generated from natural resources
such as sunlight
, which are
replenished). In 2006, about 18% of global final energy consumption
came from renewables, with 13% coming from traditional biomass
, such as wood-burning
and 3% from hydroelectricity
. New renewables
(small hydro, modern
biomass, wind, solar, geothermal, and biofuels) accounted for 2.4%
and are growing very rapidly. The share of renewables in electricity generation
is around 18%,
with 15% of global electricity coming from hydroelectricity and
3.4% from new renewables.
is growing at the rate of 30%
annually, with a worldwide installed capacity
(MW) in 2008, and is widely used
and the United States
. The annual
manufacturing output of the photovoltaics
industry reached 6,900 MW in
2008, and photovoltaic power
are popular in Germany
. Solar thermal power
stations operate in
the USA and Spain, and the largest of these is the 354 MW SEGS
power plant in the Mojave Desert
world's largest geothermal power
installation is The
Geysers in California, with a rated capacity of 750
Brazil has one of the largest renewable energy programs
in the world, involving production of ethanol fuel
from sugar cane, and ethanol now
provides 18% of the country's automotive fuel. Ethanol fuel is also
widely available in the USA.
While most renewable energy projects and production is large-scale,
renewable technologies are also suited to small off-grid applications
sometimes in rural
and remote areas, where
energy is often crucial in human development. Kenya has the world's
highest household solar ownership rate with roughly 30,000 small
(20–100 watt) solar power systems sold per year.
Some renewable energy technologies are criticized for being
yet the renewable energy market continues to grow. Climate change
concerns, coupled with
high oil prices
, and increasing government
support, are driving increasing renewable energy legislation,
incentives and commercialization
government spending, regulation and policies should help the
industry weather the 2009 economic crisis better than many other
Main forms/sources of renewable energy
Three energy sources
2008 worldwide renewable-energy
The majority of renewable energy technologies are powered by the
sun. The Earth-Atmosphere system is in equilibrium such that heat
radiation into space is equal to incoming solar radiation
, the resulting level of
energy within the Earth-Atmosphere system can roughly be described
as the Earth's "climate." The hydrosphere (water) absorbs a major
fraction of the incoming radiation. Most radiation is absorbed at
low latitudes around the equator, but this energy is dissipated
around the globe in the form of winds and ocean currents. Wave
motion may play a role in the process of transferring mechanical
energy between the atmosphere and the ocean through wind stress.
Solar energy is also responsible for the distribution of
precipitation which is tapped by hydroelectric projects, and for
the growth of plants used to create biofuels.
Renewable energy flows involve natural phenomena such as sunlight
, as the International Energy Agency
Each of these sources has unique characteristics which influence
how and where they are used.
Vestas V80 wind turbines
Airflows can be used to run wind
. 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
are 20-40%, with
values at the upper end of the range in particularly favourable
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 large
amounts of land to be used for wind turbines, 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."Offshore stations
experience mean wind speeds at 80 m that are 90% greater than over
land on average. Evaluation of global wind power
"Overall, the researchers calculated winds at 80 meters [300
feet] traveled over the ocean at approximately 8.6 meters per
second and at nearly 4.5 meters per second over land [20 and 10
miles per hour, respectively].
" Global Wind Map Shows Best Wind Farm Locations
(URL accessed January 30, 2006). This number could also increase
with higher altitude ground-based or airborne wind
."High-altitude winds could provide a potentially
enormous renewable energy source, and scientists like Roberts
believe flying windmills could
put an end to dependence on fossil fuels. At , winds are strong and
constant. On the ground, wind is often unreliable — the biggest
problem for ground-based wind turbines.
" Windmills in the Sky
(URL accessed January 30,
is renewable and produces no
such as carbon dioxide
Energy in water (in the form of kinetic energy, temperature
differences or salinity gradients
can be harnessed and used. Since water is about 800 times denser than air
,even a slow flowing stream of
water, or moderate sea swell
yield considerable amounts of energy.
There are many forms of water energy:
Monocrystalline solar cell
In this context, "solar energy" refers to energy that is collected
from sunlight. Solar energy can be applied in many ways, including
Plants use photosynthesis
to grow and
. Also known as biomatter,
biomass can be used directly as fuel or to produce biofuels
. Agriculturally produced biomass fuels,
such as biodiesel
by-product of sugar cane
be burned in internal
biofuel is burned to release its stored chemical energy. Research
into more efficient methods of converting biofuels and other fuels
into electricity utilizing fuel cells is an area of very active
Information on pump, California.
Liquid biofuel is usually either a bioalcohol such as ethanol fuel
or an oil such as biodiesel
or straight vegetable oil
. Biodiesel can
be used in modern diesel vehicles with little or no modification to
the engine. It can be made from waste and virgin vegetable and
animal oils and fats (lipids
vegetable oils can be used in modified diesel engines. In fact the
was originally designed
to run on vegetable oil rather than fossil fuel. A major benefit of
biodiesel use is the reduction in net CO2
since all the carbon emitted was recently captured during the
growing phase of the biomass. The use of biodiesel also reduces
emission of carbon monoxide and other pollutants by 20 to
In some areas corn
, and switchgrasses
are grown specifically to produce
(also known as grain alcohol) a
liquid which can be used in internal combustion engines
is being phased into the current energy
infrastructure. E85 is a fuel composed of 85% ethanol and 15%
gasoline that is sold to consumers. Biobutanol
is being developed as an alternative
Another source of biofuel is sweet
. It produces both food and fuel from the same crop.
Some studies have shown that the crop is net energy positive ie. it
produces more energy than is consumed in its production and
Solid biomass is most commonly used directly as a combustible fuel,
in Biomass Fuelled Power
producing 10-20 MJ/kg of heat. Its forms and sources
include wood fuel
, the biogenic portion of
municipal solid waste, or the unused portion of field crops. Field
crops may or may not be grown intentionally as an energy crop
, and the remaining plant byproduct
used as a fuel. Most types of biomass contain energy. Even cow manure
two-thirds of the original energy consumed by the cow. Energy
harvesting via a bioreactor
cost-effective solution to the waste
issues faced by the dairy
, and can produce enough biogas
run a farm.
With current technology, it is not ideally suited for use as a
transportation vehicles require power sources with high power
density, such as that provided by internal combustion engines.
These engines generally require clean burning fuels, which are
generally in liquid form, and to a lesser extent, compressed
more portable because they can have a high energy density, and they
can be pumped, which makes handling easier.
Non-transportation applications can usually tolerate the low
power-density of external combustion engines, that can run directly
on less-expensive solid biomass fuel, for combined heat and power.
One type of biomass is wood, which has been used for millennia. Two
billion people currently cook every day, and heat their homes in
the winter by burning biomass, which is a major contributor to
man-made climate change global warming. The black soot that is
being carried from Asia to polar ice caps is causing them to melt
faster in the summer. In the 19th century, wood-fired steam engines
were common, contributing significantly to industrial revolution
unhealthy air pollution. Coal is a form of biomass that has been
compressed over millennia to produce a non-renewable
, highly-polluting fossil
Wood and its byproducts can now be converted through processes such
into biofuels such as
methanol or ethanol fuel; although further development may be
required to make these methods affordable and practical. Sugar cane residue
, corn cobs
and other plant
can be, and are, burned quite successfully. The net
carbon dioxide emissions that are added to the atmosphere by this
process are only from the fossil fuel that was consumed to plant,
fertilize, harvest and transport the biomass.
Processes to harvest biomass from short-rotation trees like
and perennial grasses such as switchgrass
, require less frequent
cultivation and less nitrogen than do typical annual crops.
miscanthus and burning it to
generate electricity is being studied and may be economically
Biogas can easily be produced from current waste streams, such as
paper production, sugar production, sewage, animal waste and so
forth. These various waste streams have to be slurried together and
allowed to naturally ferment, producing methane gas. This can be
done by converting current sewage plants into biogas plants. When a
biogas plant has extracted all the methane it can, the remains are
sometimes more suitable as fertilizer than the original
Alternatively biogas can be produced via advanced waste processing
systems such as mechanical biological
. These systems recover the recyclable elements of
household waste and process the biodegradable fraction in anaerobic digesters
Renewable natural gas
biogas which has been upgraded to a quality similar to natural gas
. By upgrading the quality to that of
natural gas, it becomes possible to distribute the gas to the mass
market via the existing gas grid.
Geothermal energy is energy obtained by tapping the heat of the
earth itself, both from kilometers deep into the Earth's crust
in some places of the globe or from some meters
in geothermal heat pump
the places 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
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
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
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.
Renewable energy commercialization
Percentage of renewables in primary
energy consumption of EU-member states in 2005.
Source: Primärenergieverbrauch und erneuerbare Energien in
der EU, Fig 55
See Also Relative
cost of electricity generated by different sources
comparing renewable energy sources with each other and with
conventional power sources, three main factors must be
- capital costs (including, for nuclear
energy, waste-disposal and decommissioning costs);
- operating and maintenance costs;
- fuel costs (for fossil-fuel and
biomass sources—for wastes, these costs may
actually be negative).
These costs are all brought together, using discounted cash flow
, here. Inherently,
renewables are on a decreasing cost curve, while non-renewables are
on an increasing cost curve. In 2009, costs are comparable among
wind, nuclear, coal, and natural gas, but for CSP—concentrating solar power
) they are somewhat
There are additional costs for renewables in terms of increased
grid interconnection to allow for variability of weather
and load, but these have been shown in the
pan-European case to be quite low—overall, wind energy
costs about the same as present-day
Growth of renewables
From the end of 2004 to the end of 2008, solar photovoltaic (PV)
capacity increased sixfold to more than 16 gigawatts (GW), wind
power capacity increased 250 percent to 121 GW, and total power
capacity from new renewables increased 75 percent to 280 GW. During
the same period, solar heating capacity doubled to 145
gigawatts-thermal (GWth), while biodiesel production increased
sixfold to 12 billion liters per year and ethanol production
doubled to 67 billion liters per year.
Selected renewable energy indicators
|Selected global indicators
|Investment in new renewable capacity (annual)
||120 billion USD
|Existing renewables power capacity,
including large-scale hydro
|Existing renewables power capacity,
excluding large hydro
|Wind power capacity (existing)
|Solar hot water/ Space heating
|Ethanol production (annual)
||67 billion liters
|Countries with policy targets
for renewable energy use
Wind power market
Wind power: worldwide installed
At the end of 2008, worldwide wind farm
capacity was 120,791 megawatts
representing an increase of 28.8 percent during the year, and
produced some 1.3% of global
electricity consumption. Wind power accounts for approximately 19%
of electricity use in Denmark
9% in Spain
, and 6% in Germany
and the Republic of Ireland.
The United States
an important growth area and installed U.S. wind power capacity
reached 25,170 MW at the end of 2008. As of September 2009, the
Roscoe Wind Farm
(781 MW) is the
world's largest wind farm.
As of 2009, the 209 megawatt
(MW) Horns Rev 2 wind farm
is the world's largest
offshore wind farm. The United Kingdom
world's leading generator of offshore wind power, followed by
New generation of solar thermal plants
solar thermal power
stations include the 354 MW Solar Energy Generating
Systems power plant in the USA, Nevada Solar One (USA, 64 MW), Andasol 1 (Spain, 50 MW), Andasol 2 (Spain, 50 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
World's largest photovoltaic power plants
October 2009, the largest photovoltaic (PV) power plants in the
world are the Olmedilla
Photovoltaic Park (Spain, 60 MW), the Strasskirchen Solar Park (Germany,
54 MW), the Lieberose
Photovoltaic Park (Germany, 53 MW), the Puertollano Photovoltaic Park
(Spain, 50 MW), the Moura photovoltaic power
station (Portugal, 46 MW), and the Waldpolenz
Solar Park (Germany, 40 MW).
First Solar 40 MW PV Array installed
by JUWI Group in Waldpolenz, Germany
Many of these plants are integrated with agriculture and some use
innovative tracking systems that follow the sun's daily path across
the sky to generate more electricity than conventional
fixed-mounted systems. There are no fuel costs or emissions during
operation of the power stations.
Farm is a proposed 550 MW solar photovoltaic power plant which is to be built northwest of
Valley in the USA at a cost of over $1
billion.Built on of ranchland, the project would
utilize thin-film PV panels designed and manufactured by OptiSolar
in Hayward and Sacramento.
The project would deliver approximately
1,100 gigawatt-hours (GW·h) annually of renewable energy. The
project is expected to begin construction in 2010, begin power
delivery in 2011, and be fully operational by 2013.
Ranch is a proposed 250 MW solar photovoltaic power plant
which is to be built by SunPower in the
Plain, northwest of California
However, when it comes to renewable energy systems and PV, it is
not just large systems that matter. Building-integrated
or "onsite" PV systems have the advantage of
being matched to end use energy needs in terms of scale. So the
energy is supplied close to where it is needed.
Use of ethanol for transportation
Since the 1970s, Brazil has had
an ethanol fuel program
which has allowed the country to become
the world's second largest producer of ethanol
(after the United States) and the world's
largest exporter. Brazil’s ethanol fuel program uses modern
equipment and cheap sugar cane
feedstock, and the residual cane-waste (bagasse
) is used to process heat and power. There
are no longer light vehicles in Brazil running on pure gasoline. By
the end of 2008 there were 35,000 filling stations throughout
Brazil with at least one ethanol pump.
Most cars on the road today in the U.S. can run on blends of up to
10% ethanol, and motor vehicle manufacturers already produce
vehicles designed to run on much higher ethanol blends. Ford
, and GM
are among the automobile
companies that sell “flexible-fuel” cars, trucks, and minivans that
can use gasoline and ethanol blends ranging from pure gasoline up
to 85% ethanol (E85). By mid-2006, there were approximately six
million E85-compatible vehicles on U.S. roads. The challenge is to
expand the market for biofuels beyond the farm states where they
have been most popular to date. Flex-fuel vehicles are assisting in
this transition because they allow drivers to choose different
fuels based on price and availability. The Energy Policy Act of 2005
which calls for 7.5 billion gallons of biofuels to be used annually
by 2012, will also help to expand the market.
Geothermal energy prospects
The Geysers, is a geothermal
power field located 72 miles (116 km) north of San Francisco, California.
The West Ford Flat power plant is one of 21 power plants at The
It is the largest geothermal development in
the world outputting over 750 MW.
Geothermal power capacity surpassed 10 GW in 2008. The United
States is the world leader, with some 120 projects under
development in early 2009, representing at least 5 GW. Other
countries with significant recent growth in geothermal include
Australia, El Salvador, Guatemala, Iceland, Indonesia, Kenya,
Mexico, Nicaragua, Papua New Guinea, and Turkey. As of 2008,
geothermal power development was under way in more than 40
countries. Geothermal power accounted for 17 percent of the
Philippines total power mix at the end of 2008, with installed
capacity close to 2,000 megawatts.
Geothermal (ground source) heat pumps represented an estimated 30
GWth of installed capacity at the end of 2008, with other direct
uses of geothermal heat (i.e., for space heating, agricultural
drying and other uses) reaching an estimated 15 GWth. As of 2008,
at least 76 countries use direct geothermal energy in some
Wave farms expansion
Portugal now has the world's first commercial wave farm
, the Agucadoura Wave Park
officially opened in September 2008. The farm uses three Pelamis P-750
generating 2.25 MW. Initial costs are put at €
8.5 million. A second phase of the project is now
planned to increase the installed capacity to 21MW using a further
25 Pelamis machines.
Funding for a wave farm in Scotland was announced in February, 2007
by the Scottish Government
, at a
cost of over 4 million pounds
part of a £13 million funding packages for ocean power in
. The farm will be the world's largest with a capacity
of 3MW generated by four Pelamis machines.
Developing country markets
Renewable energy can be particularly suitable for developing
countries. In rural and remote areas, transmission and distribution
of energy generated from fossil fuels
can be difficult and expensive. Producing renewable energy locally
can offer a viable alternative.
Renewable energy projects in many developing countries have
demonstrated that renewable energy can directly contribute to
the energy needed for creating businesses and employment. Renewable
energy technologies can also make indirect contributions to
alleviating poverty by providing energy for cooking, space heating,
and lighting. Renewable energy can also contribute to education, by
providing electricity to schools.
Kenya is the world leader in the number of solar power systems
installed per capita (but not the number of watts added). More than
30,000 very small solar panels, each producing 12 to 30 watts, are
sold in Kenyaannually. For an investment of as little as $100 for
the panel and wiring, the PV system can be used to charge a car
battery, which can then provide power to run a fluorescent lamp or
a small television for a few hours a day. More Kenyans adopt solar
power every year than make connections to the country’s electric
In India, a solar loan
sponsored by UNEP has helped 100,000 people finance
solar power systems in India. Success in India's solar program has led to
similar projects in other parts of developing world like Tunisia, Morocco, Indonesia and Mexico.
Industry and policy trends
Global revenues for solar photovoltaics, wind power, and biofuels
expanded from $76 billion in 2007 to $115 billion in 2008. New
global investments in clean energy
technologies expanded by 4.7 percent from $148 billion in 2007 to
$155 billion in 2008. U.S. President Barack
's American Recovery
and Reinvestment Act of 2009
includes more than $70 billion in
direct spending and tax credits for clean energy and associated
transportation programs. Clean Edge
suggests that the commercialization of clean energy will help
countries around the world pull out of the current economic
Constraints and opportunities
Critics suggest that some renewable energy applications may create
pollution, be dangerous, take up large amounts of land, or be
incapable of generating a large net amount of energy. Proponents
advocate the use of "appropriate renewables", also known as
soft energy technologies
as these have many advantages.
Availability and reliability
There is no shortage of solar-derived energy on Earth. Indeed the
storages and flows of energy on the planet are very large relative
to human needs.
- Annual photosynthesis by the
vegetation in the United States is 50 billion GJ, equivalent to
nearly 60% of the nation’s annual fossil fuel use.
- The amount of solar energy intercepted by the Earth every
minute is greater than the amount of energy the world uses in
fossil fuels each year.
- The energy in the winds that blow across
the United States each year could produce more than 16 billion GJ
of electricity—more than one and
one-half times the electricity consumed in the United States in
- Tropical oceans absorb 560 trillion
gigajoules (GJ) of solar energy each year,
equivalent to 1,600 times the world’s annual energy use.
A criticism of some renewable sources is their variable nature. But
renewable power sources can actually be integrated into the grid
system quite well, as Amory Lovins
Variable but forecastable renewables (wind and solar
cells) are very reliable when integrated with each other, existing
supplies and demand. For example, three German states were more
than 30 percent wind-powered in 2007—and more than 100 percent in
some months. Mostly renewable power generally needs less backup
than utilities already bought to combat big coal and nuclear
Mark Z. Jacobson
has studied how wind, water and
solar technologies can provide 100 per cent of the world's energy,
eliminating all fossil fuels
advocates a "smart mix" of renewable energy sources to reliably
meet electricity demand:
Because the wind blows during stormy conditions when
the sun does not shine and the sun often shines on calm days with
little wind, combining wind and solar can go a long way toward
meeting demand, especially when geothermal provides a steady base
and hydroelectric can be called on to fill in the
The challenge of variable power supply BE be readily alleviated by
certain forms of grid energy
such as pumped-storage
, hydrogen fuel cells
thermal mass and compressed air. Batteries are still far too
expensive to have any impact.
From detailed studies in Europe, Dr Gregor Czisch has shown that
the variable power issue can be solved by interconnecting renewable
across Europe the European super
and using only existing storage hydro. The costs of power
over the lifetime of the scheme are the same as today's
conventional power supplies, indicating that the capital investment
is roughly the same as the cost of fuel avoided over the projects
25 year lifetime and
Lovins goes on to say that the unreliability of renewable energy is
a myth, while the unreliability of nuclear energy
is real. Of all U.S. nuclear
plants built, 21 percent were abandoned and 27 percent have failed
at least once. Successful reactors must close for refueling every
17 months for 39 days. And when shut in response to grid failure,
they can't quickly restart. This is simply not the case for wind
farms, for example.
Wave energy and some other renewables are continuously available. A
wave energy scheme installed in Australia generates electricity
with an 80% availability factor.
groups propose a 100%
Renewable Energy Source Supply, without fossil fuels
and nuclear power
.Scientists from the University
of Kassel have suggested that Germany can power itself
entirely by renewable energy.
Both solar and wind generating stations have been criticized from
an aesthetic point of view. However, methods and opportunities
exist to deploy these renewable technologies efficiently and
unobtrusively: fixed solar collectors can double as noise barriers
along highways, and extensive
roadway, parking lot, and roof-top area is currently available;
amorphous photovoltaic cells
also be used to tint windows and produce energy. Advocates of
renewable energy also argue that current infrastructure is less
aesthetically pleasing than alternatives, but sited further from
the view of most critics.
Environmental, social and legal considerations
While most renewable energy sources do not produce pollution
directly, the materials, industrial processes, and construction
equipment used to create them may generate waste and pollution.
Some renewable energy systems actually create environmental
Land area required
Another environmental issue
particularly with biomass and biofuels, is the large amount of land
required to harvest energy, which otherwise could be used for other
purposes or left as undeveloped land. However, it should be pointed
out that these fuels may reduce the need for harvesting
non-renewable energy sources, such as vast strip-mined areas and
slag mountains for coal, safety zones around nuclear plants, and
hundreds of square miles being strip-mined for oil sands. These
responses, however, do not account for the extremely high biodiversity
of land used for ethanol crops,
particularly sugar cane.
In the U.S., crops grown for biofuels are the most land- and
water-intensive of the renewable energy sources. In 2005, about 12%
of the nation’s corn crop (covering 11 million acres
(45,000 km²) of farmland) was used to produce four billion
gallons of ethanol—which equates to about 2% of annual U.S.
gasoline consumption. For biofuels to make a much larger
contribution to the energy economy, the industry will have to
accelerate the development of new feedstocks, agricultural
practices,and technologies that are more land and water
The efficiency of biofuels production has increased
significantlyand there are new methods to boost biofuel production,
although using bioelectricity, by burning the biomass to produce
electricity for an electric car, increases the distance that a car
can go from a hectare (about 2.5 acres) of crops by 81%, from
30,000 km to 54,000 km per year. However, covering that
same hectare with photovoltaics (in relatively sunless Germany or
England) allows the electric car to go 3,250,000 km/year, over
100 times as far as from biofuel.
The major advantage of hydroelectric systems is the elimination of
the cost of fuel. Other advantages include longer life than
fuel-fired generation, low operating costs, and the provision of
facilities for water sports. Operation of pumped-storage plants
improves the daily load factor of the generation system. Overall,
hydroelectric power can be far less expensive than electricity
generated from fossil fuels or nuclear energy, and areas with
abundant hydroelectric power attract industry.
However, there are several major disadvantages of hydroelectric
systems. These include: dislocation of people living where the
reservoirs are planned, release of significant amounts of carbon
dioxide at construction and flooding of the reservoir, disruption
of aquatic ecosystems and birdlife, adverse impacts on the river
environment, potential risks of sabotage and terrorism, and in rare
cases catastrophic failure of the dam wall. (See Hydroelectricity
Large hydroelectric power is considered to be a renewable energy by
a large number of sources, however, many groups have lobbied for it
to be excluded from renewable electricity standards
initiative to promote the use of renewable energies, and sometimes
the definition of renewable itself. Some organizations, including
US federal agencies, will specifically refer to "non-hydro
renewable energy".Environmental Protection Agency. Electricity from Non-Hydroelectric Renewable Energy
Energy Information Association. Policies to Promote Non-hydro Renewable Energy in
the United States and Selected Countries
. February 2005. Many
laws exist that specifically label "small
" as renewable or sustainable and large hydro as not.
Furthermore, the line between what is small or large also differs
by governing body.
Hydroelectric power is now more difficult to site in developed
nations because most major sites within these nations are either
already being exploited or may be unavailable for other reasons
such as environmental considerations.
A wind farm
, when installed on
agricultural land, has one of the lowest environmental impacts of
all energy sources: To generate the total electricity used in the
UK annually, 6% of the land area would be utilised, an area of
about 70 miles by 70 miles, and this would not preclude that land
from being used for other purposes.
- Wind power occupies less land area per kilowatt-hour (kWh) of
electricity generated than any other energy conversion system,
apart from rooftop solar energy, and is compatible with grazing and
- It generates the energy used in its construction in just 3
months of operation, yet its operational lifetime is 20–25
- Greenhouse gas emissions and air pollution produced by its
construction are low and declining. There are no emissions or
pollution produced by its operation.
- In substituting for base-load coal power, wind power produces a
net decrease in greenhouse gas emissions and air pollution, and a
net increase in biodiversity.
- Modern wind turbines are almost silent and rotate so slowly (in
terms of revolutions per minute) that they are rarely a hazard to
Studies of birds and offshore wind farms in Europe have found that
there are very few bird collisions. Several offshore wind sites in
Europe have been in areas heavily used by seabirds. Improvements in
wind turbine design, including a much slower rate of rotation of
the blades and a smooth tower base instead of perchable lattice
towers, have helped reduce bird mortality at wind farms around the
world. However older smaller wind turbines may be hazardous to
flying birds. Birds are severely impacted by fossil fuel energy;
examples include birds dying from exposure to oil spills, habitat
loss from acid rain and mountaintop removal coal mining
and mercury poisoning.
Though a source of renewable energy may last for billions of years,
renewable energy infrastructure, like hydroelectric dams, will not
last forever, and must be removed and replaced at some point.
Events like the shifting of riverbeds, or changing weather patterns
could potentially alter or even halt the function of hydroelectric
dams, lowering the amount of time they are available to generate
Some have claimed that geothermal being a renewable energy source
depends on the rate of extraction being slow enough such that
depletion does not occur. If depletion does occur, the temperature
can regenerate if given a long period of non-use.
government of Iceland states: "It
should be stressed that the geothermal resource is not strictly
renewable in the same sense as the hydro resource."
estimates that Iceland's geothermal energy could provide 1700 MW
for over 100 years, compared to the current production of 140 MW.
Radioactive elements in the Earth's crust continuously decay,
replenishing the heat. The International Energy Agency
classifies geothermal power as renewable.
All biomass needs to go through some of these steps: it needs to be
grown, collected, dried, fermented and burned. All of these steps
require resources and an infrastructure.
Some studies contend that ethanol is "energy negative", meaning
that it takes more energy to produce than is contained in the final
product. However, a large number of recent studies, including a
2006 article in the journal Science
offer the opinion that
fuels like ethanol are energy positive. Furthermore, fossil fuels
also require significant energy inputs which have seldom been
accounted for in the past.
Additionally, ethanol is not the only product created during
production, and the energy content of the by-products must also be
considered. Corn is typically 66% starch and the remaining 33% is
not fermented. This unfermented component is called distillers
grain, which is high in fats and proteins, and makes good animal
feed. In Brazil, where sugar cane is used, the yield is higher, and
conversion to ethanol is somewhat more energy efficient than corn.
Recent developments with cellulosic
production may improve yields even further.
According to the International Energy Agency
biofuels technologies being developed today, notably cellulosic
ethanol, could allow biofuels to play a much bigger role in the
future than previously thought. Cellulosic ethanol can be made from
plant matter composed primarily of inedible cellulose fibers that
form the stems and branches of most plants. Crop residues (such as
corn stalks, wheat straw and rice straw),wood waste, and municipal
solid waste are potential sources of cellulosic biomass. Dedicated
energy crops, such as switchgrass, are also promising cellulose
sources that can be sustainably
in manyregions of the United States.
The ethanol and biodiesel production industries also create jobs in
plant construction, operations, and maintenance, mostly in rural
communities. According to the Renewable Fuels Association, the
ethanol industry created almost 154,000 U.S. jobs in2005 alone,
boosting household income by $5.7 billion. It also contributed
about $3.5 billion in tax revenues at the local, state, and federal
The U.S. electric power industry now relies on large, central power
stations, including coal, natural gas, nuclear, and hydropower
plants that together generate more than 95% of the nation’s
electricity. Over the next few decades uses of renewable energy
could help to diversify the nation’s bulk power supply. Already,
appropriate renewable resources (which excludes large hydropower)
produce 12% of northern California’s electricity.
Although most of today’s electricity comes from large,
central-station power plants, new technologies offer a range of
options for generating electricity nearer to where it is needed,
saving on the cost of transmitting and distributing power and
improving the overall efficiency and reliability of the
Improving energy efficiency
represents the most immediate and often the most cost-effective way
to reduce oil dependence, improve energy security, and reduce the
health and environmental impact of the energy system. By reducing
the total energy requirements of the economy, improved energy
efficiency could make increased reliance on renewable energy
sources more practical and affordable.
Competition with nuclear power
continues to be
considered as an alternative to fossil-fuel power sources (see
Low carbon power
), and in 1956, when the first peak oil
paper was presented, nuclear energy was
presented as the replacement for fossil fuels. However, the prospect
of increased nuclear power deployment was seriously undermined in
the United States as a result of the Three Mile
Island, and in the rest of the world after the Chernobyl
This trend is slowly reversing, and several
new nuclear reactors are scheduled for construction.
Physicist Bernard Cohen
proposed in 1983 that uranium dissolved in seawater is effectively
inexhaustible, and could therefore be considered a renewable source
of energy. However, this idea is not universally accepted, and
issues such as peak uranium
No legislative body has yet included nuclear energy under any legal
definition of "renewable energy sources" for provision of
development support, and statutory and scientific definitions of
renewable energies normally exclude nuclear energy.
- http://www.ren21.net/pdf/RE2007_Global_Status_Report.pdf Global
Status Report 2007
- REN21 (2009). Renewables Global Status Report: 2009 Update p.
- Global wind energy markets continue to boom – 2006
another record year (PDF).
- REN21 (2009). Renewables Global Status Report: 2009 Update p.
- World's largest photovoltaic power plants
- Solar Trough Power Plants (PDF).
- America and Brazil Intersect on Ethanol
- World Energy Assessment (2001). Renewable energy technologies, p. 221.
- What Solar Power Needs Now Renewable Energy
Access, 13 August 2007.
- United Nations Environment Programme Global Trends in Sustainable Energy Investment
2007: Analysis of Trends and Issues in the Financing of Renewable
Energy and Energy Efficiency in OECD and Developing
Countries (PDF), p. 3.
- Clean Edge
(2009). Clean Energy Trends 2009 pp. 1-4.
- Renewables Global Status Report 2009 Update
- Renewable Energy, Sorensen, Elsevier 2004
- Renewable energy... into the mainstream p.
- How Does A Wind Turbine's Energy Production Differ from
Its Power Production?
- Wind Power: Capacity Factor, Intermittency, and
what happens when the wind doesn’t blow? retrieved 24 January
- Biomass Crops as a Source of Renewable Energy: European
Experience with Miscanthus and Projections for Illinois
- Primärenergieverbrauch und erneuerbare Energien in
der EU (PDF).
- The Path to Grid Parity (Graphic)
Claveton energy group conference house of commons June 19th
- REN21 (2009). Renewables Global Status Report: 2009 Update p.
Martinot and Janet Sawin. Renewables Global Status Report 2009 Update,
Renewable Energy World, September 9, 2009.
- Wind energy gathers steam, US biggest market:
- World Wind Energy Association (2008). Wind turbines generate more than 1 % of the global
- New Report a Complete Analysis of the Global
Offshore Wind Energy Industry and its Major Players
- U.S., China Lead Global Wind Installation
- E.ON wraps up 457 MW wind farm, transfers
- Blown away
- Global Concentrated Solar Power Industry to Reach
25 GW by 2020
- Solar Thermal Projects Under Review or
- REN21 (2008). Renewables 2007 Global Status Report (PDF) p. 12.
- PV Resources.com (2009). World's
largest photovoltaic power plants
- Solar Integrated in New Jersey.
- REN21 (2009). Renewables Global Status Report: 2009 Update pp.
- Leonora Walet. Philippines targets $2.5 billion geothermal
development, Reuters, November 5, 2009.
- Sea machine makes waves in Europe
- Wave energy contract goes abroad
- Orkney to get 'biggest' wave farm.
- Power for the People p. 3.
- Energy for Development: The Potential Role of
Renewable Energy in Meeting the Millennium Development Goals
- The Rise of Renewable Energy
- Solar loan program in India.
Pernick and Clint Wilder (2009). Clean Energy Trends 2009, Clean Edge, pp. 1-4.
- Missing the Market Meltdown
- Mark Z. Jacobson and Mark A. Delucchi. A Path to Sustainable
Energy by 2030, Scientific American, November 2009, p.
Claverton Energy Group conference, House of Commmons
- Renewable Energy Sources
- The Sietch Blog » Germany Going 100% Renewable (Or
Yet Another Reason Why America Is Falling Behind)
- Hydrogen injection could boost biofuel
- Greater Transportation Energy and GHG Offsets from
Bioelectricity Than Ethanol
- Organized Wastefulness Photon International 2007-04
April, page 106
- Union of Concerned Scientists.
Renewable Electricity Standard FAQ.
- Renewable Energy Today. Groups Seek Exclusion of Large Hydro From
Renewables Initiative. June 3, 2004.
- Gary Frey, Deborah M. Linke. Hydropower as a renewable and sustainable energy
resource meeting global energy challenges in a reasonable way.
Energy Policy. June 9, 2002.
- Why Australia needs wind power
- newscientist.com June 2005 Wind turbines a breeze for migrating birds
- What about offshore wind farms and birds?
- Australian Broadcasting Company. Critics say geo-thermal power not renewable.
August 20, 2008.
- Response of Wairakei geothermal reservoir to 40
years of production, 2006 (pdf) Allan Clotworthy, Proceedings
World Geothermal Congress 2000. (accessed March 30).
- Geodynamics says it has the "hottest rocks on
- Ethanol Production Using Corn, Switchgrass, and
Wood; Biodiesel Production Using Soybean and Sunflower
- Ethanol Can Contribute to Energy and Environmental
- University of Minnesota
- Biofuels look to the next generation.
- International Energy Agency, World Energy Outlook
2006 (PDF), page 8.
- Industrial Biotechnology Is Revolutionizing the
Production of Ethanol Transportation Fuel (PDF), pages
- Nuclear Energy and the Fossil Fuels M. King
Hubbert 1956 retrieved 25 July 2009
- US Department of Energy - Nuclear Power Deployment