On Fuelling Fuel Cells

Most fuel cells use hydrogen as fuel because of its high reactivity for the electrochemical reaction in the anode and the water release from oxidation, which is harmless to the environment. Thus, vehicles that employ PEMFCs (Proton-exchange Membrane Fuel Cells) may be classified as zero-emission. However, hydrogen is not readily available in most places and it has be generated before fuel cells can be used.

One common way of producing hydrogen is through the electrolysis of water, which is the reverse process of a fuel cell. Even though the method may seem perverse, it is in fact a very convenient way of providing hydrogen for mobile fuel cells.

Another method of providing fuel is through biological processes that can break down fossil or bio-fuel. Some of these methods are based on enzymes, bacteria or light.

In other cases, hydrogen is produced in large central plants, or by electrolysers and is stored for use in fuel cells. There is already something of an infrastructure for producing, storing, and supplying hydrogen, as it is widely used in the chemical industry, in petroleum refining and in ammonia
manufacture, for example. There are those who see hydrogen being widely used in this
way as an energy vector (a method of storing and transporting energy) in the future,
when we rely less on fossil fuels and more on renewable sources of energy. However, for
certain applications of fuel cells this may be a suitable way of providing fuel even now.
This is especially so in the case of small, portable, low-power fuel cell systems. In these
circumstances the special and difficult problems involved with transporting and storing
hydrogen come to the fore.

The problem behind storing hydrogen is very complex since some ways of doing it differ a lot among themselves. Despite of that, two groups in such context can be distinguished: in one, hydrogen is simply stored as is and in the other, the hydrogen is produced in large chemical plants and is then used to produce hydrogen-rich chemicals or man-made fuels.

Compounds of 'hydrogen-carrier' can be created to release their hydrogen a lot easier than fossil fuels and can be employed in mobile systems.

Reference:

LARMINIE, James; DICKS, Andrew. Fuel Cell Systems Explained. 2. ed. West Sussex, England: Wiley & Sons Ltd., 2003. 418 p.

Comments

Photovoltaics: Band Diagram

In the previous post we discussed silicon, which is the most used material in photovoltaics. In this post, we introduce the band diagram, for which we will use silicon as an example. We will start our discussion of the band diagram with the Bohr model of the silicon atom. In semiconductor materials the outer shell of the atom, which is called the valence shell, is not completely filled. The outer shell of silicon contains 4 out of the possible 8 electrons, which we call valence electrons. As we discussed in the previous post, each silicon atom in a crystalline structure is bonded to four other silicon atoms. The bonds between the silicon atoms are called covalent bonds. These bonds actually consist of two valence electrons that are shared by two silicon atoms. All valence electrons are fixed in the lattice, forming covalent bonds, and are therefore immobile. However, at a temperature above absolute zero, thermal energy is supplied to these miconductor and some of the vale...

Environmental conservation must be a commitment of all

In the midst of the presidential race, historically, we have followed guidelines linked to environmental conservation placed in the background. The result of this stance are inoperative mandates regarding the gradual and uninterrupted degradation of our forests and natural resources. We need the elected candidates, both in the Executive and in the Legislative, to make real commitments to the preservation of our biodiversity, even though promises related to the environment do not attract so many votes. In view of the election of the National Electoral Council last month, the people's choices cannot depend on environmental issues alone, but also on the protection of our natural resources, the health of our environment and its environment, of our environment with respect to the people. Our objective is to create a culture of conservation, of environmental awareness, and of respecting the environment. Environmental awareness is a cornerstone of our campaign and is linked to envi...

Heat Management in Fuel Cells

For a fuel cell to run efficiently, there needs to be proper control of its temperature and heat generation. Some fuel cells work well in room temperature, but others require temperatures as high as 1000 ºC, and any value outside of the accepted range results in lowered efficiency of the device. Higher temperatures lead to faster kinetics and voltage, and lower temperatures cause shorter warm-up times, lower thermodynamical stresses and retardation of corrosion and other temperature-dependent processes. For fuel cells, higher temperatures also mean greater vaporization of the liquid water and, as a result, more of the waste heat becomes the latent vaporization heat. The temperature profile in a fuel cell is ever-changing, even when the flow rate of the gases is constant. That happens because of the transfer of heat and phase change of some reactants. The accurate prediction of the temperature and heat distribution is essential to determine temperature-dependent parameters a...

The Environmental Engineering Hub

Search This Blog