Solar Engineering Of Thermal Processes

This article reports on the International Nanofluid Property Benchmark Exercise, or INPBE, in which the thermal conductivity of identical samples of colloidally stable dispersions of nanoparticles or “nanofluids,” was measured by over 30 organizations worldwide, using a variety of experimental approaches, including the transient hot wire method, steady-state methods, and optical methods. The nanofluids tested in the exercise were comprised of aqueous and nonaqueous basefluids, metal and metal oxide particles, near-spherical and elongated particles, at low and high particle concentrations. The data analysis reveals that the data from most organizations lie within a relatively narrow band (±10% or less) about the sample average with only few outliers. The thermal conductivity of the nanofluids was found to increase with particle concentration and aspect ratio, as expected from classical theory. There are (small) systematic differences in the absolute values of the nanofluid thermal conductivity among the various experimental approaches; however, such differences tend to disappear when the data are normalized to the measured thermal conductivity of the basefluid. The effective medium theory developed for dispersed particles by Maxwell in 1881 and recently generalized by Nan et al. [J. Appl. Phys. 81, 6692 (1997)], was found to be in good agreement with the experimental data, suggesting that no anomalous enhancement of thermal conductivity was achieved in the nanofluids tested in this exercise.

A Benchmark Study on the Thermal Conductivity of Nanofluids

A review on recent size optimization methodologies for standalone solar and wind hybrid renewable energy system

Gas diffusion layer for proton exchange membrane fuel cells—A review

Overview on recent developments in energy storage: Mechanical, electrochemical and hydrogen technologies

Technological challenges and optimization efforts of the Stirling machine: A review

The absence of clean electricity in Tunisia means a large number of people who are deprived of much needed socioeconomic development. However, wind and solar radiation are two renewable energy resources that are abundantly available in Tunisia. Although, it is not feasible for these two resources separately to meet high electricity demands, hybrid applications can be the best way to get over this weakness. This paper investigated the potential operation of Hybrid Energy System (photovoltaic (PV)/wind turbine/diesel system with batteries storage in the northernmost city in Africa, city of Bizerte in Tunisia. The Hybrid Optimization Model for Electric Renewable simulation software was used to simulate and optimize the technical-economic feasibility of the system. There were several system configurations with and without battery storage elements which will be studied and analyzed. The simulations will be focused on the net present costs, levelized cost of energy, produced excess electricity and the reduction of CO2 emission for the given hybrid configurations. Moreover, the comparison between the economic viability of the stand-alone and the grid-connected HES will be discussed.

Assessment viability for hybrid energy system (PV/wind/diesel) with storage in the northernmost city in Africa, Bizerte, Tunisia

Determination of adequate regenerator for a Gamma-type Stirling engine

Solar concentrator technology is becoming more prevalent today and studies performed on this subject have gained a great deal of interest in the world. In order to design a new solar parabolic concentrator that will be installed to operate in more efficient and more feasible way, it is necessary in the first step to analyze such parameters like solar irradiations values, and solar angles. Therefore, in this work, theoretical studies have been performed for solar angles using time and geographic parameters in Tunisia. An experimental measurement of solar irradiations has been done using a high precision metrological station to determine the diffuse, the direct and the global irradiations on the horizontal plane. In the second step each solar concentrator technology has its specifications in terms of mobility, orientation and the accuracy of the tracking system. In this work three pilot sun tracking systems for a solar parabolic concentrator were designed and constructed in the Research and Technology Center of Energy in Tunisia. Those trackers are able to follow the sun position on both axes (azimuth and elevation angles). We have described and determined the sun tracking errors of each one. A comparative study of the three sun tracking systems with a commercial tracker has been conducted. Basing on efficiency and economical criteria one of the sun tracking systems was selected. The total price of the chosen tracker is estimated to be around 1300 Euros and its tracking error is inferior to 0.2°. The advanced accuracy of the new tracker was achieved with the use of reduction gear unit.

Sassi Ben Nasrallah

Papers

Technological challenges and optimization efforts of the Stirling machine: A review

Assessment viability for hybrid energy system (PV/wind/diesel) with storage in the northernmost city in Africa, Bizerte, Tunisia

Determination of adequate regenerator for a Gamma-type Stirling engine

Design and construction of sun tracking systems for solar parabolic concentrator displacement

Numerical simulation of absorption-desorption cyclic processes for metal-hydrogen reactor with heat recovery using phase-change material