Effect of high irradiation on photovoltaic power and energy

Solar photovoltaics (PV) is a promising solution to combat against energy crisis and environmental pollution. However, the high manufacturing cost of solar cells along with the huge area required for well‐sized PV power plants are the two major issues for the sustainable expansion of this technology. Concentrator technology is one of the solutions of the abovementioned problem. As concentrating the solar radiation over a single cell is now a proven technology, so attempt has been made in this article to extend this concept over PV module. High irradiation intensity from 1000 to 3000 W/m² has been investigated to measure the power and energy of PV cell. The numerical simulation has been conducted using finite element technique. At 3000 W/m² irradiation, the electrical power increases by about 190 W compared with 63 W at irradiation level of 1000 W/m². At the same time, at 3000 W/m² irradiation, the thermal energy increases by about 996 W compared with 362 W at 1000 W/m² irradiation. Electrical power and thermal energy are enhanced by about 6.4 and 31.3 W, respectively, for each 100‐W/m² increase of solar radiation. The overall energy is increased by about 179.06% with increasing irradiation level from 1000 to 3000 W/m². It is concluded that the effect of high solar radiation using concentrator can significantly improve the overall output of the PV module.     

硅太阳电池工程用数学模型

为实现光伏电站、光伏户用系统、光伏水泵系统、"风 -光-柴-蓄"等各种涉及太阳能光伏利用复合能源系统的设计、数字仿真和动态模拟实验 ,以电子学理论为基础,讨论了满足工程应用精度且便于运算的太阳电池数学模型.该模型的特点是仅采用生产厂家为用户提供的太阳电池组件在标准测试条件(STC)下测出的I sc、Voc、Im、Vm作为参数,通过引入相应系数来考虑环境影响,并给出系数的典型值.实验结果表明模型的误差一般都在6%以下,可以满足对绝大多数工程项目进行物理模拟的精度要求.     

A novel hybrid photovoltaics/thermoelectric cooler distillation system

In this paper, a novel hybrid photovoltaics/thermoelectric cooler (PV/TEC) distillation system has been introduced. The limitation for distillation system working under hot arid climate is the heat removal required for the condensation process. The novelty of the proposed system is that it utilizes TEC to improve the condensation process. The proposed system composed of two porous layers separated by an air gap. The upper porous layer is installed at the back of a PV module; the lower porous layer is installed at the top of a TEC modules layer. This system can provide the demand of electricity and potable water for those people who live in rural areas (using one unit or more). The proposed system prevents PV module from overheating and actively enhancing the condensation process of the evaporated water. A steady‐state mathematical model has been proposed. This model was solved and simulated by equation solver software. Wind speed, solar radiation, and ambient temperature effect on the system performance were simulated and discussed. Results showed that the maximum productivity of the system reached an ambient temperature of 298 K, solar radiation of 1000 W/m² and wind speed of 5.5 m/s. The maximum yield of the system was 4.2 kg of distilled water per day with a net electrical output power of 73 W with an overall efficiency of 57.9% and PV cell efficiency of 12.32%.     

Economic analysis of small photovoltaic facilities and their regional differences

Small grid‐connected photovoltaic (PV) facilities in Spain receive either a premium of 0.36€ kWh^?1 over the average price on the power market or a fixed price of 0.40€ kWh^?1. However, legislation on this matter (Royal Decree 2818/98) requires a periodic review of these figures. The basis of on‐going revision of these prices has been their profitability. However, the economic success of such PV facilities is clearly affected by the amount of solar radiation at the site where they are located. Since Spain is between latitudes 44 and 36° in the northern hemisphere, the feasibility of these systems must be analysed for different regions. Two different models have been used to produce the required input data for such an analysis: a model that generates typical solar radiation years and temperatures taken from satellite images and an empirical model for the prediction of daily power produced by a grid‐connected photovoltaic system. From the results of this regional economic analysis, it may be concluded that the existing prices are insufficient in and of themselves to make these small grid‐connected systems profitable anywhere in Spain. To guarantee the economic feasibility of these PV installations in any given location, the fixed price paid for the electricity should be around 0.93€ kWh^?1. Nevertheless, if the Government were to double the current fixed price, in consideration of the slow increase in the PV market in recent years, this would mean that small grid‐connected installations would become profitable in at least 77% of the Spanish territory. Copyright © 2004 John Wiley & Sons, Ltd.     

Investigating the effects of solar modelling using different solar irradiation data sets and sources within South Africa

When designing a solar photovoltaic (PV) system, the main aim of the designer is to optimise the system through the correct choice in sizing of system components (i.e.: size of PV array versus number of batteries for storage), whilst at the same time keeping the overall systems costs as low as possible. The choice of data provider and method for measuring the solar irradiance data in W/m² for a specific geographical location is therefore a critical determinant to ensure maintenance of the desired level of accuracy for the system design. The use of a data set which either over predicts or under predicts the amount of available solar irradiation at a specific location will therefore affect the electrical performance of the system, as the real world conditions may differ considerably to the data set used in the modelling of the system design. This paper specifically deals with the modelling of an off-grid photovoltaic power supply system using three different sources of solar irradiance data for two specific geographical locations within South Africa. The principal aim of the paper is to show that satellite data over-estimates solar irradiance and hence underestimates the initial cost of a solar PV system needed to meet the load in question.     

Thermal management of solar cells using a nano‐coated heat pipe plate: an indoor experimental study

With temperature increasing, the photovoltaic efficiency of solar cells is reduced significantly. Such an efficiency loss may offset the efficiency improvement because of the development of the photovoltaic technology. This paper provides a novel approach for efficiency loss recovery of solar cells. Specifically, a nano‐coated heat pipe plate was integrated with the solar panel to remove heat from the hotspots on solar cells. This study concerns the indoor experiments of a commercial solar cell thermally managed with a heat pipe plate. The temperature rise and non‐uniformity on the solar panel were quantified in different light irradiances. With thermal management by the heat pipe plate, the solar panel shows a temperature‐rise reduction of 47–50%. This implies that half of the efficiency loss of the solar cell can be recovered. In addition, the temperature variation within the solar panel is reduced to 1.0–2.5 °C, which is beneficial in prolonging the longevity of the solar cell. In the experiments, the heat pipe plate can provide a cooling flux of 380 W/m² with light irradiance below 1000 W/m². By incorporating the heat pipe plate with a water jacket, the heat removal flux could be improved to 600 W/m², leading to a solar cell temperature of a few degrees higher than the ambient. Copyright © 2016 John Wiley & Sons, Ltd.     

A multi-step ahead global solar radiation prediction method using an attention-based transformer model with an interpretable mechanism

The conventional multi-step ahead solar radiation prediction method ignores the time-dependence of a future solar radiation time series. Therefore, according to sequence-to-sequence (seq2seq) model theory, this paper proposes the seq2seq long- and short-term memory model (seq2seq-LSTM), the seq2seq-LSTM model with an attention mechanism (seq2seq-at-LSTM), and a transformer model, which consists only of the attention mechanism. The hourly global solar radiation data between 2016 and 2018 from Shaanxi, China, is used to train and validate the models. The results show that the introduction of the attention mechanism can effectively improve the prediction accuracy of the seq2seq-LSTM model. However, the model is still not very good at capturing the long-distance dependence of the solar radiation time series due to the inherent properties of LSTM. In comparison, the transformer model, which is based entirely on the attention mechanism, performs much better at capturing the long-distance dependence of the solar radiation time series. Furthermore, as the number of time-steps increases, the performance of the solar radiation prediction decreases relatively smoothly and slowly. The obtained average coefficient of determination, root mean square error (RMSE), relative RMSE, and mean bias error are 0.9788, 72.91 W/m², 25.25%, and 38.35 W/m², respectively. In addition, the average skill score of the transformer model is around 44.9%, which is 20.54% higher than that of the seq2seq-at-LSTM model and about 40.84% higher than that of the seq2seq-LSTM model. Besides, the use of the attention mechanism can explain the improved prediction compared to other models. This model developed in this study could also be used for predictions in other fields, such as wind energy predictions and building energy predictions.     

Solar-driven high temperature hydrogen production via integrated spectrally split concentrated photovoltaics (SSCPV) and solar power tower

Hydrogen production can be achieved via combined concentrated photovoltaic (CPV) and concentrated solar power (CSP) in which concentrated radiation is spectrally split and then converted in a photovoltaic receiver and a thermal absorber. This study thus proposes an innovative solar process design integrating both thermal and quantum components of solar energy while providing a complete assessment of its global performance to demonstrate its practical interest. A stand-alone solar-to-hydrogen path was modeled and numerically simulated, which was both electrically and thermally supplied by a solar power generation unit to feed the electrolyzer power utilization unit with enhanced solar-to-hydrogen conversion efficiency. Following balance of plant (BoP), the heliostat field and cavity receiver were designed to match the entire system in which the receiver only intercepts a definite range of infrared wavelength while the rest is converted by separately insulated PV cells. Moreover, dichroic reflectors and optimum cutoff wavelength were applied to fulfill separate optimization and heat load reduction of each solar cell. Finally, the solid oxide electrolysis cell (SOEC) was designed to utilize the generated thermal and electrical power appropriately. In best case scenario, a solar-to-hydrogen conversion efficiency of 36.5% was achieved under 899 W/m² direct normal irradiance (DNI) and 1000 suns concentration. The solar plant outputs at this operating point were 850 g/h H₂ and 6754 g/h O₂. Further improvement in efficiency can be achieved through alignment in regard to the site location and annual insolation variation.     

Performance evaluation of photovoltaic/thermal–HDH desalination system

The efficiency of photovoltaic (PV) panel drops with increase in cell temperature. The temperature of the PV panel can be controlled with various cooling techniques. In the proposed work the PV panel is cooled by circulating water and the recovered heat energy is used to run a humidification and dehumidification desalination to produce distilled water from sea water (or) brackish water. This work deals with a detailed analysis of performance of combined power and desalination (Photovoltaic/Thermal–Humidification and Dehumidification) system. A mathematical model of PV/thermal–humidification dehumidification plant was developed and simulations were carried out in MATLAB environment. The performance of photovoltaic/ thermal desalination (Photovoltaic/Thermal–Humidification and Dehumidification) system was investigated under various solar radiation levels (800–1000 W/m²). For each solar radiation level the effect of mass flow rate of coolant water (30–110 kg/h) on water outlet temperature, PV efficiency, PVT thermal efficiency, distilled water production, and plant efficiency was studied. Results show that under each solar radiation level increasing coolant flow rate increases efficiency of PV panel and reduces the plant efficiency. The highest PV efficiency (16.598%) was reached under 800 W/m² at mass flow rate of 110 kg/h and the highest plant efficiency (43.15%) was reached under 800 W/m² at a mass flow rate of 30 kg/h. The maximum amount of distilled water production rate (0.82 L/h) was reached under 1000 W/m² at water mass flow rate of 30 kg/h.     

A novel choice for the photovoltaic–thermoelectric hybrid system: the perovskite solar cell

Most of the recent studies about the photovoltaic cell‐thermoelectric generator (PV‐TEG) hybrid system pay their attention to silicon PV cells. This paper is to estimate the feasibility and features of the integrated system consisting of the emerging perovskite solar cells and thermoelectric modules. The results in this paper show that the temperature coefficient of the perovskite solar cell is lower than 2‰. Because of such a lower temperature coefficient, the efficiency of the perovskite solar cell‐TEG hybrid system can amount to 18.6%, while the efficiency of the single perovskite solar cell is 17.8%. Therefore, the perovskite solar cell is a reasonable choice for the PV‐TEG hybrid system. By altering the thermal concentration, the volume of the TEG material can be decreased, and the cost of the hybrid system can be remarkably reduced. To study the influence of the thermal concentration on the performance of the hybrid system, a three‐dimensional numerical model of the hybrid system is developed in this paper. When the thermal concentration ration is lower than 100, the temperature drop is lower than 3 K, and the decline in the conversion efficiency caused by the thermal concentration can be neglected for the proposed PV‐TEG hybrid system. Copyright © 2016 John Wiley & Sons, Ltd.     

Investigation of solar hybrid system with concentrating Fresnel lens,photovoltaic and thermoelectric generators

An experimental model of a solar hybrid system including photovoltaic (PV) module, concentrating Fresnel lens, thermoelectric generator (TEG), and running water heat extracting unit was created and studied. The PV module used was of c‐Si and TEG of Bi₂Te₃; the Fresnel lens (solar concentrator) and TEG share an optical train, whereas PV module was illuminated separately with non‐concentrated light. Heat extracting unit operated in thermo siphon mode. In climatic conditions of Mexico (Queretaro, 20^o of North latitude, summer time), the Fresnel lens accepted 120 W of solar radiation power, and the system generated 7.0 W of electric power and 30 W of thermal one. The discussion is made of the possible characteristics of a hypothetical hybrid system where all its elements share the same optical train. Copyright © 2016 John Wiley & Sons, Ltd.     

Research on the influence of PV cell to thermal characteristics of photovoltaic/thermal solar system

In the paper, we analyzed internal thermal transmission characteristics of water‐heating photovoltaic/thermal (PV/T) solar collector covered by photovoltaic (PV) cell, established photothermal conversion model of PV/T solar system, and analyzed the influence of PV cell coverage to photothermal characteristics of PV/T solar system. Results show that the thermal efficiency of PV/T solar system by optimizing PV cells coverage can reach 68%. In addition, by designing four water‐heating PV/T solar system prototypes with PV cell coverage of 0.4, 0.56, 0.7, and 0.82, respectively, we conducted experimental researches for the four prototypes and found that the four prototypes can achieve thermal efficiencies of 58%, 51%, 64%, and 67%, respectively, in heating 250 L of water to 50°C. The experiment results are consistent with theoretical analysis results, indicating that it is feasible to improve thermal characteristics of PV/T solar system by optimizing PV cell coverage. Copyright © 2017 John Wiley & Sons, Ltd.     

聚光型光伏系统光电耦合性能研究

针对复合抛物面聚光型光伏（PV-CPC）系统,建立光电耦合模型,模拟不同聚光比下光伏阵列表面太阳辐照度分布规律,并比较3种不同网格电路模型的适用性和准确性。结果表明：采用离散网格照度方法模拟精度最高,同时聚光型光伏系统在提升发电功率的同时也导致一定效率损失。当聚光比增大时,光伏阵列表面辐照度值及不均匀性增大,最佳聚光面处的照度分布均匀性优于CPC出口处;光伏阵列的发电功率和效率与太阳总辐照度呈正相关、散射比呈负相关关系。     

Evaluation of PV output in terms of environmental impact based on mathematical and artificial neural network models

This paper presents different prediction models for a grid‐connected photovoltaic (GCPV) system based on long‐term data sets. A 1.4 kW GCPV installed in Sohar, Oman, where measurements of the electrical and environmental parameters are taken every second for 5 years (from May 2014 to April 2019) to reduce uncertainty and improve the proposed model's accuracy. The highest power and energy measured from the GCPV are 1180 W and 245.8 kWh, respectively. Mathematical regression and cascade‐feed forward propagation (CFNN) models for PV current, voltage, and power were proposed in terms of environmental impact. A NeuroSolutions package was used to propose GCPV models for electrical quantities. An evaluation criterion is defined, in this study, to assess the system's performance. The proposed models show excellent agreement with the measured experimental data. However, CFNN shows a superior accuracy compared with empirical and regression proposed models. The two models have proposed a dispute, but the model relating the solar irradiation and ambient temperature to GCPV current is more accurate. To evaluate and validate the proposed CFNN models, mean square error, MAE, root mean square error, and R² metrics have been used as a criterion and compared with different artificial neural networks models in the literature. The proposed CFNN is found to give the most accurate results in terms of MSE = 0.0007, MAE = 0.4310, and RMSE = 0.0290 and highest accuracy R² = 0.9999, which shows the effectiveness and feasibility of the proposed models.     

Evaluation of a cloud cover based model for estimation of hourly global solar radiation in Western Canada

Cloud cover based solar radiation models are relatively simple and convenient as the models require the input of cloud cover data which are mostly available from the meteorological stations. In this study, the performance of a cloud cover based solar radiation model (Kasten–Czeplak model) with original or locally fitted coefficients was evaluated for estimating the hourly global solar radiation for four different locations in Western Canada. The average value of R², mean bias error, and root mean square error are 0.69, ?61.6, and 157.9?W?m^?2, respectively, for the model with original coefficients, whereas 0.82, 4.4, 107.1?W?m^?2 with locally fitted coefficients. Results show that the Kasten–Czeplak model with locally fitted coefficients satisfactorily estimated the hourly solar radiation of four different locations in Western Canada. Also, the results indicate that the model with original coefficients has very limited accuracy under intermediate cloud cover conditions.     

Critical factors affecting the photovoltaic characteristic and comparative study between two maximum power point tracking algorithms

This paper presents the characterization and the modeling of the electric characteristics of currentvoltage and power–voltage of the photovoltaic (PV) panels. The philosophy behind digital simulation of solar energy systems is that experiments which normally should be done on real systems under high assembling costs can be done numerically in a short time on a computer, thus saving time and investments. The electric parameters of PV cells and the optimal electric quantities of PV panels have been analyzed (voltage and power) according to the meteorological variations (Temperature, solar irradiation …). The obtained results show that the diode parameters of the PV cells depend on solar irradiation: the current saturation increases with solar irradiation. This induces a decrease of the optimal voltage with solar irradiation; when the solar irradiation varies from 600 W/m² to 1000 W/m². By taking into consideration all the modeling results, the electric behavior of the cells association in parallels or in series, as well as the aging of a PV panel have been analyzed. Moreover, a comparative study between two types of MPPT techniques that are used in photovoltaic systems to extract the maximum power have been introduced which are Perturb and Observe (P &O) and Incremental Conductance (INC).     

Economic perspective of PV electricity in Oman

Solar and wind energies are likely to play an important role in the future energy generation in Oman. This paper utilizes average daily global solar radiation and sunshine duration data of 25 locations in Oman to study the economic prospects of solar energy. The study considers a solar PV power plant of 5-MW at each of the 25 locations. The global solar radiation varies between slightly greater than 4 kWh/m²/day at Sur to about 6 kWh/m²/day at Marmul while the average value in the 25 locations is more than 5 kWh/m²/day. The results show that the renewable energy produced each year from the PV power plant varies between 9000 MWh at Marmul and 6200 MWh at Sur while the mean value is 7700 MWh of all the 25 locations. The capacity factor of PV plant varies between 20% and 14% and the cost of electricity varies between 210 US$/MWh and 304 US$/MWh for the best location to the least attractive location, respectively. The study has also found that the PV energy at the best location is competitive with diesel generation without including the externality costs of diesel. Renewable energy support policies that can be implemented in Oman are also discussed.     

Long-term field test of solar PV power generation using one-axis 3-position sun tracker

The 1 axis-3 position (1A-3P) sun tracking PV was built and tested to measure the daily and long-term power generation of the solar PV system. A comparative test using a fixed PV and a 1A-3P tracking PV was carried out with two identical stand-alone solar-powered LED lighting systems. The field test in the particular days shows that the 1A-3P tracking PV can generate 35.8% more electricity than the fixed PV in a partly-cloudy weather with daily-total solar irradiation H_T = 11.7 MJ/m² day, or 35.6% in clear weather with H_T = 18.5 MJ/m² day. This indicates that the present 1A-3P tracking PV can perform very close to a dual-axis continuous tracking PV (Kacira et al., 2004). The long-term outdoor test results have shown that the increase of daily power generation of 1A-3P tracking PV increases with increasing daily-total solar irradiation. The increase of monthly-total power generation for 1A-3P sun tracking PV is between 18.5-28.0%. The total power generation increase in the test period from March 1, 2010 to March 31, 2011, is 23.6% in Taipei (an area of low solar energy resource). The long-term performance of the present 1X-3P tracking PV is shown very close to the 1-axis continuous tracking PV in Taiwan (Chang, 2009). If the 1A-3P tracking PV is used in the area of high solar energy resource with yearly-average H_T > 17 MJ/m² day, the increase of total long-term power generation with respect to fixed PV will be higher than 37.5%. This is very close to that of dual-axis continuous tracking PV.The 1A-3P tracker can be easily mounted on the wall of a building. The cost of the whole tracker is about the same as the regular mounting cost of a conventional rooftop PV system. This means that there is no extra cost for 1A-3P PV mounted on buildings. The 1A-3P PV is quite suitable for building-integrated applications.     

Estimation of internal heat transfer coefficients of a hybrid (PV/T) active solar still

In this paper, an attempt is made to estimate the internal heat transfer coefficients of a deep basin hybrid (PV/T) active solar still. The estimation is based on outdoor experimental observation of hybrid (PV/T) solar still for composite climate of New Delhi (latitude 28°35′N and longitude 77°12′E). The internal heat transfer coefficients are evaluated by using thermal models proposed by various researchers. The comparison of hourly yield predicted using various thermal models to the experimental has also been carried out by evaluating the correlation coefficient and percentage deviation. It is observed that, Kumar and Tiwari model (KTM) better validate the results than the others model. The average annual values of convective heat transfer coefficient for the passive and hybrid (PV/T) active solar still are observed as 0.78 and 2.41 W m⁻² K⁻¹, respectively at 0.05 m water depth.     

The potential and economic viability of solar photovoltaic power in Ghana

In this study, the potentiality and economic viability of solar photovoltaic (PV) in Ghana was assessed using RETScreen software. 5 MW of grid-connected solar PV power system using SunPower SPR-320E-WHT-D PV module can be harnessed from Navrongo, Bawku, Wa, Tema, Bolgatanga, Axim, Salaga, Kintampo, Kete Krachi, Tamale, Hohoe, Koforidua, Ejura, Takoradi, Bole, Sunyani, Bibiani, Cape coast, Prestea, and Akuse, which requires US$17,752,179 of investment capital and 25,313 m² of land for PV installation. The potential of 5 MW grid-connected PV development for Accra, Kumasi, Wenchi, and Tafo are limited. However, there are solar PV energy potentials for low-capacity PV modules for these locations. Investing in solar photovoltaic technology is capital intensive in a developing country like Ghana. However, Government’s effort to provide incentives like subsidies and creating the economic environment for private sector investment will boost investment possibilities of renewable energy in Ghana, which can help in curbing the recent power outages and load shedding, thereby increasing productivity and economic resilience.