Uses of energy


The purpose of producting energy is to meet three type of societal needs:
- Mechanical work (electrical equipment);
- Heating supply;
- Heat removal (cooling systems);
Energy does not disappear, it merely changes form. Different forms of energy have different qualities and degrees of usefulness.



Mechanical work
Mechanical work is a highly efficient use of energy that we use to operate machines and carry out work. Heating and Cooling are low-grade use if eneregy. The lower the temperature level required for heating, the lower the physical value or quality of the energy function.

Exergy is the energy that can be actually utilized for mechanical work and all other purpose of energy.
Electric energy is pure exergy - it can, it its entirely, be transformed into mechanical work. Therefore electricity is one means of transporting mechanical work.

Heat for the purpose of heating rooms and maintaining them at a acomfortable temperature is supplied to compensate for the loss of heat to surroundings. No matter how high the temperature may be in the room's heat source, the room temperature remains at the desired temperature level. In other words, the heating of rooms is a use of energy with a very low temperature.


The ability to maintain desired temperatures is one of the most important accomplishments of modern technology. Our ovens, freezers, and homes can be kept at any temperature we choose, a luxury that wasn't possible 100 years ago. Keeping our homes comfortable uses a lot of energy. Over 40 percent of the average home's energy consumption is used for heating. Another 20 percent is used for water heating, 8 percent for cooling rooms, and 5 percent for refrigeration.

Almost one-fourth of the energy used in homes is used for lighting and appliances. Lighting is essential to a modern society. Lights have revolutionized the way we live, work, and play.

Most homes still use the traditional incandescent bulbs invented by Thomas Edison. These bulbs convert only about ten percent of the electricity they use to produce light, the other 90 percent is converted into heat. In 1879, the average bulb produced only 14 lumens per watt, compared to about 17 lumens per watt today. By adding halogen gases, the efficiency can be increased to 20 lumens per watt.

Compact fluorescent bulbs, or "CFLs", have made inroads into home lighting systems in the last few years. These bulbs last much longer and use much less energy, producing significant savings over the life of the bulb.

Appliances such as refrigerators, washing machines and dryers are also more energy efficient than they used to be.


Commercial buildings include a wide variety of building types—offices, hospitals, schools, police stations, places of worship, warehouses, hotels, barber shops, libraries, shopping malls—and that’s just the beginning of the list. These different commercial activities all have unique energy needs but, as a whole, commercial buildings use more than half their energy for heating and lighting.

Types of energy use in comercial buildings

Electricity and natural gas are the most common energy sources used in commercial buildings. Commercial buildings also use another source that you don’t usually find used in residential buildings—district energy. When there are many buildings close together, like on a college campus or in a big city, it is sometimes more efficient to have a central heating and cooling plant that distributes steam, hot water, or chilled water to all of the different buildings. A district system can reduce equipment and maintenance costs, as well as save energy.


The United States is highly industrialized. Industry accounts for about one-third of the energy used in the country.

There are many different uses and a variety of different energy sources in the manufacturing sector. One main use is as boiler fuel, which means producing heat that is transferred to the boiler vessel to generate steam or hot water. Another use is as process heating, which is when energy is used directly to raise the temperature of products in the manufacturing process; examples are separating components of crude oil in petroleum refining, drying paint in automobile manufacturing, and cooking packaged foods.

Types of energy for industry/manufactoring
In the manufacturing sector, the predominant energy sources are natural gas and electricity (a secondary source). Manufacturers also use other energy sources for heat, power, and electricity generation. Many uncommon energy sources are also used by manufacturers as a feedstock(a raw material used to make other products).

Energy use by type of industry

Every industry uses energy, but there are a handful of energy-intensive industries that use the bulk of the energy consumed by the industrial sector.

The chemical industry is the largest industrial consumer of energy, followed closely by petroleum refining. The refining, chemical, paper and metal industries together use:

  • 94% of the feedstock
  • 92% of the byproduct energy
  • 70% of total inputs of energy for heat, power, and electricity generation



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