Due to the rapid growth of grid-tied solar photovoltaic (PV) systems in the generation mix, the distribution grid will face complex operational challenges. High PV penetration can create overvoltages and voltage fluctuations in the network, which are major concerns for the grid operator. Traditional voltage control devices like switched capacitor banks or line voltage regulators can alleviate slow-moving fluctuations, but these devices need to operate more frequently than usual when PV generation fluctuates due to fast cloud movements. Such frequent operations will impact the life expectancy of these voltage control devices. Advanced PV inverter functionalities enable solar PV systems to provide reliable grid support through controlled real injection and/or reactive power compensation. This dissertation proposes a voltage regulation technique to mitigate probable impacts of high PV penetrations on the distribution voltage profile using smart inverter functionalities. A droop-based reactive power compensation method with active power curtailment is proposed, which uses the local voltage regulation at the inverter end. This technique is further augmented with very short-term PV generation forecasts. A hybrid forecasting algorithm is proposed here which is based on measurement-dependent dynamic modeling of PV systems using the Kalman Filter theory. Physical modeling of the PV system is utilized by this forecasting algorithm. Because of the rise in distributed PV systems, modeling of geographic dispersion is also addressed under PV system modeling. The proposed voltage regulation method is coordinated with existing voltage regulator operations to reduce required number of tap-change operations. Control settings of the voltage regulators are adjusted to achieve minimal number of tap-change operations within a predefined time window. Finally, integration of energy storage is studied to highlight the value of the proposed voltage regulation technique vis-à-vis increased solar energy use. / Ph. D.

The aim of the Thesis is theoretical clarification of the issues of photovoltaic power plants, their diagnostics, inspection and performance measurement, including negative impacts on their operation and subsequent application of theoretical knowledge during practical inspection and diagnostics of PV power plants. In its introductory part, the Thesis deals with design, manufacturing and development of PV cells and panels and describes other necessary elements and components, including their use in individual types of photovoltaic systems. Another part describes electric parameters of PV cells and panels, especially the parameters that can be found out by measurement of V-A characteristics and also the parameters affecting the shape of the V-A characteristics. The third part is focused on failures of photovoltaic systems, which include various defects of photovoltaic cells and panels, it also provides for adverse factors affecting operation of the entire system, associated not only with weather influences but also with the actual design of the photovoltaic system. The fourth part deals with possibilities of increasing the cost-effectiveness of electricity generation by PV power plants on the basis of practical experience of their operators. The subsequent part determines, on the basis of technical standards, procedures for PV power plant inspections, the procedures for measurement and diagnostics of PV power plants and also other prerequisites connected with inspections and measurements. This part includes also a description of requirements for measuring devices, most frequent measurement errors, adverse impacts affecting measurements and methods of assessment of the data measured. The last part of the Thesis is practical. At first it deals with verification of the impact of defects of PV modules on the shape of their V-A characteristics, then with execution of inspections and diagnostics of a particular PV power plant, evaluation of the data identified and measured, as well as with a proposal of optimisation measures to increase cost-efficiency of the operation of that particular PV power plant.

Utbyggnationen av solceller ökar exponentiellt både i Sverige och internationellt. En anledning till detta är sjunkande priser, mer effektiv teknik, skattereduktioner och andra ekonomiska incitament samt ett ökande intresse från bland annat elbolag. I många fall behövs fortfarande ekonomiska hjälpmedel som just skattereduktioner eller investeringsstöd för att PV-system (solcellsanläggningar) ska bli förmånliga. I den här fallstudien undersöks möjligheten att installera solceller på Västerberg folkhögskola i Storvik. Fastigheterna ägs av Region Gävleborg. Bionär Närvärme AB som är ett dotterbolag till Gävle Energi AB tillhandahåller värme till fastigheterna via en pelletspanna. På sommaren används el till pannan då värmebehovet är lågt och det finns ett intresse att producera sin egen el med hjälp av solceller. El för uppvärmning tas från skolans elabonnemang och därför dimensioneras PV-systemet mot hela elbehovet. Syftet var att först identifiera lämpliga tak, för att sedan finna den mest kostnadsoptimala storleken på ett PV-system för skolan. Därefter utfördes en simulering för att ta reda på årlig elproduktion och med hjälp av dessa resultat kunde ekonomiska förutsättningar beräknas. Lämpliga takytor valdes ut med avseende på orientering, lutning, storlek och placering av elcentraler. Kvantitativa data gällande fastigheterna och elanvändning samlades in. Därefter testades olika dimensioner på anläggningen i Winsun för att finna den storlek som gav kortast rak återbetalningstid. Sedan utfördes simulering av vald systemstorlek i PVsyst där årligt elutbyte presenterades som resultat. Med hjälp av givna och beräknade värden för elanvändning, solcellsproducerad el, egenanvänd el och överproducerad el (som säljs ut på elnätet) kunde en ekonomisk analys utföras. Resultatet visar att den anläggningsstorlek som ger kortast återbetalningstid är strax under 100 kWp. Efter simulering av valda takytor i PVsyst uppnåddes en toppeffekt på 94,6 kWp. Detta gav en återbetalningstid på 7,8 år. / The advancement of photovoltaic systems is growing exponentially both in Sweden and internationally. Reasons for this include decreasing prices, more efficient techniques, reduction in taxes as well as the increasing interest. In many cases, financial incentives like tax reductions or investment incentives are still necessary for photovoltaic systems to become profitable. In this case study, the possibility of installing a photovoltaic system at Västerberg folkhögskola in Storvik is examined. The properties are owned by Region Gävleborg. Bionär Närvärme AB, which is a subsidiary of Gävle Energi AB, provides the properties with heat through a pellet boiler system. In the summer however, electricity is used for the boiler when the heating requirement is less demanding, and there is an interest in producing electricity using solar cells. Since there is only one electricity subscription the PV-system is dimensioned with regards to the whole of the school’s electricity use including heating. The main purpose was to first identify suitable rooftops and then find the most costeffective size of a photovoltaic system for the school. Then, a simulation was performed to find out the annual electricity production and with the help of these results, an economic calculation could be determined. Suitable rooftops were selected with respect to orientation, angle, size and placement of distribution boxes. Quantitative data regarding the properties and electricity use were collected from Region Gävleborg. Subsequently, different photovoltaic system sizes were tested in Winsun to find the system size that yielded the shortest straight repayment time. Next, simulation of the selected system size was performed in PVsyst, where annual electricity exchange was presented as a result. An economic analysis could be carried out with the help of the values of electricity usage, solar-produced electricity, self-used electricity, over-produced electricity (which is sold to the power grid). The result shows that the system size that gives the shortest repayment time is just under 100 kWp. After simulation of selected rooftops in PVsyst, a peak power of 94.6 kWp was achieved. This gave a payback period of 7,8 years.

Skolfastigheter is a municipality owned real estate company that manages most of the buildings used for lower education in Uppsala. The company is working in line with the environmental goals of the municipality by installing photovoltaic systems in schools and other educational buildings. Skolfastigheter are planning to install a photovoltaic system in a school in Stenhagen. The purpose of this study is to optimally design the proposed system. The system will be maximized, which in this study entails that the modules will be placed on every part of the roof where the insolation is sufficient. The system will also be grid connected. The design process includes finding an optimal placement of the modules, matching them with a suitable inverter bank and evaluating the potential of a battery storage. Economic aspects such as taxes, subsidies and electricity prices are taken into account when the system is simulated and analyzed. A sensitivity analysis is carried out to evaluate how the capacity of a battery bank affects the self-consumption, self-sufficiency and cost of the system. It is concluded that the optimal system has a total peak power of almost 600 kW and a net present value of 826 TSEK, meaning that it would be a profitable investment. A battery bank is excluded from the optimal design, since increasing the capacity of the bank steadily decreased the net present value and only marginally increased the self-consumption and self-sufficiency of the system.

Submitted by Marco Antônio de Ramos Chagas (mchagas@ufv.br) on 2017-04-20T14:39:28Z No. of bitstreams: 1 texto completo.pdf: 260475 bytes, checksum: 75cd7fa15456edf29588849379577fad (MD5) / Made available in DSpace on 2017-04-20T14:39:28Z (GMT). No. of bitstreams: 1 texto completo.pdf: 260475 bytes, checksum: 75cd7fa15456edf29588849379577fad (MD5) Previous issue date: 2002-04-02 / Fundação de Amparo à Pesquisa do Estado de Minas Gerais / Conselheiros: Reginaldo da Silva Romeiro e Onkar Dev Dhingra. Sete meios semi-seletivos foram avaliados quanto à sua eficácia em permitir o crescimento de isolados de Xanthomonas axonopodis pv. phaseoli e suprimir o crescimento de contaminantes, objetivando selecionar um meio para utilização na rotina de laboratório. Foram utilizados 48 isolados da bactéria, provenientes de diferentes regiões do Brasil. Todos os meios semi- seletivos apresentaram boa eficiência em permitir o crescimento da bactéria quando preparados sem a adição dos compostos antimicrobianos presentes em suas composições originais. Quando da adição desses compostos aos meios, apenas o meio MXP modificado (M-MXP) não foi eficiente na recuperação da bactéria. Através de antibiogramas qualitativo e quantitativo respectivamente, os isolados do patógeno foram expostos a 43 compostos antimicrobianos, em diferentes concentrações. Foram selecionados sete compostos aos quais todos os isolados se mostraram insensíveis. Quatro destes compostos foram adicionados separadamente e em conjunto ao meio padrão (meio 523), em diferentes concentrações, e permitiram o crescimento de todos os isolados. Os meios semi-seletivos foram testados quanto à sua repressividade, utilizando- se, para tal, seis isolados representativos do total. Verificou-se que houve uma variação muito grande no valor do índice de repressão (IR) dos meios para cada isolado. Em alguns casos, os meios semi-seletivos permitiram maior desenvolvimento da bactéria que o meio padrão. Avaliando-se a supressividade, todos os meios semi-seletivos foram mais eficientes que o meio padrão em suprimir o crescimento de contaminantes associados a sementes de feijão nas duas amostras testadas. / Seven semi-selective media were evaluated for their efficiency to allow the growth of Xanthomonas axonopodis pv. phaseoli isolates and suppress the growth of contaminants, to select a medium for use in laboratory routine tests. Forty-eight isolates of the bacterium, collected from distinct geographic regions of Brazil, were used. All semi-selective media permitted the growth of all isolates when prepared without the antimicrobial compounds presented on their original formula. When these compounds were added to the media, only the modified MXP did not permitted growth. Using qualitative or quantitative antibiograms, the isolates were exposed to forty-three different antimicrobial compounds and in different concentrations. Seven of these compounds to which the isolates showed insensibility were selected. Four of these compounds were added separately or together to the standard (523 medium), in different concentrations, and tested for growth of all the isolates. The semi- selective media were tested for their repression, using six representative isolates. There was a very high variation in repressing index value of the different media for each isolate. In some cases, the semi-selective media allowed more growth of the bacteria than the standard medium. Evaluating the suppression, all semi-selective media were found to be more efficient than the standard medium for suppressing the growth of contaminants associated with two bean seed samples. / Dissertação importada do Alexandria

abstract: This is a two part thesis: Part – I This part of the thesis involves automation of statistical risk analysis of photovoltaic (PV) power plants. Statistical risk analysis on the field observed defects/failures in the PV power plants is usually carried out using a combination of several manual methods which are often laborious, time consuming and prone to human errors. In order to mitigate these issues, an automated statistical risk analysis (FMECA) is necessary. The automation developed and presented in this project generates about 20 different reliability risk plots in about 3-4 minutes without the need of several manual labor hours traditionally spent for these analyses. The primary focus of this project is to automatically generate Risk Priority Number (RPN) for each defect/failure based on two Excel spreadsheets: Defect spreadsheet; Degradation rate spreadsheet. Automation involves two major programs – one to calculate Global RPN (Sum of Performance RPN and Safety RPN) and the other to find the correlation of defects with I-V parameters’ degradations. Based on the generated RPN and other reliability plots, warranty claims for material defect and degradation rate may be made by the system owners. Part – II This part of the thesis involves the evaluation of Module Level Power Electronics (MLPE) which are commercially available and used by the industry. Reliability evaluations of any product typically involve pre-characterizations, many different accelerated stress tests and post-characterizations. Due to time constraints, this part of the project was limited to only pre-characterizations of about 100 MLPE units commercially available from 5 different manufacturers. Pre-characterizations involve testing MLPE units for rated efficiency, CEC efficiency, power factor and Harmonics (Vthd (%) and Ithd (%)). The pre-characterization test results can be used to validate manufacturer claims and to evaluate the product for compliance certification test standards. Pre-characterization results were compared for all MLPE units individually for all tested parameters listed above. The accelerated stress tests are ongoing and are not presented in this thesis. Based on the pre-characterizations presented in this report and post-characterizations performed after the stress tests, the pass/fail and time-to-failure analyses can be carried out by future researchers. / Dissertation/Thesis / Masters Thesis Engineering 2015

With the penetration of PV on the distribution system continually increasing, new advanced simulation methods are necessary to model the potential technical impacts of PV to the equipment and operation of the distribution system. With distributed PV, a timeseries analysis approach is necessary to more fully capture the time-varying nature of solar energy and the interaction with distribution system operations. The objective of the research is to streamline the PV interconnection process by providing more accurate methods that require less time for both the PV interconnection screening criteria and the PV interconnection impact study process. To improve the computational speed of timeseries simulations, an equivalent circuit reduction method is developed to simplify the circuit to a reduced-order model. The reduced circuit is equivalent during timeseries simulations, but it solves in a fraction of the time. The algorithm works with unbalanced multi-phase complex distribution system models, and it is shown to have high accuracy when validated against the full feeder models. An advanced PV hosting capacity simulation tool is developed and used to quantify system impacts for many PV interconnection scenarios, configurations, and locations, which can be generalized to develop improved future interconnection screening criteria. The advanced tools quantify location-specific impacts and the locational hosting capacity of potential PV interconnection locations on the feeder, including PV impact signatures and zones. A set of 50 different real distribution systems is analyzed in detail to demonstrate the range of scenarios and impacts that can occur depending on the feeder characteristics and topology. Specific methods are developed for time-series analysis, faster simulation times, distribution system equivalent circuit reduction, and PV hosting capacity analysis. The advancements presented in this thesis assist in streamlining PV interconnection studies with faster interconnection analysis times and more accurate screening criteria.

The energy sector is currently in a state of change as conventional energy sources are questioned by the need of new clean and sustainable energy sources to satisfy the global energy demand in the long term. Renewable energies respond to this increasing demand and solar energy is an advanced example of them. Photovoltaic modules are experiencing a steady reduction in their production costs. It is needed that this trend continues and, along with it, their propagation and expansion in the market continues. One way of reducing production costs is by using inexpensive light concentrators to increase the output of the costly photovoltaic cell. In this respect, the Solarus AB hybrid PV/T collector has been designed based on this principle. This collector is a CPC (Compound Parabolic Collector) and belongs to the MaReCo (Maximum Reflector Collector) family. The aim of this thesis is to deeply investigate this technology in two main areas. Firstly, the collector will be tested both electrically and thermally in order to evaluate its performance. To do so, a solar test rig has been built and connected at the building Hall 45 of Högskolan i Gävle, Gävle, Sweden. The second main area of investigation of this thesis is to determine the optimal price for the Solarus AB hybrid PV/T collector in order to be competitive in the solar energy market. This study will be based in the current market prices of photovoltaic and thermal collectors. Regarding the electrical performance of the collector, the results obtained show that the front side of the receiver produces more electricity throughout the day than the reflector side. This has guided Solarus AB to decide to change the design of its receiver to improve its performance. With the current design, it has been obtained a peak power at STC of 220W. In relation with the thermal part, the heat losses of the collector have been estimated obtaining a U value of 6,8W/(m2*K), a thermal optical beam efficiency of 63,5% and a total optical beam efficiency of 74,5%. The price market study of photovoltaic and thermal collector has shown that 2m2 of the Solarus AB hybrid PV/T collector produces approximately the same annual electricity and heat as 1,1m2 of a photovoltaic module with an efficiency of 15,5% and a flat plate collector of 0,85m2 of aperture area. According to the market study, its cost is equivalent to 190€ for the PV module and 220€ for the flat plate collector. This means that the price of the Solarus AB hybrid PV/T collector should be lower than 410€.

It is well known that the efficiency of a photovoltaic (PV) module is strongly impacted by its temperature such that higher temperatures lead to lower energy conversion efficiencies. An accurate measurement of the temperature de-rating effect, therefore, is vital to the correct interpretation of PV module performance under varied environmental conditions. The current work investigates and compares methods for performing measurements of module temperature both in the lab and in field-test environments. A comparison of several temperature measurement devices was made in order to establish the ideal sensor configuration for quantifying module operating temperature. Sensors were also placed in various locations along a string of up to eight photovoltaic modules to examine the variance in operating temperature with position in the string and within a larger array of strings.

Ethiopia has been facing problems regarding power generation, distribution, balancingbetween demand and supply and access to modern energy service. About 92.4% of energysupply is from biomass (mostly in traditional) 5.7% oil which is not friendly with theenvironment and about 1.6% of energy supply is from renewable energy resource,hydropower plants.Being dependent on hydropower plant causes the country to face many challenges indistribution and balancing demand and supply. This thesis provides another way ofconsidering and implementing renewable energy resource (solar energy resource) throughtechnologies like grid-connected roof mounted solar PV system and CSP plant with the helpof PVGIS, PVWatt and SAM software.This thesis aims to come up with an idea that will work out for current engineering, socialand political issue that is seen in the country. Considering new way in planting PV system onthe roof is strongly recommended and increasing the alternative sites for power generationalong with the appropriate technology is recommended as another way. The possibility andpower generating efficiency is checked through each application.Based on the demonstration in all software’s used, it is clearly visible that the country couldhave been satisfied the needed demand and become the hub of east Africa as mentioned inthe policy and strategy. However, this dependency causes the country to insufficiently supplythe need. Apart from the possibilities and estimation, ideas that might help the country tocome over these challenges are provided in recommendation section.