Analysis of advanced supercritical carbon dioxide power cycles with a bottoming cycle for concentrating solar power applications

A number of studies have been performed to assess the potential of using supercritical carbon dioxide (S-CO 2 ) in closed-loop Brayton cycles for power generation. Different configurations have been examined among which recompression and partial cooling configurations have been found very promising, especially for concentrating solar power (CSP) applications. It has been demonstrated that the S-CO 2 Brayton cycle using these configurations is capable of achieving more than 50% efficiency at operating conditions that could be achieved in central receiver tower type CSP systems. Although this efficiency is high, it might be further improved by considering an appropriate bottoming cycle utilizing waste heat from the top S-CO 2 Brayton cycle. The organic Rankine cycle (ORC) is one alternative proposed for this purpose; however, its performance is substantially affected by the selection of the working fluid. In this paper, a simple S-CO 2 Brayton cycle, a recompression S-CO 2 Brayton cycle, and a partial cooling S-CO 2 Brayton cycle are first simulated and compared with the available data in the literature. Then, an ORC is added to each configuration for utilizing the waste heat. Different working fluids are examined for the bottoming cycles and the operating conditions are optimized. The combined cycle efficiencies and turbine expansion ratios are compared to find the appropriate working fluids for each configuration. It is also shown that combined recompression-ORC cycle achieves higher efficiency compared with other configurations

Rectifying antenna and method of manufacture

In accordance with the present invention, an aperture rectenna is provided where the substrate is transparent and of sufficient mechanical strength to support the fabricated structure above it. An aperture antenna is deposited on the transparent substrate and a metal-insulator-metal (MIM) diode is constructed on top of the aperture antenna. There is an insulating layer between the aperture antenna metal and the metal ground plane optimized to maximize the collection of incident radiation. The top of the structure is capped with a metal ground plane layer, which also serves as the DC connection points for each rectenna element

High-frequency feed structure antenna apparatus and method of use

An antenna apparatus for the reception of, and or transmission of, electromagnetic energy, the apparatus including a non-radiating dielectric waveguide aperture coupled to at least one dielectric rod antenna, which is electromagnetically coupled to a transmission line element

Dual-polarized feed antenna apparatus and method of use

An antenna apparatus and method for the interception of randomly polarized electromagnetic waves utilizing a dual polarized antenna which is excited through a cross-slot aperture using two well-isolated orthogonal feeds

Evaluation of Pressure Drop and Particle Sphericity for an Air-rock Bed Thermal Energy Storage System

Abstract The pressure drop of a packed bed thermal energy storage system with irregular shaped solid pellets and tank-to-particle diameter ratio of 10.4 is investigated. The bed height to diameter ratio is 2. The particle sphericity is calculated and used to compare pressure drop correlations to the measured values in the particle Reynolds number range of 353 ≤ Re p ≤ 5206

Experimental And Theoretical Analysis Of The Goswami Cycle Operating At Low Temperature Heat Sources

The Goswami cycle is a cycle that combines an ammonia-water vapor absorption cycle and a Rankine cycle for cooling and mechanical power purposes by using thermal heat sources such as solar energy or geothermal steam. In this paper, a theoretical investigation was conducted to determine the performance outputs of the cycle, namely, net mechanical power, cooling, effective first law efficiency and exergy efficiency, for a boiler and an absorber temperature of 85 °C and 35 °C, respectively, and different boiler pressures and ammonia-water concentrations. In addition, an experimental investigation was carried out to verify the predicted trends of theoretical analysis and evaluate the performance of a modified scroll expander. The theoretical analysis showed that maximum effective first law and exergy efficiencies were 7.2% and 45%, respectively. The experimental tests showed that the scroll expander reached a 30-40% of efficiency when boiler temperature was 85 °C and rectifier temperature was 55 °C. Finally, it was obtained that superheated inlet conditions improved the efficiency of the modified expander

Nanomaterials for Hydrogen Storage Applications: A Review

Nanomaterials have attracted great interest in recent years because of the unusual mechanical, electrical, electronic, optical, magnetic and surface properties. The high surface/volume ratio of these materials has significant implications with respect to energy storage. Both the high surface area and the opportunity for nanomaterial consolidation are key attributes of this new class of materials for hydrogen storage devices. Nanostructured systems including carbon nanotubes, nano-magnesium based hydrides, complex hydride/carbon nanocomposites, boron nitride nanotubes, TiS2/MoS2 nanotubes, alanates, polymer nanocomposites, and metal organic frameworks are considered to be potential candidates for storing large quantities of hydrogen. Recent investigations have shown that nanoscale materials may offer advantages if certain physical and chemical effects related to the nanoscale can be used efficiently. The present review focuses the application of nanostructured materials for storing atomic or molecular hydrogen. The synergistic effects of nanocrystalinity and nanocatalyst doping on the metal or complex hydrides for improving the thermodynamics and hydrogen reaction kinetics are discussed. In addition, various carbonaceous nanomaterials and novel sorbent systems (e.g. carbon nanotubes, fullerenes, nanofibers, polyaniline nanospheres and metal organic frameworks etc.) and their hydrogen storage characteristics are outlined

Synthesis, Characterization, and Applications of ZnO Nanowires

ZnO nanowires (or nanorods) have been widely studied due to their unique material properties and remarkable performance in electronics, optics, and photonics. Recently, photocatalytic applications of ZnO nanowires are of increased interest in environmental protection applications. This paper presents a review of the current research of ZnO nanowires (or nanorods) with special focus on photocatalysis. We have reviewed the semiconducting photocatalysts and discussed a variety of synthesis methods of ZnO nanowires and their corresponding effectiveness in photocatalysis. We have also presented the characterization of ZnO nanowires from the literature and from our own measurements. Finally, a wide range of uses of ZnO nanowires in various applications is highlighted in this paper