What is CHP Efficiency?
CHP (Combined Heat and Power) efficiency measures how effectively a cogeneration system converts fuel into useful energy outputs. Unlike conventional power generation that discards waste heat, CHP systems capture and utilize both electrical and thermal energy, achieving significantly higher overall efficiency.
Formula
The CHP efficiency formula is:
$$\text{CHP Efficiency} = \frac{W_{e} + Q_{o}}{Q_{i}} \times 100$$
Where:
- W_e = Useful Electrical Output (Joules)
- Q_o = Useful Thermal Output (Joules)
- Q_i = Total Fuel Input (Joules)
Example Calculation
Consider a CHP system with:
- Useful Electrical Output (W_e) = 300 J
- Useful Thermal Output (Q_o) = 600 J
- Total Fuel Input (Q_i) = 1,200 J
$$\text{CHP Efficiency} = \frac{300 + 600}{1{,}200} \times 100 = \frac{900}{1{,}200} \times 100 = 75$$
The system achieves 75% efficiency by converting three-quarters of the fuel input into useful energy.
How to Use This Calculator
- Enter the Useful Electrical Output in Joules (the electrical energy produced)
- Enter the Useful Thermal Output in Joules (the heat energy captured and utilized)
- Enter the Total Fuel Input in Joules (the energy content of fuel consumed)
- Click Calculate to determine the CHP efficiency percentage
Understanding CHP Efficiency
Benefits of High CHP Efficiency
- Energy Savings: Utilizes waste heat that would otherwise be lost
- Cost Reduction: Lower fuel consumption per unit of useful energy
- Environmental Impact: Reduced emissions through efficient fuel use
- Grid Independence: On-site power generation reduces transmission losses
Typical CHP Efficiency Ranges
- Conventional Power Plants: 30-40% (electrical only)
- Good CHP Systems: 65-80% (combined electrical and thermal)
- Advanced CHP Systems: 80-90% (optimized heat recovery)
Factors Affecting CHP Efficiency
- Technology Type: Gas turbines, reciprocating engines, or fuel cells
- Heat Recovery Design: Quality of heat exchangers and recovery systems
- Operating Conditions: Load factor and thermal demand matching
- Maintenance: System condition and optimization
- Fuel Quality: Energy content and combustion characteristics
Applications
CHP systems are particularly effective in facilities with concurrent electrical and thermal demands:
- Industrial Plants: Process heat and power requirements
- Hospitals: Heating, cooling, and electricity needs
- Universities: Campus-wide heating and power distribution
- District Heating: Community-scale thermal networks
- Data Centers: Waste heat recovery for heating applications