by Er moses.j
Renewable
energy is
energy which comes from
natural resources such as
sunlight,
wind,
rain,
tides, and
geothermal heat, which are
renewable (naturally replenished). In 2008,
about 19% of global final energy consumption came from renewables, with 13%
coming from traditional
biomass, which is mainly used for
heating, and 3.2% from
hydroelectricity. New renewables (small hydro, modern
biomass, wind, solar, geothermal, and biofuels) accounted for another 2.7% and
are growing very rapidly. The share of renewables in
electricity
generation is around
18%, with 15% of global electricity coming from hydroelectricity and 3% from
new renewables.
While
many renewable energy projects are large-scale, renewable technologies are also
suited to
rural and remote areas, where energy is
often crucial in
human
development.
Globally, an estimated 3 million households get power from small
solar PV systems.
Micro-hydro systems configured into village-scale
or county-scale mini-grids serve many areas.More than 30 million rural
households get lighting and cooking from
biogas made in household-scale digesters.
Biomass cookstoves are used by 160 million
households.
- Power generation.
- Renewable energy provides 18 percent of total electricity generation
worldwide. Renewable power generators are spread across many countries,
and wind power alone already provides a significant share of electricity
in some areas: for example, 14 percent in the U.S. state of Iowa, 40
percent in the northern German state of Schleswig-Holstein, and 20 percent
in Denmark. Some countries get most of their power from renewables,
including Iceland (100 percent), Brazil (85 percent), Austria (62
percent), New Zealand (65 percent), and Sweden (54 percent).
- Heating.
- Solar hot water makes an
important contribution in many countries, most notably in China, which now
has 70 percent of the global total (180 GWth). Most of these systems are
installed on multi-family apartment buildings and meet a portion of the
hot water needs of an estimated 50–60 million households in China.
Worldwide, total installed solar water heating systems meet a
portion of the water heating needs of over 70 million households. The use
of biomass for heating continues to grow as well. In Sweden, national use
of biomass energy has surpassed that of oil. Direct geothermal for heating
is also growing rapidly.
- Transport fuels.
- Renewable
biofuels
have contributed to a significant decline in oil consumption in the United
States since 2006. The 93 billion liters of biofuels produced worldwide in
2009 displaced the equivalent of an estimated 68 billion liters of
gasoline, equal to about 5 percent of world gasoline production.
Wind power:
Airflows
can be used to run
wind turbines. Modern wind turbines range from
around 600 kW to 5 MW of rated power, although turbines with rated output
of 1.5–3 MW have become the most common for commercial use; the power output of
a turbine is a function of the cube of the wind speed, so as wind speed
increases, power output increases dramatically.Areas where winds are stronger
and more constant, such as offshore and high altitude sites, are preferred
locations for wind farms. Typical
capacity factors are 20-40%, with values at the upper
end of the range in particularly favourable sites.
Globally,
the long-term technical potential of wind energy is believed to be five times
total current global energy production, or 40 times current electricity demand.
This could require wind turbines to be installed over large areas, particularly
in areas of higher wind resources. Offshore resources experience mean wind
speeds of ~90% greater than that of land, so offshore resources could
contribute substantially more energy.
Hydropower:
Solar energy:
Solar
technologies are broadly characterized as either
passive solar or
active solar depending on the way they capture,
convert and distribute solar energy. Active solar techniques include the use of
photovoltaic panels and
solar
thermal collectors to
harness the energy. Passive solar techniques include orienting a building to
the Sun, selecting materials with favorable
thermal mass or light dispersing properties, and
designing spaces that
naturally circulate air.
Biomass:
Biomass (plant material) is a renewable
energy source because the energy it contains comes from the sun. Through the
process of
photosynthesis, plants capture the sun's energy.
When the plants are burned, they release the sun's energy they contain. In this
way, biomass functions as a sort of natural battery for storing solar energy.
As long as biomass is produced sustainably, with only as much used as is grown,
the battery will last indefinitely.
In
general there are two main approaches to using plants for energy production:
growing plants specifically for energy use, and using the residues from plants
that are used for other things. The best approaches vary from region to region
according to climate, soils and geography.
Biofuel:
Liquid
biofuel is usually either bioalcohol such as
bioethanol or an oil such as biodiesel.
Bioethanol is an
alcohol made by
fermenting the sugar components of plant
materials and it is made mostly from sugar and starch crops. With advanced
technology being developed, cellulosic biomass, such as trees and grasses, are
also used as feedstocks for ethanol production. Ethanol can be used as a fuel for
vehicles in its pure form, but it is usually used as a
gasoline additive to increase octane and
improve vehicle emissions. Bioethanol is widely used in the USA and in
Brazil.
Biodiesel is made from
vegetable oils,
animal fats or recycled greases. Biodiesel can be
used as a fuel for vehicles in its pure form, but it is usually used as a
diesel additive to reduce levels of particulates, carbon monoxide, and
hydrocarbons from diesel-powered vehicles. Biodiesel is produced from
oils or fats using
transesterification and is the most common biofuel in
Europe.
Biofuels
provided 1.8% of the world's transport fuel in 2008.
The
major advantage of biofuels emerges from their minor impact on the carbon cycle
in nature. While
fossil
fuels add carbon to
the carbon cycle, biofuels recycle the carbon via the path of plants - biofuel
- atmospheric carbon dioxide - plants.
Geothermal energy:
Geothermal
energy is energy obtained by tapping the heat of the earth itself, both from
kilometers deep into the Earth's
crust in volcanically active locations of
the globe or from shallow depths, as in
geothermal
heat pumps in most
locations of the planet. It is expensive to build a power station but operating
costs are low resulting in low energy costs for suitable sites. Ultimately,
this energy derives from heat in the
Earth's core.
Three
types of power plants are used to generate power from geothermal energy: dry
steam, flash, and binary. Dry steam plants take steam out of fractures in the
ground and use it to directly drive a turbine that spins a generator. Flash
plants take hot water, usually at temperatures over 200 °C, out of the
ground, and allows it to boil as it rises to the surface then separates the
steam phase in steam/water separators and then runs the steam through a
turbine. In binary plants, the hot water flows through heat exchangers, boiling
an organic fluid that spins the turbine. The condensed steam and remaining
geothermal fluid from all three types of plants are injected back into the hot
rock to pick up more heat.
The
geothermal energy from the core of the Earth is closer to the surface in some
areas than in others. Where hot underground steam or water can be tapped and
brought to the surface it may be used to generate electricity. Such
geothermal power sources exist in certain geologically
unstable parts of the world such as
Chile,
Iceland, New Zealand, United States,
the Philippines and Italy. The two most prominent
areas for this in the United States are in the
Yellowstone basin and in northern
California.
Iceland produced 170 MW geothermal power and
heated 86% of all houses in the year 2000 through geothermal energy. Some 8000
MW of capacity is operational in total.
There
is also the potential to generate geothermal energy from
hot dry rocks.
Holes at least 3 km deep are drilled into the earth. Some of these holes
pump water into the earth, while other holes pump hot water out. The heat
resource consists of hot underground radiogenic granite rocks, which heat up
when there is enough sediment between the rock and the earths surface. Several
companies in Australia are exploring this technology.
At
the end of 2009, worldwide
wind farm capacity was 159,213 MW,
[36] representing an increase of 31
percent during the year,
[3] and wind power supplied some 1.3% of
global electricity consumption.
[37] Wind power accounts for approximately
19% of electricity use in
Denmark, 9% in
Spain and
Portugal, and
6% in
Germany and
the Republic of Ireland.
[38]
Top 10 wind power countries
|
Country
|
Total capacity
end 2009 (MW)
|
Total capacity
June 2010 (MW)
|
United States
|
35,159
|
36,300
|
China
|
26,010
|
33,800
|
Germany
|
25,777
|
26,400
|
Spain
|
19,149
|
19,500
|
India
|
10, 925
|
12,100
|
Italy
|
4,850
|
5,300
|
France
|
4,521
|
5,000
|
United Kingdom
|
4,092
|
4,600
|
Portugal
|
3,535
|
3,800
|
Denmark
|
3,497
|
3,700
|
Rest of world
|
21,698
|
24,500
|
Total
|
159,213
|
175,000
|
New generation of solar thermal plants:
Large
solar
thermal power
stations include the 354
megawatt (MW)
Solar Energy Generating Systems power plant in the USA,
Solnova Solar Power Station (Spain, 150 MW),
Andasol solar power station (Spain, 100 MW),
Nevada Solar One (USA, 64 MW),
PS20 solar power tower (Spain, 20 MW), and the
PS10 solar power tower (Spain, 11 MW).
The
solar thermal power industry is growing rapidly with 1.2 GW under construction
as of April 2009 and another 13.9 GW announced globally through 2014. Spain is
the epicenter of solar thermal power development with 22 projects for 1,037 MW
under construction, all of which are projected to come online by the end of
2010.In the United States, 5,600 MW of solar thermal power projects have been
announced.In developing countries, three
World Bank projects for integrated solar
thermal/combined-cycle gas-turbine power plants in
Egypt,
Mexico, and
Morocco have been approved.
