abstract: The efficiency of spacecraft’s solar cells reduces over the course of their operation. Traditionally, they are configured to extract maximum power at the end of their life and not have a system which dynamically extracts the maximum power over their entire life. This work demonstrates the benefit of dynamic re-configuration of spacecraft’s solar arrays to access the full power available from the solar panels throughout their lifetime. This dynamic re-configuration is achieved using enhancement mode GaN devices as the switches due to their low Ron and small footprint. This work discusses hardware Implementation challenges and a prototype board is designed using components-off-the-shelf (COTS) to study the behavior of photovoltaic (PV) panels with different configurations of switches between 5 PV cells. The measurement results from the board proves the feasibility of the idea, showing the power improvements of having the switch structure. The measurement results are used to simulate a 1kW satellite system and understand practical trade-offs of this idea in actual satellite power systems. Additionally, this work also presents the implementation of CMOS controller integrated circuit (IC) in 0.18um technology. The CMOS controller IC includes switched-capacitor converters in open loop to provide the floating voltages required to drive the GaN switches. Each CMOS controller IC can drive 10 switches in series and parallel combination. Furthermore, the designed controller IC is expected to operate under 300MRad of total dose radiation, thus enabling the controller modules to be placed on the solar cell wings of the satellites. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2019

Photovoltaic Thermal/Hybrid collectors are an emerging technology that combines PV and solar thermal collectors by producing heat and electricity simultaneously. In this paper, thermal and electrical performance of PV/T collectors are analyzed and presented for the climate of RAK, UAE. Thermal performance evaluation is done following the collector output model presented in European standard EN 12975-2 and electrical performance evaluation is done by analyzing the effect of water circulation on the performance of PV/T collectors. Additionally, a PV/T system is designed for residential use in UAE and simulated using simulation software Polysun. Power output and requirements of the system along with its financial analysis is presented. Alternative solar energy systems to PV/T system are analyzed in terms of power output, specific requirements and financial analyses. Finally, a study is made to reveal the impact of incentives towards sustainable energy systems on the economic feasibility of PV/T systems for residential use in UAE. / <p>The project is done in cooperation with CSEM-uae under local supervision of Mr. Manoj Kumar Pokhrel.</p>

This thesis investigates the economic viability of a grid connected PV system integrated with battery storage in a multifamily home in Sweden. In addition, a fleet of electric cars is added to the system and its economic feasibility is analyzed. The analysis is further classified based on the roof area available for PV installation, wherein system 1 considers nearly the entire roof area of 908 m2 and system 2 is assumed to have less than half the roof area of 360 m2 for PV installation. To help with the assessment, five scenarios are created; where scenario one represents a baseline Swedish cooperative without PV, scenario two includes a PV system; scenario three incorporates battery storage; four considers an electric vehicle fleet embedded into the system and scenario five has a fleet of gasoline cars. These scenarios are applied to the two systems and their results compared. To address the question of this thesis both scenarios 2 and 3 are simulated in System Advisor Model (SAM) and scenario 4 is modeled in Matlab. The outputs are exported to Excel in order to obtain the Net Present Value (NPV), which is the economic indicator for this assessment. In none of the tested scenarios the NPVs’ are positive and the best result is observed in a PV system installed with battery storage in a roof area of 360 m2, which has a NPV of -82,000 SEK. A sensitivity analysis is done to assess the changes in NPV by varying the input parameters. It is concluded that battery storage is not yet economically viable in a Swedish multifamily house.

Solar cooling research center is being developed on CSEM-UAE outdoor research facility in RAK/UAE.  The research center is capable to test system from 1 TR cooling capacity to 10 TR cooling capacity. The source of heat is solar radiation and heat pipe type evacuated tube solar collectors are used to collect the solar energy. Solar station controls and circulates water in solar collectors and helps charge the hot water stratified tank. While in operation of the solar cooling facility, circulation pumps for hot water, chilled water and rejection circuit have to be continuously operated along with fan coil units, solar station, chiller and cooling tower. These all components require continuous electrical power. Currently, the entire electrical power requirement is supplied by a diesel generator. Since the center is for research activities, most of the time solar cooling center is on no load condition. Thus solar collectors are subjected to saturation. To prevent heat collection during no load conditions solar collectors are covered. Research project carried out to design of the renewable energy powered system to ensure the electricity availability for all the components so that the facility can be operated continuously without fossil fuel. UAE climate is sunny throughout the year thus Photovoltaic will be most prominent as a renewable source in generating electrical power. The PV is subjected to UAE harsh hot and dust environment which affect the performance of the PV. Thus the performance variations of PV due to dust deposition and temperature have analyzed. A matlab simulink model has developed to analyze the energy generation in UAE environment with available weather data. Technical and economical analysis has done for different PV technologies and find out the optimum PV design for the solar cooling center. To prevent the saturation of the solar collectors, a heat rejection unit have designed and installed. The control system for the automatic operation also implemented.

Bifacial solar modules can absorb and convert solar irradiance to current on both their front side and back side. Several elements affects the bifacial yield, especially the ground albedo around the system or the installation configuration. In this document, investigations carried out at EDF R&amp;D facilities regarding the use of bifacial modules in large scale PV farm are presented. Tests on the outdoor facilities were conducted to validate and improve a bifacial stand model developed under a Dymola/Modelica environement. Furthermore, a global optimization method was implemented to determine the optimal configuration of a large bifacial plant with modules facing south. Investigations showed the importance of a new albedo model to accurately evaluate the irradiance received on the rear side. The new model shows a relative error on the rear irradiance under 5% when compared with experimental data. Techno-economical optimization of a bifacial plant was conducted at different locations and for different ground albedo. The results shows that the gain on the specific production can vary between 7.2 and 14.2% for a bifacial plant when compared with a monofacial plant. Bifacial plants are expected to become more profitable than monofacial plants in some of the cases tested when their module cost will reach 68 c€/Wp.

The use of solar photovoltaic systems has increased in the past years in an effort to move towards cleaner energy sources. Solar panels are however affected by negative factors such as dust deposition which hinder their performance. The negative effects that dust deposition has on solar panels depend on how much dust gets deposited on solar panels and how it spreads on the top surface. The spread of dust on solar panels can be uniform where all the solar panels in a entire solar photovoltaic array have the same amount of dust deposition. This is an ideal case and can be defined as uniform dust deposition. However, in real life operation, the spread of dust deposition can vary with one solar panel having a different quantity of dust deposition from another. This is defined as non-uniform dust deposition. Non-uniform dust deposition negatively affects the performance of solar panels by reducing the irradiance that reaches the solar cells thereby reducing the performance of the solar panels. The negative effects of non-uniform dust deposition are more significant over time and when there is no intervention to remove the dust. In practice, the negative effects of non-uniform dust deposition on photovoltaic modules has been addressed by periodically cleaning their top surfaces. Periodic cleaning can however increase the operational costs in terms of the cleaning frequency, time taken, cost of cleaning resources and effectiveness. In this study, we propose an optimal cleaning strategy for the solar power plants that are prone to the non-uniform dust deposition. To develop the optimal cleaning strategy, we first investigate the dust deposition process and develop a model to describe the relationship between the solar power generation and non-uniform dust deposition patterns. Then we formulate an optimization model to identify the most cost-effective solar panel cleaning plan. In the optimisation, the additional revenue due to cleaning the solar panels is formulated as the objective function. The decision variables are the number of photovoltaic strings cleaned at each cleaning interval. To highlight the effectiveness of the proposed solar panels cleaning strategy, the developed cleaning strategy is applied to a case study where analysis of the performances of other solar panel cleaning strategies, namely “full cleaning”, “no cleaning” and “random cleaning” is done. The results from the study show that the optimal cleaning strategy outperforms all the other cleaning strategies showing its effectiveness. The optimal cleaning strategy developed is useful to solar photovoltaic plants owners whose plants are located in dusty or polluted areas. It first provides them with an understanding of non-uniform dust deposition. It also provides a way of reducing the effects of non-uniform dust deposition through optimized cleaning which is cost effective and that allows the photovoltaic array to continuously give the desired output. / Dissertation (MEng)--University of Pretoria, 2020. / Electrical, Electronic and Computer Engineering / MEng / Unrestricted

Over the last decade, General Purpose Graphics Processing Units (GPGPUs) have garnered a substantial attention in the research community due to their extensive thread-level parallelism. GPGPUs provide a remarkable performance improvement over Central Processing Units (CPUs), for highly parallel applications. However, GPGPUs typically achieve this extensive thread-level parallelism at the cost of a large power consumption. Consequently, Near-Threshold Computing (NTC) provides a promising opportunity for designing energy-efficient GPGPUs (NTC-GPUs). However, NTC-GPUs suffer from a crucial Process Variation (PV)-inflicted performance bottleneck, which is called Choke Point. Choke Point is defined as one or small group of gates which is affected by PV. Choke Point is capable of varying the path-delay of circuit and causing different forms of timing violation. In this work, a cross-layer design technique is proposed to tackle the performance impediments caused by choke points in NTC-GPUs.

Indiana University-Purdue University Indianapolis (IUPUI) / Combining rooftop solar with energy storage for off-grid residential operation is restrictively expensive. Historically, operating off-grid requires an 'isolated self-consumption' operating strategy where any excess generation is wasted and to ensure reliability you must install costly, polluting generators or a large amount of energy storage. With the advent of Blockchain technology residents can come together and establish transactive microgrids which have two possible operating strategies: Centralized Energy Sharing (CES) and Interconnected Energy Sharing (IES). The CES strategy proposes that all systems combine their photovoltaic (PV) generation and energy storage systems (ESS) to meet their loads. IES strategy establishes an energy trading system between stand-alone systems which allows buying energy when battery capacity is empty and selling energy when battery capacity is full. Transactive microgrids have been investigated analytically by several sources, none of which consider year-round off-grid operation. A simulation tool was developed through MATLAB for comparing the three operating strategies: isolated self-consumption, CES, and IES. This simulation tool could easily be incorporated into existing software such as HOMER. The effect of several variables on total cost was tested including interconnection type, initial charge, load variability, starting month, number of stand-alone systems, geographic location, and required reliability. It was found that the CES strategy improves initial cost by 7\% to 10\% compared to the baseline (isolated self-consumption) and IES cases in every simulation. The IES case consistently saved money compared to the baseline, just by a very small amount (less than 1\%). Initial charge was investigated for March, July, and November and was only found to have an effect in November. More research should be done to show the effect of initial charge for every month of the year. Load variability had inconsistent results between the two geographic locations studied, Indianapolis and San Antonio. This result would be improved with an improved load simulation which includes peak shifting. The number of systems did not have a demonstrable effect, giving the same cost whether there were 2 systems or 50 involved in the trading strategies. It may be that only one other system is necessary to receive the benefits from a transactive microgrid. Geographic locations studied (Indianapolis, Indiana; Phoenix, Arizona; Little Rock, Arkansas; and Erie, Pennsylvania) showed a large effect on the total cost with Phoenix being considerably cheaper than any other location and Erie having the highest cost. This result was expected due to each geographic location's load and solar radiation profiles. Required reliability showed a consistent and predictable effect with cost going down as the requirement relaxed and more hours of outage were allowed. In order to accomplish off-grid operation with favorable economics it is likely that a system will need to reduce its reliability requirement, adopt energy saving consumption habits, choose a favorable geographic location, and either establish a transactive microgrid or include secondary energy generation and/or storage.

To secure the growing energy demand due to the rise in population and technological advancements, countries worldwide are looking for alternatives or complementary generation sources to support the existing grid infrastructure and power generating system. The increase in global temperature and climate change forces each country to switch to clean energy production.  Among the renewable energy sources, the Floating Photovoltaic (FPV) market is flourishing in various countries. It is a good source of power generation avoiding land constraint issues and adding extra benefits like cooling of panels and reducing evaporation and algal bloom problems of water sources where it is installed. In fact, as a part of a complementary generation, the idea of using unused reservoir water surface of reservoir for the deployment of photovoltaic (PV) is a considerable solution for meeting energy demand.  As hydropower and PV are dispatchable and non-dispatchable sources of energy, they can complement each other well. The floating PV and hydropower basics and factors that complement their mutual operation are discussed in this research work with a literature review. Case studies of tropical and mediterranean climatic countries like Myanmar and Albania are analyzed using HOMER Pro. The various challenges associated with this hybrid hydro-floating PV project are evaluated using risk analysis, and the highest risk elements are identified.

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