The wing sail system
At the heart of the "Aera" concept is a 35 metre high wing sail with a surface area of 245 square metres. Unlike conventional sail systems, the wing sail developed by Rondal, a Huisman subsidiary, requires no shrouds, sheets, blocks, winches or furlers. The sail can rotate 360 degrees and is driven by two electric motors housed in the mast base. The flaps on the trailing edge of the wing, which can be adjusted up to 30 degrees, are to be controlled by hydraulic cylinders, a technology that was invented and further developed for the America's Cup.
Dr Iain Percy, CEO and founder of Artemis Technologies - a spin-off of the America's Cup project Artemis Racing - was in charge of the development. Percy is an Olympic champion in the Finn Dinghy (2008) and Starboat (2008) as well as a silver medallist in the Starboat (2012) and multiple world champion. He is also a veteran of four America's Cup challenges. "A few years ago, Royal Huisman and Rondal's innovation department contacted us about the possibility of using wing sails on sailing yachts to reduce their emissions," says Percy.
A wing-sail prototype for cruising sailboats was developed. The eight-metre wing was tested for more than two years on a 22-foot keelboat in the shipyard facilities in Vollenhove, Netherlands. It was left in place around the clock in all conditions to observe whether it would ensure the safety of the boat below even in strong winds.
The 35 metre high wing sail that is to propel "Aera" is a distant relative of the sail on America's Cup boats. Unlike these, however, the wing has no stays or sheets. Preliminary performance calculations (VPP) predict that the optimum wind speed will be 15 knots and that an upwind angle of 45 degrees can be achieved. The cruising speed should be 12 knots and the maximum speed 14 knots.
The front part of the wing will be made of a thin-walled carbon fibre structure, while the rear flaps will be made of carbon fibre and Mylar film. The trim of the wing is to be computer-controlled. It would be possible to switch to sailing mode in just one minute. When not sailing, for example in a harbour, the flaps are centred and the Wing-Sail should align itself neutrally in the direction of the wind. The wing is said to be up to 60 per cent more efficient than triangular sails; a traditional rig would require 40 to 60 per cent more surface area to deliver the same performance.
The Wing-Sail can be tilted into a horizontal position for passing bridges, in rare extreme weather conditions or during dock periods.
A similar rig philosophy, the Solid Sail, but implemented in a significantly different way, is to be realised on the "Orient Express Corinthian" are created.
The energy systems
"Aera" is designed to combine several energy sources for virtually emission-free operation. Much of the environmental impact of a yacht of this size comes from running the domestic or hotel loads, such as air conditioning, pool heating and similar systems, while sailing or at anchor. Royal Huisman has designed the yacht so that the hotel load is powered by a battery storage bank powered by the latest hydro generators from Rondal or by hydrogen fuel cells. A 580 kWh battery system can supply the yacht's entire "hotel operation" for eleven hours. While sailing, four retractable hydrogen generators from Rondal, each with an output of 15 kW, will continuously recharge the batteries. In anchor mode, a 60 kW hydrogen fuel cell will take over the energy supply. Three 62 kg hydrogen tanks under 500 bar pressure would provide enough energy for 72 hours of emission-free operation.
For longer engine journeys, "Aera" will have two variable Volvo D13-700 generators equipped with "HVO" (Hydrotreated Vegetable Oil) could be used. This biofuel could reduce CO₂ emissions by up to 89 per cent, particulate emissions by 40 to 80 per cent and NOx emissions by 8 per cent compared to fossil diesel. In this mode, propulsion would be provided by two swivelling, retractable 500 kW electric motors, the same technology that Royal Huisman already uses for the 60-metre-long "Sarissa" has deployed.
The innovative design
The design of "Aera" was created by Cor D. Rover, who developed an asymmetrical layout on two decks with his team. With a width of 14.5 metres, the catamaran offers an impressive 670 square metres of deck space over its 50 metre length - comparable to a 65 to 70 metre motor yacht. The yacht can accommodate ten guests and seven crew members. The owner's suite is located on the main deck with over 44 square metres of interior space and a private 153 square metre outdoor deck with pool and covered massage cabana. There are also four guest cabins. Other features include a second glass-bottomed pool at the stern of the main deck, multiple indoor and outdoor dining areas and outdoor lounges on each deck.
A key objective in the development of "Aera" was to make sailing more accessible. "We know from research that sailing yachts often do not sail under full sail, especially for short distances between harbours," explains Jan Timmerman, CEO of Royal Huisman. "For some sailing yachts, setting and adjusting all the sails can take half an hour or more. In addition, the yacht needs an experienced sailing crew and an interior team to secure furniture and other items. For a short trip to the next bay, sailing often doesn't seem worthwhile."
With "Aera" it could be different: "While the anchor is raised, the captain enters the target, sets the wing to automatic trim, the wing sail reacts, and you are sailing in less than a minute. Without the challenge of operating a conventional sail system, without rigging, blocks, winches and sail tracks, booms swinging overhead, or furlers, sheets and sails. It's basically as simple as operating a motor yacht," says Timmerman.
