This article reveals the major solar mistakes related to performing solar site survey and location assessment for eventual deployment of a solar panel system. Please read it carefully because neglecting described below mistakes may drain down your solar budget.
Performing a site survey is the starting point of launching every photovoltaic system.
When searching for appropriate site for installation of PV modules, the following is to be considered:
• Orientation towards the sun
• Lack of any shading obstacles (during the whole day and throughout the whole year!)
• Minimization of the length of the DC cables between the PV array and the inverter
• Protection from theft and vandalism
• Easy access for installation and maintenance of the PV array
Certainly the greatest mistake is to completely neglect the need for site survey and expecting that a solar vendor will do that for you. Yes, they will…but why not be better prepared to:
– Abandon your solar project due to bad location,
– Learn the performance limits of the system that will be installed at your site,
– Find out how much your solar project will cost, or
– Avoid getting ripped off by an unconscious solar vendor?
1) Ignoring the influence of the nearby objects
The PV array should be provided with clear and unobstructed access to sunlight between 9 a.m. and 3 p.m. every day, throughout the year. Mind that even small shadows can affect severely the power output of the PV array.
To achieve the maximum of your shading analysis, do the survey during a bright and sunny day, preferably in summer when trees have their full foliage mass.
During the site survey you should be looking for the following obstacles:
• Buildings – certainly you should be informed whether a new building is not being planned nearby, throwing shade to your site;
• Chimneys, power lines, poles, hedges and neighboring roofs;
• Trees – if you’re performing your site survey in winter, remember than in summer trees look different than in winter;
• Hills and other earth obstacles – mind that in winter sun is much closer to the horizon than in summer.
A site that is unshaded during a part of the day might be partially shaded during other time of the day. Similarly, if a site is unshaded in summer, it might be shaded in winter since in winter sun is lower than in summer (and close to the horizon) and casts longer shadows.
2) Underestimating the roof condition
Solar systems can be installed on any roof type.
There are two options for installing solar modules – either mounting them on the roof or replacing the roof tiles with solar modules.
As a rule roofs with composition shingles are the easiest to work with, while those with slate are the most difficult ones.
If solar modules are mounted on the roof, this has the following drawbacks:
• Modules must be removed upon performing any roof repair or replacement activity;
• Installation of brackets and racks could cause roof leaks;
• Roof warranty may be affected;
• Some people might find this unattractive.
Roof-integrated installation costs amount however up to 40% more than roof-mounted installation.
If your roof is relatively old and needs to be replaced in the near future, in order to minimize any redundant costs a smart idea would be to replace it at the time the PV system is being installed.
If you have a new roof, consult both your PV provider and roof repair company how installation of a PV system will affect your roof warranty.
Certainly PV modules can be placed on the ground as well, on a fixed or tracking mount.
3) Miscalculating the available roof area
Usually access space around the modules adds up to 20 % to the required area for placing solar modules.
Don’t try to use every last square inch on your roof to install a solar array because:
• The array gets difficult to install;
• The array gets hard to maintain;
• Wind loading at the edge of the roof increases;
• From a regulatory point of view you could violate some provisions for providing available space for fire-fighters and other personal that might need to access the roof area.
Consider the dead spaces around the array. These are the spots that are either shaded or need to be left between the modules.
4) Choosing wrong orientation and tilt of the solar array
For grid-direct systems the orientation and tilt angle of the solar array is usually subject of roof orientation and slope.
Use compass to check what direction your roof faces. Use a spirit level to measure the angle of the roof from the horizontal.
If your site is located in the northern hemisphere, you should look towards south, east and west. If your location is in the southern hemisphere, you should look towards north, east and west. If you live near the equator, you should look towards east and west.
The ideal roof for mounting your PV array is a roof facing south if you live in the northern hemisphere, and facing north if you live in the southern hemisphere.
Having chosen the right orientation, you have three options for tilting the solar panels, certainly if your roof or installation area permits:
• For average yield throughout the year;
• For maximum yield in winter;
• For maximum yield in summer.
Solar energy differs from month to month and from season to season. This is also true for sun’s position in the sky. That is why you have to choose in advance between the above mentioned options.
For example, if your solar panels are tilted for maximum production in winter, it means that the chosen tilt ensures solar rays to fall almost perpendicularly onto solar panels only in winter.
For average yield throughout the year your solar panels should be tilted to an angle equal to the latitude (in degrees) of your location.
For maximum yield in winter your solar panels should be tilted to an angle equal to the latitude of your location minus 15 degrees.
For maximum yield in summer your solar panels should be tilted to an angle equal to the latitude of your location plus 15 degrees.
How to find fast and easy the latitude of your location?
Just go to Wikipedia and search for your location. Then look at the top of the right corner where location’s coordinates are reported. The first left number is latitude of your location, followed by the longitude. If you cannot find your city in Wikipedia, just find the closest big city to it.
Let’s imagine that you live in Birmingham, Alabama (USA), and you are curious to find what tilt angels should be for the three available options:
From Wikipedia we get:
So the latitude of Birmingham is 33.525°. Therefore the three solar tilt angles for the three above described options are as follows:
– For average yield throughout the year: -33.5°
– For maximum yield in winter: -18.5°
– For maximum yield in summer: -48.5°
6) Improperly chosen mounting of the solar array
There are four types of mounting methods:
• (Sloped-) Roof mounting,
• Flat roof/ground mounting,
• Roof-integrated mounting and
• Wall mounting
The PV array mounting type should be selected by carefully considering:
• Orientation towards the sun
• Site shading
• Weather at the location
• Roof material and bearing capacity (in case of roof mounting)
• Soil type and condition (in case of ground-mounting)
Regarding solar array mounting constructions, mind the following:
• Not every mounting construction is suitable for any kind of module, while certain kinds of modules are intended for a specific mounting;
• It’s a good plan to ask the supplier of the PV modules to install them on the roof;
• To ensure sufficient cooling of the PV modules, enough room should be provided beneath them;
• A design visa and/or a build permit might be required
• All the necessary construction regulations are to be complied with.
11) Ignoring the benefits and drawbacks of solar tracking 
Use of solar tracker is another option for squeezing more power from the sun. A solar tracker follows the sun position and movement in the sky and ensures maximum collection of sun energy by solar panels.
The average efficiency of solar tracker is reported to increase the total production yelled of 25-45%.
Although adding to the overall system costs, residential solar trackers do not need much maintenance. More important however is that every solar tracker is a potential point of failure. Furthermore a solar tracker consumes extra power. What you should also have in mind is that there might be some local regulations that prohibit the use of solar trackers.
Solar trackers are recommended especially in cases of limited space where customer wants to achieve maximum solar array performance.
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