M. Said Jiddan Walta

Introduction

Hello, my name is M. Said Jiddan Walta, commonly referred to as Jiddan. This page will be a platform for me to describe the results of my conscious learning and development during my short time in the Numerical Method class.

NPM: 2106718256

Major: Mechanical Engineering

E-mail: m.said11@ui.ac.id

Session Review

23 May 2023 Class

As an introductory class, our lecturer Dr. Ahmad Indra Siswantara introduced himself and his focus of study on the concept of consciousness, and invites us to participate in the discussion on the importance of applying consciousness in our daily lives as well as the recurrence of difficult concepts in the problems that we face that remind us to practice consciousness about the limitations of human understanding. Outside class time, a follow-up discussion was conducted in the class group for practicing consciousness by inviting discussion on the most realistic solution of a typical limit problem. We were invited to explore the notion of infinity and the limitations of computing involving values that are typically referred to as 'undefined'. Lastly, our project for the remainder of the semester was introduced.

Numerical Method - Case Study of Pressurized Hydrogen Storage

Substance Study

For the Numerical Method class, we were tasked with a project on the design and optimization of a Pressurized Hydrogen Storage, with the constraint parameters being the gas pressurized at 8 bars and the required storage volume being 1 liters. Hydrogen as a gas is useful for many industrial purposes as well as an energy source for certain vehicles and industrial appliances, and is often stored by the hundreds of liters in large tanks.

Hydrogen in its frequently encountered diatomic form of H2 gas is the lightest gas in the universe and is generally unreactive, but is readily combustible in its gaseous form. As an ultra-light gas, hydrogen occupies a substantial volume under standard conditions of pressure, i.e. atmospheric pressure. In order to store and transport hydrogen efficiently, this volume must be significantly reduced. The general methods for improving hydrogen transport and storage efficiency is through high-pressure storage in the gaseous form, very low temperature storage in the liquid form, or hydride-based storage in the solid form, though the most common being the first two. Having the highest yield of hydrogen in a fixed container volume requires pressurization up to 700 bars or more, which requires large amounts of energy and strong container design. Liquid hydrogen is cryogenic in nature, and therefore needs to be stored in extremely low temperatures to keep it in its liquid state, or at least to keep a majority of it from evaporating. For the case that we are assigned, the required storage amount is small and the pressure is also constrained, therefore the focus is not the efficiency of hydrogen yield being stored but instead the cost and material effectiveness of the container.

Hydrogen density at 8 bars and 30 degrees Celsius

For the purpose of this project, it is important to begin designing the product with understanding the substance that it is meant to store, in this case hydrogen pressurized at 8 bars.

In its gaseous form at 8 bars of pressure and local indoor temperature in Indonesia being around 30 degrees Celsius, hydrogen gas has a density of 0.627 kilograms per cubic meter, which results in 1 liter or 0.001 cubic meters of the gas weighing 0.627 grams or less than 0.001 kg. This means that storing the gas at these conditions will only require a container material and design that can withstand wall pressure of 8 bars, while ideally having lower density such that the total weight of the container far exceeds the weight of the gas being stored.

Material Choice

Our goal in this case is to select a suitable material for the storage tank, with our priorities being focused on fulfilling the load requirements presented by the hydrogen in a safe manner, low weight, and cost-effectiveness. Safety is of great importance when designing hydrogen storage. The material used must possess high strength, resistance to fracture, and be capable of withstanding high pressures. Metals like steel and aluminum alloys are commonly employed due to their mechanical properties. However, special attention must be given to hydrogen embrittlement, a phenomenon that can cause material degradation and reduce safety. Thus, selecting materials with high resistance to hydrogen embrittlement, such as specific grades of steel, becomes crucial. Hydrogen has the smallest molecule size, which means it can permeate through certain materials over time. Permeation can lead to hydrogen loss, compromising the efficiency of the storage system and potentially raising safety concerns. Hence, selecting materials with low hydrogen permeability is important. Metals like steel and aluminum have relatively low permeability, especially when coated with appropriate barriers to minimize permeation. Composites, on the other hand, can have higher permeability, although this can be mitigated by employing diffusion barriers or modifying the polymer matrix.

On the topic of optimization of weight, composite materials, such as carbon fiber reinforced polymers (CFRP), offer an advantageous balance between strength and weight. CFRP has been commonly used for hydrogen storage tanks in certain regions, having the walls consist of a lightweight polymer matrix reinforced with carbon fibers, providing exceptional strength-to-weight ratios. These materials enable the construction of lightweight tanks. The cost of materials plays a significant role in the overall economics of hydrogen storage systems. Metals like steel are relatively affordable and widely available, making them cost-effective choices for bulk storage applications. However, advanced alloys with improved resistance to hydrogen embrittlement can be more expensive. In contrast, composite materials like CFRP have higher upfront costs due to their manufacturing processes.

With these factors in mind, the most likely choice is selecting a lighter grade of steel with mechanical properties that can supplement the requirements, with additional modifications and treatments to the material to further lower its hydrogen permeability.