Thermal energy is a type of power produced by atomic and molecular particle movement within a substance. It was first discovered in 1847 by English physicist and mathematician James Prescott Joule, after whom the unit of energy and Joule’s Law are named.
Joule came across thermal energy when experimenting with mechanical energy conversion. Both mechanical energy and thermal energy rely heavily on kinetic energy, or the energy of motion.
Joule realized that the more he manipulated the speed of a substance, the higher temperature it became. Because of this, thermal energy is often referred to as heat energy, but the two terms are not exactly the same.
In this article, we’ll discuss thermodynamics, what thermal energy is, and how it relates to internal energy and gas. We’ll also talk about how heat works, why thermal energy is important, and how it affects our environment.
What Is Thermodynamics?
The relationship between heat and thermal energy has been studied extensively and is referred to as thermodynamics or the study of energy transformation.
Thermodynamics is structured around four laws:
- The zeroth law states that should one of two systems with equal heat flow encounter a third system; all three systems will share equal heat flow.
- The first law of thermodynamics is also referred to as the Law of Conservation of Energy. This law dictates that energy cannot be created or destroyed. The heat from a source will equal the heat used in a system, and only heat energy can be changed into other forms of energy.
- The second law of thermodynamics states that no closed system will ever remain the same. The entropy of an isolated system will always increase. Entropy is a quantity that represents the absence of a system’s thermal energy for conversion into mechanical work; it is also understood as the degree of randomness in a system. Interacting systems of different temperatures will experience heat flow until both temperatures become the same. A higher temperature system will transfer heat until it is equal to that of the cooler object. For example, a cube of ice will not get colder, but rather, as it interacts with the system of its warmer surroundings it will melt, eventually becoming the same temperature as its environment.
- The third law of thermodynamics tells us that the entropy of a thermal energy system will obtain a constant value when temperatures reach absolute zero.
According to the Energy Information Administration, Joule’s Law is “The rate of heat production by a steady current in any part of an electrical circuit that is proportional to the resistance and to the square of the current, or, the internal energy of an ideal gas depends only on its temperature.”
What Is Thermal Energy and How Does It Relate to Internal Energy?
Thermal energy is one of six basic forms of energy. They are:
- Chemical energy
- Nuclear energy
- Radiant energy
- Mechanical energy
- Electrical energy
- Thermal energy
The terms thermal energy and heat energy are often used interchangeably as they both involve power created by heat.
However, thermal energy refers to the stored or total internal energy of a system‘s temperature, while heat represents thermal energy transfer.
Temperature is the average kinetic energy inside an object. It is commonly measured globally by three scales: Fahrenheit (F), Celsius(C), and Kelvin(K).
The total kinetic energy of molecules combined with the potential energy of atoms while in motion is called internal energy.
Internal energy is the kinetic energy and the potential energy of the system as a whole.
Internal energy uses the same system of units as energy – the joule.
The joule is the international system of units for energy and work and is equal to the work used to generate enough force to propel a moving object a distance of one meter.
If a thermodynamic system is in a state of thermal equilibrium, it will contain internal energy.
The system’s internal energy will function as a variable. Thus, the internal energy change will equal the heat transfer input and the work generated by a system’s operation.
What Is Heat Energy and How Is It Different From Thermal Energy?
A better understanding of the differences between thermal energy, temperature, and heat energy emerges from thermodynamics.
Heat energy is the transfer, vibrational movement, or flow of thermal energy.
As mentioned above, thermal energy is the total energy of a system — it accounts for all of the particles a substance contains.
The average kinetic energy of those particles — the moving energy — is temperature.
Heat and temperature are different. Heat energy can flow between substances when there is a constant temperature, also known as latent heat.
Heat content is often measured in British thermal units (Btu). A Btu amount reflects fuel and energy source heat content.
More specifically, it tells us the amount of heat needed to make one pound of water rise in temperature by 1°F (-17.22°C) when in a liquid state and at peak density.
This temperature sits around 39°F (33.88889°C).
The Btu (one Btu equals about 1,055 J) is used because it’s part of an international system of units (also known as a SI unit) in which heat content and energy can be measured, regardless of an object’s original state of measurement.
How Does Heat Energy Transfer Work?
Heat energy can move from hot objects, liquids, gases, or spaces to cooler ones through three methods of transfer: conduction, convection, and radiation.
Conduction is when heat passes through solid material to increase the temperature of whatever is beyond it.
A good example of this is when the sun and outdoor temperature heats the body of a car, and then, in turn, the temperature inside the vehicle rises.
Convection happens when heat is transferred by fluid movement, also known as mass motion of a fluid substance. Convection will only be initiated if the temperatures of the surface of an object and the fluid, solid or gas are different.
An example of this is cold water that rises in temperature to become hot water.
Radiation is the transference of heat in the form of light. Heat transfer by way of light can be both visible and nonvisible. Radiative heat can pass through a vacuum, gas, or liquid, any of which can reflect or move the radiation.
Common examples of heat radiation include sunlight or fire.
What Is the Ideal Gas Law And What’s It Got to Do With Thermal Energy?
The ideal gas law is based upon empirical mathematics and took over 200 years to solve.
It begins with the basic formula that as the pressure of a gas increases, its volume will decrease by a proportional amount.
It was also found that temperature and volume share a similar relationship: as a gas’ temperature increases, the volume of the gas will increase by a proportional amount.
Then it was discovered that the higher amount of molecules a gas contains, the more volume it will have and that the two will be of equal proportion.
These three tenets were combined, and the result was the ideal gas law: PV=nrt. In other words, constant pressure to constant volume is equal to the product of the number of moles, temperature, and universal gas constant (R). The universal gas constant value is approximately R=8.3 J/kcal/mol — that’s 8.3 joules per mole per kelvin (K).
The ideal gas law predicts observed pressure and temperature change behaviors and relationships at a basic level.
Though it is not a good indicator of what will happen in extreme realities, it affords scientists predictions based on approximate, hypothetical models – hence, the “ideal” terminology.
Why Is Thermal Energy Important?
Thermal energy offers us another source of power. Thermal energy is used in thermal power plants.
Thermal energy can be efficiently stored and used as a backup power source during peak usage hours or seasonal weather power use increases.
Thermal energy allows us to use the energy produced by the Earth to our advantage. This type of thermal energy is called geothermal energy (Earth’s heat). This is considered a renewable source of power because the Earth continuously produces heat and replenishes any heat extracted or used.
Geothermal technologies allow us to use Earth’s heat to power heating and cooling systems. The three most common types of geothermal technology include direct use geothermal systems, deep and enhanced geothermal systems, and ground source heat pumps.
What Is Thermal Energy Storage and Why Do We Need It?
Thermal energy storage can occur in two different ways.
The first is by altering the way thermal energy is absorbed or released — either as latent or sensible heat (types of heat transfer).
Latent heat relates to the phase changes of liquids, solids, and gases.
Sensible heat has to do with the temperature of an object or gas, independent of the state of a phase change.
Thermal energy can also be stored by conducting chemical reactions.
This process introduces heat to certain chemicals, which eventually separates them into separate reactive components and allows them to store energy.
Thermal energy can also combine with renewable energy sources — for example, storage of rejected or diverted solar power.
Reducing renewable energy waste through thermal energy storage makes certain renewable energy sources even more efficient; thermal energy shows great promise in reducing greenhouse gas emissions and promoting sustainability.
How Can We Avoid Thermal Energy Pollution?
Thermal energy shows promising solutions to a growing need for power because of its ability to store energy to be used later.
Thermal energy sources are fossil fuels like natural gas, coal and oil, as well as solar heat, heat pump electric heat, and geothermal heat.
Though thermal energy has relatively few negative impacts on the environment, a few issues need to be tended to before being considered a truly green source of power.
Thermal energy can produce pollution. This pollution is often in the form of escaped chemicals or water released in thermal power plants or storage sights.
Air and water pollution may also be linked to geothermal fields. For example, steam may emit heat waste that might affect cloud formations and weather patterns.
The release of hot or cold water by these thermal energy sources into natural bodies of water such as ponds, streams, and rivers can create a temperature difference and hinder the ecosystem.
Prevention of thermal water pollution can be targeted by monitoring water temperatures and changing them closer to the water’s natural temperature.
Effluent treatments can also prevent thermal pollution. Effluent treatments require that wastewater be stored in ponds or reinjected into wells.
Thermal Energy: A Great Natural Resource
Thermal energy is a useful source of power that the world provides. Not only can thermal energy be employed in conjunction with other renewable energy sources, but it provides backup power, energy storage, and efficient heating and cooling alternatives.
As planet Earth continues to experience global warming, thermal energy will become more essential than ever — and it can take the heat.
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