2024-07-31 22:00:00
This article introduces and sensitizes the reader to the problem ofgray energy or hidden energy (grey energy or embodied energy) objects and processes that are used every day by an individual, industry or services. Indeed, the user is sensitive to the energy he consumes to operate an object, such as his car or his electric heater, but is much less sensitive to the energy that had to be spent to manufacture it, to maintain it (although he often pays for this maintenance) and to get rid of it once it has become unusable or useless. This grey energy is also associated with various impacts on the environment such as the emission of CO2 and pollutants, the creation of waste or the reduction of natural resources.
Defining energy consumption for the use of an object or good is already not an easy thing. This quantity of energy that we callenergy use or ofenergy use (operational energy) is that which is accounted for and paid for directly or indirectly by the user. Defining the amount of gray energy associated with an object, good or service is even more difficult. The consumer most of the time has no idea of the value of this hidden energy. However, the amount of energy to manufacture an object can sometimes be considerable compared to the energy that this object can provide or consume when used. For example, it takes about fifty times more energy to manufacture an alkaline battery than the amount of electricity it provides when used.
Let us recall that theprimary energy corresponds to energy before transformation. This is the case, for example, of crude oil, coal or water from a dam.secondary energy is obtained after transformation: gasoline or diesel from oil, charcoal from wood, electricity from natural gas, etc.final energy is that used by the consumer such as electricity arriving at the home, or domestic fuel oil. Finally, theuseful energy is that actually used for the required use. Between the final energy, which the consumer pays for, and the primary energy, which is used to produce it, significant losses occur. If we consider, for example, the case of French electricity, it took on average about 2.6 kWh of primary energy to produce 1 kWh of electricity consumed by the user.
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