International Journal of Smart Grid and Clean Energy Design of hydrogen reactor based on decomposition of water by aluminum as an alternative to gas fuel Risse Entikaria Rachmanita , Yuli Hananto , Masrur Ridho Akbar Renewable Energy Engineering, Politeknik Negeri Jember, Jember 68101, Indonesia Abstract Hydrogen is the most abundant element in the universe which is a source of energy obtained through several processes, one of which is the decomposition of water by aluminum.This reaction aided by NaOH as a binder layer of aluminum oxide on the surface of the aluminum so that the aluminum dissolved with the solution. This study aims to design a hydrogen reactor with a semi-continuous flow system where this system can produce hydrogen gas by refilling aluminum and removing wasted periodically without affecting the hydrogen gas produced. Hydrogen gas produced by semi-continuous hydrogen reactors to be used as fuel in gas stoves, and compared to gas stoves fueled by LPG. The design of hydrogen reactors uses materials that are not affected by the corrosive of NaOH. The hydrogen reactor is consist of several main parts including the reactor made of glass, reservoir, inlet and bubbler made of PVC, and gas storage tubes with iron plate material. The reactor performance was tested by reacting two variations of materials including used aluminum cans and aluminum foil. The first testing using 30 grams of used aluminum cans produces hydrogen gas of 24 liters, while the second testing using 36.54 grams of aluminum foil produced of 49 liters of hydrogen gas. The power produced by hydrogen stove ranges from 1.02 - 1.11 kW with a maximum efficiency of 66.02%, while the LPG stove ranges from 1.18 - 1.27 kW with a maximum efficiency of 80.13%. Keywords: Hydrogen reactor, semi-continuous flow system, decomposition of water, aluminum, stove 1. Introduction Hydrogen is one of the most abundant elements with a percentage of 70% of the total elements of the universe and is usually found on earth in the form of water and hydrocarbons such as methane. Hydrogen gas is not available in nature in its pure form, but can be produced through several processes including electrolysis, steam methane reforming, biomass gasification, and others. Decomposition of water using metals is one method for producing hydrogen gas chemically by utilizing the corrosion reaction of several metals such as zinc, magnesium and aluminum in water so that the hydrogen element is separated from the oxygen element that binds it [1], [2]. Aluminum is the most common metal used in the water decomposition process because of its high availability and easy to recycle. The total hydrogen gas produced depends on the mass of aluminum used, where 1 kg of hydrogen gas requires 9 kg of pure aluminum [3], [4]. In previous studies, using aluminum waste as the main ingredient in the process of decomposition of water to produce hydrogen gas, where waste that has a high enough aluminum content can be used to produce hydrogen gas through the water decomposition process [5], [6], [7]. This study aims to design a reactor with a semi-continuous flow system where this system can produce hydrogen gas by refilling aluminum and periodic waste disposal, but it has no effect on the hydrogen gas produced.The system is close to the recommendations of research conducted by Ahmad, F. (2010) [8], which suggests to design a reactor with a continuous flow system that is able to produce hydrogen gas continuously as needed. * Manuscript received May 8, 2020; revised December 14, 2020. Corresponding author. E-mail address: risse_rachmanita@polije.ac.id doi: 10.12720/sgce.10.1.8-20