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No matter how good an idea is – even one that could potentially save thousands of lives – it will never leave the drawing board if people can’t, or won’t, be convinced of
its value.
For wave energy expert Professor Stephen Salter, this is a scenario he knows only too well, having spent years trying to push forward his concept, the Salter Sink, that could weaken the destructive power of tropical storms.
Cyclonic storms are fuelled primarily by warm moist air found near the surface of the warm ocean waters over which the storms develop. Hurricanes require waters that are 26°C or warmer to form and, generally, the more heat in the water, and the deeper the warm section extends, the more intense a hurricane will become.
Salter’s novel idea to drain energy from hurricanes and typhoons came about after he witnessed the terrible destruction wrought by hurricane Katrina in the US in 2005. The Salter Sink is a simple, affordable device made from a ring kept afloat by old tyres and a skirt-like tube attached underneath the ring.
The system would be dropped in the Atlantic Ocean along one or more key regions of a “hurricane alley” – a warm corridor through which the most damaging storms tend to pass. According to Salter, to succeed the system would only need to drop the temperature of the surface water by as little as 1-2°C. This would not prevent hurricanes from making landfall but would weaken their destructive power in a bid to save lives and prevent billions of dollars worth of damage.
The Salter Sink works by cooling warm surface waters by mixing them with colder waters from below. There have been previous ideas to use wave-driven pumps to lift deep, cool waters up to the surface as a way to improve ocean fertility and CO2 absorption. However, as the name implies, the Salter Sink works by sinking hot water, rather than lifting cold water.
Salter says: “Like a siphon, it exploits gravity to create a ‘drain’ through which warm surface water flows.”
A large, buoyant ring made from old tyres latched together is attached to a long, skirt-like tube – around 50-100m – whose bottom opens in the cooler depths of the ocean. Salter says: “I wanted a material which would allow flexing to relieve unwanted stress and track the sea surface. Used tyres have a negative cost and last well in sea water.”
Ocean swells overtopping the ring will periodically fill it with warm surface water. Because the water in the ring is above sea level, the force of gravity will drive water out of the bottom of the tube. Over time, the tube will fill with warm surface water, so that the flow will force the warm water down the tube to drain out of the bottom to mix with cooler layers of the ocean below. The tube has a tapered profile to accelerate the velocity of the flow and improve mixing of the warm exhaust water with the colder water at depth.
Around 150-450 of these structures would be needed to be placed permanently along the hurricane corridor, with radar signals used to prevent ships from colliding with them.
Salter presented his idea to the US government in 2007. In 2012, a technology company called Intellectual Ventures backed by Bill Gates patented the idea. This prompted further research, calculations, modelling, and successful testing of the concept with a 1:100-scale tank model.
However, since then progress has been frustratingly slow for Salter owing to a general lack of interest from government. Salter says that, sadly, to regain political support for the idea will mean “waiting for even more expensive hurricane damage or, less probably, more intelligent politicians”.
Salter continues to persist with the idea and says that possibly a consortium of insurance companies could be approached for funding, or even groups concerned about eutrophication and dead spots in the sea.