Thermal energy is defined as the part of the internal energy of a thermodynamic system in equilibrium. The internal energy is proportional to its absolute temperature and is increased or decreased by energy transfer.
It can be considered a thermodynamic property.
By increasing the thermal energy of a body also increases the movement of the particles that compose it.
What is the origin of thermal energy?
Heat energy can be obtained in several ways:
- Nature. For example, geothermal energy or solar thermal energy.
- Chemical energy, through a chemical reaction.
- Exothermic reaction, such as the combustion of some fossil fuel.
- Nuclear fission energy or nuclear fusion energy. By splitting the nucleus of an atom, a large amount of heat is obtained.
- Electric energy by Joule effect or thermoelectric effect.
- By friction, as a residue of other mechanical or chemical processes.
- Solar energy.
Does thermal energy affect the environment?
Thermal energy does not directly affect the environment. However, its obtaining and use influences.
During the combustion of fossil fuels, carbon dioxide (CO2) and polluting emissions are released. Nuclear power involves other drawbacks: it generates nuclear waste.
In addition other aspects must be taken into account:
- The land use of these plants.
- Risks of contamination by other accidents. For example, in spills of petroleum or derived petrochemicals.
How is heat energy used?
Thermal energy can be transformed by a thermal engine or mechanical work. For example, a car, plane, or ship engine.
The heat energy is used in the following ways:
- Directly in applications where heat is required. For example, heating.
- Conversion into mechanical energy. For example, in combustion engines.
- Transformation into electrical energy. For example, in thermal power plants.
Conversion of heat energy into mechanical energy
By heating a gas to a constant volume, the average kinetic energy of the particles that compose it increases. At the same time, the heated gas increases the pressure on the walls of the container that contains them.
The gas has acquired potential energy at the macroscopic level. Then the gas can expand and be able to do mechanical work. For example, in thermal machines.
The potential energy acquired by the gas is due to the thermal energy supplied to it. The increase in thermal energy implies an increase in internal energy and in temperature.
Conversion of heat energy to electricity
Caloric energy can be transformed into other forms of energy, for example, it is transformed into electricity or electrical energy.
This conversion is done in:
- Conventional thermal power plants. They use fossil fuels (coal, oil, or natural gas).
- Nuclear power plants. They are nuclear power plants. They use uranium and plutonium.
- Geothermal power plants. They get the heat from inside the Earth.
- Thermal solar power plants. Heat energy is obtained naturally. It is obtained from solar radiation.
Units of measurement
Energy is measured in Joules (J) according to the SI of measurements. They are the same units that are used to measure energy.
However, when it comes to heat energy, calories (lime) are also often used. A calorie is the amount of energy it takes to raise a centigrade to a gram of water. One calorie equals 4.18 joules.