Diesel Generator Heat Rate Calculator
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Performance Results
Heat Rate (kcal/kWh)
0
Heat Rate (kJ/kWh)
0
Heat Rate (Btu/kWh)
0
Thermal Efficiency
0%
Typical diesel generator efficiency ranges from 30% to 45%.
Fuel Mass Flow
0 kg/hr
Specific Fuel Consumption
0 g/kWh
About Diesel Generator Heat Rate
The heat rate of a diesel generator is a critical metric used to determine the efficiency of a power plant or standalone generator unit. It represents the amount of thermal energy (from fuel) required to produce one unit of electrical energy (kWh). A lower heat rate indicates a more efficient generator, as less fuel is required to produce the same amount of electricity.
How to Calculate Heat Rate
To calculate the heat rate accurately, you need to know the mass of the fuel consumed and its energy content (Calorific Value). The formula used in this calculator is:
Heat Rate (kcal/kWh) = (Fuel Consumption (kg/hr) × LHV (kcal/kg)) / Power Output (kW)
Key Variables:
- Power Output (kW): The actual electrical load the generator is carrying. Do not use the rated capacity unless the generator is running at full load.
- Fuel Consumption (Liters/hr): The volumetric flow rate of diesel.
- Fuel Density (kg/L): Required to convert volume (Liters) to mass (kg). Standard diesel density varies between 0.82 and 0.86 kg/L depending on temperature and grade.
- Lower Heating Value (LHV): The net energy available in the fuel. For standard diesel, this is approximately 10,200 kcal/kg (or 42,700 kJ/kg).
Thermal Efficiency vs. Heat Rate
Thermal efficiency is the inverse of the heat rate. It describes the percentage of potential energy in the fuel that is successfully converted into electricity. The theoretical conversion factor is 1 kWh = 860 kcal. Therefore, the efficiency formula is:
Efficiency (%) = (860 / Heat Rate in kcal/kWh) × 100
Modern industrial diesel generators typically achieve thermal efficiencies between 35% and 45%. A heat rate significantly higher than 2500 kcal/kWh (approx 34% efficiency) may indicate mechanical issues, poor tuning, or operation at inefficient low loads.
Specific Fuel Consumption (SFC)
Another common metric displayed in the results is Specific Fuel Consumption (SFC). This measures the weight of fuel needed to produce one kWh. It is usually expressed in grams per kilowatt-hour (g/kWh). Lower SFC values correspond to better fuel economy and lower operating costs.
function calculateHeatRate() {
// Get inputs
var load = parseFloat(document.getElementById('genLoad').value);
var fuelFlowLiters = parseFloat(document.getElementById('fuelFlow').value);
var density = parseFloat(document.getElementById('fuelDensity').value);
var lhv = parseFloat(document.getElementById('fuelLhv').value);
// Validation
if (isNaN(load) || isNaN(fuelFlowLiters) || isNaN(density) || isNaN(lhv) || load <= 0) {
alert("Please enter valid positive numbers for all fields. Load cannot be zero.");
return;
}
// 1. Calculate Mass Flow (kg/hr)
var massFlow = fuelFlowLiters * density;
// 2. Calculate Energy Input (kcal/hr)
var energyInput = massFlow * lhv;
// 3. Calculate Heat Rate (kcal/kWh)
var heatRateKcal = energyInput / load;
// 4. Conversions
// 1 kcal = 4.184 kJ
var heatRateKj = heatRateKcal * 4.184;
// 1 kcal = 3.96832 Btu
var heatRateBtu = heatRateKcal * 3.96832;
// 5. Efficiency Calculation
// 1 kWh = 860 kcal (approx)
var efficiency = (860 / heatRateKcal) * 100;
// 6. Specific Fuel Consumption (g/kWh)
// (Mass Flow in kg * 1000) / Load in kW
var sfc = (massFlow * 1000) / load;
// Update UI
document.getElementById('resKcal').innerText = heatRateKcal.toFixed(2);
document.getElementById('resKj').innerText = heatRateKj.toFixed(2);
document.getElementById('resBtu').innerText = heatRateBtu.toFixed(0);
document.getElementById('resEff').innerText = efficiency.toFixed(2) + "%";
document.getElementById('effBar').style.width = Math.min(efficiency, 100) + "%";
document.getElementById('resMassFlow').innerText = massFlow.toFixed(2) + " kg/hr";
document.getElementById('resSfc').innerText = sfc.toFixed(1) + " g/kWh";
}
// Run calculation on load to show initial valid state
window.onload = function() {
calculateHeatRate();
};