Why Pentane in Geothermal?

  • Primarily, pentane is used to create a blowing agent which is then used to create a foam known as polystyrene. Polystyrene is used to make insulation materials for refrigerators and heating pipes. As well, pentane is used in geothermal power stations as a binary fluid, due to its low boiling point (36 o C).
  • Boiling Point: 36oC
  • Formula: C₅H₁₂
  • Melting Point: -130oC
  • Molar mass: 72.15 grams/mole

Geothermal power generation must operate with whatever temperature is found in a particular well. Water and steam work well at high temperatures. At lower temperatures, a “binary system” may sometimes provide better efficiency.

In a binary system, the hot fluid from the geothermal source is used to heat a second, lower boiling point fluid (in this case, pentane) to convert it to gas and drive a turbine. The nature of pentane allows the whole cycle (fluid to gas, drive the power generation turbine, and condense to fluid) to take place efficiently at a lower temperature.

At this location, a binary system is being used to squeeze additional power from the hot condensate leaving a primary water/steam turbine. Using an additional set of heat exchangers this energy is captured to heat low boiling point pentane and to drive an additional turbine. The pentane system harnesses more of the energy brought out of the ground.

Like getting something for nothing.