With a total primary energy supply of more than 11 billion tons of oil equivalent (Btoe) recorded in 2004, the world energy market is a 3 trillion dollar business per year and it is expected to rise significantly over the next decades (EIA 2006). Since energy is essential for the present way of life and any threat to its supply is of major importance to the well being of a country, the energy sector is not a commercially driven market. Regulations and restrictions are established in almost every country to conform the energy market to social and political requirements. To ensure the continuity of energy supply, a country cannot be entirely dependent on just one power source and, consequently, a strategic mix of different energy sources is always present. Since the First World War, the main source of energy has come from oil and gas, which today represents 62 percent of the total world energy consumption (see Figure 4.1). However, conventional forms of energy—in particular fossil fuel—create pollution that damages the environment, its natural resources and the health of its inhabitants. Burning coal for instance—which accounts for 26 percent of total world energy consumption—releases about 1 Kg of CO2 per kWh1 in the atmosphere. In 2004 global CO2 emissions were 26,583 million tons (EIA 2006).