Experimental and Theoretical Investigation of Performance of a Solar Chimney Model, Part I: Experimental Investigation

This paper presents the experimental data that was collected from small pilot solar chimney. The experimental data together with ambient conditions are used to evaluate the performance and study the behavior of the solar chimney; this data will be used for comparison with theoretical models in another paper [part II). The solar chimney prototype was designed and constructed at the Subrata Faculty of Engineering-Libya. The data were collected over several days of June 2011. The solar chimney system contains two main components; the solar collector and the solar chimney. The solar collector root‘ has a circular area of126 m3, the solar chimney is a PVC tube with internal diameter of 0.2 m and the total height of chimney is 9.3 m. The measurements include the intensity of solar radiation inside/outside the collector, temperature and velocity of air at the entrance of the chimney, temperature and speed of wind outside the collector, temperature of the ground inside collector al1d temperature measurements of air at speci?c points at different levels throughout the collector. Solar irradiance was found to affect the chimney temperature and subsequently affects chimney air velocity. The experimental results showed that temperature differences of (30 - 45°C) were recorded between the ambient temperature and that of air inside the chimney in the middle of the day, where the highest air temperature of 73.4°C was recorded at the entrance of the solar chimney. The maximum air velocity of 3.6 m/s was recorded inside the solar chimney at noon on 9 June. Wind speed outside the collector had a small effect on the speed of the air inside the chimney and tends to change slightly, hence, can neglect influence of wind speed on the performance of the system. Also the experimental results indicate that such type of system can trap a suf?cient amount of solar radiation, which elevates the air temperature to a suf?cient value able to generate enough air ?ow to operate a wind turbine to produce electricity; this means the solar chimney system for electricity production can work in the north-western part of Libya in the summer time at least.

Effect of thermal collector configuration on the photovoltaic heat transfer performance with 3D CFD modeling

The shape and material of the collector configuration in photovoltaic thermal collectors (PVTs) are adjusted to alter the effectiveness of thermal conductivity. Good thermal conductivity between units plays an important role in heat absorption, and photovoltaic modules can increase electrical and thermal efficiency. In this study, a 3D computational fluid dynamics simulation of collector design in PVTs was carried out using Solidworks. The modeling was carried out on variations in the shape of boxes, pipe boxes, and triangle boxes with aluminum, copper, and mild steel materials on the thermal collector. The triangular box shape made of copper in the collector had a minimum temperature of 301.01 K when the heat generated was 1,000 W/m2 and the flow volume was 0.0005 m3/s. The difference in the heat generation rate and volume flow rate in each collector variation affects the collector temperature.

Low-Cost Cloud-Enabled Wireless Monitoring System for Linear Fresnel Solar Plants

This paper presents the design of a cost-effective online wireless monitoring system for two linear Fresnel reflector (LFR) solar plants located in two different countries. The first LFR plant is installed in the SEKEM medical center near Belbis city, Egypt, while the second is installed in the campus of the University of Palermo, Italy. The proposed system is a standalone system that reduces the interaction of labor as it offers online wireless monitoring for important parameters of the LFR such as solar irradiance, ambient temperature, outlet and inlet collector temperature and heat transfer fluid flow. For that purpose, a wireless sensor network (WSN) based on Arduino Mega boards coupled with XBee modules are used. The ZigBee XBee modules operate at 2.4 GHz, which have the advantages of being low cost and relatively low power consumption. The wireless nodes are supplied by solar paneled power banks, and send the data to a cloud in order to monitor both LFR plants remotely. The proposed system has been implemented and tested successfully before the future deployment on the LFR plants.

A Charge-Based Mechanistic Study into the Effects of Process Parameters on Fiber Accumulating Geometry for a Melt Electrohydrodynamic Process

Melt electrohydrodynamic processes, in conjunction with a moveable collector, have promising engineered tissue applications. However, the residual charges within the fibers deteriorate its printing fidelity. To clarify the mechanism through which the residual charges play roles and exclude the confounding effects of collector movement, a stationary printing mode is adopted in which fibers deposit on a stationary collector. Effects of process parameters on generalizable printing outcomes are studied herein. The fiber deposit bears a unique shape signature typified by a central cone surrounded by an outer ring and is characterized by a ratio of its height and base diameter Hdep/Ddep. Results indicate Hdep/Ddep increases with collector temperature and decreases slightly with voltage. Moreover, the steady-state dynamic jet deposition process is recorded and analyzed at different collector temperatures. A charge-based polarization mechanism describing the effect of collector temperature on the fiber accumulating shape is apparent in both initial and steady-state phases of fiber deposition. Therefore, a key outcome of this study is the identification and mechanistic understanding of collector temperature as a tunable process variable that can yield predictable structural outcomes. This may have cross-cutting potential for additive manufacturing process applications such as the melt electrowriting of layered scaffolds.

Thermal Efficiency of a Solar Air-Heating Collector with a Metal Chip Absorber

It is known that one of the main issues of heat transfer in complex designs of solar air-heating collectors is the problem of determining the coefficient of convective heat transfer in some parts of absorbers. The article studies the processes of heat transfer occurring in a solar air-heating collector with an absorber, which is a system of metal flow chips and a V-shaped surface. A description of the design of a solar air-heating collector with a metal chip absorber is given. The absorber allows us to increase the contact surface between the coolant and the absorber. The experimental procedure and the results are presented. The experiments have shown that within the range of 850 – 950 W / m2 of direct incident solar radiation density, the average heating of coolant is 17.5 °C; within the range of 650 – 750 W / m2, it is 14.1 °C; within the range of 450 – 550 W / m2, it measures 10.1 °C. The maximum coolant heating is 27 °C which is equal to the output collector temperature 60 °C. The average heating of the coolant is 14 °C, which corresponds to the average output temperature of 45 °C. According to the data obtained in the experiment, empirical formulas are concluded. They are presented in the form of the dependence Nu = f (Re), it is aimed at determining the heat transfer coefficient of flow metal chips and V-shaped absorbers of a solar air-heating collector. The dependence of the absorbers heat transfer from metal flow chips and the V-shaped surface of the solar air-heating collector on the Re numbers within the range of 103÷104 is shown. A formula is derived that allows us to compare the effectiveness of absorbers of various types with a flat absorber of a solar air-heating collector

Prototype of lineal solar collector Fresnel

The development of a prototype linear solar collector Type Fresnel, has a purpose the use of direct solar heat radiation for water heating and/or steam production, as an alternative to supply conventional water heating systems or steam generators, which consume energy from fossil fuels. For the development of the system, used the solar radiation of the UTS, located in Bucaramanga, Colombia, is identify the mathematical models to perform the sizing, then materials based on technical specifications and availability in Colombia, in order to perform the assembly and field tests, measuring the ambient and in the collector temperature to determine the efficiency of the model. It should be noted that, the model presented does not have a control system for flow, temperature, pressure and level, it has no solar tracking of any kind; Its movement was done manually with each reflex. Finally, the model does not have a hydraulic system forced, and has a preheater at the entry of the concentration point.

Design and CFD Simulation of Solar Water Heater Used in Solar Assisted Biogas System

Difficulty in collecting conventional energy sources as well as their economic benefits including saving of time ,money, fertilizer of higher nutrient value, availability of waste easy and comfortable cooking, health benefits including the reduction diseases and environmental benefits such as saving of forest, clear surrounding were the main motivational factors for this research. However, climate temperatures in areas are too low to enable enough biogas production in small unheated digesters to meet the energy requirements of the institute, so the objectives of were to overcome the problem of energy by solar assisted with the hot water storage tank. In this research mathematical modeling of the solar water heater was designed and the analysis of heat transfer coefficient (losses) through the flat plate collector was done and the techniques that used to reduce these losses also mentioned. From the simulation results; the effect of mesh type on flat plate collector, temperature rise, and pressure drop were characterized including flow type in the laminar and turbulent using CFD approach. The FPC was needed for the preparation of the hot water for the heating of the waste food for the selected fixed dome digester with 2m2 was designed. The effect of water mass flow rate 0.01-0.05kg/s on flat plate collector, temperature rise, pressure drop, and velocity was characterized including the variation of flow types intensity using CFD approach. The optimal temperature to this process was 37 °C.The results obtained have been validated with analytical results

Leveraging Energy Storage in a Solar-Tower and Combined Cycle Hybrid Power Plant

A method is presented to enhance solar penetration of a hybrid solar-combined cycle power plant integrated with a packed-bed thermal energy storage system. The hybrid plant is modeled using Simulink and employs systems-level automation. Feedback control regulates net power, collector temperature, and turbine firing temperature. A base-case plant is presented, and plant design is systematically modified to improve solar energy utilization. A novel recycling configuration enables robust control of collector temperature and net power during times of high solar activity. Recycling allows for improved solar energy utilization and a yearly solar fraction over 30%, while maintaining power control. During significant solar activity, excessive collector temperature and power setpoint mismatch are still observed with the proposed recycling configuration. A storage bypass is integrated with recycling, to lower storage charging rate. This operation results in diverting only a fraction of air flow to storage, which lowers the storage charging rate and improves solar energy utilization. Recycling with a storage bypass can handle larger solar inputs and a solar fraction over 70% occurs when following a drastic peaking power load. The novel plant configuration is estimated to reduce levelized cost of the plant by over 4% compared to the base-case plant.

Exergy Analysis of a Flat Plate Solar Collector With Grooved Absorber Tube Configuration Using Aqueous ZnO–Ethylene Glycol

In this study, the exergetic performance of a flat plate solar collector (FPSC) setup with ZnO-based ethylene glycol (EG)/water nanofluid as a working fluid has been evaluated against that of EG/water. As a passive means to augment the rate of heat transfer, internally grooved tubes of two different pitches (e = 0.43 and e = 0.44) have been examined and compared against the performance of plain tube. The mass flow rate was fixed at 0.015 kg/s and the volume fraction of ZnO nanoparticles is ф = 0.02% v/v. The results indicate an enhancement in exergy efficiency of 44.61% when using the grooved tube (e = 0.44) against plain tube without the nanofluid and 39.17% when nanofluid is used. Using the nanofluid enhanced the exergy efficiency of the FPSC by a maximum of 73.81%. Maximum exergy efficiency obtained was 5.95% for grooved tube (e = 0.44) with nanofluid as working fluid and is in good agreement with previous literature. Exergy destruction/irreversibility due to temperature differences and heat flow within the system has been reported. Sun-collector temperature difference accounts for nearly 86–94% of the irreversibility. The results for thermal efficiency of this experimental setup have been published and summarized in this study for reference.