Back to the future? Solar and wind sails for cargo ships

Solar sails on tanker - the concept SW

Solar sails in action - already operating in Hong Kong © SW

The equipment is likely to be similar - but on a more massive scale - to the zero-emission systems the company has installed on four dual-fuel passenger ferries operated by the Hong Kong Jockey Club.

'Solar Albatross' (pictured left) is a 24 meter 100 passenger carrying catamaran ferry with its stow-able SolarSails.

The boat service is between the Hong Kong Jockey Club's Kai Sai Chau Golf Club, ferrying golf club patrons to and from their three island based 18 hole courses off Hong Kong Island.

For the Sydney, Australia based company, the hybrid boat was the first with sails embedded with solar cells to collect the sun's energy and use wind power too. The SolarSails stow flat on the roof of the boat when not in use, although they continue to collect solar energy from the sun and store it in batteries in the two hulls of the catamaran.

The sails are engineered and approved by DNV for 44 knots of apparent wind with a 100% safety factor. The sails can be feathered or lowered into a headwind. In early trials when 'sailing' in a 15 knot true wind at 45 degrees off the bow give a 1.8knot increase in boat speed from 14.2 to 16 knots with no increase in engine rpm

Solar Sailor Holdings chief executive Robert Dane said talks were under way with an Australian mining giant which planned to buy a fleet of ultra-large Capesize bulk ore carriers, to be equipped similarly.

He declined to name the company, pointing out the issue was 'very sensitive', but Solar Sailor is already working on initial development work to install its equipment on new ships as well as retrofitting existing vessels.

He estimated it would cost A$7 million (HK$58 million) to install solar-panel-equipped sails on the bulk carrier but that the owner would save that amount on fuel in just two years.
Electric power from the solar cells would augment power from the diesel engines, while the sail would harness the wind to provide additional thrust that would allow the ship owner to reduce engine power.

Each sail, which could be lowered to fold along the side of the ship to allow cargo to be loaded and unloaded, would cover 800 square metres. This is 25 times the area of each of the sails used on the Solar Albatross, one of four similar passenger ferries Solar Sailor has now built for the Jockey Club.

However, Solar Albatross is the only one of the four vessels that has solar-equipped sails, which can be angled to the sun and wind direction. The three other ferries have solar cells mounted on the roof.

He said initial estimates showed that the four ferries, which can carry up to 100 people each, had cut the Jockey Club's fuels costs by half. Dane said the ferries would be monitored over the next year to assess the actual fuel savings.

Electric power from the solar cells is used for the five minutes when the ferries are arriving and departing Sai Kung and Kau Sai Chau, while the diesel engine is started for the 15-minute cruise.

Dane said the ferries can operate at six knots using electric power and 16 knots using diesel.

The diesel engine consumed about 10 litres of oil an hour. 'With solar power we can reduce that by a couple of litres. For us that's the critical thing - the fuel savings,' he said.

On their latest project, Dr Dane said by augmenting the cargo ship's diesel engines, the technology could save 20 to 40 per cent of fuel costs and pay for itself in as little as two years.

The trial, which would initially involve only one sail being fitted to one ship, will determine whether the technology could then be rolled out on a larger scale throughout the company's fleet.

SolarSail envisages several huge sails of 850 square metres each fitted to each carrier. The sails, which would cost about $7 million, could be folded away during loading and unloading.