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In 1866, Werner von Siemens discovered the dynamo-electric principle and thus enabled electricity to be put to practical use. The dynamo can convert mechanical energy into electrical energy in an economical way. Its invention laid the foundation for today's world of electrical engineering.
In 1922, Mark Benson was granted a patent for a boiler designed to convert water into steam at high pressure. Siemens acquired the patent and developed a reliable high-pressure steam generator. The first commercial Benson boiler went into operation in 1927 in the thermal power plant at Gartenfeld in Berlin.
In 1925, the Irish Free State awarded Siemens the contract for the electrification of the entire country. The core of the supply system was the hydroelectric power plant on the river Shannon with three 30 MVA generators (commissioned in 1929). Extension of the plant was completed in 1933 (another 25 MVA).
The continually increasing voltages transmitted over power lines also made tougher demands on switching technology. Because classic oil-filled switches were liable to explode, Siemens developed an expansion circuit-breaker using water as the quenching medium. The first circuit breaker of this type was supplied to the Hamburg public utility in 1930.
Power reaches the consumer via distribution and transmission systems. The SF6 circuit breaker was introduced in 1964 in order to switch the increasingly high voltages which were being transmitted. It operated with sulfur hexafluoride (SF6) as the quenching agent.
Block A of the power plant at Biblis near Worms went into operation on a trial basis in 1974. At the time, it was the largest nuclear power plant in the world. Its output of about 1200 MW was sufficient to supply all the power then required by a city with over two million inhabitants, including industrial users.
With the use of thyristors, a breakthrough was achieved in high-voltage DC transmission (HVDC). This technology was used for the first time in 1975 to transmit power along the 1400 km route between the hydroelectric power plant at Cabora Bassa (today: Cahora Bassa) in Mozambique and South Africa.
Oil and gas-fuelled power plants based on the highly economical and environmentally friendly combined-cycle technology - which combines gas and steam turbines - are in successful operation around the world. Siemens built the combined cycle power plant at Rye House in England in 1994, which won the company the Project of the Year Award.
Fuel cells are highly efficient without giving off any emissions. They generate energy from hydrogen and oxygen by an electrochemical process. In 1994, Siemens set a world record by producing high-temperature fuel cells with an output of 1.8 kW - three times the power density previously achieved.
With the turbine installed in 2002, the Mainz-Wiesbaden power plant operates at a record efficiency level of just under 60 percent, using 10 percent less fuel. The rotor blades are subject to forces the equivalent of hanging a 40-ton truck on each blade. In order to ensure the system is robust enough to withstand these forces on a long-term basis, the blade geometry had to be precisely designed by high-performance computers.