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.

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.

abstract: This thesis addresses the issue of making an economic case for bulk energy storage in the Arizona bulk power system. Pumped hydro energy storage (PHES) is used in this study. Bulk energy storage has often been suggested for large scale electric power systems in order to levelize load (store energy when it is inexpensive [energy demand is low] and discharge energy when it is expensive [energy demand is high]). It also has the potential to provide opportunities to avoid transmission and generation expansion, and provide for generation reserve margins. As the level of renewable energy resources increases, the uncertainty and variability of wind and solar resources may be improved by bulk energy storage technologies. For this study, the MATLab software platform is used, a mathematical based modeling language, optimization solvers (specifically Gurobi), and a power flow solver (PowerWorld) are used to simulate an economic dispatch problem that includes energy storage and transmission losses. A program is created which utilizes quadratic programming to analyze various cases using a 2010 summer peak load from the Arizona portion of the Western Electricity Coordinating Council (WECC) system. Actual data from industry are used in this test bed. In this thesis, the full capabilities of Gurobi are not utilized (e.g., integer variables, binary variables). However, the formulation shown here does create a platform such that future, more sophisticated modeling may readily be incorporated. The developed software is used to assess the Arizona test bed with a low level of energy storage to study how the storage power limit effects several optimization outputs such as the system wide operating costs. Large levels of energy storage are then added to see how high level energy storage affects peak shaving, load factor, and other system applications. Finally, various constraint relaxations are made to analyze why the applications tested eventually approach a constant value. This research illustrates the use of energy storage which helps minimize the system wide generator operating cost by "shaving" energy off of the peak demand. The thesis builds on the work of another recent researcher with the objectives of strengthening the assumptions used, checking the solutions obtained, utilizing higher level simulation languages to affirm results, and expanding the results and conclusions. One important point not fully discussed in the present thesis is the impact of efficiency in the pumped hydro cycle. The efficiency of the cycle for modern units is estimated at higher than 90%. Inclusion of pumped hydro losses is relegated to future work. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2014

abstract: With growing concern regarding environmental issues and the need for a more sustainable grid, power systems have seen a fast expansion of renewable resources in the last decade. The uncertainty and variability of renewable resources has posed new challenges on system operators. Due to its energy-shifting and fast-ramping capabilities, energy storage (ES) has been considered as an attractive solution to alleviate the increased renewable uncertainty and variability. In this dissertation, stochastic optimization is utilized to evaluate the benefit of bulk energy storage to facilitate the integration of high levels of renewable resources in transmission systems. A cost-benefit analysis is performed to study the cost-effectiveness of energy storage. A two-step approach is developed to analyze the effectiveness of using energy storage to provide ancillary services. Results show that as renewable penetrations increase, energy storage can effectively compensate for the variability and uncertainty in renewable energy and has increasing benefits to the system. With increased renewable penetrations, enhanced dispatch models are needed to efficiently operate energy storage. As existing approaches do not fully utilize the flexibility of energy storage, two approaches are developed in this dissertation to improve the operational strategy of energy storage. The first approach is developed using stochastic programming techniques. A stochastic unit commitment (UC) is solved to obtain schedules for energy storage with different renewable scenarios. Operating policies are then constructed using the solutions from the stochastic UC to efficiently operate energy storage across multiple time periods. The second approach is a policy function approach. By incorporating an offline analysis stage prior to the actual operating stage, the patterns between the system operating conditions and the optimal actions for energy storage are identified using a data mining model. The obtained data mining model is then used in real-time to provide enhancement to a deterministic economic dispatch model and improve the utilization of energy storage. Results show that the policy function approach outperforms a traditional approach where a schedule determined and fixed at a prior look-ahead stage is used. The policy function approach is also shown to have minimal added computational difficulty to the real-time market. / Dissertation/Thesis / Doctoral Dissertation Engineering 2016

abstract: This thesis addresses the issue of making an economic case for energy storage in power systems. Bulk energy storage has often been suggested for large scale electric power systems in order to levelize load; store energy when it is inexpensive and discharge energy when it is expensive; potentially defer transmission and generation expansion; and provide for generation reserve margins. As renewable energy resource penetration increases, the uncertainty and variability of wind and solar may be alleviated by bulk energy storage technologies. The quadratic programming function in MATLAB is used to simulate an economic dispatch that includes energy storage. A program is created that utilizes quadratic programming to analyze various cases using a 2010 summer peak load from the Arizona transmission system, part of the Western Electricity Coordinating Council (WECC). The MATLAB program is used first to test the Arizona test bed with a low level of energy storage to study how the storage power limit effects several optimization out-puts such as the system wide operating costs. Very high levels of energy storage are then added to see how high level energy storage affects peak shaving, load factor, and other system applications. Finally, various constraint relaxations are made to analyze why the applications tested eventually approach a constant value. This research illustrates the use of energy storage which helps minimize the system wide generator operating cost by "shaving" energy off of the peak demand. / Dissertation/Thesis / M.S. Electrical Engineering 2013

In the last decade, the power generation mix and the energy markets have been affected by the growing development of distributed and renewable energy sources.Nevertheless, a significant drawback of solar and wind energy is their intermittent and weather-dependent production, which often leads to a mismatch between renewable energy production and its use. Thus, the need for energy storage is recently emerging and becoming more relevant in this era of the energy transition. Among several technologies, today, pumped hydro energy storage (PHES) represents the largest share of the energy storage systems in the world. However, possible new investors, who might be attracted by potential profit in PHES, are repelled bythe long payback period and the scarcity of adequate site topology for such power plants. Relevant design decisions can be taken to reduce the costs and improve the performance or to escape the PHES topographical requirements. For this reason, the first part of this PhD thesis reviews and provides potential assessments of some unconventional PHES systems, applied in synergy with existing infrastructures. Such is the standpoint of micro facilities near waterway locks, or underground cavities used as lower reservoirs (UPSH), or the use of pump-turbines at variable geometryto cope with fluctuating loads.Moreover, important information on PHES in micro-scale is largely missing and their potential in distributed energy systems still needs to be unveiled. In the attempt to fill this gap, this thesis provides a techno-economic overview of the design and characterization of a first-of-its-kind PHES micro facility. In micro-scales hydropower projects, the initial capital cost of a conventional hydroelectric unit is hard to be determined and often economically prohibitive. Interestingly, in order to cut the total capital investment, the micro-PHES prototype runs with a single centrifugal pump for both pumping and generating phases and exploits existing stormwater reservoirs. The variable speed regulation is also implemented and it allows the pump to constantly operate at the maximum hydraulic efficiency in order to deal with load variations. In the same way, the pump working in reverse, namely pump as turbine (PaT), runs at the most suitable speed and it keeps a high efficiency over a wide load range. In addition, the analysis of the techno-economic parameters for such a system provides an important dataset for micro-PHES feasibility breakdown.PaTs are a legitimate cost-effective option in micro hydropower but an universal performance prediction does not exist. Their hydraulic efficiency can possibly shift from the higher efficiency of traditional hydraulic turbines. Nowadays, these reasons restrict PaTs exploitation. In this thesis, a multivariate regression method is applied to the CFD results to build a surrogate model of the PaT hydraulic characteristics as a function of the cutwater geometrical modifications. Based on this model, an optimization problem is solved to identify the most advantageous geometrical assetof the PaT cutwater to maximize the hydraulic efficiency. The presented methodology and design optimization of the cutwater in PaTs, which are extremely suited to our current energy generation needs, provides a unique and much-sought guide to its performance, improvements, and adaptation to hydropower. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

This thesis is divided in two sections. The first part consists of an interview study with 10 participants to investigate how the industry views the demand for energy storage and how it may develop in the future. Although some views differed, the study showed that a great responsibility lies on the existing hydropower. Batteries are believed to have the greatest potential as short-term storage. The participants agree that hydrogen could have great potential as a flexibility service. The future for Underground Pumped Hydro Energy Storage (UPHES) in Sweden have the participants divided but they seem to agree on the fact that the potential will depend on how price variations develop on the electricity market. Lastly, the industry agreed that a variety of energy storage technologies will be needed for the future energy system. The second part of the study is a deeper investigation into what energy deficit and demand for long-term energy storage (longer than 8 hours) might occur in the future and how UPHES may help shorten the longest deficits. To determine the need for energy storage, the scenario Electrification Renewable from a Svenska Kraftnät (Svk) report was chosen to represent the future energy system for year 2045. The result showed that depending on how the need for energy storage is defined, the amount of energy demand and therefore UPHES facilities, varied. If the need for energy storage was dimensioned regarding the average year it would result in 0,21 TWh of long-term energy deficits and 28 facilities would be enough to cover all of them. If the number of facilities was increased, the result showed a lower usage of all the facilities. However, if the need for energy storage was dimensioned regarding the ''worst case scenario'', the longest deficit out of 35 years, the energy demand in the long deficits was 14 TWh. If 28 facilities were used only 11 % of the energy demand in the long deficits would be covered. If the number of facilities increased, 172 facilities would cover 32 % of the energy demand in the long deficits and 1834 facilities would cover 60 %.

Environmental awareness and uncertainty about continued supply of fossil fuel has given rise to the renewable energy movement. Wind based power generation has been at the forefront of the motion to integrate distributed energy sources in the traditional power system. Due to various technical restrictions, wide scale penetration of wind generated power has been held back by most utilities. One such restriction is the variability of generation due to the technology’s dependence on Mother Nature. Energy storage devices can complement the wind generators by reducing this variability. These devices can store excess generation for supply during low generation periods. There are several promising technologies for both energy storage and power storage applications. Power storage devices provide short term fluctuation dampening capability while energy storage devices allow longer term storage. Pumped hydro, Vanadium Redox battery and Sodium-Sulphur battery are some of the viable energy storage technologies. This project provides a set of algorithms and guidelines to obtain the optimal configuration parameters of an energy storage device. To verify the efficiency of the algorithms, a model system has been obtained from a local utility. This system represents a typical radial distribution system in rural Ontario. The load demand, wind speed and energy prices for a period of one year have been obtained from utilities and Environment Canada. The main goal in determining the location of the storage device within a distribution system is to minimize the total cost of energy and the total energy loss during the period of analysis. Locating the storage device near the wind turbines or near the largest loads lead to the optimum results. Buses that are located near those elements can be considered as suitable locations for the storage device. The energy storage capacity and charge-discharge rate of the storage device are selected based on four criteria: maximize wind turbines’ load following capability, maximize capacity factors of the wind turbines, minimize system energy losses and minimize system energy costs. A weight based multi-objective optimization algorithm has been proposed to assign various priorities to these criteria and obtain a single solution. The larger the energy storage capacity of the storage device, the better the improvement in system performance. Lower charge-discharge ramp rates provide superior results. The parameters for storage device operating schedule, i.e. charge-discharge trigger levels, have been selected using similar criteria and weighted objective approach as for the capacity selection process. Higher charge trigger levels and moderate discharge trigger levels provide the optimum system performance. Once a set of parameters for the storage device has been selected, bus voltages over the period of study are analyzed. Voltage variations outside certain limits have been identified. Finally, a Monte Carlo based simulation approach is presented to obtain output parameter (system performance) variation ranges for pseudo random changes in input parameters.

Environmental awareness and uncertainty about continued supply of fossil fuel has given rise to the renewable energy movement. Wind based power generation has been at the forefront of the motion to integrate distributed energy sources in the traditional power system. Due to various technical restrictions, wide scale penetration of wind generated power has been held back by most utilities. One such restriction is the variability of generation due to the technology’s dependence on Mother Nature. Energy storage devices can complement the wind generators by reducing this variability. These devices can store excess generation for supply during low generation periods. There are several promising technologies for both energy storage and power storage applications. Power storage devices provide short term fluctuation dampening capability while energy storage devices allow longer term storage. Pumped hydro, Vanadium Redox battery and Sodium-Sulphur battery are some of the viable energy storage technologies. This project provides a set of algorithms and guidelines to obtain the optimal configuration parameters of an energy storage device. To verify the efficiency of the algorithms, a model system has been obtained from a local utility. This system represents a typical radial distribution system in rural Ontario. The load demand, wind speed and energy prices for a period of one year have been obtained from utilities and Environment Canada. The main goal in determining the location of the storage device within a distribution system is to minimize the total cost of energy and the total energy loss during the period of analysis. Locating the storage device near the wind turbines or near the largest loads lead to the optimum results. Buses that are located near those elements can be considered as suitable locations for the storage device. The energy storage capacity and charge-discharge rate of the storage device are selected based on four criteria: maximize wind turbines’ load following capability, maximize capacity factors of the wind turbines, minimize system energy losses and minimize system energy costs. A weight based multi-objective optimization algorithm has been proposed to assign various priorities to these criteria and obtain a single solution. The larger the energy storage capacity of the storage device, the better the improvement in system performance. Lower charge-discharge ramp rates provide superior results. The parameters for storage device operating schedule, i.e. charge-discharge trigger levels, have been selected using similar criteria and weighted objective approach as for the capacity selection process. Higher charge trigger levels and moderate discharge trigger levels provide the optimum system performance. Once a set of parameters for the storage device has been selected, bus voltages over the period of study are analyzed. Voltage variations outside certain limits have been identified. Finally, a Monte Carlo based simulation approach is presented to obtain output parameter (system performance) variation ranges for pseudo random changes in input parameters.

I det här examensarbetet dimensioneras en solcellsanläggning med batteribank till fyra kolonistugor som kommer att vara bebodda under sommarhalvåret på Wij Trädgårdar i Ockelbo. Den förväntade elanvändningen beräknas för två olika brukarbeteenden. Ett brukarbeteende där hushållsapparater med höga effekter (exempelvis mikrovågsugn) förväntas ha kortare drifttider vilket resulterar i lägre krav på installerad solcellseffekt samt en mindre batteribank.För den kemiska energilagringen i en batteribank undersöks flera olika typer av uppladdningsbara batterier. AGM blyackumulatorn är det batteri som anses vara lämpligt för kemisk energilagring i solcellssystemet och som har använts vid dimensioneringen av batteribanken. Vidare undersöks möjligheterna att lagra elektricitet småskaligt genom pumpat vatten till ett vattenmagasin, som ett komplement till energilagringen i batteribanken. Genom ett vattenlagringssystem kan överskottselen från solcellerna användas för att pumpa upp vatten till ett vattenmagasin på en högre höjd och därmed lagras genom lägesenergi. När det finns ett behov av elektricitet och den lagrade energin i batteribanken inte är tillräcklig kan vattnet flöda genom en vattenturbin som genererar el till batteribanken och lasterna. Ett vattenlagringssystem kan skydda batteribanken från djupare urladdningar, vilket kan öka batteriernas livslängd i form av antalet laddningscykler, samt ta tillvara överskottselen från solcellerna i större utsträckning. Batteribanken står för en stor del av inköpskostnaden och det finns både miljömässiga och ekonomiskt starka incitament att hitta sätt att förlänga batteribankens livslängd. / In this bachelor thesis is the size of a battery bank and the demand of photovoltaic power to supply electricity to four off-grid cottages calculated, which are occupied during the summer months at Wij Trädgårdar in Ockelbo. The expected electricity demand of the households is calculated for two different user patterns. In one of the user patterns the household appliances with a high power demand (for example microwave) are expected to have a shorter daily usage time, which results in a considerable lower purchase cost as a result from lower power demand of installed photovoltaic and a smaller battery bank. For the battery bank have different rechargeable batteries been investigated. The AGM Lead-Acid battery is found to be the most suitable rechargeable battery for chemical energy storage in this photovoltaic system. Furthermore the possibilities of pumping water to a water reservoir and store as potential energy as a complement to the energy storage in the battery bank have been investigated and discussed. Through a small-scale pumped hydro storage the surplus electricity from the photovoltaic can be used to pump up water to a reservoir at a higher altitude and be stored as potential energy. When there is a demand of electricity and the energy stored in the battery bank is not enough the water can be used in a small-scale water turbine, which generates electricity t the battery bank and the loads. A pumped hydro storage can protect the battery bank from deeper discharge, which otherwise can reduce the lifetime of the batteries, and extend the number of charge and discharge cycles the batteries can manage. The battery bank represents a large part of the purchase costs and there are strong environmental and economical incentives to prolong the lifetime of the battery bank.