When studying a site/roof to install the solar power plant, surveyor should at first check for:
- The orientation of roof towards the sun (if not, one should check the possible ways for PV modules to best fit the roof facing towards south)
- Lack of any shading obstacles (during the whole day and throughout the year)
- Minimization of the length of the DC cables between the PV modules and the inverter
- Protection from theft and damage
- Easy access for installation and maintenance of the solar power plant.
Important points that should be considered during the survey
1. Assess possible shading from nearby objects
The solar PV modules should be provided with clear access to sunlight throughout the day (at least between 9:00 AM to 5:00 PM), throughout the year. Please note that even small shadows can severely affect the power output of the PV plant therefore to achieve the maximum from your analysis, perform the survey during a bright and sunny day. Shadow analysis plays a very important role in rooftop solar power plant designing and its operations for its life span, hence should be given priority and should be conducted with well calibrated tools like SunPath Finder, SunEye etc.. This can also be done using PV software such as PV Syst and Helioscope etc.
During the site survey, surveyor should check and record information related to:
- Buildings –whether a new building is not being planned nearby, throwing shadow on the site/roof being surveyed
- Unavoidable objects- Chimneys, power lines, poles and neighbouring roofs
- Trees – if you’re performing your site survey in winter, remember that in summer trees shadow looks different than in winters
2. Determine the roof area for PV installation
While calculating the area available on the roof, one should understand that here we are talking about available and feasible shadow free area where the PV modules can be installed and not the total built-up area of the roof. While estimating surveyor should keep in mind that he should not use complete rooftop are for PV module installation even if its shadow free, because:
- The PV modules gets challenging to install as not movement area is left out;
- Maintenance of the solar power plant is difficult
- Wind load at the edge of the roof increases and can impact the strength
- From a regulatory point of view, you could violate specific provisions for providing space for ventilation, fire fighting lines etc. in case of commercial establishments.
3. Determine orientation and tilt angle
Orientation of the roof and tilt angle are highlighted important and can impact the solar power plant capacity. A compass should be used to check the orientation of the roof. The tilt angle can be checked using tools such a SunEye etc. or simply a spirit level tool to measure the angle of the roof from the horizontal surface.
4. Identify the Suitable Location of components like Inverter, Junction Boxes etc.
This is one of the most important studies during a site survey. It is very important to determine an accessible location of Inverter installation which has sufficient ventilation for cooling and protection from the environment. As per international standards, Inverters are designed to withstand impact due to temperature and rain water as per standard test conditions, however it is a precautionary measure to install inverters under a shade where it is protected. This step is also important because the distance of the inverter from the Solar PV installation should be the shortest to reduce losses.
5. Estimate cabling routes and cable length
The surveyor should also study the location of the various cable termination points associated with the rooftop solar power plant. where the output of the solar inverter is interconnected to the panel. This way an estimation of possible cable routes and the length of the cable required on the interconnection panel, earthing points etc. can be estimated.
6. Check the roof condition and accessibility
Strength of the roof is very important as additional weight of solar power plants will get added to it. Surveyors should learn about the construction and life span of the room and also thoroughly check for any damage, leakage that should be considered while designing the solar power plant.
7. Water availability on the site
Water availability on the roof is very important for seamless maintenance and cleaning of PV modules over the solar power plant life span. Considering Indian situations dry cleaning of modules may not be possible in each location therefore the requirement should be brought in notice of the consumer.