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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), or heat .
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 ...
Since space is a near-vacuum, this process has close to 100% efficiency. Thermal energy is unique because it in most cases (willow) cannot be converted to other forms of energy. Only a difference in the density of thermal/heat energy (temperature) can be used to perform work, and the efficiency of this conversion will be (much) less than 100%.
Low speed diesel engines like the MAN S80ME-C7 have achieved an overall energy conversion efficiency of 54.4%, which is the highest conversion of fuel into power by any single-cycle internal or external combustion engine. [9] [10] [11] Engines in large diesel trucks, buses, and newer diesel cars can achieve peak efficiencies around 45%. [12]
In general, energy conversion efficiency is the ratio between the useful output of a device and the input, in energy terms. For thermal efficiency, the input, Q i n {\displaystyle Q_{\rm {in}}} , to the device is heat , or the heat-content of a fuel that is consumed.
Every human activity, transport and industrial process generates waste heat, being possible to harvest residual energy from cars, aircraft, ships, industries and the human body. [1] From cars the main source of energy is the exhaust gas. [32] Harvesting that heat energy using a thermoelectric generator can increase the fuel efficiency of the car.
Energy efficiency may refer to: Energy efficiency (physics), the ratio between the useful output and input of an energy conversion process Electrical efficiency, useful power output per electrical power consumed; Mechanical efficiency, a ratio of the measured performance to the performance of an ideal machine
A simple cycle gas turbine achieves energy conversion efficiencies from 20 to 35%. [5] Typical coal-based power plants operating at steam pressures of 170 bar and 570 °C run at efficiency of 35 to 38%, [6] with state-of-the-art fossil fuel plants at 46% efficiency. [7] Combined-cycle systems can reach higher values.