This next several pages present knowledge on power generation efficiency. The pages provide:
- Basic engineering definitions of electrical production efficiency,
- Fuel energy content for a wide variety of fuels, and
- Power production efficiencies by technology
The most current power production efficiencies are provided based on state-of-the-art equipment that is most recently available on the market or expected to be available within 18 months. Efficiency tables can be found using the links below:
A summary of the tables appears below:
Basic Principles of Electrical Generation
Electrical energy generation involves the conversion of primary energy into electricity.
|Generation Type||Conversion Processes|
|Hydro Power Plant||The conversion of water's "mechanical" energy or movement into electrical energy|
|Nuclear Power||The conversion of the nuclear energy released by nuclear fuel into electrical energy|
|Thermal Power Plant||The conversion of the chemical energy of fossil fuel into electrical energy|
|Solar Energy||The conversion of sunlight radiation or "protons packages" into electrical energy|
|Fuel Cell||The conversion of the chemical energy from an oxygenation controlled reaction directly into electrical energy|
In practice, the process of generating electricity relies on several transformations since most forms of primary energy are not directly convertible into electricity. For example, the primary energy in a thermal power station is converted first to high temperature steam, an intermediate heat source, then into mechanical energy in the steam turbines, which are physically connected with power generators where the electricity is produced. Direct energy conversion, of course, would be more efficient since electrical power could be generated without intermediate equipment and energy losses.
In physics theory, is the efficiency of a thermal electricity generation process. Carnot efficiency is the maximum possible efficiency for a heat engine and is defined by the temperature (T) differential of heat entering and exiting the process:
In general, the larger the difference in temperature between the hot source and the cold sink, the larger the potential thermal efficiency of the cycle. The cold side of any heat engine is limited to being close to the ambient temperature of the environment, or roughly 300 Kelvin. Most efforts to improve the thermodynamic efficiencies of heat engines focus on increasing the temperature of the source, given material limits.
Input steam temperature
543 degrees C
Sink temperature in a river
23 degrees C
= (543 – 23) / 543 = 64%
The actual efficiency of various heat engines used today has a large range:
- 10 to 15 percent for a geothermal power plant
- 25 percent for most automotive gasoline engines
- 49 percent for a supercritical coal-fired power station
- 60 percent for a steam-cooled combined cycle gas turbine.
All these processes gain their efficiency (or lack thereof) from the temperature drop across them. Significant energy may be used for auxiliary equipment, such as pumps, which effectively reduces efficiency.
Practical Efficiency Defined
Electric power plant efficiency, , is defined as the ratio of useful electricity output from the generating unit, in a specific time unit, and the energy value of the fuel source supplied to the plant, within the same time.
Energy value of fuel in one time unit
1 tone of oil equivalent
11,628 kWh in net calorie value
Useful electricity output in one time unit
Thermoelectric power plant efficiency
= 4,505 / 11,626 = 38.7%
Power plant energy loss
11,628 kWh – 4,505 kWh = 7,123 kWh
The basic definition is simple enough. The denominator is the heat contact, which is the product of the burned mass over some period of time multiplied by the fuel’s net calorie value. Electricity output, the numerator, is the net power output of the plant over the same time period. The difference between the two terms represents power plant losses.
Sequential Conversion Efficiencies
Practical efficiency compares grid injected power to the NCV of the input fuel. Sequential efficiencies track losses for each energy transformation.
|Process Stage||Avg. Loss||Description||Net Efficiency|
|Primary Fuel||0%||Initial condition||100%|
|Steam Generator||11%||Mass, water vapor and ash losses (if any) in combustion; Heat losses steam cooling||89%|
|Mechanical Turbine||48%||Heat loss in the condenser (cold source); friction (ball bearings), and ancillary equipment (pumps)||41%|
|Power Generator||1%||Minor electrical losses||40%|
|Balance of Plant||2%||Primary electrical losses (transformer, substation, cabling)||38%|