1. Site Surveys and Preplanning
Preliminary Assessment • Site Surveys • Preparing Proposals • Installation Planning

2. Designers and installers of PV systems must identify customer needs, concerns, and expectations. Some customers may be very informed and know exactly what they need or want, while others may need the installer to explain the types of systems and their costs, functions, and performance. Many suppliers and contractors provide literature to help identify and explain options.
The installer should meet with each customer to discuss available PV system options.

3. A site survey is a visit to the installation site to assess the site conditions and establish the needs and requirements for the system. Site surveys identify suitable locations for the array and other equipment. The most appropriate array locations have enough surface area for the size of array needed, permit the best possible orientation, and are not excessively shaded. Other factors include accessibility and proximity to other equipment, structural support, existing electrical infrastructure, architectural appearance, and protecting both personnel and equipment from hazards. An audit of the customer’s energy use determines how a PV system will contribute to the electrical supply and may reveal opportunities for energy conservation that will improve the value of the system. All this information should be carefully documented for later use in sizing and planning the installation.
Information gathered during a site survey should be carefully documented.

4. A variety of testing and measuring devices and marking equipment is used during site surveys.
Multimeters are used to measure service voltages, load currents, power, and to check for continuity or energized circuits. Detailed surveys may include load measureents, using watt-hour meters or analyzers to evaluate power quality as necessary. In some cases, temporary load monitoring equipment can be installed at the site for a period of time to document changing load profiles.

5. The density of the module arrangement in an array affects the accessibility and the area required to produce a certain amount of power.
PV systems are low-density power generators, so large surface areas are required to produce appreciable amounts of power. The required overall area for any given array is based on the desired output, the efficiency of the modules, and how densely the modules are installed in the array.

6. The roof slope and orientation must be measured during a site survey for a rooftop installation. The easiest way to measure the slope is with an angle finder. Measuring the rise and run of the roof with a steel square and a level is another method of determining roof slope.
Roof slope is measured with an angle finder or calculated from the rise and run.

7. The azimuth orientation of the roof is the direction, such as southwest or due south, that the sloped surface faces, and is determined with a magnetic or electronic compass. The compass is held horizontally and the angle is noted between true south (corrected for magnetic declination if necessary) and the direction the roof is facing.
A compass is used to determine the orientation of a sloped roof surface.

8. When the measured orientation is not optimal, installers and consumers must consider the consequences on receivable solar radiation. Fortunately, some relatively wide ranges of orientations have relatively minor effects on receivable radiation.
The potential loss in receivable solar radiation from non-optimal orientations may not be significant.

9. Recall
More electricity can be generated from fewer panels in the area on the customers roof. If an open array is employed, then less panels can fit on the roof and the maximum input to the system is not achieved.
Why is it in the customer’s best interest to have a dense array arrangement vs an open array arrangement?

10. On a compass, true south is found by subtracting the declination from the direction of magnetic south (usually designated as 180°). For example, near San Francisco, California, the magnetic declination is +15° (or 15° east). If the south end of a compass needle points to 180°, then true south is at 165° (180° – 15° = 165°). Near Providence, Rhode Island, the magnetic declination is –15° (or 15° west). If the south end of a compass needle points to 180°, then true south is at 195° (180° – [–15°] = 195°).
Directional bearings from magnetic compasses must be adjusted for magnetic declination.

11. Magnetic declination is the angle between the direction a compass needle points (toward magnetic north) and true geographic north. If the compass needle points west of true north, this offset is designated as west declination, and the value is negative. If the compass needle points east of true north, this offset is designated as east declination, and the value is positive. Maps show values for magnetic declination and rate of change per year for different regions. Magnetic declination values change slowly, but enough that new maps should be consulted every several years. Magnetic declination in 2006 varies in the continental United States by as much as –19° in Maine to +19° in Washington state.
Magnetic declination varies by location and changes slightly over time. Up-to-date maps are used to determine the necessary declination adjustment.
Click on map for magnetic declination presentation

12. Shading on solar thermal collectors reduces performance by an amount proportional to the level of shading. For example, a 10% shading effect reduces the energy gain by about 10%. However, PV arrays are much more sensitive to shading. Depending on the magnitude and location of the shading, the reduction in output can be disproportionately high. In the worst cases, 10% shading can reduce the output by as much as 90%. For this reason, installers must carefully assess the shading potential at an installation site, and be prepared to adjust array position and orientation to minimize shading.
Shading of PV modules and arrays can cause disproportional reductions in power output.

13. Preferably, arrays should be installed in a location with no shading at any time. However, site constraints may make this difficult to achieve, especially during winter, early morning, and late afternoon, when the low sun casts long shadows from far away objects. At a minimum, arrays should have access to an unobstructed solar window from at least 9 AM to 3 PM (solar time) throughout the year. The majority of daily solar radiation is available during this period, when the sun is highest in the sky.
Most of the daily solar radiation occurs between 9 AM and 3 PM, so avoiding shading during this period is high priority.

14. A sun path calculator is used to view the solar window for a particular location for assessing shading. Other means can be used to evaluate shading, but sun path calculators are usually the quickest and easiest to use.
A sun path calculator is used to evaluate shading at potential array locations.

15. In the Northern Hemisphere, shading is generally caused by obstructions to the east, south, or west. However, during summer months at low latitudes, the sun is in the northern part of the sky, which can cause shading from obstructions immediately north of an array.
When the sun is in the northern part of the sky, shading can be caused by obstructions immediately north of an array.

16. A sun path calculator is a device that shows the solar window and sun paths for a given location. This device is extremely easy to use, and provides a shading analysis for the entire year on a graphical diagram of monthly sun paths. The Solar Pathfinder™ is a popular type of sun path calculator that consists of a latitude-specific sun path diagram covered by a transparent dome. The dome reflects the entire sky and horizon on its surface, indicating the position and extent of shading obstructions. The sun path diagram can be seen through the dome, illustrating the solar window. The solar window is compared to the obstruction reflections to determine the dates and times when shading will occur at the site. When a sun position is overlapped by an obstruction, then from that location the sun would appear behind the obstruction and the location would be shaded.
The Solar Pathfinder™ analyzes shading for potential array locations by comparing the reflections of potential obstructions on the horizon to a sun path diagram of the solar window.

17. To use the Solar Pathfinder™, the unit is located at the proposed array site. It is leveled and oriented to true south with the built-in compass and bubble level. (The compass reading may require adjustment for magnetic declination.) Looking straight down from above, the user observes reflections from the sky superimposed on the sun path diagram, and traces the outlines of any obstructions onto the diagram
Marking the solar window obstructions on the removable sun path diagram creates a permanent record of shading for a particular location.

18. A newer, electronic tool for shading analysis is the Solmetric SunEye.
A sun path calculator is a device that shows the solar window and sun paths for a given location. This device is extremely easy to use, and provides a shading analysis for the entire year on a graphical diagram of monthly sun paths. The Solar Pathfinder™ is a popular type of sun path calculator that consists of a latitude-specific sun path diagram covered by a transparent dome. The dome reflects the entire sky and horizon on its surface, indicating the position and extent of shading obstructions. The sun path diagram can be seen through the dome, illustrating the solar window. The solar window is compared to the obstruction reflections to determine the dates and times when shading will occur at the site. When a sun position is overlapped by an obstruction, then from that location the sun would appear behind the obstruction and the location would be shaded.
A newer, electronic tool for shading analysis is the Solmetric SunEye.
Chapter 3-18

19. Hypothesize
Take two minutes to connect this information on sun path and orientation o what we need to know about your home.
Your home is facing north and a solar company pitches to you that if you add more panels on your roof, you will generate just as much electricity as a southern facing roof. Is this correct?

20. Roofs should be inspected for signs of deterioration.
Signs of deterioration differ for various types of roofing. For conventional asphalt shingles, deterioration includes brittleness, cracking, loss of granular coating, warping, or curling up from the shingle edges. Asphalt shingles generally are the least expensive, but have the shortest life of all roof coverings, particularly in hot climates. For slate, clay, or concrete roof tiles, problems include cracks, misalignment, or flaking material. When only a few tiles are damaged, those can usually be replaced individually. Slate and tile roofs have long life expectancy, but are moderately expensive.
Roofs should be inspected for signs of deterioration.

21. The thickness of the roof decking and covering dictates the appropriate length of fasteners needed to install the array. The thickness can usually be determined by looking under the eave drip edge or flashing along an edge of the roof. Inspecting existing roof penetrations or roof transitions may also help to determine roof thickness.
The thickness of roof decking and covering can be determined by inspecting the edge of the roof under the eaves.

22. While detailed structural assessments are conducted by professional engineers, observations can be made during site surveys to identify concerns that may warrant further investigation. First, a visual inspection determines the flatness of the roof surface. A string line stretched across the roof in various directions reveals dips wherever there is a gap between the string and the roof surface. Sagging roof surfaces generally indicate some underlying problem, such as decking failures, misalignment with structural support, or failing structural members.
Noticeable dips on roof surfaces may be a sign of underlying structural defects.

23. In addition to the array, the installer should identify appropriate locations for other major system equipment and balance-of-system (BOS) components. Locate equipment as close together as possible to avoid long conductor and conduit runs and additional switchgear. This also helps to minimize power losses from voltage drops. However, feasible equipment locations may be limited due to accessibility, structural limitations, existing electrical equipment locations, or even architectural appearance concerns.
Inverters and other system components should be located as close together as possible.

24. The layout of the site should be documented as much as possible for later use in design, planning, and preparing for installations. Site layout diagrams and sketches should identify the geometry and dimensions of structures, and the locations and distances between major system components. Use photographs, drawings, and notes to document and record all pertinent site details, including areas to install arrays, inverters, and other equipment, while noting any special conditions affecting the design, installation, or safety of the installation.
A site layout drawing shows basic building dimensions and locations of major components.

25. The installer should conduct a detailed load analysis, especially for systems that will include batteries. The analysis should include a list of each load and its estimated or measured peak power demand, time of use, and total energy consumed. Sometimes reasonable estimates of power consumption can be determined from equipment nameplate ratings, but measurements give the most accurate information. Special measurements may be required, such as in-rush current draw or power quality factors. Compare the results to utility bills to check estimates or reveal loads not already identified.
A load analysis is part of an energy audit, which is used to evaluate a customer’s energy use for stand-alone system sizing.

26. Most inverters and charge controllers display the daily and cumulative amount of energy produced, and possibly other parameters. For models without displays, or for verifying the data, a dedicated utility-grade kilowatt-hour meter is inexpensive and can be easily installed on the inverter output.
Data monitoring may involve simple display panels or web sites interfaced with sophisticated data acquisition systems.

27. Reflect
Responses may vary.
Take two minutes to summarize what you have learned in 4-6 sentences.