Simulation of grape culture irrigation with photovoltaic V-trough pumping systems

In large areas of the Northeast of Brazil, the population is faced with the severe problem of water shortage aggravated with the lack of electric power. However, some places, like the area next to the river São Francisco, near the city of Petrolina, in the state of Pernambuco, have become quite prosperous with the cultivation of grape crops, either for wine production or to be consumed as fruits. Wine exports have grown as an important economic activity in the region. On the other hand, in areas far from the electric network, photovoltaic pumping systems have contributed to the supply of water for local rural communities. Production of fruits, with water supplied by photovoltaic systems, might, then, become a good alternative in terms of local economic activities. The viability of this proposal depends strongly on the market value of the crop. Taking advantage of some significant technical benefits provided by low concentration tracking devices we propose to use those systems to drive local irrigated crops. Among the large family of concentrators available, V-troughs are particularly adequate for photovoltaic applications since, for certain combinations of the concentration ratio (C) and vertex angle (Ψ), they provide a perfectly uniform illumination in the region where the modules are located (absorber region). A drip irrigation system, located in the city of Petrolina, has been simulated and the maximum surface that can be irrigated by a V-trough photovoltaic pumping equipment was estimated by performing a water balance on a monthly basis. With an array of 1.3 kW_p it was found that the system is able to irrigate, without deficit, 2.11 ha. A fixed photovoltaic pumping equipment, with the same photovoltaic array, is able to irrigate an area of 1.20 ha. In both cases, the water stored in the soil contributes with an increase of 33% to the irrigated area, as compared to the case where that contribution is not considered.     

Enhanced heat dissipation of V-trough PV modules for better performance

A concentrator photovoltaic (PV) module, in which solar cells are integrated in V-troughs, is designed for better heat dissipation. All channels in the V-trough channels are made using thin single Al metal sheet to achieve better heat dissipation from the cells under concentration. Six PV module strips each containing single row of 6 mono-crystalline Si cells are fabricated and mounted in 6 V-trough channels to get concentrator V-trough PV module of 36 cells with maximum power point under standard test condition (STC) of 44.5 W. The V-trough walls are used for light concentration as well as heat dissipation from the cells which provides 4 times higher heat dissipation area than the case when V-trough walls are not used for cooling. The cell temperature in the V-trough module remains nearly same as that in a flat plate PV module, despite light concentration. The controlled temperature and increased current density in concentrator V-trough cells results in higher V_oc of the module.     

Solar distillation of water using a V-trough solar concentrator with a wick-type solar still

A V-trough solar concentrator has been combined with an inclined flat-plate wick-type solar still. Outdoor testing was carried out with and without the solar concentrator on clear days in summer and winter. The equipment was used to investigate the enhancement of the outdoor performance of the wick-type solar still by the solar concentrator.It has been concluded that use of the solar concentrator with the inclined wick-type solar still can lead to a greater fractional increase in still efficiency and productivity on clear days in winter than on clear days in summer.     

Comparison of the performance of PV water pumping systems driven by fixed, tracking and V-trough generators

Photovoltaic pumping systems with solar tracking, coupled to low concentration cavities, have been proposed as a viable alternative to reduce the final cost of the pumped water volume. V-trough concentrators are particularly appropriate for photovoltaic applications since, for certain combinations of the concentration ratio (C) and vertex angle (Ψ), they provide uniform illumination on the region where the modules are located. Water pumping systems are only operational when the irradiance is larger than a minimum irradiance level (I_C). Solar tracking increases the average collected irradiance and, for a system operating with a given critical irradiance level (I_C), it is verified that the smaller the relationship , the larger the useful energy. Thus, the gain, in terms of pumped water volume, provided by solar tracking systems, can be larger than the gain in collected solar radiation. The combination of both devices, tracking and concentration provides an additional increase of the benefits resulting from the use of solar trackers. By means of the “Utilizability Method”, we estimate the long-term gains of pumped water volume, for tracking systems, with and without concentration, against fixed systems. The long-term water volume has been calculated using the characteristic curve of a tested PVP system with a tracking V-trough concentrator. Results show that, for the climate of the city of Recife (PE-Brazil), the annual pumped water volume of the tracking system is 1.41 times the value obtained with the fixed system. In that case, the gains observed for the collected solar energy were around 1.23. For the PVP system with tracking V-trough concentrator the annual benefits for pumped water volume are around 2.49, while for collected solar radiation we found 1.74. The annualized cost of the cubic meter of pumped water has been estimated for the three configurations. Results show a cost reduction of the order of 19% for the tracking system and of 48% for the concentrating system, when compared to the fixed configuration.     

Study of a solar water heater using stationary V-trough collector

There are various types of solar water heater system available in the commercial market to fulfill different customers’ demand, such as flat plate collector, concentrating collector, evacuated tube collector and integrated collector storage. A cost effective cum easy fabricated V-trough solar water heater system using forced circulation system is proposed. Integrating the solar absorber with the easily fabricated V-trough reflector can improve the performance of solar water heater system. In this paper, optical analysis, experimental study and cost analysis of the stationary V-trough solar water heater system are presented in details. The experimental result has shown very promising results in both optical efficiency of V-trough reflector and the overall thermal performance of the solar water heater.     

A comprehensive study of dense-array concentrator photovoltaic system using non-imaging planar concentrator

A special modeling method using Simulink has been developed to analyze the electrical performance of dense-array concentrator photovoltaic (CPV) system. To optimize the performance of CPV system, we have adopted computational modeling method to design the best configuration of dense-array layout specially tailored for flux distribution profile of solar concentrator. It is an expeditious, efficient and cost effective approach to optimize any dense-array configuration for any solar concentrator. A prototype of non-imaging planar concentrator (NIPC) was chosen in this study for verifying the effectiveness of this method. Mismatch effects in dense array solar cells caused by non-uniform irradiance as well as sun-tracking error normally happens at the peripheral of the array. It is a crucial drawback that affects the electrical performance of CPV systems because maximum output power of the array is considerably reduced when a current–voltage (I–V) curve has many mismatch steps and thus leads to lower fill factor (FF) and conversion efficiency. The modeling method is validated by assembling, installing and field testing on an optimized configuration of solar cells with the NIPC prototype to achieve a conversion efficiency of 34.18%. The measured results are in close agreement with simulated results with a less than 3% deviation in maximum output power.     

Electrical performance results from physical stress testing of commercial PV modules to the IEC 61215 test sequence

This paper presents statistical analysis of the behaviour of the electrical performance of commercial crystalline silicon photovoltaic (PV) modules tested in the Solar Test Installation of the European Commission's Joint Research Centre from 1990 up to 2006 to the IEC Standard 61215 and its direct predecessor CEC Specification 503. A strong correlation between different test results was not observed, indicating that the standard is a set of different, generally independent stress factors. The results confirm the appropriateness of the testing scheme to reveal different module design problems related rather to the production quality control than material weakness in commercial PV modules.     

Solar photovoltaic (PV) energy; latest developments in the building integrated and hybrid PV systems

Environmental concerns are growing and interest in environmental issues is increasing and the idea of generating electricity with less pollution is becoming more and more attractive. Unlike conventional generation systems, fuel of the solar photovoltaic energy is available at no cost. And solar photovoltaic energy systems generate electricity pollution-free and can easily be installed on the roof of residential as well as on the wall of commercial buildings as grid-connected PV application. In addition to grid-connected rooftop PV systems, solar photovoltaic energy offers a solution for supplying electricity to remote located communities and facilities, those not accessible by electricity companies.The interest in solar photovoltaic energy is growing worldwide. Today, more than 3500 MW of photovoltaic systems have been installed all over the world. Since 1970, the PV price has continuously dropped [8]. This price drop has encouraged worldwide application of small-scale residential PV systems. These recent developments have led researchers concerned with the environment to undertake extensive research projects for harnessing renewable energy sources including solar energy. The usage of solar photovoltaic as a source of energy is considered more seriously making future of this technology looks promising.The objective of this contribution is to present the latest developments in the area of solar photovoltaic energy systems. A further objective of this contribution is to discuss the long-term prospect of the solar photovoltaic energy as a sustainable energy supply.     

An improved modeling method to determine the model parameters of photovoltaic (PV) modules using differential evolution (DE)

To accurately model the PV module, it is crucial to include the effects of irradiance and temperature when computing the value of the model parameters. Considering the importance of this issue, this paper proposes an improved modeling approach using differential evolution (DE) method. Unlike other PV modeling techniques, this approach enables the computation of model parameters at any irradiance and temperature point using only the information provided by the manufacturer’s data sheet. The key to this improvement is the ability of DE to simultaneously compute all the model parameters at different irradiance and temperature. To validate the accuracy of the proposed model, three PV modules of different types (multi-crystalline, mono-crystalline and thin-film) are tested. The performance of the model is evaluated against the popular single diode model with series resistance R_s. It is found that the proposed model gives superior results for any irradiance and temperature variations. The modeling method is useful for PV simulator developers who require comprehensive and accurate model for the PV module.     

Energy metrics analysis of hybrid – photovoltaic (PV) modules

In this paper, energy metrics (energy pay back time, electricity production factor and life cycle conversion efficiency) of hybrid photovoltaic (PV) modules have been analyzed and presented for the composite climate of New Delhi, India. For this purpose, it is necessary to calculate (1) the energy consumption in making different components of the PV modules and (2) the annual energy (electrical and thermal) available from the hybrid-PV modules. A set of mathematical relations have been reformulated for computation of the energy metrics. The manufacturing energy, material production energy, energy use and distribution energy of the system have been taken into account, to determine the embodied energy for the hybrid-PV modules. The embodied energy and annual energy outputs have been used for evaluation of the energy metrics. For hybrid PV module, it has been observed that the EPBT gets significantly reduced by taking into account the increase in annual energy availability of the thermal energy in addition to the electrical energy. The values of EPF and LCCE of hybrid PV module become higher as expected.     

Performance evaluation of solar PV/T system: An experimental validation

In this communication, an attempt has been made to develop a thermal model of an integrated photovoltaic and thermal solar (IPVTS) system developed by previous researchers. Based on energy balance of each component of IPVTS system, an analytical expression for the temperature of PV module and the water have been derived. Numerical computations have been carried out for climatic data and design parameters of an experimental IPVTS system. The simulations predict a daily thermal efficiency of around 58%, which is very close to the experimental value (61.3%) obtained by Huang et al.     

Feasibility study of brackish water desalination in the Egyptian deserts and rural regions using PV systems

Fresh water is the most important source for life on the earth. In the Egyptian deserts and rural areas, there is a shortage of fresh water in spite of the presence of large sources of brackish water. Solar energy is abundant in these remote areas of Egypt, where the amount of sunshine hours is around 3500 h/year. This paper introduces a feasibility study of water desalination in these areas using photovoltaic energy as the primary source of energy. The availability of water resources and solar energy in these areas has been investigated. Also, a design of a PV powered small scale reverse osmosis water desalination system is studied and economically estimated. It is found that the cost of producing 1 m³ of fresh water using the small PV powered RO water desalination systems is 3.73$. This cost is based on using a small system that is operating during the daylight only. If the system size and the daily period of operation are increased, the price of producing fresh water will be decreased in these regions. Also, it is important to mention that using renewable energy sources in feeding different systems in these rural areas with their energy demands will maintain their environment clean and healthy for people.     

An experimental implementation and testing of a concentrated hybrid photovoltaic/thermal system with monocrystalline solar cells using linear Fresnel reflected mirrors

Integration of solar concentrators with photovoltaic (PV) systems reduces the required number of PV panels, which often account for the major costs of PV systems. The linear Fresnel reflector mirror is considered more effective because of its simplicity and effortless fabrication. An experimental test rig of a concentrated PV/thermal system that employs a linear configuration and horizontal absorber was built for evaluating its electrical and thermal performances. The considered concentrator consists of various widths of flat glass mirrors, which positioned with different angles, and with sun light focusing on the PV cells that fixed over an active cooling system. The experimental investigation of the proposed concentrated PV/thermal system shows that higher electrical and thermal efficiencies can be achieved at comparatively high temperature levels than that typically utilized in a nonconcentrated PV/thermal system. The characteristics of PV cells also indicate that the electrical efficiency values in case of no concentration and with concentration ratio of 6.0 are 9.6%, and 11%, respectively. The measured values for the inlet and outlet cooling water temperatures of the receiver showed that the maximum outlet temperature reached was 75°C with a flow rate of 0.025 L/min, and the product thermal efficiency was 62.3%. These obtained results illustrate an adequate and good thermal and electrical performance under the meteorological weather conditions of the province of Al‐Karak in Jordan.     

Experimental investigation of wind effects on a standalone photovoltaic (PV) module

The pressure field on the upper and lower surfaces of a photovoltaic (PV) module comprised of 24 individual PV panels was studied experimentally in a wind tunnel for four different wind directions. The results show that the pressure distribution on the module surface is symmetric about its mid-plane for head-on wind (0° and 180°) and asymmetric at other wind directions. The inter-panel gap (which is essential in large PV modules) is found to influence module's surface pressure field. Pressure magnitudes on the module surface were increased with the module inclination angle, as expected. It is also observed that the mean pressure magnitudes on the PV module under smooth wind exposure are higher than those under open terrain wind exposure.     

Parametric study of various configurations of hybrid PV/thermal air collector: Experimental validation of theoretical model

In this paper, an attempt has been made to evaluate the overall performance of hybrid PV/thermal (PV/T) air collector. The different configurations of hybrid air collectors which are considered as unglazed and glazed PV/T air heaters, with and without tedlar. Analytical expressions for the temperatures of solar cells, back surface of the module, outlet air and the rate of extraction of useful thermal energy from hybrid PV/T air collectors have been derived. Further an analytical expression similar to Hottel–Whiller–Bliss (HWB) equation for flat plate collector has also been derived in terms of design and climatic parameters. Numerical computations have been carried out for composite climate of New Delhi and the results for different configurations have been compared. The thermal model for unglazed PV/T air heating system has also been validated experimentally for summer climatic conditions. It is observed that glazed hybrid PV/T without tedlar gives the best performance.     

Measurements, analyses and evaluation of residential PV systems by Japanese monitoring program

This paper is about measurements, analyses and evaluation of residential PV systems in the Japanese Monitoring Program, on which JQA was subsidized by NEDO (New Energy Development and Industrial Technology Organization) that is currently proceeding [NSS R&D] from FY1997 to FY 2000.The aim of this investigation refers, through the data evaluation and analyses, to obtain knowledge required for optimizing design of PV systems, such as system performance, characteristics and regional dependency under practical operation and to develop the system evaluation technology on the design parameter method.     

Encapsulation of PV modules using ethylene vinyl acetate copolymer as a pottant: A critical review

The primary purpose of this work is to review the literature about what is and is not known about using ethylene vinyl acetate (EVA0 copolymer as the encapsulant (or pottant) material in photovoltaic (PV) modules. Secondary purposes include elucidating the complexity of the encapsulation problem, providing an overview about encapsulation of PV cells and modules, providing a historical overview of the relevant research and development on EVA, summarizing performance losses reported for PV systems deployed since ca. 1981, and summarizing the general problems of polymer stability in a solar environment. We also provide a critical review of aspects of reported work for cases that we believe are important.Failure modes resolved in the early work to establish reliability of deployed modules and the purposes and properties of pottants, are summarized. Typical performance losses in large field-deployed, large-scale systems ranging from 1% to 10% per year are given quantitatively, and qualitative reports of EVA discoloration are summarized with respect to ultraviolet (UV), world-wide location and site dependence.The general stability of polymers and their desirable bulk properties for solar utilization are given. The stabilization formulation for EVA, its effectiveness, and changes in it during degradation are discussed. The degradation mechanisms for the base resin, e.g., unstabilized Elvax 150^TM, and stabilized EVA are indicated for literature dating to the early 1950s, and the role played by unsaturated chromophores is indicated. The limited number of studies relating discoloration and PV cell efficiency are summarized.Observed degradation of EVA or the unstabilized base resin in the laboratory and examples used to measure the degradation are summarized in sections entitled: (1) thermally-induced degradation; (2) photodegradation and photothermal degradation of EVA in different temperature regimes; (3) photobleaching and photodegradation of the UV absorber and cross-linking agent; (4) acetic acid and metal and metal-oxide catalyzed oxidative degradation; and (5) discolaration and PV cell efficiency losses.Processing effects/influences on EVA stability are discussed in sections entitled: (1) EVA raw materials and extruded, uncured films; (2) thermal encapsulation processes; (3) effects of lamination, curing, and curing peroxide on gel content and chromophores formed; and (4) incomplete shielding of curing-generated chromophores. A summary is given for the limited number of accelerated lifetime testing efforts and examples of erroneous service lifetime predictions for EVA are discussed. The known factors that effect the discoloration rate of several EVA formulations are discussed in which the reduction in rate by using UV-absorbing superstrates is a prime example. A summary is given of what is and is not known about EVA degradation mechanisms, degradation from exposures in field-deployed modeules and/or laboratory testing, and factors that contribute to EVA stability or degradation. Finally, conclusions about using Elvax 150 in EVA formulations are summarized, and future prospects for developing the next-generation pottant for encapsulating PV modules are discussed.     

The thin film flexible floating PV (T3F-PV) array: The concept and development of the prototype

The paper presents the concept and design behind the thin film flexible floating PV (T3F-PV) array, aimed at offshore large scale generation. The development of such an array comprises of non-conventional application of thin film PV panels. There are some issues envisaged, primarily the electrical reliability of the panels were they are prone to water absorption. Also the presence of the water could lead to cooling which would be an advantage of the system. Analysis of these issues and a first stage towards the development of the concept was through the manufacturing and operation of a small scale prototype in an enclosed water body in Sudbury, Canada. The data gathered from a small scale prototype leads to an estimated 0.5% decrease in electrical efficiency after the 45 day testing period mainly due to sediment occlusion on the PV panels. The cooling effect of the water could be calculated to an averaged electrical improvement of 5% through a 3 day comparison test (conducted when the floating PV had been exposed to their water conditions for almost 3 months). Also a significant variation in electrical output could be noted if the floating panels were allowed to go just below the waterline or if they were designed to stay on top of it. Some changes to the design were discussed to improve the concept and lead it onto the next step in the development, with a larger scale installation operating in the open sea with harsher environments to be dealt with.     

PV system sizing using observed time series of solar radiation

Sizing represents an important part of photovoltaic system design. This paper describes a sizing procedure based on the observed time series of solar radiation. Using a simple geometrical construction, the sizing curve is determined as a superposition of contributions from individual climatic cycles of low daily solar radiation. Unlike the traditional methods based on loss-of-load probability, the reliability of supply enters in this method through the length of the time series of data used in the analysis. The method thus resembles techniques used in other branches of engineering where extreme values are considered as functions of certain recurrence intervals.     

Statistically adjusted engineering (SAE) modeling of metered roof-top photovoltaic (PV) output: California evidence

Accurate hourly photovoltaic (PV) output data are useful for engineering design, cost-effectiveness evaluation, rate design, system operation, transmission planning, risk management, and policy analysis. However, a large sample of hourly metered PV data is seldom available, and engineering simulation is often the only practical means to obtain hourly PV output. Based on an analysis of net energy metering (NEM) funded by the California Public Utilities Commission (CPUC), this paper presents statistically adjusted engineering (SAE) modeling of metered output of 327 roof-top PV installations in California for the 12-month period of January–December 2008. The key findings are: (a) the metered PV output is on an average 80–90% of simulated performance; and (b) the simulated data have useful information for accurately predicting metered PV performance. Plausible causes for (a) include incomplete input data for PV simulation, occasional failures in metered data recording, and less than ideal conditions for PV performance in the real world.