Today the energy world is facing four major challenges: (1) high fuel prices, (2) climatic changes, (3) reduce energy consumption, and (4) investigate alternative energy sources. Fossil fuels still represent over 80% of total energy supplies in the world today, in 2020, but the trend towards new energy sources are clear in the future thanks to the new technological developments. Renewable energy is a promising alternative solution because it is clean and environmentally safe. According to the scenarios, percentage of renewable energy in the total energy produced, between the years of 2010-2040, increased to 16.6 from 47.7. Biomass is the most used renewable energy source now and in future. Geothermal and solar thermal sources are more important energy sources in future. The water energy is converted into electrical energy. Buoyancy of the water can be used as a source of infinite energy by using convenient geometric devices. Gas hydrates are of considerable interest for their potential as an energy resource and for their potential role in global climate change.