Conventional Photovoltaic Module Research Articles

Energy assessment of enhanced fixed low concentration photovoltaic systems

In order to exploit as much as possible the surfaces apt for installation of photovoltaic (PV) systems and also to keep the unit energy cost low (without increasing meaningfully capital and operation/maintenance costs), fixed low concentration systems (LCPVs) can be adopted, such systems are normally based on flat mirrors. LCPVs can be either fixed or tracked, but in this paper the fixed solution is investigated as it is a solution that can be largely exploited in urban and suburban contexts, as well as it represents a retrofit of existing PV plant. In order to mitigate the negative effects of partial shadowing of such systems, together with dust soiling and mismatching, this paper proposes an innovative solution for fixed LCPVs based on Distributed Maximum Power Point Tracking (DMPPT) at substring level, here called Enhanced LCPV (E-LCPV).To evaluate the energy performance improvement of the E-LCPV solution compared with conventional LCPVs, a simulation tool has been developed; it has as input the geographic, geometrical, optical and electrical characteristics of a fixed LCPV system and provides the daily production curves. The novelty of the tool here proposed is its ability to manage non-uniform irradiance conditions on a single PV module, which allows to compare the performance of the system with or without DMPPT at substring level.Specifically, four cases have been simulated: (a) without reflector and with bypass diode (conventional PV module); (b) without reflector but with DMPPT at the substring level; (c) with reflector and with bypass diode; (d) with reflector and with DMPPT at the substring level (E-LCPV).Comparative and parametric results are provided and discussed. Referring to Catania (Italy), results show that, in order to have advantages in using a E-LCPV, the PV module/reflector configuration should be accurately optimized in order to increase the power production, otherwise the cost of E-LCPVs can reduce drastically the advantages of using these kind of systems.

Diagnostic method for photovoltaic systems based on light I–V measurements

Improving photovoltaic (PV) system reliability and reducing maintenance and operating costs have become important factors in increasing the competitiveness of the PV energy market. Addressing these issues requires diagnostic methods that can detect and identify the occurrence and cause of power loss in the PV system, be it external, such as shading or soiling of the PV modules; or degradation of the solar cells and balance-of-system components. This allows for performing preventive and/or reparative maintenance, thus minimizing further losses and costs.This article proposes and experimentally demonstrates for the first time a complete diagnostic methodology for PV string inverter systems, which takes advantage of the current–voltage (I–V) measurement capability of the string inverter itself to perform the fault diagnosis. This enables the detection of shading, increased series-resistance losses, and potential-induced degradation affecting the PV string, by analysing changes in its I–V curve.The diagnostic methodology is based on parameters that can be easily calculated from the shape of the PV string’s light I–V curve characteristic, making it machine-analysis friendly and suitable for implementation in the string inverter. Moreover, the dimensionless formulation of the diagnostic parameters and the application of fuzzy logic in evaluating the diagnostic rules, make this method applicable to a wide range of conventional crystalline silicon based PV systems.The design and analysis of the diagnostic parameters and logic was performed based on module-level tests on conventional crystalline silicon PV modules, and were optimized to detect even small partial shading and increase series-resistance losses. To demonstrate the practical application and operation of this method, the diagnostic parameters and rules were applied “as is” to a field test PV system consisting of a crystalline silicon based PV string and a commercial string inverter capable of measuring the I–V curve of the PV string, yielding a similar high-detection rate.

Comparative simulation analyses on dynamic performances of photovoltaic–thermal solar collectors with different configurations

The electrical efficiency of photovoltaic (PV) module can be increased by reducing the operating temperature of PV module. The hybrid photovoltaic/thermal (PV/T) solar system consists of conventional PV module and attached heat transfer pipe with internal working fluid flowing to extract heat energy from PV module. This article presents a brief review on the latest researches and applications of the PV/T systems. Afterwards, based on energy-balance equations, mathematical models for several PV/T systems with different configurations are developed. Analytical expressions for both the electrical and thermal performance parameters are derived as functions of climatic and design parameters to conduct comparative analyses. The calculation results indicate that the changes in the PV/T configurations have influences on electrical and thermal performances of the PV/T system. Further suggestions on configurations optimization for practical applications are propounded.

태양광 발전시스템의 환경조건을 고려한 PV 모듈 구성

This paper proposes the configuration of photovoltaic(PV) module considering the environment conditions of the PV system. The PV system is consisted of the series-parallel connection of the PV module. When shadows or changes of the radiation or an electrical characteristic in the solar cell are happened to PV system, the serious power loss will occur. If the PV module connected in series has the shadows, the output current is restricted to current of shaded PV module. Also if shadow is occurred to the parallel connection PV module, the output voltage is limited to voltage of shaded PV module. These problems are caused power loss. Therefore, this paper proposes the method that makes the output power of the PV module equalize by reconfiguration of PV module using the switching considering these environment conditions. A validity of the method proposed in this paper proves through comparing with performance of conventional PV module.

Tracking control of high‐concentration photovoltaic systems for minimizing power losses

ABSTRACTThis paper presents three key factors that cause system mismatches and power losses in high‐concentration photovoltaic (HCPV) systems. The first factor is the I–V mismatch within a module, similar to the manufacturing mismatches in conventional photovoltaic modules. The second factor is the misalignments amongst modules, and the third factor is the tracking control. Unlike in the conventional photovoltaic systems, the second and the third factors in HCPV systems introduce larger electro‐optical mismatches due to narrow acceptance angles. We have developed a model to address these three factors. It allows an accurate estimation of power losses in HCPV systems, which enabled us to propose configurations to reduce power losses without adding additional electrical components to the system. Simulation results show that the power harvest can be increased as much as 8.5% for a system using open‐loop controls by simply increasing the number of strings at the time of calibration. Experimental test results are presented for validation. Copyright © 2012 John Wiley & Sons, Ltd.

Experimental investigation on the photovoltaic–thermal solar heat pump air-conditioning system on water-heating mode

An experimental study on operation performance of photovoltaic–thermal solar heat pump air-conditioning system was conducted in this paper. The experimental system of photovoltaic–thermal solar heat pump air-conditioning system was set up. The performance parameters such as the evaporation pressure, the condensation pressure and the coefficient of performance (COP) of heat pump air-conditioning system, the water temperature and receiving heat capacity in water heater, the photovoltaic (PV) module temperature and the photovoltaic efficiency were investigated. The experimental results show that the mean photovoltaic efficiency of photovoltaic–thermal (PV/T) solar heat pump air-conditioning system reaches 10.4%, and can improve 23.8% in comparison with that of the conventional photovoltaic module, the mean COP of heat pump air-conditioning system may attain 2.88 and the water temperature in water heater can increase to 42 °C. These results indicate that the photovoltaic–thermal solar heat pump air-conditioning system has better performances and can stably work.

Energy performance of water hybrid PV/T collectors applied to combisystems of Direct Solar Floor type

The integration of photovoltaic (PV) modules in buildings allows one to consider a multifunctional frame and then to reduce the cost by substitution of components. In order to limit the rise of the cell operating temperature, a photovoltaics/thermal (PV/T) collector combines a solar water heating collector and PV cells. The recovered heat energy can be used for heating systems and domestic hot water. A combination with a Direct Solar Floor is studied. Its low operating temperature level is appropriate for the operating conditions of the mono- or poly-crystalline photovoltaic modules which are selected in that study. However, for a system including a glass covered collector and localised in Mâcon area in France, we show that the annual photovoltaic cell efficiency is 6.8% which represents a decrease of 28% in comparison with a conventional non-integrated PV module of 9.4% annual efficiency. This is obviously due to a temperature increase related to the cover. On the other hand, we show that without a glass cover, the efficiency is 10% which is 6% better than a standard module due to the cooling effect. Moreover, in the case of a glazed PV/T collector with a conventional control system for Direct Solar Floor, the maximum temperature reached at the level of the PV modules is higher than 100 °C. This is due to the oversize of the collectors during the summer when the heating needs are null, i.e. without a heated swimming pool for example. This temperature level does not allow the use of EVA resin (ethylene vinyl acetate) in PV modules due to strong risks of degradation. The current solution consists of using amorphous cells or, if we do not enhance the thermal production, uncovered PV/T collector. Further research led to water hybrid PV/T solar collectors as a one-piece component, both reliable and efficient, and including the thermal absorber, the heat exchanger and the photovoltaic functions.

Experimental evaluation of V-trough (2 suns) PV concentrator system using commercial PV modules

V-trough photovoltaic (PV) concentrator systems along with conventional 1-sun PV module is designed and fabricated to assess PV electricity cost ($/W) reduction. V-trough concentrator (2-sun) system is developed for different types of tracking modes: seasonal, one axis north–south and two axes tracking. Three design models based on these tracking modes are used to develop the V-trough for a 2-sun concentration. Commercially available PV modules of different make and types were evaluated for their usability under 2-sun concentration. The V-trough concentrator system with geometric concentration ratio of 2 (2-sun) increases the output power by 44% as compared to PV flat-plate system for passively cooled modules. Design models with lower trough angles gave higher output power because of higher glass transmittivity. PV modules with lower series resistance gave higher gain in output power. The unit cost ($/W) for a V-trough concentrator, based on different design models, is compared with that of a PV flat plate system inclined at latitude angle (Mumbai, φ=19.12°).

A model for the series–parallel association of photovoltaic devices

AbstractThis work presents a method to obtain the one‐exponential model parameters of a series–parallel association of photovoltaic (PV) devices. From the linear expressions of the I–V characteristic in short‐circuit and open‐circuit zones, simple equations for association model parameters are obtained based on cell parameters. In order to validate the model, measurements have been performed in the 33 cells of a conventional PV module previously modified to have access to its cells, either individually or associated. Series and parallel proposed models have been applied to measurements, supposing all module cells are connected either in series or in parallel. Good approximations have been found in both cases. The method here proposed supplies a useful formulation that can be used in simulation programmes and array calculations. Copyright © 2005 John Wiley & Sons, Ltd.

A simple ray tracer to compute the optical concentration of photovoltaic modules

AbstractIn a conventional photovoltaic module, some light that falls between the solar cells is internally reflected onto the cells via the backsheet and the glass–air interface of the module; thus, a module can be considered a static concentrator. We present a simple ray tracer that computes a module's optical concentration as a function of cell separation, cell geometry, and the optical properties of the encapsulants. The ray tracer's primary simplification is to divide the module's backsheet into small pixels and, since the reflection from the backsheet is approximately Lambertian and independent of the incident angle, to sum the intensity of all rays that enter a pixel and treat them as one. The advantage of this pixel approximation is that it makes it simple to simulate curved surfaces—such as the corners of a pseudo‐square solar cell—within short computation times. The results of the simple ray tracer are shown to be consistent with those of a conventional ray tracer and an LBIC experiment. We also apply the ray tracer to a present‐day SunPower module and find that 25% of the photons that fall between the cells are internally reflected onto the cells, which results in an optical concentration of 1·024. Copyright © 2005 John Wiley & Sons, Ltd.

Analysis and modelling the reverse characteristic of photovoltaic cells

Models to represent the behaviour of photovoltaic (PV) solar cells in reverse bias are reviewed, concluding with the proposal of a new model. This model comes from the study of avalanche mechanisms in PV solar cells, and counts on physically meaningful parameters. It can be adapted to PV cells in which reverse characteristic is dominated by avalanche mechanisms, and also to those dominated by shunt resistance or with breakdown voltages far from a safe measurement range. A procedure to calculate model parameters based in piece-wise fitting is also proposed. The model has been applied to isolated crystalline solar cells measured at different conditions, and also to cells encapsulated in a conventional PV module. Good fitting has been found between the experimental and modelled curves. Evolution of calculated breakdown voltages with temperature is in accordance with avalanche theories.

Experimental study of mismatch and shading effects in the – characteristic of a photovoltaic module

Abstract A conventional photovoltaic module has been prepared with the purpose of accessing its cells either individually or associated. Measurements of every cell and of the whole module have been performed in direct and reverse bias, with the objective of documenting the scattering in cell parameters, working point of the cells and shading effects. Several shading profiles have been tested, and the influence of the reverse characteristic of the shaded cell in module output is stressed.

97/00441 Alkaline fuel cells: A critical view

Improving photovoltaic (PV) system reliability and reducing maintenance and operating costs have become important factors in increasing the competitiveness of the PV energy market. Addressing these issues requires diagnostic methods that can detect and identify the occurrence and cause of power loss in the PV system, be it external, such as shading or soiling of the PV modules; or degradation of the solar cells and balance-of-system components. This allows for performing preventive and/or reparative maintenance, thus minimizing further losses and costs.This article proposes and experimentally demonstrates for the first time a complete diagnostic methodology for PV string inverter systems, which takes advantage of the current–voltage (I–V) measurement capability of the string inverter itself to perform the fault diagnosis. This enables the detection of shading, increased series-resistance losses, and potential-induced degradation affecting the PV string, by analysing changes in its I–V curve.The diagnostic methodology is based on parameters that can be easily calculated from the shape of the PV string’s light I–V curve characteristic, making it machine-analysis friendly and suitable for implementation in the string inverter. Moreover, the dimensionless formulation of the diagnostic parameters and the application of fuzzy logic in evaluating the diagnostic rules, make this method applicable to a wide range of conventional crystalline silicon based PV systems.The design and analysis of the diagnostic parameters and logic was performed based on module-level tests on conventional crystalline silicon PV modules, and were optimized to detect even small partial shading and increase series-resistance losses. To demonstrate the practical application and operation of this method, the diagnostic parameters and rules were applied “as is” to a field test PV system consisting of a crystalline silicon based PV string and a commercial string inverter capable of measuring the I–V curve of the PV string, yielding a similar high-detection rate.

Effect of concentration on the performance of flat plate photovoltaic modules

The effect of low concentration ratios on the performance of passively cooled conventional photovoltaic modules has been investigated. Peak power outputs of up to 140 W per square metre of module area have been obtained with single crystal modules of high cell packing factor using a 2.2 X plane mirror concentrator. Both cell temperature and series resistance losses are found to be important in limiting module efficiency. Performance simulations indicate that the use of a 4 X concentrator with polar axis tracking will increase annual peak output by a factor of 3.2 over that of a fixed flat plate module.

An optimum concentration factor for conventional silicon photovoltaic modules

The current-voltage characteristics of conventional photovoltaic modules were measured at 25, 45 and 60 °C for illumination levels varying from 50 to 350 mW cm −2. The measured module parameters are used to deduce an optimum concentration factor based on the module efficiency. The results indicate an optimum concentration factor of 2 at a temperature of 45 °C.