SEARCH Articles Figures Tables Clean fuels, from fossil energy sources Combustion in Micro Channels as Energy Source for Fuel Processors Energy fuel source usage Energy fuels Energy sources Energy sources Batteries Fossil fuels Energy sources fossil fuels Energy sources fuel cells Energy sources hydrogen fuel Energy sources source FOSSIL FUELS ARE A WIDELY USED BUT LIMITED ENERGY SOURCE Fossil fuel sources of energy Fossil fuels as energy source Fuel Cells Are Highly Efficient Sources of Electrical Energy Fuels as Sources of Energy Primary Energy Sources—Fossil Fuel Renewable energy sources, fuel cells