Efficiency Of Photovoltaic Modules Research Articles

Energy and exergy analysis of hybrid micro-channel photovoltaic thermal module

In this communication, an attempt has been made to evaluate energy and exergy analysis of a hybrid micro-channel photovoltaic thermal (MCPVT) module based on proposed micro-channel solar cell thermal (MCSCT) under constant mass flow rate of air in terms of design and climatic parameter. The performance in terms of overall annual thermal and exergy gain and exergy efficiency of micro-channel photovoltaic thermal module have been evaluated by considering four weather conditions for different climatic conditions of India. Further analysis has also been carried out for single channel photovoltaic thermal (SCPVT) module and the results of micro-channel photovoltaic thermal module and single channel photovoltaic thermal module have been compared. On the basis of numerical computations, it has been observed that an overall annual thermal and exergy gains have been increased by 70.62% and 60.19% respectively for MCPVT module for Srinagar climatic conditions. Similar observations have been made for Bangalore, Jodhpur and New Delhi.

Spectral Reflectance Patterns of Photovoltaic Modules and Their Thermal Effects

Determination of the working temperature of photovoltaic (PV) modules is an essential task in research and engineering projects. It acquires more relevance in the current environment, characterized by increasing figures of installed PV power, module efficiency, solar applications, and operational configurations. However, most of the current procedures for temperature determination of PV modules are simply based on empirical correlations, carried out at conditions defined by some specific standards, with the corresponding lack of accuracy when modules work under real conditions. Thus, the present work looks into a formal procedure for temperature determination by conducting a power balance between the dynamic incoming and outgoing power fluxes. Some additional parameters are included when compared with classic expressions. In particular, the spectral reflectance of the tandem glass-semiconductor is measured to determine the reflected fraction of solar irradiance. The relationship between reflectance and equilibrium temperature is determined for a representative group of PV modules, and the influence that the working point exerts on the module temperature has also been taken into account. Finally, the influence of spectral distribution on module temperature has been quantified by simulations carried out by using a spectral model. In this way, determination of absolute temperature is achieved within a ±2°C range, regardless of module characteristics and climatic or operational conditions. In addition, temperature differences between PV modules that work under the same external conditions can be predicted within ±0.5°C. To summarize, a thermal model suitable for different PV modules and working configurations is presented. Some new parameters are introduced in the calculus process, and the influence of the most relevant ones has been quantified. In this way, the present work is aimed at making a contribution to the study of PV module temperature.

Proposal for a high voltage AlGaAs/AlGaAs/GaAs triple junction photovoltaic cell

A monolithic high voltage 1.87 eV AlGaAs/1.65 eV AlGaAs/1.42 eV GaAs triple junction (3J) photovoltaic (PV) cell design is presented. The motivation for this particular design is to reduce resistive I 2 R power loss that degrades PV module efficiency, to bypass the use of limited resources such as indium and germanium, and to simplify epitaxial growth with the lattice matched Al x Ga 1− x As semiconductor family.

Development of an Installation to Reduce the Temperature Photovoltaic Modules and Improve Efficiency

Development of an Installation to Reduce the Temperature Photovoltaic Modules and Improve Efficiency

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.

Testing the technologies

The penetration of photovoltaic (PV) systems in Japan has been on the rise. Two factors have been promoting the increase: improved generation efficiency of PV modules and governmental subsidies for the initial cost of residential PV generation systems. As a result, the cumulative installed PV capacity has increased exponentially; however, the cumulative installed PV capacity by 2007 was only about 40% of the target for 2010 (4,820 MW). Reaching the target and promoting larger installation capacities in the future will require further installation in the residential sector and the construction of large-scale PV systems. The New Energy and Industrial Technology Development Organization (NEDO) of Japan has conducted several demonstration projects to investigate technological issues regarding the large penetration of PV generation systems and to develop new technologies for using PV generation systems effectively. One of NEDO's demonstration grid-connected PV projects is the Ohta Project, a cluster of PV systems in a residential development. Another is the Wakkanai Project, the largest central-station PV system in Japan.

Geographical variation of the conversion efficiency of crystalline silicon photovoltaic modules in Europe

AbstractWe present a geographical assessment of the performance of crystalline silicon photovoltaic (PV) modules over Europe. We have developed a method that is based on a material specific analytical expression of the PV conversion efficiency, relative to nominal efficiency, as a function of module temperature and irradiance. This method is combined with a climate database that includes average daytime temperature and irradiance profiles. It is found that the geographical variation in ambient temperature and yearly irradiation causes a decrease in overall yearly PV performance from 3 to 13% relative to the performance under Standard Test Conditions, with the highest decrease found in the Mediterranean region. Based on the above results we developed a simplified linear expression of the relative PV module efficiency that is a simple function of yearly total irradiation and yearly average daytime temperature. The coefficients to the linear expression are found by fitting to the map resulting from the above‐mentioned analytical approach. The prediction of total yearly PV output from this linear fit deviates less than 0·5% from the more detailed calculation, thus providing a faster and more simplified alternative to the yield estimate, in the case when only limited climate data are available. Copyright © 2008 John Wiley & Sons, Ltd.

Experimental natural convection on vertical surfaces for building integrated photovoltaic (BIPV) applications

An experimental study on natural convection in an open channel is carried out in order to investigate the effect of the geometrical configuration of heat sources on the heat transfer behaviour. To this aim, a series of vertical heaters are cooled by natural convection of air flowing between two parallel walls. The objective of the work is to investigate the physical mechanisms which influence the thermal behaviour of a double-skin photovoltaic (PV) facade. This results in a better understanding of the related phenomena and infers useful engineering information for controlling the energy transfers from the environment to the PV surfaces and from the PV surfaces to the building. Furthermore increasing the heat transfer rate from the PV surfaces increases the conversion efficiency of the PV modules since they operate better as their temperature is lower. The test section consists in a double vertical wall, 2 m high, and each wall is constituted by 10 different heating modules 0.2 m high. The heater arrangement simulates, at a reduced scale, the presence of a series of vertical PV modules. The heat flux at the wall ranges from 75 to 200 W/m 2. In this study, the heated section is 1.6 m in height, preceded by an adiabatic of 0.4 m in height. Different heating configurations are analyzed, including the uniform heating mode and two different configurations of non uniform, alternate heating. The experimental procedure allows the wall surface temperature, local heat transfer coefficient and local and average Nusselt numbers to be inferred. The experimental evidences show that the proper selection of the separating distance and heating configuration can noticeably decrease the surface temperatures and hence enhance the conversion efficiency of PV modules.

Sustainability analysis of renewables for climate change mitigation

Carbon dioxide is a major greenhouse gas (GHG) responsible for climate change. The energy sector accounts for approximately 75 % of the total carbon dioxide emissions in the world. The main options for reducing carbon dioxide emissions in energy systems are energy efficiency, and utilization of renewable energy and nuclear energy. In the present global energy scenario, the share of modern renewables in the total primary energy use is marginal (about 4.5 %). This paper assesses the sustainability of renewables for the world using the criteria of life-cycle cost, net energy ratio, resource constraint and greenhouse gas emissions. Renewable options for electricity generation and hydrogen generation for vehicles are assessed on the basis of these criteria. Life-cycle assessment (LCA) is carried out using SimaPro 6 LCA software. For electricity generation the base case considered is thermal power generation using coal. The options considered are wind energy, solar photovoltaics and biomass gasification. For hydrogen production three methods based on renewables (photovoltaic (PV)-electrolysis, wind energy conversion systems (WECS)-electrolysis and biomass gasification) are compared with the steam methane reforming (SMR) method. The renewable-based technologies seem to be sustainable on the basis of all criteria except the high life-cycle cost. In some cases, e.g., in biomass-based systems, land availability may constrain sustainability. Biomass is likely to be a sustainable solution only if marginal/scrub lands can be used for biomass plantation with adequate yield. However, this option needs to be studied to see if the net energy ratio is greater than one. It is found that hydrogen production by photovoltaic-electrolyzer can be a non-renewable method at low load factor (~0.15) and PV module efficiency (10 %). However, this method is renewable for higher values of load factor and PV module efficiency. The framework developed in this paper can form the starting-point for sustainability analysis.

Effective efficiency of PV modules under field conditions

AbstractThe conversion efficiency of photovoltaic modules varies with irradiance and temperature in a predictable fashion, and hence the effective efficiency averaged over a year under field conditions can be reliably assessed. The suggested procedure is to define the efficiency versus irradiance and temperature for a specific module, collect the local irradiance and temperature data, and combine the two mathematically, resulting in effective efficiency. Reasonable approximations simplify the process. The module performance ratio is defined to be the ratio of effective efficiency to that under standard test conditions. Variations of the order of 10% in this factor among manufacturers, primarily the result of the differences in effective series resistance and leakage conductance, are not unusual. A focus on these parameters that control the effective efficiency should provide a path to PV modules with improved field performance. Copyright © 2006 John Wiley & Sons, Ltd.

Efficiency and degradation of a copper indium diselenide photovoltaic module and yearly output at a sunny site in Jordan

The present work mainly deals with the testing and modeling of a commercially-available copper indium diselenide (CIS) ST40 module from the former Siemens Solar Industries (SSI). For this purpose, a large quantity of current/voltage characteristics were measured in the Paul Scherrer Institute (PSI)’s photovoltaic test-facility under different cell temperatures, solar irradiation and air mass, AM, conditions. They were used to develop a semi-empirical efficiency model to correlate all measured data sets. The goal was to make available a model, allowing quick and accurate calculation of the performance of the CIS module under all relevant operating conditions. For the undegraded state of the module, the efficiency model allowed us to deduce the efficiency at Standard Test Conditions, STC, and its temperature coefficient at STC, which were 11.58% and minus 0.050%/°C, respectively. The output of the undegraded module under STC was found to be 42.4 W, i.e., 6% higher than specified by the manufacturer (40 W). Furthermore, the efficiency does not decrease with increasing air mass. At a cell temperature of 25 °C and a relative air mass of 1.5, the module has a maximum in efficiency of 12.0% at an irradiance of about 650 W/m 2. This indicates that the series-resistance losses become significant at higher irradiances. Hence, improving the transparent conducting oxide (TCO) electrode on the front side of the cells might lead to a higher output at high irradiances. Identical testing and modeling were repeated after having exposed the module to real weather conditions for one year. We found that the STC efficiency was reduced by 9.0%, from 11.58 down to 10.54%. The temperature coefficient of the efficiency had changed from minus 0.050 %/°C to minus 0.039%/°C. These results indicate possible chemical changes in the semiconductor film. The output of the module at STC was reduced by 9.0% from 42.4 W down to 38.6 W. Using meteorological data from a sunny site in the South of Jordan (Al Qauwairah) and the efficiency model presented here allows us to predict the yearly electricity yield of the CIS module in that area. Prior to degradation, the yield was found to be 362 kWh/m 2 for the Sun-tracked module; and 265 kWh/m 2 for the fix-installed module (South-oriented, at an inclination angle of 30°). After degradation the corresponding yields were found to be 334 and 241 kWh/m 2; meaning losses of 8.4% and 9.5%, respectively. (Note: all units of energy, kWh, are referred to the active cell area.) Having available efficiency models for other module types, similar predictions of the yield can be made, facilitating the comparisons of the yearly yields of different module types at the same site. This in turn allows selecting the best module type for a particular site.

MODELING OF ELECTRICAL CHARACTERISTICS OF PHOTOVOLTAIC POWER SUPPLY SOURCES

The photovoltaic (PV) generators are a major element of PV power systems and they are characterized by a low conversion ratio. This accounts for the necessity to study the current-voltage and power-voltage characteristics of PV sources in order to obtain maximum power output when there are changes both in the modules themselves and in the environment where they operate. In this paper the classical and the modified single-diode models have been used to model the electrical characteristics of PV cells and modules. Mathcad software package has been used for the modeling. The impact of solar radiation, temperature and shading both on electrical characteristics and on the PV cells and modules efficiency has been studied.

A new correlation between photovoltaic panel's efficiency and amount of sand dust accumulated on their surface

The accumulation of dust particles on the surface of photovoltaic (PV) panel greatly affects its performance especially in the dusty areas. In the present work, an experimental and theoretical study has been carried out to investigate the effect of sand dust concentration on the efficiency of PV panels. A stand-alone PV system is designed to carry out this work. The I–V characteristics have been measured simultaneously for both clean and dusty modules. It has been found that the short circuit current and the maximum output power decrease significantly as dust particles start to accumulate on the panel surface up to a concentration of 1 g/m2, but the rate of decrease is slower for concentrations beyond that value. The reduction in short circuit current in one sample of study is found to be ∼40%, whereas it is ∼34% in the maximum output power. In contrast, it is stated that the open circuit voltage is not sensitive to sand dust accumulation. A significant degradation in the efficiency of PV modules is observed for sand dust accumulation up to 1 g/m2. A linear relation has been proposed to correlate the degradation in efficiency to the amount of sand dust accumulated on the module surface. This relation can help PV system designers to reliably predict the effect of sand dust accumulation on PV module efficiency under real environmental conditions.

ASSESSMENTS ON THE MULTIJUNCTION SOLAR CELLS PHOTOELECTRIC EFFICIENCY RELATED TO THE SEMICONDUCTOR BAND GAP AND OUTDOOR CONDITIONS

The solar cell photoelectric efficiency is a concept introduced to assess the energy conversion process of photons into electron-hole pairs. A study on the correlation between photoelectric efficiency and semiconductor materials band gap of multijunction solar cells is presented. This is based on an integrated computer model used to perform the simulations over solar standard spectrum AM1.5G as well as a non-standard case, which includes the cells operating in outdoor conditions. We find that over a diffuse solar flux, the solar cell photoelectric efficiency increases whenever the cells are made from a semiconductor material with band gap higher than that optimized over the AM1.5G spectrum. Consequently, this opens a new possibility to increase the photovoltaic modules efficiency.

A Study on Simulations of the Power Output and Practical Models for Building Integrated Photovoltaic Systems

With the rapid increase in Building Integrated Photovoltaic (BIPV) systems and the popularity of photovoltaic (PV) applications, a simple but accurate model to calculate the power output of PV modules is crucial for evaluating systems. In addition, in the analysis of energy payback, two factors, the power output (maximum power output) model of PV modules and the representative local weather data, affect calculations of the energy savings and the payback time of BIPV systems. Most studies take the efficiency of PV modules as constant when calculating the energy payback time of PV systems, and ignore the influence of solar radiation and temperature on the results of the calculation. This study tries to develop one simple, practical, yet more accurate model for describing the characteristics of the power output of PV modules. It develops a model for describing the I-V characteristics of PV modules according to the equivalent circuits of solar cells, by which an accurate but complicated model of the maximum power output (MPO) can be achieved. Taking this MPO model as a benchmark, two other application models from other studies are evaluated and examined. One simplified application model for describing the maximum power output of PV modules is then derived from the results of the simulation. Once the solar radiation on PV panels and the ambient temperature are known, the power output of BIPV systems or PV systems can be calculated accurately and easily.

Low light conditions modelling for building integrated photovoltaic (BIPV) systems

The low irradiance efficiency of photovoltaic modules is important to the optimization of BIPV systems. When photovoltaic modules are integrated into a building, architectural design considerations compete with maximizing photovoltaic energy production. As a result, BIPV arrays are often not facing south and are frequently mounted vertically. Under these conditions, a greater portion of the total sunlight striking the array is diffuse or at high angles of incidence. In northern latitudes a significant amount of the total yearly energy is produced at low light levels. A grid-connected array of BIPV modules integrated into the BCIT Technology Centre building in Burnaby, B.C. was used for assessing the accuracy of an energy performance model developed for BIPV systems. The BIPV system uses AC modules and a computerized data acquisition system for monitoring the performance of modules and inverters. The performance model was developed from analysis of the open circuit voltage, maximum power point voltage and maximum power point current of the individual modules comprising the BIPV array. The algorithm for calculating power output of the photovoltaic array is derived from the ideal diode equation using the single diode model of a photovoltaic cell. An empirically derived parameter modifies the equation. Once the parameters for different module technologies are established, it is possible to compare their annual performance in a BIPV system.

Influences of Solar Incident Angle on Power Generation Efficiency of PV Modules under Field Conditions

In this report, we examined influences of solar incident angle on the power generation efficiency of photovoltaic (PV) modules based on a measurement, during winter, at Kagoshima in Japan (31.570°N, 130.545°E). It was indicated that the power generation efficiency of PV modules deteriorates with time depending on the solar incident angle, and that there are cases where the power generation efficiency sharply drops if the incident angle exceeds 60° and the reflectance of cover glass exceeds 0.2. Such drop of power generation efficiency dependent on incident angle clearly appears at clear time when the proportion of direct components of solar radiation increases. Furthermore, it was pointed out that the average value of power generating efficiency during winter including all weather conditions produces differences of 10% or so, depending on the difference of average value during the period of incident angle.

Life‐cycle assessment of photovoltaic modules: Comparison of mc‐Si, InGaP and InGaP/mc‐Si solar modules

AbstractA higher conversion efficiency of photovoltaic modules does not automatically imply a lower environmental impact, when the life‐cycle of modules is taken into account. An environmental comparison is carried out between the production and use phase, except maintenance, of an indium–gallium–phosphide (InGaP) on multicrystalline silicon (mc‐Si) tandem module, a thin‐film InGaP cell module and a mc‐Si module. The evaluation of the InGaP systems was made for a very limited industrial production scale. Assuming a fourfold reuse of the GaAs substrates in the production of the thin‐film InGaP (half) modules, the environmental impacts of the tandem module and of the thin‐film InGaP module are estimated to be respectively 50 and 80% higher than the environmental impact of the mc‐Si module. The energy payback times of the tandem module, the thin‐film InGaP module and the mc‐Si module are estimated to be respectively 5.3, 6.3 and 3.5 years. There are several ways to improve the life‐cycle environmental performance of thin‐film InGaP cells, including improved materials efficiency in production and reuse of the GaAs wafer and higher energy efficiency of the metalorganic chemical vapour deposition process. Copyright © 2003 John Wiley & Sons, Ltd.

The impact of efficiency on area-related system costs

There is an ongoing debate within the photovoltaic (PV) industry as to how significantly PV module efficiency impacts the installed cost of a PV system. This paper examines key factors and, through examples, concludes that under current economics, efficiency is generally not the dominant factor affecting overall cost. However, the paper also notes a variety of exceptions in which efficiency can become a principal cost driver. Therefore, in the absence of a reliable rule of thumb to guide design decisions, the paper identifies the technical and economic conditions under which efficiency has the strongest impact on overall cost. Copyright © 1999 John Wiley & Sons, Ltd.

Humidity: A factor in the appropriate positioning of a photovoltaic power station

Humidity is an ambient parameter which refracts, reflects and diffracts the direct visible solar radiation. This dispersion effect results in deterring the reception of the direct component of solar radiation by water vapour particles present in the atmosphere. Tropical Sudan Savannah region is known to be a hot climatic area with a highly humidified atmosphere. This paper investigates the effect of humidity on the reception of solar radiation and the resulting effect on the generated electrical power in this climatic region. A monocrystalline silicon photovoltaic module containing 33 cells connected in series was used for the investigation. The module open-circuit voltage (V OC) and short-circuit current (I SC) variations with irradiance level have been established. The variation of solar radiation intensity with humidity has also been analysed. Result indicates a little variation of the V OC with irradiance. On the other hand, the I SC has been observed to vary largely with the irradiance level. Also, the analysis of the variation of humidity with irradiance level reveals a non-linear relationship. This shows the dependence of photovoltaic module efficiency not only on the type of cell structure but also on the maximum irradiance and consequently the humidity of the surrounding.