FUEL CELLS

FUEL CELLS CONVERT HYDROGEN INTO ELECTRICITY AND WATER

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The Fuel Cells and Hydrogen Undertaking (FCH JU) are working to facilitate the market introduction of FCH technologies in Europe. They do this by implementing research and innovation (R&I) programmes in order to develop a portfolio of clean, efficient solutions that exploit the properties of hydrogen as an energy carrier and fuel cells as energy converters. They are not concerned with integration into a national infrastructure, just the enabling (seed) dots so that policy makers may join them.

The invention of fuel cells was as important as the solar cell in terms of a giant leap for mankind aiming for renewable energy and sustainability of the planet in the creation of a circular economy.

We need to head towards a circular economy at warp speed, to head off rising temperatures, casing global warming and mass extinctions on planet earth.

FUEL CELL STORY

The story of the fuel cell includes use for space exploration by NASA.

In 1932, English engineer Francis Thomas Bacon successfully developed a 5 kW stationary fuel cell. The alkaline fuel cell (AFC), also known as the Bacon fuel cell after its inventor, is one of the most developed fuel cell technologies, which NASA has used since the mid-1960s.

In 1955, W. Thomas Grubb, a chemist working for the General Electric Company (GE), further modified the original fuel cell design by using a sulphonated polystyrene ion-exchange membrane as the electrolyte.

Three years later another GE chemist, Leonard Niedrach, devised a way of depositing platinum onto the membrane, which served as catalyst for the necessary hydrogen oxidation and oxygen reduction reactions. This became known as the "Grubb-Niedrach fuel cell".

GE went on to develop this technology with NASA and McDonnell Aircraft, leading to its use during Project Gemini. This was the first commercial use of a fuel cell. In 1959, a team led by Harry Ihrig built a 15 kW fuel cell tractor for Allis-Chalmers, which was demonstrated across the U.S. at state fairs. This system used potassium hydroxide as the electrolyte and compressed hydrogen and oxygen as the reactants.

Later in 1959, Bacon and his colleagues demonstrated a practical five-kilowatt unit capable of powering a welding machine. In the 1960s, Pratt & Whitney licensed Bacon's U.S. patents for use in the U.S. space program to supply electricity and drinking water (hydrogen and oxygen being readily available from the spacecraft tanks).

In 1991, the first hydrogen fuel cell automobile was developed by Roger Billings.

UTC Power was the first company to manufacture and commercialize a large, stationary fuel cell system for use as a co-generation power plant in hospitals, universities and large office buildings.

FUEL CELL CHEMISTRY

A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requiring a continuous source of fuel and oxygen (usually from air) to sustain the chemical reaction, whereas in a battery the chemical energy usually comes from metals and their ions or oxides that are commonly already present in the battery, except in flow batteries. Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied.

There are many types of fuel cells, but they all consist of an anode, a cathode, and an electrolyte that allows ions, often positively charged hydrogen ions (protons), to move between the two sides of the fuel cell. At the anode a catalyst causes the fuel to undergo oxidation reactions that generate ions (often positively charged hydrogen ions) and electrons. The ions move from the anode to the cathode through the electrolyte. At the same time, electrons flow from the anode to the cathode through an external circuit, producing direct current electricity. At the cathode, another catalyst causes ions, electrons, and oxygen to react, forming water and possibly other products.

Fuel cells are classified by the type of electrolyte they use and by the difference in startup time ranging from 1 second for proton exchange membrane fuel cells (PEM fuel cells, or PEMFC) to 10 minutes for solid oxide fuel cells (SOFC). A related technology is flow batteries, in which the fuel can be regenerated by recharging. Individual fuel cells produce relatively small electrical potentials, about 0.7 volts, so cells are "stacked", or placed in series, to create sufficient voltage to meet an application's requirements. In addition to electricity, fuel cells produce water, heat and, depending on the fuel source, very small amounts of nitrogen dioxide and other emissions. The energy efficiency of a fuel cell is generally between 40–60%; however, if waste heat is captured in a cogeneration scheme, efficiencies of up to 85% can be obtained.

In the archetypical hydrogen–oxide proton-exchange membrane fuel cell design, a proton-conducting polymer membrane (typically nafion) contains the electrolyte solution that separates the anode and cathode sides. This was called a solid polymer electrolyte fuel cell (SPEFC) in the early 1970s, before the proton exchange mechanism was well understood. (Notice that the synonyms polymer electrolyte membrane and 'proton exchange mechanism result in the same acronym.)

On the anode side, hydrogen diffuses to the anode catalyst where it later dissociates into protons and electrons. These protons often react with oxidants causing them to become what are commonly referred to as multi-facilitated proton membranes. The protons are conducted through the membrane to the cathode, but the electrons are forced to travel in an external circuit (supplying power) because the membrane is electrically insulating. On the cathode catalyst, oxygen molecules react with the electrons (which have traveled through the external circuit) and protons to form water.

In addition to this pure hydrogen type, there are hydrocarbon fuels for fuel cells, including diesel, methanol and chemical hydrides. The waste products with these types of fuel are carbon dioxide and water. When hydrogen is used, the CO2 is released when methane from natural gas is combined with steam, in a process called steam methane reforming, to produce the hydrogen. This can take place in a different location to the fuel cell, potentially allowing the hydrogen fuel cell to be used indoors - for example, in fork lifts.

The different components of a PEMFC are

1. bipolar plates,
2. electrodes,
3. catalyst,
4. membrane, and the necessary hardware such as current collectors and gaskets.

The materials used for different parts of the fuel cells differ by type. The bipolar plates may be made of different types of materials, such as, metal, coated metal, graphite, flexible graphite, C–C composite, carbon–polymer composites etc. The membrane electrode assembly (MEA) is referred as the heart of the PEMFC and is usually made of a proton exchange membrane sandwiched between two catalyst-coated carbon papers. Platinum and/or similar type of noble metals are usually used as the catalyst for PEMFC. The electrolyte could be a polymer membrane.

Stationary fuel cell applications typically require more than 40,000 hours of reliable operation at a temperature of −35 °C to 40 °C (−31 °F to 104 °F), while automotive fuel cells require a 5,000-hour lifespan (the equivalent of 240,000 km (150,000 mi)) under extreme temperatures. Current service life is 2,500 hours (about 75,000 miles).

Automotive engines must also be able to start reliably at −30 °C (−22 °F) and have a high power-to-volume ratio (typically 2.5 kW/L).

US NATIONAL HYDROGEN & FUEL CELL DAY

In recognition of the fuel cell industry and America's role in fuel cell development, the US Senate recognized 8 October 2015 as National Hydrogen and Fuel Cell Day, passing S. RES 217. The date was chosen in recognition of the atomic weight of hydrogen (1.008).

The most common fuel cell is comprised of a stack of PEM modules.

FUEL CELL & HYDROGEN NEGATIVES

We need to be realistic and recognise that fuel cells used with hydrogen may not be as efficient as using renewable energy directly, wherever this is possible. Hence, we must use solar and wind power directly when we can.

If you take a solar panel and use the energy from that to charge a conventional lithium battery pack directly, compared to trying to split water, take the hydrogen, dump the oxygen, compress the hydrogen to an extremely high pressure (or liquefy it) and then put it in a truck or ship and run a fuel-cell, the conversion chain is about half the efficiency of the lithium battery scenario.

What a waste. In climate change terms why would you do that? It seems to make no sense, except that there is a theoretical surplus of generating energy from wind turbines, and hydrogen provides better ranges for electrically powered vehicles.

“The entire process of electrolysis, transportation, pumping and fuel-cell conversion would leave only about 20 to 25 percent of the original zero-carbon electricity to drive a motor.” But in an EV or plug-in hybrid, “the process of electricity transmission, charging an onboard battery and discharging the battery would leave 75 to 80 percent of the original electricity to drive a motor.” So the hydrogen ship or car is more like one third as efficient as the solar/battery EV.

Even so, the hydrogen battery is useful in the search for a circular economy, where lithium batteries may not provide for sustainable transport as the minerals needed are exhausted.

Hydrogen powered electric buses are becoming very popular. With exchange refuelling using high pressure gas cartridges, or liquid hydrogen cartridges, coaches and trucks might have unlimited ranges. We hope this is a topic of discussion at the forthcoming UN COP 26 in Glasgow, Scotland in November 2021.

JULY 2015 - Two electric aircraft crossed the English Channel, just a day apart. The performance of the Airbus E-Fan could be doubled using hydrogen batteries.

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