Mechanical engineering including mechanical and chemical engineering. At its simplest, thermodynamics is the study of energy, its use and transformation through a system. Typically, engineering thermodynamics is concerned with changing energy from one form to another. As an example, automotive engines convert chemical energy (enthalpy) from the fuel into heat, and then into mechanical work that eventually turns the wheels. Thermodynamics principles are used by mechanical engineers in the fields of heat transfer, thermofluids, and energy conversion. Mechanical engineers use thermo-science to design engines and power plants, heating, ventilation, and air-conditioning (HVAC) systems, heat exchangers, heat sinks, radiators, refrigeration, insulation, and others.
Energy policy of China has the goal of achieving an integrated nationwide grid in the period between 2015 and 2020. In 2015, China generated 73% of its electricity from coal-fired power stations, which has been dropping from a peak of 81% in 2007. China is the world's leading renewable energy producer, with an installed capacity of 152 GW. China has been investing heavily in the renewable energy field in recent years. In 2007, the total renewable energy investment was $12 billion USD, second only to Germany. In 2012, China invested $65.1 billion USD in clean energy (20% more than in 2011), fully 30% of