At the dead state, both the system and its surroundings possess energy but no exergy, and hence there is no spontaneous change within the system or the surroundings. Available energy, A = H − T0S, or exergy is a measure of the departure from the ambient or dead state.

Dead State – A rejecting state that is essentially a dead end. Once the machine enters a dead state, there is no way for it to reach an accepting state, so we already know that the string is going to be rejected. Transition – A way for a machine to go from one state to another given a symbol from the input.

Dead state of a thermodynamic system When a system comes in equilibrium to its surroundings, which means that the availability of the system is zero it is called in dead state. No useful work can be obtained from a system which is in dead state. Category: Engineering Thermodynamics.

exergy

In a reversible process, this value is zero. as exergy is the maximum work that can be obtained via a reversible process, from a temperature T, when the cold sink is the surroundings at temperature T0. The amount of work obtained is always less than the heat input and the ratio is termed the ‘Carnot efficiency. ‘

Gibbs free energy measures the useful work obtainable from a thermodynamic system at a constant temperature and pressure. When a system changes from an initial state to a final state, the Gibbs free energy (ΔG) equals the work exchanged by the system with its surroundings, minus the work of the pressure force.

This is most commonly electrical work (moving electric charge through a potential difference), but other forms of work are also possible. For instance, examples of useful, non-expansion work in biological organisms include muscle contraction and the transmission of nerve impulses.

Power is a measure of the amount of work that can be done in a given amount of time. Power equals work (J) divided by time (s). The SI unit for power is the watt (W), which equals 1 joule of work per second (J/s). Power may be measured in a unit called the horsepower.

So to get the GPE of an object you need a formula, the formula is MASS X GRAVITY X HEIGHT (M X G X H).

The energy transfer to light energy is the useful transfer. The rest is ‘wasted’. It is eventually transferred to the surroundings, making them warmer. This ‘wasted’ energy eventually becomes so spread out that it becomes very difficult to do anything useful with it.

For example lighting a light bulb uses electrical energy to make light energy which is useful. However, think about how that light bulb gets hot after it has been on for a little while, that is thermal energywhich is wasted energy.

Electrical energy

There are three methods of energy transfer that we need to learn: conduction, convection, and radiation.

• Conduction: Heat is thermal energy, and in solids it can be transferred by conduction.
• Convection: Fluids, that is both gases and liquids, can transfer heat energy by convection.
• Radiation:

Useful energy. Useful energy is energy in the place we want it and the form we need it. Wasted energy is energy that is not useful enrgy. Useful energy and wasted energy both end up being transferred to the surroundings, ehich become warmer.

Energy, in physics, the capacity for doing work. It may exist in potential, kinetic, thermal, electrical, chemical, nuclear, or other various forms. There are, moreover, heat and work—i.e., energy in the process of transfer from one body to another.

useful output energy refers to the useful energy that is transferred by the device (eg thermal energy by a heater) input energy refers to the total energy supplied to a device.

Calculating efficiency

1. The efficiency of a device, such as a lamp, can be calculated:
2. efficiency = useful energy out ÷ total energy in (for a decimal efficiency)
3. or.
4. efficiency = (useful energy out ÷ total energy in) × 100 (for a percentage efficiency)

The second law says that each time energy gets transferred or transformed, some of it, and eventually all of it, gets less useful. That’s the truth. It gets less useful, until finally, it becomes mostly useless (at least as far as its ability to make things happen is concerned).

Input​ refers to the amount of energy put into a device, and ​ output​ refers to the amount of energy that comes out. A device may change the type of energy but not the amount. For example, a light bulb’s input energy is the form of electrical energy, and its output energy is in the form of light and heat. Efficiency.

It is thermodynamically impossible to have an efficiency of more than 100%, as this implies that more energy is being produced than is being put in. For this reason the performance is expressed as a Coefficient of Performance (COP) rather than an efficiency. The above example would be expressed as having a COP of 3.