Calculator for Exergy, Anergy and Energy

Calculate the total energy of a system from exergy and anergy, with different units. Exergy is the component of thermal energy that can do work in a process. Anergy, on the other hand, cannot do any work. The thermal energy is the sum of both. Please enter two values to calculate the third value and the ratios./p>

The two components, exergy and anergy, together constitute 100 percent of the total thermal energy. From any two of the three values, regardless of their units, the third value can be calculated. Exergy can be negative if the energy level is below the ambient level. This occurs, for example, when a system is colder than its surroundings. Anergy, on the other hand, can never be negative, nor can energy.

Example: In a combined heat and power plant (CHP), biogas is burned to simultaneously generate electricity and heat. The CHP produces 10 kWh of electricity and 15 kWh of heat at an ambient temperature of 20 °C (293.15 K). The electrical energy (electricity) is almost entirely exergy, as it can be directly converted into work: Exergy(electricity) = 10 kWh. The heat is supplied at 80 °C (353.15 K). The exergy of the heat is correctly calculated using the Carnot factor: Exergy(heat) = 15 kWh * (1 - 293.15 K / 353.15 K) ≈ 15 kWh * 0.17 ≈ 2.55 kWh. The total energy is 25 kWh (10 kWh electricity + 15 kWh heat), and the total exergy is 12.55 kWh (10 kWh + 2.55 kWh). Anergy is energy - exergy = 25 kWh - 12.55 kWh = 12.45 kWh.
The anergy value is relatively low here because most of the energy is present as high-quality electricity and the heat is still readily usable.

Exergy is the portion of energy that can be converted into any other form of energy, that is the usable portion. For example, a stream of hot steam contains exergy because it can be used to drive a turbine and generate electricity. Anergy is the unusable portion of energy. This is heat that is only slightly above ambient temperature and can no longer be used effectively to perform work. Together, exergy and anergy constitute the total energy of a system. The higher the temperature or pressure of an energy form compared to its surroundings, the more exergy it contains. Anergy remains when the exergy has been extracted.