Energy balance
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Energy balance has the following meanings in several fields:
- In physics, energy balance is a systematic presentation of energy flows and transformations in a system. Theoretical basis for an energy balance is the first law of thermodynamics according to which energy cannot be created or destroyed, only modified in form. Energy sources or sinks of energy are therefore inputs and outputs of the system under observation.
- In biology, total body energy balance is measured with the following equation: Energy intake = internal heat produced + external work + energy storage
- In energy economics, the energy balance of a country is an aggregate presentation of all human activities related to energy, except for natural and biological processes. National energy balances are compiled on at least annual basis. Common methodology for compilation and presentation of energy balances allows simple addition of national energy balances to form supranational ones, such as is compiled for the European Union. United Nations compile energy balances for all member countries. International Energy Agency, a specialised agency of OECD is regularly preparing world energy balances.
- When comparing fuel production, energy balance is the difference between the energy produced by a 1 kg of the fuel (i.e. biodiesel, petroleum, uranium ) and the energy necessary to produce it ( extraction (e.g. drilling or cultivation of energetic plants), transportation, refining etc). Other factors affect fuel selection, such as portability. See also net energy gain