Environmental Engineering Reference
In-Depth Information
Owing to the introduction of these systems, between 1990 and 2007, the effi-
ciency of thermal electricity generation with natural gas increased from 34% to
42% on average. Coal electricity generation did not benefit from these gains and
efficiency stayed practically constant because the equipment in use in most devel-
oping countries has not been modernized. For oil, efficiency has likewise stayed
practically constant.
Chinese and Indian plants using coal are the least efficient with efficiencies
around 20%. By comparison, Japan's thermopower plants had already achieved
a 36% average efficiency by 1965. By 2004, Japanese thermopower plants had
reached an average efficiency of 40% and some of its units had efficiencies of up
to 52%. Denmark had a 36% average efficiency in 1960 and 52% in 2000.
Energy in buildings is required in two ways:
Operating energy
(usually called direct) is the energy needed to operate the ser-
vices and amenities in buildings, including thermal comfort, refrigeration, illumin-
ation, communication and entertainment, sanitation, and others. The cost of oper-
ating energy ends up in the monthly bill for energy services.
Embodied energy
(usually called indirect) is the energy needed for the produc-
tion and transportation of the materials used in construction, the manufacturing of
furniture and appliances, and the provision of infrastructure services such as water
and sanitation. Embodied energy is highly dependent on the design and construc-
tion technique of buildings.
One can try to make buildings more efficient either by investing more in the
construction phase to reduce the embodied energy or by investing heavily in more
efficient appliances to reduce other energy consumption in the operation of the
building. Over a 50-year life-cycle direct energy in the OECD building sector ac-
counts for 84% of the energy used in OECD countries which means that in each
year as much as 15% of the sunk energy is consumed in the operation of the build-
ing. This amount is even higher in some industrialized countries and lower in de-
veloping countries.
In the European Union space heating accounts for the single largest use of en-
ergy. Buildings account for up to two-thirds of total energy use in the cold regions
of China and in the former Soviet Union. Lighting sometimes accounts for the
largest single use of electricity in commercial buildings, although in hot climates,
air conditioning tends to be the single largest use of electricity.
