National University of Malaysia

About: National University of Malaysia is a education organization based out in Kuala Lumpur, Malaysia. It is known for research contribution in the topics: Population & Heat transfer. The organization has 26593 authors who have published 41270 publications receiving 552683 citations. The organization is also known as: NUM & Universiti Kebangsaan Malaysia.

Review of solar air collectors with thermal storage units

Abstract: Thermal energy storage is one of the most efficient ways to store solar energy for heating air by energy collected from sun. The relative studies are involved to the type of collection with the type of storage, i.e. separated to each other or integrated. This review summarizes the previous works on solar air heaters with storage materials include greenhouse, encapsulation, and the latest development in the solar thermal energy storage with air as a heat transfer fluid. The recent researches focused on the phase change materials (PCMs), as latent heat storage is more efficient than sensible heat storage. It has been appeared that PCM with high latent heat and suitable geometry are required for optimum thermal performance of solar air heater. The recent designs of solar air heaters with thermal storage units reduced the cost and the volume when integrated in one product.

Biohydrogen production through photo fermentation or dark fermentation using waste as a substrate: Overview, economics, and future prospects of hydrogen usage

Abstract: Hydrogen has been introduced as a potential replacement for energy resource due to the depletion of fossil fuel and raising awareness about global climate change and health problems caused by the combustion of fossil fuel. One of the attractive options to produce hydrogen is through microbial fermentation which can be classified into biophotolysis, dark fermentation, photofermentation, and microbial electrolysis cell. Among these, dark fermentation and photofermentation technologies were processes that were being studied widely. One of the reasons is that organic waste could be reused as a substrate during biohydrogen production. Although the current biohydrogen yields are low, it is expected that with improvements technology and genetic engineering, the amount of generated biohydrogen could be enhanced tremendously, and provide a sustainable way of reutilizing waste as a substrate. Thus, this paper reviews the principles of photofermentation and dark fermentation by reusing various wastes as substrates. The resulting performances, limitations, as well as future prospects of hydrogen usage and hydrogen economy are also discussed. © 2013 Society of Chemical Industry and John Wiley & Sons, Ltd

Direct conversion technologies of methane to methanol: An overview

Abstract: The emission of greenhouse gases (GHGs) is a major air pollution issue that affects climate change across the globe. Methane (CH 4 ), behind carbon dioxide (CO 2 ), is the second most abundant GHGs that negatively impact the atmosphere layer. Many studies have been conducted to identify a method for reducing the concentration of methane in the atmosphere. Converting methane to alternative forms source of energy, such as methanol, is a preferred method for methane reduction. This review aims to present an overview of recent literature that focuses on conversion of methane to methanol, with a focus primarily on the manufacturing systems and processes used in this conversion. Basic descriptions are given of several relevant technologies for converting methane to methanol and their characteristics, including conventional catalytic processes, plasma technology, photo-catalysts, supercritical water processes, biological processes and other processes. All of these options are feasible for use in the conversion process of methane to methanol.