Binary Cycle Geothermal Power Plants were the most advanced form of geothermal power plant ever. It did not use dry steam or flash steam. Just water and low-temperature secondary fluid. This made geothermal power commonplace.

(Note : The background section of this page uses most of the same words as the flash steam geothermal power page of Terra Futura to save time.)


Geothermal hot springs had been used for bathing since Paleolithic times. The Romans used hot springs to feed public baths. They also used hot springs for heating houses. In the early 20th century, heating started to be based directly on geothermal energy. The first of these were used in greenhouses. By the 1930s, geothermal energy was used to heat houses. In the 1960s, geothermal energy took on electricity generation.

In 1960, Pacific Gas and Electric created the first successful geothermal power plant. It took heat from earth's core and used it to heat a fluid. In this case, it was dry steam. This required a superheater to convert wet steam into dry steam. The dry steam turned a turbine which, in turn, turned a generator that generated electricity. The dry steam would then be condensed back into water. Dry steam power plants were the simplest design for a geothermal power plant. But there was a problem. The temperature at which this could be done was 150°C. By comparison, flash steam power plants were much hotter.

In the early 21st century, flash steam power plants were the most common geothermal power plants on Earth. High-pressure hot water with a temperature of 180°C or more was transferred into low-pressure tanks. The water turned to steam. This flash steam drove turbines. The turbines turned generators that generated electricity. These power plants were used in 24 countries in the world. Flash steam power plants had the same problem as dry steam plants. The temperature required was so high that only certain hot spots could be used. Binary cycle power plants would change all that.


Tech Level: 10-11

Binary cycle power plants were different from the rest. Pumps would pump hot water into a heat exchanger. The heat was then transferred to a secondary working fluid with a lower boiling point. This fluid was most likely butane or pentane which was vaporized at 57°C. This turned a turbine which turned a generator which generated electricity. Because of the low temperature, binary cycle power plants could be placed anywhere. Geothermal energy became commonplace.

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