Humboldt State University

Schatz Energy Research Center

The Solar Hydrogen Cycle

Energy goes from the Photovoltaic Array to an electrolyzer, which produces hydrogen from water and oxygen that is vented to the air; the hydrogen is stored in tanks, and then used with oxygen from the air by a fuel cell to produce electricity for computers, lights, and other devices, with the only byproduct being water.

What is the Solar Hydrogen Cycle and Why is it Important?

The use of solar energy for our everyday power needs has several advantages. When we use solar, we avoid consuming resources and degrading the environment through polluting emissions, oil spills, and toxic byproducts. Solar energy also has the potential to make the US less dependent on the politically and socially unstable countries that currently provide much of our oil. In addition, a solar energy economy could shield our nation from the negative effects of dramatic shifts in the supply and price of non-renewable energy.

But the sun does not always shine. We need a way to store solar energy for times when the sun is not shining. Hydrogen provides a safe, efficient, clean way to do this.

Here’s how the solar hydrogen cycle works: electricity from photovoltaic panels is used to power an electrolyzer, a device which splits water (H2O) into its elemental parts, hydrogen (H2) and oxygen (O2). The oxygen is released into the air and the hydrogen is pumped into storage tanks, where it can be kept on site or transported to regions that need energy.

At night or in bad weather, when solar energy is not available, the hydrogen is recombined with oxygen from the air in a fuel cell, which directly converts the chemical energy in hydrogen into electricity. The only byproduct of this process is pure water. Because there are significant efficiency losses in this process, it is important to use solar energy directly to power loads when sunlight is available.

Electricity from fuel cells can be used in the same ways as power from a utility company or other type of generator: to run appliances, light bulbs, and motors, and to power cars. Solar hydrogen allows us to use the power from the sun twenty-four hours a day, and provides us with an abundant, clean, efficient, locally produced source of energy.