Renewable energy finally sails off into the past

Being a Scottish sailor in the 1960's and 70's, I had more than a passing interest in fine looking ships, fine looking women especially in miniskirts, and the pursuit of propulsion power.

For those into trivia, 100 years earlier, one of the fastest clipper ships of the time was the 85m Cutty Sark, built in the Denny shipyard, my hometown of Dumbarton, Scotland

Cutty Sark was a term expressed by Robert Burns in his poem "Tam O' Shanter" where the heavy drinker Tam on his horse Maggie on the way home in the dark was pursued by a young witch Nannie with a "Cutty Sark" – a short skirt or mini skirt.

A statue of the topless young witch has pride of place on the Cutty Sark bowsprit in Greenwich London. This spectacular ship was built for speed and while she achieved 17.5 knots in a 24-hour period with a very favourable wind, her fastest record of 73 days from Sydney to London only represented 7.5 knots on average, carrying 900 tonnes of wool. Ask any long-distance sailor if 7.5 knots is impressive and they will tell you yes! On the Cutty Sark itself, for visitors there are computer stations where you can actually simulate sailing the ship from Sydney to London, on a screen with differing wind speeds and directions.

People ask me if solar panels could boost the speed of a sailing ship, the answer is yes, but only marginally. If the sun was shining and no wind was blowing, a solar panel array of 120m2 (hard to fit on a sailing ship superstructure) could generate 20kW and push a fine hull like the Cutty Sark at 4 knots, whereas her 3,000m2 sail area would achieve 17.5 knots in a strong breeze. So perhaps solar could reduce the 73 days record to 71 or 70 at best if a minimum speed was attained during the doldrums.

But the industrial revolution in terms of ship design, driven largely by the Scots with coal fired steam propulsion via paddles on wooden ships, then propellors, then steel ships became competitive by 1850 and started the decimation of sailing ships by larger vessels on scheduled routes, to more and more destinations globally.

The last commercial sailing ship, the Pamir, was commercially uncompetitive by 1949.

In the warship scenario, UK ruled the waves with the world's largest navy with an all-sailing vessel fleet. They were around 38 years slower than commercial vessel operators, to adapt to steam powered propulsion in the late 1800's, having to reluctantly admit that it was the way of the future. The Navy's role in protecting the burgeoning commercial fleet and ports in a widespread empire was a key element in their decision making.

With hundreds of other sailing enthusiasts, I attended the Wind Propulsion of Commercial Vessels symposium in London in1980 where one bright idea was large helium box kites raised to 2-3,000 metres, catching higher winds and connected to a small wire winch on the ship's bow. While it may have been a hazard to low flying aircraft, hang gliders and bird life, it never took off despite promising trials.

Even the Duke of Edinburgh, a keen and experience naval officer, who gave the keynote speech at the symposium, encouraged the assembled multitude in their endeavours.

At the same symposium, I was impressed by an aviator, Jack Manners-Spencer, who developed a fully battened "Galant Rig" on a 45 foot freedom ketch with free standing masts and who convinced me and another marine industry tragic to venture down to Southampton and do a trial on the Solent. He impressively showed us how to hoist and trim these sails, let go the moorings and exit out of a marina with only one hand, the other holding a glass of scotch for the whole exercise. Despite this magnificent display (and a scotch or 2), this design did not attract industry manufacturers.

The fact is that wind propulsion of commercial vessels has been and continues to be, investigated for ships. You will see a variety of ships with rigid sails, Flettner rotational masts and sails with solar panels, the best reported to be reducing emissions by 10% over the total voyage. None of these solutions are yet commercially realistic for production designs, but they do tick the box for the company's corporate image in window dressing, striving towards the hallowed zero emissions.