Organic Rankine Cycle

The Rankine Cycle

The Rankine Cycle is a thermodynamic cycle which converts heat into work. The heat is supplied externally to a closed loop, which usually uses water as working fluid. The Rankine Cycle based on water provides approximately 85% of worldwide electricity production.

William Rankine

The Rankine cycle is named after William John Macquorn Rankine (July 5, 1820 - December 24, 1872), a Scottish engineer and physicist. He was a founding contributor to the science of thermodynamics. Rankine developed a complete theory of the steam engine and indeed of all heat engines. His manuals of engineering science and practice were used for many decades after their publication in the 1850s and 1860s. He published several hundred papers and notes on science and engineering topics, from 1840 onwards, and his interests were extremely varied, including, in his youth, botany, music theory and number theory, and most major branches of science, mathematics and engineering. He was an enthusiastic amateur singer, pianist and cellist who composed his own humorous songs.

The first Organic Rankine Cycles: the Naphtha Launch

The Rankine cycle is usually based on water as a working fluid. Applications of the cycle with different working fluids started to appear soon, such as the Naphtha boats. In 1883 Frank Ofeldt developed a unique power system which he hoped would have replaced steam. His naphtha engines are steam engines that boil naphtha (a form of gasoline) instead of water to drive the pistons. At the time, the government required a license to boil water in steam engines but did not require one to boil gasoline. Therefore, for the first time a gentleman boater could operate his own power boat without the assistance of an engineer. One would have to be of "gentleman's" means to own one of these vessels. In the 1880s, a 21 foot boat with a Naphtha engine cost $750 - one and a half times the annual wage of craftsmen who built them. (from the Mystic Seaport Museum website).

The Italian School

The Organic Rankine Cycle technology was seriously developed only during the XX century. In Italy, an experiment was carried out during the Thirties on the Island of Ischia. Important studies were conducted after the Second World War in Russia, USA and Israel. Back to Italy, during the Seventies the Italian ORC School was born at the Politecnico di Milano, Italy's most important engineering University. Its founder was Prof. Gianfranco Angelino, with his colleagues Prof. Ennio Macchi and Prof. Mario Gaia, the founder of Turboden.

Organic Rankine Cycle Today

Organic Rankine Cycle is a well-known and widely spread form of energy production, mostly in biomass and geothermal applications, but great rises in solar and heat recovery applications are also expected. Environmental concern over climate change and rising oil prices are powerful reasons supporting the explosive growth of this efficient, clean and reliable way of producing electricity.

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