Why are companies moving away from AC systems to DC systems?
The shift that we are seeing is directly tied to the limited space in the vessel, energy storage and the need to future proof their vessel for years to come. The Onboard DC Microgrid is a perfect example of a system that is extremely compact for lower HP systems where the vessels are also very small. The microgrid can easily be utilized for batteries, fuel cells, variable speed gensets, or any other "new" power source that may come along in the next few years.
What is the main advantage for the DC Microgrid when compared to a more conventional DC installation, for a towboat?
To build on the first question, microgrid gives you the same functionality of a traditional DC grid system however it is extremely compact. The controls, drives, and off grid converter are all in on small box. This system is the go-to-choice for small towboats or tugs as the system is tested in the factory and ready to just drop into the vessel at the shipyard with very little labor/ cabling needed as compared to traditional AC or DC systems.
How to energy losses compare between the DC grid and AC?
"The best answer that I can give for this question is to refer to our ABB Generations article on Onboard DC Grid. To access the article please click here.
How can we get the highest bollard pull in tug fully electric?
This question can go in several different ways as it really is dependent on not only the top end bollard pull of the tug but also all the other task the tug will perform. Since the battery has a finite amount of energy stored the length of the trip to the job site, Fifi requirements, amount of time allowed to charge at the dock, etc. will determine the size of the battery pack and then for what and how long it can be utilized. This is typically where we want to start with an owner or designer at the beginning of the conversation to discuss all these factors and run a couple exercises to determine the feasibility of an all-electric/ battery system before the tug is detailed.
How well is Class and Regulating bodies accepting hybrid technology?
I would have to easily say very well. We have been working with all the major class societies as well as the local coast guards on hybrid systems for a while and it has typically been a situation of a pull of information by them versus a push of information for us hoping that they will accept. Rather appreciative on our side.
Are there harmonics and power quality problems on these AC electric systems?
There definitely can be if you do not design the system correctly and utilize filtering and conditioning correctly; that is the role of the integrator of the system. I am proud to say that with many different systems utilized in the market today ABB has shown that we are one of the leaders and very successful at integrating these systems correct the first time.
What is the typical duration (in hours) of charge for ABB applied Li-ion battery? What happens at the expiration of that time period?
"I believe this question is regarding the overall life expectancy of the battery. In our systems we typically design the system with a 10-year battery. At the end of 10 years the battery must be changed out and the old battery is recycled. For further information please read the attached ABB Generations article on battery recycling here.
In terms of onboard Hydrogen generation, you mention use of ammonia. My understanding is that producing ammonia is energy intensive (feedstock is NG in my understanding). Is this truly energy efficient for propulsion?
"There are currently a few different feedstocks for ammonia and yes natural gas is one of those. This question touches on one of the items that any of these systems must have answered which is infrastructure and the supply chain for any alternative fuel. This is no different than what is being looked at in the LNG world currently. For hydrogen production there are a lot of different scenarios being looked at and much like LNG some are not long-term solutions more they are a bridge to get us to better solutions. For more discussion on this topic please refer to the attached ABB Generations article “The future fuel picture: more than just hydrogen”.
What is your opinion of optimal power system for a large emergency response and rescue tug for northern hostile waters?
This is a very similar answer to the optimal bollard pull question. I would have to say that you need a dynamic system to be able to respond to the hostile waters as well as hitting the required speed that is necessary. With that, we would look at the operational profile at the beginning to determine the best system match for the owner. Since we have several available options of systems, we would look at the OPEX and CAPEX match first and then design within that particular system to match it to the dynamic needs for this particular tug. Not a specific answer but there are a lot of variable to consider on any of these systems before we find a true answer.
Tell is about the future of battery prices?
"This is a very hot topic, and the short answer is that we will see them drop as we already have. This is a combination of both the volume of batteries being used as well as manufacturing cost reducing which both have a positive effect on the drop in pricing. A good article on the price of batteries in other industries is listed and marine batteries will see the same overall trend. Read more here.