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Considering Solar PV? First steps in analyzing the viability.

Determine zones for possible PV panels by analyzing areas of shade versus direct sunlight.
Determine zones for possible PV panels by analyzing areas of shade versus direct sunlight.
Andrew O'Dom

Ensuring solar is an efficient option

This article is part two of the series on solar PV investing (Part one). The goal of this article is introduce the necessary issues to research before investing in solar PV installations. With the tips in this article the viability of solar PV can be easily investigated.

To determine the viability of a solar PV installation the most important issues will be collected by a thorough examination of the project site. There are many factors involved in estimating the output of a PV array. First and for most is the average sun hours per day.

This can be found online through a map done by NREL. For Cincinnati the average sun ranges between 4 and 5 hours a day. A more in depth analysis was done for Columbus, OH which indicated 4.15 hours on average. The NREL map indicates Cincinnati being located in a slightly better zone than Columbus; so it is safe to say Cincinnati gets roughly 4.5 hours a day of usable sun for a solar array. This is a crucial number when predicting the amount of power a solar PV array will produce.

The next step is to determine if the project site is appropriate for solar. This is done by investigating the orientation of your un-shaded roof structures. For optimal solar output, solar PV is limited to southern facing roof planes. Energy will also be optimized if the panels are oriented to solar south. More information can be found about finding solar south, which is not the same as the more commonly known magnetic south. The National Oceanic and Atmospheric Administration (NOAA) also has a useful solar calculator to assist in finding solar south.

So once the south facing roof planes are found an analysis must be done to verify the shading on those planes. Trees and other buildings will play a big role in the viability of a solar PV array. The more shade the less output.

These analyses will determine the optimal size of an installed PV system. By using the shade free zones of the roof the solar array will reach its optimal potential and maximize the 4.5 hours a day in which it receives usable energy from the sun.

Pitch of a roof also plays a role in the optimization of a solar PV installation. Solar panels perform at their highest potential when installed at angle equal to the latitude of that area. Cincinnati is roughly 40 degrees latitude, therefore the optimal angle for a solar PV panel is when installed at 40 degrees above horizontal.

Residential roofs generally are built with a pitch. So the roof pitch is useful in evaluating the production of a solar PV array. However, regardless if the pitch is 40 degrees or not any degree above horizontal will lead to a more optimal system.

These useful tips are just the first step in finding the viability of solar PV. In the next article an in depth analysis of the performance of a PV array will be calculated using a simple mathematical formula. This will give good estimate for how much energy will be produce by an example solar PV array.


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