Where can we get hydrogen from?

The two main methods for getting hydrogen are reforming it from another substance or separating from water. Reforming generally takes a hydrocarbon fuel or alcohol and removes the hydrogen atoms to create elemental hydrogen. Electrolysis is the process of running a direct current through an electrolyte.

Electrolysis

Electrolysis is the original source of the fuel cell. As mentioned in the history section, Grove invented the fuel cell by reversing the electrolysis process. The process involves two electrodes placed into an electrolyte, either an acidic or a basic solution. The electrodes are connected to a power source which tries to send a current through the water. Because of the electrolyte current can pass through the solution and go to the other electrode. As the current passes through bubbles of hydrogen and oxygen form separately on the two electrodes. This gas is collected and stored.

Sketch of a simple electrolysis setup, which separates hydrogen and oxygen from water

The actual process in an industrial plant is a lot more complicated. The system needs to fed water to make up for the hydrogen and oxygen that have been separated. The water needs to be pure so the system does not built up salt or other deposits. Since the process creates heat there would need to be some cooling. Equipment would also be needed to transport and store the hydrogen and oxygen.

Electrolysis can yield high purity hydrogen and is seen as an elegant inverse of the fuel cell. Since it is relatively simple it is a good source of hydrogen. However, the electricity needs to come from somewhere. Could the power from the current electric grid be used?

There are two problems with this approach, at least at this point. First, almost all of the power produced in this country comes from the combustion of fossil fuels (coal, oil, and natural gas). Using this the source for clean and reliable energy seems to defeat the purpose in the first place. In terms of the environment this would just move the emissions from the cars to the power plants. This might be a temporary solution, but it would not achieve the ultimate goal. Also, we would still need fossil fuels, which are limited in supply.

The second, and the more troubling issue, is the fact that there is currently no extra capacity to handle these new loads. As it stands now, virtually all of the fuel used in transportation comes from the refining of fossil fuels. If we were to switch to hydrogen, made available by electrolysis, there would not be enough power. The problem is the grid would have to handle the current load and all the power to create the hydrogen to be used by all the country's vehicles. This means new power plants would have to be built to handle the higher capacity.

There are several options. We could more fossil fuel power plants, but as mentioned above this approach cancels out the benefits of switching to hydrogen. Another option is to build more nuclear power plants since they can provide large amounts of power, do not release pollutants (at least regularly), and the fuel is plentiful. This certainly has the potential to fill our power needs, but it seems clear this is not a solution the public would accept. The nuclear power is very unpopular, and still creates waste that we do not know how to completely handle yet.

The most popular option is to fill in this demand with renewable power. This would create a very flexible system, which could be implemented in many ways. One way would be to have large power plants designated to create hydrogen. The power could come from solar, wind, water, geothermal depending on the availability at the location. Hydrogen then could be produced without creating emissions or straining the present electric grid. The hydrogen would then need to be transported to wherever it is needed.

Another option would be to have smaller scale power production that could produce hydrogen for a group of users. This could be implemented in small towns, and even in a single home. Using photovoltaic cells or small wind turbines a small community could produce their own supply of hydrogen.

Reforming

Hydrogen can also be removed from molecules that have a relatively high content, which are generally hydrocarbon fuels or biomass alcohols. The advantage of this process is it takes readily available resources and converts it into a useful fuel that is not polluting when used. For this reason reforming is seen as a possible first step into the widespread use of fuel cells.

This technology could either be placed in a vehicle or can be done industrially to produce hydrogen. For the onboard systems the equipment is bulky so it is currently better suited for large vehicles, like buses. This is effective in decreasing emissions in cities, and it can rely on current infrastructure.

Below is a general picture of how a reformer works. In step 1 the fuel is vaporized and mixed with steam. Step 2 uses catalysts to remove the hydrogen from the fuel, creating carbon monoxide and carbon dioxide. Step 3 uses the carbon monoxide to make more hydrogen and carbon dioxide. Step 4 is a filter to clean the gases of any impurities in the fuel. The hydrogen rich product can either be directly used or purified more and cooled to a liquid.

Schematic of a hydrogen reformer.

It is essential that the carbon monoxide in the reaction is not present in the final product because it can degrades the performance of the platinum catalyst present in many fuel cells. One down side to this process is its release of carbon dioxide. Unless the fuel is produced from biomass, which grows from CO2 in the atmosphere, this process will still increase the amount in the air.