Power Plant
Coal & Fuel Handling
GCV→NCV conversion for fuel analysis reports, and daily coal requirement / stock days-of-cover for fuel planning — the two calculations a plant's coal/commercial desk runs every day.
Verified against published standard
Enter GCV, hydrogen %, and moisture % to calculate NCV.
Daily Coal Requirement & Stock Days of Cover
Enter SCC, generation, and current stock to calculate.
About This Calculation
GCV (Gross Calorific Value, from bomb calorimetry) overstates the heat a real boiler actually recovers, because it assumes the water formed by combustion fully condenses and gives up its latent heat — in a real boiler, that water leaves as vapor in the flue gas, carrying its latent heat away unused. NCV (Net Calorific Value) corrects for exactly that loss, and is the figure that actually belongs in a boiler efficiency or fuel consumption calculation. Alongside it, daily coal requirement and stock days-of-cover are the two numbers a plant's fuel/commercial desk checks every single day.
Frequently Asked Questions
Why does hydrogen content matter for the GCV→NCV correction, not just moisture?
Every kilogram of hydrogen in the fuel combines with oxygen to form 9 kg of water during combustion (from the molecular weight ratio of water to hydrogen, 18/2) — that combustion-formed water carries away latent heat exactly the same way the fuel's own inherent moisture does, so a fuel with negligible inherent moisture but meaningful hydrogen content (like most liquid and gaseous fuels) still needs a real GCV→NCV correction.
Which calorific value should be used for heat rate and fuel consumption calculations?
NCV — it represents the heat actually recoverable in a real boiler, which is what a heat rate or specific fuel consumption figure is meant to reflect. Using GCV instead would systematically understate specific fuel consumption (make the plant look more efficient than it actually is), since it credits heat that never actually reaches the working fluid.
Why does days-of-cover assume constant SCC and generation rather than giving a fixed answer?
Both genuinely vary — SCC drifts with coal quality, mill/combustion condition, and ambient conditions, while generation follows grid dispatch — so days-of-cover is only ever a projection under the assumption that recent conditions continue, which is exactly why it should be re-checked with updated figures rather than treated as a one-time calculation.