 One method is to use the ground as a heat sink by drawing air through underground pipes . This is often done to provide a source of cool air for a building by means of a ground @-@ coupled heat exchanger ( also known as Earth tubes ) , wherein condensation is typically regarded as a significant problem . A major problem with such designs is that the underground tubes are subject to contamination and difficult to keep clean . Designs of this type require air to be drawn through the pipes by a fan , but the power required may be provided ( or supplemented ) by a wind turbine . 
