For several years, marine designers and operators have honed a vision of a future that is less dependent on fossil fuels. Vessels have entered service in commercial operations based on the use of “green” power — including solar collectors married to batteries.
While all-solar vessels have been envisioned by some, currently the sun’s power is mostly harnessed to supplement conventional auxiliary power sources of electricity. Examples include Royal Caribbean Cruises’ installation on several cruise ships of smaller systems, increasingly common on smaller commercial ships, that can provide useful auxiliary power particularly when docked or at anchor.
Hornblower Hybrid, a New York excursion boat, uses power generated by two 10-foot-tall twisted Savonius wind turbines and a photovoltaic solar array covering the awning on the top deck. That power is converted and stored in batteries, which power the navigation equipment, lighting and electronics on board.
Hornblower Cruises, based in San Francisco, previously introduced Hornblower Hybrid Alcatraz, which is still referred to as the company’s “environmental flagship.” The 64-foot ferry has solar panels installed on its roof. The 120-foot Alcatraz Clipper Hybrid and Alcatraz Flyer Hybrid both now feature a solar aspect; each has 126 SunPower panels that generate 40 kW to power lights, displays and audio systems.
The research vessel Spirit of the Sound, recently commissioned by the Maritime Aquarium at Norwalk, Conn., features a hybrid diesel-electric propulsion system, aided by solar panels topside. Robert Kunkel, president of Alternative Marine Technologies (AmTech), designer of the vessel, said Spirit of the Sound uses two solar panels to charge the emergency 24-volt direct-current circuits. That innovation allows the vessel to remain idle at its berth without shore power and still have the capability to run bilge pumps, navigation lights and emergency circuits.
Supplemental power has been of interest aboard power-hungry cruise ships. For example, Oasis of the Seas, operated by Royal Caribbean, benefits from some 21,000 square feet of thin-film solar collectors on deck 19. They can deliver enough power to light the ship’s Royal Promenade and Central Park areas. The company had previously installed similar capabilities on two of its Celebrity Solstice-class ships.
Royal Caribbean spokeswoman Tavia Robb said Celebrity Solstice was the industry’s first ship to use solar energy, with 216 solar panels spread throughout five areas of the ship that can generate enough power to operate approximately 7,000 LED lights. Celebrity Solstice, Celebrity Equinox and Celebrity Eclipse utilize two types of solar panel technology: solar foils glued on various free deck areas and glass solar panels that have been installed in glass structures, such as the ceilings of the solarium and atrium. Due to glass solar panels’ superior viability in marine environments, these panels have subsequently been installed on Celebrity Silhouette and Celebrity Reflection.
Solar panels aboard the Maritime Aquarium at Norwalk’s new research vessel Spirit of the Sound.
“Royal Caribbean International’s Oasis of the Seas and Allure of the Seas each have solar panels but there are fewer panels on those ships than on the Celebrity ships,” Robb added.
Internationally, the picture for solar has been even brighter, most notably demonstrated by the world-girdling cruise of the research vessel MS Tûranor PlanetSolar, which easily claims the title of the largest solar-powered vessel in the world. Last year, after circumnavigating the world — a first for a solar vessel — it visited U.S. ports on the East Coast prior to returning to Europe. The vessel, registered in Switzerland by Geneva University, was designed by LOMOcean Design and built by Knierim Yachtbau in Kiel, Germany. The roughly 85-ton, 100-foot double-hulled boat is covered by 5,800 square feet of solar panels capable of producing 93 kW. For those times when the sun is not available, 8.5 tons of lithium batteries can power the electric propulsion motors and other onboard equipment. For comparison, the battery packs in a Toyota Prius hybrid automobile weigh about 100 pounds, making the capacity of the Tûranor several hundred times greater.
While solar energy may not provide the main power source for most vessels anytime soon, its economics provide an opportunity for entrepreneurs and designers to do more with less. While Kunkel said from a propulsion perspective his company focuses mostly on projects with liquefied natural gas (LNG) and hybrid battery applications, solar is part of the mix. “Given the enormous power requirements of most vessels relative to the amount of energy that can be gathered by solar panels, the use of solar has been limited to auxiliary power issues,” Kunkel said.
“However, with every passing regulation, whether it be ballast water treatment systems, scrubbers or exhaust gas recirculation to solve emissions problems, a parasitic load is associated with those changes,” he explained. “We have been looking toward solar power to cover those loads rather than taxing the vessel generators with the additional power requirements. We have also looked to solar power to provide charging capability to the vessel’s emergency power systems — whether that be a charging circuit for a 24-volt emergency system or power to support citadel requirements or emergency navigation aids.”
For smaller vessels, solar presents an opportunity to cover modest ongoing auxiliary loads, said Bruce Schwab, owner and president of OceanPlanet Energy, a company based in Maine that focuses on marine energy efficiency, including solar. However, a limited number of surfaces can realistically be reserved for solar collectors. Schwab emphasizes the importance of combining solar with improved efficiency, such as smaller and more efficient refrigeration equipment.
“We do get occasional inquiries from people trying to build solar-powered tour boats but the amount of solar required is enormous,” Schwab said. He said “every bit helps” and there is nothing wrong with solar per se, but it is most meaningful in conjunction with efficiency efforts.
Considering the general trajectory of solar power, dreams of “pure” solar-powered vessels are, for the most part, merely dreams, said Darren Hammell, co-founder and chief strategic officer of New Jersey-based Princeton Power Systems, a manufacturer of technology products and embedded software for energy management, micro-grid operations and electric vehicle charging. However, said Hammell, even with falling petroleum prices, the role of solar should grow.
“We have seen a dramatic decrease in the price of solar arrays over the past several years. We are now at the point where even if oil prices were at a price as low as $30 per barrel, the economics of solar will remain compelling,” he said.
“Solar may not be able to power the majority of systems but it can power segments of systems or specific applications in a really cost-effective way,” he added.