Renewable
energy is
energy
that comes from resources which are continually replenished such as
sunlight,
wind, rain,
tides,
waves and
geothermal heat. About 16% of global final energy consumption comes
from
renewable resources, with 10% of all energy from traditional
biomass,
mainly used for
heating, and 3.4% from
hydroelectricity. New renewables (small hydro, modern biomass, wind,
solar, geothermal, and biofuels) accounted for another 3% and are
growing very rapidly.[2]
The share of renewables in
electricity generation is around 19%, with 16% of electricity coming
from hydroelectricity and 3% from new renewables.[2]
Wind
power is growing at the rate of 30% annually, with a worldwide
installed capacity of 282,482
megawatts (MW) at the end of 2012, and is widely used in
Europe,
Asia, and the
United States. At the end of 2012 the
photovoltaic (PV) capacity worldwide was 100,000 MW, and PV power
stations are popular in
Germany and
Italy.
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. The world's largest
geothermal power installation is
The Geysers in California, with a rated capacity of 750 MW.
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 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.[3]
As of 2011, small solar PV systems provide electricity to a few million
households, and micro-hydro configured into mini-grids serves many more.
Over 44 million households use
biogas
made in household-scale digesters for
lighting and/or
cooking,
and more than 166 million households rely on a new generation of
more-efficient biomass cookstoves.[4]
United Nations' Secretary-General
Ban Ki-moon has said that renewable energy has the ability to lift
the poorest nations to new levels of prosperity.[5]
Climate change and
global warming concerns, coupled with
high oil prices,
peak
oil, and increasing government support, are driving increasing
renewable energy legislation, incentives and
commercialization.[6]
New government spending, regulation and policies helped the industry
weather the
global financial crisis better than many other sectors.[7]
According to a 2011 projection by the
International Energy Agency, solar power generators may produce most
of the world’s electricity within 50 years, dramatically reducing the
emissions of greenhouse gases that harm the environment.[8]
Overview
Global renewable power capacity excluding hydro
[9]
Renewable energy flows involve natural phenomena such as
sunlight,
wind, tides,
plant
growth, and
geothermal heat, as the
International Energy Agency explains:[10]
Renewable energy is derived from natural processes that are
replenished constantly. In its various forms, it derives
directly from the sun, or from heat generated deep within the
earth. Included in the definition is electricity and heat
generated from solar, wind, ocean, hydropower, biomass,
geothermal resources, and biofuels and hydrogen derived from
renewable resources.
Renewable energy resources and significant opportunities for
energy efficiency exist over wide geographical areas, in contrast to
other energy sources, which are concentrated in a limited number of
countries. Rapid deployment of renewable energy and energy efficiency,
and technological diversification of energy sources, would result in
significant
energy security and economic benefits.[11]
Renewable energy replaces conventional fuels in four distinct areas:
electricity generation,
hot water/space
heating,
motor fuels, and rural (off-grid) energy services:[12]
- Power generation. Renewable energy provides 19% of
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%
in the U.S. state of Iowa, 40% in the northern German state of
Schleswig-Holstein, and 49% in Denmark. Some countries get most of
their power from renewables, including Iceland (100%), Norway (98%),
Brazil (86%), Austria (62%), New Zealand (65%), and Sweden (54%).[13]
- Heating.
Solar hot water makes an important contribution to
renewable heat in many countries, most notably in China, which
now has 70% 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.[13]
- Transport fuels. Renewable
biofuels have contributed to a significant decline in oil
consumption in the United States since 2006.[13]
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% of world gasoline production.[13]
At the national level, at least 30 nations around the world already
have renewable energy contributing more than 20% of energy supply.
National renewable energy markets are projected to continue to grow
strongly in the coming decade and beyond, and some 120 countries have
various policy targets for longer-term shares of renewable energy,
including a binding 20% by 2020 target for the European Union. Some
countries have much higher long-term policy targets of up to 100%
renewables. Outside Europe, a diverse group of 20 or more other
countries target renewable energy shares in the 2020–2030 time frame
that range from 10% to 50%.[14]
In international public opinion surveys there is strong support for
promoting renewable sources such as solar power and wind power,
requiring utilities to use more renewable energy (even if this increases
the cost), and providing tax incentives to encourage the development and
use of such technologies. There is substantial optimism that renewable
energy investments will pay off economically in the long term.[15]
History
Prior to the development of coal in the mid 19th century, nearly all
energy used was renewable. Almost without a doubt the oldest known use
of renewable energy, in the form of traditional biomass to fuel fires,
dates from 790,000 years ago. Use of biomass for fire did not become
commonplace until many hundreds of thousands of years later, sometime
between 200,000 and 400,000 years ago.[16]
Probably the second oldest usage of renewable energy is harnessing
the wind in order to drive ships over water. This practice can be traced
back some 7000 years, to ships on the Nile.[17]
Moving into the time of recorded history, the primary sources of
traditional renewable energy were human labor, animal power, water
power, wind, and firewood(traditional biomass). A graph of energy use in
the United States up until 1900 shows oil and natural gas with about the
same importance in 1900 as wind and solar played in 2010.
By 1873, concerns of running out of coal prompted experiments with
using solar energy.[18]
Development of solar engines continued until the outbreak of World War
I. The eventual importance of solar energy, though, was recognized in a
1911 Scientific American article: "in the far distant future, natural
fuels having been exhausted [solar power] will remain as the only means
of existence of the human race".[19]
In the 1970s environmentalists promoted the development of renewable
energy both as a replacement for the eventual depletion of oil, as well
as for an escape from dependence on oil, and the first wind turbines
appeared. Solar had long been used for heating and cooling, but solar
panels were too costly to build solar farms until 1980.[20]
The theory of peak oil was published in 1956.[21]
By 2008 renewable energy had ceased being an alternative, and more
capacity of renewable energy was added than other sources in both the
United States and in Europe.[22]
Mainstream renewable technologies
Wind power
Airflows can be used to run
wind turbines. Modern utility-scale 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
available from the wind is a function of the cube of the wind speed, so
as wind speed increases, power output increases dramatically up to the
maximum output for the particular turbine.[23]
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.[24][25]
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 average wind speeds of ~90%
greater than that of land, so offshore resources could contribute
substantially more energy.[26]
Hydropower
Energy in water 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, can yield considerable amounts of energy. There are many
forms of water energy:
Solar energy
Solar energy applies energy from the
sun in the
form of
solar radiation for heat or to generate electricity.
Solar powered electricity generation uses either
photovoltaics or
heat engines (concentrated
solar power). A partial list of other solar applications includes
space heating and cooling through
solar architecture,
daylighting,
solar hot water,
solar cooking, and high temperature process heat for industrial
purposes.
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. Solar
energy capture is also being linked to research involving water
splitting and carbon dioxide reduction for the development of
artificial photosynthesis or solar fuels.[27]
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
burnt, 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.[28][unreliable
source?] In general there are two main approaches
to using plants for energy production: growing plants specifically for
energy use (known as first and third-generation biomass), and using the
residues (known as second-generation biomass) from plants that are used
for other things. See
biobased economy. The best approaches vary from region to region
according to climate, soils and geography.[28]
As of early 2012, 85 of 107 biomass plants operating in the U.S. had
been cited by federal or state regulators for violating clean air or
water laws over the past five years.[29]
The
Energy Information Administration projected that by 2017, biomass is
expected to be about twice as expensive as natural gas, slightly more
expensive than nuclear power, and much less expensive than solar panels.[30]
Biofuel
Biofuels include a wide range of fuels which are derived from
biomass.
The term covers
solid biomass,
liquid fuels and various
biogases.[31]
Liquid
biofuels include bioalcohols, such as bioethanol, and oils, such as
biodiesel. Gaseous biofuels include
biogas,
landfill gas and
synthetic gas.
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. However, according to the
European Environment Agency, biofuels do not address global warming
concerns.[32]
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 2.7% of the world's transport
fuel in
2010.[33]
Geothermal energy
Geothermal energy is from
thermal energy generated and stored in the Earth. Thermal energy is
the energy that determines the
temperature of matter. Earth's geothermal energy originates from the
original formation of the planet (20%) and from
radioactive decay of minerals (80%).[34]
The
geothermal gradient, which is the difference in temperature between
the core of the planet and its surface, drives a continuous conduction
of thermal energy in the form of
heat from
the core to the surface. The adjective geothermal originates from
the Greek roots geo, meaning earth, and thermos, meaning
heat.
The heat that is used for geothermal energy can be from deep within
the Earth, all the way down to Earth’s core – 4,000 miles (6,400 km)
down. At the core, temperatures may reach over 9,000 °F (5,000 °C). Heat
conducts from the core to surrounding rock. Extremely high temperature
and pressure cause some rock to melt, which is commonly known as magma.
Magma convects upward since it is lighter than the solid rock. This
magma then heats rock and water in the crust, sometimes up to
700 °F
(371 °C).[35]
From
hot springs, geothermal energy has been used for bathing since
Paleolithic times and for space heating since ancient Roman times,
but it is now better known for
electricity generation.
Oceanogenic Power
36 GW, 100% Plant factor, < 5 cents/kwh, Scalable to 16TW
The Earth is a giant
hydraulic pump without flow. Therefore, we can consider any of
these, as analysis model.
No matter their inefficiency, when there is no flow of water:
efficiency is zero, and all the energy in the shaft, is lost in heat or
internal energy, and self-recirculation.[36]
When the flow rate increases, so does the efficiency until it reaches
its maximum; being transferred more energy from the shaft, and lowering
the energy loss. That is, one flow is primed, which implies, a
percentage of the total shaft energy.
The rotational energy of our planet is 63
Yottawatt-hour, at 1% efficiency, we would have at our disposal 630
zetta watt-hour.
Also, there are estimates of the energy in the powerful, ocean
currents, that I think, the most powerful are four; already such
estimates of lost energy (370TW) is enough to justify our discovery. But
the interesting thing is that, until the more inefficient, centrifugal
pumps on our planet, if its impeller rotates, its efficiency is not less
than 1%. Why think that the earth not have this efficiency, in the worst
case? However, the discovery: Oceanogenic Power, and all its
extraordinary implications, it is justified, although the efficiency be
less than 0.000001%.
Enabling
technologies
Heat pumps and
Thermal energy storage are classes of technologies that can enable
the utilization of renewable energy sources that would otherwise be
inaccessible due to a temperature that is too low for utilization or a
time lag between when the energy is available and when it is needed.
While enhancing the temperature of available renewable thermal energy,
heat pumps have the additional property of leveraging electrical power
(or in some cases mechanical or thermal power) by using it to extract
additional energy from a low quality source (such as seawater, lake
water, the ground, the air, or waste heat from a process).
Thermal storage technologies allow heat or cold to be stored for
periods of time ranging from hours or overnight to
interseasonal, and can involve storage of
sensible energy (i.e. by changing the temperature of a medium) or
latent energy (i.e. through phase changes of a medium, such between
water and slush or ice). Short-term thermal storages can be used for
peak-shaving in district heating or electrical distribution systems.
Kinds of renewable or alternative energy sources that can be enabled
include natural energy (e.g. collected via solar-thermal collectors, or
dry cooling towers used to collect winter's cold), waste energy (e.g.
from HVAC equipment, industrial processes or power plants), or surplus
energy (e.g. as seasonally from hyropower projects or intermitently from
wind farms). The
Drake Landing Solar Community (Alberta, Canada) is illustrative.
borehole thermal energy storage allows the community to get 97% of
its year-round heat from solar collectors on the garage roofs, which
most of the heat collected in summer.[37][38]
Types of storages for sensible energy include insulated tanks, borehole
clusters in substrates ranging from gravel to bedrock, deep aquifers, or
shallow lined pits that are insulated on top. Some types of storage are
capable of storing heat or cold between opposing seasons (particularly
if very large), and some storage applications require inclusion of a
heat pump. Latent heat is typically stored in ice tanks or what are
called
phase-change materials (PCMs).
Renewable energy commercialization
Growth of
renewables
Renewable power generation and capacity as a proportion of
change in global power supply
[39]
Growth of wind power and photovoltaics
From the end of 2004, worldwide renewable energy capacity grew at
rates of 10–60% annually for many technologies. For wind power and many
other renewable technologies, growth accelerated in 2009 relative to the
previous four years.[12]
More wind power capacity was added during 2009 than any other renewable
technology. However, grid-connected PV increased the fastest of all
renewables technologies, with a 60% annual average growth rate.[12]
In 2010, renewable power constituted about a third of the newly built
power generation capacities.[39]
By 2014 the installed capacity of photovoltaics will likely exceed that
of wind, but due to the lower
capacity factor of solar, the energy generated from photovoltaics is
not expected to exceed that of wind until 2015.
Selected renewable energy indicators[40][41]
| Investment in new renewable capacity (annual) (109
USD) |
130 |
160 |
211 |
257 |
| Renewables power capacity (existing) (GWe) |
1,140 |
1,230 |
1,320 |
1,360 |
| Hydropower capacity (existing) (GWe) |
885 |
915 |
945 |
970 |
| Wind power capacity (existing) (GWe) |
121 |
159 |
198 |
238 |
| Solar PV capacity (grid-connected) (GWe) |
16 |
23 |
40 |
70 |
| Solar hot water capacity (existing) (GWth) |
130 |
160 |
185 |
232 |
| Ethanol production (annual) (109 litres) |
67 |
76 |
86 |
86 |
| Biodiesel production (annual) (109 litres) |
12 |
17.8 |
18.5 |
21.4 |
Countries with policy targets
for renewable energy use |
79 |
89 |
98 |
118 |
Projections vary, but scientists have advanced a plan to power 100%
of the world's energy with
wind,
hydroelectric, and
solar power by the year 2030.[42][43]
According to a 2011 projection by the International Energy Agency,
solar power generators may produce most of the world’s electricity
within 50 years, dramatically reducing the emissions of greenhouse gases
that harm the environment. Cedric Philibert, senior analyst in the
renewable energy division at the IEA said: “Photovoltaic and
solar-thermal plants may meet most of the world’s demand for electricity
by 2060 -- and half of all energy needs -- with wind, hydropower and
biomass plants supplying much of the remaining generation”.
“Photovoltaic and concentrated solar power together can become the major
source of electricity,” Philibert said.[8]
Economic trends
Cost of photovoltaics in the EU
Renewable energy technologies are getting cheaper, through
technological change and through the benefits of mass production and
market competition. A 2011 IEA report said: "A portfolio of renewable
energy technologies is becoming cost-competitive in an increasingly
broad range of circumstances, in some cases providing investment
opportunities without the need for specific economic support," and added
that "cost reductions in critical technologies, such as wind and solar,
are set to continue."[45]
Hydro-electricity and geothermal electricity produced at favourable
sites are now the cheapest way to generate electricity. Renewable energy
costs continue to drop, and the levelised cost of electricity (LCOE) is
declining for wind power, solar photovoltaic (PV), concentrated solar
power (CSP) and some biomass technologies.[46]
Renewable energy is also the most economic solution for new
grid-connected capacity in areas with good resources. As the cost of
renewable power falls, the scope of economically viable applications
increases. Renewable technologies are now often the most economic
solution for new generating capacity. Where “oil-fired generation is the
predominant power generation source (e.g. on islands, off-grid and in
some countries) a lower-cost renewable solution almost always exists
today”.[46]
Hydroelectricity
Three Gorges Dam (left), Gezhouba Dam (right).
The
Three Gorges Dam in
Hubei,
China,
has the world's largest instantaneous generating capacity (22,500 MW),
with the
Itaipu Dam in Brazil/Paraguay in second place (14,000 MW). The
Three Gorges Dam is operated jointly with the much smaller
Gezhouba Dam (3,115 MW). As of 2012, the total generating capacity
of this two-dam complex is 25,615 MW. In 2008, this complex generated
97.9 TWh of electricity (80.8 TWh from the Three Gorges Dam and 17.1 TWh
from the Gezhouba Dam), which is 3.4% more power in one year than the
94.7 TWh generated by Itaipu in 2008.
Wind power
development
Wind power: worldwide installed capacity
[47]
Wind power is growing at over 20% annually, with a worldwide
installed capacity of 238,000 MW at the end of 2011,[40][48][49]
and is widely used in
Europe,
Asia, and the
United States.[50][51]
Several countries have achieved relatively high levels of wind power
penetration, such as 21% of stationary electricity production in
Denmark,[52]
18% in
Portugal,[52]
16% in
Spain,[52]
14% in
Ireland[53]
and 9% in
Germany in 2010.[33][52]
As of 2011, 83 countries around the world are using wind power on a
commercial basis.[33]
Top 10 countries by nameplate windpower capacity
(2012 year-end)[54]
|
China |
75,564ǂ |
26.8 |
|
United States |
60,007 |
21.2 |
|
Germany |
31,332 |
11.1 |
|
Spain |
22,796 |
8.1 |
|
India |
18,421 |
6.5 |
|
United Kingdom |
8,845 |
3.0 |
|
Italy |
8,144 |
2.9 |
|
France |
7,196ǂ |
2.5 |
|
Canada |
6,200 |
2.2 |
|
Portugal |
4,525 |
1.6 |
| (rest
of world) |
39,853 |
14.1 |
| World total |
282,482 MW |
100% |
As of 2012, the
Alta Wind Energy Center (California, 1,020 MW) is the world's
largest wind farm.[55]
As of February 2012, the
Walney Wind Farm in the
United Kingdom is the largest offshore wind farm in the world at 367
MW, followed by
Thanet Offshore Wind Project (300 MW), also in the UK. The
London Array (630 MW) is the largest project under construction. The
United Kingdom is the world's leading generator of offshore wind
power, followed by Denmark.[56]
There are many large wind farms under construction and these include
Anholt Offshore Wind Farm (400 MW),
BARD Offshore 1 (400 MW),
Clyde Wind Farm (548 MW),
Fântânele-Cogealac Wind Farm (600 MW),
Greater Gabbard wind farm (500 MW),
Lincs Wind Farm (270 MW),
London Array (1000 MW),
Lower Snake River Wind Project (343 MW),
Macarthur Wind Farm (420 MW),
Shepherds Flat Wind Farm (845 MW), and the
Sheringham Shoal (317 MW).
Solar thermal
Large
solar thermal power stations include the 354 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 plant (Spain, 20 MW), and the
PS10 Solar Power Plant (Spain, 11 MW).
The
Ivanpah Solar Power Facility is a 392 MW solar power facility which
is under construction in south-eastern California.[57]
The
Solana Generating Station is a 280 MW
solar power plant which is under construction near
Gila Bend,
Arizona,
about 70 miles (110 km) southwest of
Phoenix. The
Crescent Dunes Solar Energy Project is a 110 MW
solar thermal power project currently under construction near
Tonopah, about 190 miles (310 km) northwest of
Las Vegas.[58]
The solar thermal power industry is growing rapidly with 1.3 GW under
construction in 2012 and more planned. Spain is the epicenter of solar
thermal power development with 873 MW under construction, and a further
271 MW under development.[59]
In the United States, 5,600 MW of solar thermal power projects have been
announced.[60]
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.[61]
Photovoltaic power stations
Photovoltaic power
(GW)[62] |
| 2005 |
5.4 |
| 2006 |
7.0 |
| 2007 |
9.4 |
| 2008 |
15.7 |
| 2009 |
22.9 |
| 2010 |
39.7 |
| 2011 |
67.4 |
| 2012 |
100 |
| Year end capacities |
Solar photovoltaic cells (PV) convert sunlight into electricity and
photovoltaic production has been increasing by an average of more than
20% each year since 2002, making it a fast-growing energy technology.[63][64]
While wind is often cited as the fastest growing energy source,
photovoltaics since 2007 has been increasing at twice the rate of wind -
an average of 63.6%/year, due to the reduction in cost. At the end of
2011 the
photovoltaic (PV) capacity world-wide was 67.4 GW, a 69.8% annual
increase. Top capacity countries were, in GW:
Germany 24.7,
Italy 12.8,
Japan 4.7,
Spain 4.4,
the USA 4.4, and
China 3.1.[62][65]
Many solar photovoltaic power stations have been built, mainly in
Europe.[66]
As of May 2012, the largest photovoltaic (PV) power plants in the world
are the
Agua Caliente Solar Project (USA, 247 MW),
Charanka Solar Park (India, 214 MW),
Golmud Solar Park (China, 200 MW),
Perovo Solar Park (Ukraine, 100 MW),
Sarnia Photovoltaic Power Plant (Canada, 97 MW),
Brandenburg-Briest Solarpark (Germany, 91 MW),
Solarpark Finow Tower (Germany, 84.7 MW),
Montalto di Castro Photovoltaic Power Station (Italy, 84.2 MW), and
the
Eggebek Solar Park (Germany, 83.6 MW).[66]
There are also many large plants under construction. The
Desert Sunlight Solar Farm is a 550 MW solar power plant under
construction in
Riverside County, California, that will use thin-film solar
photovoltaic modules made by
First Solar.[67]
The
Topaz Solar Farm is a 550 MW photovoltaic power plant, being built
in
San Luis Obispo County, California.[68]
The
Blythe Solar Power Project is a 500 MW photovoltaic station under
construction in
Riverside County, California. The
California Valley Solar Ranch (CVSR) is a 250 MW
solar photovoltaic
power plant, which is being built by
SunPower in the
Carrizo Plain, northeast of
California Valley.[69]
The 230 MW
Antelope Valley Solar Ranch is a
First Solar photovoltaic project which is under construction in the
Antelope Valley area of the Western Mojave Desert, and due to be
completed in 2013.[70]
Many of these plants are integrated with agriculture and some use
tracking systems that follow the sun's daily path across the sky to
generate more electricity than fixed-mounted systems. There are no fuel
costs or emissions during operation of the power stations.
However, when it comes to renewable energy systems and PV, it is not
just large systems that matter.
Building-integrated photovoltaics or "onsite" PV systems use
existing land and structures and generate power close to where it is
consumed.[71]
Biofuel
development
Biofuels provided 3% of the world's transport
fuel in
2010.[33]
Mandates for blending biofuels exist in 31 countries at the national
level and in 29 states/provinces.[33]
According to the International Energy Agency, biofuels have the
potential to meet more than a quarter of world demand for transportation
fuels by 2050.[72]
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.[73]
Brazil’s ethanol fuel program uses modern equipment and cheap
sugarcane as feedstock, and the residual cane-waste (bagasse)
is used to produce heat and power.[74]
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.[75]
Nearly all the gasoline sold in the United States today is mixed with
10% ethanol, a mix known as E10,[76]
and motor vehicle manufacturers already produce vehicles designed to run
on much higher ethanol blends.
Ford,
Daimler AG, 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 6 million E85-compatible vehicles on U.S. roads.[77]
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 US
gallons (28,000,000 m3) of biofuels to be used annually by
2012, will also help to expand the market.[77]
Geothermal
development
The West Ford Flat power plant is one of 22 power plants at
The Geysers.
Geothermal power is cost effective, reliable, sustainable, and
environmentally friendly,[78]
but has historically been limited to areas near
tectonic plate boundaries. Recent technological advances have
dramatically expanded the range and size of viable resources, especially
for applications such as home heating, opening a potential for
widespread exploitation. Geothermal wells release greenhouse gases
trapped deep within the earth, but these emissions are much lower per
energy unit than those of fossil fuels. As a result, geothermal power
has the potential to help mitigate
global warming if widely deployed in place of fossil fuels.
The International Geothermal Association (IGA) has reported that
10,715 MW of geothermal power in 24 countries is online, which is
expected to generate 67,246 GWh of electricity in 2010.[79]
This represents a 20% increase in geothermal power online capacity since
2005. IGA projects this will grow to 18,500 MW by 2015, due to the large
number of projects presently under consideration, often in areas
previously assumed to have little exploitable resource.[79]
In 2010, the
United States led the world in
geothermal electricity production with 3,086 MW of installed
capacity from 77 power plants;[80]
the largest group of geothermal power plants in the world is located at
The Geysers, a geothermal field in
California.[81]
The Philippines follows the US as the second highest producer of
geothermal power in the world, with 1,904 MW of capacity online;
geothermal power makes up approximately 18% of the country's electricity
generation.[80]
Developing
countries
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.[82]
Technology advances are opening up a huge new market for solar power:
the approximately 1.3 billion people around the world who don't have
access to grid electricity. Even though they are typically very poor,
these people have to pay far more for lighting than people in rich
countries because they use inefficient kerosene lamps. Solar power costs
half as much as lighting with kerosene.[83]
An estimated 3 million households get power from small solar PV systems.[84]
Kenya is the world leader in the number of solar power systems installed
per capita. More than 30,000 very small solar panels, each producing 12
to 30 watts, are sold in Kenya annually. Some
Small Island Developing States (SIDS) are also turning to solar
power to reduce their costs and increase their sustainability.[85]
Micro-hydro configured into mini-grids also provide power. Over 44
million households use
biogas
made in household-scale digesters for
lighting and/or
cooking,
and more than 166 million households rely on a new generation of
more-efficient biomass cookstoves.[4]
Clean liquid fuel sourced from renewable feedstocks are used for cooking
and lighting in energy-poor areas of the developing world. Alcohol fuels
(ethanol and methanol) can be produced sustainably from non-food sugary,
starchy, and cellulostic feedstocks. Project Gaia, Inc. and CleanStar
Mozambique are implementing clean cooking programs with liquid ethanol
stoves in Ethiopia, Kenya, Nigeria and Mozambique.[86]
Renewable energy projects in many developing countries have
demonstrated that renewable energy can directly contribute to
poverty alleviation by providing 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.[87]
Industry
and policy trends
Global New Investments in Renewable Energy
[88]
U.S. President
Barack Obama'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
malaise.[7]
Leading renewable energy companies include
First Solar,
Gamesa,
GE
Energy,
Q-Cells,
Sharp Solar,
Siemens,
SunOpta,
Suntech Power, and
Vestas.[89]
The military has also focused on the use of
renewable fuels for military vehicles. Unlike fossil fuels,
renewable fuels can be produced in any country, creating a strategic
advantage. The US military has already committed itself to have 50% of
its energy consumption come from alternative sources.[90]
The
International Renewable Energy Agency (IRENA) is an
intergovernmental organization for promoting the
adoption of renewable energy worldwide. It aims to provide concrete
policy advice and facilitate
capacity building and technology transfer. IRENA was formed on
January 26, 2009, by 75 countries signing the charter of IRENA.[91]
As of March 2010, IRENA has 143 member states who all are considered as
founding members, of which 14 have also ratified the statute.[92]
As of 2011, 119 countries have some form of national
renewable energy policy target or renewable support policy. National
targets now exist in at least 98 countries. There is also a wide range
of policies at state/provincial and local levels.[33]
United Nations' Secretary-General
Ban Ki-moon has said that renewable energy has the ability to lift
the poorest nations to new levels of prosperity.[5]
In October 2011, he "announced the creation of a high-level group to
drum up support for energy access, energy efficiency and greater use of
renewable energy. The group is to be co-chaired by Kandeh Yumkella, the
chair of UN Energy and director general of the UN Industrial Development
Organisation, and Charles Holliday, chairman of Bank of America".[93]
100%
renewable energy
Growth of wind and solar power
Renewable energy use has grown much faster than anyone anticipated.[94]
Wind turbines generate nearly 30 percent of Danish electricity, and
Denmark has many biogas digesters and waste-to-energy plants as well.
Together, wind and biomass provide 44% of the electricity consumed by
the country's six million inhabitants. In 2010, Portugal’s 10 million
people produced more than half their electricity from indigenous
renewable energy resources. Spain’s 40 million inhabitants meet
one-third of their electrical needs from renewables.[94]
The incentive to use 100% renewable energy is created by
global warming and ecological as well as economic concerns, post
peak
oil. The first country to propose 100% renewable energy was Iceland,
in 1998.[95]
Proposals have been made for Japan in 2003,[96]
and for Australia in 2011.[97]
Norway and some
other countries already obtain all of their electricity from
renewable sources. Iceland proposed using hydrogen for transportation
and its fishing fleet. Australia proposed biofuel for those elements of
transportation not easily converted to electricity. The road map for the
United States,[98][99]
commitment by Denmark,[100]
and Vision 2050 for Europe set a 2050 timeline for converting to 100%
renewable energy,[101]
later reduced to 2040 in 2011.[102]
Zero Carbon Britain 2030 proposes eliminating carbon emissions in
Britain by 2030 by transitioning to renewable energy.[103]
It is estimated that the world will spend an extra $8 trillion over
the next 25 years to prolong the use of non-renewable resources, a cost
that would be eliminated by transitioning instead to 100% renewable
energy.[104]
A 2009 study suggests that converting the entire world to 100% renewable
energy by 2030 is both possible and affordable, but requires political
support. It would require building many more wind turbines and solar
power systems. Other changes involve use of
electric cars and the development of enhanced transmission grids and
storage.[105][106][107][108][109]
The Fourth Revolution: Energy is a German
documentary film released in 2010. It shows the vision of a global
society, which lives in a world where the energy is produced 100% with
renewable energies, showing a complete reconstruction of the economy, to
reach this goal. In 2011,
Hermann Scheer wrote the book The Energy Imperative: 100 Percent
Renewable Now, published by Routledge.
In 2011, the
Intergovernmental Panel on Climate Change, the world's leading
climate scientists convened by the United Nations, said "as
infrastructure and energy systems develop, in spite of the complexities,
there are few, if any, fundamental technological limits to integrating a
portfolio of renewable energy technologies to meet a majority share of
total energy demand in locations where suitable renewable resources
exist or can be supplied".[110]
IPCC scenarios "generally indicate that growth in renewable energy will
be widespread around the world".[111]
The IPCC said that if governments were supportive, and the full range of
renewable technologies were deployed, renewable energy could account for
almost 80% of the world's energy supply within four decades.[112]
Rajendra Pachauri, chairman of the IPCC, said the necessary
investment in renewables would cost only about 1% of global GDP
annually. This approach could keep greenhouse gas concentrations to less
than 450 parts per million, the safe level beyond which climate change
becomes catastrophic and irreversible.[112]
In 2011, the refereed journal Energy Policy published two
articles by
Mark Z. Jacobson, a professor of engineering at
Stanford University, and Mark A. Delucchi, about changing our energy
supply mix and "Providing all global energy with wind, water, and solar
power". The articles analyze the feasibility of providing worldwide
energy for electric power, transportation, and heating/cooling from
wind, water, and sunlight (WWS), which are safe clean options. In Part
I, Jacobson and Delucchi discuss WWS energy system characteristics,
aspects of energy demand, WWS resource availability, WWS devices needed,
and material requirements.[113]
They estimate that 3,800,000 5 MW
wind turbines, 5350 100 MW
geothermal power plants, and 270 new 1300 MW
hydroelectric power plants will be required. In terms of
solar power, an additional 49,000 300 MW
concentrating solar plants, 40,000 300 MW
solar photovoltaic power plants, and 1.7 billion 3 kW rooftop
photovoltaic systems will also be needed. Such an extensive WWS
infrastructure could decrease world power demand by 30%.[113]
In Part II, Jacobson and Delucchi address variability of supply, system
economics, and energy policy initiatives associated with a WWS system.
The authors advocate producing all new energy with WWS by 2030 and
replacing existing energy supply arrangements by 2050. Barriers to
implementing the renewable energy plan are seen to be "primarily social
and political, not technological or economic". Energy costs with a WWS
system should be similar to today's energy costs.[114]
NASA
Climate scientist
James Hansen and
Environmentalists for nuclear energy in general, however do not
agree, with Hansen describing the idea of a modern world run on
renewable energy as equivalent to: "believing in the Easter Bunny and
Tooth Fairy".[115]
In general, Jacobson has said wind, water and solar technologies can
provide 100 per cent of the world's energy, eliminating all
fossil fuels.[116]
He 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 gaps.[42]
A 2012 study by the University of Delaware for a 72 GW system
considered 28 billion combinations of renewable energy and storage and
found the most cost effective, for the
PJM Interconnection, would use 17 GW of solar, 68 GW of offshore
wind, and 115 GW of onshore wind, although at times as much as three
times the demand would be provided. 0.1% of the time would require
generation from other sources.[117]
In March 2012, Denmark's parliament agreed on a comprehensive new set
promotional programs for energy efficiency and renewable energy that
will lead to the country getting 100 percent of electricity, heat and
fuels from renewables by 2050.[118]
IRENEC is an annual conference on 100% renewable energy started in
2011 by EUROSOLAR Turkey. The 2013 conference is scheduled for June
27–29 in Istanbul.[119][120]
Emerging
technologies
Other renewable energy technologies are still under development, and
include
cellulosic ethanol,
hot-dry-rock geothermal power, and
ocean energy.[121]
These technologies are not yet widely demonstrated or have limited
commercialization. Many are on the horizon and may have potential
comparable to other renewable energy technologies, but still depend on
attracting sufficient attention and research, development and
demonstration (RD&D) funding.[121]
Research
There are numerous organizations within the academic, federal, and
commercial sectors conducting large scale advanced research in the field
of renewable energy. This research spans several areas of focus across
the renewable energy spectrum. Most of the research is targeted at
improving efficiency and increasing overall energy yields.[122]
Multiple federally supported research organizations have focused on
renewable energy in recent years. Two of the most prominent of these
labs are
Sandia National Laboratories and the
National Renewable Energy Laboratory (NREL), both of which are
funded by the
United States Department of Energy and supported by various
corporate partners.[123]
Sandia has a total budget of $2.4 billion[124]
while NREL has a budget of $375 million.[125]
Cellulosic ethanol
Companies such as
Iogen, POET,
and
Abengoa are building refineries that can process biomass and turn it
into ethanol, while companies such as the
Verenium Corporation,
Novozymes, and
Dyadic International are producing enzymes which could enable a
cellulosic ethanol future. The shift from food crop feedstocks to
waste residues and native grasses offers significant opportunities for a
range of players, from farmers to biotechnology firms, and from project
developers to investors.[126]
Ocean energy
Main article:
Ocean energyOcean energy is a broad category currently encompassing:
Marine current power,
Osmotic power,
Wave power,
Tidal power, and
Ocean thermal energy.
Wave Power
Systems to harvest utility-scale electrical power from ocean waves
have recently been gaining momentum as a viable technology. The
potential for this technology is considered promising, especially on
west-facing coasts with latitudes between 40 and 60 degrees:[129]
In the United Kingdom, for example, the Carbon Trust recently
estimated the extent of the economically viable offshore resource at 55
TWh per year, about 14% of current national demand. Across Europe, the
technologically achievable resource has been estimated to be at least
280 TWh per year. In 2003, the U.S. Electric Power Research Institute
(EPRI) estimated the viable resource in the United States at 255 TWh per
year (6% of demand).[129]
Scotland is home to the
European Marine Energy Centre the world's first testing facility for
wave and tidal machines, located in the waters around the
Orkney
Islands. In 2012 at the wave test site,
E.ON are
testing a
Pelamis Wave Energy Converter machine and
Aquamarine Power are testing their near-shore Oyster device. Wave
farm developments are planned in Scottish waters by
E.ON,
ScottishPower Renewables,
SSE,
Pelamis Wave Power,
Aquamarine Power and Aegir Wave Power, a joint venture between
Pelamis and
Vattenfall.[130]
In the
U.S.,
Australia, as well as in Europe, full scale
Wave
power projects are underway or in planning by
Ocean Power Technologies, as well as others, such as
CETO.
Tidal Power
Main article:
Tidal powerThe world's first commercial
tidal stream generator was installed in 2007 in the narrows of
Strangford Lough in Ireland. The 1.2 MW underwater tidal electricity
generator, part of Northern Ireland's Environment & Renewable Energy
Fund scheme, takes advantage of the fast tidal flow (up to 4 metres per
second) in the lough. Although the generator is powerful enough to power
a thousand homes, the turbine has minimal environmental impact, as it is
almost entirely submerged, and the rotors pose no danger to wildlife as
they turn quite slowly.[131]
Ocean thermal
energy
Ocean thermal energy conversion (OTEC) uses the temperature
difference that exists between deep and shallow waters to run a heat
engine.
Enhanced
geothermal systems
Enhanced geothermal system 1:Reservoir 2:Pump house
3:Heat exchanger 4:Turbine hall 5:Production well
6:Injection well 7:Hot water to district heating
8:Porous sediments 9:Observation well 10:Crystalline bedrock
Enhanced geothermal systems are a new type of
geothermal power technologies that do not require natural convective
hydrothermal resources. The vast majority of geothermal energy within
drilling reach is in dry and non-porous rock.[132]
EGS technologies "enhance" and/or create geothermal resources in this
"hot dry rock (HDR)" through
hydraulic stimulation.
EGS / HDR technologies, like hydrothermal geothermal, are expected to
be baseload resources which produce power 24 hours a day like a fossil
plant. Distinct from hydrothermal, HDR / EGS may be feasible anywhere in
the world, depending on the economic limits of drill depth. Good
locations are over deep
granite
covered by a thick (3–5 km) layer of insulating sediments which slow
heat loss.[133]
There are HDR and EGS systems currently being developed and tested in
France,
Australia,
Japan,
Germany, the
U.S. and
Switzerland. The largest EGS project in the world is a 25 megawatt
demonstration plant currently being developed in the Cooper Basin,
Australia. The Cooper Basin has the potential to generate
5,000–10,000 MW.
Experimental
solar power
Concentrating photovoltaics in Catalonia, Spain
Concentrated photovoltaics (CPV) systems employ sunlight
concentrated onto photovoltaic surfaces for the purpose of
electricity generation.
Thermoelectric, or "thermovoltaic" devices convert a temperature
difference between dissimilar materials into an electric current.
Artificial
photosynthesis
Artificial photosynthesis uses techniques include
nanotechnology to store solar electromagnetic energy in chemical
bonds by splitting water to produce hydrogen and then using carbon
dioxide to make methanol.[134]
Researchers in this field are striving to design molecular mimics of
photosynthesis that utilize a wider region of the solar spectrum, employ
catalytic systems made from abundant, inexpensive materials that are
robust, readily repaired, non-toxic, stable in a variety of
environmental conditions and perform more efficiently allowing a greater
proportion of photon energy to end up in the storage compounds, i.e.,
carbohydrates (rather than building and sustaining living cells).
Relevant approaches utilize coordination chemistry, material science and
modified bio-engineered, synthetic biomimetic and bio-inspired
techniques, as well as nanosciences, to construct photo-semiconductors
and solid state catalysts for water oxidation, plus hydrogen evolution
catalysts based on enzymes.[135]
Renewable
energy debate
Renewable electricity production, from sources such as
wind power and
solar power, is sometimes criticized for being variable or
intermittent. However, the
International Energy Agency has stated that deployment of renewable
technologies usually increases the diversity of electricity sources and,
through local generation, contributes to the flexibility of the system
and its resistance to central shocks.[136]
There have been "not
in my back yard" (NIMBY) concerns relating to the visual and other
impacts of some
wind
farms, with local residents sometimes fighting or blocking
construction.[137]
In the USA, the Massachusetts
Cape
Wind project was delayed for years partly because of aesthetic
concerns. However, residents in other areas have been more positive.
According to a town councilor, the overwhelming majority of locals
believe that the
Ardrossan Wind Farm in Scotland has enhanced the area.[138]
A recent UK Government document states that “projects are generally
more likely to succeed if they have broad public support and the consent
of local communities. This means giving communities both a say and a
stake”.[139]
In countries such as Germany and Denmark many renewable projects are
owned by communities, particularly through
cooperative structures, and contribute significantly to overall
levels of renewable energy deployment.[140][141]
In recent years, new online
crowdfunding platforms have provided additional mechanisms for
broader participation in, and support for, renewable energy by allowing
anyone to invest even small amounts and benefit from the returns.
Examples include
Abundance Generation in the UK
[142] and Solar Mosaic in the USA.
The market for renewable energy technologies has continued to grow.
Climate change concerns, coupled with
high oil prices,
peak
oil, and increasing government support, are driving increasing
renewable energy legislation, incentives and
commercialization.[6]
New government spending, regulation and policies helped the industry
weather the 2009 economic crisis better than many other sectors.[7]