What is a Supercritical Power Plant?

To increase the efficiency of steam power plants the basic method is to improve the thermal efficiency by increasing the operating pressure.

As the pressure increases the boiling temperature of water increases and the latent heat of vaporization decreases. Increase in pressure and temperature leads water to appoint at which the latent heat of vaporization is zero, or there is no boiling. Water directly becomes steam. This is the Critical Pressure and the Critical Temperature. For steam this occurs at 374degC and 220.6 bar.

Conventional steam power plants operate at steam pressures in the range of 170 bar. They are Subcritical power plants. The new generation of power plants operates at pressures higher than the critical pressure. These are Supercritical power plants.

The efficiency of the Rank in cycle depends on the pressure at which it operates. Higher pressure and temperature increase the efficiency of the thermal cycle and power plant. This is the reason for operating at higher steam pressures.

OPKL is not Supercritical It is Advanced Supercritical

The Critical Pressure and the Critical Temperature of water is 374degC and 220.6bar. But OPKL is using 595 degC and 250 bar.

What make a Supercritical Power Plant Different?

Higher Efficiency
Supercritical steam conditions improve the turbine cycle heat rate significantly over subcritical steam conditions. The extents of improvement depend on the main steam and reheat steam temperature for the given supercritical pressure. A typical supercritical cycle will improve station heat rate by more than 5%. This results in fuel savings to the extent of 5%. Overall supercritical power plant efficiency of 42% is achievable with current supercritical parameters.

Improved heat rate results in 5% reduction in fuel consumption and hence 5% reduction in CO2 emissions per MWh energy output. Typically for 660 MW supercritical unit the annual reduction in CO2 emission will be about 600,000 tones of CO2 with respect to baseline emission established by CEA for 2008 – 2009.

Supercritical technology based thermal power project is a potential candidate to avail the benefits under Clean Development Mechanism (CDM) established by United Nations Framework Convention on Climate Change (UNFCCC).

Operational Flexibility
Supercritical technology units also offer flexibility of plant operation such as:

  • Shorter start-up times
  • Faster load change flexibility and better temperature control
  • Better efficiency even at part load due to variable pressure operation and
  • High reliability and availability of power plant