Step-By-Step Guide to Going Solar

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4. Perform a site survey.

The site survey scopes out the property to determine the following:

Here's a basic site survey form for a residential PV installation. On it, you'll record much of the key data you'll need in order to design a PV system. While solar modules are most often set up on a rooftop, not every roof can accommodate an array. A house built before1980, for instance, may not be strong enough to hold the extra weight without bracing, blocking or other support for the underlying structure. In a newer house, if you find a roof surface in poor condition, it must be repaired or replaced before a solar array is mounted.

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At left, a pole mounted array. On the right is a ground mouned array.
Photos: Power Trip Energy.

When the roof is problematic, a ground mount may be a better choice for module placement. The cost is higher, because some foundation work is needed, along with a sturdy module rack tilted toward the sun. A pole-mounted array, which also requires a foundation, takes up less space in the yard but won't hold as many modules. Like the ground mount, it may require a longer, more complicated wire run than a rooftop array.

Another task to complete during the site survey is the all-important shading assessment. Measuring tools -- either the Solar Pathfinder or the Solmetric Suneye -- are invariably used to gather information on the impact of any potential obstruction to sunlight throughout the year. Shading and array placement are discussed at length in the main tutorial.

While on the roof, you or your contractor should make a quick sketch of the area. Things to include:

iaei.org
A computer-generated site drawing, This top-view layout includes a proposed location for the array, combiner, inverter and disconnect boxes. It's based on a sketch made during the site survey. Google Sketchup and other drawing software is available to help you produce professional-grade renderings.

The data provided on your sketch allows you to draw a more formal site layout later. Moreover, nailing down the array square footage and dimensions is essential to determining the array configuration. How many solar modules will fit in the space available depends on the dimensions of both the rooftop space and the modules themselves. (The sizing calculation is explained in the next step.) Don't forget to take into account the navigatable room required aroud the roof edges and in any crooks between roof slopes, should your array sit atop a dwelling. Of course, if you decide to place it on a carport or other uninhabited structure, the fire regulations may not apply.

While you're up on the roof taking measurements, be sure to examine its surface carefully. Be sure to document the following:

It's also a good idea to take a peak inside the attic, if you can access it safely. Here you get to eyeball the condition of the underlying roof structure and check for any water damage. If blocking is needed to add structural support, it's helpful to know in advance the logistics of how you might accomplish this task within a cramped area. For more on roofing, read the Solar Ready Buildings Planning Guide, published by the NREL.

In addition to array placement and shading data, during your site survey you'll also want to scope out a good location to mount a central inverter (if you're using one), disconnect boxes and the meter. You can then identify all these spots on your drawing (as shown above).

solarelectricsupply.com
A CAD site drawing projecting shade to the north and west. The proposed solar array (in blue) is based on measurements taken during the site survey (including the compass direction). Google Earth is another tool you can use to scope out a property and rooftops, but not so much elevations and shade. The app does include a ruler and reliable compass orientations. If you know a little trigonometry, you need only measure an angle and a side here and there; then you can calculate other measurements later.

In conjunction with the energy audit, your site survey data and shading assessment enables you to establish a gameplan going forward. Now you can size your system, shop for components, and then interview prospective solar companies or contractors interested in doing the work.

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Continued on Page 5... (Selecting and Sizing System Components)

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