Environmental technology refers to applying environmental monitoring, green chemistry, and electronic devices to monitor and conserve natural resources and curb human impacts on the environment. It includes sustainable energy technologies like solar panels, wind turbines, and bioreactors. The core of environmental technologies is sustainable development. Renewable energy sources like solar, wind, hydro, and biomass are discussed as alternatives to fossil fuels that exist perpetually and produce clean energy without emissions. The document provides an overview of various renewable technologies and their applications.

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INTRODUCTION
Environmental technology (envirotech), green technology (Genentech) or clean
technology (cleantech) is the application of one or more of environmental, green
chemistry, environmental monitoring and electronic devices to monitor, model and
conserve the natural environment and resources, and to curb the negative impacts of
human involvement. The term is also used to describe sustainable energy generation
technologies such as photovoltaics, wind turbines, bioreactors, etc. Sustainable
development is the core of environmental technologies. The term environmental
technologies is also used to describe a class of electronic devices that can promote
sustainable management of resources. Of the 52 percent of the country’s population that
lives in rural areas, 22 percent reside in or near forests. A majority of these people rely on
forest resources for their livelihood, making sustainable land and forest management a
critically important challenge for the Philippines. This section presents the major trends
in land and forest resources management in the country over the past five to ten years.
While there has been some increase in forest cover owing to reforestation efforts and
natural regeneration, per capita forest cover in the Philippines is still the lowest in Asia.
Moreover, the remaining primary or intact forests remain under threat.
 The term is also used to describe sustainable energy generation technologies such
as photovoltaic’s, wind turbines, bioreactors, etc. Sustainable development is the
core of environmental technologies.
 Green Energy – “any sustainable energy source that comes from natural
environment.”
 Some Aspects of Renewable Energy
 It exists perpetually and in abundant in the environment
 It is a clean alternative to fossil fuels
 “energy that is derived from natural process that are replenished
constantly”.
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Contribution of Renewable Energy in World Electricity Production:-
Fig-1 Contribution of Renewable Energy in World Electricity Production.
Major Renewable Energy Sources:-
 Solar Energy
 Wind Energy
 Hydro Energy
 Biomass Energy
 Tidal Energy
 Geothermal Energy
 Wave Energy
 Bio-fuel
 Biogas
Fig-2 Major Renewable Energy Sources.
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PRESENT INSTALLED CAPACITY OF RENEWABLE
ENERGY SOURCES IN INDIA:-
The installed capacity in respect of RES is as on 30.06.2012 is based on MNRE email of
dated 12.07.2012 from the Ministry of Renewable Energy where cumulative Grid
interactive power installed capacity has been indicated as 25409.33 MW. Reconciliation
of installed capacity of Hydro capacity resulted in transfer of 135 MW from conventional
to SHP-RES and retrieval of installed capacity of 67.20 from SHP-RES to conventional
Hydro has resulted in net addition of 67.8 MW to SHP under RES. Also 30 MW of
capacity in the nature of Waste Heat Recovery Power Plant at Goa Energy Private
Limited under U&I category of RES. Out of this installed capacity due to wind and small
hydro amounting to 508.67 MW appearing in captive capacity has been deducted to
arrive at installed capacity of utilities in respect of RES.(25409.33-
508.67+67.8+30=24998.46).
Sector MW %age
State Sector 86,881.13 41.51
Central Sector 62,373.63 29.66
Private Sector 60,321.28 28.82
Total 2,09,276.04
Fuel MW %age
Total Thermal 140206.18 66.99
Coal 120,103.38 57.38
Gas 18,903.05 9.03
Oil 1,199.75 0.57
Hydro (Renewable) 39,291.40 18.77
Nuclear 4,780.00 2.28
RES** (MNRE) 24,998.46 11.94
Total 2,09,276.04 100.00
Table-1 Total Installed Capacity in India
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Renewable Energy Source Present Installed Capacity
Wind 10200 MW
Small Hydro 2100 MW
Bagasse 750 MW
Biomass 620 MW
Solar 2 MW
Total RE Installed Capacity – 13672 MW
Table-2 Total Installed Capacity of Renewable Energy in India
SOLAR ENERGY:-
Solar power is by far the Earth's most available energy source, easily capable of
providing many times the total current energy demand. Solar power is the conversion of
sunlight into electricity.
Two main commercial ways of conversion of sunlight into electricity.
 Concentrating Solar Thermal Plant (CSP)
 Photovoltaic Plants (PV)
CSP and PV both have their markets. PV is very successful in decentralized applications,
whereas CSP offers advantages for central and large-scale applications. CSP power plants
are the most cost-efficient way to generate and to store dispatch able CO2
-free electricity.
However, there is no competition between both. Rather, they have to be seen as
complementary technologies.
PLF of CSP – In the range of 20 % to 30 %
PLF of PV – In the range of 15 % to 20 %
Photovoltaic systems (PV system) use solar panels to convert sunlight into electricity. A
system is made up of one or more solar photovoltaic (PV) panels, an AC/DC power
converter (also known as an inverter), a racking system that holds the solar panels, and
the interconnections and mounting for the other components. A small PV system may
provide energy to a single consumer, or to an isolated device like a lamp or a weather
instrument. Large grid-connected PV systems can provide the energy needed by many
customers. Solar cells can be electrically connected in series or in parallel to give any
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desired voltage and current output. Photovoltaic cells are typically sold in modules (or
panels) of 12 volts with power outputs of 50 to 100+ watts. These are then combined into
arrays to give the desired power or watts.
Fig-3 PV Cells
FUNCTIONING OF PV CELLS:-
PV functionality relies upon the absorption of light within a bulk or semiconductor
material, most commonly a silicon pn diode, providing a medium in which incident
photons can be converted to energy, usually in the form of heat. When absorbed, a photon
transfers energy to an electron in the absorbing material and if the magnitude of incident
photon energy is greater than the electron’s work function, the photon may raise an
electron’s energy state or even liberate an electron. Once liberated, the electrons are then
free to move around the semiconductor material influenced by present phenomena of
diffusion, temperature, and electric field. The quantum theory of semiconductor devices
states that all semiconductors have a gap between their valence and conduction bands.
The valence band represents all allowable energies of valence electrons that are bound
covalently to neighboring host atoms, and the conductive band represents all allowable
energies of electrons which have received some form of energy and are no longer bound
to host atoms. Semiconductors, characterized as being perfect insulators at absolute zero,
become increasingly conductive as temperature is increased. As temperature becomes
greater, sufficient energy is transferred to a small fraction of electrons, causing them to
move from the valence band to the conduction band and holes to move from the
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conduction band to the valence band. The increase in temperature responsible for this
entire process is a direct result of external energy; in the case of PV systems, it is incident
photons due to illumination. Under the photoelectric effect, because photons incident
upon a pn diode can create electron-hole pairs at a cross material junction, an electric
potential difference across this junction can be established. Under no illumination,
electrons and holes are separated at n and p regions respectively due to the diode
characteristic unidirectional current path. When illuminated, PV cells are impacted by
incident photons which bombard cell electrons creating electron hole pairs. These
electron hole pairs then separate in response to the electric field created by the cell
junction, causing electrons to drift back into the n region, and holes into the p region. A
bidirectional current path is created and energy can be harnessed. With basic PV function
understood, a solar cell can now be designed.
Fig-3 Function of PV Cell
WIND ENERGY:-
Wind power is the conversion of wind energy into a useful form of energy, such as
using: wind turbines to make electrical power, windmills for mechanical power, wind
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pumps for water pumping or drainage, or sails to propel ships. A large wind farm may
consist of several hundred individual wind turbines which are connected to the electric
power transmission network. Offshore wind farms can harness more frequent and
powerful winds than are available to land-based installations and have less visual impact
on the landscape but construction costs are considerably higher. Small onshore wind
facilities are used to provide electricity to isolated locations and utility companies
increasingly buy surplus electricity produced by small domestic wind turbines Wind
power, as an alternative to fossil fuels, is plentiful, renewable, widely distributed, clean,
produces no greenhouse gas emissions during operation and uses little land. Any effects
on the environment are generally less problematic than those from other power sources.
As of 2011, Denmark is generating more than a quarter of its electricity, and 83 countries
around the world are using wind power on a commercial basis. In 2010 wind energy
production was over 2.5% of total worldwide electricity usage, and growing rapidly at
more than 25% per annum. The monetary cost per unit of energy produced is similar to
the cost for new coal and natural gas installations. Although wind power is a popular
form of energy generation, the construction of wind farms is not universally welcomed
due to aesthetics. Wind power is very consistent from year to year but has significant
variation over shorter time scales. The intermittency of wind seldom creates problems
when used to supply up to 20% of total electricity demand, but as the proportion
increases, a need to upgrade the grid, and a lowered ability to supplant conventional
production can occur. Power management techniques such as having excess capacity
storage, dispatch able backing supplies (usually natural gas), storage such as pumped-
storage hydroelectricity, exporting and importing power to neighbouring areas or
reducing demand when wind production is low, can greatly mitigate these problems.
 Differential heating of the earth’s surface and atmosphere induces vertical and
horizontal air currents that are affected by the earth’s rotation and contours of the
land and generates WIND. A wind turbine obtains its power input by converting
the force of the wind into a torque (turning force) acting on the rotor blades. The
amount of energy which the wind transfers to the rotor depends on the density of
the air, the rotor area, and the wind speed. PLF of Wind Farm is normally in the
range of 20 % to 30% depending upon the site conditions and WTG rating.
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Fig-4 Wind Turbine.
Hydro Energy :-
Hydro power plants are based on a rather simple concept Hydro power plants harnes
water's energy and use simple mechanics to convert that energy into electricity. Water
flowing through a dam turns a turbine which turns a generator. Hydroelectricity is the
term referring to electricity generated by hydropower; the production of electrical power
through the use of the gravitational force of falling or flowing water. It is the most widely
used form of renewable energy, accounting for 16 percent of global electricity
consumption, and 3,427 terawatt-hours of electricity production in 2010, which continues
the rapid rate of increase experienced between 2003 and 2009.
Hydropower is produced in 150 countries, with the Asia-Pacific region generating 32
percent of global hydropower in 2010. China is the largest hydroelectricity producer, with
721 terawatt-hours of production in 2010, representing around 17 percent of domestic
electricity use. There are now three hydroelectricity plants larger than 10 GW: the Three
Gorges Dam in China, Itaipu Dam in Brazil, and Guri Dam in Venezuela.
The cost of hydroelectricity is relatively low, making it a competitive source of
renewable electricity. The average cost of electricity from a hydro plant larger than 10
megawatts is 3 to 5 U.S. cents per kilowatt-hour.[1]
Hydro is also a flexible source of
electricity since plants can be ramped up and down very quickly to adapt to changing
energy demands. However, damming interrupts the flow of rivers and can harm local
ecosystems, and building large dams and reservoirs often involves displacing people and
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wildlife.[1]
Once a hydroelectric complex is constructed, the project produces no direct
waste, and has a considerably lower output level of the greenhouse gas carbon
dioxide (CO2) than fossil fuel powered energy plants.
 Dam - Most hydropower plants rely on a dam that holds back water, creating a
large reservoir. Often, this reservoir is used as a recreational lake
 Intake - Gates on the dam open and gravity pulls the water through the penstock,
a pipeline that leads to the turbine. Water builds up pressure as it flows through
this pipe
 Turbine - The water strikes and turns the large blades of a turbine, which is
attached to a generator above it by way of a shaft. The most common type of
turbine for hydropower plants is the Francis Turbine, which looks like a big disc
with curved blades. A turbine can weigh as much as 172 tons and turn at a rate of
90 revolutions per minute (rpm)
 Generators - As the turbine blades turn, so do a series of magnets inside the
generator. Giant magnets rotate past copper coils, producing alternating current
(AC) by moving electrons.
 Transformer - The transformer inside the powerhouse takes the AC and
converts it to higher-voltage current
 Power lines - Out of every power plant come four wires: the three phases of
power being produced simultaneously plus a neutral or ground common to all
three
 Outflow - Used water is carried through pipelines, called tailraces, and re-enters
the river downstream
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Fig-5 Hydro Energy
BIOMASS ENERGY:-
Biomass is a renewable energy source that is derived from living or recently living
organisms. Biomass includes biological material, not organic material like coal. Energy
derived from biomass is mostly used to generate electricity or to produce heat. Thermal
energy is extracted by means of combustion, torrefaction, pyrolysis, and gasification.
Biomass can be chemically and biochemically treated to convert it to a energy-rich fuel.
Biomass, as a renewable energy source, is biological material from living, or recently
living organisms. As an energy source, biomass can either be used directly, or converted
into other energy products such as biofuel. In the first sense, biomass is plant matter used
to generate electricity with steam turbines & gasifiers or produce heat, usually by direct
combustion. Examples include forest residues (such as dead trees, branches and tree
stumps), yard clippings, wood chips and even municipal solid waste. In the second sense,
biomass includes plant or animal matter that can be converted into fibers or other
industrial chemicals, including biofuels. Industrial biomass can be grown from numerous
types of plants,
including miscanthus, switchgrass, hemp, corn, poplar, willow, sorghum, sugarcane, bam
boo, and a variety of tree species, ranging from eucalyptus to oil palm (palm oil).
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Fig-6 Sources of Biomass
BIOGAS ENERGY:-
Biogas is clean environment friendly fuel that can be obtained by anaerobic digestion of
animal residues and domestic and farm wastes, abundantly available in the countryside.
Biogas is an important renewable energy resource for rural areas in India Biogas
generally comprise of 55-65 % methane, 35-45 % carbon dioxide, 0.5-1.0 % hydrogen
sulfide and traces of water vapor. Average calorific value of biogas is 20 MJ/m3
(4713
kcal/m3
). Biogas like Liquefied Petroleum Gas (LPG) cannot be liquefied under normal
temperature and pressure. Critical temperature required for liquefaction of methane is
-82.1o
C at 4.71MPa pressure, therefore use of biogas is limited nearby the biogas plant.
An estimate indicates that India has a potential of generating 6.38 X 1010
m3
of biogas
from 980 million tones of cattle dung produced annually. The heat value of this gas
amounts to 1.3 X 1012
MJ. In addition, 350 million tones of manure would also produce
along with biogas.
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Table-3 Biogas Production From Different Material
CONCLUSION:-
Environmental Technology (envirotech), green technology (greentech) or clean
technology (cleantech) is the application of one or more of environmental science, green
chemistry, environmental monitorin and electronic devices to monitor, model and
conserve the natural environment and resources, and to curb the negative impacts of
human involvement. The term is also used to describe sustainable energy generation
technologies such as photovoltaics, wind turbines, bioreactors, etc. Sustainable
development is the core of environmental technologies. The term environmental
technologies is also used to describe a class of electronic devices that can promote
sustainable management of resources.
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REFERENCES:
 Environmental and Renewable Energy Innovation Potential among the States:
State Rankings. Applied Research Project. Texas State University.
http://ecommons.txstate.edu/arp/291/
 Hermann Scheer “Energy Autonomy: The Economic, Social & Technological
Case for Renewable Energy”
 Mark Diesendorf “Greenhouse Solutions with Sustainable Energy”.
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