Supercritical Technology

Supercritical Technology

  • "Supercritical" is a thermodynamic expression describing the state of a substance where there is no clear distinction between the liquid and the gaseous phase (i.e. they are a homogenous fluid). Water reaches this state at a pressure above 221 bar
  • Up to an operating pressure of around 190 bar in the evaporator part of the boiler, the cycle is sub-critical. This means, that there is a non-homogeneous mixture of water and steam in the evaporator part of the boiler. In this case a drum-type boiler is used because the steam needs to be separated from water in the drum of the boiler before it is superheated and led into the turbine.
  • Above an operating pressure of 221 bar in the evaporator part of the boiler, the cycle is supercritical. The cycle medium is a single phase fluid with homogeneous properties and there is no need to separate steam from water in a drum. Once-through boilers are therefore used in supercritical cycles.




  • Supercritical cycle units offer a number of advantages. The most obvious advantage is higher efficiency, and therefore, saving of fuel resources. The improvement in efficiency varies from 1.3% to 3.6% depending upon the steam parameters.
  •   e.g. Capital cost for a supercritical power station shall be about 2% higher than that of sub-critical power plant but at the same time the plant efficiency shall improve from 38.64% to 39.6%.