There are different ways in which people try to deal with the problem of energy. One way is the greater production of common energy sources, such as coal, oil and gas. The trouble with these sources, however, is that they are not renewable( ). Another way is energy conservation( ), which means using energy more efficiently. In some very cold countries, people build special houses to save energy. They place materials between the inside and outside of the walls of the house to keep the cold out and the warmth in. Finally, renewable energy sources are used even though they are often expensive to develop. One form of these is geothermal energy( ). In certain parts of the world, the temperature of the earth increases thirty degrees centigrade( ) with each kilometer down. At six kilometers, therefore, it rises to nearly two hundred degrees. Heat from the earth is already used in some countries. Four different ways of dealing with energy problems are talked about in the passage.