This collection deals with some of the topics in Energy and its types with are important for UPSC-CSE examinations. The first topic in these series focuses on calorific value, renewable energy versus non-renewable resources, conventional versus non-conventional energy and the various natures of fuel. After this we learn about green fuel, natural gas: Methane, Propane and Butane, bio fuel - Ethanol and Biodiesel, Biomass gasification and Biochar. The next part of the collection deals with Solar Energy, Wind Energy and Geothermal Energy. Each of those is explained thoroughly along with illustrations. The last few lessons focus on nuclear energy, nuclear fission and nuclear fusion along with the stages of the nuclear energy programme in India.