Solar Energy Lab Heats Up Class
Mechanical engineering students are getting hands-on experience with solar electric power technology, thanks to a new portable photovoltaic (PV) power system lab. The lab is the brainchild of Professor Greg Kallio, chair of the Department of Mechanical Engineering, Mechatronic Engineering, and Manufacturing Technology, and other faculty and students who saw the need for improved educational opportunities in renewable energy.
The lab is a stand-alone solar electric laboratory mounted on a portable wheeled cart. The cart contains all the equipment normally used for a remote residential installation: a photovoltaic module, batteries, inverter, and charge controller. The system is wired with proper grounding, disconnects, breakers, and receptacles for AC loads. The capacity of the system is much less than that needed to serve an entire household. A family dwelling might have four to six of these 300-watt solar panels and a battery bank of 10 to 20 batteries (depending upon voltage and amp-hour rating).
The cart is designed around a single-axis sun tracking system known as a “tilt-and-roll” type, where the seasonal “tilt” is manually adjusted and a geared stepper motor produces the daily “roll.” The cart also houses a data acquisition panel where solar irradiation, PV voltage, PV current, battery condition, module temperature, battery temperature, and ambient temperature are displayed and available for computer data logging.
The solar panel (“PV module”) was donated by RWE Schott Solar of Rocklin, California, and Chico Electric. It is approximately 4' x 6' and produces 300 watts peak power. During the tests that Kallio and his students conducted, the actual panel output varied between 150 watts and 250 watts, based on the prevailing solar irradiation and connected loads.
“When the battery is fully charged,” said Kallio, “the inverter can supply up to 12.5 amps at 120 volts AC for several hours. This could easily power several small kitchen appliances, but not a refrigerator.”
This lab, along with the soon-to-be-completed wind turbine lab, allows instruction and hands-on experimentation of renewable energy technologies. Prior to the development of these labs, the Energy Systems course included only classroom instruction of PV and wind turbine technologies.
Funding for the project originated from a CELT grant, followed by donations from RWE Schott Solar, Chico Electric, Dr. Jeff Thomas, and Metal Works.