The silent engine on the GreenWave allows boaters to hear lapping water and rustling wind.

Sailors like to talk about the subtle joy of their boats’ interaction with the sea — the lapping waves, the rustling wind and the sound of the wake. For many, those simple sounds are reason enough to choose a sailboat over a motorboat. But now the quiet of wind propulsion is available in some powerboats.

One step is the trend toward quieter traditional engines, which coincidentally tend to emit less air and water pollution. But a much more important green breakthrough is the replacement of diesel or gasoline-powered engines with electric motors — and an increasing number of manufacturers are moving in this direction.

The GreenWave 515 ESR electric motorboat is designed for those looking for low-impact waterborne transportation that allows passengers to hear the lapping of the waves. It’s built by Gaptec AB, a boatmaker in the Swedish city of Västervik. In the 1990s, Gaptec began making electric-powered rowboats that found a market in tourist rentals, where they became popular because they were cheap to run, but more importantly because they could be used without causing noise pollution in lakes and other environmentally sensitive areas. The positive experience gained with these rowboats led to the development of a prototype for a larger electric motorboat.

Not a drop of fuel

The GreenWave 515 ESR is a relatively small boat — 5.15 meters in length, 1.67 meters in the beam and weighing about 400 kg. Intended to be used for relaxation, nature outings and fishing, it’s built in the traditional fashion using reinforced fiberglass, with an environmentally adapted technology hidden under the aft deck and in the sailboat-like hull design.

“This boat is powered by a Torqeedo outboard motor generating 4 kW,” says designer Arne Åkerman, “This is about equivalent to a 10 horsepower petrol engine, and it will cruise at a speed of 4 to 5 knots.” The range is about 25 to 30 nautical miles (about 45 to 55 kilometers), which is roughly the distance a hiker can cover on foot in six to seven hours.

The outboard motor is folded down into a cabinet in the aft deck, and includes a battery and a battery charger. The motor and the battery are monitored by dashboard instruments displaying  speed, power consumption and operating time remaining on the current charge. “With a single passenger, the boat can reach as much as 7 knots, but then the battery doesn’t last very long,” Åkerman says. A full charge takes 12 to 14 hours. Counting the cost of charging and changing batteries, operating costs are just a few pennies per nautical mile.

Sunroof charger

With solar cells on its roof, the GreenWave boat is self-charging.

The GreenWave 515 ERS can be equipped with a fixed roof fitted with solar cells to make a self-charging boat. It takes about five days to recharge their batteries using the solar cells, providing three to four hours of operating time.

Published in January 2011