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SPECIALIST TOOLS


FINDING ‘THE SWEET SPOT’ MOBILE AERIAL WIND PROSPECTING


On the face of it, deciding the position of a wind turbine should be pretty obvious.


Just place it on the top of a well known windy hill, a westerly facing cliff, or anywhere in the North Sea. Lots of wind blows there. Problem solved.


Except that it isn’t. We know this because, it is hard to find any wind farms, anywhere in the world, that produce the expected rated power output and subsequent financial returns that were promised to the banks and governments that funded them. Why is this?


THE DIFFERENCE BETWEEN SUCCESS AND FAILURE


It turns out that the power curve of a modern wind turbine is very steep, which means that the effective profitable wind range can be very small. A reduction in wind speed of 1.5 metres/second from a forecast mean wind speed of 10 metres/ sec reduces the rated output from 54% to just 30%. This can be the difference between profit and loss.


CONSIDERATIONS


Small differences in turbine positioning can make differences to output far greater than 1.5m/sec. On land, just a few


metres extra height may greatly increase output. Other factors include: upwind land formation; trees; lakes; escarpments and buildings. At sea, factors such as proximity to land, prominent land features, adjacent river valleys, and wave height alter wind speed. Just ask any racing yachtsman.


Increasingly important, is wind shading from other wind turbines. None of these factors are accurately enough predicted by existing computer models working from the limited data they get from meteorologists and the occasional Met Mast. Lidar helps a lot, especially on land where it can be set up quite quickly, but it is still an expensive business. At sea, Lidar is frighteningly costly and as static as a Met Mast.


NEW DEVELOPMENT


Now, a new cheap, easy and highly mobile method of wind prospecting has been developed by Allsopp Helikites Ltd. It utilises their patented, small high wind capable tethered Helikite aerostats to carry accurate meteorological sensors up to turbine height and above. This creates an accurate airborne Met-Helikite system.


Wind speed, wind direction, temperature, humidity, altitude and barometric pressure


can be measured with data instantly streamed to the ground if required.


Many meteorologists worldwide have used Helikites to lift sensors to very high altitudes on land and sea. Recent published research in Germany proved that Helikite derived data was very consistent with adjacent Met-Mast data.


Helikites are not normal fair-weather blimps. For years they have been the preferred aerostat for both scientists and the military. They utilise both wind and helium to keep them up. Even small models can fly steadily in winds from 0 to 50mph.


Altitude keeping is also very stable, especially at sea. Uniquely for small aerostats; Met-Helikites can be successfully flown from walking personnel, moving vehicles, small boats or ships. This makes it easy to trail them over hundreds of miles on land or sea whilst they gather enormous amounts of data from whatever altitude the operator desires.


ADVANTAGES


The advantages for wind farm developers are obvious. Wind prospecting can occur over vast areas very rapidly. Met-Helikites can accurately sense where the ‘sweet- spots’ occur, with the highest wind speeds and the lowest turbulence.


Large areas of consistently high winds can be determined which can be used to correctly position large wind farms. Also, small positioning differences can be exploited to enhance the production from a single wind turbine. The amount of data that can be gathered is orders of magnitude greater than any other existing methods - and the cost is minimal.


COSTS


Financing immense sums of money upon inaccurate estimates can be a thing of the past. Using Met-Helikites, wind farm developers can easily afford to prospect for wind extensively and accurately worldwide. This ensures the most efficient build costs and far greater profitability.


Sandy Allsopp


Allsopp Helikites Ltd www.allsopphelikites.com


100


www.windenergynetwork.co.uk


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