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[Display omitted] • An optimized and efficient PV panel modeling is introduced in this paper. • A realistic analysis of five PV configurations is done using temperature prediction. • The analysis is based on the output power, fill factor and mismatch loss. • The parallel configurations are more efficient than the serial configurations. In this paper, a temperature prediction-based approach for realistic performance analysis of the solar photovoltaic system has been investigated. Dissimilar to general methods, the change in module temperature, due to changing solar irradiance, has been considered for realistic and accurate performance evaluation results under mismatch conditions. The module temperature is predicted by a linear equation representing the effects of ambient temperature, wind speed, and irradiance. An optimized technique has been implemented for photovoltaic panel modeling. It provides an accurate estimation of the series and shunt resistances of the photovoltaic panel. The proposed modeling method provides an accuracy of less than 0.02% at the maximum power point. The temperature prediction-based approach has been applied to a solar photovoltaic system of 16 panels, modeled using the proposed technique. Further, five photovoltaic configurations were investigated: Series, Series-Parallel, Honey-Comb, Bridge-Linked, and Total-Cross-Tied. The performance evaluation of each configuration is based on the generated maximum power, fill factor, and mismatch loss. Under mismatch conditions, the Total-Cross-Tied configuration shows a good immunity against mismatch by minimizing losses in all the considered mismatch patterns. The proposed approach provides more accurate results than the available ones because it considers the temperature effect (due to variation in ambient temperature, solar radiation, and wind speed), accounting for up to 12% reduction in output power of photovoltaic modules. [ABSTRACT FROM AUTHOR]

Abstract Power delivered by a Photovoltaic (PV) cell reduces significantly due to non-uniform irradiance. Consequently, in the case of PV module or array, the generated output power get reduces and further deteriorates the overall system performance. The reduction of output power is not directly proportional to the shading area but depends on the shading pattern and type of array configuration chosen. Many solutions have been reported in the literature to reduce partial shadings. However, the reported solutions may fail to enhance maximum power to the possible extent. Therefore, to compensate these power losses a promising technique is required which relies on reconfiguration strategies, namely reconfigure the PV modules within the PV array in order to increase maximum power at a higher level. These strategies are classified into dynamic and static reconfiguration techniques. This paper presents the state of the art of reconfiguration strategies for PV array's to increase maximum power under partial shading and mismatch conditions. In addition to this, the challenging issues for hardware implementation of both dynamic and static reconfiguration techniques are discussed in this paper. Based on the review study, it can be concluded that the dynamic reconfiguration techniques are relatively expensive, but this can effectively compensate the partial shading and mismatch effects in PV array as compared to static technique. [ABSTRACT FROM AUTHOR]

• A detailed assessment of energy performances of BIPV/T-DSF was performed. • Three types of PV glazing and three types of ventilation modes were assessed. • The model with a naturally-ventilated air cavity showed the lowest consumptions. • The façade with Perovskite cells has the highest conversion of solar radiation. • Both DSFs with natural and mechanical ventilation collect useful thermal energy. Being the interface between indoor and outdoor, building envelope significantly influences indoor heating and cooling loads and thus affects building energy consumption. This paper presents the results of numerical simulation for the performance prediction of building-integrated photovoltaic/thermal double-skin facade (BIPV/T-DSF). Different BIPV materials (amorphous silicon PV, dye-sensitized solar cell and Perovskite based solar cells) were considered as the exterior cladding of a North-facing facade of an office building located in Australia. The performance assessment involved the selection of three climates in Australia, represented by the cities of Darwin, Sydney and Canberra. The air cavity created between the outer skin and the inner one were alternatively assessed in the non-ventilated, naturally-ventilated and mechanically-ventilated modes of operation, while a full sensitivity analysis was performed in order to assess the influence of different design parameters, such as internal skin's thermal transmittance, cavity depth, ventilation louvres' opening ratio and cavity ventilation rate. By comparing the different operational modes and BIPV technologies, it was found that naturally-ventilated DSF integrating the Perovskite-based solar cell could be the optimal configuration achieving the highest savings. Total annual energy savings of 34.1%, 86% and 106% annual were reached respectively in Darwin, Sydney and Canberra, in comparison to conventional technologies. In addition, this façade technology could further reduce the building's heating and cooling loads by harvesting thermal energy generated within the air cavity. The study finally demonstrated that the harvested electrical and thermal energy from the façade could cover a significant share of building's energy consumption. [ABSTRACT FROM AUTHOR]

• Comparison of four forecasting models following mostly independent approaches. • Models performance highly dependent of the season and synoptic weather conditions. • Smart persistence model difficult to beat, especially at lead times lower than 2 h. • Break-even point between satellite and NWP models differs for GHI and DNI. • Notably higher errors at a coastal station, caused with sea-land breezes. The ability of four models to provide short-term (up to 6 h ahead) GHI and DNI forecasts in the Iberian Peninsula is assessed based on two years of data collected at four stations. The models follow (mostly) independent approaches: one pure statistical model (Smart Persistence), one model based on CMV derived from satellite images (Satellite), one NWP model (WRF-Solar) and a hybrid satellite-NWP model (CIADCast). Overall, results show Smart Persistence to be the best at the first lead steps, advective models (Satellite and CIADCast) at intermediate ones and the WRF-Solar at the end of the forecasting period. The break-even point between the advective models and WRF-Solar varies between 1 and 3 h for GHI and 3 and 5 h for DNI. Nevertheless, a detailed analysis shows enormous differences between models performance related to 1) the local geographic and topographic conditions of the evaluation stations; 2) the evaluated variable (GHI vs. DNI); and 3) the sky and synoptic weather conditions over the study area. Depending on the station and lead time, rRMSE values range from 25% to 70% for GHI and from 35% to 100% for DNI. For the same stations and leading time, rRMSE values for DNI are between 50% and 100% higher than the corresponding GHI counterparts. Depending on the synoptic pattern, rRMSE values are about 10/20% for GHI/DNI (3 h lead time, during high pressure conditions) to about 80/180% for GHI/DNI (during low pressure conditions). All models show a poor performance at a coastal station, attributed to a lack of ability to forecast clouds associated with sea-land breezes. To conclude, no single model proves to be the best performing model and, therefore, results show that the four models are, somehow, complementary. The advantages attained by this complementarity are further explored in a companion paper (Part II). [ABSTRACT FROM AUTHOR]

• Soiling index calculated through data processing obtained from a Tracking Cleanliness Sensor. • Particle deposition and soiling rates studied during different different periods of the year. • Scanning Electron Microscopy and Energy Dispersive Spectroscopy analysis. • Mirror performance and Cost-analysis for an Andasol-I type plant. Soiling represents a major problem for CSP plants, since the accumulation of particles onto the reflective surface cause absorption and scattering of solar irradiance, leading to a significant decrease in the mirrors' reflectance. Such problem can be amplified, particularly in CSP plants that are installed in semi-arid or arid regions which possess a high direct normal irradiance availability, prone to higher particle deposition due to sand storms, red rain events and, in general, higher atmospheric particle concentration. As means to reduce the amount of dust adhering to the mirrors, anti-soiling coatings are being developed to reduce particle deposition, minimizing maintenance costs due to cleaning processes, leading to an enhancement of energy production. In this paper, a Tracking Cleanliness Sensor was used to compare the Soiling Index between a set of coated and uncoated mirrors, which were left outdoors to naturally accumulate soiling in two different positions, horizontal and tilted 45°. The anti-soiling coating was developed by a partnership between RIOGLASS and IK4-TEKNIKER. Moreover, a simple economical model is proposed here for different possible scenarios regarding the coating used. [ABSTRACT FROM AUTHOR]

• Improved threshold-based methods for PV performance assessment are proposed. • The improved normal thresholds can change with the dynamic environment factors. • Probabilistic models are applied for the construction of the normal thresholds. • The proposed methods significantly increase the detected small power losses. Threshold-based methods are extensively applied for performance assessment of photovoltaic (PV) modules. When applying the conventional methods with fixed normal thresholds, the main problem is the low detection rate of relatively small power losses. As a result, taking the uncertainties in the PV data due to the dynamic environment into account when designing the normal thresholds is a real challenge. To address this issue, improved threshold-based methods for PV performance assessment based on probabilistic models are proposed in this paper. This is motivated by the availability of probabilistic models which allow to quantify the likely uncertainty in the deterministic point estimation. Two probabilistic models are developed using the quantile regression forests (QRF) method and the Bayesian regression (BR) method. The developed models provide confidence intervals for PV output efficiency which act as the normal thresholds for PV performance assessment. The proposed methods are tested on a grid-connected PV plant located in East China, and compared against the traditional methods based on deterministic models. They are also compared with an adaptive threshold-based method which updates the adaptive thresholds by a moving window. Results indicate that the proposed methods are able to identify outliers with 10% power losses almost twice as many as the ones detected by the other methods. [ABSTRACT FROM AUTHOR]

• A compression scheme based on planar wavelet transforms for BTDF data. • Compression on medium-resolution BTDF and high-resolution-BTDF data of various CFSs. • Assessment on the compression ratio versus generic error with different wavelet bases. • Evaluation on the influence of BTDF data compression on the daylighting simulation for a building interior. The bidirectional transmittance distribution function (BTDF), which is used to characterize the light transmission of a complex fenestration system (CFS), commonly involves bulky volume of data that can be a challenge to data storage and transmission in lighting simulation tools and on compact platforms. This paper introduces a compression scheme that is based on planar wavelet transforms with three levels of decomposition to efficiently compress the BTDF data of CFSs and maintain fidelity in daylighting simulation. The root-mean-square error (RMSE) and transmittance error (TE) of compressed medium-resolution BTDF data using three different wavelet bases were evaluated for five different CFS samples at various compression ratio. Based on the results, the generic error from compression did not exceed 20 % with CDF9.7 basis for compression ratio up to 200. In the case of rendering an image of a scene in which a CFS was installed at the upper daylighting section of an unilateral façade, errors began to be noticeable at a compression ratio above 70. The uniformity factor g 1 was discovered to be relatively sensitive to compression (below 15% error), while the average horizontal illuminance and daylight glare probability (below 10% error) were immune to compression ratio below 100. Compression was also evaluated for a high-resolution BTDF data of external Venetian blinds in the simulation of work-plane illuminance (WPI). With a HDR imaging technique based sky luminance map, the WPI simulation had unnoticeable errors for compressed BTDF data within a compression ratio of 100. [ABSTRACT FROM AUTHOR]

Abstract: Parabolic Trough concentrators are the predominant Concentrated Solar Power (CSP) technology today. However this technology is facing substantial challenge from the need to reduce costs and/or increase performance. This paper address this challenge by exploring the room left from the fact this type of optic falls short from the theoretical limits of concentration, proposing a new solution enabling the design of larger troughs with higher concentration or larger acceptance angles, through the use of second stage concentration of a novel type. This new optic is designed with the Simultaneous Multiple Surface (SMS) method for two reflective (X) surfaces (XX SMS) Winston et al. (2005) – of which the primary is approximately parabolic – using a different assignation of the edge rays in order to significantly reduce the Fresnel losses around the glass cover of the evacuated tubes commonly used in CSP applications. To analyze the merits of this new optic, two different comparisons are made. The first one with the SMS Helmet concentrator through the calculation of CAP (Concentration–Acceptance Product) and the second one with a commercial Parabolic Trough concentrator, using an estimate of the total amount of collected energy (kWh) for one particular location, Faro (Portugal). The paper ends with a discussion of the results obtained, their impact and possible applications in the future. [Copyright &y& Elsevier]

Abstract: Solar power tower receivers are exposed to highly-concentrated solar flux. The strong flux variations that they are exposed to during their service life enhance the physical–chemical aging mechanisms and cause the decrease of the material’s thermal performance. A material that is commonly used for these applications was selected for our study. It is used for the absorber tubes of a solar power tower receiver. This material is made of an alloy (Inconel 625) that is coated with a silicone-based paint coating (Pyromark 2500 black) to increase the solar radiation absorption capacity. With the aim of determining the optimal conditions to accelerate the aging of this two-layer material (metal+paint coating), an axisymmetric 2-D model reproducing its thermal behavior was developed. Several thermal indicators (temperature, thermal gradients, temporal gradient), which are representative of the thermal aging factors and the material’s thermal performance, are analyzed in different configurations of boundary conditions. One configuration was defined according to the normal working conditions of a particular solar power plant application; the others are associated with various boundary conditions with the potential to increase or modify the thermal stress factors to accelerate the aging mechanisms. Other aging factors such as humidity, pollutants, and dust are not investigated in this paper. Several simulations were run in permanent and variable regimes. The most influencing boundary conditions and material properties were highlighted by a sensitivity study. To design relevant aging tests, particular attention should be paid to the incident solar power and the cooling characteristics of the material. The surface total absorptance, the thermal conductivities and the thermal contact resistance between the paint and the metal layers are the parameters that most affect the material’s thermal behavior. The evolution of those material properties characterizes the aging and should be monitored. Irradiance cycles were simulated for their potential to increase the thermal fatigue. Depending on the average, the amplitude and the period of the cycle, the evolution of the thermal indicators were analyzed. They were compared to select the most appropriate aging tests that are to be performed. From there, two aging strategies were determined. To put them in practice, an experimental Solar Accelerated Aging Facility (SAAF) was built and is described in this paper. It enables to perform accelerated aging experiments with a 2-m-diameter parabola concentrating the sun radiation up to 16,000 times. A preliminary experiment to validate the model confirmed that the simulation results are in good agreement with the experimental. [Copyright &y& Elsevier]

Abstract: This paper presents a simple method for evaluating the influence of wiring on the operating conditions of the direct current components in a photovoltaic system design. This method uses electrical circuit theory, electrical resistance modeling, and an iterative calculation approach to address the causality dilemma that exists when estimating voltage reductions in the wires that connect photovoltaic modules to power inverters. This method can be used to estimate the voltage, current output, and power output of each photovoltaic module in a system, and the corresponding total power available at the inverter, given current–voltage (I–V) models for the photovoltaic modules, and the lengths and thicknesses of the corresponding interconnection wiring. This paper uses this method to illustrate the influence that wiring can have on the direct current operating voltage that is needed at the power inverter to achieve maximum power performance for the system. The goal is that this method would be incorporated into software that analyzes the power performance and energy output of photovoltaic systems. [Copyright &y& Elsevier]

Abstract: This paper presents a novel terminal sliding mode control (TSMC) method for maximum power tracking of photovoltaic (PV) power systems. First, an incremental conductance method is used for maximum power point (MPP) searching. It provides good efficiency under rapidly changing atmospheric conditions, but the accuracy for finding the MPP is highly related to the MPP tracking control. Therefore, a TSMC-based controller is developed to regulate the system to the searched reference MPP. Different from traditional sliding mode control, the developed TSMC assures finite convergence time for the MPP tracking. Furthermore, a common singularity problem that exists in traditional TSMC is removed in this paper. Even if considering uncertainty in the PV power system, the TSMC guarantees high robustness. Finally, several simulations and experiments show the expected control performance. [Copyright &y& Elsevier]

Abstract: Sizing of stand-alone photovoltaic systems (SAPVS) requires knowledge of their reliability. Because of primary influence of the solar irradiance and meteorological conditions, simulations are the best way to compute an accurate reliability for a given location and fixed sizing parameters. These studies have been developed for more than two decades, but have had a narrow geographical applicability. In this paper, we perform a complete (in time and space) simulation of a standard SAPVS in Europe using 23year radiation data corresponding to almost 2300 geographical points. At each point, the tilt angle that maximizes the energy reaching the PV array in December is estimated and the relation among sizing parameters and reliability is computed for wide ranges of values. Finally, multilayer perceptrons are trained for both computations, allowing (after their training) simple and fast estimations of the sizing parameters of this type of plants for any location in Europe. The procedure presented in this paper, although focused particularly in Europe, can be easily extended to almost any other region in the world. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: Solar thermal plants are among the most promising technologies to replace fossil fuel stationary applications, and within solar thermal technologies, parabolic troughs are considered the most mature application in the market. This paper compares different solar field technologies, in terms of both performance at design conditions and annual energy production; an in-house code, PATTO, was used to perform energy balances. We considered a reference case reflecting state-of-the-art Nevada Solar One, which showed a design efficiency and annual average efficiency of 22.4% and 15.3%, respectively, in agreement with actual performance. If solar salts are used as heat-transfer fluid instead of synthetic oil (e.g. ARCHIMEDE plant), the efficiency improved within the range of 6% due to the higher maximum temperature. Further thermodynamic advantages can be achieved with a direct steam generation plant; the main drawback is the more complex transient control and no commercially available storage systems. We propose the innovative Milan configuration, which combines advantages of direct steam evaporation and the use of a heat-transfer fluid, to investigate both synthetic oil and solar salts for steam superheating and reheating. Results for this configuration are very promising, with a sun-to-electric annual average efficiency of 17.8%, which is 16% higher than the reference case. Detailed daily simulations showed that advantages are more significant at low radiation. However, the plant should be optimized on an economic basis and we will discuss this in a future paper. [Copyright &y& Elsevier]

Abstract: Zero energy buildings (ZEB) and zero energy homes (ZEH) are a current hot topic globally for policy makers (what are the benefits and costs), designers (how do we design them), the construction industry (can we build them), marketing (will consumers buy them) and researchers (do they work and what are the implications). This paper presents initial findings from actual measured data from a 9 star (as built), off-ground detached family home constructed in south-east Queensland in 2008. The integrated systems approach to the design of the house is analysed in each of its three main goals: maximising the thermal performance of the building envelope, minimising energy demand whilst maintaining energy service levels, and implementing a multi-pronged low carbon approach to energy supply. The performance outcomes of each of these stages are evaluated against definitions of net zero carbon/net zero emissions (site and source) and net zero energy (onsite generation vs primary energy imports). The paper will conclude with a summary of the multiple benefits of combining very high efficiency building envelopes with diverse energy management strategies: a robustness, resilience, affordability and autonomy not generally seen in housing. [Copyright &y& Elsevier]

Highlights • Solar cooker with tracking reflector is evaluated experimentally. • Two figures of merit, thermal efficiency and cooking power are analyzed. • Effects of tracking angle of reflector and vessels material are investigated. Abstract This paper experimentally investigated the thermal performance of the developed solar box cooker with different reflector configurations. All tests were carried out under Bahir Dar (Ethiopia) prevailing weather condition. Two standard tests, namely stagnation test and sensible heat test were adopted in order to evaluate the thermal performance of the cooker. The highest maximum plate temperature of 148.7 °C can be achieved by the cooker with tracking reflector at optimal angle. In order to evaluate the performance of the cooker, the following performance indexes were employed, thermal efficiency, cooking power and two figures of merit, namely the ratio of optical efficiency to heat loss factor (F 1) and the product of heat exchange efficiency factor and optical efficiency (F 2). According to the experimental data, the highest computed value F 1 of 0.154°C m2/W, can be obtained from the cooker with tracking reflector at optimal angle. The thermal efficiencies achieved by Cooker I, II and III are 37.24%, 32.27% and 33.89%, respectively. Thermal efficiency of the cooker was improved by 9.6% by tracking reflector at optimal angle instead of with fixed reflector. Furthermore, the thermal efficiency was also improved by 15.4% by using aluminum cooking vessel in place of using stainless steel vessel. It can be concluded from the experiments that effective utilization of all solar radiation intercepted on the reflector, and the use of cooking vessel having a reasonably good thermal diffusivity contribute significant roles to improve the cooking performance of the cooker. [ABSTRACT FROM AUTHOR]

Abstract: Islanding phenomenon is undesirable because it leads to a safety hazard to utility service personnel and may cause damage to power generation and power supply facilities as a result of unsynchronized re-closure. Until now, various anti-islanding methods (AIMs) for detecting and preventing islanding of photovoltaic and other distributed generations (DGs) have been proposed. This paper presents an overview of recent anti-islanding method developments for grid-connected photovoltaic (PV) power generation, focusing on the concept and operating principle, mainly based on single phase system. For the performance comparison, the experimental results of the various AIMs with 3kW PV inverter are provided based on the islanding detection capability and power quality. As a result, the active AIMs have better islanding detection capability rather than the passive one. However, the active AIMs have power quality degradation on harmonic distortion or displacement power factor based on the injected active signal type. In addition to the evaluation and comparison of the main anti-islanding methods, this paper also summarizes the related anti-islanding standards to evaluate anti-islanding capability for PV system. This paper can be used as a useful anti-islanding reference for future work in DG like PV, and wind turbine. [Copyright &y& Elsevier]

Abstract: The hot water temperature that maximizes the overall instantaneous efficiency of a solar cooling facility is determined. A modified characteristic equation model is used and applied to single-effect lithium bromide–water absorption chillers. This model is based on the characteristic temperature difference and serves to empirically calculate the performance of real chillers. This paper provides an explicit equation for the optimum temperature of vapor generation, in terms of only the external temperatures of the chiller. The additional data required are the four performance parameters of the chiller and essentially a modified stagnation temperature from the detailed model of the thermal collector operation. This paper presents and discusses the results for small capacity machines for air conditioning of homes and small buildings. The discussion highlights the influence of the relevant parameters. [Copyright &y& Elsevier]

Abstract: Photovoltaic–thermal (PV/T) technology refers to the integration of a PV and a conventional solar thermal collector in a single piece of equipment. In this paper we evaluate the performance of partially covered flat plate water collectors connected in series using theoretical modeling. PV is used to run the DC motor, which circulates the water in a forced mode. Analytical expressions for N collectors connected in series are derived by using basic energy balance equations and computer based thermal models. This paper shows the detailed analysis of thermal energy, exergy and electrical energy yield by varying the number of collectors by considering four weather conditions (a, b, c and d type) for five different cities (New Delhi, Bangalore, Mumbai, Srinagar, and Jodhpur) of India. Annual thermal and electrical energy yield is also evaluated for four different series and parallel combination of collectors for comparison purpose considering New Delhi conditions. This paper also gives the total carbon credit earned by the hybrid PV/T water heater investigated as per norms of Kyoto Protocol for New Delhi climatic conditions. Cost analysis has also been carried out. It is observed that the collectors partially covered by PV module combines the production of hot water and electricity generation and it is beneficial for the users whose primary requirement is hot water production and collectors fully covered by PV is beneficial for the users whose primary requirement is electricity generation. We have also found that if this type of system is installed only in 10% of the total residential houses in Delhi then the total carbon credit earned by PV/T water heaters in terms of thermal energy is USD $144.5 millions per annum and in terms of exergy is USD $14.3 millions per annum, respectively. [Copyright &y& Elsevier]

It is a common practice to test solar thermal and photovoltaic-thermal (PVT) collectors outdoors. This requires testing over several weeks to account for different weather conditions encountered throughout the year, which is costly and time consuming. The outcome of these tests is an estimation of the thermal performance characteristics of the collector. Collector performance parameters can be derived with less effort by indoor testing under a solar simulator. However, in case of unglazed PVT collectors the thermal and the electrical performance is affected by two phenomena-additional long wave radiation (3000 nm and greater) due to emissions and reflections from the high temperature artificial sky, and an energy content of the PV spectrum (300–1100 nm) that differs from the global solar spectrum (300–2500 nm). These differences from the reference AM 1.5 solar spectrum lead to errors in the estimation of collector thermal and electrical performance. Therefore, results of indoor performance tests must be corrected to obtain the output of an unglazed PVT collector in real outdoor environment. In this paper a method is proposed to estimate the real thermal performance of unglazed PVT collectors, by using a compact indoor solar simulator testing in combination with a detailed steady state numerical PVT collector model. The numerical model takes into account the physical and spectral attributes of the solar simulator and is used to correct for the unwanted phenomena to derive the actual outdoor collector performance. The resulting numerical model also offers detailed understanding of the collector and can therefore be used to optimise the design of the collector. Furthermore, this model is used to derive thermal performance characteristics of the unglazed PVT collector as defined by solar thermal testing standards, which can be used in system simulation tools (E.g. TRNSYS models) to obtain annual collector and system yields. [ABSTRACT FROM AUTHOR]

This paper proposes advanced analytical, numerical and genetic algorithm (GA) approaches for retrieving the parameters of photovoltaic (PV) panel. A comparative study for extracting the five parameters of a single diode PV model is presented. Based on the datasheet values, a numerical based Newton-Raphson algorithm is investigated for solving the current-voltage relation of a single diode solar PV model. To highlight the rigorous performance of our models, a second analytical model is proposed. For improving the accuracy of solar panel parameters, a technique based on GA is established. This approach is based on the problem of research and optimization of the extracted parameters as an objective function. To account for variation in solar radiation and temperature, these models are presented under the reference and real operating conditions. The performances of the proposed algorithms are compared by using MATLAB scripts programming, and the theoretical advantages of GA model were demonstrated. The different models are validated experimentally by various tests of temperature and solar irradiance variation. The experimental results indicate that the GA model has a very satisfactory performance compared with the two other models and it offers good compromise between accuracy and fastness. [ABSTRACT FROM AUTHOR]

This paper presents the development and implementation of an enhanced forced switching sliding mode control (FSSMC), for dual inverter-based single stage solar photovoltaic (PV) system a stand-alone. A dual inverter fed open winding three-phase transformer is used to supply a stand-alone load in the considered topology. The FSSMC is developed for the current control of the dual inverter, while the dc-link voltage control loop is developed through indirect vector control. The solar irradiance and load impedance variations are successfully handled by the developed control scheme. The stability and disturbance rejection analyses are conducted on a linear model of the system to characterize the dynamic properties of the system and to evaluate the robustness of the controllers. The controller is implemented in simulation and experimental environments at different operating conditions. Experimental tests have been conducted on a laboratory scaled prototype using the digital controller. The performance is found to be satisfactory and have been successfully verified with the real time results. [ABSTRACT FROM AUTHOR]

A nonlinear dual-loop H ∞ controller is presented in this paper synthesized with linear matrix inequality (LMI) method with primary objectives of generating switching signals for inverters for maximum power point tracking and improving dynamic response of a single-phase grid-connected photovoltaic (PV) system. A state-space model of the PV system is developed with parametric uncertainty in terms of linear fractional transformation. A dual control loop is implemented into the control structure: one is outer dc-link voltage control loop and the other is inner grid current control loop. Weighting functions are first selected and tuned to achieve minimum tracking error and robust performance. Next, control laws are obtained by synthesizing the controller. To facilitate practical implementation, model order of the controller is reduced by Henkel-norm method. The performance of the proposed controller is demonstrated on a test system through simulation results under different parametric, atmospheric and load conditions as well as system contingencies. From the simulation results, it is evident that the controller provides superior performance under various operating conditions. [ABSTRACT FROM AUTHOR]

Highlights: [•] We have analyzed the main water PVT flate plate configuration and relative performance parameters. [•] We have subdivided the review according to the main elements that compose PVT collectors. [•] We are focused in the analysis of the thermal absorber that in recent years has been an object of significant developments. [•] Finally we provide summary of the salient point of the paper. [Copyright &y& Elsevier]

Highlights: [•] Solar energy use has increased considerably in the last decade. [•] One of the main challenges identified by the U.S. National Academy of Engineering is to make solar energy economical. [•] Advanced control techniques can be useful to improve the performance of solar systems. [•] This paper presents a procedure to optimize the operation of trough solar plants. [Copyright &y& Elsevier]

Abstract: This paper presents a new maximum power point tracking method based on the current–voltage characteristic of photovoltaic arrays. The new approach is not only capable to track the maximum power point like the conventional methods under uniform insolation conditions, but also capable to find the global maximum power point efficiently and rapidly under partially shaded conditions. The proposed algorithm could find a new MPP quickly when a sudden change occurs in the insolation level. To verify the performance of the proposed method, several simulations have been carried out in MATLAB/Simulink environment. Experimental investigations have also been performed to confirm the validity of simulation results. [Copyright &y& Elsevier]

Abstract: This paper presents a study of thermal performance for a glass window with a curved venetian blind installed on the indoor side in terms of heat gain in the shortwave part of radiation. The curved venetian blind, whose optical properties are considered nonspecular, is modeled as an effective layer. The mathematical model of the combined glass window and venetian blind is developed by combining the mathematical model of glass window and the mathematical model of a curved venetian blind using the matrix layer calculation method. The experiment is performed in a test room to measure the heat gain due to solar radiation passing through the glass window with a curved venetian blind installed in the shortwave part of radiation. The predicted results from the developed model are compared with the experimental results. The agreement between the predicted results and the experimental results is good. From the study it is found that installing a curved venetian blind to the glass window causes a significant reduction in heat gain compared to the plain glass window. The heat gain through the glass window with blind in the shortwave part of radiation (solar heat gain coefficient in the shortwave part of radiation (ShW SHGC)) is analyzed. It is found that the ShW SHGC is mainly affected by the slat properties, slat angle and solar profile angle. The glass window using blind with a lower value of slat reflectance, will have a smaller value of ShW SHGC. The slat distance also affects the ShW SHGC. The glass window using blind with a lower value of slat distance has a lower value of ShW SHGC. The effect of the slat curvature on the ShW SHGC is small when compared to the effect of other parameters. The effects of the investigated parameters on the ShW SHGC for diffuse radiation are similar to the effects on the ShW SHGC for direct radiation. When installing blind to different kinds of glass window other than clear glass window, it is found that the thermal performance is similar to the case of clear glass window. The magnitude of the ShW SHGC for the glass window with blind is also dependent on the optical properties of the glass window used. The glass window with blind using a lower value of the glass transmittance has a lower value of the ShW SHGC. The absorptance of the glass window has direct effect on the solar heat gain coefficient in the longwave part of radiation (LoW SHGC). [Copyright &y& Elsevier]

Abstract: This paper presents an analysis of the thermal performance of a solar water heating system with heat pipe evacuated tube collector using data obtained from a field trial installation over a year in Dublin, Ireland. An automated sub-system was developed and incorporated to control the hot water draw-offs and electric immersion heater to mimic the operation of solar water heating systems in domestic dwellings. The maximum recorded collector outlet fluid temperature was 70.3°C while the water temperature at the bottom of the hot water tank was 59.5°C. The annual average daily energy collected was 20.4MJd−1, energy delivered by the solar coil was 16.8MJd−1, supply pipe loss was 3.6MJd−1, solar fraction was 33.8%, collector efficiency was 63.2% and system efficiency was 52.0%. Reducing the supply pipe losses which represented 17.7% of energy collected and 21.5% of energy delivered to the hot water tank, and developing a better pump control strategy for heavily overcast and intermittent cloud covered days could result in system improvement. [Copyright &y& Elsevier]

Abstract: In desert sunny clear-sky regions solar penetration can become excessive. This can cause non-uniform daylight distribution, glare and high solar heat gain, affecting both visual and thermal comfort. Shading devices, such as solar screens, were usually used to diffuse and prevent direct solar penetration into spaces. This paper investigates the impact of changing solar screen axial rotation angle and screen opening aspect ratio on daylighting performance in a typical residential living room space under the desert sunny clear-sky. The larger aim is to arrive at efficient solar screen designs that suit the different orientations. The study was divided into three consecutive phases. In phase one, the effect of the two parameters on Daylight Availability was tested. The solar screen was axially rotated by three different angles at 10° increments. Also, the aspect ratio of the screen opening in both horizontal and vertical directions was changed systematically. Simulation was conducted using the annual Daylight Dynamic Performance Metrics (DDPMs). In phase two, the Annual Daylight Glare Probability (DGP) metric was evaluated for the cases that were found adequate in phase one. In the third phase, the annual solar energy transmittance through the screen was calculated for the cases that achieved acceptable performance in the two previous phases in order to identify the more energy efficient screens. Solar screens with openings having horizontal aspect ratios were found to be the most effective, while those with vertical aspect ratios were achieved the lowest performance. In the North orientation, since almost all the cases that were tested in this research provided acceptable daylighting performance, the designer now have a variety of options to choose from. Preference should be given to screen openings of horizontal aspect ratios, especially the 12:1 and 18:1 (H:V) screens that achieved the best performance where 92% of the space was “daylit” in comparison with only 53% of the base case. In the East orientation, it is advisable to use the 12:1 (H:V) screen opening ratio, as it was found acceptable in the two daylighting testing phases and achieved the best performance in regards to annual transmittance of solar radiation. For the South orientation, there were also many acceptable choices. However, the 3:1 screen aspect ratio is recommended as it assists in saving energy by reducing the annual transmitted solar radiation (60% reduction) while achieving acceptable daylighting performance. [Copyright &y& Elsevier]

Abstract: In this paper, a performance and cost assessment of Integrated Solar Combined Cycle Systems (ISCCSs) based on parabolic troughs using CO2 as heat transfer fluid is reported on. The use of CO2 instead of the more conventional thermal oil as heat transfer fluid allows an increase in the temperature of the heat transfer fluid and thus in solar energy conversion efficiency. In particular, the ISCCS plant considered here was developed on the basis of a triple-pressure, reheated combined cycle power plant rated about 250MW. Two different solutions for the solar steam generator are considered and compared. The results of the performance assessment show that the solar energy conversion efficiency ranges from 23% to 25% for a CO2 maximum temperature of 550°C. For a CO2 temperature of 450°C, solar efficiency decreases by about 1.5–2.0% points. The use of a solar steam generator including only the evaporation section instead of the preheating, evaporation and superheating sections allows the achievement of slightly better conversion efficiencies. However, the adoption of this solution leads to a maximum value of the solar share of around 10% on the ISCCS power output. The solar conversion efficiencies of the ISCCS systems considered here are slightly greater than those of the more conventional Concentrating Solar Power (CSP) systems based on steam cycles (20–23%) and are very similar to the predicted conversion efficiencies of the more advanced direct steam generation solar plants (22–27%). The results of a preliminary cost analysis show that due to the installation of the solar field, the electrical energy production cost for ISCCS power plants increases in comparison to the natural gas combined cycle (NGCC). In particular, the specific cost of electrical energy produced from solar energy is much greater (about two-fold) than that of electrical energy produced from natural gas. [Copyright &y& Elsevier]

Abstract: Surface slope error of concentrator is one of the main factors that influence the performance of the solar concentrated collectors which cause deviation of the reflected ray and reduce the intercepted radiation. This paper presents the general equations to calculate the standard deviation of the reflected ray error from that of slope error through geometry optics analysis, applying the equations to calculate the standard deviation of the reflected ray errors in five kinds of solar concentrated reflector, and providing typical results. The results indicate that the reflected ray errors at one direction may come from the optic errors of both directions when the incidence angle is more than 0. The error transfer from the surface slope to a reflected ray is enlarged to more than twofolds in the heliostats, solar troughs, and linear Fresnel solar energy collecting system. The equation for the reflected ray errors is generally fit for all reflection surfaces without refraction, and can also be applied to control the errors in designing an abaxial optical system. [Copyright &y& Elsevier]

Abstract: For decades, residential and commercial roofs have been considered a prime location for installation of building integrated solar systems. In climatic conditions of East Tennessee, USA, an experimental solar roof was tested during 2009/2010, by a research team representing Metal Construction Association (MCA), and a consortium of building insulation companies, photovoltaic (PV) manufacturers, and energy research centers. The main objective was to thermally evaluate a new roofing technology utilizing amorphous silicon PV laminates integrated with the metal roof panels. In order to mitigate thermal bridging and reduce roof-generated thermal loads, this novel roof/attic assembly contained a phase change material (PCM) heat sink, a ventilated air cavity over the roof deck, and thermal insulation with an integrated reflective surface. During winter, the experimental roof was expected to work as a passive solar collector storing solar heat absorbed during the day, and increasing overall attic air temperature during the night. During summer, the PCM was expected to act as a heat sink, reducing the heat gained by the attic and consequently, lowering the building cooling-loads. In this paper, field thermal performance data of the experimental PV-PCM roof/attic system are presented and discussed. Performance of the PV-PCM roof/attic is evaluated by comparing it to a control asphalt shingle roof. The test results showed about 30% heating and 50% cooling load reductions are possible with the experimental roof configuration. [Copyright &y& Elsevier]

Abstract: The use of external fixed shading devices to adjust solar influx radiation and to save energy is well known. However, fixed shading devices can reduce daylight availability, increase artificial light needs and block the beneficial winter solar radiation. This paper is part of a research on the characteristics of the optimum shading device. The aim is to investigate the balance between the energy needs for heating and cooling the space that the shading device is used for and the energy that is used for lighting the same space and the energy that the shading device can produce. In order to investigate the balance between the above mentioned parameters, thirteen types of fixed shading devices have been studied and categorized according to their energy performance, for a single occupant office room. The same office room is tested for two different Mediterranean latitudes in Athens and in Chania, Crete in Greece and for two different south facing windows’ sizes. The thermal behavior of the devices is assessed through computer simulation application and the daylight analysis is assessed with both computer simulation and physical modeling. Stable parameters were the internal loads in the office room, the south orientation of the façade and the type of glazing. Variable parameter was the type of the fixed shading device. The study shows that all shading devices with integrated south facing PV can efficiently produce electricity which may be used for lighting. The study highlights the fact that shading devices such as Surrounding shading, Brise–Soleil full façade and Canopy inclined double work efficiently against thermal and cooling loads and may be used to produce sufficient electricity and control daylight. The study defines the geometrical parameters that will be incorporated to the overall characteristics of the optimum fixed shading device and proposes new fields of development for the BIPV technologies. [Copyright &y& Elsevier]

Abstract: This paper is based on the study of an experimental wooden-framed house, equipped with a ventilated cladding, located in France. The focus is on investigating the heat transfer taking place in the ventilated air gap behind the cladding and on estimating their impact on heat transfer in the insulated part of the walls. Preliminary CFD simulation made it possible to describe the airflow in the ventilated air gap when buoyancy was acting as the main driving force. It was found that the airflow velocity could reach 0.8ms−1, when exposed to 570Wm−2 solar irradiance. This was verified experimentally. A correlation to assess airflow rate in the air gap behind the cladding has been developed based on temperature differences and on experimental conclusions. The correlation is adapted to energy performance simulation and efficiently represents the average cavity airflow at different height for various irradiance and temperature conditions. [Copyright &y& Elsevier]

Abstract: A Trombe wall that uses a phase change material (PCM) as the heat storage medium is usually called a PCM Trombe wall or PCM wall. A research project was conducted to investigate the performance of coupled novel triple glass (NTG) and PCM wall, which is simply called PCM wall in this paper, as a solar space heater. The south façade of a test room was constructed using PCM walls. Rubitherm® GR35 and GR41 were incorporated into the plaster of the walls as PCM. The ratio of the solar energy gain provided by the PCM walls to the heat load of the test room per month varied from 4% to 70%; daily overall efficiency of the PCM walls varied from 20% to 36%; and solar transmittance of the NTG varied from 0.45 to 0.55 during the heating period. The overall efficiency of the PCM wall including GR35 was higher than that of the PCM wall including GR41. [Copyright &y& Elsevier]

Abstract: Different types of tools, software and empirical methods to size and assess the performance of solar thermal systems are available today. A quick and easy-to-use graphical tool is proposed here. It is based on a single diagram, called a nomograph, which embeds technical and economic information, allowing the optimisation of the size and performance of a solar thermal system starting from the main input parameters, such as the specific costs of the system and the auxiliary fuel. The optimal surfaces are calculated as a function of the fuel cost through several regressions made on data from the application of the F-Chart method for a set of system configurations. The authors have found good correlations among these two parameters for given collectors types, climates and fuel costs. Furthermore, the design information stemming from the use of the diagram considers the optimal area of the surface of solar collectors, the corresponding annual solar fraction, the annualised total cost of the solar system and the conventional systems meeting the same load, the annual savings achieved with the use of solar system and the corresponding payback time. Nomographs have been drawn for three Italian locations, representative of different South Europe climates, for a given demand of hot water and for two types of collectors. The methods and algorithms related to the construction of the diagrams are described in this paper. Additional nomographs can be produced through a standardised procedure based on Excel Macros. An analysis of the results obtained is then performed for a sample application. [Copyright &y& Elsevier]

Abstract: The paper presents the results of experimentally supported numerical analysis performed in order to investigate the possibilities to improve the thermal efficiency of plate solar collectors. Different numerical models were developed in order to asses the influence of design and operating parameters such as bond conductance between absorber plate and tube, tube diameter, glass cover to absorber plate distance, optical properties of absorber and flow rate on thermal efficiency of collectors. Following the results, two designs of collector without tubes, with parallel flat and corrugated absorber plates of chevron type, is further considered and shown to be an effective way to increase the thermal efficiency of solar energy conversion beyond that of commercial glazed and unglazed solar water heaters. Based on the results, the guidelines for design of a new collector prototype consisting of chevron type corrugated plates normally used in plate heat exchangers are provided. [Copyright &y& Elsevier]

Abstract: A new performance parameter for PCM thermal storage systems, the energy storage effectiveness, is defined. This parameter can be used to optimise the design of any PCM thermal storage system to maximise the use of the thermal storage media. The paper presents results of a parametric study using an experimentally validated numerical model for PCM encapsulated in plates. The results are used to calculate the energy storage effectiveness which is ultimately used to optimise the useful energy that can be stored in the PCM thermal storage system. The energy storage effectiveness is also used to compare the useable storage capacity of the PCM relative to a sensible energy storage system. [Copyright &y& Elsevier]

Abstract: In cooling buildings, the use of solar energy can save around 50% of primary energy. Many studies have demonstrated the interest of such systems. However, developing and improving reliability of new components, design, control, and implementation remain a major concern. The performances of solar cooling systems are greatly influenced by climatic conditions. Indeed they affect both the driving energy of the chiller and the heat rejection. It is important to mention that internal loads and control strategy also have an impact on energy performances. Therefore, assessing the energy performance during the design phase is a key point in evaluating the economic interest of an installation. Moreover, once the commissioning of the installation is accomplished, there is a need to follow through and ensure its performance, since a large number of malfunctions can affect the quality of the system. Actual performances can be very different from those calculated in the design phase. With this aim, the present article deals with the development of an absorption chiller model used in an existing solar cooling system. This installation includes a single effect absorption chiller with a nominal chilling capacity of 30kW (EAW LB30 chiller functioning with water and lithium bromide), and it cools four classrooms of a University building in Reunion Island which is situated under a tropical climate. This pilot plant is very good monitored and can thus be used to develop and validate the absorption chiller model. The present paper first recalls the absorption principle and presents the pilot plant, the metrology, and the control strategy. Secondly, the experimental results are analysed and the steady state chiller model and also the identification method are developed. Thereafter, the simplex method is used to determine the design parameters of the machine. Finally, the simulation results are presented. The good agreement between the prediction and the experimental results allows the use of the model not only to design an installation but also to follow and control its performances. [Copyright &y& Elsevier]

Abstract: This paper presents an intelligent sizing technique for sizing grid-connected photovoltaic (GCPV) system using evolutionary programming (EP). EP was used to select the optimal set of photovoltaic (PV) module and inverter for the system such that the technical or economic performance of the system could be optimized. The decision variables for the optimization process are the PV module and inverter which had been encoded as specific integers in the respective database. On the other hand, the objective function of the optimization task was set to be either to optimize the technical performance or the economic performance of the system. Before implementing the intelligent-based sizing algorithm, a conventional sizing model had been presented which later led to the development of an iterative-based sizing algorithm, known as ISA. As the ISA tested all available combinations of PV modules and inverters to be considered for the system, the overall sizing process became time consuming and tedious. Therefore, the proposed EP-based sizing algorithm, known as EPSA, was developed to accelerate the sizing process. During the development of EPSA, different EP models had been tested with a non-linear scaling factor being introduced to improve the performance of these models. Results showed that the EPSA had outperformed ISA in terms of producing lower computation time. Besides that, the incorporation of non-linear scaling factor had also improved the performance of all EP models under investigation. In addition, EPSA had also shown the best optimization performance when compared with other intelligent-based sizing algorithms using different types of Computational Intelligence. [Copyright &y& Elsevier]

Abstract: Solar CombiSystems (SCSs) are very efficient systems for reducing conventional energy consumption of building but their thermal performances are strongly dependent on the environment where they are installed (type of climate and thermal quality of the building). Currently it is impossible to predict the energy savings generated by a SCS as there is no standard test to characterise SCS performances. Currently, the Short Cycle System Performance Test (SCSPT), based on a 12days test of the complete SCS on a semi-virtual test bench, is able to predict annual energy savings with a good accuracy, but the performance prediction is limited to only one environment (the building and the climate corresponding with the test). Based on the SCSPT procedure, this paper proposes an improvement of the method by identifying a global SCS model from the test data. Then, the identified model would be able to simulate the tested SCS in any environment and thus to characterise its performances. The proposed model to identify is a “grey box” model, mixing a “White Box” model composed of known physical equations and a “Black Box” model, which is an Artificial Neural Network (ANN). A complete process is developed to train and select a relevant global SCS model from such a test. This approach has been validated through numerical simulations of three detailed SCS models. Compared to those annual results, “Grey Box” SCS models trained from a twelve days sequence are able to predict energy consumption with a good accuracy for 27 different environments. An experimental application of this procedure has been used to characterise a real system. [Copyright &y& Elsevier]

Abstract: The desert climate is endowed by clear sky conditions, providing an excellent opportunity for optimum utilization of natural light in daylighting building indoor spaces. However, the sunny conditions of the desert skies, in countries like Egypt and Saudi Arabia, result in the admittance of direct solar radiation, which leads to thermal discomfort and the incidence of undesired glare. One type of shading systems that is used to permit daylight while controlling solar penetration is “Solar Screens”. Very little research work addressed different design aspects of external Solar Screens and their influence on daylighting performance, especially in desert conditions, although these screens proved their effectiveness in controlling solar radiation in traditional buildings throughout history. This paper reports on the outcomes of an investigation that studied the influence of perforation percentage of Solar Screens on daylighting performance in a typical residential living room of a building in a desert location. The objective was to identify minimum perforation percentage of screen openings that provides adequate illuminance levels in design-specific cases and all-year-round. Research work was divided into three stages. Stage one focused on the analysis of daylighting illuminance levels in specific dates and times, while the second stage was built on the results of the first stage, and addressed year round performance using Dynamic Daylight Performance Metrics (DDPMs). The third stage addressed the possibility of incidence of glare in specific cases where illuminance levels where found very high in some specific points during the analysis of first stage. The research examined the daylighting performance in an indoor space with a number of assumed fixed experimentation parameters that were chosen to represent the principal features of a typical residential living room located in a desert environment setting. Stage one experiments demonstrated that the screens fulfilled the requirements of the majority of tested cases. Illuminance levels in the examined residential space were satisfactory in 83% of the near zone cases and 53% in the mid-length zone, while the far zone suites 40% of the cases. Screen influence on daylighting was found to be very much dependent on the orientation of the window and time of the day. In stage two, the percentage of annual “Daylight Availability” was very much related to screen perforation percentage. As perforation percentage decreased, the percentage of Daylit and Over lit spaces decreased. At the same time, Partially Daylit areas of the space increased with similar percentages irrespective of the orientation. As a result of the twofold research stages, it is recommended to utilize a minimum of 80% perforation percentages for spaces similar to the tested case in the South orientation. In stage three, an initial investigation suggests that the use of screens can significantly reduce the occurrence of glare phenomena. Also, it is suggested to study the efficiency of designing Solar Screens that have non-uniform perforation ratios. These could prove useful in improving the illuminance levels in the mid-length and far zones of the unsatisfactory cases. In conclusion, minimum perforation percentages for Solar Screens were presented for specific design cases that encompassed different orientations, seasons and time of the day. In addition, a tool that could be used by architects for based on required annual “Daylit” areas for the design of Solar Screens that effectively achieve functional needs was provided. [Copyright &y& Elsevier]

Abstract: In addition to the conversion efficiency of a photovoltaic panel, the maximum power point tracking (MPPT) method also plays a central role to harvest most energy out of sun. The MPPT unit on a moving vehicle must keep tracking accuracy high in order to compensate rapid change of insolation due to dynamic motion of the vehicle. In this paper, some problems of a PV system associated with a moving vehicle are addressed, and a modified quadratic maximization MPPT algorithm is proposed. Theoretical PV performance is linked to the experimental test followed by the Sandia dynamic test protocol to verify the proposed MPPT method. Finally, experimental result on a model ship is discussed. [Copyright &y& Elsevier]

Abstract: This paper presents a non-tracking microstructured light redirecting device, which can be integrated into architectural glass. When fixed in the upper area of a window above eye level it redirects the light from solar altitudes between 15° and 65° and illuminates a room without causing glare. Ray-tracing calculations are employed as a tool for identifying suitable configurations and geometries. The results of the simulations show the advantage of combinations of lens-like with prism-like geometries in comparison to conventional microprism arrays regarding the overall light redirection efficiency as well as the producibility. The redirecting device is more lightweight, gives better integration options and is producible in a more economic manufacturing process as systems with similar performance. Measurements of cast silicone prototypes (100mm×100mm×4mm) confirmed the simulation results. By now the performance has also been shown by large scale industrially produced acrylic panels with dimensions of 1500mm×400mm×4mm. [Copyright &y& Elsevier]

Abstract: This paper reported a dedicated study of a novel façade-based solar loop heat pipe (LHP) water heating system using both theoretical and experimental methods. This system employs a modular panel incorporating a unique loop heat pipe that is able to serve as part of the building façade or a decoration layer of the façade, thus creating a façade integrated, low cost, highly efficient and aesthetically appealing solar water heating structure. Taking into account heat balances occurring in different parts of the system, e.g., solar absorber, heat pipes loop, heat exchanger and storage tank, a dedicated computer model was developed to investigate the dynamic performance of the system. An experimental rig was also established to evaluate the performance of such a prototype system through measurement of various operational parameters, e.g., solar radiation, temperatures and flow rates of the heat pipe fluid and water. Through comparison between the testing and modelling results, the model has been approved to be able to give a reasonable accuracy for predicting the performance of the LHP system. Two types of glass covers, i.e., double glazed/evacuated tubes and single-glazing plate, were applied to the prototype. It was found that for both covers, the heat pipe fluid temperature rose dramatically at the start-up operation and afterwards remained a slow but steady growth; while the water temperature remained a steadily growing trend throughout the operational day. The temperature rise of the circulated water at 1.6l/min of flow rate was around 13.5°C in the double-glazed/evacuated tubes based system and 10°C in the single-glazing based system; correspondingly, their average solar conversion efficiencies were 48.8% and 36%, and the COPs were 14 and 10.5 respectively. In overall, the double-glazed/evacuated tubes based system presented a better performance than the single glazing based one. [Copyright &y& Elsevier]

Abstract: In this paper, the fabrication of silicon nanodome solar cells on crystalline wafers is reported. Crystalline silicon was patterned by ebeam lithography to define the silicon nano pillars with diameter of 100nm, 1μm and 5μm. Unlike conventional bottom up growth of silicon nanowire from gold (Au), our method is free from contaminant. Consequently, it is a valuable method to fully evaluate the effect of nanostructures on solar cell performances. The fabricated devices were characterized through scanning electron microscopy, absorption measurements, illuminated solar cell I–V characteristics and monochromatic incident photon-to-electron conversion efficiency. [Copyright &y& Elsevier]

Abstract: The aim of this paper is to optimize the energy performance of cylindrical cross section evaporative wind towers as passive systems for thermal conditioning of urban spaces. Two theoretical models, a thermal model and a fluid model, have been developed to characterize the evaporative system and the tower design respectively. The thermal model evaluates the tower operation when the fan and the nozzles are working, giving as result the difference between the outlet temperature and inlet temperature. This model has been used to analyze the thermal response of the system to fluctuations in design parameters (water flow, air flow and absorption coefficient of the plastic). To that effect, three one-parametric and one multi-parametric optimization have been done. The fluid model describes the tower operation when the fan and the nozzles are not working, giving as result the wind behavior through the tower. Additional configurations of the wind tower have been evaluated: changing the number of the wind catcher openings, varying the height of the internal walls of the tower and modifying the geometry of the lower ventilation apertures. [Copyright &y& Elsevier]

Abstract: In this paper, we report on the effect of chemical vapor etching-based porous silicon (PS) on the performance of multicrystalline silicon solar cells performed via deep n+/p junction-type structures. Chemical vapor etching of silicon leads to the formation of porous silicon (PS) nanostructures that dramatically decrease the surface reflectivity from 30% to about 8%, and increase the minority carrier diffusion lengths from 90μm to 170μm. As a result, the short-circuit current density was improved by more than 20% and the fill factor (FF) by about a 10%. An enhancement of the photovoltaic conversion energy efficiency of the solar cells from 7% to 10% was observed. This low-cost PS formation process can be applied in the photovoltaic cell technology as a standard procedure. [Copyright &y& Elsevier]

Abstract: This paper shows the numerical investigation of the developed solar-desiccant cooling system applied in the East Asian climatic conditions with two different desiccant wheel coating materials – the Silica-Gel (SiO2) and the Titanium Dioxide (TiO2). The developed and validated numerical model of the system is currently used in the present study incorporating the two new materials in the desiccant wheel. The system was applied in temperate climate (Beijing and Tokyo), subtropical climate (Taipei and Hong Kong) and tropical climate (Manila and Singapore). The study showed that the specification of the solar-desiccant cooling system varies depending on the climatic conditions. It showed that the required flat plate collector area was getting larger from the temperate climate to the tropical climate. The storage tank requirement was getting bigger in the tropical climate compared to the subtropical and temperate climate. The volumetric flow rate of air was getting higher from temperate climate to tropical climate. In the comparison of the two materials, it was found that the Titanium Dioxide (TiO2) can support lower indoor temperature and humidity ratio than the Silica-Gel (SiO2) with the same specification of the solar thermal system and desiccant cooling system. In general, the solar-desiccant cooling system can provide the required indoor temperature and humidity ratio. However, for the hot and humid climate such as in tropical, large size of the solar thermal system is needed. In addition, higher volumetric flow of air to support the high cooling load is required. With regard to the new material, Titanium Dioxide, it is proven to be a good alternative material since it can provide lower indoor temperature and humidity ratio with higher cooling performance than the Silica-Gel. [Copyright &y& Elsevier]

Abstract: The common solar water heater system can meet low temperature requirements, but exhibits very low efficiency in attaining higher water temperatures (55–95°C). In the current paper, a compound parabolic concentrator (CPC)-type solar water heater system experiment rig with a U-pipe was set up, and its performance in meeting higher temperature requirements was investigated. The experiments were conducted in December at Hefei (31°53′ N, 117°15′ E), in the eastern region of China. The system showed steady performance in winter, with overall thermal efficiency always above 43%. The water in the tank was heated from 26.9°C to 55, 65, 75, 85, and 95°C. Through the experimental study and exergetic analysis of the solar water heater system, results of the five experiments showed thermal efficiency of above 49.0% (attaining 95°C water temperature) and exergetic efficiency of above 4.62% (attaining 55°C water temperature). Based on these results, the CPC-type solar water heater system with a U-pipe shows superior thermal performance in attaining higher temperatures and has potential applications in space heating, heat-powered cooling, seawater desalination, industrial heating, and so on. [Copyright &y& Elsevier]