OSSA POWERLITE^®
Diesel-Electric Marine Propulsion Systems and Accessories

2.  How is the OSSA Powerlite^®  system different from the equipment being sold by your competitors?
OSSA Powerlite is the only total diesel-electric solution.  All of our competitors, to a greater or lesser extent, are selling individual components - a motor, generator (with or without the engine!), a control system and possibly a bow thruster.  You are left responsible for figuring out the power distribution and circuit protection, designing and implementing a high voltage electrical safety system, integrating the house 12vdc and 115vac circuits and making sure the other accessories like air conditioning all work together.  OSSA Powerlite addresses all these and gives you a complete and total solution matched to your requirements.  The components of your OSSA Powerlite systems are designed and guaranteed to work together in a seamless, safe and trouble-free package.

3.  What about using a battery bank?
A drive system that uses only batteries is referred to as "electric" propulsion.  One that uses both batteries and a generator is called a "hybrid-electric" system.  A system that uses a diesel generator to directly power the motor with no battery bank is called a "diesel-electric" propulsion system.  Because of high power demands and limited storage capacity, electric propulsion (using only batteries) is only practical for very small boats motoring short distances.  Most people are now familiar with hybrid-electric systems through the new automobiles where the combination of a generator and electrical storage in batteries provides benefits in acceleration, fuel economy and braking.  In marine applications, the electrical storage benefit gained with a hybrid system rarely justifies its weight, cost and complexity.  For this reason, OSSA Powerlite is nearly always configured without a battery bank as a "diesel-electric" propulsion system.  If there is a compelling reason to use battery storage in a particular application, the OSSA Powerlite can be set up in a hybrid configuration.

4.  How can you get better fuel efficiency by generating electrical power and putting it through a motor than by powering the propeller directly from the engine?
Since no electric motor or generator is 100% efficient, it seems counter-intuitive that placing them between the diesel engine and propeller could improve fuel efficiency.  Nevertheless, the fact is that, when a diesel-electric system is properly designed and configured, it can and does substantially improve fuel economy.  (Remember, the move to diesel-electric drive for commercial ships is largely driven by the desire to reduce fuel costs.)  The potential to improve efficiency is based in the fact that by "decoupling" the engine from the propeller, it is possible to reduce the substantial energy losses of the propeller while operating the engine within a more optimum power range regardless of load conditions.  It is worth noting that simply "generating electricity and putting it through a motor" does not automatically accomplish this.  A diesel-electric system simply creates the potential for fuel savings.  A poorly designed electric drive system could be less efficient than a conventional drive.  Improving fuel economy is a primary design goal of the OSSA Powerlite system.  Our Technical Library has an extensive discussion on how diesel-electric propulsion can provide significant fuel savings.

5.  How much electrical power do I need to replace my diesel engine?
It is a fact that you will need less electric HP to power your boat than you would conventional direct diesel HP to get the same performance.  Determining how much less requires a bit of digging into the specifics of your boat and its intended use.  A cruise through the internet will find factual-sounding statements of everything from 25% to 95% of a conventional diesel.  In our experience these straight conversion formulas (i.e. 65% of normal diesel HP) and rules-of-thumb (2.5kw per ton) are such broad oversimplifications as to be virtually meaningless when it comes to a specific installation.  Obviously, this is much too important a topic to gloss over so we explore it in detail in our Technical Library.

6.  Why does OSSA Powerlite use DC power instead of AC?
Any system that incorporates a variable-speed motor (all electric marine propulsion systems) uses both alternating current (AC) and direct current (DC) voltage at various points between power generation and torque output.  Therefore, whether a system is referred to as "AC" or "DC" is generally a question of the form the electricity takes while is is being transmitted.  In other words, if the power on the main buss is "DC", then the system is referred to as being a DC system.  While it may sound academic, the choice of maintaining the buss as AC or DC power has a significant impact on system safety and how it interacts with other non-propulsion house systems.  Our Technical Library contains a detailed discussion of the subject and an explanation of how OSSA Powerlite's choice of DC power increases system safety by 5x over that of an AC system while enhancing the performance, compatibility and reliability of other, non-propulsion systems.

7.  If diesel-electric propulsion is so great, why isn't it more common?
The short answer is technology development.  While it has been possible to power a small vessel with a generator and motor for many years, the system would have been expensive, heavy and relatively inefficient.  Recent (in some cases, very recent) advancements in diesel engine, power electronics and electric motor technologies have changed this.  For example, ten years ago a typical variable-speed industrial motor might have been 85% efficient.  OSSA Powerlite motors now achieve efficiency as high as 98.9%.  Only two years ago, the lightest 200kw generator you could get weighed over 4,000 lbs.  The OSSA Powerlite 200kw generator comes in around 1,400 lbs wet.   Add to this is the fact that power electronic devices have declined in cost by as much as 90% over the past ten years and attained a level of reliability that often exceeds that of their mechanical counterparts.  Taken together, it means that the time for yacht-compatible diesel-electric propulsion systems has finally arrived.

8.  How does the cost of an OSSA Powerlite system compare to conventional propulsion?
The OSSA Powerlite system will probably be more expensive.  How much more depends on how you are configuring the system.  For example; Let's say that you would normally use two 150 hp Yanmar engines and a 16kw Fischer-Panda generator.  If you replaced this with a single 150kw OSSA Powerlite generator and a couple of 100hp OSSA Powerlite motors you would have a lighter system, better fuel economy and about the same "usable" power at virtually no additional cost.  If you instead decided to use two 100kw OSSA Powerlite generators and a couple of 150kw motors, you would get even better fuel efficiency and greater redundancy, and considerably more propulsion power but the cost would be higher.  In general, plan on the cost being around 150% to 200% what it would be with conventional equipment.  For a typical new boat build, the premium paid for a complete OSSA Powerlite system adds about 5% to the cost of the boat.

9.  How does the weight of an OSSA Powerlite system compare to conventional propulsion?
As with the question of cost, it depends on how you configure the system and what components you are replacing.  OSSA Powerlite eliminates  the need to have a separate generator for air conditioning, battery charging, cooking and so forth.  In larger vessel, it also eliminates much of the "power conditioning" equipment required.  Since the OSSA Powerlite system gets better fuel economy, less fuel has be carried to attain a given range.  Taken together, most OSSA Powerlite installations are lighter in weight then conventional systems which are sized to provide the same level of performance.

10.  What about using fuel cells, solar power and/or high tech batteries like lithium ion?
The OSSA Powerlite system is fully compatible with all of these technologies.  The questions to ask yourself are;  How much to they add to the cost?  Will they provide the amount of power I require?  How long will they last?  And, in the case of fuel cells - Where will I get the hydrogen to power it?  The OSSA Powerlite system (like the hybrid cars from Honda and Toyota) is an "open plan" power concept.  Today's systems are being delivered with our advanced diesel generators because the marine infrastructure is diesel and this engine technology provides the best performance for the money.  If and when another power source (fuel cell, stirling, solar or other) makes technical and economic sense it will be pretty much a drop-in substitute for the existing diesel generator.

11.  OSSA Powerlite uses the tag line "Propulsion Duty Rated™" for your generators.  What is that all about?
"Propulsion Duty Rated" is much more than just a promotional tag line.  It is our promise that your OSSA Powerlite generator is going to give you performance that you expect and require in a propulsion application.  Few generators are able to provide sustained power output at their rated capacity for days on end.  Those that will often use rating methods that can be confusing for even the most experienced buyer.  For example; A generator rated to provide a continuous output of "50kva"  is generally rated with a 0.8 power factor.  While the rating may be technically accurate, it will not provide 50kw of power for propulsion.  It will provide 50kw x 0.8 or 40kw.  To avoid this kind of nasty surprise, OSSA Powerlite generators are rated according to international "prime mover" specifications for generators in diesel-electric commercial ship applications.  These specifications require the generator to not only be rated at continuous duty output, put to have the ability to provide bursts of power over and above this rating.

12.  I am very interested in the whole concept of electric drive but the more I search the more conflicting information I find.  Is there a reliable, independent source for information?
As with most new technologies, good information can be hard to come by even from normally reliable sources.  Most magazines and technical writers recognize that diesel-electric propulsion is potentially the greatest new technology to come to yachting in many years.  They don't want to get left behind and feel they need to say SOMETHING whether they are familiar with the technical issues or not.  Add to this the usual internet forum self-proclaimed "experts" and the result can be both humorous and frustrating.  For example; the FAQ section of a brochure describing all electric boat (recently introduced by a well know company) attempted to explain why electric motors outperform diesel engines of similar horsepower by saying,  "One must not focus on the impact of propeller RPM on vessel speed".  It doesn't take and expert to recognize a non-explanation when they hear one.  The good news is that, with time, electric yacht propulsion technology will inevitably become better understood by the boating public, just as hybrid electric cars have.