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An offshore wind farm. Turbine towers are usually 700 metres apart with the lowest part of the rotor blade 22 metres above mean high water. Reckon on the wind losing as much as 10% of its force downwind, with each tower creating a wind shadow of at least 150 metres (the diameter of the average rotor). Picture by courtesy of Sandia National Laboratories (www.sandia.org)
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As if there aren't already enough hazards out there, a new and increasing obstacle we're all going to face is rows of towers rising out of the sea like a plantation of giant fly-catchers. Like them or not, wind farms are here to stay - and perhaps we should all be thankful that technology is at least trying to be clean and non-polluting, even if it does drive mariners crazy trying to deal with these huge offshore hair-dryers.
There aren't many offshore wind farms round Britain yet. Just three are operating but another 26 are planned - in the East Irish Sea, the Greater Wash and clustered into the Thames Estuary - with further individual sites all round the country to cope with energy needs of the future.
So far, offshore wind farms are not designated no-go areas. Both the RYA and the Coastguard Agency have held out strongly against restrictions, so that leisure cruising, racing and other navigational freedoms are not affected.
But wind farms are a hazard and they do need care in negotiating them. Basically you have three options: avoid, skirt around, or pick your way through. Whichever you choose is probably a matter of common sense. But the sea is a fickle mistress and it's as well to know what you're up against.
“Avoid” is certainly a good policy. Remember your caution about being pushed by the tide onto channel marker buoys? You can multiply that several times over in a wind farm. Depth is also something you ought to watch. So far the tendency is to build farms fairly close to shore. That means shoal water and some tricky manoeuvring around at low tide. Do you really need those kinds of headache?
“Skirt around” seems easy enough, though be aware that those rows of towers can play tricks. Even quite big vessels can apparently disappear from view as several towers line up together on your approach. Radar too, isn't always happy. You can see the obstacles from a distance right enough, but shadows and echoes often creep in as you approach, creating a smear across the display or simply reading gibberish. At night there's a further concern - landmarks that appear to come and go as invisible pylons edge between you and your target.
“Pick your way through” is an adventure you may wish not to contemplate - certainly if your craft is of any size. To small boats, meaning dinghy-size and below, there's plenty of space to move around as long as you watch what you're doing. Those pylons though are very solid and International Regulations for the Prevention of Collisions at Sea most certainly apply.
By convention, offshore wind farms round UK are being built with the towers ranged at 700 metres apart or more. That's not a lot of space allowing for tide and wind, so getting through is probably best handled under power. Whatever you do, watch your height. At its fullest extent, from water level to the tip of the topmost rotor blade, a pylon might reach as high as 150 metres.
The worry though, is the extent of the lowest blade. English ones are supposed to be 22 metres above the highest high water, plus allowing for springs. That should be enough to allow for most UK-based yachts, but don't count on it. And keep your head down if your craft is taller than average. Being dismasted does tend to mess up a nice cruise.
Deep water farms are not necessarily safer. Don't forget, these things are producing electricity, so somewhere there are submarine cables for getting that power back to shore - high tension, high voltage and quite capable of doing you and your crew a nasty mischief. Be careful!
Keep your charts up to date too. Both wind farms and their undersea cables should be clearly marked, including those under construction. Watch out for these - while there are no restrictions on sailing through an operational wind farm, there very well might be while they're being built.
Above all, keep a good lookout. Yes, pylons are numbered and carry lights at night. But they're fixed obstructions as solid as any rock. They're private property too - so while you can sail through them, don't try to land on one - it's VERY dangerous. Anyway, the lower sections are covered in marine growth and there's nowhere you can go once you've landed.
Which makes wind farms exactly like every other marine challenge to be faced out there. They're safe enough, as long as you don't take chances.
