Environmental Engineering Reference
In-Depth Information
capacity is nonetheless rather high. With about 2650 TWh produced, nearly
17 per cent of the electricity demand was supplied by hydro-electric power
plants in 2001. This share will probably decrease slightly over the coming
decades because the potential for new hydro power plants is limited.
Geothermal power
is also important for some national electricity markets.
In Iceland, El Salvador and the Philippines, geothermal power plants produce
about one fifth of the total electricity. A total of 8.3 GW has been installed
worldwide and produced about 50 TWh of electricity by 2003.
Combustible
biomass
and waste are the second most important renewable
energy resource for electricity generation today; however, no reliable figures
about global use are available. The annual electricity production from biomass
is of the order of 150 TWh.
Use of renewable energy sources for heat and fuel
production
Although the potential of
solar thermal collector systems
is enormous, their
contribution to the global primary energy supply is still rather low. Assuming
70 million m
2
of installed glazed collectors by the end of 2001 and an average
heat production of 600 kWh/m
2
, the total global solar thermal heat production
was about 150 PJ. This is equal to 0.04 per cent of the global primary energy
demand. China is by far the world's largest solar water heater manufacturer
and user. By the end of 2002, the accumulated installed area of solar domestic
hot water systems in China was about 40 million m
2
. Greece had a noticeable
installed area per capita of 264 m
2
per 1000 inhabitants by 2001. Projecting
these per capita numbers to the global population, the total installed area
would increase more than 20 times. Table 1.15 shows the number of
installations of the countries with the most significant solar collector markets.
Due to its frequent non-commercial use in developing countries, solid
biomass is by far the largest renewable energy source, representing 10.4 per
cent of world total primary energy supply, or 77.4 per cent of global
renewables supply in 2001. Africa covers about 50 per cent of its energy supply
by biomass; some countries such as Mozambique or Tanzania have even higher
figures of more than 90 per cent. High growth rates have been experienced by
non-solid biomass combustible renewables and waste, such as renewable
municipal solid waste, biogas and liquid biomass. This segment grew annually
on average at 7.6 per cent since 1990. These growth rates are expected to
continue even in industrial countries.
Geothermal energy
is also used for heat production. However, the global
share is relatively low. In the long term,
hydrogen
produced by renewable
energy sources could achieve a significant share. However, since production
costs of hydrogen are very high, it will take several decades to have a noticeable
impact on world energy supply.
