The reclassification of energy sources for electrical energy

To fulfill energy demand, especially electricity, the world is moving toward the usage of clean and sustainable energy sources. The market share of fossil fuels is diminishing year by year, and for renewable sources, it is vice versa. This transition’s main focus is zero emission and sustainability. The present carbon emissions of the world based on reliable sources account for 57 giga tons of carbon equivalents (GtCO2e) (Olivier et al., 2017). At present, the power sector emissions account for around 20 GtCO2e, or 34% of the total emissions. This is associated with a growth rate of 10% since 2010 and a target to decrease by at least 50% by 2030 with around an 8% annual fall rate. This is followed by the steel and industrial sector with 14 GtCO2e or 24%, which has risen by around 15% since 2010. These need to decrease by around ¼ by 2030. Global average direct emission intensity of steel production needs to decrease by around 30% by 2030. Furthermore, the agricultural sector adds about 13 GtCO2e or 22%. Of these, about 7 GtCO2e come from direct, farm-gate emissions with an annual growth rate of 0.6% per year since 2000. These are set to decrease by around 20% by 2030. Emissions by internationally traded agricultural products are about 27%. The transport sector accounts for around 8.7 GtCO2e, or 15% of the total emissions, which has risen by 13% since 2010. These need to decrease by nearly 1/3 by 2030. This can be achieved by 100% zero emission vehicle (ZEV) sales policies by 2035 along with a 10-fold public charging infrastructure by 2030. Carbon emissions are not only limited to commercial sectors but also to buildings and other residential areas of 6% or 3 GtCO2e per year. Although renewable energy sources also emit carbon, their total contribution to carbon emissions is only about 6% or 3 GtCO2e. This confirms the necessity of renewable source adoption for sustainability. The International Renewable Energy Agency (IRENA) aims to become the main driving force in promoting a transition toward the use of renewable energy on a global scale. Also, hydrogen production (which is used as a fuel for IC engines) and use accounts for around 0.9 GtCO2e of emission, or 1.5% of the total emissions. Renewable and low-carbon hydrogen production currently accounts for less than 1% of the total. Targets and commitments to use low carbon and renewable hydrogen are equivalent to 3% of the current total hydrogen demand. This shift of energy production from conventional to sustainable sources explores new methods and sources for producing decarburized energy. Also, the perception toward solar and wind energy as a non-conventional source of energy in this present century may not be right. The emergence of alternative and waste energy recovery technology motivation is reasserting the importance of understanding the present energy scenario (Kapitonov, 2019), (Quaranta and Muntean, 2023). Hence, the new sources and methods are explored to be regrouped necessarily based on their characteristics. This aids in better understanding the nature and role of energy sources. This perspective reclassifies and characterizes energy sources into three main types and newly coined the terms discharged energy source, declining/depleting energy source, and sustainable energy sources. This opinion proposes four criteria for classifying energy in a particular classification. They are carbon neutrality, eco-friendly, nature of availability, and usage at present. The choice of these four criteria is considered because of its crucial role in making energy sources sustainable.