Гибридная силовая установка

Land and Sea
Perhaps one of the easiest ways to understand the potential benefits of hybrid marine power is to look at automobiles, where similar systems have been in use for more than a decade. The most iconic hybrid now on the road is the Toyota Prius, a vehicle that can obtain unprecedented fuel efficiency both on the highway and around town. As delivered from the factory, the Prius is essentially a gasoline car with an electric assist. Its exemplary highway mileage actually has nothing to do with the electric drive and instead is the result of pushing a relatively light, streamlined vehicle with an efficient gas engine of modest size. The electric engine and battery system provide their greatest benefits in stop-and-go driving, where the electric engine aids in acceleration and returns energy to the battery bank when stopping. A more direct analogy to Watt Power would be Chevrolet's new Volt, which uses a pure electric drive system for propulsion, augmented by a gasoline generator that replenishes the battery supply. For shorter trips, both the Volt and Watt Power can operate without starting an internal combustion engine, but once that engine is engaged, the range is limited only by the fuel supply. — P.H.

We are cruising aboard Watt Power, a vintage 42-foot Grand Banks trawler owned by ReGen Nautic. The company's CEO, Pierre Caouette, is at the helm flanked by his partner and company co-founder, Lisa McKerracher. Both are lifelong boaters, and both have a long and successful record of entrepreneurial ventures. In 2007, they retired from the corporate world to pursue the dream of sailing around the world. At that time, they decided BioTrek, their 47-foot catamaran, would be an ideal candidate for a new type of hybrid propulsion system that replaced conventional twin diesels with a pair of electric motors powered by both a battery bank and a single house generator.

THE HELM display screen shows current battery status and power consumption. Next, Caouette plans to add a joystick control system.

A number of manufacturers experimented with similar power configurations — often with less than ideal results. BioTrek also had its share of problems, Caouette says. But rather than turn his back on the diesel-hybrid-electric concept, he used the experiences gained during his twoyear voyage to formulate a system that solved the various problems that plagued earlier attempts. "For starters, we didn't try to reinvent the wheel," he says. "With the exception of our proprietary energy management computer software, everything is off-the-shelf technology that is well-proven in other industries." Unlike some who have been lured into the field with visions of fantastic gains in operating efficiency and performance enhancements, Caouette is well aware of both the advantages and limitations of hybrid power.

For example, at displacement speeds, Watt Power now delivers about 10 percent more speed and four times the range as when powered by its original diesel engines. Taken alone and out of context, this fact would make a sensational sound bite. But it's not the full story.

The engines removed from Watt Power were vintage 210 hp Cat 3208s. These normally aspirated engines are far less efficient a low speeds than modern common rail diesels. In fact, as Caouette is the first to point out, upgrading to a pair of state-of-the-art electronic diesels would provide efficiencies similar to his hybrid power system.

"A common rail diesel, geared properly and mated to the appropriate prop, is still the most efficient way to get someplace fast," Caouette acknowledges. "At higher speeds, the diesel is operating at peak efficiency." In addition, a proportionately smaller diesel working at peak load is also a very efficient way to move a trawler-style boat at displacement speeds.

So why add the complications and expense of a hybrid system when modern diesels present the most efficient and cost-effective solution for two of the more common cruising scenarios? Because boats aren't always operated at these optimum power-to-speed intersections, Caouette says, and for reasons beyond simple fuel economy.

A common rail diesel has a broader optimum range than older engines, but efficiency still falls off at lower rpm, Caouette explains. Because hydrodynamic drag is significantly less at low speeds, miles per gallon will naturally increase at lower speeds, but this increase masks the fact that the engine is not actually delivering all the available energy the fuel could provide. In simplest terms, a properly designed hybrid system can capture and store a greater portion of a diesel's available energy by always allowing the engine to operate at optimum load, regardless of boat speed. Because electric engines deliver 100 percent torque at all rpm, the props obtain a better "bite" at low speeds, which further contributes to overall efficiency. With a properly designed system, the gains in efficiency realized by optimizing diesel performance will more than offset the proportionately smaller losses created by wiring resistance and the conversions between mechanical and electrical energy.

One scenario where Caouette felt a diesel/hybrid/ electric system would show significant advantages is aboard a semi-displacement cruiser. This type of boat is typically operated across a broader speed range, often requiring diesels to run at less than optimum load.

The Watt Power project was undertaken as proof of concept for various hybrid solutions ReGen Nautic plans to bring to market. Initially, only one of the boat's two original diesels was removed. A powerful electric motor was added to the shaft and a generator based off a Volvo D3 engine was added. As compared to a typical on-board genset found aboard a 40-footer, this powerful unit is up to 70 percent more efficient because it is always operated at peak load. It is capable of producing up to 100 kW of power, and any excess power not needed for the drive engines is shunted into the battery bank, where it can be retrieved later for either propulsion or on-board electrical needs.

An enlarged battery bank, the boat's house generator and a 15 kW inverter were also tied into the equation. The task of controlling and of cycling each item on and off was put under the control of a proprietary energy management computer or ECM. After a round of tests and trials, Watt Power's remaining diesel was removed and a second electric motor added to the shaft. The diesel generator is used to keep the battery bank charged and provide extra power when needed in this configuration.

On-board power supply is the second area where Caouette sees potential advantages for hybrid systems. These advantages would be fairly modest on smaller boats such as Watt Power but more significant on larger yachts, which typicallyrun generators when at anchor or when moored to docks lacking sufficient power supplies. A 100-foot motoryacht, for example, might have a 12-liter diesel generator running around the clock, even when power requirements dip well below its rated capacity.

In addition, there are advantages to hybrid power that go beyond pure economics. By replacing the original engines on Watt Power with the current hybrid system, Caouette says he lightened the boat by more than 2,000 pounds. The new system also occupies
far less space in the engine room. With just one diesel instead of three, service requirements are reduced accordingly, and the electric engines are almost maintenance-free to the 100,000-hour mark.

There's also a lot to be said for easing out of the slip in near silence with no exhaust fumes drifting down on neighboring vessels and for being able to make short trips such as harbor tours or dock swaps without starting the engines.

How It Works

Watt Power is currently fitted with a system Pierre Caouette, CEO of ReGen Nautic, refers to as a serial hybrid configuration. The original diesel engines have been replaced with a pair of electrical motors producing up to 300 hp, a Volvo D3 diesel that powers a 100 kW DC generator and a 33 kW per hour, 360-volt battery bank.

The battery bank alone can move the boat at idle speeds for several hours or at a hull speed of about 7 knots for 60 minutes. At that point, the generator starts, warms up, then engages to recharge the batteries. While running, the generator is operating at optimum load, which results in increased efficiencies.

Pierre Caouette is an entrepreneur, computer programmer, commercial pilot and Olympic-class sailor with a long history of success in hightech industries, including computer software and the medical field. In 2008, he and Lisa McKerracher — herself an accomplished sailor and former biotech CEO — established ReGen Nautic to develop hybrid/diesel/electric propulsion and power supply systems for the powerboat market.

The ECM used to control the engines and generator can also be tied to a bow thruster to allow for fly-by-wire maneuvering. Currently, Caouette says he is working on a joystick system for Watt Power that would have similar application aboard any single or twinscrew diesel/electric hybrid.

ReGen Nautic uses CAN (controllerarea network) bus technology, which greatly simplifies the installation and upkeep of on-board electrical systems. "The system architecture is designed to accept future upgrades, and we spent a lot of time figuring the safety
aspects of the system," Caouette says. "We've had a lot of discussion with the [American Boat and Yacht Counsel]. They haven't created any meaningful standards yet, but they felt we were going in the right direction."

Watt Power is fitted with Odyssey batteries wired-in series to create a 360-volt bank with a 33 kW per hour capacity. This battery bank represents a significant portion of the overall cost of the system, Caouette says. He adds that the cost of both motors and batteries has come down in the past year, and he expects to see reductions as the automotive industry puts more emphasis on electric drives.

Currently, a diesel/hybrid/electric retrofit such as that performed on Watt Power would run somewhere in the neighborhood of $80,000. Other projects might cost more or less, depending on what is replaced or added and how the system is configured. In general, the cost of any such system is likely to come down significantly in the next few years. Caouette is currently involved with a number of builders who are converting to this technology.

Is the hybrid powerboat the way of the future? In some cases, probably not. But as innovative technologies such as those being pioneered at ReGen Nautic become more widely understood and accepted, there's a good chance that aboard some boats, diesels may one day share the engine room with electric drives and substantial battery banks.