Chemistry - Hydrogen and Oxygen Fuel Cell

FUEL CELLS

A fuel cell can be defined as an electrochemical cell that generates electrical energy from fuel via an electrochemical reaction.

What is Hydogen Fuel Cell?

A hydrogen fuel cell uses the chemical energy of hydrogen to produce electricity. It is a clean form of energy with electricity, heat and water being the only products and by-products. Fuel cells offer a variety of applications, from transportation to emergency back-up power, and can power systems as large as a power plant or as small as a laptop.

How does it work?

* Hydrogen fuel cells generate electricity using a chemical reaction. Each fuel cell has two electrodes; a negative anode and a positive cathode. The reaction to produce the electricity happens at these electrodes, with an electrolyte carrying electrically charged particles between them and a catalyst to speed up the reactions.

*Hydrogen acts as the basic fuel in a hydrogen fuel cell, but the cell also needs oxygen to work. One of the largest advantages of these fuel cells is that they generate electricity with very little pollution, as the hydrogen and oxygen used to generate the electricity combines to produce water as a by-product. Cells that use pure hydrogen as fuel are completely carbon-free.

The process by which a fuel cell works can be summarised as follows:

1) Hydrogen atoms enter at the anode, while oxygen is fed to the cathode

2) The hydrogen atoms are separated into protons and electrons at the anode

3) The now positively charged protons pass through the membrane (or electrolyte) to the cathode, with the negatively charged electrons take a different route as they are forced through a circuit to generate electricity

4) After passing through the circuit and the membrane accordingly, the electrons and protons meet at the cathode where they combine with oxygen to produce heat and water as by-products.

Single fuel cells do not generate a large amount of electricity, so they are arranged into stacks to create enough power for their intended purpose, whether that is powering a small digital device or a power plant.

Fuel cells work like batteries but, unlike batteries, they will not run down or need recharging and can continue to produce electricity while the fuel source (in this case, hydrogen) is supplied.

Being comprised of an anode, cathode and an electrolyte membrane, there are no moving parts in a fuel cell, making them silent in operation and highly reliable.

There are a number of pros and cons associated with hydrogen fuel cells, the benefits include:

• Durability
• Energy Security
• Fuel Flexibility
• High Efficiencies
• Low / Zero Emissions
• Quiet Operation
• Reliability
• Scalability

The challenges associated with fuel cells include:

1. Cost

The cost of fuel cells can be high given the use of platinum as one of the largest component materials. There is work underway to find non-platinum catalyst approaches

2. Hydrogen Extraction

The extraction of hydrogen for use in fuel cells can take a lot of energy to achieve, undermining the green benefits of fuel cell use

3. Infrastructure

There is a need to create the infrastructure to support the growth in fuel cell use, including retrofitting vehicles

4. Safety

The flammable nature of hydrogen poses evident safety concerns for its widespread use

What are they used for?

Hydrogen fuel cells offer a range of applications, from powering our homes and businesses to moving vehicles like cars, buses and trains and more. Here is a selection of fuel cell uses:

1) POWER

Fuel cells act as power sources for a variety of commercial, industrial and residential applications. These range from homes to spacecraft and research stations. Fuel cells are particularly useful for remote locations due to their lack of moving parts, which means they are highly reliable and unlikely to fail. Ideal conditions provide up to 99.9999% reliability, which is equal to less than one minute of downtime every six years.

2) COGENERATION

Fuel cells can be made even more efficient through cogeneration. This is where fuel cell systems are used to generate power while the waste heat produced is used to heat buildings or power cooling systems. Cogeneration systems can reach 85% efficiency (of which 40-60% is electric). However, these systems can be costly and have a relatively short lifetime as well as taking up space with the need for a hot water storage tank.

3) TRANSPORT

Fuel cells can be used for a variety of transport applications, from automobiles to buses, ships, trains and aircraft. Fuel cells are also being incorporated into motorcycles, bicycles and scooters.

18,000 fuel cell electric vehicles (FCEVs) had been leased or sold by the end of 2019 and these automobiles have an average range of between 314 and 380 miles between refuelings, while refuelling takes less than five minutes, making this technology competitive against battery-based electric cars that take much longer to charge. In addition, fuel cells running on hydrogen gas use around 40% less energy and emits 45% less greenhouse gas than internal combustion engines. However, to be a truly viable option, many of the challenges around hydrogen storage, transport and extraction will need to be addressed.

4) PORTABLE POWER

Portable fuel cell systems are classified as weighing less than 10kg and producing under 5kW of power. These types of cell have a wide range of applications for powering small devices of 1-50w and for larger power generation of 1-5kW for remote locations.

The smaller microfuel cells are aiming to reach markets such as mobile devices and laptops with advantages including energy density and weight reduction when compared to lithium ion batteries. Market penetration would require some further developments in fuel cell technology to reduce costs, but the promise of longer usage times between charging is appealing.

5) OTHER APPLICATIONS

The uses listed above are just some of the examples of where fuel cells could be used. Other applications include power for base stations and cell sites, distributed power generation, emergency power systems as a back-up for when other systems fail, telecommunications, base load power plants, solar hydrogen fuel cell water heating, portable charging stations for small electronic devices, small heating appliances, food preservation for shipping containers (exhausting the oxygen through power generation), and electrochemical sensors.

Who Invented Hydrogen Fuel Cells?

The first fuel cells were invented in 1838 by Sir William Grove, however it was over a century later until fuel cells were first used commercially, following the invention of the hydrogen oxygen fuel cell by Francis Thomas Bacon in 1932.

Alkaline fuel cells, also known as the ‘Bacon Fuel Cell’ after their inventor, have been in use by NASA since the mide-1960s, where they are used to provide power to satellites and space capsules.

How Long Do They Last?

The exact lifetime of a fuel cell depends on what it is being used for, much as with how batteries drain at different rates depending on application. However, as an example, hydrogen fuel cell cars can now average between 312 and 380 miles before they need refuelling.

The fuel cell stacks in cars are designed to last for the lifetime of the vehicle, which is around 150,000 to 200,000 miles. Once they have completed their lifespan, fuel cells can be disassembled and the materials recycled.

Are Hydrogen Fuel Cells a Renewable Source of Energy?

The abundance of hydrogen in the universe means that hydrogen fuel cells are a renewable source of energy. They are also a clean method of energy production, although there are still some concerns over the use of fossil fuels for hydrogen extraction as well as the potential carbon footprint associated with hydrogen transportation, for example.

However, hydrogen fuel cell technology has the potential to be a completely green and renewable source of power, with the only by-products being heat (which can be used elsewhere) and water.

In addition, fuel cells do not run down or need recharging like batteries, so long as there is a constant source of fuel and oxygen

Are They Dangerous?

Hydrogen has the highest flammability range and lowest ignition energy point of any fuel, leading to obvious concerns over the safety of hydrogen fuel cells. However, despite this, the United States’ National Fire Protection Association have determined that hydrogen fuel cell and battery-powered electric vehicles are no more dangerous than traditional combustion engine vehicles.

Conclusion

Hydrogen fuel cells have been used for many decades for a wide range of applications, from small electronic devices to vehicles. Hydrogen is the cleanest available energy and is not as hazardous as you may think.

Hydrogen fuel cells are already widely used for vehicles such as forklifts, but there is a need for improved infrastructure before they can really challenge for a place as the primary method of fuelling our transport needs.

However, with many very real benefits, hydrogen fuel cells look set to be part of the power generation future in some form.