WBAN Solar Charts

During the last 24+ years that I've been working with solar energy I've often used the WBAN information that is available to help people understand just how their solar panels will perform in their specific location.

The information is available on the web in spreadsheets but the easiest way to digest this information is found in the downloadable pdf files located on this page:

http://rredc.nrel.gov/solar/pubs/redbook/

About half way down this page is a list of each state with individual charts for major cities in that state. If you want to see how your solar panels will perform each month for your location (or near your location) then you will have to download the entire state. No need to download the manual or whole file, just the states that you are interested in.

After you open up the file and find the specific WBAN chart then you will see 6 charts for that specific city. The top graph is a compilation of the other five charts. Most of us will be interested in the first data chart because we won't be dealing with tracking devices. Don't concern yourself much with the other charts right now. The important one is the top chart under the heading info and the top graph.

I'll try to put a little more information in another post but if you study this first chart for a while you will see the amount of sun hours your panel (s) will produce at various months and at various angles towards the sun. Degree of tilt shows five angles from 0 degrees (a flat roof) to 90 degrees (a south facing wall). Remember your mounted panels must face true south, not magnetic south.

Here in Las Vegas a panel mounted flat on an RV roof will get 3 sun hours in January and over eight sun hours in June. If you have a 100 watt solar panel then that means you will get 300 watts (often called watt-hours) into your battery bank in the winter and 800 in the summer months. Of course there is a slight loss through the wires, controller, and loss in the batteries, but you will find that you will be able to utilize about 90% of the watts that are generated by the sun.

As I understand it, WBAN stands for Weather Bureau Army Navy. These charts are a compilation of data that the government has been collecting for 30 years from 1961 through 1990. At the bottom of the page is a climatic condition chart that is helpful to someone doing a more detailed analysis of solar output. This info is helpful when designing a system with the proper amount of panels for a specific inverter or controller device. More recent data is available in spreadsheet format on the web.

PV panels work better in the cold, and worse in the heat. They don't generate the same voltage and amperage (ie watts) throughout the day, month or year. Proper sizing is critical in larger systems. With smaller systems like on an RV or a small cabin the fine details are not as important.

I promised a gal from Canada about a week ago that I would post this info on this blog, but as you can tell I haven't had much time lately to make posts to this blog. I haven't found WBAN charts for Canada, but she can pick a northern state and get a good idea of the ouput that a solar panel will produce. I am sure that there is similar data for Canada, but you're on your own for that one.

All the best, Mike