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The Greening of IT
272 How Companies Can Make a Difference for the Environment

power equipment. Equipment such as parking meters or wireless
Internet gateways can be powered by a wind turbine that charges a small
battery, replacing the need for a connection to the power grid.
References: See the large list of reference at http://en.wikipedia.org/
wiki/Wind_power.

Worldwide Aspects of Solar Power

From Table C.2, solar power supplies less than 1 percent of global
electricity demand. The term solar energy refers to the utilization of the
radiant energy from the Sun. Solar power is used interchangeably with
solar energy but refers more specifically to the conversion of sunlight
into electricity, either by photovoltaics and concentrating solar thermal
devices, or by one of several experimental technologies such as thermo-
electric converters, solar chimneys, or solar ponds. Because solar power,
along with wind power, are the alternative power-generation methods
currently receiving most attention, this section gives an overview of
worldwide development of this power source. Much of the following ptg
information comes from the Web site http://en.wikipedia.org/wiki/
Solar_energy.
The Earth receives 174 petawatts (PW) of incoming solar radiation
(insolation) at the upper atmosphere. Approximately 30 percent is
reflected back to space while the rest is absorbed by clouds, oceans, and
land masses. The spectrum of solar light at the Earth’s surface is mostly
spread across the visible and near-infrared ranges with a small part in the
near-ultraviolet.
Solar radiation along with secondary solar resources, such as wind and
wave power, hydroelectricity, and biomass, account for more than 99.9
percent of the available flow of renewable energy on Earth. The total
solar energy absorbed by Earth’s atmosphere, oceans, and land masses is
approximately 3,850 zettajoules (ZJ) per year. In 2002, this was more
energy in one hour than the world used in one year. Photosynthesis
captures approximately 3 ZJ per year in biomass. The amount of solar
energy reaching the surface of the planet is so vast that in one year, it is
about twice as much as will ever be obtained from all the Earth’s
nonrenewable resources of coal, oil, natural gas, and mined uranium
combined.