once they have been properly warmed up by burning diesel), but may not be usable in micro turbines, as only recently have heavy fuels been utilized in larger scale turbines. Compare to the very light natural gas or less volatile jet fuel that gas turbines normally run on, fuel oil could present reliability challenges for micro turbines.
The question you may be asking is what are the current applications where micro turbines are being utilized in the marine world? They’re commonly being used in conjunction with electric propulsion, which presents its own series of benefits and drawbacks for these applications. Some of the advantages of utilizing electric propulsion onboard boats and ships includes:
- Improved machinery layout and space savings
- Increased flexibility
- Reduced noise and vibration
- Improved reliability leading to reduced maintenance costs
- Reduced operating costs
- Fuel economy
- Reduced maintenance
- Reduced lost time/down time
- Configurable for maximum system availability/redundancy
- While batteries are not easily swappable during voyage, range extenders have the potential to be beneficial, replacing potential range concerns
The last bullet point is critical, and is where micro turbines come in. Similar to certain aviation applications and to what we are seeing in the automotive sector, micro turbines are very promising when they are used as power generation sources for electric propulsion; in essence, hybridized propulsion.
One notable example of hybrid shipboard propulsion that utilizes micro gas turbine technology is the MTS Argonon, a chemical tanker based out of the Netherlands. The ship utilizes Caterpillar dual fuel engines and micro turbines from Capstone to run on liquified natural gas, using a small amount of diesel as the ignition fuel. The Argonon is being touted as the first of its kind to run on natural gas, and is utilizing 2 micro turbines for cogeneration purposes, creating both heat for the natural gas to vaporize before being used in the Caterpillar engines as well as domestic heat for the ship and onboard power.
One last example I want to mention are electric barges; specifically those being built by the company Port Liner, which is also out of the Netherlands. The Dutch actually have a long history of utilizing electric boats in canals. It’s not feasible, however to electrify every waterway, particularly once you exit a canal and head into open water like the North Sea. As a result PortLiner has created a barge that utilizes electric battery power to supply energy to electric motors. Some of the key features of the Port Liner barges include having enough power for 35 hours of autonomous navigation, and zero emission transport with a reduction of 18,000 tons of CO2 per year.
Hypothetically, a range extender in the form of a micro turbine could prove useful should PortLiner look to create a longer-range version of their current fleet. It should be acknowledged however that adding such a system will disqualify it from being a zero-emissions transport. Although we should not minimize potential environmental harm, there are some serious upsides to utilizing micro turbine technology in this area. A micro gas turbine system will consume less fuel and emit less carbon dioxide into the atmosphere than its larger turbine cousins and reciprocating counterparts. While it’s not a solution for greenhouse gas emissions, it is certainly a step in the right direction!
Marine transportation has a rich history of using turbomachinery for propulsion as well as onboard power, (in fact, we may just have to cover it in a future series), and there are a variety of different applications where a micro gas turbine system could be utilized. Whether it is as the primary mover in small applications, or as a range extender in electrically powered barges or auxiliary power aboard oceangoing vessels, there is no shortage of places where these machines can be utilized.
It will be interesting to see what is in store for the future of marine transportation as emission regulations get ever stricter and fossil fuels become less feasible to use.
Coming up in next month’s rotation…
Next month we’ll cover micro turbines in rail transportation, and where they can be used.