January 25th 2010

"The performance and prospects for Offshore Wind Power"

                             given by Prof. Peter Tavner
                   Head of Engineering and Computer Sciences,                                        University of Durham

Peter called upon audience participation early in his talk when he took a straw poll on who was 'for' and 'against' wind power. Much as expected the good number of attendees produced a mixed vote; those 'for' being the majority but there was a sizeable minority 'against'. Peter then went onto give an excellent and well balanced talk covering in the time aspects from early windmills dating over 2000 years in both China and Persia and right up to the modern and more familiar units such as the 2mw Gamesa wind generators we see today, coining a phrase 'power stations' up a stick!

The use of wind powered windmills dates back years more commonly used then for grinding milling, marsh drainage and paper making as opposed to harnessing power. The first recorded UK mill was at Weedon in Yorkshire in 1185. It was the Danish pioneer Paul la Cour in 1885 that began to take the wind power seriously in terms of looking at and developing interest in this reusable free resource. After his successful experiments interest soon spread around the world; in 1887 Charles Brush began a couple of decades of development of wind turbine power for the generation of electricity.

To date Danish engineers and entrepreneurs, through such organisations as Vestas, have continued to develop their designs; 1958 when they conceived the original 200kw 3 bladed upwind turbine, which has become a benchmark in the trade.

In the 1980 era California developed and assembled a number of such turbines to form what has become known as wind farm technology to pump oil, which leads onto today's modern turbines - wind farm technology. Development has spawned individual units and wind farms that utilise turbine types that have variable pitch blades to enable energy to be extracted at lower wind speeds and sophisticated disengaging mechanisms if the winds speeds get too high or are highly turbulent. Typically these operate at 690v with fixed speed or variable speed with a wound rotor generator.

More complex turbines offer pitch regulation variable speed direct or geared drive units that can provide a complex array of power generation. It was also noted that the height of the units has increased over the development period where it has been proven that lower ground level airs are more affected by turbulent air reducing their efficiency.

The blades extract energy by the aerodynamic lift action of the wind flowing over them. A lot of work has been put in over the last couple of decades trying to establish the optimum blade configuration. It has been shown that for a windmill in a constant windspeed the power generated is proportional to the effective cross sectional area swept out by the blades and the cube of the windspeed.

Worldwide development continues apace with figures of 8gw of energy being provided in Europe last year from wind turbines. This is equivalent to 4 fossil powered fuel stations. The UK has just approved round 3 in January 2010. Big gains have been made in operating efficiency with best results of 27.5% onshore and up to 29.5% offshore in exposed locations. Yes capital costs and maintenance are high but this is essential for best efficiency. One of the biggest issues is planning and approval but the move to locate more in coming years off shore in developed farms should enable us to capture more of this free green energy resource. Probabilities of the turbines now being able to generate energy are now much greater than 95% in wind speeds of between 5-15 metres per sec. The turbine will always be seen as a compliment to fossil, but the harnessing of the wind in consideration to the surrounding environment has now to be considered a viable alternative.

Peter concluded his presentation with a vote asking if any of the audiences opinions had been modified in favour of wind turbine technology, to which a few had been converted. It was generally felt as a much better understood viable alternative to fossil fuels as a compliment to our increasing energy needs.

A vote of thanks was proposed by Richard Aldridge and was carried whole heartedly by the audience. There was much discussion after the meeting ended.

David Grint      February 2010