We return with the fourth part of our series, in which we answer the most frequently asked questions and concerns about hydrogen and its potential applications in a modern and sustainable economy.
Today we will focus on the differences between an electrolyzer and a fuel cell and look at different hydrogen generator technologies.
If you haven’t already, be sure to check out the previous materials in this series:
1. Frequently Asked Questions about Hydrogen #1
2. Frequently Asked Questions about Hydrogen #2
3. Frequently Asked Questions about Hydrogen #3
8. What are the differences between an electrolyzer and a fuel cell?
An electrolyzer and a fuel cell are separate devices crucial for producing and utilizing hydrogen as an energy carrier.
Function and process: An electrolyzer is used to produce hydrogen by splitting water into its constituent elements – hydrogen and oxygen – when exposed to an electric voltage. A fuel cell is a device that works in reverse, using the electrochemical reaction of hydrogen and oxygen to produce electricity, water/steam, and heat.
Application: Electrolysers are primarily used to produce hydrogen, which can then be stored and used as an energy carrier and clean feedstock in various sectors. Fuel cells, on the other hand, are used as energy sources in hydrogen vehicles (FCEVs) and to convert hydrogen back into electricity and heat. This is particularly important for increasing the efficiency of renewable energy installations by utilizing surplus renewable energy (it should be noted that depending on current technologies, fuel cell efficiency varies from about 30-65%, resulting in some energy loss during re-conversion).
Energy source: As mentioned, an electrolyzer requires an external source of electrical energy to carry out the water-splitting process. This means it can be powered by energy from the grid or directly from renewable energy sources such as solar or wind power. In contrast, a fuel cell utilizes the reaction of hydrogen and oxygen to directly generate electrical energy.
These differences illustrate that electrolyzers and fuel cells have different functions and applications, but both will play a crucial role in the evolving hydrogen ecosystem.
9. What electrolyzer technologies are being developed?
Among the most promising electrolysis technologies, we mention alkaline electrolyzers (AWE), proton exchange membrane electrolyzers (PEM), anion exchange membrane electrolyzers (AEM), and solid oxide electrolyzers (SOEC). They differ in terms of commercialization level, specific advantages, and application ranges.
Alkaline Electrolysis
It is the most mature and widely used commercial electrolytic hydrogen production method. An AWE electrolyzer cell consists of electrodes (anode and cathode) immersed in an alkaline electrolyte solution, facilitating the flow of ions between the electrodes. Key advantages of alkaline technology include maturity and a high level of technology readiness, efficiency, durability, and applicability to MW-scale plants. The challenge, however, is that they are less flexible in operating under varying loads.
Therefore, SES Hydrogen Energy’s technological goal is to achieve increased cooperation of our alkaline devices with renewable energy sources, which will improve the process and increase electrolysis efficiency.
PEM Electrolyzers
Instead of a liquid electrolyte, they use a polymer membrane to separate hydrogen and oxygen during water electrolysis. The advantages of this technology are relatively high efficiency, operational flexibility, as well as more effective prevention of hydrogen and oxygen mixing. However, a challenge is the corrosive working environment, which results in higher purchase and maintenance costs due to the use of electrodes made of expensive noble metals such as platinum or iridium.
AEM Electrolyzers
This is an up-and-coming hydrogen production technology, combining the advantages of alkaline and PEM technologies. By using lower-cost components that do not contain platinum group metals, this technology enables cost reductions and potentially longer device life.
AEM electrolyzers are relatively new and are not as popularized as PEMs, let alone alkaline electrolyzers. At SES Hydrogen Energy, we recognize their significant potential and are focused on developing our own AEM electrolyzers to increase efficiency and lower the target cost of hydrogen production.
SOEC Electrolyzers
They are currently at an early stage of technological maturity. They operate at high temperatures, which also allows for the utilization of waste heat from industrial processes. They are highly energy efficient, but susceptible to material degradation due to operating temperatures of around 850-1200°C.