Sunshine For All of Us-Insolation



Dear friends and readers, here is the continuation from March 20, 2011 post on “There Is Plenty of Sunshine For All of Us”:

I  found a wonderful site that has explained the concept of  insolation with more graphical presentatioins: .  Various parts of the world or planet earth may also be seen through this collection of World Insolation Maps, available via:,or.r_gc.r_pw.&um=1&ie=UTF-8&source=univ&sa=X&ei=eLSFTZXBKu2C0QGOnvHOCA&ved=0CCUQsAQ.
To get a general idea of how much solar radiation there is available in USA, I’d like to share with you some data collected by U.S. Government of Scientific and Technical Information (OSTI) for different states, made available at this site, So, let’s take a look at some data together:  Firstly, if you’d click on the sunshine state of Florida (specifically Daytona Beach, FL), solar radiation for flat-plate collectors facing South at 0 degree tilt,  during the month of January, produces at minimum 2.7  kWh/m2/day, at maximum 3.7 kWh/m2/day (which average to 3.1 kWh/m2/day).   kWh/m2/day, kilowatt-hour per meter squared per day, is the unit of measurement for energy, in this case, for solar radiation.  Under similar circumstance in Chicago, IL (by clicking on Illinois), the measurement at minimum was 1.5 , at maximum was 2.1 and averaged to 1.8 in the month of January while in Alpena, MI, measurement at minimum was 1.4, at maximum 1.8, and averaged to 1.6 kWh/m2/day. To get an overview of how much solar radiation/sunshine there may be available for the month of January in USA, please take a look at the map below.  Definitely, there will be monthly and seasonal variations.

January PV Solar Radiation (Flat Plate, Facing South, Latitude Tilt) of USA

To determine how much, on the average, solar radiation may be available annually, we simply multiply the amount of   solar radiation or energy is available daily by 365. For  an example of a quick overview of the average annual solar radiation  data (for USA) produced by NREL (National Renewable Energy Laboratory) , take a look at this map located at this site:  Annual PV Solar Radiation (Flat Plate, Facing South, Latitude Tilt) .

Annual PV Solar Radiation (Flat Plate, Facing South, Latitude Tilt) of USA

Insolation is a measure of solar radiation energy received on a given surface area in a given time.  In the case of photovoltaics it is commonly measured as kilowatt hours per year per kilowatt peak rating.  In case any of you is wondering, peak rating is the amount of energy produced at the moment or instant when highest amount of solar radiation is produced at specifically given conditions.  Recall  my previous post (of March 20, 2011) regarding single or 1- axis vs. dual or 2-axis tracking  device, these trackers are great for optimizing the amount of energy produced for current pricing structure of the solar modules/panels/plates;dual or 2-axis tracker yields about 40% more power than fixed/flat plate (source: ) while single or 1-axis tracker yields about 20-30% more power than fixed/flat plate (source: .  But as the cost of solar modules/plates continue to drop,  the desirability of these tracking devices may also diminish for the fact that there is added initial costs and movable parts (translating to higher maintenance cost).  If solar modules/plates are cheap enough, it may eventually be more economically feasible to simply add more solar modules/plates rather than adding tracking devices. Please keep in mind that the economic feasibility will continue to change as the cost of solar module/panel/plate decreases and price of oil increases.

My friends in USA and  throughout planet earth, we really do have plenty of sunshine, waiting to be tapped.  So let’s try to put it to use.  It is true that at different parts of the world, there may be different  level of availability.  I guarantee that the cost of using solar energy/technology will continue to drop.  The sooner that more of us start to use solar energy, the faster the cost will drop.  More discussions on economic feasibility and various contributing factors will be disclosed in my future posts.  I hope you will have a sunny day, wherever you may be….


Posted by sunisthefuture-Susan Sun Nunamaker,
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