Is hydrogen the solution to the world’s energy crisis?
Jon Hiew
With the ongoing energy crisis, it has never been more crucial for scientists and engineers to come up with solutions for alternative sustainable and renewable sources of energy. Being one of the potential solutions to this problem, hydrogen fuel cells have been discussed as one of the most promising sources of energy, as they do not emit greenhouse gases and the supply of hydrogen is abundant. But the technology of hydrogen fuel cells requires development before it can be made publicly available. Within a hydrogen fuel cell, there is a cathode, an anode – which are typically covered in a platinum catalyst – and an electrolyte solution between the two electrodes. Hydrogen gas is pumped towards the anode and the catalyst breaks up the hydrogen gas into protons and electrons, where the protons will travel across the proton exchange membrane electrolyte to the cathode. The electrons also travel towards the cathode, but leave the fuel cell and through a circuit towards a motor to supply energy, where they arrive back at the fuel cell’s cathode. At the cathode, air, which is roughly 21% oxygen gas, flows through and reacts with the hydrogen ions to form only water. This process repeats over again supplying energy, until the hydrogen supply is cut off to the fuel cell.
+ + 4e −
Anode Reaction: 2H 2 → 4H
Cathode Reaction: 4H + + 4e − + O
2 → 2H 2 O
Using electrolysis to create electricity, different types of hydrogen fuel cells work in very similar ways with proton exchange membrane (PEM) fuel cells, whose main application has been in vehicles. This is due to their high energy density, fast start-up time and ability to operate at relatively low temperatures, when compared to other fuel cells. For more stationary applications such as power plants, molten carbonate (MCFC) and solid oxide (SOFC) fuel cells are better suited to these roles, due to their high efficiency and power output. These fuel cells would be used in large fuel cell power plants of megawatt capacity. In addition, both fuel cells operate at higher temperatures of roughly 650°C (MCFC) and 500°C to 1000°C (SOFC), which can be used by combining with heat and power (CHP) plants to improve its efficiency to over 80%. 1 When providing the hydrogen gas needed to power fuel cells, hydrogen has to be extracted from the many different natural compounds it is found in. Hydrogen extracted can be cla ssified into ‘the hydrogen rainbow’, where hydrogen created corresponds to the carbon intensity on the ‘rainbow’ of grey, green and blue. It is currently estimated that roughly 90% of hydrogen produced is grey hydrogen, 2 which originates from fossil fuels and natural gases. Blue hydrogen, which refers to fossil fuels with carbon capture and storage, has been one of the most criticized types of hydrogen due to its high greenhouse gas footprint. Oil and gas industries claim around 90% of emissions are captured, 3
1 https://fuelcellsworks.com/knowledge/technologies/mcfc/. 2 The truth about hydrogen: https://www.youtube.com/watch?v=AGTjKJHu99c. 3 Ibid.
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