Primary energy

Primary energy sources should not be confused with the energy system components (or conversion processes) through which they are converted into energy carriers. ==Usable energy==

Primary energy sources are transformed in energy conversion processes to more convenient forms of energy that can directly be used by society, such as electrical energy, refined fuels, or synthetic fuels such as hydrogen fuel. In the field of energetics, these forms are called energy carriers and correspond to the concept of "secondary energy" in energy statistics. Conversion to energy carriers (or secondary energy) Energy carriers are energy forms which have been transformed from primary energy sources. Electricity is one of the most common energy carriers, being transformed from various primary energy sources such as coal, oil, natural gas, and wind. Electricity is particularly useful since it has low entropy (is highly ordered) and so can be converted into other forms of energy very efficiently. District heating is another example of secondary energy. According to the laws of thermodynamics, primary energy sources cannot be produced. They must be available to society to enable the production of energy carriers. Source energy, in contrast, is the term used in North America for the amount of primary energy consumed in order to provide a facility's site energy. It is always greater than the site energy, as it includes all site energy and adds to it the energy lost during transmission, delivery, and conversion. While source or primary energy provides a more complete picture of energy consumption, it cannot be measured directly and must be calculated using conversion factors from site energy measurements. However, this can vary considerably depending on factors such as the primary energy source or fuel type, the type of power plant, and the transmission infrastructure. One full set of conversion factors is available as technical reference from Energy STAR. Either site or source energy can be an appropriate metric when comparing or analyzing energy use of different facilities. The U.S Energy Information Administration, for example, uses primary (source) energy for its energy overviews but site energy for its Commercial Building Energy Consumption Survey and Residential Building Energy Consumption Survey. The US Environmental Protection Agency's Energy STAR program recommends using source energy, and the US Department of Energy uses site energy in its definition of a zero net energy building. == Conversion factor conventions==

for the United States 2016 shows that 66.4% of primary energy ends up as waste heat Where primary energy is used to describe fossil fuels, the embodied energy of the fuel is available as thermal energy and around two thirds is typically lost in conversion to electrical or mechanical energy. There are very much less significant conversion losses when hydroelectricity, wind and solar power produce electricity, but today's UN conventions on energy statistics counts the electricity made from hydroelectricity, wind, solar and nuclear as the primary energy itself for these sources. One consequence of employing primary energy as an energy metric is that the contribution of these sources energy is under reported compared to fossil energy sources, and there is hence an international debate on how to count energy from non-thermal renewables, with many estimates having them undercounted by a factor of about two to three. The false notion that all primary energy from thermal fossil fuel sources has to be replaced by an equivalent amount of non-thermal renewables (which is not necessary as conversion losses do not need to be replaced) has been termed the "primary energy fallacy". One method that is used to better account for this is called the substitution method. In this technique the electrical energy produced by these sources is divided by the average energy efficiency of fossil fuel electrical sources. This gives the primary energy that would have been needed if only fossil fuels were employed. == See also ==