How Does Energy Happen?

What is energy?

Energy can be defined as the capacity to do work or produce heat. In physics, energy is an abstract quantitative property that is transferred between objects or systems when they interact. Energy comes in many forms such as kinetic, potential, thermal, gravitational, sound, light, chemical, nuclear and more.

There are two main types of energy: potential energy and kinetic energy. Potential energy is stored energy that objects possess due to their position or chemical configuration. Examples include gravitational potential energy from an object’s height, elastic potential energy stored in a compressed spring, and chemical potential energy from the bonds between atoms in molecules. Kinetic energy is energy associated with motion. Examples include the kinetic energy of an object moving at a certain velocity, the random motion of molecules in a gas, and the electrons moving through a wire.

The law of conservation of energy states that the total energy in an isolated system remains constant. Energy can only be transferred between objects or systems, and can be converted between different forms, but it cannot be created or destroyed. Potential energy can be converted to kinetic energy and vice versa.

Where does energy come from?

Energy comes from a variety of natural sources in our world. Some of the main sources of energy include:

Solar Energy

The sun radiates an enormous amount of electromagnetic energy in the form of sunlight. This solar energy drives many processes on Earth, providing the heat and light that sustains most life on the planet. Solar energy is harnessed through various technologies like solar panels which convert sunlight into electricity.

Chemical Energy

Chemical energy comes from the bonds between atoms and molecules in substances. When these chemical bonds are broken or formed, energy is absorbed or released. Examples of stored chemical energy include fossil fuels like coal, oil, and natural gas. The energy stored in food through photosynthesis is also a form of chemical energy.

Nuclear Energy

Nuclear energy comes from processes that convert matter into energy within the nucleus of an atom. Nuclear fission of heavy elements like uranium and plutonium releases energy that can be harnessed to generate electricity. The fusion of light elements like hydrogen also releases massive amounts of nuclear energy, as occurs in the sun.

Gravitational Energy

Gravitational energy comes from the pull of gravity exerted across cosmic distances. The gravitational force of the moon causes tides on Earth. Hydropower is another example of using gravity’s pull on water to generate electricity.

Mechanical Energy

Mechanical energy arises from the motion and position of objects. The kinetic energy of a moving object like wind or flowing water can be captured through turbines and converted into electricity. Objects high above the ground have potential energy that can be tapped by allowing them to fall.

How is energy captured and converted?

There are a variety of processes that can capture and convert energy from one form to another. Some key examples include:


Plants, algae, and some bacteria capture light energy from the sun and convert it into chemical energy stored in sugars and other organic compounds through the process of photosynthesis. This conversion of light energy into chemical energy is essential for almost all life on Earth.


Animals are able to capture chemical energy stored in the organic matter they eat and convert it into forms their bodies can use through the process of cellular respiration. This involves breaking down nutrients through digestion and using them to fuel body functions.


Batteries are able to convert chemical energy into electrical energy through electrochemical reactions. As two different chemicals interact via oxidation and reduction reactions, electrons flow through an external circuit, producing electricity.


Generators are able to convert various forms of mechanical energy into electrical energy. For example, water turbines convert the kinetic energy of moving water into electricity through electromagnetic induction. Similarly, wind turbines and gas turbines use the kinetic energy of wind and expanding gases to generate electricity.

How do living things use energy?

Living organisms like plants and animals need energy to survive and function. At a cellular level, the energy used by organisms is in the form of a molecule called adenosine triphosphate or ATP. ATP provides the chemical energy that powers the majority of cellular processes. It acts like the “energy currency” of the cell, transferring energy from where it is generated to where it is consumed.
atp provides chemical energy to power cellular processes

ATP is continuously regenerated from adenosine diphosphate (ADP) and phosphate, allowing it to be reused. This regeneration of ATP happens through processes like photosynthesis in plants or cellular respiration in animals. These processes convert energy from sunlight or food sources into chemical energy in ATP.

The energy stored in ATP then drives key cellular activities like muscle contraction, nerve impulse transmission, chemical synthesis, and cell division. ATP is able to power these processes by giving up one of its phosphate groups, releasing energy in the form of heat. This heat energy is harnessed to do work inside the cell. The resulting ADP is then recharged by replenishing its phosphate group to repeat the cycle of energy release and use.

Beyond the cellular level, living organisms also need energy flows at the ecosystem level. Energy enters most ecosystems from the sun, through a process called photosynthesis in plants, algae, and some bacteria. These organisms convert solar energy into chemical energy, which is then passed on and transformed as it moves through food chains and food webs.

Herbivores get energy by eating plants, omnivores and carnivores get energy by eating other animals, and decomposers get energy by breaking down dead organic matter. Energy is passed on and transformed from one trophic level to the next. Only about 10 percent of the energy is transferred to each successive level, as the rest is lost as heat. The continued flow and transformation of energy makes life possible in ecosystems.

How do machines use energy?

Machines rely on energy to perform work and operate their components. Some common types of machines and how they use energy include:

Engines – Whether fueled by gasoline, diesel, or other fuels, engines convert chemical energy in the fuel into mechanical energy through combustion. This energy powers the moving components in the engine and drives the wheels or propellers on a vehicle or boat.

Motors – Electric motors convert electrical energy into mechanical energy through electromagnetic interactions. They power fans, pumps, tools, appliances, and factory machinery.

Turbines – Turbines use flowing energy sources like air, water, or steam to spin rotors connected to generators that produce electricity. Examples include gas turbines, hydroelectric turbines, and wind turbines.

Pumps – Pumps move fluids like water or oil by converting mechanical energy into pressure energy and kinetic energy in the fluid flow. They are powered by electric motors or engines in many applications.

Machines expand human capabilities to perform work, but still obey the conservation of energy. The energy input to machines is converted to useful work output as well as wasted as heat and other byproducts.

How is energy transported?

Energy transportation refers to the processes and infrastructure used for moving energy from where it is generated to where it can be used. There are several major ways that energy is transported:

Electric grids – Electricity grids transmit power from electricity generation sites like power plants to homes, businesses and other end users. These grids consist of an interconnected network of transmission and distribution lines, substations, transformers and other equipment to control voltage and direct power flows.

Pipelines – Pipelines transport various energy resources in liquid or gas form like petroleum, natural gas, and biofuels. Extensive pipeline networks span countries and even continents to transport these energy resources from wells, production facilities, storage hubs and seaports to destinations where they are refined or consumed.

Physical transport – Energy sources like coal, petroleum, wood, and biofuels are often transported in bulk via rail, truck, barge or ship to get them to market. Vessels and vehicles specially designed for hauling these cargo enable massive quantities of energy resources to be moved efficiently.

Energy transportation is a vital link between producers and consumers of energy. Developing and maintaining the proper infrastructure allows energy to be accessed reliably and affordably across various geographies and distances.

How is energy stored?

Energy can be stored for later use in a variety of ways:

Batteries store chemical energy and convert it into electrical energy. They contain two terminals and an electrolyte paste. Chemical reactions in the battery separate positive and negative charges, storing the energy until it is needed. When the circuit is completed, the chemical reactions drive electrons from the negative to the positive terminal, producing electricity.

Fuel tanks and cylinders store liquid and gaseous fuels. Gasoline, diesel, propane, and natural gas all contain chemical energy that can be released through combustion. This stored chemical energy is easily transported for later use.

Dams store energy by using electric pumps to move water into an elevated reservoir. The gravitational potential energy can later be converted into kinetic energy and electricity by allowing the water to flow down through turbines.

Chemical bonds within molecules and compounds store energy that can be released through chemical reactions. Foods like fats and sugars contain energy stored in the bonds between atoms that is released when the molecules are broken down during digestion or combustion.

Batteries, fuels, dams, and molecules all allow energy to be stored in a stable state until we need to use it for work and electricity.

What happens to energy when work is done?

When energy is used to do work, the total amount of energy in the universe remains the same. This is known as the law of conservation of energy. While energy cannot be created or destroyed, it can be transformed from one form into another. For example, when an engine burns gasoline, chemical energy in the fuel is converted into heat and kinetic energy that powers the vehicle. Even though the chemical energy seems to disappear, it has simply changed form.

Often, some energy is lost or wasted when it is converted from one form to another. For instance, when gasoline is combusted in a car engine, not all of the chemical energy is transformed into useful kinetic energy. Some is lost as heat and sound energy, which dissipates into the environment. This lost energy is called waste heat. It represents an efficiency loss, since less work can be done than the total energy theoretically available.

All real-world energy conversions contain some inefficiency resulting in waste heat and energy dispersal. While 100% efficiency is possible in theory, it is unattainable in practice. There will always be some energy leaks and losses. However, through thoughtful design and engineering, the efficiency of energy systems can be dramatically improved to minimize wasted energy.

How can energy use be made more efficient?

There are several ways we can increase efficiency and reduce energy waste in homes, transportation, industry and infrastructure. Some key methods include:


Insulating buildings better reduces heating and cooling requirements dramatically. Insulation in walls, roofs, floors and around pipes and ductwork prevents heat loss in winter and heat gain in summer. Proper insulation lowers energy bills and improves comfort.

Regenerative braking

In vehicles, regenerative braking captures kinetic energy when braking and uses it to charge batteries instead of wasting that energy as heat. Hybrid and electric vehicles use regenerative braking to extend range.

LED lighting

LED bulbs require far less electricity and last much longer than incandescent and CFL lights. Replacing old bulbs with LEDs reduces lighting energy use by 50-70%. LED streetlights are also more efficient and reduce light pollution.

The Future of Energy

As concerns about climate change and energy independence grow, there is increasing focus on developing new energy technologies and infrastructure that are renewable, sustainable, and efficient. Key areas of innovation and development include:

Renewable Energy

Renewable energy sources like solar, wind, geothermal and hydropower are rapidly expanding as costs decrease. With renewable energy incentives, supportive policies, and growing private sector investments, renewable energy could provide over half of global electricity by 2050, replacing fossil fuels and lowering greenhouse gas emissions.

Nuclear Fusion

Nuclear fusion promises nearly limitless clean energy by fusing light atomic nuclei like hydrogen rather than splitting heavy nuclei like uranium. After decades of research, fusion experiments are now achieving important milestones, with commercial fusion power possible by 2040 if progress continues.

Smart Grids

Upgrading power grids with advanced sensors, controls, and software enables two-way communication between utilities and customers, optimizing energy distribution and coordinating demand with variable renewable supplies. Smart grids boost efficiency and integration of renewables.

Energy Storage

As renewable energy grows, energy storage technologies like batteries, compressed air, pumped hydro, and hydrogen will be key to provide grid stability and reserve power. Continued cost reductions and innovations in battery storage will facilitate more renewables.

Other Innovations

From advanced biofuels to AI-enabled “smart buildings” to new heating technologies, researchers are exploring many promising new ways to produce, store, distribute and conserve energy in a clean, efficient, and economical manner. Ongoing innovation in energy technologies will be crucial for transitioning to a sustainable energy future.

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