Renewable sources of energy

Renewable sources of energyEnergy sourcesEnergy is the primary and most universal measure of all kinds of work by human beings and natureThe flow of energy is one of its formsDivided into 3Primary energy sourcesSecondary fuelsSupplementary sourcesPrimary energy sourcesA source which provide net supply of energyEg coal, oil, uraniumThe energy required to obtain from these fuels is much less than what they can produce by combustion and nuclear reactionTheir energy yield ratio is very high yield ratio the energy fed back by the material to the energy received from the environmentThis can only accelerate growth, but supply is limitedIt becomes very essential to use these fuels sparinglySecondary fuelsProduce no net energyBut they necessary for economyIntensive agricultural is an example, where in terms of energy the yield is less than the inputSupplementary fuelsNet energy yield is zeroBut they require highest investment in terms of energyThermal is an example

Coal, natural gas , oil and nuclear energy using breeder reactor are net energy yieldersSolar energy, wind energy, water energy are secondary sources of energySolar energy can be used through plants, solar cells and solar heaters.Geothermal and ocean thermal other sources

Energy sources and their availabilityCommercial or conventional energy sourcesMajor sources fossil fuelsWater power or energy stored in waterEnergy of nuclear fissionMinor sourcesSunWindTides in seaGeothermalOcean thermal electric conversionFuel cellsThermionicThermoelectric generatorsWood was dominant in pre industrialization era.Percentage use of various sources for the total energy consumption in the world

coal32.5% 92%Oil38.3%Gas19.0%Uranium0.13%hydro2.0%Wood6.6% 8%Dung1.2%waste0.3%Coal

Since the advent of industrialization coal has been the most common source of energy.Last 3 decades it is switched to oilCoal developed from vegetable matter which grew on past geological ages.trees and plants falling into water, decayed and producing peat bogs. These bogs are buried under layers of silt,due to soil pressure,heat and movement of earth crust distilled off some gaseous matter in bog and form brown coal or lignite, continuing this activity and reducing gaseous content progressively , forming peat lignite, bituminous and anthracite.

Oil Almost 40% of the energy needs of the world are fed by oilRising prices of oil making little strain on economyBut, with todays consumption and a resource amount of 250000million tones of oil, which is sufficient for about 100 years Refining petroleum or crude oils produce our fuel oilsThe potential oil bearing areas are located in Assam, Tripura , Manipur, West Bengal , Ganga valley, Punjab, Western coastal area,Gas Incompletely utilized at present and huge quantities are burned off in oil production processTransportation cost is hugeClassified asGases of fixed composition such as ethylene, methane..Composite industrial gases such as producer gas , coke oven gas, water gas , blast furnace gas etc.Agricultural and organic wastesat present a small amount of these are utilized for energy purposeMost of the unused material will cause considerable environmental problems.11Major points considered when using this source isThe waste should utilized near the source, in order to reduce the transportation costAppropriate equipments for burning or extracting energy from materials should be developed to suit local conditions and meet the requirements of the local areasOther non energy uses of the material should also be consideredConsidering the availability and the location of the material produced, these are regarded as an important energy supply for the rural areas.

Water powerDeveloped by allowing water to fall under the force of gravity.Used extensively for electric power generationPotential energy of water is converted to mechanical energy by using prime movers known as hydraulic turbines.It is quite cheap because of abundant availability of waterCapital cost is very high but operating cost is lowNo fuel requiredNuclear powerAccording to modern theories of atomic structure, matter consisting of minute particles known as atomsBetween them have a large binding energyControlled fission will release this energyThe energy released by the complete fission of 1kg uranium is equal to the heat energy obtained by burning 4500 tons of coal or 2200 tons of oil.

Non conventional sourcesBecause of large energy requirements and utilization, fossil fuels are exhausted eventually in futureIndustrialized countries put their concentration on renewable energy sources, some of them are

Solar energyWind energyEnergy from biomassOcean thermal energyTidal energyGeothermal energyHydrogen energyFuel cellsMagneto hydro dynamics generatorThermionic converterThermo electric power

Solar energyEnergy comes to the earth from sun This keeps the temp. of the earth above that in colder space, cause current in atmosphere and in ocean, cause water cycle and generate photosynthesis in plantsSolar power where sun hits to atmosphere is 10^17 W, that to earths surface is 10^16WThe world wide power demand is 10^13 WThe energy radiated by the sun on a bright sunny day is approximately1kW/m^2, this can be utilized to generate steam , and used to drive prime movers in the case of generation of electric energy.But their use is limited because of some reasons like, they required large space, uncertainty of availability of energy at constant rate due to cloud, wind etc

Applications of solar energy which enjoying success today are,Heating and cooling of residential buildingSolar water heatingSolar drying of agricultural and animal productsSolar distillation on a small community scaleSalt production by evaporation of sea water Solar cookersSolar engines for water pumpingFood refrigerationBio conversion and wind energy, which are indirect source of solar energySolar furnacesSolar electric power generation by-Solar pondsSteam generators heated by rotating reflectors or by tower conceptReflectors with lenses and pipes for fluid circulation12. Solar photovoltaic cells

Wind energyEnergy of wind can be economically used for electric power generationWinds are caused from-Heating and cooling of atmosphere which generates convection currents. Heating is caused by the absorption of solar energy on the earths surfaceThe rotation of the earth with respect to atmosphere and its motion around the sunThis is an indirect form of solar energy, used to run windmill, which in turn runs a generator to produce electricityIt can generate an estimated amount of 1.6*10^7MWSome types of windmills are- multi blade type windmillSail type windmillPropeller type windmillSavonius type windmillDarrieus type windmill

Some characteristics of wind energy are-It is a renewable source of energyLike all forms of solar energy ,wind power systems are non polluting , there is no adverse effect on environmentWind energy systems avoid fuel provision and transportOn small scale , it is less costly, for large scale, costs be competitive with conventional electricity and lower cost could be achieved in mass production

Problems associated with wind energyWind energy available in dilute and fluctuating manner, because of this reason conversion machine have to be necessarily largeUnlike water energy, wind energy need storage means because of its irregularity.Wind energy systems are noisy in operation, a large unit can be heard many kilometers away.Large areas are needed to install wind farms for electrical power generation.Energy from biomass and biogasThe potential for application of biomass as an alternate source of energy in India is greatWe have plenty of agricultural and forest resources for biomassIt is produced in nature through photosynthesisIt is an organic matterEnergy released by burning biomass is approximately 112kcal/mol ie, 469kJ/moleIt can be used directly by burning or can processed to produce convenient liquid and gaseous form

Biomass resources categorized into 3,In its traditional solid mass (wood and agricultural residues)In its non traditional form (converted in to liquid form)Ferment biomass anaaerobically to obtain a gaseous fuel called biogasBiomass resources includeConcentrated waste municipal solids , sewage wood products , industrial wastes, manure of large lotsDispersed waste residue crop residue, legging residue,disposed manureHarvested biomass, standby biomass, biomass energy plantation Energy plantationFor large scale production of electric power, can use fire wood as a fuelFor that selected species of trees are planted and harvested in regular period of time for large area , near to the plant,In India , suggested trees are eucalyptus, casuarina and baboolBiogas Main source of production biogas is wet cow dung, livestock wasteIn India, we have large cattle population, its population is 250millionOther sources areSewage , crop residue , vegetable wastes, poultry wastes ,

In big cities , sewage source is the main source for the production of biogas, and which is used to run pumps to pumpout the sewage water itselfThe sewage biogas contain 84% in rural areas, biogas can be used for cooking, lighting, mechanical power and small electricity generation.

Ocean thermal energyIndirect method of utilization of solar energyLarge amount of solar energy collected and stored in tropical oceansTropic oceans- equatorial band between the tropic of cancer and the tropic of CapricornIncluding central portions of pacific and Atlantic oceans, and most of Indian ocean They play a critical role in regulating earths climate and large scale weather patternThus, heat contained in oceans could be converted into electricity by utilizing the fact that the temperature difference between warm surface waters of the tropical oceans and the colder waters in the depth is about 20-25 degree K

OTEC system utilization of energy, with its associated temperature difference and its conversion into workThe surface water with high temperature is used to heat some low boiling organic fluid, by using this vapours we can run a heat engine, the exit vapour would be condensed by pumping colder water from deeper regions.Tidal energyTides in the sea are the result of the universal gravitational effect of heavenly bodies like sun and moon on earthDue to the fluidity of water mass, this effect can be apparent in the motion of water, which causes a periodic rise and fall in water levels, this is due to the daily cycle of rising and setting of sun and moonThis periodic rise and fall of water level of sea is called tide, electricity generated from this tide is known as tidal power. Water level is above the mean sea level flood tideWater level is below the mean sea level ebb tide

For practical electric power generation from tide need some favorable site ie, geography of inlet or bay must be suitable for the construction of large scale hydroelectric plant dam would be built on the mouth of the bayIt will have large gateA low head hydraulic reversible turbine is installedA tidal basin is formed, dam separates basin and seaDifference in water level is obtained in basin and sea, basin filled during high tide and emptied during low tideThis arrangement is known as single basin plant.Geothermal energyEmbedded with in the earthAccording to various theories, earth has a molten core, that relating to volcanic actionVolcanic action - stem and hot water coming outside from earth core with temp. of 200 or 300 degree C, with pressure of 3000kN/m^2Two ways of electric power generationHeat energy transferred to a working fluid which operates the power cycleHot water and steam used directly to operate the turbines,

Hydrogen energyIt is a non conventional energy resource but hydrogen is used as a alternate source of conventional energy.Because of technical problems of production, storage, transportationSo the expense is very highthe advantage of using hydrogen as a source is that can be produced from waterIt has higher energy content per unit massHave large combustion efficiencyIts burning process is non polluting and this can be used in fuel cell to produce both electricity and useful heat

Fuel cellsElectro chemical device, electrical energy produced from chemical energyMain components of cell areA fuel electrodeAn oxidant or air electrodeAn electrolyteFuel cells used in industries are,Hydrogen oxygen cellHydrazineCarbon/coalmethaneHydrogen oxygen (hydrox) are more efficient and the most developed cell

Hydrox cell have two porous electrode, material used are either carbon or nickelAn electrolyte of 30% KOH is used, due to its high electric conductivity and corrosive action comparing with acidThe cell operates with normal atmospheric pressure and at a temp about 90 degree C then it is called low temp cellsThe cell operates with pressure upto 45atm and temperature upto 300 degree C are called high pressure cells

A single hydrox cell can produce an emf of 1.23voltSome advantages of fuel cellDirect conversion process, so high operating efficiencyLighter and smaller so need less maintenanceTransmission losses are very low so generation cost get reducedProduce little pollution and little noise so acceptable in residential areasDrawbacks low voltage, high initial cost and low service lifeMagneto Hydro-Dynamics generatorDirect conversion of heat energy into electrical energyObeys Faradays law of electromagnetic inductionWhen an electric conductor moves across a magnetic field , a voltage is induced in it which produces an electric currentInstead of solid conductors using fluid which is electrically conducting

Working principle partially ionized and compressed gas is expanded in a duct and which is forced through a strong magnetic field so an electric potential is developed in the gas, by connecting 2 electrodes on the sides of duct, we can pick up the potential, which is a DC, by connecting an inverter to this arrangement we can generate ACPower generation is simple, and has large power and temperature handling capacityNo moving parts, so high reliabilityIt can brought full power from standby conditions with in 45 secondsLoad variation also take fraction of second

Thermionic converter direct conversion of heat energy to electrical energyConsist of 2 electrodes held in a container filled with ionized cesium vapourWorking principle- heating one electrode boils out electrons that travel to the opposite colder. Electrode. The positive ions in the gas neutralize the space charge effect of electrons that is prevent the flow of electronsHeating electrode cathode Material tungsten impregnated with a barium compoundCooler electrode anode Material barium and strontium

Thermo electric powerDirect conversion of heat energy to electrical energyPrinciple is based on seebeck effectStates that if two dissimilar materials are joined to form a loop and the junctions are maintained at different temperatures, then an emf will developed around the loopThe hot junction is created by heating that junction using a heat source ie, oil or gas burnerThe cold junction is created by water cooling or radiative heat transfer

SOLAR ENERGYSolar energy received from sun in the form of radiations, which can be converted in to any other forms such as heat and electricityMajor drawbacksThe intermittent and variable manner in which it arrives at earths surfaceThe large area required to collect the energy at a usable rateDirect radiation - the radiation, that has not been absorbed or scattered and reaches the ground directly from sun Diffuse radiation - the radiation, that received from sun after changing its direction by reflection or scattering by the atmosphereInsolation the total solar radiation energy received on a horizontal surface of unit area on the ground in unit timeSolar collector a device for collecting solar radiation and transfer the energy to a fluid passing in contact with itTwo types concentrating type solar collectorsNon concentrating type solar collectorsMain components- solar energy collector and associated absorberGreen house effect it is possible to grow exotic plants in cold climates through better utilization of the available sunlight,

Flat plate collectors- can collect and absorb both direct and diffuse radiations, they are also effective in cloudy days when there is no direct radiationDivided into 2 types on the basis of heat transfer fluid used. Liquid heating collectorsAir or gas heating collectorsHave mainly 5 componentsA transparent coverTubes , finsThe absorber plateInsulation The casing or container A typical liquid collectorPlate and tube type collectorFlat surface with high absorptivityMetal plate copper, aluminium, steelTube is in line and integral with the metal plateHeat will transferred from the metal plate by the circulation of water through the tubeFor front cover usually uses glassDrawbacksIn cold weather, moisture may condense the inside of transparent cover and reduce the heat transferring rateCorrosion of metal tubes by waterLeakes in water circulation

Typical air collectors or solar air heatersUsing air as a heat transferring mediumThe drawbacks of liquid collectors are solved here.Drawbacks of air collectors are. large duct size and higher flow rate , with increased pumping powerTransfer of heat from air is also difficultClassified into twoNon porous absorber- air may flow above and or behind the absorber platePorous absorber- absorber plate has slits

Give a brief review of conventional sources of energyWrite a note on thermal storage.Write a detailed note on Global warming and Green house effect. Explain solar absorption refrigeration system in detail. Give a description of flat plate collectors and the working of solar water heater. What are the advantages and applications of renewable energy sources?Briefly describe the principle of thermionic converter.Explain the methods of solar thermal power generation.Describe in brief, the different energy storage methods used in solar system.Explain the design and fabrication of flat plate collectors also discuss about its performance

Application of solar air heatersHeating buildingsDrying agricultural productsHeating green housesAir conditioning buildingsAdvantages of flat plate collectorsThey have the advantages of using beam and diffuse radiationThey do not orientation towards the sunThey require little maintenanceThey are mechanically simpler than concentrating type collectors