Lower Heating Value Combined Heat and Power Efficiency Calculation

14 Jun 2021

What is the lower heating value combined heat and power efficiency of the plant (%)?

What is the formula to calculate the lower heating value combined heat and power efficiency of the plant?

The lower heating value combined heat and power (CHP) efficiency of the plant can be calculated using the following formula:

Efficiency = (Useful Energy Output / Energy Input) * 100

Where:

Useful Energy Output = Electrical Energy Output + Heat Energy Output

Electrical Energy Output = Rated Power * Capacity Factor * 1 hour

Heat Energy Output = Heat Energy Output at Rated Power * Capacity Factor * 1 hour

Energy Input = Fuel Energy Input * Capacity Factor * 1 hour

Given the information:

Rated Power = 200 kW

Capacity Factor = 60% (0.6)

Heat Energy Output at Rated Power = 300,000 Btu/h

Fuel Energy Input = Rated Power / Heat Rate

First, let's calculate the fuel energy input using the heat rate:

Fuel Energy Input = Rated Power / Heat Rate

Fuel Energy Input = 200 kW / 9000 Btu/kWhe = 0.0222 MMBtu (Million Btu)

Now, let's calculate the useful energy output:

Electrical Energy Output = Rated Power * Capacity Factor * 1 hour

Electrical Energy Output = 200 kW * 0.6 * 1 h = 120 kWhe

Heat Energy Output = Heat Energy Output at Rated Power * Capacity Factor * 1 hour

Heat Energy Output = 300,000 Btu/h * 0.6 * 1 h = 180,000 Btu

Useful Energy Output = Electrical Energy Output + Heat Energy Output

Useful Energy Output = 120 kWhe + 180,000 Btu = 120 kWhe + 0.18 MMBtu

Now, we can calculate the efficiency:

Efficiency = (Useful Energy Output / Energy Input) * 100

Efficiency = (120 kWhe + 0.18 MMBtu) / (0.0222 MMBtu) * 100

Calculating this value will give you the lower heating value combined heat and power efficiency of the plant as a percentage.