Energy engineering is a broad field of engineering dealing with areas such as energy harvesting and storage, energy conversion, energy materials, system, energy efficiency, energy services, facility management, plant engineering, energy modeling, environmental compliance, sustainable energy, and renewable energy technologies. Energy engineering is one of the most recent engineering disciplines to emerge. Energy engineering combines knowledge from the fields of physics, math, and chemistry with economic and environmental engineering practices. Energy engineers apply their skills to increase efficiency and further develop renewable sources of energy. The main job of energy engineers is to find the most efficient and sustainable ways to operate buildings and manufacturing processes. Energy engineers audit the use of energy in those processes and suggest ways to improve the systems.