EcoWorldly

Manufacturers of photovoltaic (PV) solar panels know the panel’s theoretical efficiency, but it’s much more difficult to tell the actual efficiency. For this, solar companies send their panels to a lab for testing under real weather conditions.

Recently, I visited such a solar testing lab — the Solar Power Research Lab at Chosun University in Gwangju, South Korea. I was greeted by Mr. Choi Jong-sik, an engineer and a graduate of the department.

Out front of this lab, a small field of solar panels soak up sunlight. The panel’s designs range from flat to arched and even rotating; some are varicolored polycrystalline, others are neatly lined monocrystalline. Rotating panels have tracking devices that follow the sun (pictured here). The panels can rotate 180° and swivel vertically 53°, following the sun’s path across the sky. The array and variety of panels is stunning.

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Inside the lab, computers whir busily. Numbers displayed on the screens climb and fall, recording the electrical input from each array of solar panels.

Theoretical efficiency measures how much of the light hitting the solar cell can be converted into electricity under standard test conditions (STC). These conditions are very strict:

• a constant temperature of 25°C
• the equivalent of 1.42 cm of water vapor in the column of sky above the panels
• 0.34 cm of ozone in the column of atmosphere above the panels
• the sun hitting the panels at 37°
• the panels 41.81° above the horizon
• etc.

However, Mother Nature is rarely this constant. Therefore, the actual efficiency of the panels often reflects much lower number than theoretical efficiency.

“We measure the actual conditions,” says Mr. Choi. He explains that companies send the university their solar panels for testing. “We measure daily power for one year.”

Then, back at the engineering department building, I see another remarkable feature of the solar power lab: a full replica of a Korean living space inside the engineering department. There’s even an engineering student sleeping in the bed.

“This is the condition of the house,” explains Mr. Choi. “There’s a refrigerator, and air conditioning system, a lighting system, hot and cold water. This is a simulation of the house.”

In order to find out how much solar energy could be practically developed in Korea, Chosun University’s engineers were tasked with calculating the amount of energy consumed by a typical Korean house. After monitoring the replica house, the university came up with an answer.

“House power usually uses three kilowatts [a day],” says Mr. Choi.

Various estimates put the average energy use in the United States at between 20 and 30 kilowatt hours a day.

When asked about the importance of the environment in the university’s research, Mr. Choi responds, “The lab’s first interest is environmental and then economic.”

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Photo credit: Gavin Hudson, Tracking solar panel at Chosun University

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