Search results
Results from the WOW.Com Content Network
Common energy efficiency label on appliances to indicate their energy efficiency in a clear manner. Efficient energy use, or energy efficiency, is the process of reducing the amount of energy required to provide products and services. There are many technologies and methods available that are more energy efficient than conventional systems.
Energy conversion efficiency (η) is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The input, as well as the useful output may be chemical , electric power , mechanical work , light (radiation), or heat .
A premium efficiency electric motor: more than 90% (see Main Article: Premium efficiency). A large power transformer used in the electrical grid may have efficiency of more than 99%. Early 19th century transformers were much less efficient, wasting up to a third of the energy passing through them. [citation needed]
Measurable energy conservation and efficiency gains in the 1980s led to the 1987 Energy Security Report to the President (DOE, 1987) that "the United States uses about 29 quads less energy in a year today than it would have if our economic growth since 1972 had been accompanied by the less- efficient trends in energy use we were following at ...
The theoretical and conceptual basis for the emergy methodology is grounded in thermodynamics [citation needed], general system theory [2] and systems ecology. [3] Evolution of the theory by Howard T. Odum over the first thirty years is reviewed in Environmental Accounting [1] and in the volume edited by C. A. S. Hall titled Maximum Power.
Energy (from Ancient Greek ἐνέργεια (enérgeia) 'activity') is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat and light.
For energy-conversion heating devices their peak steady-state thermal efficiency is often stated, e.g., 'this furnace is 90% efficient', but a more detailed measure of seasonal energy effectiveness is the annual fuel use efficiency (AFUE).
A human achieves the lowest cost of transport when walking at about 6 kilometres per hour (3.7 mph), at which speed a person of 70 kilograms (150 lb) has a metabolic rate of about 450 watts. [1] This gives a dimensionless cost of transport of about 0.39.