The Organic Rankine Cycle

The Rankine cycle is named after its inventor, the scottish physicist William Rankine (1820-1872), one of the fathers of thermodynamics.

The concept behind the Organic Rankine Cycle is simple, but is better explained through a schematic.

rankine wiki w360

A heat source - such as the flames of aboiler, hot flue gases or any other comparable heat source - heats, by way of a heat exchanger (2) a special working fluid that is the real secret behind LT ORC technology. This fluid, which is 100% biodegradable and non-toxic, starts boiling and expands dramatically even when exposed to a temperature lower than that of water and becomes a dry, highly pressurized gas which moves a turbine (3), producing mechanical power (Wturbine ) that, in our plants, is converted by a direct drive alternator into electric power, which is used on site or sent to the power grid.

On exiting the turbine the working fluid goes through to a condensating heat exchanger (4) where it gives off its excess heat, condenses into a liquid form again and goes to a storage tank (1), ready to be pumped back to the secondary exchanger, thus closing the cycle.

The excess low-temperature heat given off in the condensating exchanger (Qout) can used for ambiental heating purposes, or to preheat fuel, or again  to reduce the water content of biomass prior to burning, thus increasing its heating value.

(Rankine cycle schematic from Wikimedia Commons © Andrew Ainsworth, English Wikipedia. Licensed under GNU FDL)

Advantages of our LT-ORC Turbogenerators

There are several strong points that should motivate a client in choosing our systems over those of our competitors:

  • High thermodinamic efficiency of the Organic Rankine Cycle
  • Highly efficient turbine system (efficiency up to 90%)
  • Ability to operate under partial load (temperature or thermal input below nominal specs)
  • Low mechanical wear, due to the use of ceramic bearings;
  • Direct - drive alternator tmounted on the same shaft as the turbine, avoiding the efficiency losses inherent to gearboxes;
  • Zero turbine blade erosion, due to a totally dry working fluid;
  • Extremely long system lifecycle, due to the peculiar characteristics of our working fluid.
  • No need for ancillary water treatment plants;
  • Closed cycle = zero working fluid consumption
  • Sealed circuit = no working fluid deterioration
  • Good performances even under a partial load.

Furthermore, our turbogenerators:

  • Do not require specialized personnel or special authorizations to operate
  • Are characterized by an extreme applicability to several industrial sectors
  • Are absolutely environment-friendly.