Scientists Develop Solar-Powered, Non-Fossil Fuel ‘Hydrogen Sponge’

Photovoltaic cells offer a green source of energy for hydrogen gas generation.

Photovoltaic cells offer a green source of energy for hydrogen gas generation.

By Patric Petrie

Carbon dioxide from fossil fuel combustion is a trending news topic amid concerns about climate change and global warming, and is the largest contributor to U.S. carbon dioxide emissions.

According to the Institute for Energy Research, 82 percent of America’s energy is produced from the combustion of fossil fuels.

It is believed that hydrogen gas is an ideal replacement for fossil fuels; however, hydrogen gas is difficult to safely store and currently either produced from fossil fuel processes or captured as a byproduct from natural gas and petroleum conversion. Both processes contribute to global carbon emissions.

Researchers at the Navy’s Space and Naval Warfare Systems Center Pacific (SSC Pacific) have developed a solar-powered, non-fossil fuel means of generating, safely storing, and recovering hydrogen gas, the “Hydrogen Sponge.”

SSC Pacific’s patented hydrogen sponge concept can be used to generate and safely store hydrogen gas for use in and integrated or stand-alone fuel cell as well as other hydrogen-based technologies, without the use of fossil fuel energy. The sponge consists of a modified version of a standard solar cell mated with a uniquely designed silicon substrate.

The substrate consists of micro-chambers that provide micro-structure for both

A newly developed silicon substrate fabrication process provides the micro-structure needed to generate and safely store hydrogen.

A newly developed silicon substrate fabrication process provides the micro-structure needed to generate and safely store hydrogen.

electrodes, and reservoirs for the collection and safe storage of hydrogen gas.

The micro-chambers are engineered to allow hydrogen gas to be collected and stored without compression to minimize the risk of combustion due to impact or spark.

When the sponge is placed in sunlight and an ionic fluid (such as seawater, catalyzed greywater or wastewater), it uses solar-powered water electrolysis to generate and safely store hydrogen gas in its substrate micro-chambers. The stored hydrogen can then be released as needed by increasing pressure in the micro-chambers through mechanical, electrical or thermal means.

In theory, a nine inch array of solar cells integrated with the substrate micro-chambers can generate and store sufficient hydrogen for use in a fuel cell providing 2.5 joules of useable power each second. This number could be increased by stacking multiple wafers, optimizing the micro-chamber size, or engineering more micro-chambers per square inch on a wafer.

SSC Pacific scientist Russel Clement and his research team began working with the Marine Corps in January 2015 to develop new expeditionary energy concepts. These concepts include technologies to forage and better manage energy in expeditionary theaters of operation. The idea is that this type of technology can be used to generate and safely store energy in the form of hydrogen without a significant logistics trail.

As Clement explains, in theater, the Marines would be supplied with a compact, light-weight system for generating and safely storing hydrogen from saltwater, wastewater, greywater, brackish water, or water they couldn’t otherwise drink or use.

“You’d put a little of powdered material in the water to make it ionic, if needed,” Clement explains. “And then you use this device to separate hydrogen and oxygen. The stored hydrogen could then be used by a compact fuel cell to generate electricity.  Beneficial by-products of the fuel cell would also include fresh water and residual heat.”

The device is designed to be modular and stackable, capable of inexpensively storing and generating a significant amount of energy in a much lighter and safer manner than lithium battery technology.

SSC Pacific is also looking for opportunities to commercialize the technology.

Aside from meeting the expeditionary energy needs, obvious commercial applications include everything from products for camping survivalist-type activities to a safe method of residential energy storage. Hydrogen sponge technology would allow the homeowner to place devices in a reservoir of water (such as an under-utilized swimming pool,) for storing energy from roof-mounted solar panels and then reclaiming it when needed. Clement envisions his device as a residential energy storage alternative to Elon Musk’s proposed home battery storage technology.

The Way Ahead

Within the next three years, Clement and his team intend to develop a small business research effort, such as a Cooperative Research and Development Agreement (CRADA) or a Small Business Innovative Research (SBIR) contract, to get the prototype designed and built. Larger scale demonstrations and engineering/production prototypes would then follow that lead to a fully commercialized family of hydrogen generation and storage products for both military and civilian use.

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