1 Historical Development of Wind Turbines Svein Kjetil Haugset, 2007

2 First use of wind - sails In use for 6000 years ”Catching” the wind in a sail Generating a drag force, D –due to pressure differences –parallel to the wind Drag force, D, on the sail: v1v1 u sail v3v3 p high p low

3 “Sailing” the mills in Mesopotamia First historic record from 1700BC in Mesopotamia. Afghan records 700AD show the title: “Millwright” as a common one. Mill-ruins in Iran and Afghanistan shows widespread use Known as “Persian wind mill”: –purely drag devices, using “sails” –fixed direction –slow rotating (slower than the wind) –poor efficiency, less than 10%

4 ”Sailing” the mills elsewere Chinese drag-type mills –First record in 1219 A.D., possibly much older –No screen – the sails were adjusting to the wind direction –Could be used in all direction Recent design: –Savounius-type turbines –Cup aneometers Said to be the most “re-invented” turbine.....

5 Turbines in medieval Europe First record in Europe in 1185, Yorkshire. The “Windmill Psalter” from Canterbury, 1270, with picture. Horizontal axed – “sails” does not move parallel with the wind, but perpendicular to the wind. Lift-force is dominant: –no longer “sails” but “wings” Wind speed is no longer the limitation for the rotational speed.

6 Drag-type vs. lift-type turbines Drag force:Lift force: v1v1 u sail w axis of rotation D v1v1 u wing axis of rotation w u L

7 First industrial revolution? Alongside watermills, the only source of mechanical power –3-7 kW out-put, depending on size and wind conditions Used for grinding Long lasting design: –Great variation in structural design and control mechanisms but the overall principle stayed the same till the 18th century. By the 14th century, it was widely used in whole Europe

8 Fortunes to the Netherlands Need for drainage lead to new development The new design featured: –a shaft to lead the power to ground level. –possibility to link several mills together –gradually improvement in the wing design. Gave the opportunity for new uses

9 Variations in structural design

10 Scientific research Design done by craftsmen for 3400 years John Smeaton - first wind scientist? –Measuring efficiency, C P = 0,28 –Designed the twisted blade. The modern turbine is “ready”: 1.Chambered leading edge (airfoil) 2.Blade-beam at 25% of airfoil length 3.Non-linear twist of airfoils 200 years of optimizing still to go!

11 Wild West Wind Fan type turbines in USA: –Halladay introduced in 1854 –Aermotor ca 1870 Autonomous system –Turned after the wind –Turned out of the wind at high speeds Higher speed and efficiency Widely used –From : 6 million –Still in use to day

12 Wind goes electric First large scale electric wind turbine in 1888: Charles F. Brush –Ø 17 m –12 kW –step-up gearbox (50:1) –10 / 500 r.p.m. First Danish electrical wind turbine in 1891: Poul La Cour –low solidity (ratio of area) –airfoil shaped blades –higher rotational speed –25 kW

13 Modern theory is developed Research on propellers and airfoils –NACA (later NASA) in USA and Göttinger in Germany –Airfoil and propeller theory was developed –Modern wind turbines: a spin-off from war-industry (?) Albert Betz: –Worked on the theoretical limit of wind turbines: the Betz’ limit. An ideal turbine, independent of design, will only be able to extract 59,3% of the available kinetic energy in the wind. –Was important in developing the Blade Element Momentum Methode. Ludvig Prandt’l: –Simplified the complex analysis of Betz. –Developed Prandt’l Tip Loss Factor: Theoretical model for the loss in lift at the tip of a turbine blade The theoretical foundation for the modern turbine was made!

14 Various attempts: Smith-Putam, 1941, USA: 1.25 MW, 175 foot 2 steel blades (16 tons) Down-wind type Destroyed after less than 1000 hours Gedser Mill, 1960s, DK: 200 kW 3 glass fibres blade Up-wind type Basis for the Danish concept Hutter, 1968, D: 2 glass fibres and plastic blades Shedding aerodynamic loads 4000 hours before project was ended

15 The Danish Concept Three bladed Up-wind Dimensioned to withstand gusts AC – generators Constant rotational speed Automatic yawing (turning after the wind) Stall controlled. Great commercial success in the 80s –The 55 kW sold over –Size gradually grew –VESTAS gained a leading position in the marked

16 Growing in the wind

17 What now? Potential for improving: –transmission, mechanical gears is the Achilles heal of the turbine –lighter and stronger materials in the blades –individually pitched (regulated) blades –lower sound level –decrease tip-losses –making installations and maintenance more efficient –CUTING COSTS Moving the turbines off-shore –floating installations no one can see (and would not protest against) Larger turbines –5 MW is built, 7 MW is discussed.

18 What have we learned? Wind turbines is one of the oldest energy sources we know of The development of modern type turbines has taken nearly 900 yrs Have had great impact on the economy in various periods The modern turbine was made 250 yrs ago Basic theory only available in less than 90 yrs Still lost of things to do