Abstract
Human beings are the only species able to harness energy for their use from different natural sources known as fuel. Hydrocarbon-based fossil fuels are considered a prime source of energy due to their high energy density and the availability of mature energy-conversion technologies. However, as the sources of fossil fuels are becoming depleted due to excessive exploration and use, the need to upgrade energy-conversion efficiency has become vital. Moreover, reducing greenhouse gas emission from fossil fuel energy conversion is also an issue. On the other hand, although renewable energy resources are plentiful and environmentally friendly, there is a lack of capable technology to harness and convert renewable energy to ensure its efficient and cost-effective application. This chapter aims to introduce readers to the available energy-conversion technologies for extracting energy from fossil fuels as well as from renewable energy sources. Unconventional technologies like waste-to-energy, magneto-hydrodynamics, and thermionic energy conversion are also discussed. A brief treatment regarding energy efficiency is also included to focus its profound importance in modern energy industry to ensure best energy utilization.