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Useful output energy is always lower than input energy. Efficiency of power plants, world total, 2008. Energy conversion efficiency (η) is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The input, as well as the useful output may be chemical, electric power, mechanical work, light (radiation ...
But energy splits up during usage and its output does not have the same potential for the physical performance as before. [4] For this reason it is important to distinguish between input and output of energy usage. The input side can easily be measured with the help of the meter readings.
The output power of a motor is the product of the torque that the motor generates and the angular velocity of its output shaft. Likewise, the power dissipated in an electrical element of a circuit is the product of the current flowing through the element and of the voltage across the element. [1] [2]
If energy output and input are expressed in the same units, efficiency is a dimensionless number. [1] Where it is not customary or convenient to represent input and output energy in the same units, efficiency-like quantities have units associated with them. For example, the heat rate of a fossil fuel power plant may be expressed in BTU per ...
Therefore, the efficiency of all real machines is less than 1. A hypothetical machine without friction is called an ideal machine; such a machine would not have any energy losses, so its output power would equal its input power, and its efficiency would be 1 (100%). For hydropower turbines the efficiency is referred to as hydraulic efficiency ...
Open systems have input and output flows, representing exchanges of matter, energy or information with its surroundings. An open system is a system that has external interactions. Such interactions can take the form of information, energy, or material transfers into or out of the system boundary, depending on the discipline which defines the ...
Energy input and output will always balance according to the First Law of Thermodynamics or the energy conservation principle. Exergy output will not equal the exergy input for real processes since a part of the exergy input is always destroyed according to the Second Law of Thermodynamics for real processes. After the input and output are ...
A 100% efficiency implies equal input and output: for 1 kWh of output, the input is 1 kWh. This thermal energy input of 1 kWh = 3.6 MJ = 3,412 Btu; Therefore, the heat rate of a 100% efficient plant is simply 1, or 1 kWh/kWh, or 3.6 MJ/kWh, or 3,412 Btu/kWh