Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved.

ENERGY Primary (from natural resources such as coal, crude oil) Renewable (inexhaustible such as solar and wind energy) Non-Renewable (cannot be regenerated in a short time span such as coal, petroleum, natural gas) Secondary (derived from natural resources such as petrol, diesel) Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Limitations of Fossil Fuels 1.They are non-renewable energy resources. Formation of fossil fuels takes millions of years. So they will eventually run out. 2.Because fossil fuels are energy-rich, so there is always a high danger of fire and explosions when they are being extracted, processed, transported and stored. 3.Extraction of coal from mines is a dangerous task which poses health hazards in lives of mine workers. Crude oil is toxic in nature and contains carcinogenic compounds. 4.Coal contains high percentage of water, so when it burns, energy is wasted in evaporating its own moisture content. 5.On burning, they produce a large amount of greenhouse gases, such as carbon dioxide, which cause environment pollution and global warming. 6.In addition, they produce other acidic gases such as NO 2, SO 2, SO 3 that dissolve in moisture present in air and cause acid rain which is harmful for plants animals and damages buildings. 7.The polymers obtained from petro-chemicals are non-biodegradable and cause environmental pollution. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Nuclear Energy Nuclear energy may be considered non-conventional even though it has become an established source of energy for about 50 years now. Nuclear energy is the energy released when the nuclei of certain atoms undergo nuclear reactions. Such materials used to release energy are called nuclear fuels. Nuclear Binding Energy Nuclear Reactions Nuclear reactions differ from chemical reactions in terms of energy considerations. The energies associated with nuclear reactions are several orders of magnitude larger than those associated with chemical reactions. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Nuclear Reactions in the Sun The pressure inside the core of the Sun is high enough which pushes the hydrogen atoms close to each other. The two hydrogen atoms combine to yield a bigger atom, that is, helium with a large amount of energy release. This process is not a single step process, but takes place in multiple steps: Step 1: Two protons combine to form a deuterium, a positron (or antielectron) and a neutrino: Step 2: A proton and deuterium combine to form a 3 He atom and a γ-ray (photon): Step 3: Two 3He atoms combine together to yield a 4 He atom and two protons: Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

The net energy released is 26 MeV. These reactions are responsible for 85% of the Sun’s energy. The remaining 15% can be accounted for by the following reactions: Step 1: 3 He and 4 He combine to form 7 Be and a γ- ray (photon): Step 2: The 7 Be captures an electron to yield 7 Li and a neutrino: Step 3: The 7 Li combines with a proton to form two 4 He, a positron and a neutrino: Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Nuclear Power Reactor Nuclear reactors are designed to carry out nuclear reactions for generation of electricity, heat, radioactive isotopes and nuclear chemistry research. Parts inside the core of nuclear reactor Fuel rodsModeratorControl rodsCoolant Steam generator Containment Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Classification of Nuclear reactors Thermal neutron reactors Light water moderated reactors (LWRs) Heavy water moderated reactors Graphite moderated reactors Fast neutron reactors Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Breeder Reactors Breeder reactors generate new fissionable material at a rate greater than their consumption rate. Due to their superior fuel economy, they are highly in demand. Types of Breeder Reactors Fast breeder reactor Thermal breeder reactor Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved Nuclear Fuel Cycle Mining and milling of uranium ConversionEnrichmentFuel fabrication Use of fuel in nuclear reactor Removal of spent fuel Disposal of spent fuel

Disadvantages of Nuclear Energy The major disadvantage associated with the nuclear energy is the expulsion of radiation. The nuclear radiations penetrate deep into the body, damage cells and lead to illness, and sometimes even death. Any malfunction in the nuclear reactor may lead to leakage of radiation and people exposed to it may be susceptible to illness, years after exposure. The radioactive waste from nuclear reactors is hazardous and once it enters the biosphere (ecosystem), it will take years to decay to safe levels. Another disadvantage of nuclear energy is a disaster known as meltdown. This occurs when a nuclear reaction goes out of control leading to a nuclear explosion, thereby producing a lot of harmful radiation. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Safety Measures and Nuclear Waste Disposal For nuclear waste disposal, it is a common practice to determine radioactive content of the waste and half-life of radioactive substances. The radioactive waste is grouped into following three categories and the suitable disposal method determined accordingly. 1.Low-level waste 2.Intermediate- level waste 3.High-level waste Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

The various safety measures have been designed so that there is no adverse impact due to handling radioactive material in nuclear reactors. These include: 1.Nuclear power plants are designed in such a way that accidents are avoided, however, in case of any accident or unusual event, the following safety measures are adopted: a) Shutting down operating reactors. b) Cooling down reactors, to remove heat from nuclear fuel. c) Preventing leakage of radioactive materials to surroundings. 2.At the time of design and construction of nuclear power plant safety measures are taken against earthquakes. 3.Periodically radiation dose in air, seawater, soil is monitored to measure and analyze radioactive material content and check any adverse effects on surrounding environment. 4.In addition to the above mentioned measures, strict tests and monitoring are performed to comprehensively evaluate safety of power plants. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Solar Energy Solar energy is the radiant energy due to illumination of the Sun. It can be converted into various forms of energy like thermal and electrical energies. The main advantages of using solar energy as an energy source are that it is readily available, free of cost and eco-friendly. Applications of Solar Energy To name a few, solar calculators, solar watches are some of the useful applications of solar energy in our day-to-day lives. In addition, this energy source is also harnessed to provide basic necessities in the rural regions. Domestic water supply and irrigation in villages is done by using solar pumps. The light installations in villages like streets and tunnels, educational institutions and healthcare centers are mostly dependent on the Sun’s energy. In such remote areas, this has been the choice of power supply since a decade now. Also, the direct rays of Sun are used to provide warmth in the houses. It is also helpful in cooking via the solar cookers or to warm up water using solar water heaters. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Conversion of Solar Energy Solar energy may be converted into more useful forms of energies by two pathways − thermal conversion and photo-conversion. In thermal conversion, the heat from direct rays of Sun is absorbed in the form of infrared radiation by the surfaces, air or water and put to many uses. 1.The low-temperature heat from the sun may directly heat the buildings to provide warmth. In some cases flat plate collectors may be used to collect heat. 2.Water in solar ponds can be used to collect solar energy and store it for later use. A salt gradient is maintained in the three zones of the pond − the surface zone, gradient zone and the storage zone. 3.The temperature difference between two surfaces heated by solar energy may be converted into electricity in accordance with the Seeback effect. 4.The heat from solar energy may be used to carry out thermochemical reactions. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Photovoltaic Cells Photovoltaic or solar cells convert solar energy into electricity. These are made up of semiconductors like diodes, integrated circuits and transistors. Various solar cells have been designed with different materials, so as to give a higher efficiency at a low cost; however, crystalline silicon cells, though expensive, are still the most effective ones. Forward-biased p–n junction photodiode. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Importance of Photovoltaic Cells 1.Earth receives a large amount of solar energy, that is, almost 6000 times more than the average electrical power consumed by humans. 2.Additionally, it is available to us free of cost and is completely pollution free during its usage. 3.Solar electricity generation offers many advantages amongst all other renewable energy sources. 4.Even though the construction cost is high, operating and maintenance costs are extremely low compared to the other means, therefore, it is highly economical to use. 5.High-efficiency solar cells have efficiencies of over 40% and their efficiencies are increasing day by day, while the production costs are declining. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Some other advantages of photovoltaic cells are as follows: 1.They operate at ambient temperature. 2.Their parts do not corrode or suffer wear and tear. 3.They do not need to be recharged. Photovoltaic cells have some disadvantages associated with their use such as: 1.These are expensive to install. Once the system is installed, the cell goes on producing power free of cost till the inverter needs further replacement. 2.Solar energy is not available throughout day and night and also not equally in all seasons and areas. Therefore, a storage system is required. However, there is a solution to this, whereby using germanium in amorphous Si–Ge thin- film solar cells, residual power can be generated at night due to background infrared radiation. 3.The photovoltaic devices only produce DC voltage. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Silicon A semiconductor is neither a conductor nor an insulator, but is something in between these two extremes. Its electrical resistivity lies in between that of a conductor and an insulator, and also can be monitored easily. Silicon, till date, is the most popular semiconductor material used to make photovoltaic cells. This is because it is cheap but highly efficient. Other semiconductors such as gallium arsenide, cadmium telluride, cadmium sulphide, etc., are used for making special- purpose high-efficiency photovoltaic cells. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Production of Solar Cell Grade Silicon Pure silicon is not available on earth. It comes in the type of quartz sand which is heated with carbon (metallurgical coke) in an electric arc furnace. Silicon is formed as per the following reaction: Silicon is first mixed with HCl to obtain trichlorosilane and some amounts of tetrachlorosilane. Pure trichlorosilane so obtained is passed through a fixed-bed column containing quaternary ammonium ion exchange resin acting as a catalyst to convert it into silane Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Doping of Silicon Pure semiconductor grade silicon needs to be incorporated with impurities for it to develop semiconductor properties. This process is known as doping and a number of doping techniques are used. 1.Doping may be carried out at the crystal formation stage by adding appropriate amount of impurities. The dopant can be deposited on the metal rod along with the molten silicon by mixing suitable compounds with the reaction mixture. For example, phosphine (PH 3 ) is mixed with the reaction mixture feed to get n-type semiconductor and boron trihydride (BH 3 ) is mixed for a p-type semiconductor. 2.A dopant can be incorporated on a region of semiconductor material by diffusion of the impurity into the crystal of the material without actually melting it. The technique is known as diffusion technique and is carried out by heating the silicon wafer in presence of the impurity below its melting point. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

The advantages of hydropower: 1.Multiple-use dams provide a constant supply of water for irrigation and agriculture. 2.Hydropower is non-polluting and a renewable source of energy. 3.The hydroelectric power plants are usually automated and do not require on- site manual labor during normal functioning, thereby cutting down the expenses. The construction cost of the plant is also not so high. Disadvantages of hydropower: 1.It has large environmental impacts and affects the flora and fauna of the river and the land nearby. 2.The temperature of the river water can also change due to the fall of water and this affects the population of fishes and other aquatic life. 3.A small amount of carbon dioxide (a green house gas) is also produced during the generation of electricity in hydropower plant. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

The advantages of wind energy: 1.The wind is available free of cost and this method of energy generation proves to be highly efficient. 2.It does not cause any sort of pollution of greenhouse gases or any other pollutants. 3.The power plant takes a very small area to be installed, keeping the rest of the land for other useful purposes. The disadvantages of wind energy: 1.The force of wind is not constant all the time and varies depending on the climatic conditions. 2.The wind turbine leads to noise pollution, and are not silent like the other renewable sources of energy. 3.The manufacturing process of wind turbine leads to some pollution, but once made, they supply clean electricity. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Geothermal Energy Underground hot water or steam is used to generate electricity. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

The advantages of geothermal energy: 1.Geothermal energy is one of the best sources of energy. 2.A geothermal power plant does not cause any sort of pollution and it requires a very small space to be built upon, which reduces great deal of expenditure. 3.No fuel is required to produce electricity, thereby reducing the running costs. Hence, it is the most clean, simple, economical and renewable energy source. The disadvantages of geothermal energy: 1.To find a best location to build the power plant is the main point of concern. The selection of location should be such that it should give very high temperature of underground water. 2.If the survey result gives a positive response, proper care must be taken during construction and a provision must be provided to withstand any leakage of harmful gases from deep within the Earth or through the holes drilled. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

The advantages of tidal and wave power: 1.It is a reliable energy source, and tides are easily predictable. 2.Once built, its maintenance is not so expensive and tidal power is available free. 3.It does not emit out any greenhouse gases or any other waste. The disadvantages of tidal and wave power: 1.It only provides power at the time of tide, that is, after about 10–12 h, but not regularly. 2.Cost of building a dam across an estuary is expensive and also affects the upstream as well as the downstream environment to a large extent. A solution to this problem is the construction of offshore turbines and vertical-axis turbines, which are not only cheaper to build, but also have less environmental impact. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Ocean Thermal Energy Electricity is produced on the basis of temperature difference between the warmer top layer and colder deep layer. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved Types of OTECClosed-cycle OTECOpen-cycle OTECHybrid OTEC

The benefits of using OTEC apart from power generation are as follows: 1.The production of desalinated water which serves drinking purposes and irrigation. 2.Its use for power electricity production results in air-conditioning. 3.Spent cold water can be used to decrease temperature of freshwater in a heat exchanger or flow directly into a cooling system. 4.Likewise, spent out water from the OTEC plant can be used for chilled soil agriculture. Chilled water cools down the surrounding soil while flowing through the underground pipes, thereby creating a healthy environment for many plant varieties that evolved in the temperate climates to grow in the subtropics. There are some disadvantages also, such as: 1.OTEC power plant requires a vast initial investment of capital. 2.There are only few suitable sites in the tropics that would favor the OTEC power plants. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Biomass and Biofuels Biomass is a renewable energy source that includes all organic matter like plants and animals along with their residues, garden waste, agricultural and forest residues. Thus, harvesting CH 4 is advantageous because: 1.It provides heat and electricity. 2.It also reduces greenhouse potential. 3.Using biofuels in automobiles decreases the air pollution and hence large- scale development of such energy sources must be implemented. 4.Recently, compressed natural gas (CNG) and liquefied petroleum gas (LPG) have emerged so as to replace petrol from being used as a fuel in automobiles. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Hydrogen Energy 1.Hydrogen is the simplest element present, having atomic number 1. It is also the most abundant gas present in the Universe. 2.The Sun, and many other stars are made up of hydrogen. Nuclear fusion 3.Reactions occur inside the Sun wherein hydrogen atoms combine to form bigger nucleus, that is, helium and a lot of radiant energy. 4.However, hydrogen never exists as gas on the Earth and is always present in combined form with either oxygen in the form of water, or with carbon in the form of hydrocarbons. 5.Hydrocarbons are the constituents of various fuels: Gasoline, methanol, propanol, natural gas, etc. Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved

Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved.

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Engineering Chemistry (revised edition) ISBN: 978-81-265-4475-2 Copyright©2014 Wiley India Pvt. Ltd. All Rights Reserved.

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