The work potential of the energy contained in a system at a specified state is simply the maximum useful work that can be obtained from the system. You will recall that the work done during a process depends on the initial state, the final state.
The work potential of the energy contained in a system at a specified state is simply the maximum useful work that can be obtained from the system. You will recall that the work done during a process depends on the initial state, the final state.
The work potential of any energy source is the maximum amount of energy we can extract or harness to be used as maximum useful work and the rest/remaining of the lost or discarded energy is waste energy. Some amount of the energy is always discarded as waste, as we cannot harness 100% (full amount)of the energy from any source. But we can look to harness or extract the maximum amount of energy which can be converted into useful work. This useful work is termed as exergy or available energy.
Basic understanding of exergy:
As per second law of thermodynamics(qualitative law), if a hot body loses heat to a cold body quantity (magnitude) of the heat remains same but quality of the heat decreases. Quality of heat corresponds to work producing capability of the heat. Whenever there is reduction in quality of energy, there is entropy generation in a system. If entropy generation exists then there is exergy destruction or work producing capacity of heat decreases.
The work done by a system depends on the initial state, process path and the final state.
In exergy analysis initial state of a thermodynamic system is specified(not a variable),the maximum work output is obtained if the system undergoes reversible process between two specified states and the system must be in a dead state(thermodynamic equilibrium with the surroundings) to maximize the work output. Say if we want to harness maximum energy from a high temperature source reservoir with help of a reversible engine, we will have to discard the waste energy at surrounding temperature to get maximum useful work.
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