Massive energy storage systems for the renewable green energy revolution

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Massive energy storage systems for the renewable green energy revolution

  1. 1. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME115MASSIVE ENERGY STORAGE SYSTEMS FOR THE RENEWABLEGREEN ENERGY REVOLUTIONSyed Bader Anwar,Associate Professor, EEE Department,Ayaan College of Engineering & Technology,Moinabad, R.R. Dist., A.P., India.Dr. Sardar Ali,Professor & Head - EEE Department,Royal Institute of Technology & Science,Chevella, R.R. Dist., Hyderabad, A.P., India.ABSTRACTMassive Energy Storage (MES) systems are the critical technology needed by the RenewableGreen Power Generation systems if they are to become a major source of readily accessible base loadpower, and hence eventually replace fossil/nuclear power plants. For system stability and loadlevelling, stored energy banks capable of releasing many megawatts of power quickly, and providingthis power over many hours, are needed to convert the intermittent and fluctuating renewable power,into electricity on demand.In this paper we present and compare the characteristics of most promising energy storagesystems and discuss their suitability for fluctuation smoothing, load leveling, improving powerquality, and reliability of supply and as uninterruptible emergency power sources.Key words: Massive Energy Storage, Green Power, Load levelling.I. INTRODUCTIONIn general, power or energy flow from a renewable resource is not constantly available, butdepends on weather conditions, or time of day, or season. Furthermore energy demand by humansocieties is also by no means invariant. So there needs to be a mediating technology between thesource and the consumer. This technology is energy storage which plays a very important role in allnatural and man-made processes.For years, the stumbling block for making renewable energy practical and dependable hasbeen how to store electricity for days when the sun isnt shining and the wind isnt blowing. But newtechnologies suggest this goal may finally be within reach. Renewable power can probably replacefossil / nuclear power, if enough wind farms, wave farms, and solar generators are built but costINTERNATIONAL JOURNAL OF ADVANCED RESEARCH INENGINEERING AND TECHNOLOGY (IJARET)ISSN 0976 - 6480 (Print)ISSN 0976 - 6499 (Online)Volume 4, Issue 3, April 2013, pp. 115-123© IAEME: www.iaeme.com/ijaret.aspJournal Impact Factor (2013): 5.8376 (Calculated by GISI)www.jifactor.comIJARET© I A E M E
  2. 2. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME116effective harnessing and storing of electrical power remains a major challenge to science, particularlywhen very large quantities of electrical energy are involved [1].Fig 1. A typical electrical power profile, showing the large variations during a 24-h period. In a loadleveling scenario, an electrical energy storage device would be charged during low-power demandperiods, and would discharge during high-power demand periods, thus filling in the valleys andlopping-off the peaks. A utility would need less overall power generation capability.Massive Energy Storage (MES) facilities, well dispersed, are likely to be an integral part ofpower supply systems geared to exploiting renewable resources. Without sufficient MES accessible atall times, solar/wind/wave power cannot serve as a stable base load supply; it can only serve as asmall incremental supplier. Hence MES must be recognised as a top priority critical technologydeserving sustained attention and support if a shift to renewable energy sources is to have any chanceof success.2. ENERGY STORAGE SYSTEMSIn this chapter we will consider and assess the practicability of several large scale energystorage systems, from pump storage commonly associated with hydroelectric schemes, throughcompressed air, flywheels, thermal storage, batteries, hydrogen, capacitors and superconductingmagnets.Pumped Water Energy Storage SystemPump storage is in essence a system for enhancing the operation of hydro-electric powerplants, by assisting nature in refilling the reservoir. In particular, it is applicable to those schemes thatoperate with more than one reservoir. In these circumstances, it becomes possible, at periods whendemand for power from the grid is low, to use excess generation capacity to move water from a lowerreservoir to a higher one, for future use when demand is high. Water is then released back into thelower reservoir through a turbine, generating electricity in exactly the same way as for a conventionalhydro-electric power station. A system of this description was first used in Italy and Switzerland inthe 1890s. Now, there is a large number of pumped storage systems in operation worldwide producingover 90 GW of power to the grid. This is about 3% of current global electrical generation capacity.
  3. 3. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME117Fig 1. Pumped Water Energy StoragePumped storage hydro-electric systems, like their conventional counterparts, use the potential energypossessed by water when it is raised against the force of gravity, the primary difference being thatmechanical intervention is employed to elevate the water. The potential energy density in stored wateris very low and therefore it requires either a very large body of water or a large variation in height toachieve substantial storage capacity, replenishing the reservoir through pumping, with the generatorsacting as motors and the turbines as pumps.If we follow through the full pumping/power-delivery cycle, from the power required toreplenish the stored energy (75% efficient), to the depletion of this energy in supplying consumers(70% efficient), almost 50% of the power generated disappears in electrical system losses. Even so,the economics of large scale electricity generation has determined that rapid and ready access tohydro-electric power justifies this wastage.The open sea can also be used as the lower reservoir in a pumped hydro-system. The firstseawater pumped hydro plant, with a capacity of 30 MW, was built in Japan, at Yanbaru, in 1999, andother schemes are being planned. Additionally pump storage has been proposed as one possible meansof balancing power fluctuations from very large scale Photovoltaic and Concentrated Solar Power(CSP) generation [2].Compressed Air Energy Storage (CAES)Air is an elastic medium, and when compressed it stores potential energy. Released air, ifexpanded in a controlled manner, can be used to power a gas turbine. Such a system, employing anunderground cavern to store the air was patented by Stal Laval in 1949. Since then two operationalplants have been completed and commissioned – one in Germany (Huntorf CAES) [3, 4] and anothermuch more recently in the USA (McIntosh CAES) [5].Fig 2. Compressed Air Energy Storage
  4. 4. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME118Very large storage volumes of the order of 500,000 m3with air at pressures in the range 7–8 MPahave been proposed to procure energy storage levels in excess of 500 MW-h. However, the onlypractical way of storing volumes of this magnitude is to use impermeable underground caverns atdepths of 700–800 m.An alternative approach to the storage problem, which is being investigated strenuously, is tostore high levels of energy in low weight, high speed flywheels, by employing advanced compositematerials to withstand the high stress levels.Fig 3. Flywheel Energy StorageFor electrical storage applications, the flywheel is typically housed in an evacuated chamber andconnected through a magnetic clutch to a motor/generator set out side the chamber. In turn, throughthe agency of some power electronics to stabilise frequency, the generator interacts with the local ornational grid. Potentially, tens of megawatts can be stored for minutes or hours using a flywheel farmapproach.In renewable energy storage terms, interest in flywheel technology is further boosted by otherkey features such as minimal maintenance, long life (at least 20 years or tens of thousands ofaccelerating /decelerating cycles), and environmental neutrality.If stored energy levels from flywheel farms can be lifted to 0.1 TJ or more, this storagemethod will be approaching a capacity that is of real significance to the problem of moderating andbalancing electricity supply, particularly when it becomes based wholly on renewables, as it hopefullywill, in the not too distant future.Thermal Energy Storage System(THES)Since in our present day economy, energy is produced and transferred as heat, the potentialfor thermal energy storage (THES) merits serious examination as a facilitator for a future economybased on renewables. Thermal energy storage generally involves storing energy by heating, melting orvaporising a material, with the energy being recoverable as heat by reversing the process [15].
  5. 5. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME119Fig 4. Thermal Enegy StorageStoring energy by simply raising the temperature of a substance is termed, rather curiously, sensible-heat storage. Its effectiveness depends on the specific heat (heat energy in joules per unit kilogram perdegree Kelvin above absolute zero) of the substance and, if volume restrictions exist, also on itsdensity.Storage by phase change, that is by changing a material from its solid to liquid hase, or fromliquid to vapour phase, with no change in temperature, is referred to as latent-heat storage. In this casethe specific heat of fusion and the specific heat of vaporisation, together with the phase changetemperature, are significant parameters in determining storage capacity.Battery Energy Storage System(BESS)In the electrical power industry, energy storage in batteries represents a well establishedtechnology. However it is a technology that is undergoing a renaissance after a forty yeardevelopmental plateau. This has been triggered by the renewables revolution, but has been facilitatedby developments in power electronics and control engineering, which means that highly sophisticatedbattery conditioning systems can be realised at moderate cost. Modern power electronic switchingprocesses also make it possible for a DC battery storage system to be easily and efficiently connectedinto the AC grid system.Fig 5. Battery Energy Storage SystemBatteries have several advantages over some other large scale storage systems. First, because of theiroutstanding power and voltage controllability, they are ideal for ensuring that the generated frequencyof a power station remains stable during demand surges by providing rapidly available back-up
  6. 6. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME120power. Second, they are very quiet and ecologically benign. Third, battery banks with a wide range ofcapacities can be readily constructed from factory-assembled modules. This offers storage flexibility,which does not exist with some other techniques. Finally, because battery banks can be assembled onrelatively compact sites, they can be located at or close to distribution substations, rather than at apower station. This offers the benefit of avoiding transmission losses in the grid.While weight for weight, or volume for volume, batteries tend to be the most compact ofelectrical energy storage media, transference of energy into and out of a battery generates rathersignificant levels of power loss.Hydrogen Energy Storage(HES)While hydrogen makes up 75% of the known matter in the universe, hydrogen is actuallyquite rare on Earth. Estimates suggest that in the surface layers of the planet, including the seas andoceans, the average concentration of elemental hydrogen is only 0.14%. Since it is quite reactive itexists on Earth only in combination with other elements such as oxygen in water, with carbon inmethane and with nitrogen in ammonia. As a result hydrogen gas is not a readily accessible energysource as are coal, oil and natural gas. It is bound up tightly within water molecules and hydrocarbonmolecules, and it takes high levels of energy to extract it and purify it. The gas is separated mainlyfrom natural gas, oil and coal with a small percentage (4%) obtained from the electrolysis of water.Fig 6. Hydrogen Energy StorageWater (H2O) is, not surprisingly, a very common source of hydrogen. It can be ‘split’ byelectrolysis, which is a process of decomposing water into hydrogen and oxygen by using electriccurrent. The technology is mature and is generally used where very pure hydrogen is required. Anelectrolysis cell comprises five main elements. First, the containment vessel, which is not unlike avery large battery, is filled with an aqueous electrolyte (usually a dilute solution of water andpotassium hydroxide). Second, an anode plate and a cathode plate are inserted into the electrolyte andare connected to an external electrical circuit, which drives current through the vessel. Hydrogen isformed at the cathode and the oxygen formed at the anode, so that these gases can be removedseparately. The electric current required is 40 kA for a cell voltage of 1.5 V.The most promising method for bulk storage of hydrogen produced from renewable energysources is the compressed form of the gas, which can be contained in underground caverns. Hydrogengas at 150 atmospheres (14.71 MPa) and at 20°C has an energy content of 1.7 GJ/m3 or 0.47 MW-h/m3. Consequently, a suitable rock cavern with a volume of just over 1000 m3 would be sufficient tostore a very useful 500 MW-h. CAES requires 500,000 m3 for a similar storage capacity.
  7. 7. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME121Capacitor Energy Storage Systems(CES)Large high voltage capacitors are used where significant amounts of electrical energy arerequired to be dissipated over very short time intervals, such as in testing insulators, for poweringpulsed lasers, in pulsed radar, and for energising particle accelerators. Few other electrical storagesystems can release, almost instantly, very high levels of power for a few microseconds ormilliseconds.Polar materials are slightly more promising in offering high permittivity from non-exoticcompounds. In such substances molecular dipoles are already present in the isolated, neutral, form.The most abundant of these is water, in which the H2O molecule is asymmetric. While each hydrogenatom is strongly bonded by sharing electrons covalently with the oxygen atom, the electron cloud ofthe molecule tends to favour the oxygen nucleus leaving the hydrogen nuclei exposed. Thus purewater has a high relative permittivity, tabulated as 81 for distilled water. However, this is still notenough to produce energy density levels that are significant in bulk storage terms.The remaining possibility is electrochemical capacitors. In this category electrolytics are themost well established embodiment. High capacitance is achieved in electrolytic capacitors byintroducing an electrolyte into the space between the metal electrodes. In this type of capacitor ions inthe electrolyte provide a mechanism for conduction current flow and the electrolyte can thus act asone of its plates. High capacitance is procured, not by employing a polarising effect in the electrolyte,but by separating it from the second plate by an extremely thin oxidised insulating layer on thiselectrode.Research into electrochemical capacitors (EC), which store electrical energy in two insulatinglayers when oxide coated electrodes are separated by an electrolyte (electric double layer, EDL),indicates that the separation distance over which the charge separation occurs can be reduced to a fewangstroms (1 angstrom = 0.1 nm). The capacitance and energy density of these devices is thousands oftimes larger than electrolytic capacitors.Superconducting Magnets Energy Storage System (SMES)When cooled to very low temperatures, some conductors are able to carry very high currents andhence high magnetic fields with zero resistance. Such materials are termed superconductors.Fig 7. Superconducting Magnet Energy StorageSuperconductivity occurs in a wide variety of materials, including simple elements like tin andaluminium, various metallic alloys and some heavily-doped semiconductors [46]. As an example of
  8. 8. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME122the superconducting temperature threshold, aluminium is superconducting below 1.175 K, which inCentigrade terms is –271.825°C. Superconductivity does not, however, occur in copper, nor in noblemetals like gold and silver, nor in most ferromagnetic metals.3. CONCLUSIONThe path from prototype development to full scale implementation of a technology is often aprecarious one, and Massive Energy Storage represents a technology that requires the solution ofvery complex scientific and engineering problems. Success in ‘rolling out’ this technology in theforeseeable future will take a very major commitment of manpower and funding, but decisions needto be made now. Finally, MES systems would undoubtedly provide substantial load-levelling andstabilisation potential for renewable power stations.REFERENCES[1] S. Fletcher, Bottled Lightening: Super batteries, Electric Cars, and the New Lithium Economy.New York: Hill and Wang, 2011.[2] Kurokawa, K., Energy from the Desert. http://www.ieapvps.org/[3] Herbst, G.E. et al., Huntorf 290MW Air Storage system Energy Transfer (ASSET) plantdesign, construction and commissioning. Proceedings of the Compressed Air EnergyStorageSymposium, NTIS, 1978.[4] Crotogino, F., Mohmeyer, K.-U. and Scharf, R. Huntorf CAES:More than 20 Years of Successful Operation.http://www.unisaarland.de/fak7/fze/AKE_Archiv/AKE2003H/AKE2003H_Vortraege/AKE2003H03c_Crotogino_ea_HuntorfCAES_CompressedAirEnergyStorage.pdf[5] Compressed air energy storage: history. http://www.ridgeenergystorage.com/caes_history.htm[6] Pickard, W.F., The History, Present State, and Future Prospects of Underground PumpedHydro for Massive Energy Storage, Proceedings of the IEEE, Feb, 2012[7] Ter-Gazarian, A., Energy Storage for Power Systems. Peter Peregrinus Ltd., 1994.[8] Katz, D.L. and Lady, E.R., Compressed Air Storage. Ulrich’s Books Inc., Ann Arbor, Michigan,1976.[9] Giramonti, A.J., Preliminary feasibility evaluation of compressed air storage power systems.United Technologies Research Centre Report, R76-952161-5, 1976.[10] Gill, J.D. and Hobson, M.J., Water compensated CAES cavern design. Proceedings of theCompressed Air Energy Storage Symposium, NTIS, 1978.[11] Renewable energy storage. Imech E Seminar Publication 2000-7, 2000.[12] Driga, M.D. and Oh, S.-J., Electromagnetically levitated flywheel energy storage system withvery low internal impedance. Pulsed Power Conference, 1997. Digest of Technical Papers, 11thIEEE International, 29 Jun–2 Jul 1997 Page(s):1560–1565 vol. 2, issue 1, 1997.[13] Williams, P.B., Practical application of energy flywheel. Modern Power Systems 4(5):59– 62,1984.[14] Grassie, J.C., Applied Mechanics for Engineers. Longmans, Green & Co. Ltd, London, 1960.[15] Kovach, E.G., Thermal energy storage. Report of the NATO Science Committee Conf.,Turnberry, Scotland. Pergammon Press, Oxford, 1976.[16] Olivier, D. and Andrews, S., Energy Storage Systems – Past, Present and Future. MacleanHunter House, Barnet, UK, 1989.[17] Wetterman, G. (ed.), Proceedings of the International Seminar on Thermochemical EnergyStorage, Royal Swedish Academy of Engineering Sciences, Stockholm, 1980.[18] Hart, A.B. and Webb, A.H., Electrical batteries for bulk energy storage. Central ElectricityResearch Labs., Report RD/L/R1902, 1975.[19] Talbot, J.R.W., The potential of electrochemical batteries for bulk energy storage in the CEGBsystem. Proceedings of International Conference on Energy Storage, Brighton, UK, 1981.
  9. 9. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME123[20] ABB-led Group to Build World’s Largest Battery Storage System; Global Power andTechnology. Business Wire, 29 October 2001.[22] Winter, C.-J. and Nitsch, J., Hydrogen as an Energy Carrier: Technology, Systems, Economy.Springer-Verlag, 1988.[23] Williams, L.O., Hydrogen Power. Pergamon Press, 1980.[24] Whittingham M. S., History, Evolution and Future Status of Energy Storage, Proceedings of theIEEE, May 2012[25] G.Ramachandran,T.MuthuManickam,B.SuganyaAbiramavalli,T.Sheela,ArunKumarMadhuvappan,L.Vasanth, “Study And Implementation Of Green Power In Campus Environment” InternationalJournal Of Electronics And Communication Engineering &Technology (IJECET) Volume 3, Issue 1,2012, pp. 325 - 331, ISSN PRINT : 0976- 6464, ISSN ONLINE : 0976 –6472.

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