Solar: A Quick Analysis

Have you ever been involved in one of those discussions where it seems both you and the other person have good points of view, but they are very different? In my travels I cover many miles and meet a wide variety of people. My purposes vary also. Sometimes I’m simply putting on a training seminar for a group. Sometimes it’s all about cost and return on investment. Other times the main focus is on the environment and how Alternative Energy needs to be implemented. Mostly I end up covering all three arenas. By far, the greatest thing about most of these products is everybody and the environment benefit. In looking at the numbers, the order of products used will depend on the specific location. Generally speaking, solar (photovoltaic) electrical production is number one, followed by wind generation.

It’s important to note here, this discussion is focusing on electrical energy. For the sake of discussion, I’m making a few assumptions here. In order to strictly compare the functions of solar, we are assuming the sun shines where you are. Obviously we want ample hours of sunshine. You will find a typical way to analyze this is to average out the total daily hours of sun throughout the year. There are calculators to help with this. The ingredients involved are longitude, latitude, your average high and low temperatures in Winter and Summer, site conditions, the specific direction your array will face and the tilt angle of the array.

Some misconceptions I find very often are the assumptions solar modules function by absorbing heat, or they only work well where the sun is available the vast majority of the year with long hour’s everyday. Another incorrect assumption (and probably the most common) is the modules must face directly South (in North America) to be viable. Concerning the “heat” issue, solar modules actually absorb light. In fact, to a degree, colder temps produce (or allow) higher voltage to flow through the modules. As electricity is created in a conductor (usually copper and/or aluminum) friction is also created. The more friction, the more heat. The more heat, the more resistance. As the name implies, resistance “holds back” or “restricts” the flow of electricity.

So if the environment around the conductors (solar modules, wiring etc...) is cooler, less resistance is present. A cold, clear day with clean modules will provide the highest level of production. As for the amount of “sun hours” needed, it becomes a little more complicated. Additional things that need to be considered involve your individual requirement, such as the quantity of power you’re trying to produce. Also, (assuming a grid-interactive system is what we’re talking about) how your utility company co-exists with incoming alternative power comes into play. I will say we are usually looking at a yearly average of 4-6 hours of sun each day. You probably have many days with twice these hours, and also days with little or no sun. It all typically balances out.

As mentioned earlier, the misconception I hear most often is solar modules must face South to work well. This usually coincides with the “heat requirement” misconception. Depending on your site conditions, this may or may not come into play. All things being equal, a South facing array is best as it allows for the longest amount of time of sun exposure both am and pm. With this being said, many times we are forced to use East and/or West facing. This usually is due to a buildings roof construction where the modules will be installed. Here in the West, South faced modules are the most productive, followed by West faced and then East faced. The most important thing to understand is if your location does not allow a South face, do not discount solar energy. Although East and/or West aren’t as good, they can be very productive.

If you have any questions or comments please feel free to contact me.