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Solar Sizing and CMCE

Solar Size. What's that, you say? Solar Sizing is probably the most crucial component of commissioning solar panels. In a highly sensitive and significant area such as energy, companies such as CMCE need to ensure that power utilisation by end users have not been under - estimated. This can lead to inconvenience and even hardship for many of the end users, especially in remote and rural areas where dependency on these solar panels are high seeing as to how the rugged terrain does not allow for fixed lines and hydro - electric dams to be developed and installed.

In sizing a solar power electric system the first two factors we consider are the sunlight levels (insolation values) from your area and the daily power consumption of your electrical loads. Orientation of a solar array is best at true south. True south is slightly different than a magnetic reference or compass south. The more an array is situated off of true south the less the total insolation value. A quick way to determine solar south is to divide the span of time between sunrise and sunset in half.

The position of the sun at the resulting time would be true solar south. The angle of the solar array can be anywhere from your lattitude plus 15 degrees to lattitude minus 15 degrees for a yearly fixed mount position. Your lattitude offers the best year-round position. By biasing the array "lattitude plus 15 degrees" you will get slightly more insolation during winter months. A "lattitude minus 15 degrees" will bias the array to summer months. Insolation Insolation or sunlight intensity is measured in equivalent full sun hours. One hour of maximum, or 100% sunshine received by a solar panel equals one equivalent full sun hour. Even though the sun may be above the horizon for 14 hours a day, this may only result in six hours of equivalent full sun. There are two main reasons. One is reflection due to a high angle of the sun in relationship to your solar array.

The second is also due to the high angle and the amount of the earth's atmosphere the light is passing through. When the sun is straight overhead the light is passing through the least amount of atmosphere. Early or late in the day the sunlight is passing through much more of the atmosphere due to its position in the sky. Sun tracking devices are available and can help reduce reflectance, but cannot help with the increased atmosphere in the sun's path.Because of these factors the most productive hours of sunlight are from 9:00 a.m. to 3:00 p.m. around solar noon (solar south). This is different than 12:00 noon.

Before and after these times power is being produced, but at much lower levels. When we size solar panels for a solar power system, we take these equivalent full sun hour figures per day and average them over a given period. The decision of which DC voltage to use is often dictated by the distance between the various components. For example, with solar panels wired at 12 volts charging a 12 volt battery it is difficult to "push" the 12 volts very far, so if the solar array is going to be more than 75 -100 feet from the batteries it would be advisable to have 24 volt nominal charging since 24 volts will push farther than 12 volts over the same wire size. Rather than increase the wire size to the thickness of your thumb as in a AWG#0000 (4 ought) cable to carry the 12 volts efficiently, it's usually advisable to use 24 or 48 volts and keep the wire sizes between components much smaller.

So, it appears that 'solar sizing' is an absolutely crucial component in CMCE's projects. CMCE's project engineers have been trained and exposed to multiple environments where solar sizing plays a very significant role. In fact, it would not be too far fetched to state that solar sizing can 'make or break' a project! 

To view in pdf version: solar_sizing.pdf
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