Thermal energy is the energy released in the form of heat. It can also be called heat energy. In a more technical way we can define thermal energy as part of the internal energy of a thermodynamic system in equilibrium that is proportional to its absolute temperature and is increased or decreased by energy transfer.
The thermal energy can be transformed using a thermal engine (a thermoelectric power plant uses thermal energy to generate electricity); or in mechanical work (for example, a car, airplane or ship engine).
The obtaining of thermal energy can imply an environmental impact. If thermal energy is obtained by certain sources of non-renewable energy such as, for example, by combustion of fossil fuels, or nuclear energy, the environmental impact is negative.
During the combustion of fossil fuels, carbon dioxide (CO2) and polluting emissions are released. On the other hand, the use of nuclear energy also brings other drawbacks: this source of energy generates radioactive waste that must be controlled. In addition, the use of land from power generation plants and the risks of contamination due to accidents in the use of the materials involved, such as oil spills or petrochemical derivatives must be taken into account.
On the other hand, thermal energy can be obtained through renewable energy sources such as solar thermal energy. Solar thermal energy can capture solar radiation and convert it into energy through solar collectors.
Heat energy can be obtained in several ways:
- It can be obtained directly from nature. It would be the case of geothermal energy or solar thermal energy.
- Energy generated from chemical energy,
- It can be obtained by an exothermic reaction, like the combustion of some fossil fuel.
- Thermal energy can be generated through a reaction of fission nuclear energy or nuclear fusion energy. By splitting the nucleus of an atom a large amount of heat is obtained.
- Energy generated by electrical energy by Joule effect or by thermoelectric effect
- Thermal energy due to friction, as a residue of other mechanical or chemical processes.
Conversion of thermal energy to other forms of energy
Thermal energy or heat energy can be converted to other types of energy. The main forms of energy conversion are conversion into mechanical energy and conversion to electrical energy.
Conversion of heat energy into mechanical energy
Heating a gas to a constant volume increases the average kinetic energy of the particles that make it up. At the same time, the heated gas increases the pressure on the walls of the container that contains them. At this moment the gas has acquired potential energy, at a macroscopic level, and thus it can, eventually, expand and be able to perform mechanical work as commonly happens in thermal machines such as thermal engines or steam engines.
The potential energy acquired by the gas is due to the thermal energy supplied to it. The acquisition of thermal energy by the gas is confirmed by the fact that the gas increases its temperature. If the gas can expand, it does a job and, therefore, consumes some of the energy it has acquired and cooled down.
Conversion of heat energy to electricity
This conversion of thermal energy into mechanical energy is carried out in thermoelectric and thermonuclear power plants. The thermoelectric plants gas is heated by burning fossil fuels (usually coal or natural gas). In thermonuclear plants the gas is heated by the use of nuclear energy. They are also known as nuclear power plants. Both types of plants use steam in the energy conversion process.
Another type of plants capable of generating electricity are geothermal power plants and thermodynamic solar power plants. In these cases the thermal energy is obtained naturally. In geothermal energy heat is obtained from the interior of the Earth. In thermal solar energy the heat energy is obtained from solar radiation.
Obtaining thermal energy through solar radiation
Solar radiation can be converted into thermal energy by different methods. Solar thermal energy these applications. Below, 3 examples: The solar oven, solar collectors and solar power plants.
The solar oven is a larger number of mirrors, controlled by computer according to the movement of the sun, so that the incident rays are reflected in the central concave mirror, which is the common focal point. At the focal point, the temperature can rise to 4000 ° C. This thermal energy is already useful for melting metals, heating ovens or water ( solar thermal power plants).
Solar collectors. The solar collectors are blackened aluminum panels that absorb solar radiation and convert it into heat through a closed circuit of water. In single-family homes in favorable geographical positions, 90% of the hot water needs can be met (heating of apartments and swimming pools, sanitary water). In less warm places, said energy recovery is economic only if it replaces the electricity consumption.
Solar power plant: solar thermal energy plants concentrate solar radiation at a point with the help of mirrors. At this point concentrates a large amount of thermal energy that is used to generate steam. Turbines are activated with the steam generated, converting thermal energy into mechanical energy. Turbines will generate electricity in a way similar to how nuclear power plants or thermal power plants do.
The differences between these three types of power plants are in the fuel they use to obtain thermal energy: solar energy, nuclear energy through the fission of uranium atoms and the combustion of fossil fuels respectively.
Thermal energy measurement unit
The units for measuring thermal energy are the same units that are used to measure energy since it is still a form of energy.
Energy is measured in Joules (J) according to the international system. Although when it comes to calorific energy calories are also commonly used (lime). A calorie is the amount of energy that is needed to raise one gram centigrade of water. A calorie equals 4.18 joules.
Last review: April 13, 2017