NON CONVENTIONAL SOURCES OF ENERGY

Conventional energy

 

Energy that has been used from ancient times is known as conventional energy; Coal, natural gases, oil, and firewood are example conventional energy sources. Conventional energy sources have demonstrated both extremely positive and negative consequences. These negative effect have fueled the proliferation of alternative energy sources in recent years. These traditional energy sources consist primarily of coal, natural gas and oil. They form from decaying plant and animal material over hundreds of thousands to millions of years.

They are exhaust able except water. They cause pollution when used, as they emit smoke and ash. They are very expensive to be maintained, stored and transmitted as they are carried over long distance through transmission grid and lines.

Non conventional energy

 

Non conventional energy is a synonymous terms used for the alternative energy or the renewable energy. In a broader sense the clean energy like solar, geothermal, water, wind, biomass, fuels, electricity etc. are taken as the non conventional energy.

 

Non conventional/ renewable energy sources are those energy sources which are not destroyed when their energy is harnessed. Renewable energy sources are distinct from fossil fuels, which must be consumed to release energy.

 

Human use of renewable energy requires technologies that harness natural phenomena, such as sunlight, wind, wave, water flow, biological process such as anaerobic digestion, biological hydrogen production, and geothermal heat.

They are inexhaustible. They are generally pollution free. Less expensive due to local use and easy to maintain.

1. Wind Energy:

Wind is caused by huge convection currents in the Earth's atmosphere, driven by heat energy from the Sun. This means as long as the sun shines, there will be wind.


The earth's surface has both land and water. When the sun comes up, the air over the land heats up quicker than that over water. The heated air is lighter and it rises. The cooler air is denser and it falls and replaced the air over the land. In the night the reverse happens. Air over the water is warmer and rises, and is replaced by cooler air from land.

Wind power is harnessed by setting up a windmill which is used for pumping water, grinding grain and generating electricity. The moving air (wind) has huge amounts of kinetic energy, and this can be transferred into electrical energy using wind turbines. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity. The electricity is sent through transmission and distribution lines to a substation, then on to homes, business and schools.

Wind turbines cannot work if there is no wind,
or if the wind speed is so high it would damage them. Areas with constantly high speed preferably above 20 km per hour are well-suited for harnessing wind energy.
Wind turbines are usually sited on high hills and mountain ridges to take advantage of the prevailing winds.

The gross wind power potential of India is estimated to be about 20,000 MW.

2. Tidal Energy:

Sea water keeps on rising and falling alternatively twice a day under the influence of gravitational pull of moon and sun. This phenomenon is known as tides.

The moving water has huge amounts of kinetic energy, and this can be transferred into useful energy in different ways. Hydroelectric power (HEP) schemes store water high up in dams. The water has gravitational potential energy which is released when it falls.

The Dam is built to retain the water. More electricity is produced if the water is more in the reservoir. Sluice Gates: These can open and close to regulate the amount of water that is released into the pipes. Potential energy in the retained water is transferred into kinetic energy by water flowing through the pipes with high speed.

The force and high pressure in the water turns a series of shafts in a generator. Spinning shafts in the generator charges millions of coils and magnets to create electricity, which is regulated by a transformer. This is then transported via cables to homes and factories.

It is estimated that India possesses 8000-9000 MW of tidal energy potential. The Gulf of Kuchchh is best suited for tidal energy.

3. Solar Energy:

Sun is the source of all energy on the earth. It is most abundant, inexhaustible and universal source of energy. AH other sources of energy draw their strength from the sun. India is blessed with plenty of solar energy because most parts of the country receive bright sunshine throughout the year except a brief monsoon period. India has developed technology to use solar energy for cooking, water heating, water dissimilation, space heating, crop drying etc.

4. Geo-Thermal Energy:

Geo-thermal energy is the heat of the earth's interior. This energy is manifested in the hot springs. The most common current way of capturing the geothermal energy is to tap into naturally occurring hydrothermal convection systems containing pressurized hot water or steam. These are forced to the surface and used to drive steam turbine generators, or used to heat hot water or air for space or water heating. India is not very rich in this source,

5. Energy from Biomass:

Biomass refers to all plant material and animal excreta when considered as an energy source. Some important kinds of biomass are inferior wood, urban waste, bagasse, farm animal and human waste.

Advantages of Non-conventional Energy Sources are:

       They are renewable sources of energy.

       They can be renewed with less effort and money.

       Usage of these non-conventional energy sources does not cause pollution and are eco-friendly.

       They are inexhaustible resources.

       There is no depletion of natural resources.

       Does not cause harm to the ecosystem.

       The energy sources are sustainable and will never run out.

       They require less maintenance and reduce the cost of operation.

       The produce very little or no waste products like carbon dioxide and other pollutants and have minimal effect on the environment.

       They can be economically beneficial to many regional areas.

 

Disadvantages of Non-conventional Energy Sources are:

1. available in dilute form in nature
2. cost of harnessing energy is very high
3. availability is uncertain
4. difficulty in transporting such resources

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%). They cause water deep inside the earth to form steam. As more steam is formed, it gets compressed at high pressure and comes out in the form of hot springs which produces geothermal power. 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.

Geothermal power is cost effective, reliable, sustainable, and environmentally friendly,^[7] 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 most common current way of capturing the geothermal energy is to tap into naturally occurring hydrothermal convection systems containing pressurized hot water or steam. These are forced to the surface and used to drive steam turbine generators, or used to heat hot water or air for space or water heating.

 

Geothermal energy – Working principle

First step needed is to extract the geothermal energy from steam, hot water and hot rocks from Earth's crust. The success of this process depends on how hot the water gets, and water temperature depends on how hot were rocks to start with, and how much water is pumped down to these rocks. The water is pumped down through an „injection well“, it passes through the cracks in these rocks and then comes back up again through a „recovery well“ towards the surface, and because of the great pressure water is transformed into a steam when getting to the surface.

This created steam then needs to be separated from brine what is usually done in central separation chamber. After this process of separation is over, complete steam is transferred to heat exchangers which are located inside the power plant. After steam is transferred to heat exchangers it’s possible to transfer it even further to the steam turbines where it can be generated into electricity, and in the same time through the exhaust pipes unused energy is being released.

In heat exchangers steam is being cooled under the pressure in condensate and after that heat is transferred into cold water in condensate heat exchangers. This cold water that is gained on this way gets pumped from wells to storage tanks from which is transferred to heat exchangers where water's temperature gets increased and then passes through deaerators where it boils and where released oxygen and other gases that could cause corrosion (when being heated) are removed by final water cooling.

Advantages of Geothermal Energy

1)  It is a renewable source of energy.
2)  By far, it is non-polluting and environment friendly.
3)  There is no wastage or generation of by-products.
4)  Geothermal energy can be used directly. In ancient times, people used this source of energy for heating homes, cooking, etc.
5)  Maintenance cost of geothermal power plants is very less.
6)  Geothermal power plants don't occupy too much space and thus help in protecting natural environment.
7)  Unlike solar energy, it is not dependent on the weather conditions.

Disadvantages of Geothermal Energy

1)  Only few sites have the potential of Geothermal Energy.
2)  Most of the sites, where geothermal energy is produced, are far from markets or cities, where it needs to be consumed.
3)  Total generation potential of this source is too small.
4)  There is always a danger of eruption of volcano.
5)  Installation cost of steam power plant is very high.
6)  There is no guarantee that the amount of energy which is produced will justify the capital expenditure and operations costs.
7)  It may release some harmful, poisonous gases that can escape through the holes drilled during construction.

Applications of Geothermal Energy

 

1. Aquaculture, Horticulture, And Thermo culture

Geothermal renewable energy can be used for aquaculture, horticulture, and thermoculture. This renewable energy can be used to raise plants and marine life that needs warm waters and a tropical environment. Greenhouses can use geothermal power generation to keep plants warm and moist, with the steam and heat being provided by geothermal energy.

2. Industrial And Agricultural Uses

Geothermal power generation can play a big part in industrial and agricultural operations around the world. Geothermal renewable energy can play many roles in these sectors. Timber can be dried using heat from geothermal energy, and paper mills like one that is located on a geothermal field can use this energy in almost every stage of paper processing.

 

3. Food Processing

The food processing industry is one that can benefit greatly from geothermal renewable energy. One way that this energy source can be invaluable is as steam for sterilizing food processing facilities. Geothermal energy can also help dry out plants, making powders and concentrates that are used in food processing, and at times these substances can be used to add flavors or preserve foods without any unnatural additives. Foods can be cooked, steamed, or prepared in other ways using geothermal energy as well.

4. Providing Heat For Residential And Commercial Use

Geothermal renewable energy can be used to provide heat for all types of buildings, from homes to businesses to farms, barns, and other types of buildings.

5. Electricity Generation

A geothermal power station can provide a large amount of electricity, with many benefits that using fossil fuels for electricity generation do not offer. Geothermal power generation is very clean, because it uses the heat and steam trapped in the earth to produce electricity.

 

 

Nuclear Energy

Nuclear energy is a rare form of energy. It is the energy stored in the center or the nucleus of an atom. Nearly all the mass of the atom is concentrated in a tiny nucleus in the center. The nucleus is composed principally of two sorts of particles: the proton which carries the positive charge and the neutron which is electrically neutral and has a mass slightly bigger than that of proton. Nuclear energy is the energy released from the nucleus of an atom. When nuclear reaction occurs weather fission or fusion, it produces large amount of energy.

After we bombard the nucleus into two parts, two different elements are formed along with the emission of high energy. The process generally followed is called fission. There is another reaction called fusion, which produces almost one tenth of the energy as produced during fission. Fission is the chain reaction which needs uranium-235. The nuclear energy is considered as the worthiest alternative source of energy after fossil fuels.

Nuclear fission is the splitting of a massive nucleus into photons in the form of gamma rays, free neutrons, and other subatomic particles. In a typical nuclear reaction involving ²³⁵U and a neutron:

²³⁵₉₂U + n = ²³⁶₉₂U

followed by

²³⁶₉₂U = ¹⁴⁴₅₆Ba + ⁸⁹ ₃₆Kr + 3n + 177 MeV

The fission of heavy elements is highly exothermic which releases about 200 million eV compared to burning coal which only gives a few eV. The amount of energy released during nuclear fission is millions of times more efficient per mass than that of coal considering only 0.1 percent of the original nuclei is converted to energy. Daughter nucleus, energy, and particles such as neutrons are released as a result of the reaction. The particles released can then react with other radioactive materials which in turn will release daughter nucleus and more particles as a result, and so on. The unique feature of nuclear fission reactions is that they can be harnessed and used in chain reactions. This chain reaction is the basis of nuclear weapons. One of the well known elements used in nuclear fission is Uranium-235. When Uranium-235 is bombarded with a neutron, the atom turns into Uranium-236 which is even more unstable, resulting in the nucleus splitting into daughter nuclei such as Krypton-92 and Barium-141 and free neutrons. The resulting fission products are highly radioactive, commonly undergoing beta-minus decay.  

 

Nuclear fusion is the reaction in which two or more nuclei combine together to form a new element with higher atomic number (more protons in the nucleus). The energy released in fusion is related to E = mc ² (Einstein’s famous energy-mass equation). On earth, the most likely fusion reaction is Deuterium–Tritium reaction. Deuterium and Tritium are both isotopes of hydrogen.

² ₁Deuterium + ³ ₁Tritium = ⁴₂He + ¹₀n + 17.6 MeV

The reaction is followed either by a release or absorption of energy. Fusion of nuclei with lower mass than iron releases energy while fusion of nuclei heavier than iron generally absorbs energy. This phenomenon is known as iron peak. The opposite occurs with nuclear fission.

The power of the energy in a fusion reaction is what drives the energy that is released from the sun and a lot of stars in the universe. Nuclear fusion is also applied in nuclear weapons, specifically, a hydrogen bomb. Nuclear fusion is the energy supplying process that occurs at extremely high temperatures like in stars such as the sun, where smaller nuclei are joined to make a larger nucleus, a process that gives off great amounts of heat and radiation. When uncontrolled, this process can provide almost unlimited sources of energy and an uncontrolled chain provides the basis for a hydrogen bond, since most commonly hydrogen is fused. Also, the combination of deuterium atoms to form helium atoms fuel this thermonuclear process. For example:  ²H   + ³H → ⁴He + ¹n + energy.

 

Comparison chart

	Nuclear Fission	Nuclear Fusion
Definition	Fission is the splitting of a large atom into two or more smaller ones.	Fusion is the fusing of two or more lighter atoms into a larger one.
Natural occurrence of the process	Fission reaction does not normally occur in nature.	Fusion occurs in stars, such as the sun.
Byproducts of the reaction	Fission produces many highly radioactive particles.	Few radioactive particles are produced by fusion reaction, but if a fission "trigger" is used, radioactive particles will result from that.
Conditions	Critical mass of the substance and high-speed neutrons are required.	High density, high temperature environment is required.
Energy Requirement	Takes little energy to split two atoms in a fission reaction.	Extremely high energy is required to bring two or more protons close enough that nuclear forces overcome their electrostatic repulsion.
Energy Released	The energy released by fission is a million times greater than that released in chemical reactions, but lower than the energy released by nuclear fusion.	The energy released by fusion is three to four times greater than the energy released by fission.
Nuclear weapon	One class of nuclear weapon is a fission bomb, also known as an atomic bomb or atom bomb.	One class of nuclear weapon is the hydrogen bomb, which uses a fission reaction to "trigger" a fusion reaction.
Energy production	Fission is used in nuclear power plants.	Fusion is an experimental technology for producing power.
Fuel	Uranium is the primary fuel used in power plants.	Hydrogen isotopes (Deuterium and Tritium) are the primary fuel used in experimental fusion power plants.

 

 

How Nuclear Power Works

Principles of Nuclear Power

Atoms are constructed like miniature solar systems. At the center of the atom is the nucleus; orbiting around it are electrons.

The nucleus is composed of protons and neutrons, very densely packed together. Hydrogen, the lightest element, has one proton; uranium, the heaviest natural element has 92 protons.

The nucleus of an atom is held together with great force, the "strongest force in nature." When it is bombarded with a neutron, it can be split apart, a process called fission (pictured to the right). Because uranium atoms are so large, the atomic force that binds it together is relatively weak, making uranium good for fission.

In nuclear power plants, neutrons collide with uranium atoms, splitting them. This split releases neutrons from the uranium that in turn collide with other atoms, causing a chain reaction. This chain reaction is controlled with "control rods" that absorb neutrons.

Fission releases energy that heats water to about 520 degrees F in the core of nuclear power plants. This hot water is then used to spin turbines that are connected to generators, producing electricity.

What Is A Nuclear Reactor?

All nuclear reactors are devices designed to maintain a chain reaction producing a steady flow of neutrons generated by the fission of heavy nuclei. They are, however, differentiated either by their purpose or by their design features. In terms of purpose, they are either research reactors or power reactors.

Research reactors are operated at universities and research centres in many countries, including some where no nuclear power reactors are operated. These reactors generate neutrons for multiple purposes, including producing radiopharmaceuticals for medical diagnosis and therapy, testing materials and conducting basic research.

Power reactors are usually found in nuclear power plants. Dedicated to generating heat mainly for electricity production, they are operated in more than 30 countries (see Nuclear Power Reactors). Their lesser uses are drinking water or district water production. In the form of smaller units, they also power ships.

Most of the plants in operation are "light water" reactors, meaning they use normal water in the core of the reactor.

In the United States, two-thirds of the reactors are pressurized water reactors (PWR) and the rest are boiling water reactors (BWR). In a boiling water reactor, shown below, the water is allowed to boil into steam, and is then sent through a turbine to produce electricity.



In pressurized water reactors, shown below, the core water is held under pressure and not allowed to boil. The heat is transferred to water outside the core with a heat exchanger (also called a steam generator) the outside water boils into steam and drives a turbine. In pressurized water reactors, the water that is boiled is separate from the fission process, and so does not become radioactive.



After the steam is used to power the turbine, it is cooled off to make it condense back into water. Some plants use water from rivers, lakes or the ocean to cool the steam, while others use tall cooling towers. The hourglass-shaped cooling towers are the familiar landmark of many nuclear plants. For every unit of electricity produced by a nuclear power plant, about two units of waste heat are rejected to the environment.

Advantages of Nuclear Energy

1. Lower Greenhouse Gas Emissions : As per the reports in 1998, it has been calculated the emission of the greenhouse gas has reduced for nearly half due to the popularity in the use of nuclear power. Nuclear energy by far has the lowest impact on the environment since it does not releases any gases like carbon dioxide, methane which are largely responsible for greenhouse effect. There is no adverse effect on water, land or any habitats due to the use of it. Though some greenhouse gases are released while transporting fuel or extracting energy from uranium.

2. Powerful and Efficient : The other main advantage of using nuclear energy is that it is very powerful and efficient than other alternative energy sources. Advancement in technologies has made it more viable option than others. This is one the reason that many countries are putting huge investments in nuclear power. At present, a small portion of world’s electricity comes through it.

3. Reliable : Unlike traditional sources of energy like solar and wind which require sun or wind to produce electricity, nuclear energy can be produced from nuclear power plants even in the cases of rough weather conditions. They can produce power 24/7 and need to be shut down for maintenance purposes only.

4. Cheap Electricity : The cost of uranium which is used as a fuel in generating electricity is quite low. Also, set up costs of nuclear power plants is relatively high while running cost is low. The average life of nuclear reactor range from 4.-60 years depending upon its usage. These factors when combined make the cost of producing electricity very low. Even if the cost of uranium rises, the increase in cost of electricity will be much lower.

5. Low Fuel Cost : The main reason behind the low fuel cost is that it requires little amount of uranium to produce energy. When a nuclear reaction happens, it releases million times more energy as compared to traditional sources of energy.

6. Supply : There are certain economic advantages in setting up nuclear power plants and using nuclear energy in place of conventional energy. It is one of the major sources of electricity throughout the nation. The best part is that this energy has a continuous supply. It is widely available, has huge reserves and expected to last for another 100 years while coal, oil and natural gas are limited and are expected to vanish soon.

7. Easy Transportation : Production of nuclear energy needs very less amount of raw material. This means that only about 28 gram of uranium releases as much energy as produced from 100 metric tons of coal. Since it’s required in small quantities, transportation of fuel is much easier than fossil fuels. Optimal utilization of natural resources in production of energy is a very thoughtful approach for any nation. It not only enhances the socio-economic condition but also sets example for the other countries.

Disadvantages of Nuclear Energy

1. Radioactive Waste : The waste produced by nuclear reactors needs to be disposed off at a safe place since they are extremely hazardous and can leak radiations if not stored properly. Such kind of waste emits radiations from tens to hundreds of years. The storage of radioactive waste has been major bottleneck for the expansion of nuclear programs.

2. Nuclear Accidents : While so many new technologies have been put in place to make sure that such disaster don’t happen again like the ones Chernobyl or more recently Fukushima but the risk associated with them are relatively high. Even small radiation leaks can cause devastating effects. Some of the symptoms include nausea, vomiting, diarrhea and fatigue. People who work at nuclear power plants and live near those areas are at high risk of facing nuclear radiations, if it happens.

3. Nuclear Radiation : There are power reactors called breeders. They produce plutonium. It is an element which is not found in the nature however it is a fissionable element. It is a by-product of the chain reaction and is very harmful if introduced in the nature. It is primarily used to produce nuclear weapons. Most likely, it is named as dirty bomb.

4. High Cost : Another practical disadvantage of using nuclear energy is that it needs a lot of investment to set up a nuclear power station. It is not always possible by the developing countries to afford such a costly source of alternative energy. Nuclear power plants normally take 5-10 years to construct as there are several legal formalities to be completed and mostly it is opposed by the people who live nearby.

5. National Risk : Nuclear energy has given us the power to produce more weapons than to produce things that can make the world a better place to live in. We have to become more careful and responsible while using nuclear energy to avoid any sort of major accidents. They are hot targets for militants and terrorist organizations. Security is a major concern here. A little lax in security can prove to be lethal and brutal for humans and even for this planet.

6. Impact on Aquatic Life : Eutrophication is another result of radioactive wastes. There are many seminars and conferences being held every year to look for a specific solution. But there is no outcome as of now. Reports say that radioactive wastes take almost 10,000 years to get back to the original form.

7. Major Impact on Human Life : We all remember the disaster caused during the Second World War after the nuclear bombs were dropped over Hiroshima and Nagasaki. Even after five decades of the mishap, children are born with defects. This is primarily because of the nuclear effect. Do we have any remedy for this? The answer is still no.

8. Fuel Availability : Unlike fossil fuels which are available to most of the countries, uranium is very scare resource and exist in only few of the countries. Permissions of several international authorities are required before someone can even thought of building a nuclear power plant.

9. Non Renewable : Nuclear energy uses uranium which is a scarce resource and is not found in many countries. Most of the countries rely on other countries for the constant supply of this fuel. It is mined and transported like any other metal. Supply will be available as long as it is there. Once all extracted, nuclear plants will not be of any use. Due to its hazardous effects and limited supply, it cannot be termed as renewable.

Applications

There have been great advances in using nuclear energy for peaceful purposes, such as medicinal use of isotopes, radiation techniques or production of electricity. Other uses are:

Food and Agriculture
The use of isotopes and radiation techniques in agriculture comes under this category. Leading organizations have been working on the technology to increase agricultural production, improve food availability and quality, reduce production costs and minimize pollution of food crops. One major ongoing advancement is Sterile Insect Technique (SIT), that helps in large-scale food irrigation and biological control of pests.

Human Health
One very common application is in the treatment of cancer, i.e., through the use of radiotherapy. Also, small amounts of radioisotope tracers are used for diagnostic and research purposes. The radioisotopes aid in measuring the concentration of various enzymes, some drugs, hormones and many other substances that are present in the human blood. These techniques have also helped in monitoring the levels of toxic substances in food, air and water.

Sterilization
Gamma emissions can be used for the sterilization of medical supplies like cotton, bandages, gloves used for surgery, syringes, burn dressings, etc.

Tracing Pollutants
Radioisotopes can be actively used for tracing the pollutants present in air. The dangerous residues of the radioisotope present even in small amounts in air can be very harmful to humans (can cause health effects such as kidney disease, etc.). Hence, the tracing quality helps to detect the residue easily, thereby ensuring a healthy and safe environment.

Detecting Leaks in Pipelines
The gamma rays emitted by the radioisotopes can now be used to check welds of gas and oil pipelines. In this, the radioactive source is placed inside the pipe and the film outside the welds. This being convenient, can successfully be used in place of X-ray equipment, which was earlier used to detect leakage in pipelines.

Power Sources
While decaying, the radioisotopes emit lots of energy, which is used to control the heart pacemaker. This energy also provides power to the beacons and satellites used for navigation.

Determination of Age
The most interesting use of the nuclear energy is that it can be used by the archaeologists, geologists and anthropologists in determining the age of rocks, insects, etc.

Its Use in Space
Both fission and fusion of nuclear power is actively used in providing power for the missions in space. It generates higher velocities that increases the speed of rockets. This high generation of velocity is due to the higher density reactions that take place and is around 7 magnitudes more than the chemical reactions, which is used to power the current generation of rockets.

Generating Electricity
With so many different uses, the use of nuclear energy for the production of electricity is the most important one. The energy released by the fission that takes place in a nuclear reactor of the nuclear power plant is converted and generated into electricity.

Nuclear energy can also be used in industries for processing of various products by means of radiation.

 

Wind power

Wind power is the conversion of wind energy into a useful form of energy, such as using wind turbines to produce 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. For new constructions, onshore wind is an inexpensive source of electricity, competitive with or in many places cheaper than fossil fuel plants.^[1][2] Offshore wind is steadier and stronger than on land, and offshore farms have less visual impact, but construction and maintenance costs are considerably higher.

 

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.^[4] The effects on the environment are generally less problematic than those from other power sources.

 

Types of wind turbine:

Horizontal axis

Horizontal-axis wind turbines (HAWT) have the main rotor shaft and electrical generator at the top of a tower, and must be pointed into the wind. Small turbines are pointed by a simple wind vane, while large turbines generally use a wind sensor coupled with a servo motor. Most have a gearbox, which turns the slow rotation of the blades into a quicker rotation that is more suitable to drive an electrical generator.^[17]

Since a tower produces turbulence behind it, the turbine is usually positioned upwind of its supporting tower. Turbine blades are made stiff to prevent the blades from being pushed into the tower by high winds. Additionally, the blades are placed a considerable distance in front of the tower and are sometimes tilted forward into the wind a small amount.

Downwind machines have been built, despite the problem of turbulence (mast wake), because they don't need an additional mechanism for keeping them in line with the wind, and because in high winds the blades can be allowed to bend which reduces their swept area and thus their wind resistance. Since cyclical (that is repetitive) turbulence may lead to fatigue failures, most HAWTs are of upwind design.

Vertical axis design

Vertical-axis wind turbines (or VAWTs) have the main rotor shaft arranged vertically. One advantage of this arrangement is that the turbine does not need to be pointed into the wind to be effective, which is an advantage on a site where the wind direction is highly variable, for example when the turbine is integrated into a building. Also, the generator and gearbox can be placed near the ground, using a direct drive from the rotor assembly to the ground-based gearbox, improving accessibility for maintenance.

The key disadvantages include the relatively low rotational speed with the consequential higher torque and hence higher cost of the drive train, the inherently lower power coefficient, the 360 degree rotation of the aerofoil within the wind flow during each cycle and hence the highly dynamic loading on the blade, the pulsating torque generated by some rotor designs on the drive train, and the difficulty of modelling the wind flow accurately and hence the challenges of analysing and designing the rotor prior to fabricating a prototype.^[20]

When a turbine is mounted on a rooftop the building generally redirects wind over the roof and this can double the wind speed at the turbine. If the height of a rooftop mounted turbine tower is approximately 50% of the building height it is near the optimum for maximum wind energy and minimum wind turbulence. Wind speeds within the built environment are generally much lower than at exposed rural sites,^[21][22] noise may be a concern and an existing structure may not adequately resist the additional stress.

Types of controls in wind mill:

• Pitch control - The turbine's electronic controller monitors the turbine's power output. At wind speeds over 45 mph, the power output will be too high, at which point the controller tells the blades to alter their pitch so that they become unaligned with the wind. This slows the blades' rotation. Pitch-controlled systems require the blades' mounting angle (on the rotor) to be adjustable.
• Passive stall control - The blades are mounted to the rotor at a fixed angle but are designed so that the twists in the blades themselves will apply the brakes once the wind becomes too fast. The blades are angled so that winds above a certain speed will cause turbulence on the upwind side of the blade, inducing stall. Simply stated, aerodynamic stall occurs when the blade's angle facing the oncoming wind becomes so steep that it starts to eliminate the force of lift, decreasing the speed of the blades.
• Active stall control - The blades in this type of power-control system are pitchable, like the blades in a pitch-controlled system. An active stall system reads the power output the way a pitch-controlled system does, but instead of pitching the blades out of alignment with the wind, it pitches them to produce stall.

Advantages Of Wind Energy

1. Renewable Energy : Wind energy in itself is a source of renewable energy which means it can be produced again and again since it is available in plenty. It is cleanest form of renewable energy and is currently used many leading developed and developing nations to fulfill their demand for electricity.

2. Reduces Fossil Fuels Consumption : Dependence on the fossil fuels could be reduced to much extent if it is adopted on the much wider scale by all the countries across the globe. It could be answer to the ever increasing demand for petroleum and gas products. Apart from this, it can also help to curb harmful gas emissions which are the major source of global warming.

3. Less Air and Water Pollution : Wind energy doesn’t pollute at all. It is that form of energy that will exist till the time sun exists. It does not destroy the environment or release toxic gases. Wind turbines are mostly found in coastal areas, open plain and gaps in mountains where the wind is reliable, strong and steady. An ideal location would have a near constant flow of non-turbulent wind throughout the year, with a minimum likelihood of sudden powerful bursts of wind.

4. Initial Cost : The cost of producing wind energy has come down steadily over the last few years. The main cost is the installation of wind turbines. Moreover the land used to install wind turbines can also be used for agriculture purpose. Also, when combine with solar power, it provides cheap, reliable, steady and great source of energy for the for developed and developing countries.

5. Create Many Jobs : Wind energy on the other hand has created many jobs for the local people. From installation of wind turbines to maintenance of the area where turbines are located, it has created wide range of opportunities for the people. Since most of the wind turbines are based in coastal and hilly areas, people living there are often seen in maintenance of wind turbines.

Disadvantages Of Wind Energy

1. Noise Disturbances : Though wind energy is non-polluting, the turbines may create a lot of noise. This alone is the reason that wind farms are not built near residential areas. People who live near-by often complaint of huge noise that comes from wind turbines.

2. Threat to Wildlife : Due to large scale construction of wind turbines on remote location, it could be a threat to wild life near by. Few studies have been done by wind turbines to determine the effect of wind turbines on birds and animals and the evidence is clear that animals see wind turbines as a threat to their life. Also, wind turbines require them to be dig deep into the earth which could have negative effect on the underground habitats.

3. Wind Can Never Be Predicted : The main disadvantage of wind energy is that wind can never be predicted. In areas where large amount of wind is needed or winds strength is too low to support wind turbine, there solar or geothermal energy could prove to be great alternatives. That is one of the reasons that most of the companies determine wind turbine layout, power curve, thrust curve, long term wind speed before deploying wind turbines.

4. Suited To Particular Region : Wind turbines are suited to the coastal regions which receive wind throughout the year to generate power. So, countries that do not have any coastal or hilly areas may not be able to take any advantage of wind power. The location of a wind power system is crucial, and one should determine the best possible location for wind turbine in order to capture as much wind as possible.

5. Visual Impact : Though many people believe that wind turbines actually look nice but majority of them disagree. People consider wind turbines to have an undesirable experience. Petitions usually comes in court before any proposed wind farm development but few people think otherwise and feel they should be kept in tact for everyone to enjoy its beauty.

Tidal power

Tidal power, also called tidal energy, is a form of hydropower that converts the energy of tides into useful forms of power, mainly electricity.

Although not yet widely used, tidal power has potential for future electricity generation. Tides are more predictable than wind energy and solar power. Tides are the waves caused due to the gravitational pull of the moon and also sun(though its pull is very low). The rise is called high tide and fall is called low tide. This building up and receding of waves happens twice a day and causes enormous movement of water.

Thus tidal energy forms a large source of energy and can be harnessed in some of the coastal areas of the world. Tidal dams are built near shores for this purpose. During high tide, the water flows into the dam and during low tide, water flows out which result in turning the turbine.

Advantages of Tidal Energy

1)  It is an inexhaustible source of energy.
2)  Tidal energy is environment friendly energy and doesn't produce greenhouse gases.
3)  As 71% of Earth’s surface is covered by water, there is scope to generate this energy on large scale.
4)  We can predict the rise and fall of tides as they follow cyclic fashion.
5) Efficiency of tidal power is far greater as compared to coal, solar or wind energy. Its efficiency is around 80%.
6)  Although cost of construction of tidal power is high but maintenance costs are relatively low.
7)  Tidal Energy doesn’t require any kind of fuel to run.
8)  The life of tidal energy power plant is very long.
9)  The energy density of tidal energy is relatively higher than other renewable energy sources.

Disadvantages of Tidal Energy

1)  Cost of construction of tidal power plant is high.
2)  There are very few ideal locations for construction of plant and they too are localized to coastal regions only.
3)  Intensity of sea waves is unpredictable and there can be damage to power generation units.
4)  Influences aquatic life adversely and can disrupt migration of fish.
5)  The actual generation is for a short period of time. The tides only happen twice a day so electricity can be produced only for that time.
6)  Frozen sea, low or weak tides, straight shorelines, low tidal rise or fall are some of the obstructions.
7)  This technology is still not cost effective and more technological advancements are required to make it commercially viable.
8)  Usually the places where tidal energy is produced are far away from the places where it is consumed. This transmission is expensive and difficult.

Uses:

 

Tidal Electricity - Like other forms of Energy,the main usage of Tidal Energy is in the generation of Electricity.Tidal Energy is being used in France to generate 240 MW of Tidal Electricity at very low costs. Note the Power generated from Tidal Energy is reliable as Tides are uniform and predictable in nature.

Grain Mills – Tidal Energy has been used for hundreds of years.Just like Wind Mills,Tidal Energy was used for the mechanical crushing of grains in Grain Mills.The movement of Turbines due to Tidal Energy was used in the crush Grains.However with the advents of Fossil Fuels,this usage of Tidal Energy has become quite low.

Energy Storage - Tidal Energy can also be used as a store of Energy. Like many of the hydroelectric dams which can be used a large Energy Storage ,so Tidal Barrages with their reservoirs can be modified to store energy. Though this has not been tried out,with suitable modifications Tidal Energy can be stored as well though costs may prove to be high.

Provide Protection to Coast in High Storms – Tidal Barrages can prevent Damage to the Coast during High Storms and also provide an easy transport method between the 2 arms of a Bay or an Estuary on which it is built.

Ocean Wave Energy

Wave energy is an irregular and oscillating low-frequency energy source that can be converted to a 60-Hertz frequency and can then be added to the electric utility grid. The energy in waves comes from the movement of the ocean and the changing heights and speed of the swells. Kinetic energy, the energy of motion, in waves is tremendous. An average 4-foot, 10-second wave striking a coast puts out more than 35,000 horsepower per mile of coast.

Waves get their energy from the wind. Wind comes from solar energy. Waves gather, store, and transmit this energy thousands of miles with little loss. As long as the sun shines, wave energy will never be depleted. It varies in intensity, but it is available twenty-four hours a day, 365 days a year.

Wave energy is the energy of the surface waves of the oceans and this energy can be captured to do useful work such as the production of electricity, pumping off water or power the water desalination plants. Wave energy has great potential which is estimated at around a 2TW worldwide.

Wave Energy Advantages

1. Potential: According to estimations there is a lot of potential from the use of Wave energy. Based on current estimates and efficiency levels of the wave energy converters we can exploit the waves to get about 2TW of energy power so that we can turn it into useful energy like electricity. This means that exploitation of wave energy is still at its infancy.
2. Green: Wave energy is green, meaning that it does not emit any hazardous for the environment polluting gases thus contributing to the reduction of CO₂ emissions and towards the goal for a cleaner environment.
3. Renewable Source: Wave energy is a Renewable Energy Source, RES, with all the benefits such a source would have. It is renewable and as long as we have waves we can capture their energy. Of course waves will exist for as long as we have winds.
4. Consistent Wave Power: Waves are consistent throughout the day and thus electricity production is predictable and overall it can be planed and properly managed. This makes wave energy more consistent than Wind and Solar Energy.
5. Low Operational Costs: Once the Wave Energy Converters, WECs, are installed the wave energy plant has low operational costs which makes such an investment attractive.
6. Minimal aesthetic pollution: Wave energy converters are installed either on the surface of the water or are submerged in the water thus affecting the surrounding as little as possible. Many plants are built offshore thus affecting the aesthetics even less.
7. No pollution danger: There is no danger of polluting the surrounding area in case of a disaster like there is with fossil fuel plants. Quite frequently accidents at oil rigs pollute the surrounding areas this can never be the case with wave energy plants.
8. Shoreline Protection: A positive side effect wave energy plants have is the fact that the capturing of the energy of the waves means that the power with which they hit the shoreline is less, thus causing less damages and less corrosion of the shores.
9. Wave energy plant size: Wave energy plants can be built at various sizes contrary to fossil fuel plants like a nuclear plant. This means that the plants can be built according to needs and based on budget availability.
10. Wave density: The power density of wave energy is greater than wind energy thus making it more efficient.

Wave Energy Disadvantages

1. Cost: Cost is the number one disadvantage of Wave energy since the deployment of a wave energy plant and the installation of wave energy converters, WECs, involves installation of equipment in the sea, and in most cases offshore, which takes the cost even higher. The cost of equipment used is high due to the fact that Wave Energy is relatively a new technology and a lot of research is under way in this area to make it more efficient and less costly.
2. Effects on the environment: Even though wave energy plants may be built in such a way so that they would not be visible, there may be cases which their presence affects tourism and do not get local acceptance due to fears of a negative impact on the local economies.
3. Effects on Marine Life: In this case we may have disruption of marine life in the area due to the building or the operation of a wave energy plant. This is something which cannot be avoided but it may be controlled and minimized.
4. Breakdowns: Wave Energy Converters, WECs, are installed in the sea and in many cases offshore and thus they are exposed to strong ocean waves, storms and certainly sea water. These are factors which may lead to their frequent breakdown which results to loss of service, production of electricity, loss of income and an increase of operational costs.
5. Implementation Base: The installed base of wave energy plants is low compared to wind and solar energy plants. This means that the experiences which can be shared are less than those of other renewable energy sources.
6. Technology Improvement: The rate of improvement of the technology has been low and much lower than other RES technologies. This has an effect on cost and rate of adoption both of which follow the same pace.
7. Electricity Transmission: Quite often wave energy plants are built in areas which are remote and far from the grid and at the same away from the need for electricity. This makes the connectivity to the grid expensive and difficult.
8. Specific locations: Wave energy plants cannot be built anywhere. They are built where there is sufficient wave power to justify the investment. In some areas where the installation of a wave energy plant is justified due to sufficient wave strength there may not be sufficient funds to be invested and vice versa.

Solar Energy

Without the sun, living life on earth is indeed impossible. Sun as we known is a ball of fire that gives us light and heat. The energy that we receive from the sun is called as the solar energy. With the help of this energy serious problems regarding energy that is needed everyday can be solved. Solar energy means capturing the rays of the sun and storing and its heat. This heat can be converted with the help of solar panels into heat or electrical energy. When we talk about solar energy, there are two kinds of solar energy namely, thermal energy and electrical energy.

Thermal energy is something which we can find everywhere and is totally free of cost. It helps us ding our daily chores like dries things, clothes, heats water, and many other things.  Water can basically be heated in two ways i.e. actively and passively.  In active method, when a heating element inside the solar hot water system heats the water during hot season. In the passive method the water is pre heated and flows through a cold inlet that of a conventional electric geezer.

Electric energy, the power of the sun is used to produce electricity with the help of solar cells. It can be used through a solar home system that helps in conducting electricity where there is no power supply. Apart from that it can be used a system where the electricity supplying utility is connected to the property and lastly it can be used as a backup system where there are frequent load shedding problems.

Importance of Solar Energy:

As mentioned before solar energy is required and is important for survival of life on earth. Not only human beings, plants, animals everyone requires solar energy every day. Plants require solar energy to produce oxygen, prepare food i.e. photosynthesis. Solar energy is required to produce both pure and saltwater in oceans as it is the only source of melting the frozen ice formed on the mountain caps. Apart from that the electricity which we get to run various machines is all gained from the solar energy, thus its importance and existence is very important on a planet where there is life.

Solar energy is a clean and renewable energy. Also it’s versatile and can help in producing power for watches and calculators that do not run on batteries. It’s a clean energy because it is received directly from the sun. The fossil fuels and other gas and oil that are extracted from the mines are non renewable energy. Also they are costly and cause lot of pollution. But solar energy is something that is renewable and can be used for lots of activities. Also it is available free of cost. As fossil fuels and other oils are soon going to disappear solar energy which is available in abundant should be utilized well and hence is important.

Advantages of Solar Energy:

• An energy that is totally free of cost and saves your money as the Sun is always going to be there.
• It is an environment friendly energy and hence does not create pollution.
• Provides electricity that is helps in producing electricity with the help of solar panels.
• A silent energy provider as the solar cells do not create sounds while extracting heat from the sun and producing electricity.
• Solar energy helps in reducing the electricity bill.
• The solar energy system can work independently without any connection and can be utilized and installed in remote areas too where there is no sign of electricity.
• Solar energy helps in decreasing the harmful gasses and does not contribute to acid rains, global warming, forest destruction and other natural disasters.
• No maintenance is required for solar energy and also it does not have any specific life span
• Solar energy is used for ventilating homes  i.e. ceiling fans need electricity which is gained from solar energy
• Solar energy can be used to boil water instead of suing water heaters you can make use of the solar energy. Though you need to spend initially you will gain good benefits out of it in future.
• Solar energy can help in heating your homes and charging batteries.
• It can also be used for cooking purposes by using solar oven.
• It can be used to heat swimming pools. Suppose you have a swimming pool outside you house you can make use of solar blanket to heat water during extreme cold seasons.

Disadvantages of Solar Energy:

• Solar energy can be used only during the daytime i.e. when the sun is shining bright
• The solar collectors, panels and cells that are used to absorb heat from the sun are very expensive
• In case of cloudy climate, there would be no signs of sun and solar energy which is difficult.
• The solar batteries that are charged or needs to be charged are very heavy and require large storage space. Replacing it is also difficult.
• Its low in efficiency and requires lots of land area
• There is no consistency because the devices that require energy of the sun will only work if the delivery of photons is consistent.
• Replacing the solar energy panels is also a very difficult job.
• Installation of solar energy requires large area so that the system can provide good amount of electricity. This is a great disadvantage in places where the area is small.

Solar Reflectors

Solar thermal systems use the sun’s heat to produce electricity. Mirrored surfaces concentrate sunlight onto a receiver that superheats a liquid. Energy from the scalding liquid is either used to produce steam or is converted directly into mechanical energy. In both cases the final product is electricity.

Solar reflectors are classified by how they collect solar energy. The three most common types are parabolic troughs, parabolic dishes, and power towers.

Parabolic troughs and dishes use mirrors shaped like parabolas to focus incoming radiant energy onto a fluid-filled pipe that runs down the center of a trough. Heat from the fluid is used to boil water in a steam generator to produce electricity.

Solar reflectors use a mirrored dish to concentrate the sun’s energy onto a receiver that is located at the focal point in the center of the dish. Heat energy is then transferred to the fluid in an engine. As the fluid is heated it expands, which increases the pressure it exerts within the engine. This mechanical energy is then captured by a generator or alternator and converted to electricity.

Power towers use large flat mirrors to focus sunlight onto a receiver located on a tower.  The receiver contains fluid or molten salt, which is heated to generate steam, which is used to turn a turbine at the foot of the tower to generate electricity.

Typical solar-to-electric power plants or concentrated solar power plants require 5 – 10 acres of land for every megawatt of generating capacity.  By this standard, a 200 MW solar plant in West Texas would need about 1,300 acres (two square miles) of land.

Concentrating Solar Power (CSP) Technologies

Concentrating Solar Power (CSP) technologies use mirrors to concentrate (focus) the sun's light energy and convert it into heat to create steam to drive a turbine that generates electrical power.

CSP technology utilizes focused sunlight. CSP plants generate electric power by using mirrors to concentrate (focus) the sun's energy and convert it into high-temperature heat. That heat is then channeled through a conventional generator. The plants consist of two parts: one that collects solar energy and converts it to heat, and another that converts the heat energy to electricity.

CSP technology utilizes three alternative technological approaches: trough systems, power tower systems, and dish/engine systems.

Trough Systems

·  Trough systems use large, U-shaped (parabolic) reflectors (focusing mirrors) that have oil-filled pipes running along their center, or focal point, as shown in Figure 1. The mirrored reflectors are tilted toward the sun, and focus sunlight on the pipes to heat the oil inside to as much as 750°F. The hot oil is then used to boil water, which makes steam to run conventional steam turbines and generators.

Power Tower Systems

·  Power tower systems also called central receivers, use many large, flat heliostats (mirrors) to track the sun and focus its rays onto a receiver. As shown in Figure 3, the receiver sits on top of a tall tower in which concentrated sunlight heats a fluid, such as molten salt, as hot as 1,050°F. The hot fluid can be used immediately to make steam for electricity generation or stored for later use. Molten salt retains heat efficiently, so it can be stored for days before being converted into electricity. That means electricity can be produced during periods of peak need on cloudy days or even several hours after sunset.

Dish Engine Systems

·  Dish/engine systems use mirrored dishes (about 10 times larger than a backyard satellite dish) to focus and concentrate sunlight onto a receiver. As shown in Figure 5, the receiver is mounted at the focal point of the dish. To capture the maximum amount of solar energy, the dish assembly tracks the sun across the sky. The receiver is integrated into a high-efficiency "external" combustion engine. The engine has thin tubes containing hydrogen or helium gas that run along the outside of the engine's four piston cylinders and open into the cylinders. As concentrated sunlight falls on the receiver, it heats the gas in the tubes to very high temperatures, which causes hot gas to expand inside the cylinders. The expanding gas drives the pistons. The pistons turn a crankshaft, which drives an electric generator. The receiver, engine, and generator comprise a single, integrated assembly mounted at the focus of the mirrored dish.

Passive Solar Design

A passive solar system does not involve mechanical devices or the use of conventional energy sources beyond that needed to regulate dampers and other controls, if any. Classic examples of basic passive solar structures are greenhouses, sunrooms and solariums -- as the sun's rays pass through the glass windows, the interior absorbs and retains the heat. Modeling this concept in your home can cut heating costs by half compared to heating the same home by traditional means without the use of passive solar (see References 1). In terms of design, success of the passive solar system depends on orientation and the thermal mass of the structure's exterior walls, which means their ability to store and redistribute heat (see References 2).

Passive Solar Collectors

A passive solar system typically relies on south-facing windows as collectors to capture solar energy, although some systems may also use supplemental PV panels. In any case, the goal is to redistribute the energy collected according to a fundamental law of thermodynamics, which states that heat moves from warm to cool areas and surfaces (see References 3). The simplest method of transferring the heat from passive solar collectors is through convection. To illustrate, think of a sunroom with windows on a southern wall. As the sun's rays travel through the glass, the heat is directed into the room. It then rises to areas where the air is cooler, including other rooms beyond and above.

Heliostat

A heliostat (from helios, the Greek word for sun, and stat, as in stationary) is a device that includes a mirror, usually a plane mirror, which turns so as to keep reflecting sunlight toward a predetermined target, compensating for the sun's apparent motions in the sky. The target may be a physical object, distant from the heliostat, or a direction in space. In almost every case, the target is stationary relative to the heliostat, so the light is reflected in a fixed direction.

Nowadays, most heliostats are used for daylighting or for the production of concentrated solar power, usually to generate electricity. They are also sometimes used in solar cooking. A few are used experimentally, or to reflect motionless beams of sunlight into solar telescopes. Before the availability of lasers and other electric lights, heliostats were widely used to produce intense, stationary beams of light for scientific and other purposes.

Most modern heliostats are controlled by computers. The computer is given the latitude and longitude of the heliostat's position on the earth and the time and date. From these, using astronomical theory, it calculates the direction of the sun as seen from the mirror, e.g. its compass bearing and angle of elevation. Then, given the direction of the target, the computer calculates the direction of the required angle-bisector, and sends control signals to motors, often stepper motors, so they turn the mirror to the correct alignment. This sequence of operations is repeated frequently to keep the mirror properly oriented.

Large installations such as solar-thermal power stations include fields of heliostats comprising many mirrors. Usually, all the mirrors in such a field are controlled by a single computer.

Applications :

·         generally, there are broad uses for concentrating solar power (CSP).

·         combined heat and power (CHP) system

·         lighting and space heating for buildings

·         improved solar cooking, canning and baking. Also solar food drying

·         solar distillation of alcohol and other fuels (save biomass fuel for other uses such as biochar)

·         biomass drying, even solar torrefaction (examples of wet biomass: biogas slurry, manure, humanure, duckweed, wood etc.)

·         solar pyrolysis system for biochar production where all of the heat comes from sunlight rather than from the pyrolysis products such as bio-oil and various organic chemicals. This way, none of the pyrolysis products would have to be burned up to keep the reaction going. This would increase the efficiency of biomass use. It is an unproven idea - no designs exist.

·         enhanced lighting and heating of greenhouses

·         solar alarm clock (let's hope that the sun is shining when you have to wake up !)

·         improved electricity yield of photovoltaic cells 

·         water heating for various applications; examples: aquaponics (see Tilapia aquaculture)

·         solar thermal water treatment, disinfection, sewage treatment

·         solar desalination (see Oceansource)

·         steam (and superheated steam) for a wide variety of uses (sterilizing and cleaning things, soil sterilization, industrial process heat, etc.)

·         to power an open source modern steam engine

Gasification

Gasification is a process that converts organic or fossil fuel based carbonaceous materials into carbon monoxide, hydrogen and carbon dioxide. This is achieved by reacting the material at high temperatures (>700 °C), without combustion, with a controlled amount of oxygen and/or steam. The resulting gas mixture is called syngas (from synthesis gas or synthetic gas) or producer gas and is itself a fuel. The power derived from gasification and combustion of the resultant gas is considered to be a source of renewable energy if the gasified compounds were obtained from biomass.

In a gasifier, the carbonaceous material undergoes several different processes:

1. The dehydration or drying process occurs at around 100 °C. Typically the resulting steam is mixed into the gas flow and may be involved with subsequent chemical reactions, notably the water-gas reaction if the temperature is sufficiently high enough (see step #5).
2. The pyrolysis (or devolatilization) process occurs at around 200-300 °C. Volatiles are released and char is produced, resulting in up to 70% weight loss for coal. The process is dependent on the properties of the carbonaceous material and determines the structure and composition of the char, which will then undergo gasification reactions.
3. The combustion process occurs as the volatile products and some of the char reacts with oxygen to primarily form carbon dioxide and small amounts of carbon monoxide, which provides heat for the subsequent gasification reactions. Letting C represent a carbon-containing organic compound, the basic reaction here is
4. The gasification process occurs as the char reacts with carbon and steam to produce carbon monoxide and hydrogen, via the reaction
5. In addition, the reversible gas phase water-gas shift reaction reaches equilibrium very fast at the temperatures in a gasifier. This balances the concentrations of carbon monoxide, steam, carbon dioxide and hydrogen.

Applications :

Heat

Gasifiers offer a flexible option for thermal applications, as they can be retrofitted into existing gas fueled devices such as ovens, furnaces, boilers, etc., where syngas may replace fossil fuels. Heating values of syngas are generally around 4-10 MJ/m³.

Electricity

Currently Industrial-scale gasification is primarily used to produce electricity from fossil fuels such as coal, where the syngas is burned in a gas turbine. Gasification is also used industrially in the production of electricity, ammonia and liquid fuels (oil).

Combined heat and power

This type of plant is often referred to as a wood biomass CHP unit but is a plant with seven different processes: biomass processing, fuel delivery, gasification, gas cleaning, waste disposal, electricity generation and heat recovery.^[22]

Transport fuel

Diesel engines can be operated on dual fuel mode using producer gas. Diesel substitution of over 80% at high loads and 70-80% under normal load variations can easily be achieved.^[23] Spark ignition engines and SOFC fuel cells can operate on 100% gasification gas.^[24][25][26] Mechanical energy from the engines may be used for e.g. driving water pumps for irrigation or for coupling with an alternator for electrical power generation.

Photovoltaic cell (PV Cell)

 

 

A photovoltaic cell (PV cell) is a specialized semiconductor diode that converts visible light into direct current (DC). Some PV cells can also convert infrared (IR) or ultraviolet (UV) radiation into DC electricity. Photovoltaic cells are an integral part of solar-electric energy systems, which are becoming increasingly important as alternative sources of utility power.

The first PV cells were made of silicon combined, or doped, with other elements to affect the behavior of electrons or holes (electron absences within atoms). There are two basic types of semiconductor material, called positive (or P type) and negative (or N type).

A typical silicon PV cell is composed of a thin wafer consisting of an ultra-thin layer of phosphorus-doped (N-type) silicon on top of a thicker layer of boron-doped (P-type) silicon. An electrical field is created near the top surface of the cell where these two materials are in contact, called the P-N junction. When sunlight strikes the surface of a PV cell, this electrical field provides momentum and direction to light-stimulated electrons, resulting in a flow of current when the solar cell is connected to an electrical load

Figure 1. Diagram of a photovoltaic cell.

Regardless of size, a typical silicon PV cell produces about 0.5 – 0.6 volt DC under open-circuit, no-load conditions. The current (and power) output of a PV cell depends on its efficiency and size (surface area), and is proportional to the intensity of sunlight striking the surface of the cell.

Large sets of PV cells can be connected together to form solar modules, arrays, or panels. The use of PV cells and batteries for the generation of usable electrical energy is known as photovoltaics. One of the major advantages of photovoltaics is the fact that it is non-polluting, requiring only real estate (and a reasonably sunny climate) in order to function. Another advantage is the fact that solar energy is unlimited. Once a photovoltaic system has been installed, it can provide energy at essentially no cost for years, and with minimal maintenance.

Fuel cell

A fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent.^[1]

There are many types of fuel cells, but they all consist of an anode, a cathode and an electrolyte that allows charges to move between the two sides of the fuel cell. Electrons are drawn from the anode to the cathode through an external circuit, producing direct current electricity. As the main difference among fuel cell types is the electrolyte, fuel cells are classified by the type of electrolyte.

Fuel cells are used for primary and backup power for commercial, industrial and residential buildings and in remote or inaccessible areas. They are also used to power fuel-cell vehicles, including forklifts, automobiles, buses, boats, motorcycles and submarines.

The electrolyte substance usually defines the type of fuel cell.

The most important design features in a fuel cell are:

• The fuel that is used. The most common fuel is hydrogen.
• The anode catalyst breaks down the fuel into electrons and ions. The anode catalyst is usually made up of very fine platinum powder.
• The cathode catalyst turns the ions into the waste chemicals like water or carbon dioxide. The cathode catalyst is often made up of nickel but it can also be a nanomaterial-based catalyst.

A typical fuel cell produces a voltage from 0.6 V to 0.7 V at full rated load.

Advantages

• Fuel cells eliminate pollution caused by burning fossil fuels; the only by-product is water.
• If the hydrogen used comes from the electrolysis of water, then using fuel cells eliminates greenhouse gases.
• Fuel cells do not need conventional fuels such as oil or gas and can therefore eliminate economic dependence on politically unstable countries.
• Since hydrogen can be produced anywhere where there is water and electricity, production of potential fuel can be distributed.
• Installation of smaller stationary fuel cells leads to a more stabilized and decentralized power grid.
• Fuel cells have a higher efficiency than diesel or gas engines.
• Most fuel cells operate silently, compared to internal combustion engines
• Low temperature fuel cells (PEM, DMFC) have low heat transmission which makes them ideal for military applications.
• Operating times are much longer than with batteries, since doubling the operating time needs only doubling the amount of fuel and not the doubling of the capacity of the unit itself.
• Fuel cells have no “memory effect” when they are getting refueled.
• The maintenance of fuel cells is simple since there are few moving parts in the system.
• Fuel cells provide high quality DC power.
• The absence of combustion and moving parts means that fuel cell technologies are expected to provide much improved reliability over traditional combustion engines.
• Use a variety of fuels, renewable energy and clean fossil fuels.
• The power densities are high values.
• Cogeneration Capability.
• Fuel cells can be responsive to changing electrical loads.
• Fuel cell operating temperatures vary from around 80°C for low-temperature PEMFCs to around 1000°C for MCFCs. Temperatures inside combustion engines may reach over 2000°C.

 

Disadvantages

• Fuelling fuel cells is still a major problem since the production, transportation, distribution and storage of hydrogen is difficult.
• Reforming hydrocarbons via reformer to produce hydrogen is technically challenging and not clearly environmentally friendly.
• The refueling and the starting time of fuel cell vehicles are longer and the driving range is shorter than in a “normal” car.
• Fuel cells are in general slightly bigger than comparable batteries or engines. However, the size of the units is decreasing.
• Fuel cells are currently very expensive to produce, since most units are hand-made.
• Some fuel cells use expensive materials.
• The technology is not yet fully developed and few products are available.