Thermal performance of a solar pressure cooker based on evacuated tube solar collector

This paper presents the thermal performance of a community type solar pressure cooker based on evacuated tube solar collector. The developed design of solar pressure cooker has separate parts for energy collection and cooking unit and both are coupled by heat exchanger. The paper has presented the performance results of experimental study conducted on solar pressure cooker and a simulation model has been developed for predicting the cooker performance under a variety of operating and climatic conditions. The theoretical model is validated against the experimental results. The obtained results have suggested a possibility of several batches of solar cooking on a clear sunny day under typical conditions of Delhi.     

基于双指数模型的太阳电池输出特性计算机模拟

以双指数形式太阳电池理论模型为基础，用实验数据拟合太阳电池的I-V特性。然后利用获得的重要待定参数的拟合值对太阳电池的I-V和P-V特性计算机模拟，并分析了它们对太阳电池性能的不同影响机制。     

On the relevance of mass transport in thin layer nanocrystalline photoelectrochemical solar cells

A comprehensive analysis of the diffusion and migration processes in the steady state operation of mesoporous photoelectrochemical solar cells has been attempted. The dye sensitized TiO₂ nanocrystalline solar cell utilizing the iodide/triiodide redox mediator serves as the system of reference. The porous nature of the semiconductor plays an important role in this process. Efficient design characteristics for such cells are obtained in order to minimize, e.g., the concentration overpotential, thus minimizing one of the sources of loss in such cells.The models developed illustrate operational aspects such as concentration profiles in the cell under the conditions relevant to existing systems, the limiting or maximum possible currents in the nanocrystalline PEC device, and the anticipated mass-transfer overpotential as a function of current density. The geometric and structural properties of the photoanode as well as the relative position of the counter-electrode with respect to the mesoporous film photoanode can be better exploited towards an efficient operation of the solar energy conversion device.The repercussions of the variation of solar cell design parameters are illustrated experimentally by the performance of practical application devices. These serve as evidence towards the plausibility and the validity of a mass transfer model for the electrolyte function in nanocrystalline PECs.     

Thermal and technical analyses of solar chimneys

An analysis for the solar chimneys has been developed, aimed particularly at a comprehensive analytical and numerical model, which describes the performance of solar chimneys. This model was developed to estimate power output of solar chimneys as well as to examine the effect of various ambient conditions and structural dimensions on the power output. Results from the mathematical model were compared with experimental results and the model was further used to predict the performance characteristics of large-scale commercial solar chimneys. The results show that the height of chimney, the factor of pressure drop at the turbine, the diameter and the optical properties of the collector are important parameters for the design of solar chimneys.     

Experimental and theoretical study on a solar assisted CO2 heat pump for space heating

In this paper, a solar combi-system which consists of solar collector and a CO₂ heat pump is investigated experimentally and theoretically. Two experiments are primarily conducted to show the performance of this solar combi-system under different operation conditions. A system model is developed and validated in TRNSYS to analyze the influence of main components parameters. Subsequently, a multi-parameter optimization is carried out in GENOPT to obtain a final optimal result. The simulated results show that the optimized system can save 14.2% electricity and improve the solar fraction by 8%. The solar fraction of the optimized system can reach 71.1%. Finally, the optimized system performance is studied with the weather and load characteristics in Shanghai. Compared with the CO₂ HP heating system alone, the solar assisted system can save 1790.8 kWh electricity on the basis of year round operation.     

太阳电池的双指数简化模型

以太阳电池的双指数理论模型为研究对象,通过数值模拟的方法,建立太阳电池的简化模型,并利用太阳电池的实验数据进行了模拟分析.研究结果表明:以简化模型为基础,仅利用生产厂家为用户提供的产品在标准测试条件(STC)下测出的I∝、V∝、Im、Vm作为参数,能以较高的精度计算出太阳电池的,I-V特性,为太阳电池数学模型的工程应用提供了可能.     

Design nomogram for long-term performance prediction of Integrated Collector–Storage (ICS) solar water heater

The performance prediction of Solar Integrated Collector–Storage System (ICS) is determined in terms of generalized dimensionless grouped parameters. These dimensionless parameters are primarily a combination of physical characteristics representing thermal performance curves for solar ICS systems and include information readily available to a designer pertaining to dimensions, thermal characteristics and operating conditions. The inter-relation between these is summarised as a nomogram and helps in predicting the system performance graphically for a particular locality or it may be deduced from it by simple hand calculation. This method does not require a detailed knowledge of system parameters for predicting system performance, and an advantage of this method is that short-term performance data is used to predict long-term performance and solar fraction. A simulation model was developed using a transient one-dimensional analysis for a solar ICS system. Time-dependent heat transfer coefficients and thermophysical properties were taken in the present simulation. © 1998 John Wiley & Sons, Ltd.     

临近空间太阳电池模型修正与发电量预测研究

由于在飞行过程中,温度、辐照度和倾角变化都会对临近空间飞行器上太阳电池的输出功率及效率产生影响,该文利用太阳光模拟器及薄型晶体硅太阳电池,进行多组测量实验,得到在不同温度、辐照度和倾角条件下,太阳电池的短路电流、开路电压等参数,并通过与模型仿真结果进行对比,对已有太阳电池电模型进行修正,得到更接近真实飞行工况的临近空间飞行器用薄型晶体硅太阳电池的模型。最后,基于修正后的模型通过仿真对太阳电池阵列在临近空间的全天发电功率变化趋势进行预测,可为临近空间飞行器用太阳电池阵列设计与功率预测提供重要参考。     

太阳电池直流模型的计算机仿真

太阳电池特性由材料、设计和工艺决定，太阳电池直流模型则可描述其电特性。现有的测试方法不能直接测出模型参数，但容易获得太阳电池片实测Ｉ—Ｖ数据，采用最小二乘法拟合出模型参数，就可以建立模型参数与制造工艺的直观联系。本文对提高模型拟合的速度及精度的实现方法进行讨论，在计算机上实现快速拟合。     

Performance analysis of water cooled concentrated photovoltaic (CPV) system

The concentrated photovoltaic (CPV) system focuses solar radiation on the solar cells. CPV systems need to track the sun for keeping the reflected radiation focussed on the solar cell. A CPV module and its active water-cooling system are developed at the School of Energy and Environment, Southeast University, China and its performance has been reported here. This developed system has been used for testing the PV module's performance for different parameters such as operating temperature, power output, and efficiency. The experimental results show that the operating temperature of the CPV module under water cooling is reduced under 60 °C and therefore the efficiency of the CPV has increased and produced the more electric power output. The effect of water flow rate has been analyzed for the CPV efficiency and output.     

Exergetic optimization of flat plate solar collectors

In this paper, an exergetic optimization of flat plate solar collectors is developed to determine the optimal performance and design parameters of these solar to thermal energy conversion systems. A detailed energy and exergy analysis is carried out for evaluating the thermal and optical performance, exergy flows and losses as well as exergetic efficiency for a typical flat plate solar collector under given operating conditions. In this analysis, the following geometric and operating parameters are considered as variables: the absorber plate area, dimensions of solar collector, pipes' diameter, mass flow rate, fluid inlet, outlet temperature, the overall loss coefficient, etc. A simulation program is developed for the thermal and exergetic calculations. The results of this computational program are in good agreement with the experimental measurements noted in the previous literature. Finally, the exergetic optimization has been carried out under given design and operating conditions and the optimum values of the mass flow rate, the absorber plate area and the maximum exergy efficiency have been found. Thus, more accurate results and beneficial applications of the exergy method in the design of solar collectors have been obtained.     

Study on performance of solar assisted air source heat pump systems for hot water production in Hong Kong

This paper reports the investigation results on application of the solar assisted air source heat pump systems for hot water production in Hong Kong. A mathematical model of the system is developed to predict its operating performance under specified weather conditions. The optimum flow rate from the load water tank to the condenser is proposed considering both the appropriate outlet water temperature and system performance. The effect of various parameters, including circulation flow rate, solar collector area, tilt angle of solar collector array and initial water temperature in the preheating solar tank is investigated, and the results show that the system performance is governed strongly by the change of circulation flow rate, solar collector area and initial water temperature in the preheating solar tank.     

A new integrated single‐diode solar cell model for photovoltaic power prediction with experimental validation under real outdoor conditions

The output power prediction by a photovoltaic (PV) system is an important research area for which different techniques have been used. Solar cell modeling is one of the most used methods for power prediction, the accuracy of which strongly depends on the selection of cell parameters. In this study, a new integrated single‐diode solar cell model based on three, four, and five solar cell parameters is developed for the prediction of PV power generation. The experimental validation of the predicted results is done under outdoor climatic conditions for an Indian location. The predicted power by three models is found close to measured values within 4.29% to 4.76% accuracy range. The comparative power estimation analysis by these models shows that the three‐parameter model gives higher accuracy for low solar irradiance values <150 W/m², the four‐parameter model in the range of 150 to 500 W/m², and the five‐parameter model for >500 W/m². The present model is also compared with other models in literature and is found to be more accurate with less percentage error. The overall results also show that the power produced depends on temperature and solar radiation levels at a particular location. Thus, single solar cell model developed can be used with sufficient accuracy for power forecast of PV systems for any location worldwide. The follow‐up research areas are also identified.     

Investigation of parameters of photothermoconverter based on Si solar cells

A photothermoconverting unit based on thin (180 μm) high-efficiency solar cells manufactured by Sunoasis (the People’s Republic of China) has been developed, and its parameters have been investigated under the full-scale conditions of Tashkent. The output photovoltaic parameters of this photothermoconverting system have been studied under different temperatures; the temperature coefficients DUnl/DT and Dh/DT of the solar cells in a solar array are determined. The differences in the values of the temperature coefficients for the isolated solar cells and for those in a solar array are analyzed. A method to experimentally determine the “overheating” temperature of the solar cell incorporated in a solar array is proposed. The recommendations for further investigations are developed.     

Metal-insulator-semiconductor solar cell under gamma irradiation

The performance of a home made MIS–p-Si solar cell was experimentally studied under various gamma irradiation doses (up to 500 Mrad). The effect of radiation dose on the I−V and C−V characteristics was investigated in this work. The obtained results showed that all the output parameters of the cells under investigation were degraded with gamma radiation exposure. In addition, the effects of fabrication conditions (metal thickness and adding of antireflection coating) on the cell output parameters were also investigated.     

Simulated Annealing algorithm for photovoltaic parameters identification

A Simulated Annealing based approach is proposed in this paper for optimal estimation of solar cell model parameters. Different solar cell models, namely single diode, double diode, and photovoltaic module, are used in this study to verify the proposed approach outcomes. The developed technique is used to solve a transcendental function that governs the current–voltage relationship of a solar cell, as no direct general analytical solution exists. Several cases were investigated to test and validate the consistency of accurately estimating various parameters of different solar cell models. Comparative study among different parameter estimation techniques is presented to show the effectiveness of the developed approach. Furthermore, statistical analyses are carried out to measure the accuracy of the estimated parameters and model suitability.     

Analysis of a solar chimney power plant in the Arabian Gulf region

A simplified thermodynamics analytical model for steady airflow inside a solar chimney is performed. A simplified Bernoulli equation combined with fluid statics and ideal gas equation was implemented and solved using EES solver to predict the performance of the solar chimney power plant. The analytical model matched the experimental data and numerical study available in the literature. The developed analytical model was used to evaluate the effect of geometric parameters on the solar plant power generation. The analysis showed that chimney height and turbine pressure head are the most important physical variables for the solar chimney design. The study showed that second-law efficiency has non-monotonic relation with turbine pressure head. The model shows that second-law efficiency and power harvested increase with the increase of chimney height and/or diameter. The developed model is used to analyze the feasibility of solar chimney power plants for the UAE climate which possesses typical characteristics of the Gulf climate. The solar characteristics of the UAE are shown along with characteristic meteorological data. A solar chimney power plant with a chimney height of 500 m and a collector roof diameter of 1000 m would produce at least 8 MW of power. The amount of power produced during the summer would be higher where the demand in the Gulf area is the highest.     

Performance assessment of a direct steam solar power plant with hydrogen energy storage: An exergoeconomic study

Power generation and its storage using solar energy and hydrogen energy systems is a promising approach to overcome serious challenges associated with fossil fuel-based power plants. In this study, an exergoeconomic model is developed to analyze a direct steam solar tower-hydrogen gas turbine power plant under different operating conditions. An on-grid solar power plant integrated with a hydrogen storage system composed of an electrolyser, hydrogen gas turbine and fuel cell is considered. When solar energy is not available, electrical power is generated by the gas turbine and the fuel cell utilizing the hydrogen produced by the electrolyser. The effects of different working parameters on the cycle performance during charging and discharging processes are investigated using thermodynamic analysis. The results indicate that increasing the solar irradiation by 36%, leads to 13% increase in the exergy efficiency of the cycle. Moreover, the mass flow rate of the heat transfer fluid in solar system has a considerable effect on the exergy cost of output power. Solar tower has the highest exergy destruction and capital investment cost. The highest exergoeconomic factor for the integrated cycle is 60.94%. The steam turbine and PEM electrolyser have the highest share of exergoeconomic factor i.e., 80.4% and 50%, respectively.     

Performance optimization and analysis of solar combi-system with carbon dioxide heat pump

In this paper, a solar combi-system which consists of solar collectors and a carbon dioxide heat pump is proposed and investigated through simulation and optimization. Performance analysis and comparison are primarily conducted to show the feasibility and reasonability of using a CO₂ heat pump as an auxiliary heater under local weather conditions. Then, a system model with a test building in TRNSYS is developed for performance optimization. The most influential variables are identified using influence and sensitivity analyzes of single parameters. Subsequently, a multi-parameter optimization using the high-weight parameters is carried out to obtain a final design result. The simulated results of the optimized case show that the average coefficient of performance of the CO₂ heat pump is 2.38, and the solar fraction of the system is 69.0% for the entire heating season. The time when a comfortable temperature level can be achieved in the indoor environment accounts for 81.6% of the entire heating season. Furthermore, the performance characteristics of the proposed system are evaluated in terms of the thermal balance, fraction of the thermal energy saving, feasibility of net zero energy, economic factor, and CO₂ emissions reduction.     

Spatially distributed model for the analysis of laser beam induced current (LBIC) measurements of thin film silicon solar modules

A 3D distributed model is developed and implemented based on circuit analysis software for the investigation of spatial variation in performance due to the distributed nature and non-uniformity of solar cell properties. This is applied to LBIC measurements where it is used for sensitivity analysis of the measurements with respect to certain parameters in series connected thin film PV modules.The model is used to explain the differences in dark and illuminated measurements, which clearly shows the illuminated LBIC signal is largely dependent on the homogeneity of the background illumination. The dark LBIC is largely affected by the shunt resistance of the neighbouring cells rather than by the signal strength of the cell under test. It is required to bring the cell into limiting conditions, which then gives a signal one order of magnitude stronger than that in the non-limiting case. The simulations are validated against measurements taken in these regimes.