ALBERT

Description: Temperature fields and their transient behaviors are essential subjects to be considered for modeling and design of absorber tubes in concentrated solar power plants. Both subjects have been addressed by various authors. However, the first subject has been primarily solved in the steady state. While the second has been solved by considering transient variations in the environmental or operating conditions, but with a heat conduction model in steady state. To the best of our knowledge, there are no analytical transient two-dimensional (2D) (r, φ) solutions involving nonuniform heat flux distribution (NUHFD) on the absorber tube of a parabolic trough solar collector (PTC). This study aims to obtain an analytical solution for the transient heat conduction in 2D of the absorber tube. The analytical solution was obtained using the method of separation of variables and the superposition principle. Two NUHFD functions were analyzed: a step function and a local concentration ratio (LCR) function. To the first function, the effect of the inlet fluid temperature and efficiency were also studied. The results agree with experimental and numerical results from the literature. The maximum average root-mean-square was near 6.4% for the step function, while the maximum average error was 1% for LCR function. The theoretical energy balances corroborate the validity of the analytical solution. The analytical solution could be useful to compare other theoretical studies (e.g., to prove new numerical schemes), to simulate other parameters of design, and to calibrate experimental tests. Even this work could be extended for nonlinear boundary conditions.

Description: An experimental investigation was conducted to demonstrate the effects of materials on the heat transfer characteristics of R410A during evaporation and condensation inside two horizontal plain tubes with the same inner diameter of 6 mm, but with two different materials of aluminum and stainless steel. The variation of vapor quality for the test section was kept in the range of 0.2–0.9, while mass velocities were allowed to vary from 100 to 400 kg/m2/s1. First, a series of single-phase and repetitive experiments were conducted to verify the accuracy and reliability of the test rig. Results of the evaporation experiments show that the plain aluminum tube performs best for all tested mass velocities. Several different correlations were employed to predict the present data, and their predictive ability was compared and discussed. Results indicate that the Liu and Winterton correlation could accurately predict the present results except for low mass velocities. Roughness effects were accounted for employing a correction factor. The larger roughness of the stainless steel tube was supposed to make the stainless steel tube perform better if roughness effects were accounted for, so the better performance of the aluminum tube was mainly attributed to the material effects. The pool boiling heat transfer as predicted by the VDI model was compared with the experimental results, and more obvious material effects have been found for pool boiling conditions. The minor differences between the two tubes in this case may be explained by the nucleate boiling suppression and incomplete wetting. For the condensation experiments, little difference was found between the two tested tubes, which means that the material and roughness effects may have had little influence on the thermal performance during condensation.

Description: The abundant spatial and temporal availability of solar energy has been fueling many researches and have been the reason for the proliferation of solar energy applications in the past decades. Many of these applications involve heavy investments and thus require highly accurate and reliable long-term average solar data for efficient deployment of solar energy technologies. Since ground stations are costly, site-specific, scarce and cannot provide long-term solar data, satellite-derived data is the next best alternative. However, satellite models are often unable to capture the complex local climatological variations of a given site. As such, short-term high precision solar ground measurements are used to train the satellite model so as to improve the accuracy of long-term solar estimates. There exist several site adaptation techniques to perform this task. However, to the knowledge of the researchers, no comparative study has been conducted to establish which site adaptation technique is the most effective. In this study, a robust methodology has been proposed to compare the effectiveness of four site adaptation techniques for monthly and yearly data sets using novel key performance indicators. Ground measurements from 12 stations in the tropical islands of Mauritius, Rodrigues, and Agalega were used to adapt satellite data obtained from HelioClim-3 database using different techniques. Three new nonlinear site adaptation techniques have been proposed: adjustment technique (Technique 2), compensation technique (Technique 3), and relationship technique (Technique 4). The first part of the study showed that 67–100% of the data sets were best approximated with sixth-order polynomials for the three nonlinear techniques. The second part revealed that Technique 1 (linear method) and Technique 2 were most appropriate for maximum and average data sets, respectively. The results were such that Technique 2 and Technique 1 provided best approximations for77.9–83.3% and 40.7–58.3% of average and maximum data sets, respectively. In the third part of the study, only Technique 2 provided remarkable improvements for all statistical metrics with respect to the original monthly data sets (113–118 data sets). The analysis reported 57.6–89.9%, 49.8–68.0%, 67.4–87.3%, 53.8–63.1%, 45.0–64.0%, 7.7–9.6% and 2.7–4.7% mean improvements for mean bias error (MBE), mean absolute bias error (MABE), mean percentage error (MPE), mean absolute percentage error (MAPE), root-mean-square error (RMSE), Nash–Sutcliffe (NSE), and coefficient of determination (COD), respectively, for Technique 2. Similar results were observed for yearly average data sets while the appreciation was shared among all four techniques for yearly maximum data sets, with Technique 1 having a slight advantage.

Description: Satellite-based solar power data is becoming more and more important because of its continuous temporal and spatial availability. However, its reliability can be enhanced through quality control and calibration against ground-based measurement data. Here, a holistic methodology is employed for the adaptation of satellite-based data for estimating solar energy. For the purpose, high-quality ground-based measurement data and satellite-based datasets are assessed across 12 sites in three small islands located in the Indian Ocean. Initially, both datasets go through a rigorous quality control process. A quantitative analysis of irradiance and insolation data is then conducted. Eventually, site adaptation of satellite-based data is performed using bias removal technique and statistical analysis of datasets. A set of seven statistical performance indicators is used to support the assessment. Analysis of datasets shows that adaptation of peak values should be performed separately. Results showed that despite the small surface areas of the islands studied, a spatial variation of insolation can be depicted. A temporal variation of insolation is also noted with a peak in the summer and low insolation levels in winter. Peak irradiance values tend to exceed solar constant for all sites. Variations of peak irradiance can only be noticed in ground-based measurement data. While insolation levels are comparable in the summer season for all the sites, insolation levels in the winter season are higher in the sites with lower latitudes. Calibration factors for peak irradiance, monthly and annual average irradiance as well as yearly insolation are presented.

Description: This paper describes the development of a computer model to predict the performance of a discrete layer wire mesh solar volumetric air receiver. The model accounts for all important energy transfer processes within the absorber and allows for the use of two different types of wire mesh screens. Model predictions are compared to experimental results for validation purposes. An optimum design analysis is performed to determine optimum receiver characteristics and performance. Results show a predicted efficiency in the range of 89 percent to 87 percent when the outlet air temperature is between 700°C and 820°C, respectively.

Description: An approximate analytical solution to the transient heat-conduction problem in a large composite region with an internal cylindrical source is presented. The generalized orthogonal expansion technique is utilized in deriving the solution. Such problems are encountered in the design or simulation of the ground-coupled heat exchangers used in ground-coupled heat pumps. Solutions are presented for the nondimensional temperature as a function of the ratios of the thermal conductivities and thermal diffusivities of the two materials in the layers. To verify the correctness of the solution, comparisons are made between the two-layer composite solution and the classical homogeneous cylindrical source solution and a finite difference solution.

Description: Power augmentation and velocity measurements in the wake of a HAWT blade with Mie type tip vane (a tip device on the main blade) are presented. The maximum Cp with a Mie type tip vane is found to be 15 percent larger than that without the Mie type tip vane. Power augmentation caused by the Mie type tip vane is mainly due to the reduction of tip vortex and the diffusing effect by the Mie type tip vane. The effects of a Mie type tip vane are quantitatively verified by the velocity distributions around the tip of the main blade. The velocity distribution was measured by three-dimensional hot wire probes, which measured the axial, radial, and tangential velocity components. The circulation distributions along the main blade with a Mie type tip vane and without a Mie type tip vane were obtained from the measured velocity distributions. A strong reduction of bound vorticity is found for the main blade tip without the Mie type tip vane, whereas the bound vorticity persists on the main blade tip with the Mie type tip vane.

Description: An approach to the design of active window shades is developed to control the direct solar gain through a window. Using simple actuation hardware and sensors, a control strategy is presented that automatically adjusts window shades to save HVAC energy by controlling direct solar radiation passing through a window. The control algorithm is based on a simple approach that admits direct light in the winter and blocks the direct light in the summer, while providing shade adjustment that affords maximum visibility through the window. Cloudy skies or indirect sun result in horizontal placement of the shades, and the shades close at night. The implementation uses two thinfilm photovoltaic cells as sensors and a control algorithm that is independent of the window orientation, latitude, or solar time, so that it operates properly in any installation location. Preliminary analytic and test results show significant energy savings when the automatic window shades are compared with a window without shades, and with a window outfitted with fixed horizontal shades.

Description: In recent years the problem of controlling the temperature of oil leaving an array of parabolic trough collectors has received much attention. The control schemes developed have in general utilized a feedback control loop combined with feedforward compensation. The majority of the published papers place the emphasis almost entirely on the design of the feedback control loop. Little or no attention has been paid to issues involved in the design of the feedforward controller. This paper seeks to redress this imbalance by concentrating upon the design and development of a feedforward controller for the ACUREX distributed solar collector field at the Plataforma Solar de Almeria. Different methods of combining feedback and feedforward will be assessed and experimental results will be presented in order to support any theoretical observations made.

Description: A recent French contribution in the field of surface hardening of steel using concentrated solar energy is presented. Single spot and continuous scanning processes have been investigated in a small-scale solar furnace. Hardened regions of 0.5–1.5 mm in thickness have been obtained on specimens of carbon steel, resulting from the transformation hardening process. Compressive stresses are induced in the thermally affected layer, without tensile peak in the bulk.

Description: An analytical model is developed to predict the annual variation of soil surface temperature from readily available weather data and soil thermal properties. The time variation is approximated by a first harmonic function characterized by an average, an amplitude, and a phase lag. A parametric analysis is presented to determine the effect of various factors such as evaporation, soil absorptivity, and soil convective properties on soil surface temperature. A comparison of the model predictions with experimental data is presented. The comparative analysis indicates that the simplified model predicts soil surface temperatures within ten percent of measured data for five locations.

Description: A performance assessment was conducted for a solar–biogas hybrid micro gas turbine integrated with a solar power tower technology. The considered system is a solar central receiver integrated with a micro gas turbine hybrid with biogas fuel as a backup. The Brayton cycle is designed to receive a dual integrated heat source input that works alternatively to keep the heat input to the system continuous. The study considered several key performance parameters including meteorological condition effects, recuperator existence and effectiveness, solar share, and gas turbine components performance. This study shows a significant reduction in CO2 emissions due to the utilization and hybridization of the renewable energies, solar, and biogas. The study reveals that the solar–biogas hybrid micro gas turbine for 100-kW power production has a CO2 emission less than a conventional fossil fuel gas turbine. Finally, the study shows that the method of power generation hybridization for solar and biogas gas turbines is a promising technique that leads to fuel-savings and lower CO2 emissions.

Description: A novel multi-generation system (MGS) that comprises two absorption cycles, two Rankine cycles (RCs), and a hot water (HW) production chamber is studied in this research. It is designed to utilize the waste heat from the first Rankine cycle as a thermal energy input for the second Rankine cycle and a double-effect absorption cycle (DEAC). The waste heat from the second Rankine cycle serves as heat input to a single-effect Rankine cycle. Regeneration and reheat principles are also applied to the Rankine cycles. The objective of the study is to develop an MGS without a gas cycle that can achieve higher energy and exergy efficiencies. Two concentrated solar technologies, namely, parabolic trough collectors (PTCs) and heliostats are used to power the designed system. The environmental benefit of the system is also analyzed. The energy and exergy efficiencies of the novel MGS presented in this study are 73.11% and 50.72%, respectively. The application of solar thermal technologies to power the system reduces the overall energy and exergy efficiencies, respectively, to 56.12% and 38.39% for the solar PTC and 41.89% and 29.06% for heliostats. The energy and exergy coefficient of performances (COPs) are 0.754 and 0.349 for the single-effect absorption cycle (SEAC), respectively. As much as 752.7 kg/h of CO2, 2.13 kg/h of NOx, and 4.21 kg/h of SOx will be saved from being emitted to the atmosphere.

Description: The structural and architectural elements of building-integrated photovoltaic-thermal (BIPVT) systems are made up of photovoltaic (PV) modules and these are required to be fixed at an optimum inclination angle for generating maximum exergy. This work presents an attempt to determine the amount of exergy generated by an optimally inclined double-storied BIPV thermal system by considering the actual cyclic nature of insolation, surrounding air temperature, PV cell temperature, intermediate slab temperature, and the chamber temperature. The insolation value, which is computed by an anisotropic sky model along with these cyclic variables, is used for solving the set of governing differential equations for evaluating the exergy of the system. Other influencing parameters of the BIPV thermal systems such as air changes in both chambers, packing factor of PV module, the orientation of PV module, and thickness of the intermediate slab are considered for finding its effect on the total exergy of the system. Numerical results show that for packing factor more than 0.6, there is no significant change in total heat exergy with respect to the inclination angle. For packing factor more than 0.3, the generation of electrical exergy exceeds the heat exergy, and the overall exergy of BIPVT system decreases with rise in packing factor (βm) up to 0.3 and then rises nonlinearly.

Description: The interest of the direct normal irradiation (DNI) estimation is important in the evaluation of the solar potential and, consequently, for data correction and expansion of the historical series. In this study, a review of the performance of 16 models of radiative transfer was performed. These models are used to estimate DNI on a clear day in Botucatu/SP region located in Brazil. The revised models are categorized into two classes: simple models (11 models: ASH, MAJ, ALLEN, GH, P1, HLJ, FU, KU, H1, IP, and INC) and complex models (five models: BIRD, IQ, MRM5, P2, and YANG). The evaluation methodology used here is consistent with the literature. The input parameters were estimated and a statistical analysis using relative-mean-bias-error (rMBE), root-mean-square-error (rRMSE), and mean absolute percentage error (MAPE) indicators were performed to validate those models. The results indicate that the complex models (that require more atmospheric inputs) generally performed better than simpler models. Despite the consistent limitations in the use of estimated parameters, the performance of the models can be considered satisfactory. The best performances are highlighted for models MRM5 and YANG. Simple models ASH and IP performed similar to complex models. These results were confirmed using frequency distribution and the cumulative frequency analysis. These results are important for engineers of solar systems to use the best model and select the most suitable locations for installing a small or large solar plant.

Description: A method for optimizing the geometrical layout for a façade-mounted solar photovoltaic array is presented. Unlike conventional studies, this work takes into account the finite height of the façade, which is more realistic. The proposed analytical relationships and optimization routine evaluate the best tilt angle and the number of panels such that the whole layout receives the maximum solar radiation, year-round. This is achieved while ensuring that the panels are at a safe minimum distance to avoid mutual shading issues. Validation was performed by simulating the scenarios and comparing the results with manual measurements taken in a three-dimensional drafting program. The method was then used to evaluate designs for facades with a variety of orientations, hypothetically located in Auckland, New Zealand. For this case study, the per-panel and total year-round energy accumulation associated with the number of panels were determined. The results showed that more panels can be integrated into constrained fields by sacrificing the year-round best value of the tilt angle. Therefore, increasing the number of panels may decrease the energy accumulation performance.

Description: This paper analyzes the direct solar vapor generation of acetone by solar radiation falling on the heat pipes of an evacuated tube collector (ETC) that can activate a domestic scale organic Rankine cycle (ORC). The irradiance from the sun determines the mass flow of acetone along the horizontal manifold of the ETC to produce vapor at the collector outlet. A scilab code is developed to simulate the flow of acetone inside the manifold where subcooled acetone undergoes heating and evaporation process. Simulation is run from 60 °C to a saturation temperature of 120 °C at a pressure of 604 kPa, vapor qualities from 1% to 100%, and solar radiation from 300 to 1100 W/m2. The Kattan–Thome–Favrat flow boiling model is used to obtain the two-phase local heat transfer coefficients along the horizontal manifold, and it is validated with the numerical and experimental values of ammonia. The ORC system can generate 218 kWh/year of electrical energy, a thermal power capacity of 1616 kWh/year and achieve an ORC efficiency of 84.4%. The solar-ORC has a thermal efficiency of 3.25% and an exergy efficiency of 21.3% with a solar collector of 2.84 m2.

Description: Air conditioning systems (ACSs) represent one of the main demands for electricity in residential, commercial, and industrial buildings. The use of a photovoltaic air conditioning unit (PVACU) represents an attractive application to this demand for reasons such as environmental concerns and the match between diurnal cooling load and solar resource. A PVACU consists of a photovoltaic generator (PVG) that supply an ACS through direct current to direct current and frequency converters, without energy storage. This system considers the natural adjustment of the ACS cooling capacity according to the PVG power. Modeling the ACS, the PVG, and the thermal load (TL) makes possible to evaluate PVACU performance. For this, a small library’s TL and an ACS supplied by a PVG were used as case study. The PVG installed capacity assumes values of 700, 1000, and 1400 Wp. The simulation results show that the PVACU with a 1400 Wp PVG would be sufficient to regulate internal temperature within international comfort standards in the range of 20 °C to 24 °C. According to the data obtained in the simulations, it was possible to conclude that the PVACU has a large potential to be used in air conditioning of other environments in regions with Amazonian climatic conditions.

Description: Wind turbine technology has been used to pump water since ancient history. Direct mechanically coupled wind turbines are the most common method for pumping water to croplands and livestock. Many more recent wind turbines are electrically coupled, with the water pump connected to the wind turbine via a motor-generator connection. With electrical coupling, the distance and location of the water pump is independent of the location of the wind turbine. Therefore, the wind turbine can be located at an optimal wind energy site while the water pump is close to the water well or water tank. This paper analyzes a water-pumping system consisting of a wind turbine, a permanent magnet synchronous generator, an induction motor, and a centrifugal-type water pump.

Description: Direct steam generation collectors are considered with the aim to improve the performance of a parabolic trough collector leading to a reduction of operating costs of solar electric generation systems. In this study a hydrodynamic steady state model is developed and linked with a thermal model to optimize the performance of once-through direct steam generation solar collectors. The hydrodynamic model includes flow pattern classification and a pressure drop model. Flow pattern maps for typical DSG collectors with horizontal and inclined absorber tubes are generated to investigate the variation of flow conditions with radiation level, tube diameter, tube length and flow rate. Two-phase flow frictional pressure drop correlations for the range of operating conditions in a DSG collector are selected from the wide range of published correlations by comparison with experimental data for typical steam-water flow conditions in a DSG collector. Pressure drop is calculated for different operating conditions for both horizontal and inclined solar absorber tubes. Alternative operational strategies are evaluated to achieve optimum performance of a direct steam generation collector at different radiation levels. [S0199-6231(00)00101-5]

Description: Organic solar cells are considered to be the promising solar technology for the coming year because of their ease of manufacture. In the present study, the Aloe Latex as a yellow orange Solid (ALS) collected from the leaves of Aloe Vera plant (aloe barbadensis miller) was used as a natural and cheap sensitizer thin film. The ALS powder was analyzed using X-ray diffraction,UHPLC-MS, and Fourier transform infrared (FT-IR) spectroscopy to determine the chemical composition and the structural properties. While the impedance spectroscopy was performed for the dielectrical properties. The optical properties were detemined using UV–Vis absorption of the ALS thin film deposited in a glass. For the first trial, a planar heterojunction solar cell using zinc oxide (ZnO) thin film as an electron selective layer was build. The band gap was found to be 1.88 eV. The electrical properties of the investigated cell by the current–voltage (I–V) measurements showed an open-circuit voltage (Voc) of 0.74 V, an important efficiency of 0.50%, and a great fill factor (FF) of 0.70.

Description: Solar radiation is a rich and clean source of energy. It can be collected and converted to thermal energy with the help of flat plate collectors called the solar-assisted air heater. Because of the low coefficient of heat transfer of air, the solar-assisted air heater has low thermal performance which can be improved by creating local turbulence using surface roughness on the heat transferring plate. The present investigation has been conducted to perceive the influence of the curved-ribbed element with gap on flow and heat transfer. The roughness element is defined by using five non-dimensionlized parameters, i.e., relative roughness width (W/w), relative roughness pitch (P/e), relative gap width (g/e), relative roughness height (e/D), and relative gap distance (d/x). The radius of the curvature of the curved rib-element is kept constant and the experimental measurements were done under quasi-steady state. The thermohydraulic performance parameter improved by 3.61 times the smooth flat plate solar air heater (SAH), in curved-ribbed SAH for W/w = 3, P/e = 8, g/e = 1, e/D = 0.045, and d/x = 0.65 at Reynolds number of 23,000. The generalized relation for heat transfer and flow characteristics is also being developed and the predicted Nusselt number and friction factor with the accuracy of ± 7.5% and ± 6.7%, respectively.

Description: In this technical brief, the classic actuator disk theory is revisited with a view to shed some light on the singularity of the flow at the edge of the disk where the vortex tube starts and where vorticity is generated. The study is carried out using small perturbation assumption in two-dimensions and simplified boundary conditions in all cases. The problem of the two-dimensional thin cambered plate with constant vorticity distribution is solved and the leading edge singularity is analyzed as it is believed to be relevant to the axisymmetric flow at the actuator disk edge. Next, the velocity components induced by the cylindrical vortex tube of constant vorticity are obtained via the Biot–Savart law and the near edge behavior is investigated. It is shown that the velocity components behavior is consistent with that of the thin cambered plate with constant loading, thus reinforcing the notion that the axisymmetric slip-line behaves as r − R ∝ −xlnx near the disk edge.

Description: Batch type food dryers are common for drying agricultural produce due to simple in design, but they are prone to nonuniform drying and significant heat cost exclusively if they fall in the medium to large size range. The current study illustrates a solar hybrid food dryer using a gas burner and solar collector (evacuated tube collector, ETC) as heating source along with an inline perforation inside the drying chamber to obtain spatial drying homogeneity. Air distribution was assessed through three-dimensional simulation using computational fluid dynamics (CFD) analysis. Performance trials were conducted under three heating options (ETC, gas, and dual) using green chilies at 60 °C. Throughout drying chamber, under all heating modes, the average difference in drying rates ranged from 0.61 to 1.30 kg water/kg dry matter, demonstrating homogeneous drying. Simulated and experimental results of air distribution were found to be in agreement with each other. Using three options for thermal heating (ETC, gas, and dual) and an overall 58% efficiency for evacuated tube collector, the specific energy for moisture evaporation was found to be 4.5–5.7 MJ/kg and specific product energy 19.2–24.9 MJ/kg. In case of dual heating option, the energy supplied by solar and gas sources for a 20 hours period was 50.64% (160.22 MJ) and 49.35% (156.13 MJ), respectively. Compared with dual heating option, energy cost can be reduced by 68% if only solar energy is used as a heating option but with a protracted drying time.

Description: We research the investment potential of wind energy in Jordan. The capacity factor of the first large-scale wind farm in the country, Tafila Wind Farm, was found to be 33.1%, based on actual energy production during its first year of operation. The best performing turbine in the farm achieved a capacity factor of 39.1%. Other eight sites, which are expected to have such capacity factors were subjected to techno-economic investigation utilizing 52 different turbine models of nameplate capacities range from 1.0 to 5.0 MW. A capacity factor higher than 25.0% can be achieved at all the studied sites. The average levelized cost of electricity of the 52 turbines at the eight sites is 0.0708 $/kWh, and the cost ranges from 0.0452 to 0.1108 $/kWh. A proposed 80 MW farm at every location results in a total capacity of 640 MW and an annual estimated energy generation of 1545.0–2076.0 GWh, around 7.0–9.0% of the country's projected electricity demand in 2020.

Description: Close range photogrammetry is a sensing technique that allows the three-dimensional coordinates of selected points on a surface of almost any dimension and orientation to be assessed. Surface characterisations of paraboloidal reflecting surfaces at the ANU using photogrammetry have indicated that three-dimensional coordinate precisions approaching 1:20,000 are readily achievable using this technique. This allows surface quality assessments to be made of large solar collecting devices with a precision that is difficult to achieve with other methods.

Description: In the present work, a solar humidifier suitable for solar thermal energy-driven humidification–dehumidification desalination has been proposed and experimentally investigated. The proposed solar humidifier compacts the solar heater and humidifier into a single component while reducing energy costs by utilizing solar thermal energy. Several local flow storage and distributor elements are created in the absorber surface that produces a “dam effect” in combination with stainless steel mesh and airflow baffles. The effect of varying flowrates of air and water, inlet water temperature as well as inlet relative humidity on the performance of the solar humidifier is investigated. Humidity based normalized gain (NGhumidity) versus solar humidifier efficiency curve, which depicts a heat and mass performance of the solar humidifier, is reported. This curve is analogous to the normalized gain versus collector efficiency curve of the solar water/air heater. The productivity of the present system is compared with the published results of similar studies. Best mean productivity of 838.5 g/m2/h and best instantaneous productivity of 955.2 g/m2/h were achieved using a present solar humidifier, showcasing the effectiveness of the proposed approach. The comparison of the performance of the solar humidifier with the performance of conventional configuration having separate heating and humidification is also carried out. It was found that the investigated solar humidifier (internal heating configuration) does perform the same in terms of utilization of solar energy for evaporation, if not better, than the conventional separate humidifier and heater (external heating configuration).

Description: Previously reported studies have shown that the volumetric receivers have lower radiative and convective losses, leading to higher efficiency. However, the conventional volumetric receivers are difficult to use along with the thermal storage systems, owing to the use of air as the heat transfer fluid. Molten salt, having high heat capacity, emerges as a suitable candidate to be employed as the heat transfer fluid and for storing thermal energy in the storage devices. It is challenging to use the molten salt in the conventional volumetric receiver configuration; therefore, a novel design called Liquid Volumetric Plated Cavity Receiver is proposed, where the solar salt is used as heat transfer fluid. It consists of a parallel arrangement of hollow plates in an open cavity. Solar radiation concentrated by the heliostat field is absorbed on the outer surface of the hollow plates. The heat is then taken away by the molten salt flowing inside the hollow plates. The plates are arranged such that the molten salt gets heated up within the volume of the enclosure, effectively mimicking the heating performance of the volumetric receivers. Using an analytical model for heat losses, it is observed that the losses are very sensitive to the aspect ratio of the aperture and depth of the receiver. The effects of receiver inclination, plate orientations, radiation incident at the aperture, and surface emissivity have been investigated as well. The results show that a Liquid Volumetric Plated Cavity Receiver increases the efficiency (by ∼3%) as compared with that of the simple cubic receiver.

Description: This paper discusses procedures for creating calibrated building energy simulation programs. It begins with reviews of the calibration techniques that have been reported in the previous literature and presents new hourly calibration methods including a temperature bin analysis to improve hourly x−y scatter plots, a 24-hour weather-daytype bin analysis to allow for the evaluation of hourly temperature and schedule dependent comparisons, and a 52-week bin analysis to facilitate the evaluation of long-term trends. In addition, architectural rendering is reviewed as a means of verifying the dimensions of the building envelope and external shading placement as seen by the simulation program. Several statistical methods are also presented that provide goodness-of-fit indicators, including percent difference calculations, mean bias error (MBE), and the coefficient of variation of the root mean squared error (CV(RMSE)). The procedures are applied to a case study building located in Washington, D. C. where nine months of hourly whole-building electricity data and sitespecific weather data were measured and used with the DOE-2.1D building energy simulation program to test the new techniques. Simulations that used the new calibration procedures were able to produce an hourly MBE of –0.7% and a CV(RMSE) of 23.1% which compare favorably with the most accurate hourly neural network models (Kreider and Haberl, 1994a, b).

Description: A transient heat transfer model is developed to study the thermal performance of a high-temperature solar thermochemical reactor for metal oxide reduction. The solar reactor consists of an indirectly irradiated tubular fluidized bed contained in a solar cavity receiver. Radiative heat transfer in the cavity, modeled with the Monte Carlo ray-tracing method, is coupled to conduction in the tube and cavity walls. Incident radiation distributions from a diffuse radiative source and a high-flux solar simulator are implemented separately in the model to study the influence of incident radiation directionality on the performance of the reactor. Maximum temperature, maximum thermal stress, start-up time, energy balance, and particle reduction rate for the proposed reactor concept are calculated to inform the design and optimization of a prototype reactor.

Description: Solar chimney is a passive renewable technology, adopted and followed widely for the application of room ventilation and power production. It requires a wide space for operation. Hence, an effective heat transfer mechanism is required within the available space to improve the performance. The solar chimney is integrated with a solar still using an external condenser to effectively utilize the energy released during the condensation of water vapor in the external condenser. The external condenser acts as an additional heat source besides the solar collector in the solar chimney. The experiments were conducted with the solar chimney of heights 1 m and 2 m, by considering the effects of an external condenser in both summer and winter. Heat transfer studies on the external condenser are also made to determine the effectiveness and the number of transfer units. The temperature and mass flow rate of vapor in the still are the influential parameters on the effectiveness of the external condenser. The condensation energy released from the external condenser increased the daily average air velocity by 14.9% and 22.4% in summer and winter, respectively. However, the overall solar chimney efficiency was improved by 37.1% in summer and 14.5% in winter for the integrated system with the chimney of height 2 m.

Description: In this paper, a portable photovoltaic (PV)-powered vaccine carrier intended for “hard to reach” areas that suffer luck of electricity and transportation has been proposed. The design of the proposed system has been analyzed and each of its elements (PV panel, battery, converter, and refrigerator) has been deeply studied, modeled, and validated through simulation as well as experimentally. These elements are carefully selected to form a robust, light system and at a reasonable cost. To maximize energy production, the PV panel control using a maximum power point tracking (MPPT) controller has been examined. Moreover, to ensure an appropriate battery charging and thereby prolonging battery life, state of charge (SOC) estimation using the Luenberger observer has been studied. The proposed system has been investigated under different climatic conditions. It was subjected to different daily profiles of irradiance and temperature measured in three seasons, namely, winter, spring, and summer in Marrakesh, Morocco. As expected, for all studied cases, the proposed PV-powered vaccine carrier works adequately and maintains continuously a low temperature of 4 °C (as required by the World Health Organization (WHO) for vaccine preservation) for a journey of 15 h. These results making it a very suitable option to transport vaccines safely in remote areas.

Description: Natural convection heat transfer was investigated in a scaled test facility of a Trombe wall geometry. A silicone oil was employed as the convecting medium to obtain large Rayleigh numbers (up to 1.5 × 1010, based on enclosure height) characteristic of full-scale Trombe wall in a passive solar building. The main objectives were to study effects of Trombe wall nonisothermality and location on heat transfer, fluid temperature and fluid flow patterns. As expected, Nusselt numbers were slightly larger on the Trombe wall space side than on the living space side. Nusselt numbers increased slightly as the mass transfer gaps in the Trombe wall were increased. The results were verified, for the zero gap case, by comparing with previous studies. Physical understanding of the convection process was enhanced by flow visualization data. The information obtained should be useful to designers in optimizing overall building performance for passive solar heating.

Description: Following several successful applications of feedforward neural networks (NNs) to the building energy prediction problem (Wang and Kreider, 1992; JCEM, 1992, 1993; Curtiss et al., 1993, 1994; Anstett and Kreider, 1993; Kreider and Haberl, 1994) a more difficult problem has been addressed recently: namely, the prediction of building energy consumption well into the future without knowledge of immediately past energy consumption. This paper will report results on a recent study of six months of hourly data recorded at the Zachry Engineering Center (ZEC) in College Station, TX. Also reported are results on finding the R and C values for buildings from networks trained on building data.

Description: The thermal and electrical performance of the solar photovoltaic (PV) panel of a solar photovoltaic thermal (PVT) air system is determined experimentally in the present work. For this purpose, a data acquisition system was developed indigenously using ATMEL MEGA 2560 and ATMEL 328 microcontrollers. The parameters measured were PV panel surface temperature, inlet and outlet air temperatures, PV current, and voltage. The parameters were also compared with those of a reference PV system to demonstrate the effect of cooling of PV panel on its electrical power output. The experiments were performed in the locality of Tiruchirappalli, Tamilnadu, India (11 deg N latitude, 79 deg E longitude) and the working of the PV data acquisition was tested for a period of 3 months from February to April 2017. The results indicate acceptable working of the indigenously developed PV/PVT data acquisition system.

Description: This study presents the overall performance of a double-pass solar air heater (DPSAH) with three different configurations: (i) double-pass solar air heater without fins and heat storage (DPSAHWF), (ii) double-pass solar air heater with longitudinal fins and without heat storage (DPSAHLF), and (iii) double-pass solar air heater with longitudinal fins and heat storage (DPSAHLFHM). Five longitudinal fins on the upper channel and granular carbon at the bottom of lower channel as heat storage material were used for the analysis. Each configuration was examined for the following flowrates of air (ṁ1 = 0.008 kg/s, ṁ2 = 0.012 kg/s, and ṁ3 = 0.016 kg/s). The results show an improvement in thermal efficiency with an increase in the air flowrate. The outlet air temperature increases considerably with a decrease in flowrate, for all the three orientations. The lowest and the highest efficiencies during the peak sunshine hours were recorded as 33% and 65% for the conventional heater and the heater with fins and heat storage material, respectively. A maximum of 849 W/m2 of solar intensity was recorded during the test period. The system is also examined for thermal discharge after the sunshine hours to determine the effectiveness of the heat storage material.

Description: This paper presents some of the experimental results from a study conducted to demonstrate the potential use of photocatalytic oxidation for decolorization and COD reduction of wastewater from 5–fluorouracil manufacturing. A series of batch experiments, were carried out using diluted solutions of the wastewater with 0.1 percent w/v TiO2. Low pressure mercury lamps were used to simulate the UV part of sunlight. The experiments showed that a complete decolorization and a substantial reduction of COD was achieved within 20 hours with a 20 percent solution. During the reaction period, the pH was noted to decrease considerably, indicating formation of acids. Adding hydrogen peroxide to the solution was found to significantly increase the reaction rates. Adding 2400 ppm of H2O2 gave an 80 percent decrease in color in one hour and a 70-80 percent decrease in COD in 20 hours. The influence of UV-light intensity was also examined. This experiment showed that with a UV-intensity of 15 W/m2, i.e., a cloudy day, the decolorization rate was still considerable, while the COD reduction rate was very low.

Description: The use of artificial roughness is an efficient and commercial way to appreciate the thermal performance from the collector to the air in solar air heater ducts, for numerous applications such as space-heating, crop-drying, and seasoning of timber industrial purpose. In this paper, the tentative inquiry on thermal enactment using new-fangled of three-sided roughened quadrilateral duct solar air heater having an alignment of multiple-v and transverse wire is performed and compared the outcomes with smooth duct air heater under similar operational circumstances. The modification of an arrangement and operational constraints is inspected within the restrictions, the moral of four-sided duct aspect ratio (W/H) = 8, the Reynolds number occupied from 3000 to 12,000, fraction of pitch to roughness height, P/e in the range of 10–25; ratio of roughness height to hydraulic diameter, e/D in the range of 0.018–0.042; at flow attack angle, α = 60 deg for constant moral of relative roughness width, (W/w) = 6. The augmentation on thermal efficiency in three-sided rugged duct is found to be 23–86% when compared to smooth duct, and the maximum thermal efficiency can occur at P/e = 10 and e/D = 0.042. The enhancement in air temperature flowing under three-sided roughened duct is found to be 49.27% more than that of a smooth duct. The instant innovative form of three-sided roughened solar air warmer would be preferable to those of a smooth solar air heater with respect to heat assignment.

Description: This research details the design, fabrication, and partial testing of a concentrated solar receiver and an air-cooled heat exchanger. The solar receiver and heat exchanger have been fabricated for use in an experimental system that uses the supercritical carbon dioxide Brayton cycle. They are coupled with a Science Applications International Corporation (SAIC) solar dish 250× concentrator located on the University of Nevada, Las Vegas campus. The purpose of this solar-powered supercritical CO2 system is to function as a testbed for testing the cycle, system components, and alternate system configurations. Photographic flux mapping of the dish showed peak solar flux just above 200× and is used to appropriately size the receiver. Sun tests of the tubing, receiver, and air-cooled heat exchanger were performed achieving fluid temperatures in the range of 973 K (700 °C) using nitrogen in an open loop at low mass flowrates, and above 1173-K (900 °C) receiver wall temperatures in a no-flow case.

Description: Microgrids play a critical role in the transition from conventional centralized power systems to the smart distributed networks of the future. To achieve the greatest outputs from microgrids, a comprehensive multi-objective optimization plan is necessary. Among various conflicting planning objectives, emissions and cost are primary concerns in microgrid optimization. In this work, two novel procedures, i.e., non-dominated sorting genetic algorithm-II (NSGA-II) and multi-objective particle swarm optimization (MOPSO), were developed to minimize emissions and cost in combined heat- and power-based (CHP) industrial microgrids (IMGs) simultaneously, by applying the most practical constraints and considering the variable loads. Two different scenarios, the presence and absence of photovoltaics (PV) and PV storage systems, were analyzed. The results concluded that when considering PVs and PV storage systems, the NSGA-II algorithm provides the most optimized solution in minimizing economic and environmental objectives.

Description: In this paper, a new design of a solar still powered by a compound parabolic concentrator (CPC-SS) for agriculture irrigation is proposed and investigated. The concentrating performance of its concentrator is simulated which is proved that it has a wide focusing angle and the receiving rate is still more than 80% when the incident angle of light reaches to 35 deg. Theoretical calculations show that the daily water production rate per unit area of the solar still can reach 4 kg/m2, which can meet the crop growth needs of 2 m2. The water production performance and operating temperature of the CPC-SS were tested experimentally under actual weather conditions, and the variation curves of system internal working temperature and water production performance with time were given. As the results, in the sunny weather conditions in Beijing in the autumn, the daily water production of the tubular solar still is about 2.03 kg/m2, and the maximum operating temperature in the tube reaches 60 °C. The actual solar energy utilization efficiency can be as high as 22%.

Description: An algorithm and modeling are developed to make precise planning of year-round solar energy (SE) collection, storage, and redistribution to meet a decided demand of electrical power fully relying on solar energy. The model takes the past 10 years’ data of average and worst-case sky coverage (clouds fraction) condition of a location at a time interval (window) of per 6 min in every day to predict solar energy and electrical energy harvest. The electrical energy obtained from solar energy in sunny times must meet the instantaneous energy demand and also the need for energy storage for nighttime and overcast days, so that no single day will have a shortage of energy supply in the entire year and yearly cycles. The analysis can eventually determine a best starting date of operation, a least solar collection area, and a least energy storage capacity for cost-effectiveness of the system. The algorithm provides a fundamental tool for the design of a general renewable energy harvest and storage system for non-interrupted year-round power supply. As an example, the algorithm was applied for the authors’ local city, Tucson, Arizona of the U.S. for a steady power supply of 1 MW.

Description: The earlier aerodynamic models for studying vertical axis wind turbines (VAWT’s) are based on constant incident wind conditions and are thus capable of predicting only periodic variations in the loads. The purpose of the present study is to develop a mode capable of predicting the aerodynamic loads on the Darrieus rotor in a turbulent wind. This model is based on the double-multiple streamtube method (DMS) and incorporates a stochastic wind model The method used to simulate turbulent velocity fluctuations is based on the power spectral density. The problem consists in generating a region of turbulent flow with a relevant spectrum and spatial correlation. The first aerodynamic code developed is based on a one-dimensional turbulent wind model. However, since this model ignores the structure of the turbulence in the crossflow plane, an extension to three dimensions has been made. The computer code developed, CARDAAS, has been used to predict aerodynamic loads for the Sandia-17m rotor and compared to CARDAAV results and experimental data. Results have shown that the computed aerodynamic loads have been improved by including stochastic wind into the aerodynamic model.

Description: The present experimentation work discloses drying of hygroscopic crops under the new concept of solar-assisted greenhouse type dryer integrated with evacuated tube water heating system to control and maintain the temperature of the greenhouse environment according to the regulated flowrate of heated water in the drying trays. The dryer consists of an evacuated tube solar collector, flow regulating device and drying bed with provision for the flow of heated water. The power supply for forced circulation of solar-heated water inside the copper tube as well as the greenhouse environment air is maintained by solar photovoltaic (PV) modules. The dryer is tested for drying two hygroscopic crops namely coriander and fenugreek. The drying performance of the hybrid system is evaluated in terms of mass reduction and its derived influence on moisture content and drying rate. The derived parameters are compared with the corresponding evaluations under open sun drying. The rise in the greenhouse environment temperature and the crop surface temperature at hourly intervals as compared to the ambient condition were used as parameters for the thermal performance of the dryer. The drying curve for change in mass shows complete drying time for coriander and fenugreek reduced by 3.5 and 2.5 h, respectively, for present sample sizes. The most suitable mathematical model was also regressed using matlab followed by the development of a neural network for more precise prediction of moisture ratio (MR) for present hybrid drying.

Description: The high cost and poor performance of small wind turbines make them not widely used. In an attempt to meliorate this situation, the authors propose to investigate alternative airfoils with different chord and pitch angle distributions that permit low manufacturing, installation and maintenance costs, as well as high efficiency. To achieve these goals, two airfoil sections, Gottingen and Joukowski, together with different chord and pitch angle distributions were simulated by using a validated numerical code based on the blade element momentum (BEM) method. The chord geometry includes constant, linear, and elliptic distributions while the twist angle includes constant and linear distributions. The results reveal that the linear pitch distribution reduces the thrust in the intermediate region of the blade and the bending moment at the root and reduces the power coefficient for both rotors. Rotors with elliptic chord distribution show increased forces in the intermediate region. Joukowski based blades with elliptic chord distribution show lower thrust compared with those with linear chord distribution. The linear chord distribution increases the thrust in the intermediate region and reduces it at the tip and root regions. Blades with multiple airfoils show marginal improvement. The Gottingen and Joukowski based rotors have similar annual energy production (AEP). The Joukowski based rotor with linear pitch and linear chord distribution shows better performance at low velocities and easy to manufacture which makes it a good candidate for small power wind turbines.

Description: This manuscript has been presented to evaluate the annual performance of evacuated tube solar air collector (ETSAC) by using phase change material (PCM). The PCM (acetamide) simultaneously stores and exchange the heat to the air amid day hours. The heat stored by the PCM has been used to deliver hot air amid night hours. The performance of the system has been analyzed with a circular fin configuration along with reflectors at 0.035 kg/s air flowrate for 12 typical days. The performance of the system has been found excellent in the month of July. The maximum average temperature of PCM has been found to be as 87.8 °C and the maximum average collector efficiency as 31.4%.

Description: This work reports the design, numerical modeling, and optimization of a new solar water heater using a heat pipe parabolic trough collector (HPPTC) with low concentration ratio. The heat pipe evaporator is positioned on the focal axis of the reflector, while the condenser section is completely immersed in the water cylindrical tank. The copper wire mesh wick is used as the capillary structure, and the working fluid is distillated water. The proposed model operates in transitory regime under the weather conditions of Casablanca city in Morocco. The intensity of direct solar radiation was estimated by the Kasten model assuming a total sun tracking. The finite difference method has been used to solve governing equations. Several optimization types have been investigated and proved that the optimal configuration is obtained by correctly choosing the geometrical and physical parameters of the system. The thermal efficiency for this configuration with a single heat pipe is about 68.45%. This high performance show that the incorporation of a heat pipe as absorber in a PTC may be a better alternative than conventional heating systems.

Description: A combined thermal power and cooling cycle is proposed which combines the Rankine and absorption refrigeration cycles. It can provide power output as well as refrigeration with power generation as a primary goal. Ammonia-water mixture is used as a working fluid. The boiling temperature of the ammonia-water mixture increases as the boiling process proceeds until all liquid is vaporized, so that a better thermal match is obtained in the boiler. The proposed cycle takes advantage of the low boiling temperature of ammonia vapor so that it can be expanded to a low temperature while it is still in a vapor state or a high quality two phase state. This cycle is ideally suited for solar thermal power using low cost concentrating collectors, with the potential to reduce the capital cost of a solar thermal power plant. The cycle can also be used as a bottoming cycle for any thermal power plant. This paper presents a parametric analysis of the proposed cycle.

Description: It is known that the higher the evaporation temperature, the higher the coefficient of performance of a heat pump for hot water supply. Flat-plate solar collectors which were insulated on the back and bonded with flexible polycrystalline silicon-type photovoltaic modules on the upper surfaces were used in a heat pump system as the evaporator in order to increase the coefficient of performance and to generate electric power. The total area of the collectors was 3.24 m2 and the photovoltaic modules covered 76 percent of the area. The characteristics of the photovoltaic array and the thermal performance of the heat pump were studied experimentally. The results indicated that a coefficient of performance (COP) of the heat pump as high as six could be obtained at 40°C of the water temperature at the inlet of the condenser in the daytime in winter. The peak electric power generated was 120 W. It was found that the photovoltaic modules on the collectors did not influence the performance of the heat pump appreciably. When there was little solar radiation, the COP of the heat pump became two which was very low. This defect was improved by using an evaporator, which had a high convective heat transfer coefficient, arranged in parallel with the fiat-plate collectors.

Description: Garrad Hassan have a project in progress funded by the U.K. Department of Trade & Industry (DTI) to assess the prospects and Cost benefits of advanced wind turbine design. In the course of this work, a new concept, the coned rotor design, has been developed. This enables a wind turbine system to operate in effect with variable rotor diameter augmenting energy capture in light winds and shedding loads in storm conditions. Comparisons with conventional design suggest that a major benefit in reduced cost of wind-generated electricity may be possible.

Description: We have achieved a 50,000 ± 3,000 times concentration of sunlight using a unique dielectric nonimaging concentrator in an experiment performed at the National Renewable Energy Laboratory. The scale of the experiment is several times larger than that of previous experiments. Total output power approaching 1 kW passes through a 4.6 mm diameter aperture. An extractor tip is added to the concentrator profile which allows measurement of flux levels using an air calorimeter. This new device has the potential to allow the use of dielectric concentrators at larger scale for thermal electric power generation. We report on the implications of this experiment for the future use of dielectric concentrators.

Description: The reradiation losses, inherent to every thermal receiver, can be significantly reduced by exposing the working fluid to monotonously increasing irradiance and preventing energy exchange between parts of the receiver that are at different temperatures. In this way the highest temperatures are reached only near the end of the working fluid’s path. The improvement is much more pronounced for nonuniform as compared to uniform irradiance. For a Gaussian distribution of irradiance we calculate improvements exceeding a factor of two for the efficiency at a given temperature (0.8 of the peak stagnation temperature), and for the temperature at a given efficiency of 0.8. These results are independent of the peak irradiance and of the width of the distribution. Even a coarse partitioning into two mutually isothermal parts can already produce a significant improvement over the totally isothermal receiver.

Description: Wind-generated electricity can be fundamentally transformed from an intermittent resource to a baseload power supply. For the case of long distance transmission of wind electricity, this change can be achieved at a negligible increase or even a decrease in per unit cost of electricity. The economic and technical feasibility of this process can be illustrated by studying the example of a wind farm located in central Kansas and a 2000 km, 2000 megawatt transmission line to southern California. Such a system can have capacity factor of 60 percent, with no economic penalty and without storage. With compressed air energy storage (CAES) (and with a negligible economic penalty), capacity factors of 70–95 percent can be achieved. This strategy has important implications for the development of wind energy throughout the world since good wind resources are usually located far from major demand centers.

Description: This paper describes the thermodynamic optimization of a class of refrigerators without work input, which are driven by heat transfer from a solar collector. The model consists of a finite-size solar collector with heat loss to the ambient, and a refrigerator with three finite-size heat exchangers, namely, the evaporator between refrigeration load and refrigerant, the condenser between the refrigerant and the ambient, and the heat exchanger between the solar collector and the refrigerant. The total thermal conductance of the three heat exchangers is fixed. The solar collector heat loss to the ambient is proportional to the collector-ambient temperature difference. The first part of the paper reports the operating conditions for maximum refrigeration effect, specifically, the optimal collector temperature, and the optimal way of allocating the thermal conductance inventory to the three heat exchangers. For example, the optimal condenser conductance is equal to half of the total thermal conductance, and is independent of other operating parameters. The second part of the paper examines the changes in the optimal design when the price of the refrigeration load (pL) is different (higher) than the price of the heat input provided by the collector (pH). The optimal collector temperature and the optimal three-way allocation of the thermal conductance inventory are reported as functions of the price ratio pH/pL.

Description: Space-based inflatable technology is of current interest to NASA and DOD, and in particular to the Air Force and Phillips Laboratory. Potentially large gains in lowering launch costs, through reductions in structure mass and volume, are driving this activity. Diverse groups are researching and developing this technology for radio and radar antennae, optical telescopes, and solar power and propulsion applications. Regardless of the use, one common requirement for successful application is the accuracy of the inflated surface shape. The work reported here concerns the shape control of an inflated thin circular disk through use of a nonlinear finite element analysis. First, a review of the important associated Hencky problem is given. Then we discuss a shape modification, achieved through enforced boundary displacements, which resulted in moving the inflated shape towards a desired parabolic profile. Minimization of the figure error is discussed and conclusions are drawn.

Description: The TRNSYS simulation program is a sequential-modular transient simulation program which is widely used for both solar and nonsolar simulation studies despite its near 20-year-old origins. There have been many revisions to TRNSYS between its original release and the current version 13.1 but they have maintained the same sequential computational scheme for solving simultaneous algebraic and differential equations. TRNSYS 14 has recently been developed which implements a more robust method for solving simultaneous sets of nonlinear equations. The new computational scheme utilizes equation blocking to improve convergence properties and it handles discrete control decisions in a manner which promotes convergence in the iterative calculations. The new computational scheme allows TRNSYS 14 to solve problems which were either difficult or impossible to solve in previous versions as well as backwards problems, for which the output of a component is specified and the input must be determined. The computation scheme incorporated into TRNSYS 14 is described in this paper and its capabilities are illustrated with several examples.

Description: This article presents a study of modeling and optimization for the dynamic performance of wind turbine composite material blades and investigates the effects of composite material stacking sequence in addition to some design parameters such as twist angle (ɸ) and aspect ratio (AR) on the whole wind turbine performance. The two-stage Savonius rotor VAWT composite blades are designed and simulated within the solidworks simulation 2020 package. Modified mechanical parameters are introduced to improve the scalability, reliability, and accuracy of the developed models. The lamination plate theory is used to compute the equivalent mechanical properties for each composite blade. The finite element analyses (FEAs) are conducted to investigate the dynamic characteristics (frequency and associated mode shapes) of wind turbine models. Taguchi tools such as analysis of variance (ANOVA), signal-to-noise (S/N) ratio and additive model were employed to evaluate and obtain the significant factors and determine the optimal combination levels of wind turbine design parameters. Mathematical modeling based on response surface methodology (RSM) has been established. The analysis of results shows that the aspect ratio with a contribution of 48.08% had the dominant impact on the rotor performance followed by the stacking sequence and twist angle.

Description: The objective of this paper is the investigation of the annual performance of a solar power plant with linear Fresnel reflectors in the El-Oued region at Algeria. The solar collectors produce water steam that feeds a turbine to produce electricity. The System Advisor Model (sam) tool is used for simulation. The mean net daily electricity production rate from 8:30 am to 5:30 pm is 48 MWe, and the respective annual production is 210,336 MWh/year. The mean daily optical efficiency of the solar field was close to 52%, while the mean thermal efficiency was about 39%. The net daily cycle efficiency is found to be 24%. The net capital cost of the examined system is $393 million, and the developer net present value is $47 million; the investor net present value is $15 million, the entire period of capital recovery is 11 years, and the levelized cost of electricity is 0.0382 $/kWh. The solar power plant leads to the yearly avoidance of 420,672 tons carbon dioxide emissions (operational cost savings of $6.1 million). Based on the obtained results, linear Fresnel reflectors can be used to achieve satisfying, energetic, financial, and environmental performance that can lead to sustainability.

Description: Devices and methods are presented in which an optical fiber reflectometer and a solar concentrator are used to determine solar reflectivity and absorptivity for opaque and diffuse materials. The measurements can be taken at high temperature, the final aim is to reach 2500°C. Firstly we will present the specific reflectometer and its measurement principles. We will then describe the whole experimental hardware (solar concentrator, associated devices) and the method used to determine solar reflectivity and absorptivity. Finally, we will present examples of results obtained on a metallic sample.

Description: One of the problems of designing a solar compound parabolic concentrator (CPC) is related to its manufacturing shape accuracy. The complexity of curving and holding the CPC profile in place is indeed a challenging issue, especially because there are no standardized molds and the process is typically handmade. It is very easy to provoke misalignment on the CPC surface and in consequence, divert the solar incident rays, affecting significantly the optical efficiency of the system. This work presents a novel, inexpensive methodology to manufacture a CPC with accuracy by using basic tools. The design starts with the acquisition of a pair of medium-density fiberboard wooden templates of the CPC profile that are used later to make a Styrofoam CPC mold and then cut with a hot-wire technique. A high-reflectance anodized aluminum sheet is curved to approximate the CPC shape and is then coupled with the temporary Styrofoam mold. The last part consists of the elaboration of a housing system to contain the parts. This is consolidated by a polyurethane resin that expands and fills all enclosure cavities, offering stiffness and stability. A photogrammetry analysis was implemented for the validation of the surface shape accuracy. The results from the optical analysis show that this technique achieved a high degree of accuracy and homogeneity on the CPC surface shape.

Description: A magnetohydrodynamic (MHD) generator is a device that generates electrical energy through the interaction between a conductive fluid and a magnetic field. This method of direct energy conversion allows the use of a renewable energy source such as solar energy and represents an alternative to tackle the greenhouse effect. This paper presents the development of an MHD solar generator, which is constituted by a solar thermal system and an MHD cell. The solar thermal system consists of a set of tubes with copper fins, connected in parallel and placed inside of a 1 m2 panel. In which, an electrolytic mixture of H2O and NaCl at 20% vol. was introduced as a working fluid. In order to increase the kinetic energy of the fluid, the panel was exposed to solar radiation, where it reached temperatures above 373 K and pressures above 96 kPa. This solar thermal system operates in closed cycle conditions by including a check valve in its inlet–outlet junction; in this way, the fluid travels through the MHD generator. The MHD cell was composed of a block of polytetrafluoroethylene, two cylindrical stainless-steel electrodes, and four neodymium magnets. For simulation purposes, comsol multiphysics was used to reproduce the current density produced by the MHD solar generator. Pressure and temperature quantities obtained experimentally in the MHD cell were employed as boundary conditions. The experimental maximal current density obtained corresponds to 4.30 mA/m2, and the comparison between theoretical and experimental results shows that the model fits fairly well.

Description: In a continuing effort to enhance the performance of small wind energy systems, one root airfoil and three primary airfoils were specifically designed for small horizontal axis wind turbines. These airfoils are intended primarily for 1–5 kW variable-speed wind turbines for both conventional (tapered/twisted) or pultruded blades. The four airfoils were wind-tunnel tested at Reynolds numbers between 100,000 and 500,000. Tests with simulated leading-edge roughness were also conducted. The results indicate that small variable-speed wind turbines should benefit from the use of the new airfoils which provide enhanced lift-to-drag ratio performance as compared with previously existing airfoils.

Description: Desiccant cooling systems have the ability to provide efficient humidity and temperature control while reducing the electrical energy requirement for air conditioning as compared to a conventional system. Naturally, the desiccant air dehumidification process greatly influences the overall performance of the desiccant system. Therefore, the effects of variables such as air and desiccant flow rates, air temperature and humidity, desiccant temperature and concentration, and the area available for heat and mass transfer are of great interest. Due to the complexity of the dehumidification process, theoretical modeling relies heavily upon experimental studies. However, a limited number of experimental studies are reported in the literature. This paper presents results from a detailed experimental investigation of the heat and mass transfer between a liquid desiccant (triethylene glycol) and air in a packed bed absorption tower using high liquid flow rates. A high performance packing that combines good heat and mass transfer characteristics with low pressure drop is used. The rate of dehumidification, as well as the effectiveness of the dehumidification process are assessed based on the variables listed above. Good agreement is shown to exist between the experimental findings and predictions from finite difference modeling. In addition, a comparison between the findings in the present study and findings previously reported in the literature is made. The results obtained from this study make it possible to characterize the important variables which impact the system design.

Description: The modeling of photovoltaic (PV) systems is substantial for the estimation of energy production and efficiency analysis in the PV systems under the changing environmental conditions. A PV model mathematically expresses the electrical characteristic of the PV modules according to temperature and irradiance. The most popular electrical circuit models are the single-diode model (SDM) and the double-diode model (DDM). Considering accuracy and complexity, SDM was used in this paper. In the equivalent circuit model used to estimate the electrical behavior of the PV modules, the parameter estimating has become an optimization problem. In recent studies, it is seen that metaheuristic algorithms are often employed in solving this optimization problem. In this paper, a new six-parameter PV model is proposed to improve the accuracy of the five-parameter SDM, taking into account the temperature dependence of the series resistance. Particle swarm optimization (PSO) and a couple of metaheuristic algorithms have been executed to estimate six unknown parameters of the proposed model under standard test conditions (STC: 25 °C, 1000 W/m2, AM1.5) using current–voltage (I–V) data of PV module. In order to evaluate the performance of the proposed method under the changing environmental conditions, it was compared with the three methods commonly used in the literature. Accuracy of the proposed model has been indicated by the root mean square error (RMSE) within the range of current data and the model current values. Simulation results demonstrate that the proposed model can predict the I–V curve for the PV modules with high accuracy.

Description: Various properties of the paraffin have made them compatible to be incorporated in the building materials for improving the latent heat storage capacity of the building envelope. However, the poor thermal conductivity of the paraffin reduces their thermal performance and hence limits their direct application/incorporation in the buildings. In this study, composite mixtures of paraffin and expanded perlite (EP) with an equal weight percent of 49.5 and 47.5, loaded with 1% and 5% of graphene nano-platelets, respectively, were synthesized. The developed samples were characterized uncycled and after 2000 thermal cycles. The results indicate that phase change material (PCM)/expanded perlite/graphene nano-platelets composite shows a significant increment in the thermal conductivity, reduction in the latent heat storage capacity, and a small weight loss. The heat storage/release test depicts that the phase change material/expanded perlite/graphene nano-platelets-5 shows 1.66 and 2.5 times faster heat storage/release rate than phase change material/expanded perlite/graphene nano-platelets-1 and paraffin, respectively. There is no significant change noted after 2000 thermal cycles in phase change material/expanded perlite/graphene nano-platelets-5 and phase change material/expanded perlite/graphene nano-platelets-1 samples, suggesting long-term reliability of the composite PCM. Additionally, thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR) testing were also conducted and the results suggest high thermal reliability and good chemical compatibility. These analyses suggest that the phase change material/expanded perlite/graphene nano-platelets composite can become a potential candidate for thermal energy storage.

Description: Sustainable power generation on solar photovoltaic (SPV) modules integrated lighter-than-air platforms (LTAPs) is a daunting task since they are exposed to variable environmental factors such as wind, ambient air pressure, and incident solar insolation. Among these factors, the wind plays a significant role in destabilizing the system from its equilibrium position and affects the power generation. In this paper, we proposed a methodology for estimating the dynamics of power generation due to the destabilized pitching under different wind vectors. An alternative to the conventional fluid–structure interaction, a semi-analytical methodology has been formulated, utilizing commercial ansys fluent software, to estimate the pitching characteristics of lighter-than-air platform (LTAP). This pitching characteristic has been mapped to the body inertial frame for investigating the incident solar insolation followed by determining the corresponding power generation. The consequences of the envelope contour function (ECF) are also incorporated while characterizing the power generation. Furthermore, this study also provides scope for the placement of the solar PV array on LTAP in order to minimize losses in generated onboard power under variable pitching conditions.

Description: In a previous paper, the results of photogrammetric measurements of a number of paraboloidal reflecting surfaces were presented. These results showed that photogrammetry can provide three-dimensional surface characterisations of such solar concentrators. The present paper describes the assessment of the quality of these surfaces as a derivation of the photogrammetrically produced surface coordinates. Statistical analysis of the z-coordinate distribution of errors indicates that these generally conform to a univariate Gaussian distribution, while the numerical assessment of the surface normal vectors on these surfaces indicates that the surface normal deviations appear to follow an approximately bivariate Gaussian distribution. Ray tracing of the measured surfaces to predict the expected flux distribution at the focal point of the 400 m2 dish show a close correlation with the videographically measured flux distribution at the focal point of the dish.

Description: This study presents the geometrical optimization of a solar air heater. A reasonable working range of geometrical parameters: length 1–3 m, width 0.1–0.5 m, and height 0.005–0.05 m (or aspect ratio 1–20), is investigated as per general applications and installation constraints. The effect of these geometrical parameters on thermal (heat flux and outlet air temperature) and hydraulic (air velocity, mass flowrate, pressure loss and pumping power, and Bejan number) parameters are theoretically studied. Later, a numerical investigation is carried out with an optimum geometry of SAH-duct (length 2.44 mm and width 0.3 m), for aspect ratio 4–18 and Re 3000–15,000. An experimental study is also done to validate numerical results. The heat transfer and frictional loss do not show a significant change in the values for the aspect ratio 8–12.

Description: The present study demonstrated the antibacterial effect of photocatalytic oxidation in indoor air using titanium dioxide as the catalyst. Through a series of experiments, it was determined that titanium dioxide did enhance the inactivation rate of the microorganisms under certain conditions. In these experiments the air velocity, relative humidity, and UV (350 nm) intensity were varied. It was found that higher velocities retarded the destruction rate due to the low retention time in the reactor. TiO2 also did not accelerate the reaction at low humidities (30 percent). At a relative humidity of 50 percent, there was complete inactivation of the organisms, but at higher humidities (85 percent), 10 percent of the organisms were still viable. The experiments showed that at higher UV intensities, most of the inactivation was done by the UV photons. However, the photons were not able to completely inactivate the microorganisms. In the photocatalysis experiments there was complete inactivation of the bacteria.

Description: An experimental investigation was carried out to determine the heat transfer coefficient from a rectangular tilted cavity to the ambient due to the buoyancy driven flow in the cavity. The cavity is partially or fully open from one side. All the walls of the cavity are adiabatic except the wall facing the cavity opening which is heated at a constant heat flux. Air was used as the cavity fluid and the experiments were carried out at a flux Grashof number of 5.5 × 108. The tilt angle of the cavity, measured from the vertical direction, was changed between −90 deg to +90 deg in 15 deg increments. Also, geometries of aspect ratio (height-to-width of cavity) of 1.0, 0.5, and 0.25 and of opening ratio (opening height to cavity height) of 1.0, 0.5, and 0.25 were considered in the study. The results are presented in terms of the average Nusselt number for different values of the above experimental parameters. Conclusions are derived for the effect of changing the tilt angle, the aspect ratio, or the opening ratio of the cavity on the average heat transfer coefficient between the cavity and the ambient air.

Description: This paper reviews the design and implementation of hardware and software tools for nonintrusive electrical load monitoring. Estimates of spectral content in measured waveforms can be used to determine in real time the operating schedule of loads at a target site. Techniques for transient event detection are reviewed. These techniques can detect the turn-on and turn-off transients of individual loads, and can be used to easily determine the energy usage of loads that draw constant power in steady-state operation. Techniques for monitoring the power consumption of smoothly varying loads (e.g., variable speed drives) using spectral estimates are also discussed.

Description: Advancement of human civilization has led to rapid industrialization going in hand with urbanization and globalization, which have elevated energy demand worldwide. Conventional energy sources with the fear of being exhausted at a rapid pace seem to fail to quench inflated energy demand alone. Solar being a ubiquitous and eco-friendly source of renewable energy has become one of the most dominant forms of power generation implemented in diverse applications. To maximize the efficacy of the solar photovoltaic (SPV) system, it must be operated at maximum power point (MPP) that incorporates the use of maximum power point tracking (MPPT) algorithm. MPPT algorithm is a self-automated control technique that compels the SPV system to operate at MPP thereby harnessing maximum obtainable power under time-varying environmental conditions such as solar intensity, temperature, SPV module characteristics, and module shading. This paper puts forward an elaborated study on 27 MPPT techniques that are pervasive in the SPV system. The entire assessment deals with MPPT techniques employed under uniform solar insolation varying from time to time as well as global maximum power point tracking (GMMPT) techniques employed under partial shading (PS) conditions. Vivid comparisons among all the MPPT techniques along with their brief discussion, merits, and demerits have been done. Moreover, a detailed structure of error-based incremental conductance MPPT has been proposed.

Description: Concentrating solar power (CSP) technology is one of the promising options to generate green energy. However, the cost of kWhe produced is relatively high compared with fossil resources and can be reduced by integrating a cogeneration system exploiting waste energy. In this study, a technico-economic evaluation of a 1 MWe CSP plant with a condensation heat (85 °C) is investigated. The temperature constraint is set to meet the thermal separation needs of the draw solution of a forward osmosis desalination process. The purpose of this study focuses on the factors involved in reducing the cost per kWhe, which are the selection of the organic fluid used in the organic Rankine cycle and the appropriate choice of the solar multiple (SM) according to the appropriate storage hours (SH) maximizing the CSP thermal efficiency. The performance of different organic fluids was compared, based on the calculation of the thermodynamic cycle efficiency. The cyclopentane was retained for its reduced cost. Operating with this fluid, a sensitivity analysis was realized to test the effect of the solar multiple and storage hours on the power plant. It allows us to conclude that different appropriate combination between storage hours and solar multiple can be chosen, for the needs of our project, we opt for 8 h and 1.85, respectively. Thus, in this case, the cost of kWh was found to be 23.95¢.

Description: Our experiments show that active carbon fiber (ACF) might be a good substitute for activated carbon (AC) as the refrigeration capacity Qf and adsorption time of ACF are three times more and 1/5 ∼ 1/10 of those of normal activated carbon (AC), respectively. The COP for ACF-methanol could be 10 percent ∼ 20 percent higher than that of AC-methanol. Thus ACF-methanol might be a good adsorption refrigeration pair for constructing adsorption refrigerators, especially those for household applications.

Description: The distribution of surface normal deviations from an ideal shape on concentrating solar surfaces is used to define the optical quality of a reflector. These distributions can be modeled by considering them to ideally follow a two-dimensional, circular Gaussian distribution. However, the measurement of these deviations in experimental systems usually defines only that component of the surface normal that deviates from the ideal surface normal direction, and ignores the rotational component of the normal vector in the plane perpendicular to the ideal direction. To compare the measured one-dimensional radial distribution with the expected two-dimensional model, we must transform the two-dimensional model into the appropriate radial distribution. The following analysis describes this transformation, and presents results gained from an application of the analysis to measured surface normal data from a mirror panel used in the reflecting surface of the 400 m2 paraboloidal (“Big Dish”) concentrator constructed at the ANU.

Description: At the DLR a second generation sodium heat pipe receiver for the Schlaich Bergermann und Partner (SBP) 9-kWe dish/Stirling system has been developed and constructed. Long-term operation occurred from Oct. 1992 until Aug. 1993 at the Plataforma Solar de Almeria (PSA) in Spain, accumulating 950 operating hours. The performance of the SBP 9-kWe system with a sodium heat pipe receiver is evaluated according to the guidelines for dish/Stirling performance evaluation by Stine and Powel, as proposed to the International Energy Agency (IEA). Tests were stopped due to a leak in the receiver absorber surface. The analysis of this damage are reported.

Description: This paper presents a two-dimensional (2D) transient numerical model for simulating the vapor deposition process for growing perovskite films. The diffusion process of methylammonium iodide (MAI) vapor through the processing chamber to react with the lead iodide (PbI2) substrate and grow the perovskite layer is analyzed with a diffusion coefficient that has been determined by measuring thicknesses of perovskite layers grown in a chemical vapor deposition (CVD) chamber. Innovations applied to the CVD chamber to improve the uniformity of layer thickness and offer control over the growth process are applied and computationally assessed. One is the addition of screens at various strategic locations in the chamber to improve flow uniformity. Another is changing the locations of MAI sublimation bowls and chamber outlet numbers and locations. The results show that adding screens makes the MAI vapor flow more uniform in the plenum while allowing a quicker purge of the N2 inert gas. This leads to a higher and more uniform growth rate of perovskite. The MAI vapor flow is influenced by the reaction plenum geometry, so the chamber is expected to allow good control of the process to achieve uniform surface deposition rate and controlled grain growth of the perovskite layer.

Description: The effects of rime ice on horizontal axis wind turbine performance were estimated. For typical supercooled fog conditions found in cold northern regions, four rime ice accretions on the S809 wind turbine airfoil were predicted using the NASA LEWICE code. The resulting airfoil/ice profile combinations were wind tunnel tested to obtain the lift, drag, and pitching moment characteristics over the Reynolds number range 1−2 × 106. These data were used in the PROPID wind turbine performance prediction code to predict the effects of rime ice on a 450-kW rated-power, 28.7-m diameter turbine operated under both stall-regulated and variable-speed/variable-pitch modes. Performance losses on the order of 20 percent were observed for the variable-speed/ variable-pitch rotor. For the stall-regulated rotor, however, a relatively small rime ice profile yielded significantly larger performance losses. For a larger 0.08c-long rime ice protrusion, however, the rated peak power was exceeded by 16 percent because at high angles the rime ice shape acted like a leading edge flap, thereby increasing the airfoil Cl,max and delaying stall.

Description: A high-flux solar simulator is essential for evaluating solar thermal components under controlled and adjustable flux input conditions. This study presents a newly built high-flux solar simulator composed of 19 individual units. Each unit includes a xenon short-arc lamp (each consuming up to 6 kW electricity power) coupled with a truncated ellipsoidal reflector, a cooling blower, and a power module. The power module yields a current in the range of 50–160 A. The number of lamps in use is flexible, which allows for a wide range of radiation flux (10%–100%) on the focal plane. The radiation power, peak value, flux distribution on the circular target plane, and conversion efficiency are evaluated based on a flux mapping method. The results indicate that the proposed solar simulator is capable of achieving thermal power of 23.3 kW, peak flux in excess of 1.78 MW/m2, a stagnation temperature exceeding 2360 °C, and average irradiance of 773.4 kW/m2 on the focal plane (diameter of 260 mm). The electro-thermal conversion efficiency of the simulator is 35.7%. A ray-tracing method was employed, and the simulation results were found to be in good agreement with those in the experiments. An experimental test of a volumetric ceramic receiver was conducted, and the results indicate the availability and applicability of the high-flux solar simulator when carrying out studies about solar receivers.

Description: This article compares the dynamic behavior of solar-assisted novel salt-based ammonia/sodium thiocyanate (NH3 + NaSCN) and ammonia/lithium nitrate (NH3 + LiNO3) single-effect absorption refrigeration cycles. An evacuated tube collector (ETC) is attached with fully mixed hot water storage tank to power the absorption system. Variations in ambient conditions are determined for Gujarat Region of India and their effects on absorption cycles are quantified throughout the days for the months of April to September. System performance is investigated and compared on terms of coefficient of performance (COP), refrigeration capacity, efficiency and solar COP (SCOP). At same operating conditions, it is found that the NH3 + LiNO3 cycle can achieve much lower evaporator temperature (−13.1 °C) then NH3 + NaSCN cycle (−7.5 °C) and maximum possible COP for NH3 + NaSCN cycle is 0.73 and 0.68 for NH3 + LiNO3 cycle. The working limit of NH3 + LiNO3 cycle is wide ranging and narrow for NH3 + NaSCN cycle due to high crystallization possibility. SCOP varies from 0.18 to 0.43 for NH3 + NaSCN cycle and 0.17 to 0.39 for NH3 + LiNO3 cycle over the period of 6 months. Based on these findings, the suitable working cycle is justified.

Description: The motion response of a (NREL) 5 MW wind turbine with tip-fusion winglets in the marine environment were studied in this paper. The aerodynamic performance of the wind turbine in three motion modes of yaw, surge, and pitch is simulated by the fluent software. The variation trend of power and axial thrust of the wind turbine with winglets under the motion conditions is explored, and its flow field is analyzed. The results indicate that the wind turbine with fusion winglets has the better aerodynamic performance. Besides, the effect of the winglet on the aerodynamic performance is mainly concentrated at the tip of the blade, especially at the relative height of 0.9 or above. The research results provide theoretical and technical reference for improving aerodynamic performance of the floating offshore wind turbine by adding tip-fusion winglets under the complex sea states.

Description: This paper describes the development and performance assessment of a tower solar collector driven integrated system operating in trigeneration mode to generate electricity, heating, and cooling, in a carbon-free manner. The proposed system applies a heliostat-based central receiver unit as a base of solar energy input to drive the steam Rankine cycle which is combined with the process heater and the lithium bromide-water operated absorption chiller. An analysis is performed to monitor the behavior of energy and exergy efficiency at various operating conditions of the proposed trigeneration system. The computed results are authenticated with the reported literature. A comparison is made between the present findings and reported results in the form of exergy efficiency, total exergy destroyed, and energy efficiency. Consideration of process heat and cold along with electricity provides a promising increase in energy efficiency from 15.8% to 64.1% while the exergy efficiency is enhanced from 16.9% to 24.4%. Variation in direct normal irradiations from 600 W/m2 to 1000 W/m2 results in the significant rise of energetic and exergetic outcomes of the proposed trigeneration system. Out of 100% solar exergy supplied to the proposed trigeneration, 24% is generated as the exergetic output, 1.6% is lost to ambient, and the remaining 74.4% is the exergy destroyed in the system components.

Description: This paper presents a model prediction to capture specifically how energy usage in sustainable buildings on college campuses is affected by different variables of student life. The California State University, Fullerton (CSUF) Student Housing Phase III, which received a Platinum Leadership in Energy and Environmental Design (LEED) certification for the Building Design and Construction category, with its performance in a LEED California Nonresidential Title 24 (NRT24) and ASHRAE 90.1 climate zones, is used as a case study to illustrate the method. Through LEED-approved software, the standard compliant energy models are compared with the occupancy-scheduled models along with the actual energy consumption in different climate zones. The results provide insight into how variables within student dormitory life affect the total building energy usage. The total amount of energy consumed per area is one new factor providing understanding into occupancy trends. This new data set reveals more understanding regarding how and where the energy is consumed to maintain a comfortable learning environment. The LEED certification program is one benchmark used to determine sustainable building design. Designers must adhere to set standards before being awarded a U.S. Green Building Council (USGBC) certification such as LEED. The results from this paper will provide input over which variables within student dormitory life affect the energy usage of the building. With the model results, some solutions are presented to update the LEED project certification as well as to reduce student energy usage.

Description: The total monthly average of daily radiation on a horizontal surface at the site of Oran (35.38 deg N, 0.37 deg W) is achieved by applying two models. We present a comparison between the first one which is a regression equation of the Angstrom type and the second model, developed by the present authors: Some modifications were recommended using relative humidity as the input meteorological parameter) and longitude, latitude, and altitude as the astronomical parameters. The process of examining similarities is made using root mean square error (RMSE), the mean bias error (MBE), mean absolute error (MAE), and mean absolute percentage error (MAPE). This comparison shows that the second model is closer to the experimental values of the Angstrom model.

Description: A new high-flux solar furnace, capable of delivering up to 40kW at peak concentration ratios exceeding 5000, is operational at PSI. Its optical design characteristics, main engineering features, and operating performance are described. This solar concentrating facility will be used principally for investigating the thermochemical processing of solar fuels at temperatures as high as 2500 K.

Description: Cyclic loadings produce progressive damage that can ultimately result in wind turbine structural failure. There are many issues that must be dealt with in turning load measurements into estimates of component fatigue life. This paper deals with how the measured loads can be analyzed and processed to meet the needs of both fatigue life calculations and reliability estimates. It is recommended that moments of the distribution of rainflow-range load amplitudes be calculated and used to characterize the fatigue loading. These moments reflect successively more detailed physical characteristics of the loading (mean, spread, tail behavior). Moments can be calculated from data samples and functional forms can be fitted to wind conditions, such as wind speed and turbulence intensity, with standard regression techniques. Distributions of load amplitudes that accurately reflect the damaging potential of the loadings can be estimated from the moments at any wind condition of interest. Fatigue life can then be calculated from the estimated load distributions, and the overall, long-term, or design spectrum can be generated for any particular wind-speed distribution. Characterizing the uncertainty in the distribution of cyclic loads is facilitated by using a small set of descriptive statistics for which uncertainties can be estimated. The effects of loading parameter uncertainty can then be transferred to the fatigue life estimate and compared with other uncertainties, such as material durability.

Description: Accurate modeling of hourly heating and cooling energy use in commercial buildings can be achieved by a Generalized Fourier Series (GFS) approach involving weather variables such as dry-bulb temperature, specific humidity and horizontal solar flux. However, there are situations when only temperature data is available. The objective of this paper is to (i) describe development of a variant of the GFS approach which allows modeling both heating and cooling hourly energy use in commercial buildings with outdoor temperature as the only weather variable and (ii) illustrate its application with monitored hourly data from several buildings in Texas. It is found that the new Temperature based Fourier Series (TFS) approach (i) provides better approximation to heating energy use than the existing GFS approach, ((ii) can indirectly account for humidity and solar effects in the cooling energy use, (iii) offers physical insight into the operating pattern of a building HVAC system and (iv) can be used for diagnostic purposes.

Description: This paper analyzes the irreversibilities due to the heat transfer processes in a latent heat thermal storage system. The Thermal Storage Module (TSM) consists of a cylindrical shell that surrounds an internal coaxial tube. The shell side is filled by a Phase Change Material (PCM); a fluid flows through the inner tube and exchanges heat along the way. The most fundamental assumption underlying this study is that the exergy of the hot fluid stream in the active phase is discharged into the environment and completely destroyed, unless it is partially intercepted by the storage system. A numerical study is conducted to identify and to minimize the thermodynamic losses of the storage and removal processes. The dependence of the second-law efficiency of the system on various design parameters is investigated and discussed.

Description: In stationary heat-loss experiments, the thermal losses by gas conduction of an evacuated flat-plate solar collector (EFPC) were experimentally determined for different values of interior gas pressure. The experiments were carried out with air and argon in the pressure range from 10−3 to 104 Pa. For air, loss reduction sets in at 100 Pa, whereas at 0.1 Pa heat conduction is almost completely suppressed. Using argon as filling gas, gas conduction is reduced by 30 percent (compared to air) at moderate interior pressures of 1000 Pa. With decreasing pressure this reduction is even greater (50 percent reduction at 10 Pa). A theory was developed to calculate thermal losses by gas conduction in an EFPC: Fourier’s stationary heat conduction equation was solved numerically (method of finite differences) for the special geometry of the collector. From kinetic gas theory a formula for the pressure dependency of the thermal conductivity was derived covering the entire pressure range. The theory has been validated experimentally for the gases air and argon. Calculations for krypton and xenon show a possible gas conduction loss reduction of 60–70 percent and 75–85 percent (with respect to air, depending on gas pressure), corresponding to a reduction of the overall collector losses of up to 40 percent.

Description: A procedure was developed for systematically testing whole building energy simulation models and diagnosing the sources of predictive disagreement. Field trials of the method were conducted with a number of detailed state-of-the-art programs by researchers from nations participating in International Energy Agency (IEA) Task 12 and Annex 21. The technique consists of a series of carefully specified test case buildings that progress systematically from extremely simple to relatively realistic. Output values for the cases, such as annual loads, annual maximum and minimum temperatures, peak loads, and some hourly data are compared, and used in conjunction with diagnostic logic to determine the algorithms responsible for prediction differences. The more realistic cases, while geometrically simple, test the ability of the programs to model such combined effects as thermal mass, direct solar gain windows, window shading devices, internally generated heat, infiltration, sunspaces, earth coupling, and deadband and setback thermostat control. The more simplified cases facilitate diagnosis by allowing excitation of particular heat transfer mechanisms. The procedure was very effective at revealing bugs, faulty algorithms, and input errors in a group of building energy simulation programs that may be considered among the world’s best. The output data from the simulation programs can be used as reference ranges for comparing and diagnosing other detailed or simplified design tools.

Description: A solar dynamic ground test demonstrator space power system is being developed. The system comprises a complete Brayton engine—a heat receiver, concentrator, radiator, recuperator, heat rejection gas cooler, and turboalternator compressor. All of these components will be operated inside a vacuum tank. The engine is powered by simulated sunlight from an external bank of lights. Successful completion of the testing will indicate the readiness of solar dynamic power for space applications. This paper discusses the thermal and structural analysis of the heat receiver component. The analysis performed indicates that all components comfortably meet the life and cold start requirements, while maintaining the necessary overall performance.

Description: A noncalorimetric method for measuring the heat-transfer coefficient (UA) of building thermal envelopes is proposed and applied in an indoor test cell. The UA value measured by this method agrees closely with that measured by a calorimetric method. This method creates a Single input and a Single output data Pair (SSP) from the measured data sets by using digital filters. The filter output and physical criteria are used to determine the correct transfer function, which yields the measured UA value. This method seems to have the following advantages over calorimetric methods: it uses shorter measurement times, uses simpler test equipment, and has minimum thermal intrusion on normal operating conditions.

Description: The absorbing matrix of a volumetric (directly irradiated) solar receiver must be exposed to the concentrated incoming sunlight. Most applications require that the receiver operates at an elevated pressure and in many cases the working fluid is not air. These requirements can be met only if the receiver is equipped with a transparent window. A novel frustum-like high-pressure (FLHiP) window, made of fused silica, is presented. Optical, mechanical, and thermal analyses, over 1,000 hours of accelerated life-time tests and several hundred hours of tests in a solar receiver, show that this window satisfies the required criteria for operation in a volumetric solar receiver, whose operating pressure and peak absorber temperature reach 30 bar and 1700°C, respectively.

Description: The FAST Code which is capable of determining structural loads of a flexible, teetering, horizontal axis wind turbine is described and comparisons of calculated loads with test data are given at two wind speeds for the ESI-80. The FAST Code models a two-bladed HAWT with degrees-of-freedom for blade bending, teeter, drive train flexibility, yaw, and windwise and crosswind tower motion. The code allows blade dimensions, stiffnesses, and weights to differ and the code models tower shadow, wind shear, and turbulence. Additionally, dynamic stall is included as are delta-3 and an underslung rotor. Load comparisons are made with ESI-80 test data in the form of power spectral density, rainflow counting, occurrence histograms, and azimuth averaged bin plots. It is concluded that agreement between the FAST Code and test results is good.

Description: A study is reported of predicted flat-plate photovoltaic output in Southern Nevada, and this output is compared to the time variation of the electrical utility load for this area. Included in the comparisons are typical summer time variations of predicted outputs and loads on an hourly basis. Also shown are the time differentials between the utility peak load and the peak photovoltaic output. Plots are also given of the fractions of the output of the photovoltaic systems relative to their peaks that occur at the time of the utility load peak. Finally, the results of a study are reported that investigates the influence of time-of-day purchase prices on the orientation of the modules to maximize revenues. A simple price model based on one used by the local utility for independent power producer purchases is incorporated to show the influence of pricing on optimal orientation.