Supercritical & Ultra-supercritical technology
Definition
Conventional coal-fired power plants, which make
water boil to generate steam that activates a turbine, have efficiency of about
32%.
Supercritical (SC) and ultra-supercritical (USC)
power plants operate at temperatures and pressures above the critical point of
water, i.e. above the temperature and pressure at which the liquid and gas
phases of water coexist in equilibrium, at which point there is no difference
between water gas and liquid water. This results in higher efficiencies – above
45%.
Supercritical (SC) and ultra -supercritical
(USC) power plants require less coal per megawatt-hour, leading to lower
emissions (including carbon dioxide and mercury), higher efficiency and lower
fuel costs per megawatt.
Difference
Super-critical technology is more efficient than the
conventional sub-critical technology and higher super-critical parameters of
565/593 deg. C can lead to about 5% savings in fuel consumption as compared
to typical 500 MW sub critical units. However, the super-critical technology
being a new technology may involve higher capital cost for initial units and
a part of the higher capital cost may get offset by savings in fuel. With new
manufacturing entities being set up in the country, there may be reduction in
capital cost in the long run. Generally, the super-critical technology is
being adopted for large size units to achieve benefit of economies of scale
and faster capacity addition.
In India
A capacity of about 4000 MW is likely to be added in the
11th Plan through super-critical units of which about 1980 MW has already
been commissioned so far. In the 12th Plan, about 50% to 60% coal fired
capacity addition is expected to be from super-critical units
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