I. Introduction
Because of the population increase and the industrialization energy demand cannot be covered with a finite energy sources, difference between energy production and consumption is growing rapidly. On the other hand, traditional energy production methods today are seen as one of the major causes of environmental pollution. In addition, it is an unavoidable reality that fossil fuels will run out in time. As a result of industrial activities each year about 20 billion tons of carbon dioxide, 100 million tons of sulfur compounds, 2 million tons of lead and other toxic chemical compounds are released into the atmosphere [1].