Some people have trouble thinking of a megayacht as an eco-friendly vessel, which is understandable. Fuel and freshwater capacities are measured in the thousands, if not tens of thousands, of gallons. Some yachts devote entire refrigerators to keeping fresh flowers, and most maintain enough food stocks to feed a charter party of 12 for up to a week. But despite all this, many megayacht builders and designers are looking for ways to reduce the impact of the vessels they build and refit by recognizing that in the world of big yachts, small changes can go a long way.
For instance, Feadship has taken a series of steps to reduce the electricity consumed by marine air conditioning, a yacht’s largest energy drain as it runs 24 hours per day. One way is to apply a heat-reflective glaze to the hull and another is by combining recirculated indoor air and precooling outdoor air both with the goal of reducing the air conditioning systems cooling load. Yet another is using heat produced by propulsion and generator engines to heat water for domestic use, including an onboard pool.
Other builders are concentrating on new hullforms to improve efficiency. One, Hong Kong-based Kingship, laid the keel of its new 44-meter (144-foot) Green Voyager line (above) at the end of March. The naval architecture firm Axis Group designed the hull with a plumb bow that maximizes waterline length and therefore reduces hydrodynamic drag, resulting in a claimed 20-percent reduction in fuel consumption, compared to a conventional hull. The main saloon will feature windows that open to the full height of the deck to reduce the need for air conditioning. But the greenest feature onboard the Green Voyager won’t be visible. Siemens’ hybrid propulsion system was chosen for its low energy consumption, clean operation, and relatively small size. Similar to a hybrid car, it will store 600-kWH of energy in compact lithium batteries, allowing the Green Voyager to be propelled by diesel-electric or electric only, as well as straight diesel power.
Another innovator is sailboat-builder Perini Navi, which launched its first motoryacht last year, the 50-meter (164-foot) Exuma (right). The Picchiotti Vitruvius-branded yacht employs a weight-saving all-aluminum hull that mimics the slippery lines and outstanding efficiency of a sailing vessel’s. Exuma was awarded the first Rina Green Plus Platinum designation based on her efficiency, exhaust emissions, and advanced black- and grey-water-treatment technology. She will have a range of 5,500 miles at 12 knots (13.5 mph) and carry a 12-foot hovercraft in her bow.
By paying attention to details like waste-water treatment and air conditioning systems, shipyards are today making older yachts greener without compromising comfort or amenities. And new yachts are increasingly enjoying significantly better fuel efficiency thanks to advanced hull designs and weight-saving construction techniques.
This article originally appeared in the April 2011 issue of Power & Motoryacht magazine.