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PV powered universities literature review

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Open-pv.png This page is part of an MTU graduate course MY5490/EE5490: Solar Photovoltaic Science and Engineering. Both the course documentation and the course generated content is open source. However, the course runs over Spring semesters during this time it is not open edit. Please leave comments using the discussion tab.


PV powered universities

Green Campus #x2014; Energy management system[1]

Abstract The aim of this paper is to describe and discuss about the main objectives and functions of the Energy Management System (EMS) of the Green Campus Smart Grid (GCSG). The main objectives of the Green Campus Smart Grid project are to realise fully functional smart grid (SG) environment, to demonstrate the functions of the smart grid and to function as a test platform for further smart grid related research. The EMS is responsible for controlling the smart grid devices and applications connected to the smart grid environment. By gathering the information from these devices to the EMS database, it can optimise the operation of the devices by accessing single database? and increase energy efficiency of the smart grid. The database also serves research purposes by offering access to long term data of the devices connected to the smart grid environment.

  • All of the data includes information about estimated load curves, stationary loads connected to the smart grid, priority of the loads, and weather forecasts are processed in Energy Management System

Design microgrid for a distribution network: A case study of the University of Queensland[2]

Abstract With more and more distributed generators (photovoltaic and wind) and distributed energy resources being integrated into power networks, traditional electricity grids may be replaced by smaller and more efficient grids called microgrids. Especially in recent years, there has been a significant increase in photovoltaic (PV) installations in Australia. As such, potential for microgrids to continue supply power to loads during a blackout was evident. However, microgrids have posed a concern for utilities as they do not provide utilities the same ability as the conventional grid to regulate microgrid voltage and frequency, and later possibly interfere with restoration of normal electricity supply. This paper investigates the feasibility of forming a microgrid in the University of Queensland for continuous electricity supply during power outage by utilizing its PV and storage systems. A simple but effective load shedding algorithm based on existing schemes and future technologies has been implemented. It also demonstrates how microgrid resynchronization can be achieved.

  • The intermittency of PV power supply may threaten microgrid integrity; therefore, in order to maintain system voltage and frequency within limits, loads are to be shed according to its priority
  • Under frequency load shedding works by disconnecting predefined loads when system frequency drops below a set threshold value
  • Genetic algorithm is used for load shedding and it fulfills all restrictions set by designer, minimizes disconnection of loads, and prevents disconnection of high priority loads
  • Smart buildings has enabled crucial information such as local real time electricity consumption and generation to be gathered; therefore, engineers will be able to make better decisions regarding switching of loads or changing power generation in real time
  • As soon as normal supply of power resumes, it is necessary for the microgrid to resynchronize with the main grid as microgrid operation in the long run is not sustainable
  • The most common closed loop method for resynchronization is the synchronously rotating frame phase locked loop
  • An effective load shedding algorithm is the key to maintaining microgrid integrity by ensuring balance between power supplied and demanded
  • As real power output from the PV arrays can not be controlled power mismatch may occur, and in order to count for power mismatch, a user defines apparent power safety margin and real power margin, and they are applied to the battery storage system
  • When utility supply return, the main circuit breaker cannot be closed instantly due to phase difference in voltage waveforms. Instead microgrid frequency is increased or decreased to minimize the phase difference

New experimental method for measuring power characteristics of photovoltaic cells at given light irradiation[3]

Abstract U-I characteristics - or electric power - as function of electrical voltage or current - of a solar panel (PV cell or panel) gives important information for developers, engineers and users. From this reason to get U-I plot or characterization of the electric power of a solar panel plays important role at the tests. In this paper a new and easy experimental method for U-I measurement (indirectly measured electric power data) for PV cells will be introduced. The new idea describes a simple, fast and reliable way how to get U-I characteristics - or power properties - of PV cells in a laboratory at a university using basic experimental tools.

  • In order to specify the optimum value of the operating point the maximum power output of the PV panel has to be determined at given and constant irradiation
  • One of the most general specific functions for description of a PV cell is the U-I (voltage-current) characteristics which belongs to given light irradiation
  • The mechanical holder for PV panels is called as adjustable measurement stand. The holder is a rotating and tilting mechanical stand, and rotation around the vertical axis is possible in 360 degree
  • The minimum azimuth angle is 30 degree and the maximum is around 90
  • In this article outlets for electrical signals of the PV tables are positioned in inner laboratory using cable connections, and for each PV panel a user friendly measurement place was designed and built on the laboratory wall. The measurement places give output voltage signals of the PVs through special inverters for the users, this way users can connect their meter and measure the voltage data

Distributed measurement system for long term monitoring of clouding effects on large PV plants[4]

Abstract A recording system for the generation of current-voltage characteristics of solar panels is presented. The system is intended for large area PV power plants. The recorded curves are used to optimize the energy output of PV power plants, which are likely to be influenced by passing clouds and periods of overcast skies.

Comparison of power generation from solar panel with various climate conditionand selection of best tilt angles in Ulaanbaatar[5]

Abstract The tilt angle of the photovoltaic (PV) array is the key to an optimum power generation. Solar panels or PV arrays are most efficient, when they are perpendicular to the sun's rays. Optimal tilt angle of solar panel are different at places of the earth. In Ulaanbaatar that is coldest capital city, the optimal tilt angle is 30 degrees in summer and 60 degrees in winter. By the calculation, the average tilt angle of the solar panel in Ulaanbaatar that can produce annually large amount energy is around 45 degrees. But 45 degrees of tilt angle are not so suitable due to snow and ice accumulation on the solar panel during winter in Ulaanbaatar.

A simple formula for estimating the optimum tilt angles of photovoltaic panels[6]

Abstract This paper presents a new approach to computing the optimal tilt angle for photovoltaic (PV) panels. The influence of cloudy conditions on the tilt angle is explored. It is demonstrated that more energy can be extracted from the PV system in cloudy conditions when the tilt angle of the panel is decreased compared to when the panel is aimed to be facing directly normal to the sun. Validation for fixed tilt, south-facing panels and for 2-axis tracking panels is presented by numerical simulations.

A simple formula for estimating the optimum tilt angles of photovoltaic panels[7]

Abstract This paper presents a new approach to computing the optimal tilt angle for photovoltaic (PV) panels. The influence of cloudy conditions on the tilt angle is explored. It is demonstrated that more energy can be extracted from the PV system in cloudy conditions when the tilt angle of the panel is decreased compared to when the panel is aimed to be facing directly normal to the sun. Validation for fixed tilt, south-facing panels and for 2-axis tracking panels is presented by numerical simulations.

  • It has been demonstrated that more energy can be extracted from the PV system in cloudy conditions when the tilt angel of the panel is decreased
  • The benefits of simplified formulas are that the tilt angels can be calculated based on historically known quantities, and there will be increased PV harvesting energy yield due to higher PV energy output in cloudy conditions

Measurement of spectral sensitivity of PV cells[8]

Abstract PV based large scale energy generation has spread significantly. In spite of similar technical parameters the amount of yearly produced energy may differ by notable percents. It results from the operation of solar trackers and also from the different spectral behavior of the different PV panel types. In this paper we introduce a novel on site spectral sensitivity measurement method. The spectral characteristic is recalculated from separate power maximum measurements, where the measurements are made by spectrally different natural irradiation (sunrise, noon, foggy, cloudy, etc.).

  • The efficiency of transformation of the infrared radiation into electricity is low. Also efficiency of the whole spectra is 6-7% of the amorphous cells, 15-17% of the crystalline cells

Fab Pitfalls with "Green Energy" at University and Government Campuses[9]

Abstract Many university and government campuses have rapidly expanding “Green Energy” programs. These programs often include a mix of solar photovoltaic power, wind power, fuel cells, and other low-carbon sources. Unfortunately, practical experience has shown serious problems with these sources powering sensitive fab tools. A better solution is to operate the fab tools from traditional utility-provided power, then use the “green” power to operate less-sensitive fab support equipment: chillers, CDA compressors, CDW pumps, and so forth. This less-sensitive equipment often consumes half or more of the entire fab energy budget, and is readily adaptable - with some small technical effort - to tolerate the power disturbances found on a “green” grid.

  • Practical experience has shown serious problems with renewable sources powering sensitive fab tools
  • Switching frequency of a DC/AC inverter in PV installation create a large level of noise which can significantly affect metrology tools
  • Green energy has a higher source impedance than utility energy which means that disruptive voltage sags tend to be deeper and longer

Forecasting of photovoltaic power yield using dynamic neural networks[10]

Abstract The importance of predicting the output power of Photovoltaic (PV) plants is crucial in modern power system applications. Predicting the power yield of a PV generation system helps the process of dispatching the power into a grid with improved efficiency in generation planning and operation. This work proposes the use of intelligent tools to forecast the real power output of PV units. These tools primarily comprise dynamic neural networks which are capable of time-series predictions with good reliability. This paper begins with a brief review of various methods of forecasting solar power reported in literature. Results of preliminary work on a 5kW PV panel at King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia, is presented. Focused Time Delay and Distributed Time Delay Neural Networks were used as a forecasting tool for this study and their performance was compared with each other.

Evaluation and verification of an intelligent control system with modelling of green energy devices by constructing a micro-grid system in university campus (report I)[11]

Abstract This paper presents a simulation model of green energy devices, which is developed for analyzing energy balance of a micro-grid and for optimizing its management. Several renewable energy based electricity production and storage are modeled and analyzed in the making of strategies for sustainable micro-grid management. In this study, two different simulation models are described, which call a “long-term simulation model”, and a “detailed short-term simulation model”. The first one is a high speed simulation model; it aims for prediction of the energy supply and demand balance of the micro-grid. In contrast, the second one is an accurate verification model; it use for detailed signal analysis of the devices and system. A case study, renewable energy model using photovoltaic, fuel cell, biomass and tidal power generation, is conducted and its simulation result is presented.

  • The home and building energy management system (HEMS and BEMS) has been growing in Japan, and it enables resident to save energy and lower electricity bill payment
  • The power supply emulator is software which runs on an emulation server, and is for copying the putput of a green energy device
  • The information of power consumption, power supply, and various environmental data is stored in the EMS database server
  • Based on the information and on prediction of power consumption and power supplies, EMS controls power generation systems and power consumption within possible limits
  • Efficiencies of DC/DC converters are higher than full-wave rectifier efficiency
  • The bidirectional DC/AC inverter controls the active power transferred from the DC bus to the AC bus

Centralized and modular architectures for photovoltaic panels with improved efficiency[12]

Abstract The most common type of photovoltaic (PV) installation in residential applications is the centralized architecture. This realization aggregates a number of solar panels into a single power converter for power processing. The performance of a centralized architecture is adversely affected when it is subject to partial shading effects due to clouds or surrounding obstacles, such as trees. An alternative modular approach can be implemented using several power converters with partial throughput power processing capability. This paper presents a detailed study of these two architectures for the same throughput power level. The study compares the overall efficiency of these two different topologies, using a set of rapidly-changing real solar irradiance data collected by the Solar Radiation Research Laboratory (SRRL) at the National Renewable Energy Laboratory (NREL). This provides an opportunity to study both schemes using real measured data. The output power of both the topology is compared against the panel ideal power. Hence, the efficiency is overall in nature. The electrical efficiency is another form of computation which uses the panel maximum available power as input instead of panel ideal power. The paper uses overall efficiency for all analysis. The buck converter along with the Perturb & Observe maximum power point tracking algorithm were selected to perform the study. A detail power loss analysis is also presented in the paper. Analytical results are validated through detailed computer simulations using the Matlab/Simulink mathematical software package.

Greenhouse gases emissions and energy payback of large photovoltaic power plants in the northeast united states[13]

Abstract The majority of large-scale solar farms have so far been constructed in the Southwest of the United States due to the intense insolation there. However, the high cost of electricity and the desire to increase the portion of renewables in the electric supply have generated interest in developing large-area plants in other areas. The environmental impact of building such large-scale solar farms in the northern United States has not yet been evaluated; we do so in this paper. This work discusses the life-cycle environmental impact from constructing and operating a 37-MWp solar-photovoltaic power-plant on the forested campus of Brookhaven National Laboratory, New York. We use the results from our assessments of its life-cycle emissions of greenhouse gases are then compared with those generated by similar plants in other regions to assess the net impacts of photovoltaics' life cycles in areas where trees are removed to accommodate the power plant.

  • Single axis solar panels made of multi crystalline silicon have an average efficiency of 13.5% and its total power is about 37MWdc
  • 10% of inverters' part must be replaced every 10 years
  • Photovoltaic would reduce at least 68% of the green house gases which would be emitted from the current electricity system

A green prison: The Santa Rita Jail campus microgrid[14]

Abstract A large microgrid project is nearing completion at Alameda County's twenty-two-year-old 45 ha 4,000-inmate Santa Rita Jail, about 70 km east of San Francisco. Often described as a green prison, it has a considerable installed base of distributed energy resources (DER) including an eight-year old 1.2 MW PV array, a five-year old 1 MW fuel cell with heat recovery, and considerable efficiency investments. Fig. 1 is an aerial depiction of the Jail with the PV rooftop modules clearly visible.

  • Round-trip losses are significant for NaS batteries, and 30 percent is the average here
  • In general, the battery is charged in the early morning hours and discharged during the following afternoon

A green campus project and advances in semiconductor nanostructures for photovoltaic applications[15]

Abstract We provide an overview of the various campus wide “Green” projects at the University of California, San Diego aiming for higher energy saving and efficiency for buildings and facilities. We present results on novel photovoltaic and photoelectrochemical cells based on semiconductor nanostructures, including compound semiconductor quantum wells and Si-based nanowires, for solar energy generation and storage.

  • The solar cell efficiency is improved 250 percent by SiNx surface passivation, and conformal ITO contact reduces the series resistance and improves the energy conversion efficiency about 5 times compared to bare Si p/n junction solar cells and about 2.3 times to that of SiNx passivated devices
  • The use of Ag mesh grid on ITO top contact reduces the series resistance and increase of efficiency
  • High quality Al2O3 passivation gives the best energy conversion efficiency

An innovative approach for determining PV cost convergence in the 25 Solar America Cities[16]

Abstract This presentation introduces the PV cost convergence calculator (PV CCC) developed under a contract supporting the U.S. Department of Energy's (DOE) Solar America Cities (SAC) program. The PV CCC is the first tool of its kind to provide a means to compare solar PV levelized costs and the timing of PV cost convergence with conventional energy sources for inter-city residential and commercial systems. The model reveals the specific impacts of various types of incentives on grid parity, and provides valuable input for strategic planning activities.

Large-scale photovoltaic solar power integration in transmission and distribution networks[17]

Abstract The province of Ontario in Canada has embarked on a major initiative to promote the grid interconnection of photovoltaic (PV) solar power systems. The Ontario Centres of Excellence, Centre of Energy, has recently approved a $6 million project for this purpose to a team of two Universities — University of Western Ontario and University of Waterloo, together with the support of four major industry partners who are involved in this technology in Ontario. A new technology has been developed for the utilization of PV solar farms in the nighttime and also during daytime as STATCOM. This paper will present the scope, objectives, research activities and commercialization potentials of this transformative project.

  • Large solar power plants can cause reverse power flow in the feeder transformers which results a transformer maloperation
  • Feeder losses can be reduced when properly sized and placed photovoltaic systems match the feeder peak load
  • Fluctuations can happen in the output power of photovoltaic systems by random variations of solar irradiance which is caused by environmental conditions
  • In order to predict the solar power that can be transmitted to the grid, real-time models of weather and metrological data are superimposed
  • For determining the wind load, solar panels need to be instrumented with pressure taps

Simulation and experimental study of shading effect on series and parallel connected photovoltaic PV modules[18]

Abstract Partial shading of photovoltaic modules is a widespread phenomenon in all kinds of Photovoltaic (PV) systems. In many cases the PV arrays get shadowed, completely or partially, by the passing clouds, neighboring buildings and towers, trees or the shadow of one solar array on the other, etc. This further leads to nonlinearities in characteristics. In this study, the simulation and experimental results of uniform and partial shading of PV modules are presented. Different shading pattern have been investigated on series and parallel connected photovoltaic module to find a configuration that is comparatively less susceptible to electrical mismatches due shadow problems. Simscape simulation model is employed to model the solar cell taking into account its series and parallel resistance.

  • The output characteristics of a PV module get more complicated if the entire array does not receive uniform insolation
  • A bypass diode can be added in parallel with solar cell in order to overcome the effects of partial shading
  • Shaded cells absorb power and act as a load which means that power is dissipated in shaded cells as heat and cause hot spots

Assessing the effect of variable atmospheric conditions on the performance of photovoltaic panels: A case study from the Vaal Triangle[19]

Abstract The purpose of this paper is to present a practical setup which is used to determine the availability of power from a singular stationary photovoltaic panel for variable atmospheric conditions in the Vaal Triangle, located in southern Gauteng, South Africa. Atmospheric conditions in this paper are characterized by air pollution and cloud movements, both which impact negatively on the operation of photovoltaic panels as shown by a number of scientific studies. Power regulation is achieved through the use of a DC-DC converter with a constant load resistance being employed to ensure reliability of the results for repeated measurements. The performance of the system is determined by considering the amount of time in which the DC-DC converter delivers power to the load resistance over a one week period, given as a percentage. Initial results indicate that the performance of this system varies by as much as 26% over a three month period stretching from March through May of 2011.

  • Cloudy conditions and air pollution prevent direct radiation, and they give rise to diffuse radiation which is not conductive to optimum PV performance
  • A major drawback of PV energy generation is the low power density and related to solar irradiation and low efficiency of the PV conversion
  • A 24 V DC/DC converter can be used to ensure a minimum voltage drop over the converter between its input and output
  • The on-time of the system can be determined with a normal probability plot in MS EXCEL using the Data Analysis Toolpak

An experimental investigation of the real time electrical characteristics of a PV panel for different atmospheric conditions in Islamic University of Technology (OIC), Gazipur, Bangladesh[20]

Abstract The electrical characteristics of a 60W, 12V PV panel is presented on this paper for geographical location of Latitude = 23° 43'N and Longitude = 90°25'E (Islamic University of Technology, Gazipur, Dhaka, Bangladesh). The open circuit voltage and short circuit current of the panel are measured and recorded at an interval of three minutes along with the total solar irradiation. The total solar irradiation is measured using the device “UNIKLIMA VARIO” commissioned in the automatic weather monitoring station of the university. Based on the weekly data voltage-times and current-time curves are plotted for three different seasons from which the total available electrical power curve is also derived. Then the electrical efficiency of the panel is calculated using the solar irradiation data. The objective is to observe the variation of efficiency for different weather and atmospheric condition. The voltage generated by a PV panel depends on the geographical location of the site, time of the year, time of the day and local weather condition. The geographical and climatic condition of the chosen site is suitable for PV power systems. The electrical design of the array is influenced by the factors such as- sun intensity, sun angle, load matching for maximum power and operating temperature of the panel. Based on the experiments it has been observed that with increased radiation, the panel current is increased linearly. With a constant irradiation, the output voltage of the panel is increased for a decrease in the panel temperature or vice-versa. Finally the efficiency curve for the three different seasons is plotted and according to the observed data a comparison is carried on based on different factors affecting the efficiency of the panel. The total energy output in kWh is also calculated using the power curve of the panel for three different seasonal variations.

  • The most important factor for designing any solar energy system is having the knowledge of quantity and quality of the solar energy at a specific location
  • The countries that are located within 3.200 km of the equator, the usage of sun's energy can be economically significant
  • The solar energy variations is related to the angle that the sun makes with a horizontal plane on the surface of the earth
  • The automatic weather station UNIKLIMA vario is used for storing the climatic data, controlling, and monitoring
  • When the cell temperature increases due to the increase in irradiation, the cell starts to operate at a lower efficiency; therefore, the efficiency of the cell is higher in the winters than summers

Analysis of the solar and wind resources for applications in hybrid systems in the Yucatan Peninsula[21]

Abstract The evaluation of PV-Wind hybrid systems under real field conditions is essential to predict their actual capacity to convert the energy available in the solar radiation and wind resources into electrical power. Therefore, detailed studies of these resources play a crucial role to estimate whether electricity can be generated at a reasonable cost for a specific region. The work presented in this paper shows the results of a study of Solar and Wind resources with the purpose of being applied in conjunction for reliable hybrid PV-Wind generators in the Yucatan Peninsula region. The study was undertaken at the Energy Laboratory of the Autonomous University of Yucatan located close to the north coast. Diurnal and seasonal variations were computed for each resource.

Optimal 24-hr utilization of a PV solar system as STATCOM (PV-STATCOM) in a distribution network[22]

Abstract This paper presents a novel optimal utilization of photovoltaic solar system as STATCOM for voltage regulation and power factor correction during both nighttime and daytime. The PV solar system conventionally generates real power during the day but the entire asset remains idle at night. This novel PV solar system operated as STATCOM is termed PV-STATCOM which utilizes the entire inverter capacity in the night and that remaining after real power generation during the day for accomplishing various STATCOM functionalities. Bluewater Power Corporation in Sarnia, Canada, is going to showcase this new concept of optimal utilization of PV solar system on a 10kW PV system in its network. The controller for the PV-STATCOM is being developed in the university lab and will be installed in the distribution utility network. A simulation model for the 10kW PV-STATCOM and the Bluewater Power distribution system network is developed in PSCAD software. This paper presents the steady state and transient performance of the PV-STATCOM controller for voltage regulation and power factor control both during nighttime and daytime. This proposed PV-STATCOM if connected at the terminals of an industrial customer having induction motor loads can help improve power factor and avoid potential penal tariffs over a 24-hour period, in addition to generating revenues due to sale of real power during the day.

  • A PV solar system inverter can be used as a STATCOM for voltage control and power factor correction
  • The simulation model for the controller can be built using PSCAD/EMTDC
  • The inverter is controlled in current-control mode, using the hysteresis band modulation technique

Photovoltaic module shading: Smart Grid impacts[23]

Abstract In the design of a solar photovoltaic system, one criterion that continues to receive low priority is the provision of minimum inter row spacing for photovoltaic modules. Consumers and installers alike strive to maximize area usage for systems such that they achieve the highest amount of annual energy output. This, in turn, leads to module rows being designed very close to each other; with array tilt lowered in an attempt to reduce inter row shading. This design practice fails to take into consideration many effects that close row spacing can have on system output. When designing a photovoltaic array to optimize its performance as a power generator and its contribution to the electric grid during peak demand periods - shading concerns become a key consideration. This paper describes a process developed at Rowan University's Center for Sustainable Design to test the impact that inter row shading can have on power output and performance across the day. A test rig and protocol were created which tested module's output given various depths of shading from one row of modules upon another. The exclusion of bypass diodes in the system was also tested to view the most extreme possible cases of power loss induced by shading. The results of this experimentation showed that even very small amounts of shading upon solar photovoltaic modules can lead to significant loss in power generation. As more PV systems are installed on the utility system their availability during peak times becomes an ever increasing requirement for Smart Grid success. This paper also explores the ramifications that proper inter row spacing design guidelines could have on reinforcing some of the fundamental principles of Smart Grid.

  • A significant loss of power will occur even if a very small amount of shading exist upon solar photovoltaic modules
  • Power output of modules can be maximized by optimization of the balance between maximum module density per area and minimum module shading
  • Intermittent sources have a greater potential for availability during summer peaking utility's peak demand period
  • By considering the altitude and azimuth angles of the sun at the design latitude and longitude, optimal row spacing can be determined
  • Bypass diodes can be used in the PV modules in order to reduce the amount of power that is wasted in the shaded area
  • Applying a bypass diode to each individual cell is not practical; therefore, the bypass diode is run in parallel to a series string of cells
  • Efficiency of a photovoltaic module begins to drop above a certain temperature, and efficiency losses could not be negligible if the temperature goes above 40 degrees of Celsius

Design and implementation of a 12 kW wind-solar distributed power and instrumentation system as an educational testbed for Electrical Engineering Technology students[24]

Abstract The main objective of this paper is to report and present design and implementation of a 12 kW solar-wind hybrid power station and associated wireless sensors and LabView based monitoring instrumentation systems to provide a teaching and research facility on renewable energy areas for students and faculty members in Electrical Engineering Technology (EET) programs at the University of Northern Iowa (UNI). This new ongoing project requires to purchase a 10 kW Bergey Excel-S wind turbine with a Power Sink II utility intertie module (208 V/240V AC, 60 Hz), eight BP SX175B 175W solar PhotoVoltaic (PV) panels, and related power and instrumentation/data acquisition hardware. A 100 ft long wind tower to house the new wind turbine is available at UNI campus. Furthermore, the electricity generated by this power station will be used as a renewable energy input for a smart grid based green house educational demonstration project to aid the teaching and research on smart grid and energy efficiency issues. 330:038 Introduction to Electrical Power/Machinery, 330:166 Adv Electrical Power Systems, 330:059/159 Wind Energy Applications in Iowa, 330:059/159 (2) Solar Energy Applications and Issues, and 330:186 Wind Energy Management are the classes that will use this proposed testbed. There are also workshops planned for the area Science, Technology, Engineering, and Mathematics (STEM) teachers as well as local farmers' education and training on wind and solar power systems. Previous workshops organized by UNI Continuing and Distance Education have been very successful. The hybrid unit contains two complete generating plants, a wind-turbine system and a PV solar-cell plant. These sources are connected and synchronized in parallel to the UNI power grid as part of laboratory activities on wind-solar hybrid power systems and grid-tie interactions. The proposed project is part of a program initiative to improve our laboratory facilities to better reflect on the current and future renewab- - le energy technologies. The proposed testbed will allow students to be educated and trained in the utilization of real-time electrical power systems and additionally will allow them to gain valuable “hand-on” experience in setting up a real-time data acquisition system specifically in grid-tied wind-solar power systems. Since Iowa's solar energy resources are higher in summer, this will provide an excellent complement to the load demand when summers are not windy.

  • The battery bank and diesel requirements is reduced by combining photovoltaic and wind in a hybrid energy system
  • Batteries lose 1 to 5 percent of their energy content per hour; therefore, they can store energy only for a short period of time
  • Various optimization techniques such as linear programming, dynamic programming and so on are used to design a hybrid system in a most cost effective way

Comparison of photovoltaic module performance at Pu'u Wa'a Wa'a[25]

Abstract: Hawaii is experiencing a substantial increase in grid-tied PV installations and utility companies are concerned with the resulting grid management issues. To address these concerns and to enable the utilities to make informed decisions, the Hawaii Natural Energy Institute (HNEI) of the University of Hawaii initiated a PV test program that provides high-resolution data to characterize module and array performance under a variety of local climatic conditions. In the first phase of the project HNEI developed a PV test bed located at Pu'u Wa'a Wa'a ranch on the Kona coast of the Big Island of Hawaii. Initially we selected seven different PV technologies for testing consisting of poly-crystalline, mono-crystalline, amorphous, and mixed technologies. The test modules comprise 200 W units, tilted at 20°, with maximum power point trackers, via small inverters connected to the grid or via charge controllers connected to a battery and load bank. The data is sampled at 1 Hz and stored in a database for visualization and analysis. This paper presents a description of the test bed design, the high data rate Data Acquisition System (DAS), and initial experimental results.

  • Performance of photovoltaic is dependent on the PV module's design, material, and environmental variables
  • If a portion of PV array or the entire array is covered with clouds then an immediate power loss will occur
  • The impact of mentioned power loss on the grid will be exacerbated if a sudden change in the load demand happens at the same time
  • The battery voltage needs to be maintained below its float voltage in order to reach MPP of the module
  • A graphical user interface is created under a Matlab environment in order to analyze and visualize data
  • MPPTs operation is more efficient with low voltage modules
  • Charge controllers show an average efficiency around 90 percent

Study of a standalone wind and solar PV power systems[26]

Abstract This study utilizes hourly average wind speed and hourly total global solar radiation data for the years 2007-2009 to study the energy yield from (i) a standalone wind power system of 6 kW rated capacity and (ii) a standalone 6 kW photovoltaic (PV) power system. These wind and PV power systems are installed in the campus of King Fahd University of Petroleum and Minerals at Dhahran, Saudi Arabia. The annual energy yields from standalone wind and solar PV power plants each of 6 kW installed capacity were found to be 8,000 kWh and 10,364 kWh with respective capacity factors of 14.3% and 19.7%. The propose wind turbine could displace 2 tons of greenhouse gases annually from entering in to the local atmosphere and the solar PV power plant could be able to reduce around 3 tons of these gases annually.

  • The RETScreen Clean Energy Project Analysis Software is used to calculate the energy that is yielded from wind and solar systems

improved photovoltaic energy output for cloudy conditions with a solar tracking system[27]

Abstract This work describes measurements of the solar irradiance made during cloudy periods in order to improve the amount of solar energy captured during such periods. It is well-known that 2-axis tracking, in which solar modules are pointed at the sun, improves the overall capture of solar energy by a given area of modules by 30–50% versus modules with a fixed tilt. On sunny days the direct sunshine accounts for up to 90% of the total solar energy, with the other 10% from diffuse (scattered) solar energy. However, during overcast conditions nearly all of the solar irradiance is diffuse radiation that is isotropically-distributed over the whole sky. An analysis of our data shows that during overcast conditions, tilting a solar module or sensor away from the zenith reduces the irradiance relative to a horizontal configuration, in which the sensor or module is pointed toward the zenith (horizontal module tilt), and thus receives the highest amount of this isotropically-distributed sky radiation. This observation led to an improved tracking algorithm in which a solar array would track the sun during cloud-free periods using 2-axis tracking, when the solar disk is visible, but go to a horizontal configuration when the sky becomes overcast. During cloudy periods we show that a horizontal module orientation increases the solar energy capture by nearly 50% compared to 2-axis solar tracking during the same period. Improving the harvesting of solar energy on cloudy days is important to using solar energy on a daily basis for fueling fuel-cell electric vehicles or charging extended-range electric vehicles because it improves the energy capture on the days with the lowest hydrogen generation, which in turn reduces the system size and cost.

  • Solar energy is a way to boost the future hydrogen economy via the electrolysis of water
  • The best configuration overall fixed configuration for PV installations is one in which the modules face south and are tilted with respect to the ground at an angle equal to the site latitude
  • The largest amount of solar energy can be obtained using a mechanical tracking system so that the modules are always facing the sun
  • Two axis solar tracking increases the solar insolation by over 50% relative to that for PV modules with fixed horizontal orientation, by 30% relative to PV modules with a fixed latitude tilt
  • For cloudy conditions, orienting solar modules toward the zenith captures the most solar energy

Energy cost calculations for a solar PV Home System[28]

Abstract Energy costing for a Solar Home System has been presented here considering the main cost components. It has been identified that the cost of solar PV panels, bank interest rate, cost of battery and its longevity plays the most important role in determining the energy cost. Average solar insolation is also taken into consideration and the results show that contribution of the storage battery towards the total cost of energy is significantly higher than that of the solar PV panel.

The PV grid-connected demonstration system of University #x201C;Politehnica #x201D; of Bucharest[29]

Abstract In 2006, at University Politehnica of Bucharest, in the framework of the European demonstration project PV-enlargement, and of the Romanian project ldquoPV gridrdquo, a rooftop grid-connected photovoltaic power generation system of 30 kWp has been installed. This is a double array PV system containing two kinds of silicon modules: crystalline and amorphous. The installed power of crystalline modules is of 27.36 kWp and that of amorphous modules is of 3.24 kWp. This paper gives a survey of amorphous silicon array performances during 12 representative working months under specific operational and environmental conditions of Bucharest geographical location.

  • A central data monitor which monitors the health of the entire system, collects the data from inverters about its operating parameters
  • The monitoring system is connected to a PC from which monitors operation of inverters, energy input and output, and historical file of the electric performances
  • Data acquisition system measures solar irradiation, module temperature, air temperature, power and energy produced of each inverter, and so on
  • Data are retrieved from the monitoring equipments at regular intervals of 10 minutes, and submitted immediately to quality control and data analysis through remote access via internet
  • The biggest temperature differences between panels and environment are in summer time, about 15 degree Celsius as average value

Cost boundaries for future PV solar cell modules[30]

Abstract Growth of the photovoltaic (PV) market is still constrained by high initial capital costs of PV. Developments in PV technologies may lead to cheaper systems at the likely expense of life expectancy and efficiency. Cost boundaries are required for future PV technologies to compete effectively within the current PV market. This paper develops a methodology based on life-cycle costing and sensitivity analysis to determine cost boundaries for new PV technologies. Amongst other comparisons with existing PV systems, the upper wattpeak cost bounds are estimated and the minimum economically viable replacement period is illustrated. Furthermore, future PV system ratings are compared to current PV systems for similar energy outputs. The results show that a price reduction factor greater than 5 is competitive for future solar cell lifetimes of less than 4-5 years. Meanwhile, future PV systems were, on balance, found to have higher ratings compared to current PV systems of similar energy outputs. The potential application of the model developed in this work is also discussed.

MATLAB-Based Modeling to Study the Effects of Partial Shading on PV Array Characteristics[31]

Abstract The performance of a photovoltaic (PV) array is affected by temperature, solar insolation, shading, and array configuration. Often, the PV arrays get shadowed, completely or partially, by the passing clouds, neighboring buildings and towers, trees, and utility and telephone poles. The situation is of particular interest in case of large PV installations such as those used in distributed power generation schemes. Under partially shaded conditions, the PV characteristics get more complex with multiple peaks. Yet, it is very important to understand and predict them in order to extract the maximum possible power. This paper presents a MATLAB-based modeling and simulation scheme suitable for studying the I-V and P-V characteristics of a PV array under a nonuniform insolation due to partial shading. It can also be used for developing and evaluating new maximum power point tracking techniques, especially for partially shaded conditions. The proposed models conveniently interface with the models of power electronic converters, which is a very useful feature. It can also be used as a tool to study the effects of shading patterns on PV panels having different configurations. It is observed that, for a given number of PV modules, the array configuration (how many modules in series and how many in parallel) significantly affects the maximum available power under partially shaded conditions. This is another aspect to which the developed tool can be applied. The model has been experimentally validated and the usefulness of this research is highlighted with the help of several illustrations. The MATLAB code of the developed model is freely available for download.

  • Characteristics of an array with bypass and blocking diodes differ from that of an array without these diodes
  • Blocking diodes prevent reverse current through the series assemblies, which generate lower output voltage in comparison with the others connected in parallel
  • In order to feed the generated power by solar panels to the grid, a boost-type dc/dc converter and an inverter are used
  • If the likely shading pattern on the PV array is known, the simulation model is handy to design the most optimum configuration of the PV array to extract the maximum power
  • Some software packages can be used to model the effects of shading such as PV-Spice, PV-DesignPro, SolarPro, PVcad, and PVsyst

Autonomous PV system to applications in the Eastern of Mexico[32]

Abstract It is particularly important to evaluate the properties of the generation system in the actual operating conditions in order to get a real picture of the amount of electricity which could be generated. The Eastern of Mexico is a region with a significant amount of solar radiation potentially useful for PV applications. Thus, the Energy Laboratory of the University of Yucatan developed an autonomous photovoltaic generator to evaluate the operational performance of a stand-alone PV system in the local environmental conditions. The system created allows monitoring the patterns produced by the generation, storage and consumption of the electrical power to study the transport of energy along the whole system. On the other hand, the solar radiation and the temperature were also monitored because of their impacts on the PV generation pattern.

  • The main systems installed in the container comprise the energy storage system, the monitoring system, and the inverter and charge controller
  • A charger controller was connected between the PV panel and the batteries bank in order to avoid overcharge situations
  • The inverter prevents from extreme cycles of over-discharge extending the batteries lifetime
  • The PV panel is installed on a structure with a rotation axis; therefore, the inclination angle for the PV panel can be easily changed
  • The temperature sensor is installed on the back of a PV module while the solar radiation sensor is fitted with same inclination angle at the edge of the PV panel
  • Environmental sensors such as solar radiation sensor, temperature sensor, and wind speed and wind direction sensors are installed on top of a 6m height tower

Monitoring and analysis of research PV Modules at University of West Bohemia in Pilsen and in the Czech Republic[33]

Abstract In this time, there is a great press on the environment protection, in order the emission of the classic fossil fuels should be reduce. Therefore the higher utilization of the renewable power sources is expanding all over the world. The utilization of the solar radiation for the electricity production by the photovoltaic generators is one of the production way with high regardful of the environment protection. The paper deals with the experience of the PV operation and results in the Czech Republic (CR). Next, the University of West Bohemia (WBU) in Pilsen research activities on the field of PV research systems is discussed.

  • The angle has a great influence on the total daily production of PV, but cleaning modules has a low influence on the PV production
  • The difference between the production of the module with the angle 35 and 60 degrees is approximately 20%, and the difference between 35 and 45 degree is about 10%

Product-integrated PV applications - How industrial design methods yield innovative PV powered products[34]

Abstract Given the high potential of PV technology to reduce the environmental impact of electricity use of products, it would be worthwhile to advance the integration of PV systems in mass produced products. We assume that industrial design engineering (IDE) could play a crucial role in making PV technology fit for product applications by its focus on functionality and usability. IDE might have an added value to existing R&D of PV technology which emphasizes on increased performance and decreased production cost of PV cells and modules. Therefore, in this paper, we will assess how industrial design methods might favour the development of product-integrated PV applications. In our project product designers have conceptually designed 17 products with integrated PV cells. The project took place in 2007 at the School of Industrial Design Engineering of University of Twente in the Netherlands. During the design process several innovative design methods were applied, among which the innovation phase model, lead user studies, platform driven product development, risk diagnosis, technology road mapping, TRIZ, innovative design and styling, innovation journey and constructive technology assessment. By observing 17 PV-powered products which resulted from the project we evaluated the innovative effect of industrial design methods on product-integrated PV applications. The application of IDMs resulted in a broad range of varied innovative PV-powered product concepts ranging from small products, like electronic handhelds, to middle-sized products like toys and portable fridges, to big-sized objects such as building-integrated PV elements and a zeppelin. The results show that the use of carefully chosen and applied industrial design methods can help to better integrate PV technology in products.

  • The main reason for the reduction battery use in products are considered to be cost and environmental issues
  • Batteries cause a lot of user interventions
  • Product-integrated PV systems can reduce the required capacity of batteries and the number of user interventions associated with battery use

Performance evaluation and analysis of 50kW grid-connected PV system[35]

Abstract This paper summarizes the results of these efforts by offering a photovoltaic system structure in 50 kW large scale applications installed in Chosun University dormitory roof. The status of PV system components, are inter-connection and safety equipment monitoring system will be summarized as this article. This describes configuration of utility interactive photovoltaic system which generated power supply for dormitory. In this paper represent 50 kW utility PV system examination result.

  • PV systems are easy to maintain, the life cycle is long, and the installation is easy

A cost analysis of very large scale PV (VLS-PV) system on the world deserts[36]

Abstract To preserve the Earth, a 100 MW very large-scale photovoltaic power generation (VLS-PV) system is estimated assuming that it is installed on the world deserts, which are Sahara, Negev, Thar, Sonora, Great Sandy and Gobi desert. These deserts are good for installing the system because of large solar irradiation and large land area. A PV array is dimensioned in detail in terms of array layout, support, foundation, wiring and so on. Then generation cost of the system is estimated based on the methodology of life-cycle cost (LCC). As a result of the estimation, the generation cost is calculated as 5.3 cent/kWh on Sahara desert, 6.4 cent/kWh on Gobi desert assuming PV module price of $1.0/W, system lifetime of 30 years and interest rate of 3%. These results suggest that VLS-PV systems are economically feasible on sufficient irradiation site even if existing PV system technologies are applied, when PV module price will decrease to a level of $1.0/W.

Steady-state performance of a grid-connected rooftop hybrid wind-photovoltaic power system with battery storage[37]

Abstract This paper reports the performance of a 4-kW grid-connected residential wind-photovoltaic system (WPS) with battery storage located in Lowell, MA, USA. The system was originally designed to meet a typical New-England (TNE) load demand with a loss of power supply probability (LPSP) of one day in ten years as recommended by the Utility Company. The data used in the calculation was wind speed and irradiance of Login Airport Boston (LAB) obtained from the National Climate Center in North Carolina. The present performance study is based on two-year operation. (May 1996-Apr 1998) of the WPS. Unlike conventional generation, the wind and the sunrays are available at no cost and generate electricity pollution-free. Around noontime the WPS satisfies its load and provides additional energy to the storage or to the grid. On-site energy production is undoubtedly accompanied with minimization of environmental pollution, reduction of losses in power systems transmission and distribution equipment, and supports the utility in demand side management. This paper includes discussion on system reliability, power quality, loss of supply and effects of the randomness of the wind and the solar radiation on system design.

  • Due to aging, some modules may experience some discoloration over time from blue to brown due to oxidation which occurs at high temperatures between the actual solar cells and the front glass cover, and it reduces the module's efficiency
  • Linear modeling and Neural networks are used to predict PV performance under various temperature, and wind conditions
  • A converter rectifies the alternating current generated by the wind generator and protects the batteries from being overcharged by wind turbine
  • The air along the coastline is subject to higher temperature differences than air in land due to absorption differences between land and water

Universidad Verde-200 kWp grid connected PV system[38]

Abstract This project consists in the installation of four photovoltaic subgenerators connected to the low voltage grid at Jaen University Campus (Spain), with a total power of 200 kWp. The Univer Project is developed under the Thermie Programme of the EU, with a budget of about 1.8 M euros. The main objective is the integration of a medium scale PV plant using different architectural solutions. This project presents two innovative aspects: on the one hand, the development of the technology necessary to implement medium-high scale PV plants in crowded places, mainly focused on safety and protection systems; on the other, the development and analysis of different architectural solutions to integrate PV generators using constructive structures easily replicable.

  • In order to protect people, installation includes a floating system configuration, a cover of wiring, a permanent insulation controller to detect the earth faults of the generators, and an earth grid
  • Some operating problems may occur in installation of PV, for instance, a current harmonic can be introduced by inverter which can cause interference
  • A permanent insulation controller can be used to detect the loss of the system insulation

Advances in PV semiconductor materials and technology[39]

Abstract It is now accepted that photovoltaics is the most promising of the renewable energy sources for electric power generation. Photovoltaic's ability to provide reliable, high grade energy over an extended lifetime is now well proven in both space and terrestrial applications. Widespread adoption of this clean, silent power source, however, still awaits the achievement of a number of outstanding technical and economic objectives. Extensive research into photovoltaic technology over the last two decades has done enough to conclude that all these goals can be met. The present challenge is to apply these results industrially and commercially so as to make the dream and reality. Photovoltaics can only provide an efficient service to its users if it provides a transparent and trouble free source of electricity. This involves the application of photovoltaic devices in well integrated systems which also include appropriate mechanical and electrical interfaces. The author focuses on one part of the system-the photovoltaic generator itself. This paper reviews the status of international developments and the contributions which they can make in achieving this objective.

Design, performance and cost of energy from high concentration and flat-plate utility-scale PV systems[40]

Abstract This paper presents the results of a recent study to assess the near-term cost of power in central station applications. Three PV technologies were evaluated: Fresnel-lens high-concentration photovoltaic (HCPV);, central receiver HCPV; and flat-plate PV using thin-film copper indium diselenide (CIS) cell technology. Baseline assumptions included PV cell designs and performances projected for the 1995 timeframe, 25 and 100 MW/year cell manufacturing rates, 50 MW power plant size, and mature technology cost and performance estimates. The plant design characteristics are highlighted. Potential sites were evaluated and selected for the PV power plants and cell manufacturing plants. Conceptual designs and cost estimates were developed for the plants and their components. Plant performance was modeled and the designs were optimized to minimize levelized energy costs. Cost estimates for both plant and energy delivered include effects of uncertainty in key parameters. Although the study did not involve detailed engineering, efforts were made to optimize all of the plant designs and minimize levelized energy costs. Cell and module fabrication processes were also developed.


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