Glossary - Letter E

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The science that deals with the relationships of groups of living things and their environment.


Form of energy resulting from the movement of charged particles (electrons) through a conductor. Electricity is frequently present in nature (lightning, static electricity, nerve impulses, etc.), but this form of electricity cannot be used to meet energy needs. Instead, secondary energy sources known as energy carriers must be produced from primary sources, such as coal, natural gas, heavy fuel oil, nuclear and most renewables.

Electricity mix

Like the energy mix, which describes the part of each primary energy sources in a final energy consumption of a given area, the electricity mix shows the proportion of total electricity generated by each source in a specific region, country, continent or worldwide. These sources include nuclear power, thermal energy (fuel oil, natural gas and coal), hydroelectric power, solar, wind and bioenergies.


Matter is made up of atoms. An atom comprises a nucleus made of protons (positively charged particles) and neutrons (neutral charge), which is orbited by electrons (negative charge). When an atom contains the same number of protons as electrons, it is neutral.

Embodied Energy

Embodied energy is the total amount of energy required to produce a material or industrial product. Unlike the energy consumed directly to use or operate a product, embodied energy is "hidden". It corresponds to the sum of the energy used in a material or product's lifecycle, from extraction and processing to manufacture, transportation, installation, maintenance and recycling. To give a few examples, the embodied energy of a computer is estimated at 6,275 kWh, while that of a 45 kg dishwasher comes to around 1,000 kWh. Looking at cars, a vehicle with an internal combustion engine has an estimated embodied energy of 21,000 kWh, compared with 35,000 kWh for an electric vehicle. The embodied energy of an alkaline battery corresponds to 50 times the energy it stores.

Energy and Climate Change Package

A set of binding legislation that aims to allow the European Union to combat climate change. The first package, adopted in December 2008, sets three key targets for 2020 (the "20-20-20" targets): a 20% reduction in greenhouse gas emissions from 1990 levels; a 20% improvement in the E.U.'s energy efficiency; and raising the share of E.U. energy consumption produced from renewable resources to 20%. The second package, presented by the European Commission in January 2014, sets more ambitious targets for 2030.

Energy Balance

The energy balance of an operation or process is the ratio between the energy available at the end of the operation and the energy used to carry out the operation. It is positive when it is greater than 1. Naturally, energy producers seek a maximum energy balance.

Energy Carrier

A synonym of secondary energy (see definition).

Energy Density

The amount of energy stored in an object, expressed in watt-hours per kilogram (1 Wh/kg = 3.6 kJ/kg). For example, the energy density of a standard rechargeable battery ranges from 70 to 100 Wh/kg. This rises to 150 to 200 Wh/kg for a lithium-ion battery and up to 1,500 Wh/kg for some lithium or manganese batteries. This is far lower than the energy density of a liquid fuel, which is around 10,000 Wh/kg.

Energy Efficiency

In economic terms, energy efficiency refers to the efforts made to reduce the energy consumption of a system (building, factory, infrastructure, extraction method, etc.) while maintaining the same level of performance. It is calculated by dividing the useful energy transferred by the energy supplied.

Energy Independence

The ability of a country or region to meet all its energy needs without having to import primary or final energy.

Energy Mix

The range of energy sources of a region.

Energy Policy

The choices and policy decisions made by a country relating to energy production and consumption. It covers a wide variety of areas such as supply strategy, the energy mix, targeted tax measures, incentives for energy saving, R&D funding, and public awareness initiatives.

Energy Poverty

Refers to the situation of people or communities that do not have sufficient and regular access in their homes or communities to the basic energy or energy services to achieve their day-to-day living requirements. This may be due to factors such as poorly insulated buildings or high energy costs and can have dramatic consequences, such as excess deaths in winter and social isolation. Also called fuel poverty.

Energy Storage

As its name implies, energy storage consists of storing a quantity of energy in a given location in order to use that energy at a later date. The primary goal is to limit energy loss; the secondary goal, to adapt to demand, especially during low production periods. Hydroelectric dams, rechargeable batteries and oil terminals are examples of energy storage.

Energy Transition

Refers to the shift from current energy production systems, which rely primarily on non-renewable energy sources (oil, natural gas and coal), to an energy mix based largely on renewable energy sources.


Describes a building, mode of transportation or industrial process that uses large amounts of energy.

Environmental Impact

Any change to the environment, whether adverse or beneficial, wholly or partially resulting from human activity (projects, processes, products, services, etc.).


Protein or protein molecule that acts as a biological catalyst, i.e. it facilitates a biochemical reaction without interacting with the products of this reaction. Enzymes are essential to the metabolic processes of living organisms. As of early 2012, the website of the European Bioinformatics Institute listed almost 4,600 different enzymes.


EPR™ (European Pressurized Reactor or Evolutionary Power Reactor) is a third-generation pressurized water nuclear reactor designed and developed by France’s AREVA. The reactor is intended for countries with a high power grid capacity and is rated for an electrical power output of 1,650 megawatts — 10 to 40% more than standard pressurized water reactors. France, Finland and China have already started building EPRs, while the United Kingdom is set to follow suit. The reactors will be brought into service in 2020, 2014 and 2023, respectively.

Estimated Energy Consumption

The energy consumption of a building or home can be estimated. This is not the same as documented energy consumption, but is the amount of energy that would be consumed under standard conditions of use in a building. Estimated consumption is calculated based on appliances and utilities (heating, hot water, insulation, etc.). This information can be used to establish an Energy Performance Certificate (EPC).


Ethane is an alkane with two carbon atoms (formula CH3-CH3). It is always found in small amounts with methane in thermogenic natural gas. Ethane is the initial reactant in the synthesis of a number of very important molecules in the petrochemicals industry, including ethylene, vinyl chloride, chloroethane and nitromethane.

Ethyl Tertiary Butyl Ether (ETBE)

A fuel additive produced by the biofuel sector. It is obtained through chemical synthesis in which ethanol is combined with isobutylene in a catalytic reaction.


Ethylene, also known as ethene, is the simplest alkene, or hydrocarbon with carbon-carbon double bonds (formula CH2=CH2). Ethylene is used to produce a wide variety of molecules used in our daily lives, such as ethanol, and numerous polymers and plastics. The list includes polyethylene, polyvinyl chloride (PVC), polystyrene, polyethylene terephthalate (PET), polytetrafluoroethylene (teflon), styrene butadiene rubber (SBR) and styrene butadiene styrene (SBS).

Exploration Portfolio

All of an oil company’s prospects (possible traps) that may contain hydrocarbons. The economic value of the exploration portfolio is weighted according to the probability of discovering deposits in these prospects.