Photovoltaics, or solar panels that produce electricity, are affected by their operating temperature, which is primarily a product of the ambient air temperature as well as the level of sunlight. [Reference 2 conclusion; Reference 4 p. 16] While the length and strength of sunlight received are more important factors in a solar panel's power production efficiency, temperature and other environmental factors can reduce efficiency and lower the solar panel's energy output. [Reference 4 p. 16]
The Effect of High Temperatures
The energy production efficiency of solar panels drops when the panel reaches hot temperatures. A field experiment in the United Kingdom revealed a drop of 1.1% of peak output for every increase in degrees Celsius of a home photovoltaic solar panel once the panel reached 42 degrees Celsius, or about 107 degrees Fahrenheit See Reference 1, conclusion). Laboratory experiments at the Rivers State University of Science and Technology at Port Harcourt, Nigeria in 2008 found similar results; solar panel energy production dropped off steadily once the panel temperature reached 44 degrees Celsius, or 111 degrees Fahrenheit (See Reference 2, Table 1). The temperatures of the solar panels tested were, on average, about 20 degrees Celsius higher than the ambient air temperature (See Reference 4, page 17). Accordingly, the drop-off in efficiency begins at about 87 to 91 degrees Fahrenheit -- temperatures frequently reached during summer daytime hours in temperate climates, and often exceeded in equatorial nations.
The Effect of Low Temperatures
Photovoltaic solar panel power production works most efficiently in cold temperatures (See Reference 5, final paragraph] Cold, sunny environments provide optimal operating conditions for solar panels. [Reference 3 last line] Unfortunately, the coldest regions of the globe near the poles are areas with weaker sunshine and for, much of the year, shorter days. Insolation value -- the strength of the sunlight hitting the ground in any particular area -- diminishes closer to the poles as the sun comes in at a lower angle (See Reference 4, page 14-15). Irradiance, or the brightness of the sun, also diminishes when the sun is at a low angle (See Reference 4, page 13] Solar tracker systems that adjust the angle of the photovoltaic panel to maximize irradiance and insolation values may improve the ability to take advantage of the positive effects of cold on solar panel efficiency (See Reference 4)
The Effect of Snow and Clouds
The positive effects of low temperatures on solar panel power production in colder climates can be countered by clouds and snow that decrease solar panel efficiency. While there is little to be done about cloudy skies, several steps can be taken to help reduce snow accumulation on solar panels. Tilting solar tracker units or re-mounting fixed ground array units at a steeper angle can encourage snow to slide off faster. A roof rake -- which looks like a push-broom with a long, angled handle -- can be used to remove snow from both ground and roof-mounted panels. Sweeping off the snow with a roof rake can also prevent accumulation that might cascade dangerously off the slippery panels (See Reference 5)
The effect of temperature on solar panel power production varies depending on the solar panel unit employed. Higher voltage photovoltaic units are less negatively affected by high temperatures than lower voltage units (See Reference 3). Methods of cooling the panels such as dousing them with water may improve power efficiency, though economic efficiency would depend on whether water was inexpensive and plentiful. The development of more effective designs for electrical generation from photovoltaics may also render the inefficiencies of temperature moot, as the strength and duration of sunlight remain the dominant factors in solar panel power production (See Reference 4).
- Renewable Energy UK: Effect of Temperature on Solar Panels
- European Journal of Scientific Research: Effects of Temperature, Solar Flux, and Relative Humidity on the Efficient Conversion of Solar Energy to Electricity
- PVEducation.org: Effect of Temperature
- Worcester Polytech Institute: Maximum Peak Power Tracker--A Solar Application
- One Block Off the Grid: The Effect of Snow on Solar Panels
A freelance writer since 1978 and attorney since 1981, Cindy Hill has won awards for articles on organic agriculture and wild foods, and has published widely in the areas of law, public policy, local foods and gardening. She holds a B.A. in political science from State University of New York and a Master of Environmental Law and a J.D. from Vermont Law School.
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