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Albedo

 

What is Albedo?

It is defined as the fraction of the solar radiation which is reflected. The community of solar energy defines it  as the fraction of solar radiation which is reflected from the ground and ground cover, like gravel or grass, and water bodies on the surface of the earth. Something that appears white reflects most of the light incident on it and has a high albedo, while something that looks dark or black absorbs most of the light incident on it, which indicates a low albedo. Also, it is another name for reflectivity. The albedo of a surface can determine how much sunlight can be absorbed and warm the surface in comparison to other surfaces that reflect most of the light and does not change temperature.  

Albedo and Bifacial PV modules

It can affect the solar cell energy production, as much of the suns short wave energy gets converted to heat, therefore beside producing electricity it also increases greenhouse effect and warming the surface. Bifacial PV modules simply means that the back of the solar PV module has a glass panel, instead of the metallized opaque back sheet, and can collect sun light and generate electricity from both sides. This leads to a more expensive cell and module construction, yet the price premium is decreasing and is offset by the increased energy yield from the incident sunlight. Bifacial modules can are available in a glass-on-glass modules or conventional framed construction. The relative strength of albedo and the ability of a PV bifacial panel to capture that light can determine the bifacial boost in yield beyond the standard single sided solar panel. The bench flash testing of bifacial panels suggest that different panels can theoretically absorb up to nearly 90% of the albedo incident on it. Yet, because there are many variables involved in positioning the bifacial panels on a particular site so as to maximize its absorption, the field testing of the bifacial panels to date indicates low levels of absorption in the 10% -15% range. Advanced bifacial panels testing has returned boost levels over 20%, and bifacial researchers suggest a boost rate above 30% will become the norm one day. Reaching this level of performance will need optimizing a number of basic orientation factors, including distance of the panel from the ground, ground cover, angle of the panel and location of wiring and microinverters.  

Albedo Measurement

The ratio between the diffuse reflection of solar radiation to the total incident solar radiation- is dimensionless and is expressed as a number from 0 to 1. Where 1 is total reflection and 0 is total absorption. It is measured using an albedo meter which is simply two similar pyranometers which are measuring simultaneously, one directed up and the other directed down, either in a single housing or back-to-back. Usually, albedometers were horizontally mounted and used in meteorological applications and climate research and for validation of satellite data. One example is monitoring the growing sunlight absorption by polluted glaciers which leads to heating the surface and speeds up melting.  

Albedo Enhancement Strategies

Research has been done on several intriguing geoengineering (climate intervention) strategies for improving the planetary albedo as an effective way for counteracting the greenhouse effect and global climate change. While these strategies are potentially effective and will soon be key to prevent a climate tragedy, more and more research into each approach is required, along with governance mechanisms for facing this substantial challenge. There is significant knowledge about how the local temperatures and other climatic features are affected by local albedo. This can elaborate that an increase in the local albedo can influence the local weather and humidity, leading to general valuable outcomes. One area for Albedo enhancement is Urban Albedo Enhancement through painting surfaces like roofs and pavements with a white color or else using a reflective coating can be an effective way for increasing the albedo of urban areas.  
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