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 to 2009. However, from 2010 to 2015 China reduced energy consumption per unit of GDP by 18%, and CO emissions per unit of GDP by 20%. On a per-capita basis, it was the world's 42nd largest emitter of greenhouse gases in 2014. China is also the world's largest renewable energy producer. China is the largest producer of hydroelectricity, solar power and wind power in the world. Energy policymaking in China is largely decentralised. There has been no Ministry of Energy since it was dissolved in 1993, and it was only in 2002–2003 that serious governmental dialogue on re-centralising energy administration