Primary and Secondary Energy

Primary Energy : Primary energy sources are those that are either found or stored in nature. Common primary energy sources are coal, oil, natural gas, and biomass (such as wood). Other primary energy sources available include nuclear energy from radioactive substances, thermal energy stored in earth's interior, and potential energy due to earth's gravity. The major primary and secondary energy sources are Coal, hydro power, natural gas, petroleum etc. Primary energy sources are mostly converted in industrial utilities into secondary energy sources; for example coal, oil or gas converted into steam and electricity. Primary energy can also be used directly. Some energy sources have non-energy uses, for example coal or natural gas can be used as a feedstock in fertilizer plants.

The human factor is not mentioned in UN or OECD/IEA/Eurostat manual definitions. In defining primary energy it may not be necessary to include this, but for secondary energy it can be useful for separating natural energy transformation and human-made energy transformation.

For primary energy the important distinguishing characteristics is the process of extraction or capture. Primary energy is extracted or captured from sources, and through this extraction and capture, the physical and chemical characteristics of the energy is not changed. For example hard coal which is extracted from the ground. It is only cleaned and separated from rocks and other non-energy substances, but the physical and chemical property of the energy in the hard coal itself is not changed. As specified in the UN definition, cleaning, separation and grading of the energy components in a source, is not an energy transformation process, and the energy in hard coal is therefore not secondary energy.  

 

For secondary energy the important distinguishing characteristics is the process of transformation. Energy transformation is any process of transforming one form of energy to another. Energy of fossil fuels, solar radiation, or nuclear fuels, which are all primary, can be converted into other energy forms such as electricity and heat that are more useful to us. All energy that has been subjected to human-made transformation is secondary energy. Figure 1 gives a schematic illustration of primary versus secondary energy

The purpose of the activity of extraction, capture or transformation is to make the energy available for trade and use. Extraction and collection from energy sources can also be used for non-energy purposes. This aspect is only stressed in the definition of primary energy suggested by Tim Simmons for Inter Ener Stat. Based on these points, and as a starting point for discussion, we have a proposal for a new definition of primary energy: “Primary energy is energy embodied in sources which involve human induced extraction or capture, that may include separation from contiguous marital, cleaning or grading, to make the energy available for trade, use or transformation” For secondary energy, a proposal for a new definition: “Secondary energy is energy embodied in commodities that comes from human induced energy transformation”