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Primary energy (PE) is the energy found in nature that has not been subjected to any human engineered conversion process. It encompasses energy contained in raw fuels and other forms of energy, including waste, received as input to a system. Primary energy can be non-renewable or renewable.
Primary nutritional groups are groups of organisms, divided in relation to the nutrition mode according to the sources of energy and carbon, needed for living, growth and reproduction. The sources of energy can be light or chemical compounds; the sources of carbon can be of organic or inorganic origin.
Food energy is chemical energy that animals (including humans) derive from their food to sustain their metabolism, including their muscular activity. [ 1 ] Most animals derive most of their energy from aerobic respiration , namely combining the carbohydrates , fats , and proteins with oxygen from air or dissolved in water . [ 2 ]
Nuclear energy – energy in the nucleus or core of atoms [1] Nuclear fusion; Nuclear reactor; Nuclear reprocessing; Oil drilling; Oil platform; Oil refinery; Oil shale; Oil well; Osmotic power – or salinity gradient power – is the energy available from the difference in the salt concentration between seawater and river water. OTEC ...
Sunlight's radiant energy is also captured by plants as chemical potential energy in photosynthesis, when carbon dioxide and water (two low-energy compounds) are converted into carbohydrates, lipids, proteins and oxygen. Release of the energy stored during photosynthesis as heat or light may be triggered suddenly by a spark in a forest fire, or ...
An energy carrier can be more valuable (have a higher quality) than a primary energy source. For example 1 megajoule (MJ) of electricity produced by a hydroelectric plant is equivalent to 3 MJ of oil. [4] Sunlight is a main source of primary energy, which can be transformed into plants and then into coal, oil and gas.
Carbon is a primary component of all known life on Earth, and represents approximately 45–50% of all dry biomass. [1] Carbon compounds occur naturally in great abundance on Earth. Complex biological molecules consist of carbon atoms bonded with other elements , especially oxygen and hydrogen and frequently also nitrogen , phosphorus , and ...
Chemical fuels are substances that release energy by reacting with substances around them, most notably by the process of combustion. Chemical fuels are divided in two ways. First, by their physical properties, as a solid, liquid or gas. Secondly, on the basis of their occurrence: primary (natural fuel) and secondary (artificial fuel). Thus, a ...