The name gives you a hint: the Silent 79 Yacht isn’t powered by a noisy combustion engine. Instead, the 79-foot vessel has an array of 70 photovoltaic panels that provide the power for the onboard and propulsion systems. A bank of lithium-ion batteries stores energy for cloudy days and a generator provides emergency backup. Otherwise, it’s a fairly standard affair, with plenty of deck space on the perimeter — the solar panels provide shade in the center — and configurations ranging from four to six bedrooms. Set to launch in 2020, two of them are already spoken for, with a third still seeking an owner.