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OCEAN THERMAL ENERGY

SOURCE:- YOUTUBE.COM

Tidal energy,

sometimes called tidal power, is the power achieved by capturing the energy contained in moving water in tides and open ocean currents.
There are two types of energy systems that can be used to extracted energy: kinetic energy, the moving water of rivers, tides and open ocean currents; and potential energy from the difference in height (or head) between high and low tides. The first method - generating energy from tidal currents - is becoming more and more popular because people believe that it does not harm the environment as much as barrages or dams. Many coastal sites worldwide are being examined for their suitability to produce tidal (current) energy.

Tidal power is classified as a renewable energy source, because tides are caused by the orbital mechanics of the solar system (ocean currents are caused by the surface effect of winds) and are considered inexhaustible. The root source of the energy is the orbital kinetic energy of the earth-moon system, and also the earth-sun system. Tidal power has great potential for future power and electricity generation because of the essentially inexhaustible amount of energy contained in these rotational systems. Tidal power is reliably predictable (unlike wind power and solar power). In Europe, Tide Mills have been used for nearly 1,000 years, mainly for grinding grains.

Wave Energy

Waves are generated by the wind as it blows across the sea surface. Energy is transferred from the wind to the waves.
Wave energy is sometimes confused with tidal energy, which is quite different.
Waves travel vast distances across oceans at great speed. The longer and stronger the wind blows over the sea surface, the higher, longer, faster and more powerful the sea is. The energy within a wave is proportional to the square of the wave height, so a two-meter high wave has four times the power of a one-meter high wave.

Why Wave Energy?
Wave energy has the potential to be one of the most environmentally benign forms of electricity generation. It is a clean and renewable energy source and its potential is huge. Some additional benefits of wave energy are:

1.  With the wave energy resource distributed across the globe, wave energy offers many countries the benefit of security of supply
2.  Waves are generated over large areas of ocean and, once generated, travel immense distances with only small energy losses.
3.  Waves can be anticipated one or two days in advance through direct satellite measurements and meteorological forecasts which provide a high level of predictability and hence good network planning.

SOURCE:- Wikipedia.org , pelamiswave.com

nuclear energy...................

An absorption or release of nuclear energy occurs in nuclear reactions or radioactive decay; those that absorb energy are called endothermic reactions and those that release energy are exothermic reactions. Energy is consumed or liberated because of differences in the nuclear binding energy between the incoming and outgoing products of the nuclear transmutation.
The best-known classes of exothermic nuclear transmutations are fission and fusion. Nuclear energy may be liberated by atomic fission, when heavy atomic nuclei (like uranium and plutonium) are broken apart into lighter nuclei. The energy from fission is used to generate electric power in hundreds of locations worldwide. Nuclear energy is also released during atomic fusion, when light nuclei like hydrogen are combined to form heavier nuclei such as helium. The Sun and other stars use nuclear fusion to generate thermal energy which is later radiated from the surface, a type of stellar nucleosynthesis. In any exothermic nuclear process, nuclear mass might ultimately be converted to thermal energy, given off as heat, carries away the mass with it.
In order to quantify the energy released or absorbed in any nuclear transmutation, one must know the nuclear binding energies of the nuclear components involved in the transmutation.
 types of nuclear energy.........

Nuclear fusion

The binding energy of helium is the energy source of the Sun and of most stars. The sun is composed of 74 percent hydrogen (measured by mass), an element whose nucleus is a single proton. Energy is released in the sun when 4 protons combine into a helium nucleus, a process in which two of them are also converted to neutrons.
The conversion of protons to neutrons is the result of another nuclear force, known as the weak (nuclear) force. The weak force, like the strong force, has a short range, but is much weaker than the strong force. The weak force tries to make the number of neutrons and protons into the most energetically stable configuration. For nuclei containing less than 40 particles, these numbers are usually about equal. Protons and neutrons are closely related and are sometimes collectively known as nucleons. As the number of particles increases toward a maximum of about 209, the number of neutrons to maintain stability begins to outstrip the number of protons, until the ratio of neutrons to protons is about three to two.
The protons of hydrogen combine to helium only if they have enough velocity to overcome each other's mutual repulsion sufficiently to get within range of the strong nuclear attraction. This means that fusion only occurs within a very hot gas. Hydrogen hot enough for combining to helium requires an enormous pressure to keep it confined, but suitable conditions exist in the central regions of the Sun, where such pressure is provided by the enormous weight of the layers above the core, pressed inwards by the Sun's strong gravity. The process of combining protons to form helium is an example of nuclear fusion.
The earth's oceans contain a large amount of hydrogen that could theoretically be used for fusion, and helium byproduct of fusion does not harm the environment, so some consider nuclear fusion a good alternative to supply humanities energy needs. Experiments to generate electricity from fusion have so far have only partially succeeded. Sufficiently hot hydrogen must be ionized and confined. One technique is to use very strong magnetic fields, because charged particles (like those trapped in the Earth's radiation belt) are guided by magnetic field lines. Fusion experiments also rely on heavy hydrogen, which fuses more easily, and gas densities can be moderate. But even with these techniques far more net energy is consumed by the fusion experiments than is yielded by the process.

nuclear fission

nuclear fission is either a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller parts (lighter nuclei). The fission process often produces free neutrons and photons (in the form of gamma rays), and releases a very large amount of energy even by the energetic standards of radioactive decay.
Nuclear fission of heavy elements was discovered in 1938 by Lise Meitner, Otto Hahn, Fritz Strassmann, and Otto Robert Frisch. It was named by analogy with biological fission of living cells. It is an exothermic reaction which can release large amounts of energy both as electromagnetic radiation and as kinetic energy of the fragments (heating the bulk material where fission takes place). In order for fission to produce energy, the total binding energy of the resulting elements must be greater than that of the starting element.
Fission is a form of nuclear transmutation because the resulting fragments are not the same element as the original atom. The two nuclei produced are most often of comparable but slightly different sizes, typically with a mass ratio of products of about 3 to 2, for common fissile isotopes. Most fissions are binary fissions (producing two charged fragments), but occasionally (2 to 4 times per 1000 events), three positively charged fragments are produced, in a ternary fission. The smallest of these fragments in ternary processes ranges in size from a proton to an argon nucleus.

An induced fission reaction. A neutron is absorbed by a uranium-235 nucleus, turning it briefly into an excited uranium-236 nucleus, with the excitation energy provided by the kinetic energy of the neutron plus the forces that bind the neutron. The uranium-236, in turn, splits into fast-moving lighter elements (fission products) and releases three free neutrons. At the same time, one or more "prompt gamma rays" (not shown) are produced, as well.



source:wikipedia.org  ,  youtube.com

geothermal energy...................

Geothermal energy is thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. The geothermal energy of the Earth's crust originates from the original formation of the planet (20%) and from radioactive decay of minerals (80%). 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 γη (ge), meaning earth, and θερμος (thermos), meaning hot.
At the core of the Earth, thermal energy is created by radioactive decay^[1] and temperatures may reach over 5000 °C (9,000 °F). Heat conducts from the core to surrounding cooler rock. The high temperature and pressure cause some rock to melt, creating magma convection upward since it is lighter than the solid rock. The magma heats rock and water in the crust, sometimes up to 370 °C (700 °F).
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. Worldwide, 11,400 megawatts (MW) of geothermal power is online in 24 countries in 2012. An additional 28 gigawatts of direct geothermal heating capacity is installed for district heating, space heating, spas, industrial processes, desalination and agricultural applications in 2010.
Geothermal power is cost effective, reliable, sustainable, and environmentally friendly, 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 Earth's geothermal resources are theoretically more than adequate to supply humanity's energy needs, but only a very small fraction may be profitably exploited. Drilling and exploration for deep resources is very expensive. Forecasts for the future of geothermal power depend on assumptions about technology, energy prices, subsidies, and interest rates. Pilot programs like EWEB's customer opt in Green Power Program show that customers would be willing to pay a little more for a renewable energy source like geothermal. But as a result of government assisted research and industry experience, the cost of generating geothermal power has decreased by 25% over the past two decades. In 2001, geothermal energy cost between two and ten US cents per kWh.

source:wikipedia.org

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, windpumps for water pumping or drainage, or sails to propel ships.

Large wind farms consist of hundreds of individual wind turbines which are connected to the electric power transmission network. Offshore wind is steadier and stronger than on land, and offshore farms have less visual impact, but construction and maintenance costs are considerably higher. Small onshore wind farms provide electricity to isolated locations. 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. The 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 from wind 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.

biogas plant.................

Anaerobic digestion is a collection of processes by which microorganisms break down biodegradable material in the absence of oxygen. The process is used for industrial or domestic purposes to manage waste and/or to produce fuels. Much of the fermentation used industrially to produce food and drink products, as well as home fermentation, uses anaerobic digestion. Silage is produced by anaerobic digestion.

The digestion process begins with bacterial hydrolysis of the input materials. Insoluble organic polymers, such as carbohydrates, are broken down to soluble derivatives that become available for other bacteria. Acidogenic bacteria then convert the sugars and amino acids into carbon dioxide, hydrogen, ammonia, and organic acids. These bacteria convert these resulting organic acids into acetic acid, along with additional ammonia, hydrogen, and carbon dioxide. Finally, methanogens convert these products to methane and carbon dioxide.The methanogenic archaea populations play an indispensable role in anaerobic wastewater treatments.

It is used as part of the process to treat biodegradable waste and sewage sludge. As part of an integrated waste management system, anaerobic digestion reduces the emission of landfill gas into the atmosphere. Anaerobic digesters can also be fed with purpose-grown energy crops, such as maize.

Anaerobic digestion is widely used as a source of renewable energy. The process produces a biogas, consisting of methane, carbon dioxide and traces of other ‘contaminant’ gases. This biogas can be used directly as fuel, in combined heat and power gas engines[5] or upgraded to natural gas-quality biomethane. The nutrient-rich digestate also produced can be used as fertilizer.

hydroelectric power plant........

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 generation – 3,427 terawatt-hours of electricity production in 2010,and is expected to increase about 3.1% each year for the next 25 years.
he cost of hydroelectricity is relatively low, making it a competitive source of renewable electricity.
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 wildlife.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.

 

 

The Gordon Dam in Tasmania is a large hydro facility, with an installed capacity of 430 MW.

Generating methods

Conventional (dams)

Pumped-storage

Run-of-the-river

Tide

Underground

  

Conventional (dams) :

Most hydroelectric power comes from the potential energy of dammed water driving a water turbine and generator. The power extracted from the water depends on the volume and on the difference in height between the source and the water's outflow. This height difference is called the head. The amount of potential energy in water is proportional to the head. A large pipe (the "penstock") delivers water to the turbine.

Pumped-storage : 

This method produces electricity to supply high peak demands by moving water between reservoirs at different elevations. At times of low electrical demand, excess generation capacity is used to pump water into the higher reservoir. When there is higher demand, water is released back into the lower reservoir through a turbine. Pumped-storage schemes currently provide the most commercially important means of large-scale grid energy storage and improve the daily capacity factor of the generation system. Pumped storage is not an energy source, and appears as a negative number in listings.

Run-of-the-river:

 Run-of-the-river hydroelectric stations are those with small or no reservoir capacity, so that the water coming from upstream must be used for generation at that moment, or must be allowed to bypass the dam. In the United States, run of the river hydropower could potentially provide 60,000 MW (about 13.7% of total use in 2011 if continuously available)

Tide:

A tidal power plant makes use of the daily rise and fall of ocean water due to tides; such sources are highly predictable, and if conditions permit construction of reservoirs, can also be dispatchable to generate power during high demand periods. Less common types of hydro schemes use water's kinetic energy or undammed sources such as undershot waterwheels. Tidal power is viable in a relatively small number of locations around the world. In Great Britain, there are eight sites that could be developed, which have the potential to generate 20% of the electricity used in 2012 .                      

Underground:

 An underground power station makes use of a large natural height difference between two waterways, such as a waterfall or mountain lake. An underground tunnel is constructed to take water from the high reservoir to the generating hall built in an underground cavern near the lowest point of the water tunnel and a horizontal tailrace taking water away to the lower outlet waterway.

 

 

Advantages:

1 .  Flexibility:Hydro is a flexible source of electricity since plants can be ramped up and down very quickly to adapt to changing energy demands.

2 . Low power costs:The major advantage of hydroelectricity is elimination of the cost of fuel. The cost of operating a hydroelectric plant is nearly immune to increases in the cost of fossil fuels such as oil, natural gas or coal, and no imports are needed.

3 . Reduced CO2 emissions: Since hydroelectric dams do not burn fossil fuels, they are claimed to not directly produce carbon dioxide. While some carbon dioxide is produced during manufacture and construction of the project, this is a tiny fraction of the operating emissions of equivalent fossil-fuel electricity generation. 

Disadvantages:

 

1. Ecosystem damage and loss of land:

                                         Hydroelectric power stations that use dams would submerge large areas of land due to the requirement of a reservoir.

 

 

:Large reservoirs required for the operation of hydroelectric power stations result in submersion of extensive areas upstream of the dams, destroying biologically rich and productive lowland and riverine valley forests, marshland and grasslands. The loss of land is often exacerbated by habitat fragmentation of surrounding areas caused by the reservoir

2. Methane emissions (from reservoirs):
Lower positive impacts are found in the tropical regions, as it has been noted that the reservoirs of power plants in tropical regions produce substantial amounts of methane. This is due to plant material in flooded areas decaying in an anaerobic environment, and forming methane, a greenhouse gas

3. Failure risks:Because large conventional dammed-hydro facilities hold back large volumes of water, a failure due to poor construction, natural disasters or sabotage can be catastrophic to downriver settlements and infrastructure. Dam failures have been some of the largest man-made disasters in history.

 

 

SOLAR COOKER AND SOLAR CELL

                                  

                    solar cooker

It is a device which converts solar energy directly into heat energy.

diagram-

                         

MATERIAL REQUIRED

 

-A solar cooker cover is lined with reflective material like mirror to reflect sun radiations into the box,where food containing utensil is placed.

-Glass cover(see the img.) is used to trap sun radiations.Glass sheets have a property that they allow radiations of small wavelengths to pass through them but do not allow radiations of large wavelengths to pass through them.

-Insulated lining such as black coloured thermocol is kept under containers to absorb sun radiations.

-The box is coloured black from inside to absorb the heat.

PROCESS

When sun radiations of small wavelengths come towards mirror, the mirror reflects them.Radiations fall on glass cover and pass into the box.The thermocol absorbs the heat of these radiations.When the sun radiations reflect back from here they are of large wavelengths, that is why glass does not allow these to pass  away and the radiations get trapped in the container.So in this way heat is used to cook the food.

ADVANTAGES

-Free of cost

-Pollution free

-no lose of nutrients of the food because of low temperature.

-More than one food item can be cooked.

DISADVANTAGES

-Solar cookers don't work at night or on cloudy days.

 -Parabolic cookers can get dangerously hot. You need to wear sunglasses when looking into a solar cooker, since the sun's reflected rays can hurt your eyes. 

-Food takes a long time to cook in solar box cookers.

                                                           SOLAR CELL

A device which converts solar energy directly into electricity.

diagram-

                          

ADVANTAGES

-It has long life.

-Pollution free

-Requires low maintenance as it has no moving parts.

-Good choice for remote areas.

DISADVANTAGES

-Costly because a highly purified silicon is used as semiconductor to convert infra red waves into electricity.

-Solar cells are connected by using silver wires ,which is very costly,to reduce loss of energy due to

   resistance.

-Used for charging storage batteries,which give direct current.This d.c. can be converted into A.C. through inverter.

DIFF B/W VOLUNTARY AND INVOLUNTARY ACTIONS

It's easier to describe involuntary actions first. Basically, involuntary actions keep you alive and keep you safe. They are things which happen without you even thinking about them. These include behaviours like breathing, blinking, yawning, hiccoughs, and so on, or things like jerking your hand out of a fire, shivering when you're cold, or ducking when someone throws a ball at your face.

Voluntary actions are virtually everything else. Even walking is voluntary. You don't have to think about it when you do it, but it generally doesn't happen until you decide to do it.

Now, here's where the confusing part comes in. Many involuntary actions can become voluntary if you so choose. You can control your breathing or blinking, you can jerk your hand away, or you can duck. However, it's extremely difficult to shiver without being cold or to make yourself yawn or hiccough.

Similarly, you don't have to think about walking. That is, you don't have to think how to do it, but you're not doing it involuntarily. You're doing it subconsciously.

I hope this helps you to understand the difference. It's a fascinating topic.