Wind propulsion designers wait on shipowner participation
The latest wind power developments are still in the testing stage, and shipowners may choose to take advantage of this renewable energy source via battery hybrids instead, says Wendy Laursen.
“I see small vessels as being the early adopters to break the ground and show everyone that this works,” says Dr Traut. The smaller the ship, the larger the relative savings from applying wind power. Even if multiple units are installed to increase the amount of wind power output, it doesn’t scale proportionally to the propulsion power requirements of large vessels, he says.
The idea that smaller vessels will move first is a familiar one, but, says Charles Moray, managing director of Oceanfoil, it is clear from talking with shipowners that the economic pressure is much greater for the higher tonnage vessels. Moray is in the final stage of negotiations with two shipowners who are offering Singapore-flagged tonnage for trials of his wingsail technology. The vessels under consideration are two 101,000dwt bulk carriers, another twice the size and an oil tanker.
CFD and tank testing has already demonstrated that reductions in fuel consumption of between 15% and 20% are possible, and Mr Moray is finding shipowners increasingly interested in his technology. He is working with researchers from University College London to develop software that will enable shipowners to determine optimal routes based on time of year and the number of days they are willing to spend on the voyage. He is also designing modifications to his system to suit specific vessel requirements, such as the need to have multiple cargo hatches accessed at the same time. This involves wing sails that will fold down, but, says Mr Moray, like the standard system, no crew intervention and no crew training is required for the Oceanfoil system.
Solar Sailor’s solution to the space and accessibility issue on bulk carriers is also to have folding wing sails that open up to double or quadruple the area. The design involves having the masts fold down onto the deck of the vessel where they sit flush with the openings of the cargo hulls. It’s an ideal solution, says the company, as it’s easily retrofitted and does not pose any significant difficulties to cargo handling equipment. All the equipment stows away neatly and effortlessly with minimal or next to no hull penetrations.
“Since sail powered ships followed the trade winds in the past, major shipping ports were established where these trade winds were most powerful,” says Dr Frank Berté, president of Innovative Marine Technology. His Cargoproa design is suited to a range of vessels including container ships. The combination of the Cargoproa and the container vessel turns the coupled vessels into a proa configuration like a canoe and outrigger. The outrigger allows the proa to carry a sail area much larger than the canoe could carry without it. The large sail area provided by the sailing space frame in the Cargoproa design means cargo vessels would not need to run engines for propulsion whilst at sea.
The Cargoproa stays outside the territorial limits near the originating port or the destination port. It couples or decouples from the vessel to be propelled at these locations.
The height of Cargoproa twin masts allow use of wind in the 100-150m elevation range above sea level, where wind velocity is considerably higher than at sea level, and comparable to the wind velocity seen by kite type propulsion schemes. The Cargoproa’s space frame has a rigid structure, with the two masts and a fore spar, which in combination with the triangular deck comprise a tetrahedron. This configuration eliminates the need for stays on the masts. The tall masts allow for sufficient sail area for achieving the thrust forces needed to replace the diesel engines of a container ship.
Cargoproa claims to make the propelled vessel an efficient sailing vessel capable of sailing on a broad reach, a close reach, and downwind (contrary to other wind based propulsion systems). “Coupling the Cargoproa is readily accomplished even when a container ship has turned off the engines and is still rolling or pitching due to ocean waves and wind forces, because the Cargoproa incorporates mechanisms that ensure a safe and controlled coupling process to the vessel to be propelled,” says Dr Berté. “Because of the Cargoproa outrigger, rolling of the container vessel while underway is minimised and this reduces the likelihood of loss of containers from the vessel in high sea and wind conditions. The coupling devices fit between container blocks and attach to simple devices which are fixed to the gunwales of the container vessel.”
Another design, the Vindskip from Terje Lade, is a cross between sailing and flying on water that was inspired by the aerospace industry and sailboat environment where relative wind is a crucial factor in designing aircraft, propellers and sailing boats. “A merchant vessel travelling at an average speed of 17 – 18 knots for example will have a headwind more than 50% of the time, regardless of the course it is taking. This in turn will cause a great drag force from the wind. The wind power system of Vindskip uses this apparent wind and generates a positive force in the longitudinal direction of the ship as a function of the angle of attack,” says Mr Lade.
“For a merchant vessel, turning the negative drag forces from the wind into a positive pull created some design challenges,” he says. “Even though a vessel with a hull shaped like a symmetrical air foil travelling in the relative wind will generate an aerodynamic lift, it does not necessarily follow that the design will generate a positive pull in the ship’s speed direction. The first wind tunnel test we conducted clearly demonstrated this. We had to then look at generating a two-dimensional flow alongside the above-water hull in order to achieve this. Recent wind tunnel tests at Cranfield University, as well as CFD optimisation testing, has helped us to improve the performance where we are now seeing a positive pull in a sector from 18° to 180° apparent wind angle of attack, which is an incredible achievement.” This year Mr Lade will look at performing further CFD optimisation tests for the underwater hull and subsequent tests in a model tank in readiness for potential shipowner participation.
Norsepower is developing an auxiliary wind propulsion solution using a rotor sail, a completely new version of the Flettner rotor. The Norsepower Rotor Sail Solution uses new technology, advanced materials and leading-edge control system to reduce fuel consumption and can be fitted to newbuildings or as a retrofit. A prototype of the Norsepower Rotor Sail has been assembled at the company’s test site in Naantali, Finland, and the prototype will be tested at sea on Bore’s Estraden later this year.
According to Windship Technology in the UK, 40% of the existing bulk carrier is less than five years old. The new generation has around 15% lower fuel consumption and this will leave older vessels less able to compete for charters. The company is developing an auxiliary fixed-wing sail system that it claims could cut fuel consumption by around 30% for retrofits, more for newbuildings. The masts rotate automatically to exploit the power of the prevailing wind and, as the speeds and angles of the wind change, the system develops more power, allowing reductions in engine power to be made. Windship plans to use its Singapore base to build and test a prototype early next year.Tuomas Riski, CEO and partner of Norsepower, says his aim is to be the first company to have an industrially piloted and certified auxiliary wind propulsion product which is delivered as a ready-made solution.
However, there is still scepticism about the use of wind power in the world’s cargo fleet. For DNV GL, the relative unreliability of wind makes it ill-suited for deep sea transport or operations in some latitudes with seasonally variable weather conditions. That is not to say that wind power does not have a place, and DNV GL is positive about the impact that hybrid systems using batteries could have on reducing emissions. In this case, shore-based wind energy systems could be used to charge the batteries.
Electricity can be used to power ships at berth (cold ironing), and to charge batteries for fully electric and hybrid ships. Enhancing the role of electricity on ships will contribute towards improved energy management and fuel efficiency on larger vessels, says DNV GL. For example, shifting from AC to onboard DC grids would allow engines to operate at variable speeds, helping to reduce energy losses. Additional benefits include power redundancy and noise and vibration reduction.
All-electric vessels and hybrid vessels with energy storage in large batteries and optimised power control can give significant reductions in fuel costs, maintenance and emissions, in addition to improved responsiveness, regularity and safety in critical situations. Furthermore it can work as a storage unit for energy harvested from waste energy recovery, regenerative braking of cranes and renewable energy. Additionally batteries can improve effectiveness of gas-fuelled propulsion systems based on LNG or other environmentally friendly fuels.
Electrification has generated strong interest, particularly for ship types with frequent load variations. By around 2030, DNV GL envisages that improvements in energy storage technology will enable some degree of hybridisation for most ships. For large, deep sea vessels, a hybrid architecture will be used for powering auxiliary systems, manoeuvring and port operations to reduce local emissions when in populated areas.
The first Maritime Battery Forum has been established with close to 40 members, among those cargo and vessel owners, yards, vendors, research organisations and DNV GL, all in partnership with Norwegian authorities. Several research and development projects are ongoing, and more are initiated, to address maritime safety and business challenges of adopting batteries in an effective way and to improve the technical framework. Major maritime power system providers, such as ABB, Siemens, Rolls-Royce and Wärtsilä, are all on the front foot preparing different main and auxiliary power solutions.
Several decision support tools are already established such as tentative DNV GL rules for battery power, a DNV GL guideline for large maritime battery systems, a new tool for qualification of battery related systems, a battery ready service (technical, economic and environmental performance analyses), battery sizing and optimisation tools and an introduction course to maritime battery systems, with close to 100 people already participating.
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