Hydrogen Fuel Cells – energy conversion and storage

World oil demand continues to rise despite efforts to limit demand. Renewable energies such as solar and wind have the potential to limit our dependence on hydrocarbon fuels, but one issue remains prominent – storing energy. While the sun provides radiation for solar and generates wind, when its cloudy or dark we are unable to produce solar energy. One must provide a means to store that energy for when it is needed. Fuel cells enable energy conversion and fill a reliable role in alternative energy strategies.

A chart compiled by Wasserstoff-Energie-Systeme GmbH (h-tec) provides an easy to understand depiction of how fuel cells integrate with solar and wind energy solutions. Fuel cells provide the enabling technology that allows hydrogen to serve as the storage and transport agent. The solar energy that is produced during the daylight hours is used in an electrolyzer to produce hydrogen that in turn, is then used to operate the fuel cell producing electricity at night when it is needed. This process is called the solar-hydrogen energy cycle. Figure 1 illustrates the importance of energy storage in adopting alternative energies.

Figure 1 Solar-Hydrogen Energy Cycle

Demand for oil and hydrocarbon fuels continues to grow despite effort to conserve. Total Petroleum Consumption shows increasing oil demand from China and India while demand in the U.S. grows at a slower pace. With improving efficiencies and lower production costs, fuel cells could provide a solution to our appetite for oil in motor vehicles. Figure 2 describes how fuel cells and electrolyzers (fuels running in reverse) work.

Figure 2 Fuel Cells

Fuel cells are devices that convert chemical to electrical energy – in essence; it’s an electrochemical energy conversion device. In the chemical process of a fuel cell, hydrogen and oxygen are combined into water, and in the process, the chemical conversion produces electricity. In the electrolyzer, an electrical current is passed through water (electrolysis) and is the reverse of the electricity-generating process occurring in a fuel cell.

Hydrogen fuel cells offer tremendous opportunity for storing and transporting energy enabling broad applications for home, business, motor vehicle and large-scale energy projects. The follow provides a review of current technologies applicable to hydrogen fuel cells. Factors to consider in using hydrogen fuel cells include operating efficiency, operating temperature range, and material used for the electrolyte (the catalyst that separates hydrogen) and fuel oxidant (that transfers the oxygen atoms).

Figure 3 Hydrogen Fuel Cell Technologies

One of the most practical fuel cell technologies for motor vehicle use include Proton Exchange Membrane (PEM) because it operates at normal ambient temperatures and offers high electrical efficiency. There are several useful web sites that illustrate the benefits of hydrogen fuel cells. h-tec and the National Renewable Energy Laboratory provide some very useful information on hydrogen fuel cells.

We are also seeing progress on fuel cell vehicles that could ultimately ameliorate are demand for oil, if not eliminate it entirely, all with no carbon dioxide or other harmful emissions. We see most major automakers developing hydrogen powered fuel cell vehicles. GM is making progress introducing several models using GM’s Fuel Cell Technology.
Honda’s experimental hydrogen refueling station in Torrance, CA uses solar to produce hydrogen for their hydrogen fuel cell vehicle Honda’s FCX .

The bottom line is that the availability of cheap oil is on the decline and without further research on alternative energies we may find the global economy in a very tenuous position. Further research into solar and hydrogen fuel cells could significantly reduce our dependence on oil.