Said Al-Hallaj

Heat transfer characteristics of liquid flow with micro-encapsulated phase change material: Experimental study

This experimental study investigates the heat transfer characteristics of a liquid flow with micro-encapsulated phase change material (MEPCM). The MEPCM mass concentration is varied between 0 and 20 percent with average particle diameter of 10 μm. Tube wall temperature profile, fluid inlet and outlet temperatures are measured and the corresponding heat transfer coefficient is determined for various operating conditions. A wide range of the controlling parameters, MEPCM concentration, heat flux, inlet temperature, and flow rate are covered. The results showed significant enhancements in heat transfer coefficient (higher than 50%) and reduction in tube wall temperature (higher than 40%). The results also showed that the heat transfer enhancement curve showed resemblance to the MEPCM specific heat curve.

Natural Convection With Micro-Encapsulated Phase Change Material

This study numerically explores the effect of presence of micro-encapsulated phase change material (MEPCM) on the heat transfer characteristics of a fluid in a rectangular cavity driven by natural convection. The natural convection is generated by the temperature difference between two vertical walls at constant temperatures. The phase change material (PCM) melts in the vicinity of the hot wall and solidifies near the cold wall. Unlike the pure fluids, the heat transfer characteristics of MEPCM slurry cannot be simply presented in terms of corresponding dimensionless controlling parameters such as Rayleigh number. In the presence of phase change particles, the controlling parameters’ values change significantly due to the local phase change. The numerical results show significant increase in the heat transfer coefficient (up to 80%) at the considered operating conditions. This increase is a result of the MEPCM latent heat and the increased volumetric thermal expansion coefficient due to MEPCM volume change during melting.

Design and modeling of optical modules for use in the “Emerald Forest” algae photobioreactors

Abstract As part of the “Emerald Forest” concept proposed in previous work by the authors (Teymour, Al-Hallaj, Eltayeb, & Khalil, 2009), photobioreactors for large-scale algae production are developed. Optical waveguides are used to overcome light limitations, and to maximize light collection and optimize light distribution. The finite volume discrete ordinates (FVDO) method is used to model light transport efficiency by different designs of waveguides that can be used to transport light, or change its direction and intensity, as a first step in the design of an efficient waveguide-based algae photobioreactor.

Energy Storage Systems for Smart Grid Applications

Energy storage is a critical component of any initiative to make electric power and mobility more sustainable. As more solar and wind power generation are added to the electric grid, a mismatch between the periods of peak generation and peak demand necessitate some way to store energy and buffer transient fluctuations in the grid. Similarly, to transition from petroleum-based energy for transportation requires renewable technologies for storing energy with high energy density. This chapter addresses energy storage for smart grid systems, with a particular focus on the design aspects of electrical energy storage in lithium ion batteries.

Case Study: A Hybrid Fuel Cell/Desalination System for Caye Caulker

The case study presented in this chapter discusses the key decisions that factor into the design of a hybrid fuel cell/desalination (HFCD) system to supply a developing region with adequate electrical power and water. The focus of this case study is Caye Caulker, a Carribean island located off the coast of Belize. Caye Caulker has limited fresh water sources and currently uses diesel generators as its sole source of power. The goal of this case study is to replace these diesel generators with an HCFD system that can also provide Caye Caulker with potable water.

Renewable Energy Sources and Energy Conversion Devices

Renewable energy sources are those sources that are regenerative or can provide energy, for all practical purposes, indefinitely. These include solar, wind, geothermal, tidal, wave, hydropower and biomass.

Modeling of compression curves of phase change graphite composites using Maxwell and Kelvin models

Materials containing phase change and graphite composites are very attractive materials for energy storage and thermal management applications because of their high thermal conductivity and heat storage characteristics. Mostly, these composites are currently used in thermal management of lithium-ion batteries to regulate the battery temperature and protect the battery from undesirable thermal runaway and also it can be used in other thermal energy storage applications. Several samples with expanded graphite impregnated with phase change material composites such as paraffin wax were tested in quasi-static stress–strain compression tests. To provide these composites with flexibility and compressibility, a special silicon polymer added to the phase change material–expanded graphite composite resulted in a new phase change material with expanded graphite and polymer composite; for which several samples of this composite were tested as well. The compression tests were performed using an Instron 3300R floor model universal testing system at a constant platen speed of 52 mm/min. All tests were conducted at room temperature and they were compressed up to failure. All phase change material–expanded graphite composite samples were tested in-plane and through-plane relative to the expanded graphite compaction directions. Both phase change material–expanded graphite composite samples in in-plane and through-plane directions showed distinct and unique mechanical and thermal characteristic responses. Compression stress–strain tests for all samples were modeled using a combined constitutive viscoelastic polymeric foam model equation based on Kelvin and Maxwell models. In this research, the Maxwell–Kelvin viscoelastic model was used to calibrate the compression tests for expanded graphite, phase change material–expanded graphite, and phase change material with expanded graphite and polymer composites. It was found that ductility and viscous characteristics of the model are due to the presence of expanded graphite whereas brittleness characteristics are due to the presence of phase change material. The polymeric foam model equation is a powerful tool for designing new energy storage composites with targeted mechanical and thermal characteristics such as yield strength, Youngs modulus, thermal conductivity, and latent heat. From curve fitting of the experimental tests of phase change material–expanded graphite composites with the viscoelastic model, several mechanical properties such as elastic and viscous coefficients were computed.

Control of Hybrid Energy Systems

There is growing interest in integrating fuel cells with batteries or supercapacitors to create stand-alone generators. These could be used in applications where diesel generators are commonly used today. The reason for wanting to do this is to reduce system cost.

Case Study: Hybrid PEM Fuel Cell/Li-ion Battery System for a Non-Idling Airport Ground Support Vehicle

The case study presented in this chapter describes the design and implementation of a hybrid system for the elimination of engine idle in airport ground support vehicles. We will first examine the decision-making process by considering several combinations of renewable energy technologies. This will be followed by a discussion of why a PEM (Polymer Electrolyte Membrane) fuel cell/lithium–ion battery system is the most suitable design for this project. We will then discuss the details of the proposed design. The chapter will conclude in a discussion of the project results and a summary of the successes and limitations of the project along with proposed future work.

Hydrogen Production, Storage and Fuel Cells

Hydrogen can be produced through thermal, electrolytic, or photolytic processes using fossil fuels, biomass, or water as a feedstock. Photolytic processes will not be covered here.