The commercial sector consists of retail stores, offices (business and government), restaurants, schools and other workplaces. Energy in this sector has the same basic end uses as the residential sector, in slightly different proportions. Space conditioning is again the single biggest consumption area, but it represents only about 30% of the energy use of commercial buildings. Lighting, at 25%, plays a much larger role than it does in the residential sector. Lighting is also generally the most wasteful component of commercial use. A number of case studies indicate that more efficient lighting and elimination of over-illumination can reduce lighting energy by approximately fifty percent in many commercial buildings.
Commercial buildings can greatly increase energy efficiency by thoughtful design, with today's building stock being very poor examples of the potential of systematic (not expensive) energy efficient design (Steffy, 1997). Commercial buildings often have professional management, allowing centralized control and coordination of energy conservation efforts.
Solar heat loading through standard window designs usually leads to high demand for air conditioning in summer months. An example of building design overcoming this excessive heat loading is the Dakin Building in Brisbane, California, where fenestration was designed to achieve an angle with respect to sun incidence to allow maximum reflection of solar heat; this design also assisted in reducing interior over-illumination to enhance worker efficiency and comfort.
The industrial sector represents all production and processing of goods, including manufacturing, construction, farming, water management and mining. Increasing costs have forced energy-intensive industries to make substantial efficiency improvements in the past 30 years. For example, the energy used to produce steel and paper products has been cut 40% in that time frame, while petroleum/aluminum refining and cement production have reduced their usage by about 25%. These reductions are largely the result of recycling waste material and the use of cogeneration equipment for electricity and heating.
The energy required for delivery and treatment of fresh water often constitutes a significant percentage of a region's electricity and natural gas usage (an estimated 20% of California's total energy use is water-related.) In light of this, some local governments have worked toward a more integrated approach to energy and water conservation efforts.
Unlike the other sectors, total energy use in the industrial sector has declined in the last decade. While this is partly due to conservation efforts, it's also a reflection of the growing trend for U.S. companies to move manufacturing operations offshore.
The usage of telecommuting by major corporations is a significant opportunity to conserve energy, as many Americans now work in service jobs that enable them to work from home instead of commuting to work each day.
Cogeneration
Cogeneration (also combined heat and power, CHP) is the use of a heat engine or a power station to make both electricity and useful heat at the same time.
Conventional power plants emit the heat created as a byproduct of electricity generation into the environment through cooling towers, as flue gas, or by other means. Combined heat and power captures the byproduct heat for domestic or industrial heating purposes, either very close to the plant, or - especially in Scandinavia and eastern Europe - for distribution through pipes to heat local housing.
Byproduct heat at moderate temperatures (100 to 180°C) can also be used in absorption chillers for cooling. A plant producing electricity, heat and cold is sometimes called regeneration or more generally: polygene ration plant.
Cogeneration is a thermodynamically efficient use of fuel. In separate production of electricity some energy is lost as waste heat, but in cogeneration this energy performs useful work (see energy).
Thermal power plants (including those that use fissile elements or burn coal, petroleum, or natural gas), and heat engines in general, do not convert all of their available energy into electricity. In most heat engines, a bit more than half is wasted as excess heat (see: Second law of thermodynamics). By capturing the excess heat, CHP uses heat that would be wasted in a conventional power plant, potentially reaching an efficiency of up to 70%, compared with at most 40% for the conventional plants. This means that less fuel needs to be consumed to produce the same amount of useful energy. Also, less pollution is produced for a given economic benefit.
An exact match between the heat and electricity needs rarely exists. A CHP plant can either meet the need for heat ("heat driven operation") or be run as a power plant with some use of its waste heat.
CHP is most efficient when the heat can be used on site or very close to it. Overall efficiency is reduced when the heat must be transported over longer distances. This requires heavily insulated pipes, which are expensive and inefficient; whereas electricity can be transmitted along a comparatively simple wire, and over much longer distances for the same energy loss.
A car motor becomes a CHP plant in winter, when the reject heat is useful for warming the interior of the vehicle. This example scores the point that deployment of CHP depends on heat uses in the neighbourhood of the heat engine.
Cogeneration plants are commonly found in district heating systems of big towns, hospitals, prisons, oil refineries, paper mills, wastewater treatment plants, thermal enhanced oil recovery wells and industrial plants with large heating needs.
Quakenbrück
Quakenbrück is a small town in Lower Saxony. It has about 13,000 inhabitants.
Dew point
The dew point is the temperature where water vapor condenses into liquid water.
All air holds different amounts of water vapor. The dew point shows the amount of moisture in the air. The higher the dew point is, the higher the level of moisture in the air at a given temperature. The dew point of humid air will be higher than the dew point of dry air.
Condensation of water vapor starts when the temperature of air is lowered to its dew point and beyond. The dew point, like other measures of humidity, can be found from measurement taken by a hygrometer.
Podgorica
Podgorica () is the capital of Montenegro. In 2011, the population was 185,937.
Región Autónoma del Atlántico Sur
The Región Autónoma del Atlántico Sur is an independent part of Nicaragua. It is often simply known as RAAS. Its capital is Bluefields. It was made when new regions were formed in Nicaragua in 1989. The old region was turned into Atlántico Sur and Atlántico Norte. The capital of Atlántico Norte is Puerto Cabezas. There is also a popular tourist place called Corn Island, which is about 45 km from the capital Bluefields
Región Autónoma del Atlántico Norte
Región Autónoma del Atlántico Norte is an autonomous region of Nicaragua. It was created in 1989. Its capital is Puerto Cabezas. Often the name is shotened to RAAN.
Compressor
Compressor could mean:
Gas compressor
A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume. Compression of a gas naturally increases its temperature. When the gas is air, the machine is called an air compressor.
Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas. Liquids are relatively incompressible, so the main action of a pump is to transport liquids.
There are many different types of gas compressors. The two primary categories are:
The more important types in each of the four sub-categories are discussed below.