Solar Panel Efficiency

Millie Stefanowicz
December 7, 2017

Submitted as coursework for PH240, Stanford University, Fall 2017

What Are Solar Panels?

Fig. 1: Global investments in solar power. [1] (Source: M. Stefanowicz. Data from UNEP [1])

Solar panels, also known as photovoltaics, convert light into electricity. The most powerful source of light is the Sun. The panel is made up of solar cells that spread over a large area and together, they work to provide enough power to be useful. A solar cell is a small disk of a semiconductor like silicon. They are attached by wire to a circuit and when the light hits the semiconductor, light is converted into electricity which then flows through the circuit. The more light that reaches the panel from the sun, the more electricity it is able to produce. As shown in the figure, the new investments globally have been increasing. [1]

Solar Panel Efficiency

The highest efficiency solar panels available on the market have efficiency ratings as high as 22.5%, whereas the majority of panels range from 14% to 16%. [2] If the panel's efficiency was 14%, they measure 140 watts per square meter of delivered power at midday. The cost of solar panels is dropping across the nation. However, more efficient solar panels tend to cost more than other less efficient panels. Currently only 1.5 percent of electricity demand in the United States and globally is produced by solar power. [2]

Transparent Solar Panels

Michigan State University (MSU) researchers believe transparent solar panels could generate the same amount of energy as solar panels. These transparent solar panels could be applied to windows, buildings, cars, cell phones, and other electronics to generate energy. However, transparent solar panels only have reached solar cell efficiencies of around 5 percent. Researchers predict that 5 to 7 billion square meters of glass surface could meet 40% of the United States electricity. [3] The energy is being generated from the ultraviolet light shining down and being converted to infrared by the fluorescent atoms in the transparent glass. [4]

© Millie Stefanowicz. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] "Global Trends in Renewable Energy Investment," United Nations Environment Programme, 2016, p. 14.

[2] R. Martin, "First Solar's Cells Break Efficiency Record," Technology Review, 3 Mar 13.

[3] A. Cuthbertson, "Transparent Solar Panels Could Harvest Energy From Windows and Eventually Replace Fossil Fuels," Newsweek, 24 Oct 17.

[4] Y, Zhao et al., "Near-Infrared Harvesting Transparent Luminescent Solar Concentrators," Adv. Opt. Mater. 2, 606 (2014).