Historical overview of the efficiency of utilized energy sources

Throughout human history, the efficiency of energy conversion devices has been crucial. The increase in humanity's energy consumption makes the efficiency of energy conversions crucial. In the Neolithic era, humans used about 3,500 kcal (14.6 MJ) per day, while modern people in developed countries use around 250,000 kcal (1,046 MJ) daily. Over approximately 10,000 years, our energy consumption has increased more than seventyfold. The rapid development of industry, household and agricultural automation, advances in transport technology, and widespread use of telecommunication constantly introduce new energy consumers. However, the rapidly growing demand for energy is outpacing the existing explored reserves of available energy sources, leading to concerns about resource depletion in many areas. There is a growing call to shift focus from fossil fuels to climate-neutral and renewable energy sources. As electrification becomes more widespread, the need for electrical energy is increasing, presenting us with numerous new challenges. Consequently, establishing new energy principles and formulating new (energy) strategies are necessary. This paper analyses energy conversion efficiency across historical periods, focusing on recent trends. Based on the results, we can assert that if this trend continues, we can achieve more efficient energy conversion systems.