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Novel metal hydrides fuel storage cell development
FIVE YEARS AGO, HYDROGEN SOUTH AFRICA (HYSA) SYSTEMS at the University of the Western Cape (UWC) unveiled the fi rst forklift and refuelling station prototypes in Africa to be powered by hydrogen fuel cells. Dr Mykhaylo Lototskyy, a key technology specialist in hydrogen storage and related applications at HySA, and his team developed the prototypes in collaboration with the Department of Science and Innovation (DSI) and Impala Platinum (Implats). The novel metal hydrides used to store the hydrogen that powers the fuel cells of the forklift and to compress the hydrogen for the refuelling station were engineered by HySA by combining certain metallic alloys with hydrogen.
Dr Lototskyy, who is also a Senior Lecturer at the South African Institute for Advanced Materials Chemistry (SAIAMC) at UWC, says: “While scientists have known of so-called AB2-type intermetallic hydrogen storage alloys since the early 1980s, the metal hydrides engineered at HySA Systems and used in the prototypes are unique. Conventionally, the AB2-type alloys make use of a number of specifi c elements which are made up of both A and B components like titanium, zirconium, chromium, manganese and iron. However, our alloys contain these and some other components in certain amounts that results in precise matching of their properties with the requirements of an end-user.”
The metal hydrides also serve as ballast to ensure proper weight distribution and the stability of the prototype forklift. Currently, commercial forklifts use hydrogen stored as a gas in high-pressure composite gas cylinders, which are too light and require manufacturers to place additional ballast in the forklift.
“Through the use of the metal hydrides we engineered, we were able to ensure that the hydrogen pressure in the metal hydride hydrogen storage system on board the forklift does not exceed 185 bar. That is almost two times lower than the typical hydrogen pressure of 350 bar in a commercial fuel cell forklift,” says Dr Lototskyy. HySA Systems is one of three Centres of Competence (CoCs) in the DSI’s HySA Programme, which aims to stimulate innovation along the hydrogen fuel cell technology value chain in South Africa through local manufacture of hydrogen and fuel cell products, and job creation and economic development through the mining and sale of platinum group metals (PMGs). PMGs are used as catalysts in fuel cells to provide a high rate of electrochemical reactions through which hydrogen and oxygen are converted into electricity.
The UWC centre focuses on developing hydrogen fuel cell systems, demonstrators, products and prototypes, performing technology validation and system integration in hydrogen fuel cell technologies. An internationally recognised researcher in the fundamentals of metal hydrides and their application in hydrogen storage, hydrogen compression, hydrogen separation and purifi cation, Dr Lototskyy was appointed Key Programme Manager for the HySA Programme in 2019.
Hydrogen fuel cell storage technology is environmentally friendly and has benefi ts that set it apart from battery-based energy storage technology.
Dr Lototskyy says, “Hydrogen fuel cells off er higher energy storage densities per unit volume varying from 0.33 to 0.51 kWh/litre depending on the storage method. The highest value achieved for rechargeable Li-ion batteries is less than 0.14 kWh/litre. A hydrogen-fuelled fuel cell system can be refuelled in several minutes while a battery needs to be charged for several hours.”
Other advantages are: • Electric power withdrawn from a hydrogen fuel cell system is constant throughout its operation cycle while the maximum power that can be withdrawn from an ordinary battery decreases as the battery discharges.
• Hydrogen fuel cells last longer than batterybased energy storage systems, which reduces operating costs. • The machines are less noisy than those powered by internal combustion engines, do not emit harmful gases and are safe to operate in a confi ned space. • Metal hydrides are a more effi cient way to store hydrogen than storing it as a compressed gas or in liquid form. Hydrogen stored as a compressed gas (350–700 bar) is potentially unsafe in high-pressured fuel cell systems, while liquid hydrogen evaporates easily. • Hydrogen is only released from metal hydrides at high temperatures while metal hydrides can use waste heat instead of electricity to drive hydrogen compression, a potential benefi t to industrial customers. Dr Lototskyy and his team are developing a second prototype of a metal hydride hydrogen storage tank where fast refuelling can be achieved at lower pressures of 100–150 bar.
