function calculateHeatRate() {
var powerMW = parseFloat(document.getElementById('powerOutput').value);
var fuelKgHr = parseFloat(document.getElementById('fuelConsumption').value);
var gcv = parseFloat(document.getElementById('calorificValue').value);
var auxPct = parseFloat(document.getElementById('auxPower').value);
if (isNaN(powerMW) || isNaN(fuelKgHr) || isNaN(gcv) || powerMW <= 0 || fuelKgHr <= 0 || gcv <= 0) {
alert("Please enter valid positive numbers for Power, Fuel, and GCV.");
return;
}
// 1. Total Heat Input in kcal/hr
var totalHeatInputKcal = fuelKgHr * gcv;
// 2. Gross Heat Rate = Total Heat Input / Gross Power Output
// Note: Gross Power is in MW, need to convert to kW for kcal/kWh
var grossPowerKW = powerMW * 1000;
var grossHeatRate = totalHeatInputKcal / grossPowerKW;
// 3. Net Power Output (subtracting auxiliary)
var netPowerMW = powerMW * (1 – (auxPct / 100));
var netPowerKW = netPowerMW * 1000;
// 4. Net Heat Rate
var netHeatRate = totalHeatInputKcal / netPowerKW;
// 5. Overall Plant Efficiency (%)
// Standard constant: 1 kWh = 860 kcal (Thermal equivalent)
var netEfficiency = (860 / netHeatRate) * 100;
// UI Updates
document.getElementById('results-box').style.display = 'block';
document.getElementById('grossHeatRateResult').innerHTML = grossHeatRate.toFixed(2);
document.getElementById('netEfficiencyResult').innerHTML = netEfficiency.toFixed(2);
document.getElementById('totalHeatInput').innerHTML = (totalHeatInputKcal / 1000000).toFixed(2);
document.getElementById('netPowerOutput').innerHTML = netPowerMW.toFixed(2);
document.getElementById('netHeatRateResult').innerHTML = netHeatRate.toFixed(2);
}
Understanding Heat Rate in Thermal Power Plants
In thermal engineering, the Heat Rate is a measure of a power plant's efficiency. It represents the amount of thermal energy (fuel) required to produce one unit of electrical energy (1 kilowatt-hour). A lower heat rate indicates a more efficient power plant.
The Core Formula
Heat Rate (kcal/kWh) = [Fuel Consumption (kg/hr) × Calorific Value (kcal/kg)] / Power Output (kW)
Key Components
Gross Power Output: The total electricity generated at the terminals of the generator.
Auxiliary Consumption: The power used by the plant's own equipment (pumps, fans, conveyors) to function.
Gross Calorific Value (GCV): The total heat released by a unit of fuel when it is burned completely.
Net Heat Rate: This accounts for the energy lost through auxiliary consumption, providing a more realistic view of the plant's commercial performance.
Practical Example
Imagine a 210 MW coal-fired unit consuming 120,000 kg of coal per hour. If the coal has a GCV of 4,000 kcal/kg:
Monitoring the heat rate is critical for operational economics. Even a small reduction in heat rate (e.g., 10 kcal/kWh) can result in millions of dollars in fuel savings annually for large utility-scale power stations. Factors such as condenser vacuum, boiler fouling, and turbine degradation all contribute to a rising (worsening) heat rate over time.