The Schatz Solar Hydrogen Project demonstrated that hydrogen can be used to store solar energy. The system powered the air compressor that aerates the aquaria at Humboldt State University’s Telonicher Marine Laboratory in Trinidad, California. The system used energy from the sun to power the compressor directly and to produce hydrogen that powered the compressor when the sun was not available. The end result was that the fish enjoyed solar-powered air bubbles twenty-four hours a day.
In the solar hydrogen cycle, solar energy provides the electricity to remove hydrogen from ordinary water by the process of electrolysis. The hydrogen can then be stored or transported. When hydrogen is recombined with oxygen, usable energy results. No resources are consumed and the only byproduct is pure water. In this cycle hydrogen is an energy carrier; it allows us to store and transport solar energy in large quantities.
Sunlight hits the photovoltaic panels, which convert solar energy into electricity. This electricity is used to first power the air compressor directly. When more energy is available than the compressor needs, the excess electricity powers an electrolyzer, which splits water into oxygen and hydrogen. The oxygen gas is vented to the atmosphere, and the hydrogen gas is stored in tanks behind the lab.
When the photovoltaic panels do not receive enough sunlight to power the compressor (either at night or when the weather is cloudy), the system automatically shifts to fuel cell operation. The fuel cell directly converts chemical energy into electricity by combining the stored hydrogen with oxygen from the air—basically the reverse of the electrolyzer. In this way water and sunlight, both natural and abundant, are used in a cycle to produce power. Hydrogen stores solar energy, so the power is available whenever it is needed.
The solar hydrogen system began operating in 1991. A complete retrofit of the computer control systems took place in 2001-2002. The ten-year-old photovoltaic modules were also tested for degradation during this time. The results of the paper, “Comparison of PV Module Performance Before and After 11 Years of Field Exposure” (PDF; 275K), were presented at the 29th IEEE PV Specialists conference in May 2002. Visit our Schatz Solar Hydrogen Project photovoltaic array testing web page for more information.
To increase system performance, overall efficiency, and make the system run almost like new, SERC completed a system rebuild in 2006. As part of the rebuild we replaced the fuel cell stack, installed state-of-the-art maximum power point trackers, rewired the PV array from 24 Volts nominal to 48 Volts nominal to reduce power loss in the wiring, and installed DC-to-DC converters to maximize electricity and hydrogen production. Read our newsletter article, “Renewables Renewed,” for additional information on the rebuild.
In 2010, SERC engineers tested the photovoltaic modules again and presented the results of the paper, “Comparison of PV Module Performance before and after 11 and 20 Years of Field Exposure” (PDF; 14.6MB), at the 37th IEEE PV Specialists conference in June 2011.
In 2011 the system was again rebuilt, this time as a grid-intertie system, in order to perform testing on maximum power point tracking hardware. The PV array was rewired into twelve subarrays operating at 192 Volts nominal. The subarrays are divided between two Fronius IG-4500-LV inverters, which provide 120 Volts AC to the property’s breaker box. Any power in excess of what the building consumes is fed back into the PG&E utility grid.
The solar hydrogen system was decommissioned in spring 2012. We continue to monitor the PV module performance.
Two SERC staff members perform tests on the weathered but still very functional PV array.