The big news in maritime shipping has been recent advances in batteries and battery-management systems that now make electric drives and hybrid systems a viable propulsion alternative or supplement for larger vessels.
One of the major players in this high-tech, cutting-edge field is Vancouver-based Corvus Energy. BoatingLocal recently chatted with Corvus Vice-President of Americas Matt Koenig of Duxbury, Massachusetts, to find out why batteries and battery-management systems are generating such a buzz, and how the technology might one day benefit recreational boaters.
Koenig is quick to point out that Corvus’s expertise is in the fields of advanced battery-management systems, electrical architecture, and the manufacturing process and design of these systems. The company does not actually make the individual battery cells, which are based on a patented lithium-ion-polymer chemistry and built by industry leader Dow Kokam.
Koenig says to think of the battery cells as the muscle of the propulsion system, while Corvus provides the brain (BMS), the nervous system (electrical architecture) and a skeleton and skin (the innards and exterior casing). Corvus links multiple battery cells into modules, and modules into banks and arrays, and manages their output for maximum charge and discharge efficiency.
The company assembles the cells into 6.2 kilowatt-hour modules, which can be fitted together to make batteries capable of storing several megawatt-hours of energy (161 modules are needed to generate 1 megawatt). The scope of any sized array is technically possible, limited only by the amount of space onboard the vessel—and how much money the customer wants to spend. Based on a standard group 8D battery format, each module weighs about 140 pounds, delivers 3,000 to 4,800 cold cranking amps and a module can be configured from 14.8-88.8 VDC nominal, with capacities ranging at those voltages from 420-70 Ah’s.
“Our system provides the highest energy and power density storage in the world,” states Koenig. “Our management algorithms give the batteries a charge/discharge efficiency of 99.x percent. and a 100-percent depth of discharge without damaging the battery. Then the batteries can, in some applications, be fully recharged from 0 to 100 percent in as little as 30 minutes. Further, our system is optimized for reliability and safety.”
“These are the safest cells on the planet,” he continues. “They have infinitesimally low internal resistance, and thus negligible thermal management concerns. They also have no off-gassing. The entire system, including the cells and connectors, are submersible to 3 meters. Lastly, they don’t require maintenance and are 100-percent recyclable.”
One of the greatest benefits of the Corvus system is fuel savings. It allows a vessel to run off a smaller diesel at low speeds or loads or when sitting idle. When faster speeds or heavy loads require more power, the battery and parallel hybrid drive takes up the peak demand, a process known as, “peak shaving” or “load leveling”. According to Koenig, such a hybrid system can result in fuel savings of up to $300,000 per year for a 2,000-hp diesel tugboat, providing a return on investment in less than 5 years through fuel-cost savings alone.
While the Corvus system offers huge benefits for commercial vessels and larger diesel-powered craft with hybrid drives, it may be too pricey for the average recreational boater. But, Koenig added, “We are working with some of the new electric and hybrid-drive refit systems integrators for the recreational market. We are also working with the superyacht market to supply multi-megawatt banks to several high-profile private vessels.”
Another application for recreational boaters could be providing power for a large sportfisherman that spends a lot of time running at low rpm when trolling or idling to open water. At low speeds, the boat and its various electrical systems can run off battery power, with the diesels kicking in for trips to and from the grounds. Also, a smaller generator can do the job of maintaining the battery charge, thereby saving on interior space and providing a far more efficient day of trolling.
As mentioned, the Corvus system isn’t cheap. Each module currently costs $9,300 to $10,800. This includes the battery-management system and other elements, as well as a limited lifetime warranty. Koenig says that the price is expected to drop consistently in the near future, adding that, “These storage solutions, in many applications, will provide 5- to 6-figure cycle lives—an order of magnitude better than any existing storage modality.”
While the average boater my not yet be able to enjoy the advantages of advanced battery-management systems, you can bet that the technology will trickle down in the years ahead, to the point where we may even see viable hybrid power on smaller vessels. And if gas prices continue to climb, that day may come sooner than expected.