The development of artesian and pumped wells as a source of irrigation water has created the need for a measuring device which will be accurate for small discharges. The thin edged weir has been accepted as one of the most accurate and desirable measuring devices for this work. Three types of weirs are now commonly used: the Rectangular, the Cipolleti, and the Triangular Notch weir. Of these types the triangular notch is probably the best suited for small discharges (under 3 second feet). The various formulae for discharge over 90% Triangular weirs have been accurately determined for heads over two tenths of a foot. It is the purpose of this investigation to determine the coefficients for use in the general formula for discharge resulting from heads under 0.3 foot.

No description available.

Thesis (PhD (Physics))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The output power of end-pumped lasers is mainly limited by thermal effects in the bulk crystal gain material. The thermal effects either fracture the crystal or cause degradation in the laser beam quality and output power. This is especially pronounced in Nd:YVO4 and Nd:GdVO4 which exhibit strong thermal lensing. These two Nd3+ vanadate materials are of great value because of their high emission cross sections which makes them excellent gain materials for mode-locked, high repetition rate Q-switched and intra-cavity frequency doubled lasers. The two Nd3+ vanadates have very similar spectral properties but many publications claim that the more expensive Nd:GdVO4 is thermo-optically superior to Nd:YVO4. However, a debate ensued after theoretical calculations as well as measurements of the thermal conductivity and thermo-optical coefficients indicated that the opposite is true. To our knowledge there has never been a direct comparison of the thermal lensing of these two materials under identical pumping and lasing conditions. In order to contribute to the debate we did such measurements for different crystals of these two materials with equal low doping using three different measurement methods. We subsequently determined that Nd:YVO4 has slightly lower thermal lensing for the stronger gain -polarisation. One of the measurement methods we used is a novel more reproducible one that we developed for this purpose. It is more reproducible because it selectively measures only the focal length of the central, relatively unaberrated part of the thermal lens. Another measurement, utilising a probe beam through the laser crystal, found that there was almost no increase in the temperature when lasing is interrupted. This indicated that there is almost no upconversion present in the crystals which is probably due to their optimally chosen low doping. A further consequence of the vanadate debate is that there is still confusion about the value of the important thermo-optical coefficient for the higher gain -polarisation (dne/dT ) of Nd:YVO4. This parameter is of great importance in thermal calculations since the strength of the thermal lens is largely dependent on it. We therefore numerically modelled the thermal lensing in our crystals using different dne/dT values and found that the value given by Sato & Taira (2007) matches our experimental results the best. Our measurements also indicated that the thermal lens dioptric power increased nonlinearly with pump power. This appeared to contradict theory of thermal lensing since we knew that there was no upconversion in the crystals (which is the standard explanation for the nonlinear increase). We proceeded to use our numerical modelling to identify the main source of the nonlinear increase as the varying spectral output of the diode pump laser. The findings in this thesis therefore extend knowledge of the thermo-optical properties of the vanadates and increase understanding of the strongly aberrated thermal lenses formed inside them. Furthermore, the findings now enable the power-scaling of end-pumped vanadates lasers to higher levels. / AFRIKAANSE OPSOMMING: Die uitset drywing van longitudinale-gepompte vaste-toestand lasers word hoofsaaklik beperk deur termiese effekte in die laser kristal. Die kristal word of gekraak of die laser se bundel kwaliteit en uitset drywing verminder. Dit is veral ’n problem in Nd:YVO4 en Nd:GdVO4 kristalle waarin sterk termiese lense voorkom. Hierdie twee Nd3+ vanadaat kristalle is waardevol vanwee hulle ho¨e emissie deursnitte wat hulle uitstekend maak as versterkings materiale vir modus-gesinkroniseerde, ho¨e repitisie, Q-geskakelde en binne-resonator frekwensie-verdubbelde lasers. Die twee vanadate het baie soortgelyke spektrale eienskappe, maar verskeie publikasies beweer dat die duurder Nd:GdVO4 materiaal termo-opties beter is as Nd:YVO4. Onlangse teoretiese berekeninge asook metings van die termiese en termo-optiese kwaliteite van die twee kristalle toon egter die teenoorgestelde. Sover ons weet is daar nog geen direkte vergelyking van die termiese lens in hierdie twee materiale onder identiese kondisies gedoen nie. Ons het dus so ’n meting aangepak vir kristalle met identiese lae konsentrasie van die Nd3+ ioon deur drie verskillende meet metodes te gebruik. Een van die meet metodes is ’n nuwe, meer reproduseerbare metode wat ons ontwikkel het vir hierdie doel. Dit is meer reproduseerbaar omdat dit slegs die binneste deel van die termiese lens meet wat min sferiese aberrasie het. ’n Ander meeting, wat ’n toets-bundel deur die kristal stuur, het getoon dat daar byna geen verhoging in die die temperatuur van die kristal was toe ossilasie in die resonator onderbreek was nie. Dit is ’n aanduiding dat dat daar byna geen op-omskepping teenwoordig is in die kristalle nie wat te danke is aan hul optimale lae konsentrasie van die Nd3+ ioon. ’n Verdere gevolg van die debat is dat daar nog verwarring in die literatuur bestaan oor die waarde van Nd:YVO4 se termo-optiese dne/dT koeffisi¨ent. Hierdie parameter is van groot belang in berekinge van die termiese lens se fokale lengte vir die ho¨er wins -polarisasie. Deur numeriese modellering te gebruik het ons bevind dat die waarde wat verskaf word deur Sato & Taira (2007) ons eksperimentele data die beste pas. Ons metings het ook aangedui dat die dioptriese krag van die termiese lens nie linie¨er toeneem ten opsigte van die geabsorbeerde pomp krag nie. Dit was o¨enskynlik teenstryding met teorie oor termiese lense. Dit is omdat ons bevestig het dat daar geen op-omskepping in die kristalle teenwoordig was nie, wat die standaard verklaring vir die nie linie¨eriteit is. Ons het dus ons numeriese modellering gebruik om die hoofbron van die nie-lini¨ere toename te identifiseer as die veranderende spektrale uitset van die diode pomp laser. Die bevindings in hierdie tesis bou dus kennis op oor die termo-optiese eienskappe van die vanadate en versterk begrip van die sterk termiese lense binne hulle. Verder stel die bevindings ons nou in staat om die uitset drywing van longitudinale-gepompte vanadaat lasers na ho¨er vlakke te skaal.

Šios disertacijos tikslas – didelio tikslumo matuoklio, skirto šiluminio lęšio lazerių aktyviuosiuose elementuose matavimams sukūrimas, bei įvairių metodų, skirtų šiluminio lęšio įtakos mažinimui tyrimas. Matavimai buvo atliekami Shack‘o ir Hartmann‘o bangos fronto matuokliu, kuris buvo pritaikytas mažų skersinių matmenų (<1x1 mm) šiluminio lęšio matavimams. Pademonstruotas naujos konstrukcijos asferinis kompensatorius iš esmes mažinantis šiluminio lęšio aberacijų įtaką išilginio diodinio kaupinimo lazeriuose. Atlikti šiluminio lęšio aberacijų matavimai buvo panaudoti kompensatoriaus profilio skaičiavimams. Naudojant asferinį kompensatorių, pagamintą plonasienių dangų užgarinimo būdu, generacijos slenkstis sumažėjo daugiau kaip 3 kartus, taip pat ženkliai pagerėjo lazerio pluošto intensyvumo skirstinys. Darbe nagrinėjamas stiprinamų impulsų energijos didinimo būdas pasitelkiant eliptinę rezonatoriaus modą Yb:IAG lazeryje. Šis metodas leidžia kelis kartus padidinti stiprinamų impulsų energiją, išlaikant dirakciškai ribotus erdvinius pluošto parametrus. Taip pat, surasta lazerio rezonatoriaus konfigūracija, leidžianti palaikyti stipriai astigmatišką modą aktyviajame elemente, ir simetrišką modą lazerio išėjime. Pateikiami šiluminio lęšio matavimų rezultatai „atermalinės“ ir Ng orientacijos Yb:KGW kristaluose. Taip pat, parodėme, kad kristalo galų išsigaubimo įtaka Ng orientacijos Yb:KGW aktyviuosiuose elementuose gali siekti 50%. Atlikti tyrimai parodė, kad išbandyta... [toliau žr. visą tekstą] / In this thesis, analysis of thermal effects and various approaches for their mitigation in diode end pumped ultrafast lasers is presented. Experimental investigations were performed by employing Shack-Hartmann wavefront sensor which was adapted for measurements of thermal lens in diode end pumped lasers. During research, operation of high average power, diode-pumped, Nd:YVO4 laser with aspheric aberration corrector was investigated. Actual thermal lens measurements were conducted in order to design properly shaped aberration corrector that was manufactured using a thin film deposition technology. This allows us to conclude that employment of proper thermal lens aberration compensator allowed for laser threshold reducing and ensured improved output beam quality parameter M2 in wide pump power range. Prospects of output pulse energy scaling in diode end-pumped Yb:YAG laser by employing elliptical mode geometry was investigated. During our experiments, maximum average power in of ~ 5.5 W was obtained at repetition rates of 30-100 kHz, while in CW operation mode the 8 W output power was achieved. In spite of strongly astigmatic thermal lens due to optimized cavity design the output beam exhibits high spatial quality: beam quality parameter M2 in both vertical and horizontal plane was close to unity. Detailed comparative study of thermal effects in Yb doped KGW crystals with different orientation was performed. Measurements confirm, that anisotropic optical and thermal properties... [to full text]

In this thesis, analysis of thermal effects and various approaches for their mitigation in diode end pumped ultrafast lasers is presented. Experimental investigations were performed by employing Shack-Hartmann wavefront sensor which was adapted for measurements of thermal lens in diode end pumped lasers. During research, operation of high average power, diode-pumped, Nd:YVO4 laser with aspheric aberration corrector was investigated. Actual thermal lens measurements were conducted in order to design properly shaped aberration corrector that was manufactured using a thin film deposition technology. This allows us to conclude that employment of proper thermal lens aberration compensator allowed for laser threshold reducing and ensured improved output beam quality parameter M2 in wide pump power range. Prospects of output pulse energy scaling in diode end-pumped Yb:YAG laser by employing elliptical mode geometry was investigated. During our experiments, maximum average power in of ~ 5.5 W was obtained at repetition rates of 30-100 kHz, while in CW operation mode the 8 W output power was achieved. In spite of strongly astigmatic thermal lens due to optimized cavity design the output beam exhibits high spatial quality: beam quality parameter M2 in both vertical and horizontal plane was close to unity. Detailed comparative study of thermal effects in Yb doped KGW crystals with different orientation was performed. Measurements confirm, that anisotropic optical and thermal properties... [to full text] / Šios disertacijos tikslas – didelio tikslumo matuoklio, skirto šiluminio lęšio lazerių aktyviuosiuose elementuose matavimams sukūrimas, bei įvairių metodų, skirtų šiluminio lęšio įtakos mažinimui tyrimas. Matavimai buvo atliekami Shack‘o ir Hartmann‘o bangos fronto matuokliu, kuris buvo pritaikytas mažų skersinių matmenų (<1x1 mm) šiluminio lęšio matavimams. Pademonstruotas naujos konstrukcijos asferinis kompensatorius iš esmes mažinantis šiluminio lęšio aberacijų įtaką išilginio diodinio kaupinimo lazeriuose. Atlikti šiluminio lęšio aberacijų matavimai buvo panaudoti kompensatoriaus profilio skaičiavimams. Naudojant asferinį kompensatorių, pagamintą plonasienių dangų užgarinimo būdu, generacijos slenkstis sumažėjo daugiau kaip 3 kartus, taip pat ženkliai pagerėjo lazerio pluošto intensyvumo skirstinys. Darbe nagrinėjamas stiprinamų impulsų energijos didinimo būdas pasitelkiant eliptinę rezonatoriaus modą Yb:IAG lazeryje. Šis metodas leidžia kelis kartus padidinti stiprinamų impulsų energiją, išlaikant dirakciškai ribotus erdvinius pluošto parametrus. Taip pat, surasta lazerio rezonatoriaus konfigūracija, leidžianti palaikyti stipriai astigmatišką modą aktyviajame elemente, ir simetrišką modą lazerio išėjime. Pateikiami šiluminio lęšio matavimų rezultatai „atermalinės“ ir Ng orientacijos Yb:KGW kristaluose. Taip pat, parodėme, kad kristalo galų išsigaubimo įtaka Ng orientacijos Yb:KGW aktyviuosiuose elementuose gali siekti 50%. Atlikti tyrimai parodė, kad išbandyta... [toliau žr. visą tekstą]

This report covers the work carried out to redesign the two existing conventional hydro power stations in Zambia on the Kafue river into the pumped storage facility with solar photovoltaic power so that security of supply and water conservation is achieved to reduce the power deficits during the dry and drought periods. The two stations are Kafue gorge upper power station (KGUPS) and Kafue gorge lower power station (KGLPS) with an installed capacity of 990 MW and 750 MW respectively. These two stations are dammed hydro power station with the reservoirs size of 785 106 m3 and 80 106 m3 respectively and situated on the 9000 hectares of land with the net head of 400 m. The two plants are situated 15 kilometres apart and the water inflow in the KGUPS is dependent on the water release from the holding dam Ithezi- thezi (ITT dam) situated 220 kilometres from the KGUPS dam. The work covered the sizing of the storage dams and determining the autonomy days needed in order to keep the station (KGUPS) running with minimal impact on power blackouts which were calculated at 5 days considering the size of the dam and the available energy. The financial calculation for the PV system was also carried out in this study except for the hydro system which was not carried out due to the time allocated to conduct this study. The proposed operation scheme for the two hydro stations and the solar PV system is also carried out in order to increase solar power penetration in the Zambian grid, reduce power deficit and conserve water during the days/times with enough solar power.   Designing of the system was carried out using Homer Pro software on which the hydro power station was modelled using the water influx into the turbines at KGUPS, the plant net head of 400 meters was also used with the calculated head losses of 7 % for the 4 meter diameter penstock between KGUPS dam, KGUPS machine hall to the KGLPS dam. The KGUPS dam was modelled as a natural battery so that charging is done using the water from the KGLPS dam, the battery with a total annual capacity of 428 GWh was modelled. PVsyst and PVGIS software tools were also used to simulate the production from the optimised PV system so that the accuracy of tools can be compared.   To cover the load of 777 MW/day (18.6 GWh/day), the available power to provide the necessary energy for the pumps was 270 MW as surplus power from the hydro power machines at KGUPS .The available power from solar PV plant of 236 MW maximum was achieved from the optimized 300 MW PV plant in the dry period of the day which occurs in the month of October, with 300 MW converter , 8 % penetration of solar into the Zambian grid and the pumping scheme was able to provide 589 hours of autonomy with 80 % average state of charge. The total maximum power of 390 MW was good enough to provide power to the two pumps of each 165 MW. From the simulations carried out in the increment of solar PV system from 50 MW to 350 MW, the reliance on hydro power can be reduced drastically and power deficits due to the drought situation as the case for the year 2016 can be alleviated. 300 MW PV plant was selected in order to match with the available land, machines to work as pumps and the initial investment cost to be loosely monitored. The optimized 300 MW PV system with the life of 30 years had a project capital cost of $113 million united states dollars with the levelized cost of electricity 0.0487 $/kWh. The solar PV plant has a payback period of 9 years considering the yearly production from solar PV of 534 GWh as simulated from Homer, PVGIS interactive tool gave an output of 491 GWh. Pumped hydro systems has the capability of utilizing the already existing structures like dams and turbines. They also have the capability of stabilizing the grid network and allow easy penetration of renewable energy technologies like wind and solar. With the government of Zambia pushing for more renewables in the grid by 2030, a pumped hydro project at KGUPS will certainly be able to stabilize the grid and provide a scheme that will be able to push thermal plants to run at full capacity and the efficiency can be improved. In accordance with the IEC TC (technical committee) [30] pumped hydro energy storage is a mature bulk energy technology offering stability and allowing the penetration of intermittent renewables like wind and solar.

Este trabalho propõe a análise de curtos-circuitos trifásicos em geradores de indução duplamente alimentados (DFIG Doubly Fed Induction Generator). Os DFIGs voltam à pauta de hidrogeração devido aos recentes investimentos em usinas hidrelétricas reversíveis com velocidade variáveis empregando DFIGs. Esta configuração de geração, que permite velocidade do eixo diferente da frequência da rede, também é uma opção para usinas hidrelétricas convencionais, trazendo benefícios em termos de eficiência energética, estabilidade e otimização do sistema de potência. As pesquisas envolvendo este tipo de gerador tem se concentrado em aplicações para energia eólica. Os estudos são focados em aspectos de controle e otimização da geração não havendo muitos trabalhos voltados ao estudo de curto-circuito do ponto de vista da máquina principalmente relativos à solução analítica. Os trabalhos voltados a transitórios tratam em geral de afundamentos de tensão na linha de transmissão e metodologias para manter o gerador conectado ao sistema durante estes transitórios. Na área de hidrogeração, na maioria dos casos, os estudos tratam de aspectos de controle, de otimização da operação e de ganhos para o sistema de potência quando do uso do DFIG. Assim, faz-se necessário aumentar a gama de estudos do comportamento desses geradores frente a transientes elétricos, mais especificamente a curtos-circuitos. Para o estudo de transientes do curto-circuito trifásico foi desenvolvida a solução analítica e um modelo baseado no proposto por Krause (KRAUSE, 2002) para simulação em Simulink do Matlab para comparação de resultados. / This work proposes the analysis of three-phase short circuit on doubly fed induction generator, DFIG. This generator is again a subject of study for hydrogeneration as per recent investments on variable-speed Pumped Storage Power Plants. This configuration, which allows asynchronous shaft speed, is also an alternative for conventional hydro power plants, providing improvements on energy efficiency and stability and optimization of power system. Current studies on this subject are focused on wind power applications, covering mostly control and generation optimization aspects while there aren\'t so many studies on short-circuit especially with analytical solution. Electrical transient studies are usually covering voltage dips or sags on transmission line and associated methods to maintain power unit connected to power system during such. The researches on hydro power are also about control, operational optimization and power system improvements when DFIGs are installed. Thus, it is necessary to contribute to research regarding behavior of such generators under electrical transient conditions, more specifically under short circuits. The analytical equation for three-phase short circuit was developed as well the electric model based on the one proposed by Krause (KRAUSE, 2002) for simulations on Simulink of Matlab.

SAMMANFATTNING Medvetenhet och oro kring miljöeffekter från utsläpp av växthusgaser och de minskande resurserna av icke förnybara energikällor har ökat de senaste årtiondena. Utvecklingen av ny teknologi för förnybar energi har drivits fram globalt som ett svar på denna oro. Det har skett stora framsteg i produktion av el och värme från sol, vind, hav, vattenkraft, biomassa, geotermiska resurser, biobränslen och väte. Följaktligen har utvecklingen av energi-lager blivit en viktig del för integration av förnybar energi i systemen. Det är gynnsamt för hela försörjningskedjan, för pålitlighet och bättre stabilitet i leveranser och distribution, och för ökad el-kvalitet. I uppsatsen undersöks en optimal energidesign för ett kombinerat system med vattenkraft och vindkraft inklusive ett lager i form av en damm. Vatten som pumpas upp till lagret har en stor och balanserande potential för att få in en högre grad förnybar energi i energisystemen. Detta är nödvändigt då dessa energikällor är intermittenta och variabla till sin natur. Ett av de studerade objekten är ett vattenkraftverk med pumpad damm, Tehri i Uttarakhand, Indien. Systemets totala verkningsgrad om 93 % diskuteras utifrån förluster såväl som potentialen för vind och dess inverkan. Vind-data är hämta från National Institute of Wind Energy (NIWE) och har analyserats med programmen MATLAB och WindPro. Det slutligen valda området för exploatering av vindkraft blev Ramakkalmedu, Idukki district, Kerala, Indien. Efter valet av plats valdes tre olika vindturbiner ut för analys; Siemens SWT-3.2-113 3.2 MW, Enercon E-126 4.2MW, och Enercon E-126 7.58MW. Analysen består av flera delar; vindparks-modellering, beräkning av buller-generering från vindkraften, beräkning av årlig energi-generering - Annual Energy Production (AEP), kapacitetsfaktor, vindparkens effektivitet med hänsyn tagen till lagret/dammens variation av bas-last. Resultat har erhållits från alla tre turbinerna och den övergripande slutsatsen är att kombinationen med vatten- och vindkraft med lagring av vatten som pumpas upp vid behov är en tillfredsställande metod för att möta belastningstoppar, vilket valideras av denna uppsats.   Nyckelord: pumpade vattenkraftdammar, vindkraftparker, energi lager, förnybar energi. / ABSTRACT  Awareness and concern regarding the environmental effects of greenhouse gas emissions and depletion of non-renewable energy sources has increased over the last decades. A considerable development of new technology for renewable energy has occurred globally as an answer to this concern. There has been a major progress in production of electricity and heat generated from solar, wind, ocean, hydropower, biomass, geothermal resources, and biofuels and hydrogen. Consequently, the development of energy storages has become an imperative part, for integration of renewable energy. It is beneficial for the entire supply chain, for dependability and better stability, and for enhanced quality of electrical power. This thesis is exploring an optimal energy design for a system of pumped hydro-wind power plants including storage. Solutions with Pumped Hydro Storages have a great potential for their balancing role necessary for a higher degree of renewable energy sources, RES, in the energy systems because of the intermittent and variable nature of these sources. Tehri pumped hydro storage plant, in Uttarakhand, India is one of the objects studied in this thesis. The systems total efficiency of 93%, calculated from head losses, is discussed as well as wind potential and its impact. Wind data is obtained from National Institute of Wind Energy (NIWE) and analysed using the software tools MATLAB and WindPro. The finally chosen area explored for wind potential is Ramakkalmedu, Idukki district, Kerala, India. After selection of site within the area, three different turbines; Siemens SWT-3.2-113 3.2 MW, Enercon E-126 4.2MW, and Enercon E-126 7.58MW were considered for analysis. The analysis consists of several parts; Wind farm modelling, Noise estimation of Wind Park, estimation of Annual Energy Production (AEP), Capacity factor, Wind park efficiency with respect to the storage/reservoir´s base load variation. Results are achieved for all three turbines. The overall conclusion is that combined hydro and wind power with a pumped storage, is a satisfactory method for bulk energy store to address peak loads, which is validated by this thesis.   Keywords: Pumped Hydro, Wind farm, Energy Storage, Renewable Energy.

Este trabalho propõe a análise de curtos-circuitos trifásicos em geradores de indução duplamente alimentados (DFIG Doubly Fed Induction Generator). Os DFIGs voltam à pauta de hidrogeração devido aos recentes investimentos em usinas hidrelétricas reversíveis com velocidade variáveis empregando DFIGs. Esta configuração de geração, que permite velocidade do eixo diferente da frequência da rede, também é uma opção para usinas hidrelétricas convencionais, trazendo benefícios em termos de eficiência energética, estabilidade e otimização do sistema de potência. As pesquisas envolvendo este tipo de gerador tem se concentrado em aplicações para energia eólica. Os estudos são focados em aspectos de controle e otimização da geração não havendo muitos trabalhos voltados ao estudo de curto-circuito do ponto de vista da máquina principalmente relativos à solução analítica. Os trabalhos voltados a transitórios tratam em geral de afundamentos de tensão na linha de transmissão e metodologias para manter o gerador conectado ao sistema durante estes transitórios. Na área de hidrogeração, na maioria dos casos, os estudos tratam de aspectos de controle, de otimização da operação e de ganhos para o sistema de potência quando do uso do DFIG. Assim, faz-se necessário aumentar a gama de estudos do comportamento desses geradores frente a transientes elétricos, mais especificamente a curtos-circuitos. Para o estudo de transientes do curto-circuito trifásico foi desenvolvida a solução analítica e um modelo baseado no proposto por Krause (KRAUSE, 2002) para simulação em Simulink do Matlab para comparação de resultados. / This work proposes the analysis of three-phase short circuit on doubly fed induction generator, DFIG. This generator is again a subject of study for hydrogeneration as per recent investments on variable-speed Pumped Storage Power Plants. This configuration, which allows asynchronous shaft speed, is also an alternative for conventional hydro power plants, providing improvements on energy efficiency and stability and optimization of power system. Current studies on this subject are focused on wind power applications, covering mostly control and generation optimization aspects while there aren\'t so many studies on short-circuit especially with analytical solution. Electrical transient studies are usually covering voltage dips or sags on transmission line and associated methods to maintain power unit connected to power system during such. The researches on hydro power are also about control, operational optimization and power system improvements when DFIGs are installed. Thus, it is necessary to contribute to research regarding behavior of such generators under electrical transient conditions, more specifically under short circuits. The analytical equation for three-phase short circuit was developed as well the electric model based on the one proposed by Krause (KRAUSE, 2002) for simulations on Simulink of Matlab.

Memoria para optar al título de Ingeniero Civil Mecánico / De acuerdo a la necesidad de mitigar la variabilidad de producción de energía eléctrica mediante recursos renovables de naturaleza variable (energía solar y eólica), se analiza la factibilidad técnica de utilizar un sistema de almacenamiento de energía mediante bombeo de calor (Pumped Heat Energy Storage o PHES) utilizando CO2 como fluido de trabajo, lo que permite alcanzar altas eficiencias con bajo riesgo asociado al ciclo y un menor potencial de contaminación ambiental en comparación a otros fluidos de trabajo. El funcionamiento de un sistema PHES, consiste en el uso de bombas de calor para almacenar energía, en forma de calor (normalmente con sales fundidas tipo sal solar), a partir de superávit eléctrico, o bien en condiciones de bajo costo marginal en la red (alta generación de renovables - eólicas o fotovoltaicas). El calor almacenado es transformado nuevamente en energía eléctrica a través de un ciclo de potencia apropiado. Se establecen 6 distintas posibles configuraciones con distintos grados de viabilidad de acuerdo a tres factores: Las ventajas de utilizar el mismo fluido de trabajo en carga y descarga (Ciclo de descarga tipo Rankine de vapor o Brayton de CO2), la limitante tecnológica de la no existencia en el mercado de una turbina de CO2 apropiada (tipo de expansor en la bomba de calor: Turbina o válvula de expansión) y la limitante tecnológica-económica de los compresores de CO2 comerciales, los cuales no alcanzan temperaturas ideales para el uso de sales fundidas como medio de almacenamiento de calor (utilización o no de calentador eléctrico como complemento del compresor en la bomba de calor). Además se explora la posibilidad de utilizar 5 tipos distintos de sales fundidas, algunas de las cuales presentan potencial de ser producidas localmente. Se realizan modelos computacionales de cada configuración y se comparan eficiencias Round-Trip, eficiencia exergética de la bomba de calor y uso de sales fundidas principalmente. Se descartan combinaciones de sales fundidas con configuraciones que resultan inviables y se obtienen eficiencias Round-Trip entre 40 y 63% para aquellas viables, siendo la configuración con mayor eficiencia la con bomba de calor sin modificaciones y ciclo Rankine estándar (no considera restricciones), seguida por la configuración equivalente pero con calentador eléctrico (eficiencias 3-5% menores considerando restricción del compresor). Luego, las más prometedoras son aquellas con descarga Brayton, con eficiencias 4-7% inferiores que las con ciclo Rankine y presentando la posibilidad de utilizar los mismos equipos tanto en carga como descarga (ciclo Brayton reversible), aunque con mayores presiones de trabajo (asociado a mayores costos). Se considera necesario un estudio económico con mayor profundidad para determinar la conveniencia o no de este tipo de ciclos, así como también cuantificar las ventajas y desventaja de cada uno de los casos estudiados. Por último, de las 5 sales evaluadas, se detecta gran potencial en sales de litio (eficiencias 2-5% menores que sal solar con un requerimiento de flujo aproximadamente 40% menor) que podrían ser producidas en Chile dada la disponibilidad de materia prima.