Renewable Energy
Renewable
energy is energy derived from "natural processes ongoing", such as
solar power, wind power, water flow biological processes, and geothermal.
To
find out more about the use of renewable energy in modern society, see the
development of renewable energy. For
a general discussion, see future energy development.
The
definition of "Renewable".
The
concept of renewable energy to fame in the 1970s, in an effort to offset the
development of nuclear energy and fossil fuel. The
most common definition is the energy source that can be quickly restored back
naturally, and the process is ongoing. By
this definition, the nuclear and fossil fuels are not included in it.
Sustainable
Energy
By
definition, all renewable energy is certainly also a sustainable energy,
because always available in nature in a relatively very long so no need to
worry or anticipate will run out of its source. The
bearers of non-nuclear energy does not include nuclear power as part of
sustainable energy as supplies of uranium-235 in nature there is a limit, say
hundreds of years. However,
nuclear activists have argued that nuclear energy, including sustainable if it
is used as fuel in fast breeder reactor (FBR: Fast Breeder Reactor) nuclear
fuel because the backup could "give birth" hundreds to thousands of
times.
The
reason for this, reserves discussed nuclear energy experts in the order of tens
or hundreds of years it is implicitly calculated by assuming reactor used is
ordinary reactor (BWR or PWR type generally), which in fact can only burn the
U-235. On
one side of the U-235 content in nature no more than 0.72% only, the remaining
approximately 99.28% is U-238. Of
uranium U-238 is in a state of combustion "regular" (used as fuel in
reactors usual) can not produce nuclear energy, but when mixed with U-235 and
put together into a breeder reactor, along with consumption / combustion U -235,
U-238 experienced a reaction to the capture of one neutron and transformed into
U-239. Within
minutes the U-239 decays while issuing beta particles and re-transformed into
Np-239. Np-239
also returned while emitting beta particles it decays into Pu-239. Pu-239
is this, which although not available in nature but is formed as a byproduct of
combustion of U-235, has the ability to divide and produce energy as U-235. It
is conceivable if all U-238 numbering thousands of times more than the U-235,
successfully transformed into Pu-239, how an increase in the numbers of nuclear
fuel. Something
similar happens to atoms [thorium-233] that with the arrest of one neutron
reactions transformed into U-233 which has the capability chain reaction
(nuclear reactions).
That
is why certain developed countries are reluctant to leave despite the risk of
radioactive nuclear that receives no light. Fast
breeder reactor such as that possessed by North Korea got the strict
supervision of the IAEA for being able to produce new fuel Pu-239 is
susceptible misused for weapons of mass destruction.
On
the other hand the opponents of nuclear tend to use the term "sustainable
energy" as a synonym of "renewable energy" to exclude nuclear
energy from the energy group discussion [need citation needed].
The main
sources of renewable energy:
1. Geothermal
energy
Geothermal
energy comes from radioactive decay in the center of the Earth, which makes
Earth the heat from the inside, as well as from the heat of the sun that makes
the hot surface of the earth. There are three ways
geothermal utilization:
• For power
plants and used in the form of electricity
• As a heat
source which is utilized directly using a pipe into the earth
• As a heat
pump that pumped directly from the bowels of the earth
 |
| Geothermal energy |
Geothermal
energy is a form of thermal energy or thermal energy generated and stored in
the earth. The
heat energy is energy that determines the temperature of an object. Geothermal
energy comes from the energy of planet formation (20%) and the radioactive
decay of minerals (80%) [1]. Geothermal
gradient, which is defined by the difference in temperature between the earth's
core and the surface, controlling the continuous conduction occurs in the form
of heat energy from the core to the surface of the earth.
Earth's
core temperature reaches more than 5000 ° C. Heat
flows by conduction toward the rocks around the Earth's core. This
heat causes the rocks to melt, forming magma. Magma
flow of heat by convection and moving up because of magma in the form of molten
rock has a lower density than solid rock. Earth's
crust and the magma heats the water flowing in the earth's crust, heating it up
to 300 oC. This
raises a hot water high pressure so that water comes out of the earth's crust
[2].
Geothermal energy from the core of the Earth is closer to the surface in some areas. Hot steam or water can be used underground, brought to the surface, and can be used to generate electricity. Geothermal power sources are in some parts of the geologically unstable as Iceland, New Zealand, United States, Philippines, and Italy. The two most prominent areas for this in the United States are in the Yellowstone dome and in northern California. Iceland produces geothermal power and energy flow to 66% of all houses in Iceland in 2000, in the form of direct thermal energy and electrical energy through power generation. 86% of existing homes in Iceland utilizing geothermal home heating.
2. Solar energy
Geothermal energy from the core of the Earth is closer to the surface in some areas. Hot steam or water can be used underground, brought to the surface, and can be used to generate electricity. Geothermal power sources are in some parts of the geologically unstable as Iceland, New Zealand, United States, Philippines, and Italy. The two most prominent areas for this in the United States are in the Yellowstone dome and in northern California. Iceland produces geothermal power and energy flow to 66% of all houses in Iceland in 2000, in the form of direct thermal energy and electrical energy through power generation. 86% of existing homes in Iceland utilizing geothermal home heating.
2. Solar energy
Solar
panels (photovoltaic arrays) on a small yacht at sea can charge the battery of
12 V to 9 ampere under conditions of full and direct sunlight.
 |
| Solar energy |
Since
most renewable energy comes from is "solar energy" term is a bit
confusing. But
the question here is collected energy directly from sunlight.
Solar power
can be used for:
• Generating electricity using
solar cells
• Generate electricity Using
solar tower
• Heating the building directly
• Heating the building via heat
pumps
• Reheating food Using a solar
oven.
• Heating of water through
solar-powered water heaters
Of
course, the sun does not provide constant energy to any point on Earth, so its
use is limited. Solar
cells are often used to charge the battery, in the daytime and the power of the
battery is used at night when sunlight is not available.
3. Wind energy
The
temperature difference at two different places produce different air pressure,
resulting in the wind. Wind
is the movement of matter (air) and has been known for a long time were able to
drive the turbine. Wind
turbines used to generate kinetic energy and electrical energy.
 |
| Wind energy |
Available
energy from the wind is a function of wind speed; when
the wind speed increases, the energy output also increased up to the maximum
limit of the energy produced by the turbine is able to. Regions
with stronger winds and constant as offshore and high altitude, usually
preferred to build "wind farms".
4. Water Energy
Water energy
is used because it has mass and is capable of flows. Water has a
density of 800 times that of air. Even
the slow movement of water is able to be converted into other forms of energy. Water
turbine is designed to obtain energy from various types of reservoir, which is
calculated from the amount of water mass, height, until the water velocity. Water energy is used in
the form of:
·
Dam power plant. The largest
is the Three Gorges dam in China.
·
Micro-hydro is built to generate electricity up to a
scale of 100 kilowatts. Commonly
used in remote areas that have many sources of water.
 |
| Water energy |
·
Run-of-the-river built by harnessing the kinetic energy
of the water flow without the need for a large water reservoir.
5. Biomass
Plants
usually use photosynthesis to store solar energy, air, and CO2. Bio-fuels
(biofuels) are fuels derived from biomass - organisms or products of animal
metabolism, such as feces from cows and so on. It also is a
source of renewable energy. Typically
biomass is burned to release the chemical energy stored in it, the exception
when the biofuel is used to fuel the fuel cell (eg, direct methanol fuel cells
and direct ethanol fuel cell).
 |
| Biomass Struktur |
Biomass
can be used directly as fuel or to produce other types of fuel such as
biodiesel, bioethanol or biogas depending on the source. Biomass
in the form of biodiesel, bioethanol, and biogas can be burned in internal
combustion engines or boilers directly with certain conditions.
Biomass into a renewable energy source if the rate decision does not exceed the rate of production, because basically biomass is a material produced by nature in a relatively short time through a variety of biological processes. Various cases of the use of non-renewable biomass has occurred, such as the case of deforestation Roman times, and is now happening, deforestation amazon. Peat is also true that pendefinisiannya biomass as a renewable energy quite biased because the rate of extraction by humans are not comparable with the rate of growth of the peat layer.
Biomass into a renewable energy source if the rate decision does not exceed the rate of production, because basically biomass is a material produced by nature in a relatively short time through a variety of biological processes. Various cases of the use of non-renewable biomass has occurred, such as the case of deforestation Roman times, and is now happening, deforestation amazon. Peat is also true that pendefinisiannya biomass as a renewable energy quite biased because the rate of extraction by humans are not comparable with the rate of growth of the peat layer.
There
are three forms of the use of biomass, which is in solid, liquid, and gas. And
in general there are two methods for producing biomass, ie by growing organisms
and the use of biomass waste materials processing industries result of living
beings.
6. Liquid
biofuel
Liquid
biofuel usually shaped bioalcohol such as methanol, ethanol and biodiesel. Biodiesel
can be used in modern diesel vehicles with little or no modifications and can
be obtained from waste vegetable and animal oils and fats.
 |
| Bio alcohol |
Depending
on the potential of each area, corn, sugar beets, sugar cane, and several types
of grasses cultivated to produce bioethanol. While
biodiesel is produced from crops or crops that contain oil (palm oil, copra,
castor seeds, algae) and has gone through various processes such as
esterification.
7. Solid
biomass
Direct
use is usually in the form of combustible solids, either wood or flammable
plants. Plants
can be grown specifically for combustion or may be used for other purposes,
such as processed in specific industries and waste processing results which can
be used as a fuel is burned.
 |
| sawdust as a alternative energy fuel burned |
Briquetting
biomass also use solid biomass, in which the raw material can be a piece or
pieces of solid biomass raw or through certain processes such as pyrolysis to
increase the percentage of carbon and reduces the water content. Solid biomass
can also be processed by means of gasification to produce gas.
8. Biogas
Various organic materials, biologically by fermentation, or in physico-chemical gasification, can release flammable gases.
Various organic materials, biologically by fermentation, or in physico-chemical gasification, can release flammable gases.
 |
| Biogas cycle process |
Biogas
can easily be produced from a variety of industrial wastes that exist today,
such as paper production, sugar production, livestock manure, and so on. Various
waste streams must be diluted with water and allowed to naturally ferment,
producing methane gas. The
residue of the fermentation activity is fertilizer rich in nitrogen, carbon,
and minerals.
Small-scale
energy sources
- Piezoelectric, an electric charge resulting from the application of mechanical stress on the solid object. This object converts mechanical energy into electrical energy
- Clock automatically (Automatic watch, self-winding watch) is a watch that is driven by the stored mechanical energy, which is obtained from the user's hand movements. Mechanical energy stored in the spring mechanism inside.
- Platform electrokinetic (electrokinetic road ramp) is the method of generating electrical energy by harnessing the kinetic energy of a moving car on a foundation that is installed on the road. A foundation has been installed in the parking lot of the supermarket Sainsbury's in Gloucester, United Kingdom, where the electricity generated is used to drive the cash register.
reference :
http://id.wikipedia.org
http://semestahijau.blog.dompetdhuafa.org/sample-page/energi-terbarukan/
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