There
are many sources of energy that are renewable and considered to be
environmentally friendly and harness natural processes. These sources of
energy provide an alternate ‘cleaner’ source of energy, helping to
negate the effects of certain forms of pollution. All of these power
generation techniques can be described as renewable since they are not
depleting any resource to create the energy. While there are many
large-scale renewable energy projects and production, renewable
technologies are also suited to small off-grid applications, sometimes
in rural and remote areas, where energy is often crucial in human
development.
Tidal Power
Tidal
energy can be generated in two ways, tidal stream generators or by
barrage generation. The power created though tidal generators is
generally more environmentally friendly and causes less impact on
established ecosystems. Similar to a wind turbine, many tidal stream
generators rotate underwater and is driven by the swiftly moving dense
water. Although not yet widely used, tidal power has potential for
future electricity generation. Tides are more predictable than wind
energy and solar power. Historically, tide mills have been used, both in
Europe and on the Atlantic coast of the USA. The earliest occurrences
date from the Middle Ages, or even from Roman times. Tidal power is the
only form of energy which derives directly from the relative motions of
the Earth–Moon system, and to a lesser extent from the Earth–Sun system.
The tidal forces produced by the Moon and Sun, in combination with
Earth’s rotation, are responsible for the generation of the tides.
British company Lunar Energy announced that they would be building the
world’s first tidal energy farm off the coast of Pembrokshire in Wales.
It will be the world’s first deep-sea tidal-energy farm and will provide
electricity for 5,000 homes. Eight underwater turbines, each 25 metres
long and 15 metres high, are to be installed on the sea bottom off St
David’s peninsula. Construction is due to start in the summer of 2008
and the proposed tidal energy turbines, described as “a wind farm under
the sea”, should be operational by 2010.
Wave Power
Wave
power is the transport of energy by ocean surface waves, and the
capture of that energy to do useful work — for example for electricity
generation, water desalination, or the pumping of water (into
reservoirs). Wave energy can be difficult to harness due to the
unpredictability of the ocean and wave direction. Wave farms have been
created and are in use in Europe, using floating Pelamis Wave Energy
converters. Most wave power systems include the use of a floating buoyed
device and generate energy through a snaking motion, or by mechanical
movement from the waves peaks and troughs. Though often co-mingled, wave
power is distinct from the diurnal flux of tidal power and the steady
gyre of ocean currents. Wave power generation is not currently a widely
employed commercial technology although there have been attempts at
using it since at least 1890. The world’s first commercial wave farm is
based in Portugal, at the Aguçadora Wave Park, which consists of three
750 kilowatt Pelamis devices. In the United States, the Pacific
Northwest Generating Cooperative is funding the building of a commercial
wave-power park at Reedsport, Oregon. The project will utilize the
PowerBuoy technology Ocean Power Technologies which consists of modular,
ocean-going buoys. The rising and falling of the waves moves the
buoy-like structure creating mechanical energy which is converted into
electricity and transmitted to shore over a submerged transmission line.
A 40 kW buoy has a diameter of 12 feet (4 m) and is 52 feet (16 m)
long, with approximately 13 feet of the unit rising above the ocean
surface. Using the three-point mooring system, they are designed to be
installed one to five miles (8 km) offshore in water 100 to 200 feet (60
m) deep.
Solar Power
Photovoltaic
(PV) Solar power is harnessing the suns energy to produce electricity.
One of the fastest growing energy sources, new technologies are
developing at a rapid pace. Solar cells are becoming more efficient,
transportable and even flexible, allowing for easy installation. PV has
mainly been used to power small and medium-sized applications, from the
calculator powered by a single solar cell to off-grid homes powered by a
photovoltaic array. The 1973 oil crisis stimulated a rapid rise in the
production of PV during the 1970s and early 1980s. Steadily falling oil
prices during the early 1980s, however, led to a reduction in funding
for photovoltaic R&D and a discontinuation of the tax credits
associated with the Energy Tax Act of 1978. These factors moderated
growth to approximately 15% per year from 1984 through 1996. Since the
mid-1990s, leadership in the PV sector has shifted from the US to Japan
and Germany. Between 1992 and 1994 Japan increased R&D funding,
established net metering guidelines, and introduced a subsidy program to
encourage the installation of residential PV systems. Solar
installations in recent years have also largely begun to expand into
residential areas, with governments offering incentive programs to make
“green” energy a more economically viable option. In Canada the
government offers the RESOP (Renewable Energy Standard Offer Program).
Wind Power
Wind
power is the conversion of wind energy by wind turbines into a useful
form, such as electricity or mechanical energy. Large-scale wind farms
are typically connected to the local power transmission network with
small turbines used to provide electricity to isolated areas.
Residential units are entering production and are are capable of
powering large appliances to entire houses depending on the size. Wind
farms installed on agricultural land or grazing areas, have one of the
lowest environmental impacts of all energy sources. Although wind
produces only about 1.5% of worldwide electricity use, it is growing
rapidly, having doubled in the three years between 2005 and 2008. In
several countries it has achieved relatively high levels of penetration,
accounting for approximately 19% of electricity production in Denmark,
11% in Spain and Portugal, and 7% in Germany and the Republic of Ireland
in 2008. Wind energy has historically been used directly to propel
sailing ships or converted into mechanical energy for pumping water or
grinding grain, but the principal application of wind power today is the
generation of electricity. As of 2008, Europe leads the world in
development of offshore wind power, due to strong wind resources and
shallow water in the North Sea and the Baltic Sea, and limitations on
suitable locations on land due to dense populations and existing
developments. Denmark installed the first offshore wind farms, and for
years was the world leader in offshore wind power until the United
Kingdom gained the lead in October, 2008. Other large markets for wind
power, including the United States and China focused first on developing
their on-land wind resources where construction costs are lower (such
as in the Great Plains of the U.S., and the similarly wind-swept steppes
of Xinjiang and Inner Mongolia in China), but population centers along
coastlines in many parts of the world are close to offshore wind
resources, which would reduce transmission costs.
Hydroelectricity
Hydroelectricity
is electricity generated by hydropower, i.e., the production of power
through use of the gravitational force of falling or flowing water. It
is the most widely used form of renewable energy. Once a hydroelectric
complex is constructed, the project produces no direct waste. Small
scale hydro or micro-hydro power has been an increasingly popular
alternative energy source, especially in remote areas where other power
sources are not viable. Small scale hydro power systems can be installed
in small rivers or streams with little or no discernible environmental
effect or disruption to fish migration. Most small scale hydro power
systems make no use of a dam or major water diversion, but rather use
water wheels to generate energy. This was approximately 19% of the
world’s electricity (up from 16% in 2003), and accounted for over 63% of
electricity from renewable sources. While many hydroelectric projects
supply public electricity networks, some are created to serve specific
industrial enterprises. Dedicated hydroelectric projects are often built
to provide the substantial amounts of electricity needed for aluminium
electrolytic plants, for example. In the Scottish Highlands there are
examples at Kinlochleven and Lochaber, constructed during the early
years of the 20th century. The Grand Coulee Dam, long the world’s
largest, switched to support Alcoa aluminum in Bellingham, Washington
for America’s World War II airplanes before it was allowed to provide
irrigation and power to citizens (in addition to aluminum power) after
the war. In Suriname, the Brokopondo Reservoir was constructed to
provide electricity for the Alcoa aluminium industry. New Zealand’s
Manapouri Power Station was constructed to supply electricity to the
aluminium smelter at Tiwai Point.
Radiant Energy
This
natural energy can perform the same wonders as ordinary electricity at
less than 1% of the cost. It does not behave exactly like electricity,
however, which has contributed to the scientific community’s
misunderstanding of it. The Methernitha Community in Switzerland
currently has 5 or 6 working models of fuelless, self-running devices
that tap this energy. Nikola Tesla’s magnifying transmitter, T. Henry
Moray’s radiant energy device, Edwin Gray’s EMA motor, and Paul
Baumann’s Testatika machine all run on radiant energy. This natural
energy form can be gathered directly from the environment or extracted
from ordinary electricity by the method called fractionation. One of the
earliest wireless telephones to be based on radiant energy was invented
by Nikola Tesla. The device used transmitters and receivers whose
resonances were tuned to the same frequency, allowing communication
between them. In 1916, he recounted an experiment he had done in 1896.
He recalled that “Whenever I received the effects of a transmitter, one
of the simplest ways [to detect the wireless transmissions] was to apply
a magnetic field to currents generated in a conductor, and when I did
so, the low frequency gave audible notes.”
Geothermal Power
Geothermal
energy is a very powerful and efficient way to extract a renewable
energy from the earth through natural processes. This can be performed
on a small scale to provide heat for a residential unit (a geothermal
heat pump), or on a very large scale for energy production through a
geothermal power plant. It has been used for space heating and bathing
since ancient roman times, but is now better known for generating
electricity. Geothermal power is cost effective, reliable, and
environmentally friendly, but has previously been geographically limited
to areas near tectonic plate boundaries. Recent technological advances
have dramatically expanded the range and size of viable resources,
especially for direct applications such as home heating. The largest
group of geothermal power plants in the world is located at The Geysers,
a geothermal field in California, United States. As of 2004, five
countries (El Salvador, Kenya, the Philippines, Iceland, and Costa Rica)
generate more than 15% of their electricity from geothermal sources.
Geothermal power requires no fuel, and is therefore immune to
fluctuations in fuel cost, but capital costs tend to be high. Drilling
accounts for most of the costs of electrical plants, and exploration of
deep resources entails very high financial risks. Geothermal power
offers a degree of scalability: a large geothermal plant can power
entire cities while smaller power plants can supply rural villages or
heat individual homes. Geothermal electricity is generated in 24
countries around the world and a number of potential sites are being
developed or evaluated.
Biomass
Biomass,
as a renewable energy source, refers to living and recently dead
biological material that can be used as fuel or for industrial
production. In this context, biomass refers to plant matter grown to
generate electricity or produce for example trash such as dead trees and
branches, yard clippings and wood chips biofuel, and it also includes
plant or animal matter used for production of fibers, chemicals or heat.
Biomass may also include biodegradable wastes that can be burnt as
fuel. Industrial biomass can be grown from numerous types of plants,
including miscanthus, switchgrass, hemp, corn, poplar, willow, sorghum,
sugarcane, and a variety of tree species, ranging from eucalyptus to oil
palm (palm oil). The particular plant used is usually not important to
the end products, but it does affect the processing of the raw material.
Production of biomass is a growing industry as interest in sustainable
fuel sources is growing. The existing commercial biomass power
generating industry in the United States produces about 0.5 percent of
the U.S. electricity supply. Currently, the New Hope Power Partnership
is the largest biomass power plant in North America. The facility
reduces dependence on oil by more than one million barrels per year, and
by recycling sugar cane and wood waste, preserves landfill space in
urban communities in Florida.
Compressed Natural Gas
Compressed
Natural Gas (CNG) is a fossil fuel substitute for gasoline, diesel, or
propane fuel. Although its combustion does produce greenhouse gases, it
is a more environmentally clean alternative to those fuels, and it is
much safer than other fuels in the event of a spill (natural gas is
lighter than air, and disperses quickly when released). CNG is used in
traditional gasoline internal combustion engine cars that have been
converted into bi-fuel vehicles (gasoline/CNG). Natural gas vehicles are
increasingly used in Europe and South America due to rising gasoline
prices. In response to high fuel prices and environmental concerns, CNG
is starting to be used also in light-duty passenger vehicles and pickup
trucks, medium-duty delivery trucks, transit and school buses, and
trains. Italy currently has the largest number of CNG vehicles in Europe
and is the 4th country in the world for number of CNG-powered vehicles
in circulation. Canada is a large producer of natural gas, so it follows
that CNG is used in Canada as an economical motor fuel. Canadian
industry has developed CNG-fueled truck and bus engines, CNG-fueled
transit buses, and light trucks and taxis. Both CNG and propane
refueling stations are not difficult to find in major centers. During
the 1970s and 1980s, CNG was commonly used in New Zealand in the wake of
the oil crises, but fell into decline after petrol prices receded.
Nuclear Power
Nuclear
power is any nuclear technology designed to extract usable energy from
atomic nuclei via controlled nuclear reactions. The only method in use
today is through nuclear fission, though other methods might one day
include nuclear fusion and radioactive decay. All utility-scale reactors
heat water to produce steam, which is then converted into mechanical
work for the purpose of generating electricity or propulsion. In 2007,
14% of the world’s electricity came from nuclear power, with the U.S.,
France, and Japan together accounting for 56.5% of nuclear generated
electricity. There are 439 nuclear power reactors in operation in the
world, operating in 31 countries. According to the World Nuclear
Association, globally during the 1980s one new nuclear reactor started
up every 17 days on average, and by the year 2015 this rate could
increase to one every 5 days. According to a 2007 story broadcast on 60
Minutes, nuclear power gives France the cleanest air of any
industrialized country, and the cheapest electricity in all of Europe.
France reprocesses its nuclear waste to reduce its mass and make more
energy. Reprocessing can potentially recover up to 95% of the remaining
uranium and plutonium in spent nuclear fuel, putting it into new mixed
oxide fuel. This produces a reduction in long term radioactivity within
the remaining waste, since this is largely short-lived fission products,
and reduces its volume by over 90%. France is generally cited as the
most successful reprocessor, but it presently only recycles 28% (by
mass) of the yearly fuel use, 7% within France and another 21% in
Russia.
Proponents
of nuclear energy contend that nuclear power is a sustainable energy
source that reduces carbon emissions and increases energy security by
decreasing dependence on foreign oil. Proponents also emphasize that the
risks of storing waste are small and can be further reduced by using
the latest technology in newer reactors, and the operational safety
record in the Western World is excellent when compared to the other
major kinds of power plants. Critics believe that nuclear power is a
potentially dangerous energy source, with decreasing proportion of
nuclear energy in power production, and dispute whether the risks can be
reduced through new technology. Proponents advance the notion that
nuclear power produces virtually no air pollution, in contrast to the
chief viable alternative of fossil fuel. Proponents also point out that
nuclear power is the only viable course to achieve energy independence
for most Western countries. Critics point to the issue of storing
radioactive waste, the history of and continuing potential for
radioactive contamination by accident or sabotage, the history of and
continuing possibility of nuclear proliferation and the disadvantages of
centralized electricity production.