Site survey is the first and most crucial step in the solar design process since the data collected during survey serves as a foundation for making further detailed proposals. Therefore an accurate site survey is a must for any solar installer.
Main objectives of a solar site survey
- Ensure a site is free from shade due to obstacles such as water tanks, AC units, staircase, etc.
- Clear access for maintenance at the site
- Appropriate orientation to the sun
- Obtain dimensions of the roof structure
- Aesthetics of the installation
- The energy consumption of the consumers.
For example, a software based shading analysis of the site can save losses incurring due to inefficient generation. Even a little bit of shade can significantly affect the output and efficiency of a solar power system. Electrically, most PV panels are divided into 3 ‘zones’. If you get shading on just one of those zones then the effect isn’t as bad; however, even partially shading three zones together can lead to a reduction in output of up to 60%. Worse still is if the shading affects both zones at once, for example shading the bottom of the panel. In these cases, even just shading the bottom row of cells would reduce the total power output of the panel by 90-95% of the entire string!
Hence it is crucial to assess the site for all necessary criteria before the installation is done.
How a site survey form looks like?
Every site is unique and requires different design approach. EPC’s can reach out to companies offering design consultancy works. One such company is “Heaven Designs Pvt. Ltd.”
Click here to view their 126 kW design and engineering work for a pharmaceutical industry owners from Vadodara who decided to go solar.
Common mistakes during a solar site survey
1. Ignoring the shade due to obstruction
Consideration of obstructions present on the rooftop like HVAC systems, water tanks, etc and their shadows is an important factor in calculating the area which is shade free and suitable for panel installation. Also the shadows from nearby trees and adjoining buildings should be properly accounted for.
There may be a case that some part of the roof are shadow free during the survey, but may have shadows, during the later part of the day. Therefore, the survey period should not be stuffed during a single time duration but rather spread across multiple hours of the day. The area should be shade free for at least 5 hours (9 a.m to 2 p.m) a day.
2. Failing to conduct roof condition assessment
Failing to consider the structural stability of roofs, especially in case of shed roofs can lead to long term problems such as damage during heavy rain or wind. It has been observed in the past that the entire roof getting blown away with panels during a mild cyclone.
3. Inaccurate roof dimensioning
Accurate measurement of the roof dimension is a very crucial aspect in solar site survey. The plan for access areas (walkways) should be clearly laid out after talking to the customer. Using every bit of available roof space can lead to difficulty in panel installation and further maintenance.
4. Inaccurate orientation and tilt measurement
Orientation and tilt of the roof can significantly affect the solar access values and overall energy generation. The optimum orientation depends upon the hemisphere your building is located in and the latitude of the location respectively.
Ideally the building roof should be south facing in Northern hemisphere and vis-à-vis.
5. Inappropriate selection of mounting mechanism
Choice of mounting system can affect the energy generation numbers. Improper selection of mount type can lead to drop in generation values by up to 20%. Also mounting system influences the life of panels and the stability of roofs. Generally on roofs, two types of mounting mechanism are provided-
- Flush mount– mostly in case of shed roofs
- Elevated mount– in RCC roofs, when there is shadow from adjoining objects (trees and buildings) or when there is an obstruction present on the roof.
6. Improper location of inverters and other DC components.
If the site selection for inverters is not done properly, it may result in higher losses due to increased cable length. Losses on the DC side are more as compared to the losses on AC side. It may also increase the overall cost of the system due to increased cable requirements. Therfore the inverter should be located close to the array to minimize DC losses.
How TSL can accelerate the whole site survey process with improved accuracy?
TSL offers a cloud based platform for the solar designers to analyze the clien’t site virtually rather than doing onsite survey. Designers can make use of both satellite images for simpler surveys and drone images in case of large scale analysis for remote sites.
Click here to look at our “Case Study: Solar Potential estimation at IIT Mandi”, where we carried out large scale analysis for IIT Mandi campus spread across 538 acres using drone imagery.
The roof dimensions can be precisely measured from the available google images. The obstructions present on the roof, nearby tress and buildings as well as their shadow effect on the roof can be easily marked.
TSL also offers accurate 2D and 3D modelling which can help solar installers to convince their clients by showing them, how their roofs will actually look after the panel installation. This can help in increasing their conversion ratio due to enhanced customer satisfaction.
Moreover, this entire processes mentioned above can be completed well within 30 minutes which conventionally took an entire day for on-site survey. So, it helps in significant cutback in design duration which eventually results in reduced number of business cycles in closing a particular deal.
Site survey thus is a very crucial step in deciding the conversion of a particular deal and therefore should be made robust with no margin for errors. The use of available AI tools, not only saves time and effort but also improves accuracy and hence should be effectively used by design engineers to maximize their productivity.