Final answer:
The largest contributions to the electricity sector are from coal and natural gas, with renewable energies growing but still forming a smaller fraction of the overall mix. Coal, despite its environmental impact, is heavily relied upon due to its availability and high energy content. Moreover, efficiency losses in electricity production present an area for potential improvements.
Step-by-step explanation:
The largest contribution to the electricity sector historically has come from traditional biomass and hydropower, but in more modern contexts, especially pertaining to industrialized nations, the greatest contribution has shifted to fossil fuels, with coal and natural gas being predominant.
In the United States, for instance, coal is responsible for 44% and natural gas for 23% of electricity generation. While renewable energies are making significant strides, coal remains a major player due to its abundance and high energy density, despite its substantial carbon emissions.
It's also important to note that a significant portion of the energy input into the production of electricity is lost due to thermodynamic inefficiencies, meaning that there is substantial room for improvement in the efficiency of electricity generation and distribution.