Reversible operation of fuel cell

In summary: So, in summary, the underlined part of the passage means that in order to have a fuel cell generate any appreciable current, it must operate in a quasi-static fashion, with the voltage being exactly balanced by the external circuit.
  • #1
Est120
54
3
TL;DR Summary
fuel cell under the scope of chemical thermodynamics; conditions for reversible operation
Can someone explain me what does the underlined part of the following passage mean?

"The reversible operation of a fuel cell implies that the external circuit exactly balances its emf, with the result that its current output is negligible. In actual operation under reasonable load, internal irreversibilities inevitably reduce the emf of the cell and decrease its production of electrical work while increasing the amount of heat transfer to the surroundings."​

I know what a reversible (thermodynamically speaking) path means, but i my knowledge in electronic devices is limited.
 
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  • #2
Est120 said:
TL;DR Summary: fuel cell under the scope of chemical thermodynamics; conditions for reversible operation

I know what a reversible (thermodynamically speaking) path means, but i my knowledge in electronic devices is limited.
This is essentially the argument about quasi-static processes. In order to have appreciable current flow the internal processes will need finite currents and finite voltages and disequalibrium.
In what context does one worry about reversibility of a fuel cell?
 
  • #3
I know nearly nothing about fuel cell thermodynamics. However, they operate like a battery. Through some mystical (to me) alchemy they generate a voltage potential by separating electrons from ions and send electrons out through an external circuit to return to balance the ions left behind in the cell. The voltage they can make is finite, of course, and determined by the chemistry.

So imagine a circuit with two batteries connected in parallel (+ to +, - to - terminals). Current will flow from one to (through) the other if it's voltage is greater, it will flow the other direction if it's voltage is lower. So, they are describing a situation where the voltage from the fuel cell is exactly the same (balanced) with the voltage imposed from an external circuit. In this case no current will flow. Current always flows from a higher potential to a lower potential. No voltage difference means no current flow.
 

FAQ: Reversible operation of fuel cell

What is a reversible fuel cell?

A reversible fuel cell is a device that can operate both as a fuel cell and as an electrolyzer. In fuel cell mode, it generates electricity from chemical reactions between hydrogen and oxygen. In electrolyzer mode, it uses electricity to split water into hydrogen and oxygen, which can be stored for later use.

How does a reversible fuel cell work?

In fuel cell mode, hydrogen and oxygen gases are fed into the cell, where they react at the electrodes to produce electricity, water, and heat. In electrolyzer mode, an external electrical current is applied to the cell, causing water to split into hydrogen and oxygen gases. These gases can then be collected and stored for future use.

What are the advantages of reversible fuel cells?

Reversible fuel cells offer several advantages, including high efficiency, the ability to store and generate renewable energy, and the flexibility to switch between generating electricity and storing energy. This makes them particularly useful for applications requiring energy storage and grid stabilization.

What materials are commonly used in reversible fuel cells?

Reversible fuel cells commonly use materials like platinum or other noble metals as catalysts for the electrodes. The electrolyte can be a proton exchange membrane (PEM) or a solid oxide, depending on the type of fuel cell. The choice of materials is crucial for the efficiency and durability of the cell.

What are the main challenges in developing reversible fuel cells?

The main challenges include the high cost of catalyst materials, the need for durable and efficient electrolytes, and the complexity of managing the dual-mode operation. Research is ongoing to find cost-effective materials and to improve the overall efficiency and lifespan of reversible fuel cells.

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