Sustainability at sea: Reducing fuel consumption and emissions of marine vessels

Dan Olsen Lab Group

From left: Kirk Evans (lab manager); Mark James (technician); James Tillotson (test engineer); Daniel Olsen (mechanical engineering faculty); Josh Moothart (senior in mechanical engineering).

Daniel Olsen and his lab are known for their top-notch work in investigating and minimizing fuel consumption and emissions by reconfiguring engine systems. Their latest project, funded by Siemens, accomplished just that.

Current inefficiencies

Marine vessels are huge consumers of fossils fuels and are inherently inefficient, both in terms of quantities of fuel burned and resulting emissions to the atmosphere. Marine power systems designed to improve fuel efficiency and reduce emissions can have a significant effect in reducing environmental impact and lowering operating costs.

Conventional diesel-electric propulsion plants produce power at constant frequency which requires operating their diesel engines at constant speed, regardless of the power demand which can vary widely depending on what the task the vessel is performing (e.g. open-ocean transit versus slow-speed maneuvering). The requirement for the engines to always run at constant speed prevents optimal (most efficient and cleanest burning) operation. Additionally, a conventional diesel-electric vessel must have enough engines in operation to be able to respond to any situation immediately in the event of an emergency on board that results in the loss of one engine. This requirement forces the inefficient practice of placing a redundant, “just-in-case” engine in service which is consuming fuel and producing emissions without contributing to the vessel’s operation.

Testing the technology

Siemens is addressing this issue with cutting-edge technology that incorporates variable speed power generation and stored energy via their Blue Drive PlusC© system. These systems have been installed globally on nearly 40 operating vessels, including offshore support vessels, construction vessels, large commercial fishing boats, ferries, and oceanographic research vessels, to name a few.

The Blue Drive PlusC© system has been a commercial success, well-recognized and lauded in the marine industry over the past few years, but no independent, third-party evaluation of the system had been conducted to actually quantify the fuel consumption savings and emissions reductions achievable.

Siemens reached out to Olsen’s lab to conduct testing that mirrors the conditions experienced at sea, contrasting the performance parameters of a constant engine speed power generation system to that of a system allowing variable engine speed (variable frequency) to optimize engine efficiency. Further, Olsen’s team was able to build a simulation of available energy storage so that the savings realized with eliminating the redundant engine could be effectively modeled.

Fuel consumption graph
Comparison of brake specific fuel consumption for constant speed and variable speed control. There is a significant reduction in fuel consumption for variable speed, especially at low engine power.

The testing protocol was developed by Olsen’s team utilizing a Cummins QSK50 Tier 4 engine located at the CSU Engines and Energy Conversion Laboratory. The test sequence duplicated a notional ship operating profile, first with constant engine speed and then followed by variable engine speed operation that replicated the Blue Drive PlusC© system. Additionally, the imposition of the variable frequency fuel consumption and emissions on stipulation multi-engine operation scenarios was conducted. This modeling was able to predict the impact of including an energy storage capability.

“Having access to the Cummins QSK50D in the EECL at CSU really benefited the study because the engine accurately represents engines used in marine diesel applications,” said mechanical engineering senior and project lead, Josh Moothart.

Future potential for the marine industry

Their findings showed that the variable speed system was 5-7% more fuel efficient for each engine on average, resulting in reduced emissions and the potential to also reduce engine maintenance costs. The multi-engine model incorporating energy storage showed possible savings of up to 15% in fuel consumption. Emissions reductions were even more promising with up to 40% reduced NOx emissions.

“It has been a privilege to work with Siemens on a project that has such a large potential for reductions in worldwide fuel consumption and pollutant emissions,” said Olsen.

Daniel Wise, Director of Federal Marine Programs for Siemens added, “Siemens has been delighted with the professionalism and responsiveness of Dr. Olsen’s team. The results of the testing conducted at CSU offer independent confirmation of the viability and merit of the Blue Drive PlusC© system, which was obviously great news for Siemens. We are confident that the system will continue to enjoy success in the marine industry and are looking forward to opportunities to work with CSU in the future.”

Olsen is currently in discussions with Siemens about a potential field project where the Blue Drive PlusC system would be evaluated on a ship servicing a U.S. inland waterway.