Advanced High Temp PEM Fuel Cells Explained

Edward Brown

Advanced High Temp PEM Fuel Cells Explained

High Temperature Proton Exchange Membrane fuel cells (HT-PEMFC) are a type of PEM fuel cells that can operate at temperatures between 120 and 200°C. These fuel cells are used for both stationary and portable applications. The membrane in HT-PEM fuel cells is made of an acid and temperature-resistant polymer, commonly polybenzimidazole (PBI) with phosphoric acid as the electrolyte. HT-PEM fuel cells are less sensitive to impurities and can be operated with reformate gas with hydrogen concentrations of about 50 to 75%. They can use a variety of fuels such as methanol, ethanol, natural gas, and LPG, which are reformed in a reformer to produce hydrogen-rich reformate gas.

These fuel cells offer a balance-of-plant system efficiency of 35-45% for methanol-fueled systems and can reach up to 63% cell efficiency. Methanol is the most commonly used fuel for HT-PEM fuel cells due to its simplicity and efficiency in steam reforming. HT-PEM fuel cells have several strengths, including no water management for humidification, utilization of waste heat for combined heat and power (CHP), simple cooling, the ability to use various fuels, and high system efficiency. However, they also have weaknesses such as longer start-up time, the need for a stack heating component, and higher platinum content in the membrane electrode assembly. HT-PEM fuel cells find applications in stationary power systems and as range extenders for electric vehicles.

Development of HT-PEM Fuel Cells

HT-PEM fuel cells emerged in 1995 as a revolutionary advancement in the fuel cell industry. These polymer electrolyte membrane fuel cells were specifically designed to operate at higher temperatures, offering improved resistance to impurities compared to other types of PEM fuel cells.

The membrane material plays a crucial role in the development of HT-PEM fuel cells. Acid and temperature-resistant polymers like polybenzimidazole (PBI) are utilized, enabling the cells to withstand harsh conditions and act as efficient electrolytes. Typically, phosphoric acid is used as the electrolyte in HT-PEM fuel cells.

One of the key differentiating factors of HT-PEM fuel cells is their ability to tolerate impurities. Unlike low-temperature PEM fuel cells, which require high-purity hydrogen, HT-PEM fuel cells can operate with reformate gas containing hydrogen concentrations ranging from 50 to 75%. Additionally, HT-PEM fuel cells exhibit a higher tolerance to carbon monoxide, enabling them to withstand concentrations of up to 3 Vol-%.

Operating at cell temperatures ranging from 150 to 180 °C, HT-PEM fuel cells offer versatility in fuel selection. They can utilize a wide range of fuels, including methanol, ethanol, natural gas, and LPG, among others. These fuels are reformed in a reformer to produce hydrogen-rich reformate gas, which is then used for power generation in the fuel cells.

Furthermore, the membrane electrode assembly used in HT-PEM fuel cells serves a dual purpose by facilitating efficient hydrogen separation. This allows the cells to extract ultrapure hydrogen from diluted or impure hydrogen-containing gases, enhancing overall performance.

Strengths of HT-PEM Fuel Cells

HT-PEM fuel cells offer several key strengths that make them stand out among other fuel cell types:

  1. No water management: Unlike other fuel cell types, HT-PEM fuel cells eliminate the need for water management and humidification of the membrane, simplifying the system design.
  2. Waste heat utilization: The waste heat generated by the stack, operating at temperatures between 130 and 180°C, can be effectively harnessed for combined heat and power (CHP) applications, improving overall system efficiency.
  3. Simple cooling: Due to the higher stack temperature compared to LT-PEMFC, cooling the stack in HT-PEM fuel cells is relatively straightforward, reducing complexity and maintenance requirements.
  4. Ability to use various fuels: HT-PEM fuel cells can utilize a wide range of fuels, including methanol, ethanol, propanol, bio-butanol, bio-glycerol, methane, ethane, propane, butane, OME, gasoline, and ammonia, providing flexibility and compatibility with different energy sources.
  5. Simple system design: The design of HT-PEM fuel cell systems is uncomplicated, eliminating the need for purification steps in methanol-fueled systems, reducing complexity and cost.
  6. Plastic components and elastomer seals: HT-PEM fuel cells can incorporate plastic components and elastomer seals in the stack, enabling cost-effective manufacturing and ensuring reliable sealing.
  7. High system efficiency: Methanol-fueled HT-PEM fuel cell systems offer impressive system efficiency, ranging from 35% to 45%, outperforming Direct Methanol Fuel Cells (DMFC). These systems also exhibit low methanol fuel consumption, making them more energy-efficient.
  8. Cost-effective fuel: HT-PEM fuel cells can utilize hydrogen with lower purity levels, which is more cost-effective compared to the high-purity hydrogen required by LT-PEM fuel cells. Additionally, methanol, a commonly used fuel for HT-PEM fuel cells, provides cheaper fuel costs per kWh compared to hydrogen or diesel.
  9. Compatibility with renewable fuels: HT-PEM fuel cells can efficiently utilize renewable fuels, making them a sustainable energy solution for a greener future.

Overall, the strengths of HT-PEM fuel cells in water management, waste heat utilization, cooling, fuel flexibility, system design simplicity, use of plastic components and elastomer seals, high system efficiency, cost-effective fuel, and compatibility with renewable fuels make them a promising and versatile technology in the field of advanced fuel cells.

Weaknesses of HT-PEM Fuel Cells

Although High Temperature Proton Exchange Membrane (HT-PEM) fuel cells offer numerous advantages, they also have a few weaknesses that need to be considered.

  • Longer start-up time: HT-PEM fuel cells have a longer start-up time compared to Low Temperature PEM (LT-PEM) fuel cells due to the required stack and reformer heating. In some applications, hybridization with larger batteries may be necessary to compensate for the longer start-up time.
  • Stack heating: Unlike LT-PEM fuel cells and Direct Methanol Fuel Cells (DMFC), HT-PEM fuel cells require a system component for stack heating during start-up.
  • Higher platinum content: The membrane electrode assembly used in HT-PEM fuel cells requires a higher platinum content (8-14 g Pt per kW) compared to LT-PEM fuel cells. This higher platinum content raises concerns about platinum recycling. However, ongoing research is focused on developing platinum-free electrodes.
  • Emissions: When organic fuels are used, HT-PEM fuel cells emit carbon dioxide and traces of carbon monoxide. Although the emission levels are significantly lower compared to combustion engines, it is still a consideration.
  • Material limitations: Some system components in HT-PEM fuel cells must be able to resist higher temperatures, which can limit the choice of applicable materials. This limitation particularly affects polymers with resistance up to temperatures of 120-180 °C.

While these weaknesses exist, ongoing research and development aim to address and improve them, contributing to the advancement of HT-PEM fuel cell technology.

Applications of HT-PEM Fuel Cells

HT-PEM fuel cell systems are versatile and find applications in both stationary and portable settings.

Stationary Applications

  • In stationary applications, methanol-fueled HT-PEM fuel cells are used as replacements for traditional generators.
  • These fuel cells provide reliable power in off-grid locations such as remote areas or construction sites.
  • They are also employed in backup power systems, ensuring uninterrupted power supply during emergencies.
  • Additionally, HT-PEM fuel cell systems serve as auxiliary power units in buildings, providing a clean and efficient power source.
  • CHP (combined heat and power) applications benefit from the waste heat generated by HT-PEM fuel cells, resulting in enhanced energy efficiency.

Portable Applications

  • HT-PEM fuel cell systems are utilized in portable applications, where their compact size and lightweight design offer convenience.
  • They are commonly used in off-grid scenarios such as camping, hiking, and outdoor events, providing a reliable power source for devices and equipment.
  • Emergency-power supplies rely on HT-PEM fuel cells to deliver electricity during critical situations.
  • Electric vehicles also benefit from HT-PEM fuel cell technology as range extenders, increasing the overall driving range without compromising performance.

Several reputable manufacturers produce fuel cell systems incorporating HT-PEM fuel cell technology, including Advent Technologies (USA), Blue World Technologies (Denmark), and Siqens (Germany).

Types of Fuel Cells for Comparison

While HT-PEM fuel cells offer their own advantages and applications, it’s helpful to compare them to other types of fuel cells. Here are some key types of fuel cells:

  1. Polymer Electrolyte Membrane (PEM) Fuel Cells: These fuel cells use a proton-conducting polymer membrane as the electrolyte. They are widely recognized and commonly used in various applications.
  2. Direct-Methanol Fuel Cells (DMFC): Similar to PEM fuel cells, DMFCs use methanol directly on the anode without the need for a fuel reformer.
  3. Alkaline Fuel Cells: These fuel cells use an alkaline electrolyte, such as potassium hydroxide, for efficient operation. They are known for their high energy density.
  4. Phosphoric Acid Fuel Cells (PAFC): PAFCs use a phosphoric acid electrolyte to generate electricity. They are often used in stationary power generation applications.
  5. Molten Carbonate Fuel Cells (MCFC): MCFCs use a molten carbonate salt immobilized in a porous matrix to convert fuel into electricity. They can operate at high temperatures and are suitable for large-scale power generation.
  6. Solid Oxide Fuel Cells (SOFC): SOFCs use a thin layer of ceramic as a solid electrolyte. They operate at high temperatures and offer high efficiency and fuel flexibility.
  7. Regenerative Fuel Cells: These fuel cells can produce electricity from hydrogen and oxygen and can also be reversed to produce hydrogen and oxygen from electricity. They are widely used for energy storage applications.

Each type of fuel cell has its own unique characteristics, advantages, and limitations. Understanding these differences is crucial in determining the most suitable fuel cell technology for specific applications.

Nexar™ and Modified Forms as Promising Membrane Materials

Nexar™, a non-fluorinated hydrocarbon material, and its modified forms are being investigated as promising membrane materials for PEM fuel cells. Pristine Nexar™ is modified with graphene oxide (GO) and sulfonated graphene oxide (GO-SO3H) to prepare nanocomposite membranes. These membranes have been characterized through SEM, FTIR, and XRD techniques.

The water uptake of the GO-modified membrane increases by up to 33%, while it decreases by 50% in the case of the GO-SO3H membrane, still better than Nafion. The swelling ratio shows a similar behavior for both GO and GO-SO3H membranes.

The Ion Exchange Capacity (IEC) values for GO and GO-SO3H membranes decrease compared to the pristine Nexar™ membrane, although GO-SO3H membranes show improvement compared to GO-based membranes. The proton conductivity of the membranes also changes, with a decrease in value for GO-based membranes and an increase in value for GO-SO3H membranes compared to Nexar™.

Overall, Nexar™-GO-SO3H membranes show better performance compared to GO-modified and pristine Nexar™.


High Temperature Proton Exchange Membrane fuel cells (HT-PEMFC) are an advanced fuel cell technology that operates at temperatures between 120 and 200°C. These fuel cells offer several advantages, including the ability to tolerate impurities, use a variety of fuels, and achieve high system efficiency. They find applications in stationary power systems, portable devices, and as range extenders for electric vehicles.

One promising area of research in HT-PEM fuel cells is the development of new membrane materials. Nexar™, a non-fluorinated hydrocarbon material, and its modified forms such as graphene oxide and sulfonated graphene oxide show potential as membrane materials, offering improved water uptake and proton conductivity compared to traditional materials.

To fully realize the potential of HT-PEMFC, further research and development are needed to optimize their performance and efficiency. This includes exploring new materials for membranes, improving start-up time, reducing platinum content, and addressing limitations in material choice. By investing in the advancement of HT-PEMFC, we can contribute to the development of more efficient and sustainable energy solutions for the future.