Thermodynamics

There are four laws of Thermodynamics:

  1. Energy is constant, energy cannot be destroyed or created
  2. Thermal equilibrium, heat transfer from hotter to colder object will stop when the temperature is equal
  3. Entropy of the universe always increase over time
  4. A perfectly crystalline (the most ordered state the substance can be in) has entropy of zero

Entropy

Entropy is energy dispersal, and it’s one way. Thermodynamics arrow of time states that entropy can only go through one direction. Energy always become messier and messier over time. For example, like a hot coffee in a glass. The heat in the coffee dispersed into the air, the glass, and the table itself. Another example, the sun exert energy to the earth. Everything that catch the sunlight get the energy. The plants can grow by photosynthesis, the herbivores receive energy by consuming the plants, the humans get energy when they consume the plants and animals, we also using sun’s energy to keep us warm and producing vitamin D.

The amount of energy in this universe is preserved since the big bang.

To calculate entropy, entropy = S(J/K), joules per kelvin, to calculate how the energy is distributed within a system.

If energy is constant, how do we get the energy, electricity?

As I said, the energy is conserved. For example, we get energy from the sun. The sun actually has constant amount of energy, it spread the energy slowly by releasing the photons. The sun has total 1788 * 10^47 Joules, calculated by Einstein E = mc^2, which m is the mass of an object, c is the speed of light. Mass is a form of a stored energy.

We convert the energy from sun to direct current (DC) electricity with photovoltaic (PV) effect. It can feed our home appliances. The excess energy the solar panel receives is stored in a battery with 80% - 90% efficiency (some energy lost as heat).

When we use the energy from our home appliances, the energy dispersed even more, increasing the entropy. For example, the LED that produce light, it increased the entropy into the air by increasing the heat.