HYBRID DRIVES
Retrofitting a marine hybrid drive system can offer quiet motoring, precision docking and regeneration under sail. Jake Kavanagh explains
Leisure marine engines are generally used so little that they tend to corrode out rather than wear out, so until recently there has been little incentive to retrofit a hybrid installation. Prices remain high and deep-cycle lithium batteries are equally expensive, so most boaters stick with what they’ve got.
But things are changing as more production boatbuilders begin fitting hybrids as options, and the manufacturers of the internal combustion engine see hybrid–or even full-electric–as the future.
Economies of scale in the automotive sector are also bringing prices down, and increasing numbers of boaters have come to enjoy the benefits of silent electric cruising. The large battery banks required also replaces the need to run generators overnight at anchor.
Here are some of the most promising advances for retrofit, as seen by PBO at recent boat shows.
1 Multi-fuel hybrid
If you’re looking for a replacement for a small marine engine, Berlin-based Arens has developed a 379cc two-cylinder 11kW (14.3hp) hybrid that can switch between fuels. In development for eight years, the Arens Syprop can be used in several modes, namely thermal, pure electric, as a 4kW generator, a hydro-regenerator and a booster. In booster mode, both internal combustion engine (ICE) and electric drives are combined to deliver 16kW/20.8hp of peak output. The thermal engine is a twin ‘Boxer’ design configured to run on either gasoline or methanol with a seamless electronic switchover. The electric motor is connected directly to the shaft by a belt to reduce noise and vibration and there is no gearbox. Reverse is selected by the e-drive spinning backwards.
Aimed at smaller sailboats, the Syprop weighs 65kg (143lb) and basic maintenance is only required every 500 hours/5 years.
Arens is currently producing about 30 units a year, averaging €15,000 each, but is looking to increase production.
2 Gearbox hybrid
Mounting an electric motor between
