NONCONVENTIONALENERGY RESOURCES
K.LAKSHMIDURGA
2/4 ECE
[email protected] cell:9848417555
A.N.S.HARIKASRI
2/4ECE
[email protected] cell:9885158288
BAPATLA ENGINEERING COLLEGE BAPATLA .
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ABSTRACT Energy is a critical component in the development of any country and more so in the industrialization is very context context of the develop developing ing countr countries. ies. Rapid industrialization very ofte often n hamper hampered ed due to
inadequ inadequate ate energy energy availab availabili ility ty.. Communi Communicat cations ions,, health health,, shelte shelterr and other other basic basic needs needs of the society are also very much restrained by inadequate availability of energy at several several phases and sometimes sometimes it to such an extent that it even brings brings the whole process process of planning in that sector sector to a stand still. Conventional Hydro Power and Thermal Energy (from coal) had played a very import important ant role role in the indust industria riall develo developme pment. nt. However However,, the oil crisis crisis start starting ing from from 1973 had brought to focus that renewable energy sources have a very important role to play since the price of a non-renewabl non-renewablee source could be changed often adversely to the developmental developmental interests interests of the poorer countries.Often the technologies relating to the other sources of energy are not so well developed and fine-tuned to have a high degree of efficiency in utilization. However, if one were to look at the economic cost and the way some of these can be suitably priced it becomes apparent that many of the alternative sources of energy are already in a position to compete with conventional energy sources. Solar Energy and Wind Energy appear as natural sources of such renewable energy options and these have been used in many countries somewhat successfully. On the other hand, there are many other sources of alternative energy forms such as Biomass, Bio fuels, Hydrogen Energy and the like which when developed could have an importance role in meeting the energy needs in the countries of the region. non conventiona conventionall energy resources for The paper paper illustra illustrates tes the use of various various non non bio mass mass,, sun sun ligh light, t, wind, wind, tide tidess and and foss fossil ilss which power power genera generatio tion, n, which which includ includee bio which are viable alternat alternative ive to the trad abunda abundant ntly ly avai availa lable ble,, to gener generat atee power power as a viable tradit itio iona nall and fast fast
depleting hydro and thermal resources.
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BIOELECTRICITY Electricity is the key to economic development development for any country. The conventional conventional fossil fuel resources for power generation are fast depleting and there is a growing concern over the
enviro environme nmenta ntall degrada degradation tion caused caused by convent convention ional al power power plants plants.. Against Against such such impli implicat cations ions,, power generation from non-convent non-conventional ional resources assumes greater greater significance significance.. Among the various renewable energy sources, biomass conversion technologies appear to be one of the best suited for conversion to shaft power/electricity.
Among Among the various various renewa renewable ble energy energy source sources, s, bio-resources, of which which agro-r agro-resi esidue due forms a major component, hold special promise as future fuel and feedstock. Biomass-based syst systems ems are are the the only only energ energy y gener generat ating ing syst system ems, s, whic which h have have the the comb combin ined ed benef benefit itss of renewability , decentralization , and availability on demand without need for separate storage.
Taking into account the energy requirements of collection, processing and conversion to convert forms of that, biomass still assures a bright future from energy point of view.
Worldwide, biomass is the fourth largest energy resource after coal, oil, and natural gas. It is used for heating (such as wood stoves in homes and for process heat in bioprocessing industries), cooking (especially in many parts of the developing world), transportation (fuels production . such as ethanol) and, increasingly, for electric power production
Advantages
1. Biom Biomas asss is availa cheap ap,, widely widely avail availabl able, e, easy easy to available ble all all roun ound the the year year . It is che transport,store, and has no environmental hazards. hazards. 2. Biom Biomas asss-ba base sed d powe powerr gene genera rati tion on syst system ems, s, link linked ed to plan planta tati tion onss on wast wastel elan and, d,
simult simultaneo aneously usly addres addresss the vital vital issues issues of wastelands development development , environmental
4 restoration, restoration, rural employment generation and generati generation on of power power with no distribution
losses. 3. As a renewable fuel, biomass is used in nearly every corner of the developing world as a source of heat , particularly in the domestic sector. 4. Biomass is a versatile source of energy , which can be converted to ‘modern’ forms such
as liquid and gaseous fuels , electricity and process heat . 5. Bioenergy also permits operation at varying scales. For example, small-scale (5– 10 kW),
medium-scale (1–10 MW) and large-scale (about 50 MW) electricity generation systems or biogas plants of a few cubic meters (Indian and Chinese family plants for cooking) to several thousand cubic meters (Danish systems for heat and electricity). This variety of decentralized applications applications at the village level as scales is useful for power generation for decentralized national grids . well as for supply to the national 6. Modern biomass energy systems could be set up in virtually any location location where
plants can be grown or domestic
animals reared. Support from the government
Exploitation of the abundant biomass energy resources available in our country is being accorded a high priority by the MNES (Ministry of Non-conventional Energy Sources) . The implem implement entati ation on of projec projects ts is being being facili facilitat tated ed throug through h compreh comprehensi ensive ve program programmes mes by the minist ministry ry,, which which seeks seeks to create create a favorab favorable le policy policy enviro environme nment, nt, encourag encouragee technol technology ogy up gradation gradation and ensure market for the power generated. generated.
In pursuance of the national agriculture policy, a National Biomass Resource Atlas is boosting power generation generation form biomass biomass . The being prepared with the specific intention of boosting
national agriculture policy had called for increasing power generation from renewable sources
5 for meeting the needs of agriculture. The national Biomass Resource Assessment Programme has been assigned this task. According to a recent initial assessment made by the MNES about 500 million tonnes of biomass is generated every year from crop residues, bagasse, agro residue and forest sources. So far bagasse-based bagasse-based cogeneration cogeneration has achieved a capacity of 222 222 MW and
about 332 MW capacity is under installation.
SOLAR ENERGY
It is radiation from the Sun capable of producing heat, causing chemical reactions or generating generatin g electric electricity ity . The Sun is an extremely powerful energy source and solar radiation is by
far the largest source of energy recei received ved by the Earth, but its intensity at the Earth's surface is actually actual ly quite low. This is partly because the Earth Earth's 's atmosphere atmosphere and its clouds absorb or scatte scatter r as much as 54 percent of all incoming sunlight. Despite this, in the 20th century solar energy becamee increasingly attractive becam attractive as an energy source source owing to its inexhau inexhaustible stible supply and its nonpolluting character , which are in stark contrast to such fossi fossill-fuel fuel sources as coal, oil, and
natural gas.
percen centt vis visibl iblee lig light ht,, 45 The sun sunlig light ht tha thatt rea reaches ches the gro ground und con consis sists ts of near nearly ly 50 per percent percent inf infrare rared d radi radiatio ation n an ultravio aviolet let ligh light t an and d sm smal alle lerr am amoun ounts ts of ultr and d ot othe herr fo form rmss of electromagnetic electromagn etic radiation. This radiation can be converted either into thermal energy (heat) or
into electrical energy , though the former is easier to accomplish. Two main types of devices are used us ed to ca capt ptur uree so sola larr en ener ergy gy an and d co conv nver ertt it to th ther erma mall en ener ergy gy:: flat-plate collectors and concentrating concen trating collectors . Because the intensity of solar radiation at the Earth's surface is so low,
both types of collectors must be large in area. Even in sunny parts of the world's temperate regions, for instance, a collector must have a surface area of about 430 square feet (40 square m) to gather enough energy to serve one person for one day.
6 The most widely used flat-plate collectors consist of a blackened metal plate , covered with one or two sheets of glass that is heated by the sunlight falling on it. This heat is then transferred to air or to water, called carrier fluids, that flows past the back of the plate. Flat-plate hot-water -water heating and house heating . Fla collectors are commonly used for hot Flat-plat t-platee collec collectors tors
typically heat carrier fluids to temperatures ranging from 66° to 93° C (150° to 200° F) . The efficiency of such collectors ranges from 20 to 80 percent, depending on the design of the collector.
Satellite Solar-Power Solar-Power Systems
satellitee solar-powe solar-powerr system system (SS (SSPS) PS) is based The earth earth satellit based on technol technologi ogical cal advance advancess
stemming stemming from from the space space program. program. The concept concept involves involves the placement of earth satellites that would function as solar energy collecting stations in geostationary or synchronous orbits around the earth. Such orbits would be at an altitude of about 22,300mi (36,000 km) and would be equational, i.e., parallel to earth’s equational plane. The satellites would have large collectors of photo voltaic arrays. They would also have conversion systems that would convert the electric power power genera generated ted by the arrays arrays into into power power at micro microwave wave frequen frequencie cies. s. A large large transm transmitt itting ing antenna on each satellite would beam the microwave energy from its fixed position relative to the earth to a receiving station on the surface of the earth. That station would have a large receiving antenna that would reconvert the microwave power into ac electric power and feed into a conventional power transmission grid. The satellites, being so high above the earth, would be in sunlight most of most of the day, and no electric energy storage would be needed.
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The attitude controls of an SSPS, possible through use of laser technology, must see to it that the collector areas are constantly facing the sun and the transmitting antenna is constantly facing the receiving antenna on the earth. Still, the SSPS would have to pass through the earth’s shadow once a day, so that a complete cutoff of power from any one satellite is experienced about 5 percent of the time. A possible solution to this would consist of two geostationary o
satellites separated by about 7900mi(12,700 km) and thus about 20 out of phase, both having a direct line of sight to the same receiving antenna on earth. Such a system would ensure that one would be illuminated during the time the other is in the earth’s shadow. This would mean a 50 percent power cutoff during roughly 10 percent of the time, instead of a 100 percent cutoff during 5 percent of the time, and a possibly better match to loads demands. Additional satellites would even the power output further. further.
ENERGY FROM THE OCEANS Solar energy which may be used directly creates other forms of energy that can also be harnessed to generate power. One, the wind, is caused by the uneven solar heating and cooling of the earth’s crust combined with the rotation of the earth. Another is the result of the absorption of the seas and oceans of solar radiation, which causes, like the wind, ocean currents and moderate tempera temperatur turee gradie gradients nts from from the water water surface surface downwar downward, d, especi especially ally in tropic tropical al waters waters.. The
8 oceans and seas constitute some 70 percent of the earth’s surface area , so they represent a rather large storage reservoir of the solar input.
The temperature gradient can be utilized in a heat engine to generate power. This is called ocean temperature energy conversion conversion (OTEC). OTEC may be considered solar energy once
removed. Because the temperature difference is small, even in the tropics, OTEC systems have very low efficiencie efficienciess and consequently have very high capital costs.
Another source of energy in the oceans that can be exploited for power generation is the tides. Tides are primarily caused by lunar and only secondarily by solar , gravitational forces
acting together with those of the earth on the ocean waters to create tidal flows. These manifest themselves in the rise and fall of waters with ranges (height differences) that vary daily and seasonally and come at different times from day to day. They also vary widely from place to place, being as low as few centimeters but may exceed 8 to 10 m (25 to 30ft) in some parts of the world. The potential energy of the tides can be trapped to generate power, but at extremely high capital costs.As the seas and oceans of the earth constitute about 70 percent of its surface area, the total terrestrial solar energy incidence on them is immense, being equal to the total extra terrestrial solar energy received by the earth, which is about 1.516 E +18 Kwh/year or about 5.457 E+18 MJ/year , times an average clearness index of 0.5 times the fraction of area 0.7 or
about 0.53 E+18 kWh/year , or 1.9 E+18 MJ/year . This corresponds to an average terrestrial incidence on the waters of the solar constant S= 1353 W/sq.m x 0.5 = 676 W/sq.m. This energy is not totally absorbed by the water because some of it is reflected back to the sky. At an average water surface temperature of 20o C (680 F), the latent heat of vaporization is 2454kJ/kg and the sea water density is a little over 1000kg/m3. The annual energy absorbed would therefore be 1.20 x 1000 x 2454 , or about 3 x 10 6 kJ/m2 per year , which is equivalent to about 95W/m 2 or
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about 14 percent of the incidence . This figure varies, being a little higher than 100 W/m in the tropics to much less in arctic waters.
Lambert’ rt’ss law of Sola Solarr-ener -energy gy absor absorpt ptio ion n by the wate waterr takes takes place place accor accordi ding ng to Lambe absorption , which states that each layer of equal thickness absorbs the same fraction of light that
goes through it. In other words,
-dl(y)/d -dl(y)/dy y = µI (or) (or) I(y)= I(y)= Io e
-µy
where Io and I(y) are the intensities of radiation at the surface (y=0) and at a distance y below the -
surface. µ is an extinction coefficient ( also also called absorption coefficient) that has the unit length 1
-1
-1
. µ has values values of of 0.05m 0.05m for very clear fresh water, 0.27m fore turbid fresh water and 0.50 m
-1
for very salty water. Thus the intensity falls exponentially with depth and depending upon µ, almost all of the absorption occurs very close to the surface of deep waters. Because of heat and mass transfer at the surface itself, the maximum temperatures occur just below the surface.
Considering deep waters in general, the high temperatures are at the surface, whereas deep deep water water remai remains ns cool. cool. In the tropic tropics, s, the ocean ocean surfac surfacee temper temperatu ature re often often exceeds exceeds 25o C (77oF), while 1 km below the temperature is usually no higher than 10o C (50o F).Water density decre decreas ases es with with an increa increase se in temp temper erat atur uree ( above above 3.98 3.98o C, wher wheree pure pure wate water’ r’ss densi density ty is maximum, maximum, decreasing decreasing again below this temperature, temperature, the reason reason ice floats). floats). Thus there will be no thermal convection currents between the warmer, lighter water at the top and the deep cooler, heavier water.
It is said said,, ther theref efor ore, e, that that in tropi tropica call water waterss there there are are two two esse essent ntia ially lly infi infini nite te heat heat heat source source at the surface at about 27o C(81o F ) and a heat sink , some 1 km reservoirs, a heat
directly directly below, at about 4o C( 39 o F); both reservoirs are maintained annually by solar incidence.
10 The concept of ocean temperature energy conversion (OTEC) is based on the utilization of this temperature difference in a heat engine to generate power, a concept first recognized by the Frenchman d’Arsonval in 1881 . The maximum temperature difference on the earth is in the tropics and is about 15 o C (59 o F). Ocean currents carry the 27 to 28 o C warm tropical waters on a journey to the arctic circles during which they are gradually cooled to 4o C and maximum density. In the Arctic Circle they then settle below the surface, and a surface-deep water siphon is created that keeps cold water below the surface.
The surface temperatures (temperatures differences) vary both with latitude and season (refer figure above), both being maximum in tropical, subtropical, and equatorial waters, i.e., between the two tropics, making these waters the most suitable for OTEC systems.
The claims for OTEC systems are just as grandiose as those for most other renewable energy energy system systems. s. Withi Within n 800-km 800-km (500-m (500-mi) i) of that that path, path, the temper temperatu ature re differ difference encess between between surface and deep waters varies between 22o C (40 o F) and 15o C (27o F). Assuming a practical conversion conversion efficiency efficiency of 2 percent percent (below), (below), the Gulf Stream represents represents an annual power potential of 700 x 1012 kWh. An array of conversion plants moored on 1-mi (1.6-km) spacing along the length and breadth of that path would be capable of an annual 26 x 10 12 kWh. Such are the claims for OTEC, but practical and financial problems effectively preclude such dreams.
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GEOTHERMAL ENERGY
It is the pow power er ob obta tain ined ed by us using ing hea heatt fr from om th thee Ea Eart rth' h'ss in inte teri rior or.. Mo Most st ge geot othe herm rmal al resources are in regions of active volcanism . Hot springs, geysers, pools of boiling mud, and fumaroles (vents of volcanic gases and heated groundwater) are the most easily exploited sources of such energy. The greatest potential for geothermal energy, however, lies in the generation of electricity. Geothermal energy was first used to produce electric power at Larderello, Italy, in 1904 . By the late 20th century, geothermal power plants were in operation in Italy, New Zealand,
Japa Ja pan, n, Ic Icel elan and, d, Me Mexic xico, o, th thee Un Unit ited ed St Stat ates es,, an and d el else sewhe where re,, an and d ma many ny oth other erss we were re un under der construction in other countries.
The most useful geothermal resources are hot water and steam trapped in subsurface formations or reservoirs and having temperatures ranging from 176° to 662° F (80° to 350° C) . Water and steam hotter than 356° F (180° C) are the most easily exploited for electric-power generation and are utilized by most existing geothermal power plants. In these plants the hot water is flashed to steam, which is then used to drive a turbine whose mechanical energy is then converted to electricity by a generator. Hot, dry subsurface rocks may also become more widely used as a source of geothermal energy once the technical problems of circulating water through them th em for hea heati ting ng and co conv nver ersi sion on to st steam eam ar aree co comp mple lete tely ly re reso solv lved. ed. Th Thee de devel velop opme ment nt of geothermal resources has become increasingly attractive owing to the rising cost of petroleum and the non polluting character of geothermal energy production.
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REFERENCES
POWER POWER PLANT TECHNOLOGY TECHNOLOGY - EL Walki Walki : Mc Graw- Hill
NON CONVENTIONAL ENERGY RESOURES – G.D.Rai : Khanna Publishers
RENEWABLE RENEWABLE ENERGY RESOURCES RESOURCES - John Twidell Twidell & Toney
BIOMASS ENERGY IN ASEAN MEMBER COUNTRIES RWEDP/COGEN/ RWEDP/COGEN/AEEMTR AEEMTRC C Publication Publication,, JUNE 1997.
WWW.WEC.COM
WWW.GOOGLE.COM
