Shreya Vishnoi
Shakti Sustainable Energy Foundation team has identified some critical reasons for inefficiencies. These reasons are based on energy audit findings, efficiency assessment and benchmarking work done by several agencies including the National Productivity Council (NPC). Power plant efficiency is a holistic function of heat rate, APC, vintage, PLF & fuel quality.
Source: http://shaktifoundation.in/
A 10% increase in Gross Heat Rate would reduce the net efficiency by about 9%. As a result, more coal will be burned to generate the same electricity. Reasons for variations in heat rate are: Un-optimized boiler combustion, excess air and energy loss in the draft system, Low turbine cylinder efficiency, Inefficient air pre-heaters, Un-optimized performance of Low Pressure (LP) & High Pressure (HP) heaters, Deviations from Design Condenser Vacuum, Variation in steam temperature at Turbine Stop Valve (TSV), Variation in make-up water consumption from design parameters
A 10% increase in APC would reduce the net efficiency by about 1%. Reasons for poor APC are: Losses in Feed Water System, Losses in Draft System, Losses in Cooling Tower System.
A 10% change in PLF (or load) would result in a change in the efficiency by 1.3%. A reduced PLF can adversely impact the operating efficiency of a plant. For instance, at 50% operating load, the heat rate of subcritical units deteriorates by about 10%.
In plants having been in operation for more than 25 years, efficiency degrades by around 1 to 2% and capacity gets reduced by around 5 to 10%. About 45 units with 200/210 MW capacity, have operated for more than 25 years. Similarly, in the category of 500 MW units, the average operated life for almost 40% of the units is more than 15 years.
Coal quality is characterized in terms of its heating value which is generally expressed as Gross Calorific Value (GCV or Higher Heating Value – HHV) or Net Calorific Value (NCV of Lower Heating Value – LHV), together with its moisture, ash and volatile content. For Indian coal, the NCV is typically 7 to 12% of the GCV.
