Power Plants - Performance Efficiencies

The performance of a power plant can be expressed through some common performance factors:

• heat rate (energy efficiency)
• thermal efficiency
• capacity factor
• load factor
• economic efficiency
• operational efficiency

Heat Rate (Energy Efficiency)

Overall thermal performance or energy efficiency for a power plant for a period can be defined as

φ_hr = H / E                                     (1)

where

φ_hr= heat rate (Btu/kWh, kJ/kWh)

H = heat supplied to the power plant for a period (Btu, kJ)

E = energy output from the power plant in the period (kWh)

Thermal Efficiency

Thermal efficiency of a power plant can be expressed as

μ_te = (100) (3412.75 Btu/kWh) / φ                                  (2)

where

μ_te = thermal efficiency (%)

• 1 kWh = 3412.75 Btu

Capacity Factor

The capacity factor for a power plant is the ratio between average load and rated load for a period of time and can be expressed as

μ_cf = (100) P_al / P_rl                                       (3)

where

μ_cf = capacity factor (%)

P_al = average load for the power plant for a period (kW)

P_rl = rated capacity for the power plant (kW)

Load Factor

Load factor for a power plant is the ratio between average load and peak load and can be expressed as

μ_lf = (100) P_al / P_pl                                   (4)

where

μ_lf = load factor (%)

P_pl = peak load for the power plant in the period (kW)

Economic Efficiency

Economic efficiency is the ratio between production costs, including fuel, labor, materials and services, and energy output from the power plant for a period of time. Economic efficiency can be expressed as

φ_ee = C / E                                       (5)

where

φ_ee = economic efficiency (cents/kW, euro/kW, ...)

C = production costs for a period (cents, euro, ..)

E = energy output from the power plant in the period (kWh)

Operational Efficiency

Operational efficiency is the ratio of the total electricity produced by the plant during a period of time compared to the total potential electricity that could have been produced if the plant operated at 100 percent in the period.

Operational efficiency can be expressed as

μ_oe = (100)E /E_100%                                 (6)

where

μ_eo = operational efficiency (%)

E = energy output from the power plant in the period (kWh)

E_100% = potential energy output from the power plant operated at 100% in the period (kWh)