Definition of temperature: The temperature is the thermodynamic magnitude that shows the thermal energy of one body in relation to another.
Although the definition of temperature is simple and concise, you can explain what the temperature is in a more extensive way: What is the temperature?
Temperature is a physical quantity of matter that quantifies the common notions of heat and cold. The objects of low temperature perceive them cold, while objects of higher temperatures we consider them warm or hot. This physiological sensation of cold and heat is generated…
The Kelvin is the temperature unit of the International System. The Kelvin is one of the seven basic units of temperature. Its symbol in the international system of units is K. The Kelvin scale is a thermodynamic (absolute) temperature scale where the absolute zero, the theoretical absence of energy, is zero (0 K). This unit is named after the British physicist, mathematician and engineer William Thomson (1824 - 1907), who was later named Lord Kelvin. Lord Kelvin wrote about the need for a "thermodynamic temperature scale".
To express the temperature difference or the interval, the use…
In physics, in particular in thermodynamics, heat is defined as the contribution of transformed energy as a result of a chemical or nuclear reaction and transferred between two systems or between two parts of the same system. This energy is not attributable to a job or a conversion between two different types of energy. Heat is, therefore, a form of transferred energy and not a form of energy contained as internal energy.
As the energy is exchanged, the heat is measured in the International System in joules. In practice, however, it is often still used as the unit of measurement of calories,…
Geothermal energy is a type of renewable energy on a human scale that is obtained from the heat of the interior of the Earth. Equestrian thermal energy can be obtained without the combustion of any material, it is therefore a form of clean energy without carbon dioxide emissions.
The temperature in the inner layers of the Earth remains constant during the different seasons of the year. Generally the inner layers are hotter than the surface in winter and cooler in summer. This is because the surface layers are heated and cooled more easily according to the laws of thermodynamics.…
Low-temperature solar thermal installations are considered those installations of solar thermal energy that provide useful heat at temperatures below 65 ° C through solar energy.
A low-temperature solar thermal installation consists of solar collectors, two water circuits (primary and secondary), heat exchanger, accumulator, expansion vessel and pipes.
The circulation of water inside the circuits can be obtained by thermosiphon, taking advantage of the density difference of the water at different temperatures or by means of a circulation pump. Although with a circulation…
In thermodynamics, an isothermal process is a thermodynamic transformation at constant temperature, that is, a variation of the state of a physical system during which the temperature of the system does not change with time. Devices called thermostats can maintain a constant temperature value.
The isothermal transformation of a perfect gas is described by Boyle's law which, in a pressure-volume diagram (or Clapeyron's plane), is represented by a branch of the equilateral hyperbola. Isotherm of a perfect gas Calculation of heat and work exchanged
For isothermal gas…
The flat plate thermal solar collector has a good cost / effectiveness ratio in moderate climates and adapts correctly to a large number of applications (hot water heating, pool heating, heating support, preheating industrial fluids, etc.).
We can distinguish two basic types of flat plate collectors, depending on the configuration of the absorber: the "grid type" parallel, in the vertical and horizontal versions and the "serpentine type" series. Basically, the difference between the two is:
- The parallel configuration favors that the temperature of the collector can be stratified…
The Fahrenheit degree (° F) is a temperature unit proposed by Gabriel Fahrenheit in 1724.
On the Fahrenheit scale, the melting point of water is 32 degrees of temperature, and the boiling point is 212 degrees. A difference of 1.8 degrees Fahrenheit equals that of 1 degree Celsius. Fahrenheit established the zero temperature (0 ° F), the freezing point of a 50% mixture of salt (ammonium chloride) and ice, and as 96 ° F, he took the temperature of the blood (he used that of the horses ). The figure 96 may seem an odd measure, but in principle the scale contained only twelve…
Geothermal energy is a long-term source of energy worldwide. With the geothermal energy stored in the top three kilometers of the Earth's crust, theoretically, the current energy demand could be covered for more than 100,000 years. However, only a small part of this energy is technically usable and the effects on the earth's crust during extensive heat dissipation are not yet clear.
When geothermal energy is used, a distinction is made between direct use, that is, the use of heat in itself, and indirect use, the use for conversion into electricity in a geothermal power plant. With the…
A solar thermal collector is a component of a solar thermal installation. A solar collector is a type of solar panel responsible for capturing solar energy and transforming it into heat. It is also called the solar thermal collector.
The solar collector is the basic element of this renewable energy source.
From solar collectors there are many types. The solar collector used will depend on the use that is going to be given. For example, if we want to heat a pool to a temperature of 25-28ºC, in the spring, we need a simple sensor, since the ambient temperature will easily be…
The solar thermal energy consists of the use of energy from the Sun to transfer it to a medium that carries heat, usually water or air.
Among the different applications of solar thermal energy there is the possibility of generating electric power. The current technology allows to heat water with solar radiation to produce steam and subsequently obtain electrical energy.
Although the principle of operation is very similar there are two main applications of solar thermal energy:
- Thermal single energy for use in homes and small installations
- Large thermal solar…
Thermodynamics is the branch of classical physics that studies and describes the thermodynamic transformations induced by heat and work in a thermodynamic system, as a result of processes that involve changes in the temperature and energy state variables.
Classical thermodynamics is based on the concept of macroscopic system, that is, a portion of physical mass or conceptually separated from the external environment, which is often assumed for convenience that is not disturbed by the exchange of energy with the system. The state of a macroscopic system that is in equilibrium conditions…
One of the applications of solar thermal energy is the obtaining of sanitary hot water (ACS). Solar collectors capture the energy of solar radiation to increase the temperature of a fluid.
Domestic hot water (DHW) is water intended for human consumption (potable) that has been heated. It is used for sanitary uses (bathrooms, showers, etc.) and for other cleaning uses (washing dishes, washing machine, dishwasher, floor scrubbing). In terms of energy, the ACS is an important component to take into account, since it represents between 25 and 40% of the energy consumption of homes.
What is entropy? Entropy (S) is a thermodynamic quantity originally defined as a criterion for predicting the evolution of thermodynamic systems.
Entropy is a function of extensive character state. The value of entropy, in an isolated system, grows in the course of a process that occurs naturally. Entropy describes how a thermodynamic system is irreversible.
The meaning of entropy is evolution or transformation. The word entropy comes from the Greek. Entropy in the world of physics
In physics, entropy is the thermodynamic magnitude that allows us to calculate the…
The third law of thermodynamics, sometimes called Nernst's Theorem or Nernst's Postulate, relates the entropy and the temperature of a physical system.
The third law of thermodynamics states that absolute zero can not be achieved in a finite number of stages. The third law of thermodynamics can also be defined as that when reaching absolute zero, 0 degrees Kelvin, any process of a physical system stops and when reaching absolute zero the entropy reaches a minimum and constant value.
This principle states that the entropy of a system at the absolute zero temperature is a well-defined…
The zero law of thermodynamics speaks of what we experience every day: two systems that are in thermal equilibrium with a third are in equilibrium with each other. It is said that two bodies are in thermal equilibrium when, on contacting each other, their state variables do not change. Around this simple idea the zero law is established.
Every law of physics has its relevance, as well as the zero law of thermodynamics, which curiously was the last law to be introduced in literature. After the realization that heat is a form of energy that could be transformed into another, thermology…
In the autonomous electricity supply facilities, it is necessary to store the energy captured during the hours of solar radiation in order to cover supply during the hours when there is no (daily cycle and seasonal cycle).
- Electric batteries have a very important and fundamental to the proper functioning and duration of a solar photovoltaic installation function.
- They must have sufficient capacity to ensure supply of electricity during periods of clouds (autonomy of installation).
- It is reversible electrochemical systems…
For the conversion of fossil energy into electrical energy, the technology of a thermal power plant is often used. At the moment in which a thermal power station is fossil fuels fossilized from a source of non-renewable energy generation.
A thermal power plant (or thermoelectric plant) is a plant that generates electricity by transforming heat. Historically heat energy is converted into electricity by transferring heat to a working fluid and then transforming the energy of this fluid into mechanical energy. Finally, mechanical energy is transformed into electricity. The…
In engineering a heat exchanger (or simply an exchanger) is an apparatus in which thermal energy is exchanged between two fluids that have different temperatures.
From the thermodynamic point of view, heat exchangers can be assimilated to open systems that work without exchanging work; in other words, they exchange matter and heat with the outside, but they do not exchange jobs.
In the solar thermal industry the heat exchanger is used to transfer the heat captured through the solar radiation that is found from fluid that circulates through the solar collectors to another…
Thermal temperature is the absolute measure of temperature and is one of the main parameters of thermodynamics. Its unit of measure in the international system of measures is the Kelvin.
This is an "absolute" scale because it is the measure of the fundamental property of temperature: its zero value, or absolute zero, is the lowest possible temperature. There is nothing that can have a temperature below absolute zero. The absolute zero of the thermodynamic temperature, transformed in the Celsius scale would be equal to 273,5ºC. This characteristic is defined by the third law of thermodynamics…
We refer to hight-temperature solar thermal to those collectors who work at temperatures above 500 ° C. They are used for power generation.
The technologies used in hight-temperature solar thermal energy are:
Parabolic trough solar collectors…
- Parabolic trough solar collectors
- Central tower
- Parabolic dishes or parabolic reflector
- Linear Fresnel concentrators
These equipments have a natural circulation based on convection currents formed in the fluid at different temperatures.
If we heat a water tank at the bottom when the bottom water warms, it becomes less dense and rises to the surface where it cools. Then returns to the bottom of the container and thus a natural circulation flow is generated.
This is the operating principle of a thermosiphon team, which will be essential that:
- The solar collector (heat sources) is always located below the level of the accumulator.
- The primary circuit is as short as possible…
Low-temperature solar thermal energy is used in applications that require temperatures between 100ºC and 250ºC. From 80ºC the flat collectors practically no longer have any performance and it is necessary to resort to other capture systems.
Low-temperature thermal energy systems are used mainly for applications that demand thermal energy, that is, heat between 125º C and 400º C. To reach higher temperatures it is necessary to concentrate the solar radiation.
For this type of solar thermal energy, two types of solar collectors are used:
Passive solar energy is based on the use of solar energy without the need to use external support mechanisms. By these mechanisms we refer to the use of electric motors to orient solar panels or similar systems.
The objective is to obtain personal thermal comfort. Personal thermal comfort is a function of personal health factors (medical, psychological, sociological and situational), ambient air temperature, average radiant temperature, air movement (thermal sensation, turbulence) and relative humidity (which affects human evaporative cooling).
To use passive solar energy…
The geothermal heat pump is an air conditioning system for buildings that exploits the heat exchange with the superficial subsoil, by means of a heat pump. Since the heat in the subsoil comes largely from the interior of the Earth, geothermal energy of low enthalpy is classified as a source of renewable energy, although the heat pump itself consumes electricity, generally produced from other sources of energy (for example, fossil fuels).
The heat pump allows the exchange of heat between a "source" at a lower temperature than the "well", or the point where the heat is introduced. In a…
In thermodynamics, an isobaric process is a change in the state of a certain amount of matter in which the pressure does not change, but one or more of its state variables. An example of this is air in a cylinder with a freely movable piston to which heat is supplied. Due to the increase in temperature, the volume will increase, but the pressure will remain constant.
The isobaric process is governed by Charles's law. The Frenchman Jacques A. Charles (1742-1822) was the first to make measurements about gases that expand when their temperature increases. Examples of isobaric processes…
The degree Celsius or degree Celsius (in symbol in ° C), is the unit of a temperature measurement scale, named after the Swedish astronomer Anders Celsius (1701 - 1744), who proposed it for the first time in 1742.
The Celsius scale fixes the melting point of ice in a mixture of water saturated with air at 0 ° C and the boiling point at 99.974 ° C under standard pressure conditions (1 bar, a little less than one atmosphere, pressure in the one that the water boils at 100 degrees centigrade).
Originally conceived by the Celsius scale had the boiling point of water at…
An adiabatic process is a thermodynamic process in which the system does not exchange heat with its surroundings. An adiabatic process may also be isentropic, which means that the process may be reversible.
The adiabatic process provides a rigorous conceptual basis for the theory used to expose the first law of thermodynamics and, as such, is a key concept in thermodynamics.
The term adiabatic refers to elements that impede the transfer of heat with the environment. An isolated wall is quite close to an adiabatic limit. Hence the adiabatic wall term appears.
A process that…
A thermodynamic process is the evolution of certain properties, which are called thermodynamic properties, in relation to a particular thermodynamic system. In order to study a thermodynamic process, it is required that the system be in thermodynamic equilibrium at the initial and final point of the process; that is, that the magnitudes that undergo a variation when passing from one state to another must be completely defined in their initial and final states.
In this way thermodynamic processes can be interpreted as the result of the interaction of one system with another…
The first law of thermodynamics was announced by Julius Robert von Mayer in 1841. It is the principle of conservation of energy.
Definition of the first law of thermodynamics: The total energy of an isolated system is neither created nor destroyed, it remains constant. Energy only transforms from one type to another. When one energy class disappears, an equivalent quantity of another class must be produced.
A body can have a certain speed with what has kinetic energy. If it loses speed, this kinetic energy that it loses becomes another type of energy, whether it is potential energy…
Geothermal energy is the discipline of Earth Sciences that studies the set of natural phenomena involved in the production and transfer of heat or thermal energy from within the Earth.
In a broad sense, the geothermal concept can also be extended to the study of other planets. Its principles are exploited at a technological level in the production of electricity and cogeneration through geothermal power plants from the associated geothermal energy. The origin of earth's heat from a geothermal
The heat of the Earth's core was originally generated during the accretion of…
The Sun is a star around which the Earth turns.
It has an approximate diameter of 1,400,000 km and a mass of 1.99 × 1033 g.
The Sun revolves around itself. However, since it is constituted by a large mass of gases, the different regions do not rotate in solidarity, but they do so at different speeds, which depend on latitude.
The Sun, and with it the entire solar system, moves towards a point in the firmament located in the constellation of Hercules at a speed of about 19 km / s. This is because the Sun has a movement of translation around the galactic center, like…
The batteries in a photovoltaic solar energy system is to accumulate the energy produced by the photovoltaic panels during the hours of Sun to be able to use it at night or on cloudy days.
The use of batteries also allows to provide a higher current intensity than a functioning photovoltaic panel can offer. This would be the case if several electrical appliances were used at the same time.
A battery consists of small 2V accumulators integrated in the same element; Has direct current at 6, 12, 24 or 48V. The accumulator is the cell that stores energy through an electrochemical…
The efficiency of photovoltaic cells is one of the elements that determine the production of a photovoltaic solar energy installation. The other factors that determine the performance of a solar plant are latitude and climate.
The conversion efficiency value of a photovoltaic cell depends on several factors. When we refer to conversion efficiency, we refer implicitly to the thermodynamic efficiency, to the separation efficiency of the load carrier, to the reflectance efficiency and to the values of conduction efficiency. These parameters are difficult to measure…
Geothermal energy is a renewable energy obtained from the heat stored inside the Earth. Thanks to the laws of thermodynamics, thermal energy is transferred from the interior of the Earth to a fluid. In this way, energy is transported in the form of internal energy.
Geothermal energy is basicaly based simply on taking advantage of the fact that the subsoil temperature is warmer than on the surface, in winter, and instead cooler, in summer. This is a consequence of the fact that the surface layers of the Earth are heated and cooled much more easily than the interior, which is maintained…
In this section we intend to answer the main questions related to solar energy.
Generally, these are general topics that could be located in several sections of the web. Our intention is to expand this section in the future to publish generalist articles and curiosities of nuclear energy.
Most of the questions are focused on small solar installations, comparative with solar thermal energy and photovoltaic solar energy.
In the future we will also answer on more oriented questions in the field of physics: thermodynamics, forms of energy, mechanical energy, potential energy,…
A forced circulation for solar water heater is an installation in which the water circulates inside the circuit driven by a pump. With forced circulation system, the movement of water in the closed circuit is forced by a pump. This feature makes a big difference with respect to sanitary hot water installations with thermosyphon. In this way, it artificially moves the hot water not to the highest point of the closed circuit, but it does so from the solar collectors down to where the accumulator is located.
In many occasions it is not viable to install solar thermal equipment…
Renewable energy is that energy that comes from practically inexhaustible natural sources. They are considered inexhaustible either because of the large amount of energy they contain or because they can be regenerated naturally.
Among the main advantages of renewable energies we highlight the following:
Renewable energies are respectful with the environment and do not pollute.In this sense, they are safer and pose fewer health risks than other sources of non-renewable energy.
In most cases they are simple to dismantle and it is not necessary to guard their waste, as it…
A solar collector of evacuated tubes is a type of solar panel that uses solar thermal energy. The finality of solar collectors is converting solar radioation into thermal energy.
This renewable solar energy system uses a type of solar panel consisting of linear collectors housed in evacuated glass tubes.
The evacuated tube solar collector consists of a set of cylindrical tubes. The tubes are formed by a selective absorber, located on a reflector settlement and surrounded by a transparent glass cylinder.
The vacuum has been made between the transparent outer tube and…
In thermodynamics, the internal energy is the total energy contained in a thermodynamic system.
The internal energy is the energy that is needed to create the system. According to this definition, the energy to displace the environment of the system, any energy related to external force fields (potential energy, gravitational energy, etc.) or any energy associated with the movement (for example, kinetic energy) is excluded from the internal energy. .
The internal energy of a system can be modified by exercising a work on it or by heating it (providing thermal energy). If we look…
The Stirling engine was invented in 1816 by Robert Stirling, a Scottish priest. The goal was to get a less dangerous engine than the steam engine.
The operation of the Stirling engine is based on the expansion and contraction of a gas that can be helium, hydrogen, nitrogen or air. This gas is forced to cycle cyclically from a cold source where it contracts to a hot source where it expands. It is considered as a thermal engine (thermodynamic engine) due to the presence of a temperature gradient between the two thermal sources.
Originally, the Stirling engine was conceived as an…
At the end of the 17th century, the Earth was conceived as a molten mass with a solid crust as a result of its cooling. It was not until the 19th century that the first calculations of the age of the Earth based on its thermal evolution were drawn up, and the term geothermal was first defined as the scientific discipline that studies earth's heat, origin of this heat, distribution and use.
Precisely, the use of this thermal energy is what has led to the development of geothermal energy. Geothermal energy allows us to take advantage of the heat energy inside the Earth in different applications,…
Geothermal energy is that energy that can be obtained by man through the use of heat from the interior of the Earth. This type of energy has many applications. One of these applications is the generation of electric power.
The generation of electricity from geothermal energy is a good complement for hydroelectric plants, which also has the advantage that it is constant throughout the year. Geothermal plant
Geothermal power plants are the plants responsible for converting geothermal energy into electricity. A geothermal plant is a facility where electricity is generated…
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially, using the energy of solar radiation.
Photosynthesis occurs in plants, algae, and some groups of bacteria, but not in archaea. Photosynthetic organisms are called "photoautotrophs," but not all organisms that use light as an energy source effect photosynthesis, since "photoheterotrophs" use organic compounds, not carbon dioxide, as a carbon source. In plants, algae and cyanobacteria, photosynthesis uses carbon dioxide and water, releasing oxygen as a waste product. photosynthesis is crucial…
In thermodynamics an adiabatic wall is a wall that does not allow the transfer of heat from one side to another. An adiabatic wall does not let out or enter any heat.
Adiabatic walls are theoretical concepts because if in case tehey would exist they would be a perfect thermal insulation. At present, any thermal insulation, however good it may be, always allows some transfer of heat energy. Adiabatic process
An adiabatic process is a process in which the system does not exchange heat with its surroundings. An isentropic process is an adiabatic process that is also reversible.…
The greenhouse effect is the process by which the atmosphere of a planet passes solar radiation from the Sun, but instead prevents or hinders the thermal energy output of the planet.
It is called greenhouse effect due to the similarity with the operation of the greenhouses that are able to retain the heat inside. The operation is not exactly the same, but it is very similar. The difference is that the greenhouse uses the glass and not the gases in the atmosphere to retain heat. That is why this natural phenomenon has been called the greenhouse effect.
When we talk about the greenhouse…
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…
In electricity, the rated voltage of an electrical device is the voltage that must not be exceeded in normal operation. The nominal adjective is because that tension usually serves to characterize the device, to name it. The nominal value indicates the theoretical or ideal value of anything that can be quantified, as opposed to the real value, which is what is obtained in a given measurement.
Another definition of rated voltage: The rated voltage is the specific potential difference for which a device or installation is designed.
As it is a nominal value it implies that the voltage…
A solar accumulator is a reservoir that separates the energy supply from the energy capture. That is, because we will not always need energy at the moment of solar radiation, the compiler is entrusted to store this energy to supply it when needed.
For this, the accumulator stores thermal energy from the solar collectors.
When the system needs, for example, domestic hot water the accumulator supplies this hot water and replaces it with cold water that comes from the network. The cold water will pass through the circuit of solar collectors exposed to solar radiation and increase…
A thermodynamic system is a portion of the material space, separated from the rest of the thermodynamic universe (that is, from the external environment) by means of a real or imaginary control surface (or edge), rigid or deformable.
A thermodynamic system can be the seat of internal transformations and exchanges of matter and / or energy with the external environment (that is, everything external to the system that interacts with it). Classification of thermodynamic systems
Within thermodynamics there are three main types of thermodynamic systems: open, closed and isolated.…
A solar thermal power plant or thermosolar power plant is an industrial facility in which solar radiation is used to generate electricity. Solar radiation is used to heat a fluid. Using fluid, taking advantage of the laws of thermodynamics, the necessary power is produced to move an alternator to generate electrical energy as in a classic thermoelectric power station. Operation of a solar thermal power station
The operation of a solar thermal power plant is based on obtaining heat from solar radiation and transferring it to a heat carrier medium. This heat carrier is usually…
Within the history of solar energy, in one form or another, solar energy has always been present in the life of the planet being this imprescidible for the development of life. However, the way in which human civilization has exploited it invented new strategies and tools has undergone a long evolution.
The Sun is indispensable for the existence of life on the planet: it is responsible for the water cycle, photosynthesis, etc. Already the first civilizations realized this and, as civilizations have evolved, they have also evolved techniques to harness their energy. At the beginning they…
The function of a solar thermal installation is to take advantage of solar energy to generate heat. The solar panels of these facilities capture the heat of the solar radiation that falls on them to heat a fluid. The different ways to take advantage of this hot fluid allows us to use this type of renewable energy in multiple applications.
A solar thermal installation consists of:
- Solar collectors
- Primary and secondary circuits
- Heat exchanger
- Accumulator, pumps
- Glass of expansion
- Main control panel.
A thermodynamic property is a characteristic or a particularity that allows the changes of the work substance, that is to say, changes of energy.
The thermodynamic properties can be classified as intensive and extensive. They are intensive those that do not depend on the amount of matter of the system (pressure, temperature, composition). Extensive ones depend on the size of the system (mass, volume).
The thermodynamic variables are the magnitudes that we consider necessary or convenient to specify to give a macroscopic description of the system. Most of these magnitudes…
Thermodynamics is mainly based on a set of four laws that are universally valid when applied to systems that fall within the constraints implicit in each.
The first principle that was established was the second law of thermodynamics, as formulated by Sadi Carnot in 1824. The 1860 already established two "principles" of thermodynamics with the works of Rudolf Clausius and William Thomson, Lord Kelvin. Over time, these principles have become "laws." In 1873, for example, Willard Gibbs claimed that there were two absolute laws of thermodynamics in his graphical methods in fluid thermodynamics.…