Power to the people
Modern society could not survive without the regular supply of vast quantities of electricity – and the capacity to generate electricity on the scale seen today can be traced back to 1884, when Charles Parsons patented the compound steam turbine. Parsons’s turbine design is still in use in power stations across the globe. The story of the turbine is told in the BBC programme Genius of Invention.
A number of other geniuses paved the way for Parsons’s great breakthrough – in particular Michael Faraday (1791–1867), who showed that motion and magnetism could be combined to create electricity. Faraday’s experiments led to the creation of the world’s first electrical generator and made it possible for electricity to travel hundreds of miles from where it was generated. By this means, electrical power would eventually be available to billions of people at the flick of a switch.
The beginnings of the turbine
In 1883 Charles Parsons was in charge of the electrical generators at the engineering firm of Clarke Chapman on Tyneside. At that time, like every other generator, they were powered by a reciprocating steam engine – based on the design by James Watt (1736–1819) – which worked by converting vertical motion into rotary motion. To Parsons, the inefficiencies of this two-step engine were clear. He wanted an engine with a one-step rotary motion and minimal vibration, so he turned to the turbine.
The turbine operates on the same principle as a windmill. In a windmill, the energy of the wind works directly on the rotating parts to create mechanical action. Parsons decided to use high-pressure steam as his energy source. The steam would be blasted at the steel blades of the turbine – which were arranged in wheel formation – causing the device to rotate on its spindle and turn an electrical dynamo.
Since the energy created by expanding steam is much higher than the energy created by wind, Parsons had to find a way to maximize the efficiency of the process, and many refinements followed. Rather than blasting the steam at a single ‘wheel’ of blades, he used a row of wheels, all rotating around the same spindle. Each successive wheel, or turbine stage, through which the steam passed was designed to work with ever-decreasing pressures, meaning that Parsons’s turbine could extract far more energy from the same volume of steam than would otherwise have been the case.
Another vital consideration of turbine manufacture is the speed at which the blades can revolve. The Parsons turbine is designed so that each successive wheel, or turbine stage, through which the steam passes is built with narrower gaps between its individual blades. To get through a narrower gap, the steam has to travel at a higher speed, which increases the speed of revolution.
More than 130 years later, turbines are still made using exactly the same principle as that devised by Parsons. Before Parsons, electrical generators were operating at under 500 revolutions per minute. His turbo-generator could rotate at 4800 revolutions per minute, opening the doors to the creation of electricity on an enormous scale.
(With thanks to Geoff Horseman, Chief Turbine Engineer, Siemens, C. A Parsons Works, Newcastle upon Tyne.)