The capacity of a physical system to perform work is called energy. There are different types of energy, such as heat energy, mechanical energy, light energy, sound energy and electric energy. Heat energy is produced when there is a transfer of heat from a warm object to a cool object. This is an important form of energy as it is essential for day-to-day activities like cooking, ironing and the heating of water. Any object that can be used to derive heat is considered as a source of heat energy. There are many sources of heat energy.
The sun is a part of our solar system. Thus, it is a natural source of heat energy. Sunlight is important for the existence of all living organisms on the planet. This form of heat energy is also called solar energy.
The heat energy that is found from the Earth is called geothermal energy. Sustainable and clean geothermal energy can be found in the hot water and rocks present in the shallow ground. It is also found in the molten rocks available in the extreme depth of the Earth.
The air around us is a very common source of heat energy for heat pumps. Exhaust air is also a good heat source for heat pumps in buildings, both commercial and residential.
Heat energy can be generated by the burning of fuels. Fuel can be defined as any combustible substance that can burn and provide energy. A few examples of fuels are wood, kerosene, coal, charcoal, gasoline/petrol and oil.
Electricity is a form of energy that can be converted into heat energy, thus, it's considered a source. For example, the clothes iron that is used in our domestic household uses electrical energy to generate heat.
Waste Heat Recovery
Waste heat recovery is a process in which heat energy that is excess for certain industrial processes is diverted to use in other work applications. There are many industrial applications that generate large amount of excess heat. Waste heat recovery boilers are used to channel this excess heat into other useful work applications.
Waste or effluent water is a possible source of heat energy as it has a constant high temperature throughout the year. For example, untreated and treated water from sewers and industrial waste water and condenser heat that is generated from refrigeration plants are used in making of electricity and other industrial processes.