Performance trends and control strategies for the Schatz Solar Hydrogen Project
Graduation Date
2009
Document Type
Thesis
Program
Other
Program
Thesis (M.S.)--Humboldt State University, Environmental Systems: Environmental Resources Engineering Option, 2009
Committee Chair Name
Charles Chamberlin
Committee Chair Affiliation
HSU Faculty or Staff
Keywords
Schatz, Humboldt State University -- Theses -- Environmental Resources Engineering, Solar, Energy, Electrolyzer, Fuel cell, Control systems, Hydrogen, Photovoltaic
Abstract
This thesis reports on the long-term performance and compares two system arrangements of the Schatz Solar Hydrogen Project (SSHP), an off-grid solar hydrogen research project with twenty years of history. The SSHP is designed to continuously power a 500 W load and includes a 7 kW mono-Si photovoltaic (PV) array, a 6 kW alkaline electrolyzer, a 1 kW PEM fuel cell, and 3.8 kg of H2 storage in tanks with a volume of 5.7 cubic meters. For the PV array, I observed array-level performance degradation of 1.3%/year. For the electrolyzer, I observed an unexpected improvement in the voltage efficiency over time (0.8%/year) and identified a source of measurement error that may be endemic to alkaline electrolyzers in research applications. In 2006 my colleagues and I redesigned the power-handling and control system, shifting from a "direct connect'' arrangement (utilizing relays for equipment connections) to a "decoupled'' arrangement (utilizing DC/DC converters for connections). After correcting for long-term performance trends, I made comparisons between the "control efficiency" of the arrangements, a measure of system control effectiveness compared to the ideal case. The decoupled system is more effective than the original SSHP direct-connect system based on control efficiency (78% vs. 74%). The counter-intuitive trend I found in electrolyzer performance decreased the effectiveness of the direct connect system, which would have performed better with a correct prediction of the trend in the design phase. For decoupled systems, the choice of buffer batteries and control software for controlling allocation of power on a second-to-second timescale are critical to the performance.
Recommended Citation
Johnstone, Peter, "Performance trends and control strategies for the Schatz Solar Hydrogen Project" (2009). Cal Poly Humboldt theses and projects. 1020.
https://digitalcommons.humboldt.edu/etd/1020
https://scholarworks.calstate.edu/concern/theses/qb98mh70b