Site Assessment 101: A Guide for a Solar EPC's

As an EPC or an installer, before quoting the price and determining the capacity, you will have to perform a feasibility of the site in order to ensure that you not only quote inappropriate price but also take into consideration the solar capacity that ca be accommodated and any risks or barriers in installing a solar rooftop plant. In this blog, we will help you identify all the parameters that you should take into consideration to ensure that your next site is solar-ready and that there are no unknown challenges or risks.

The site parameters that influence the performance and reliability of a rooftop solar plant are - access to solar radiation, shadows, temperature, ventilation, wind speed, building height, terrain, orientation, dust level and pollution, salinity, humidity, extreme weather conditions, etc. Every solar site will be different and there is no one-size-fits-all solution when it comes to a rooftop solar installation. Therefore, it is crucial to plan a rooftop solar plant according to the site condition to ensure optimum performance and safety.

Note: In this blog, we will also consider that the demand is greater than the available space and hence the site readiness is considering the physical aspects of installing a solar plant.

Now, it is very obvious to assume that a site survey would be the first step toward installing a solar plant, but it is always wise to check the satellite image of the location before visiting the site. Let us understand why.

With the help of Google Earth or even Google Maps and the location coordinates, one can figure out the rooftop where the solar plant is to be installed. Both applications, allow you thoroughly measure the site and also give you a general idea of the surrounding area and objects like buildings trees, etc. Now, this gives you an idea of the capacity that can be installed, if it is a larger site, you can plan the visit with 2-3 team members to ensure that all details of the site are covered. Moreover, it prepares you to interact with the client and clarify any issues noticed with maps during the visit. Sometimes there is no access to the roof, especially in the case of industrial roofs. If the maps show a smoke or soot deposition on the roof it means there is a chimney on the roof or in the surroundings which will also impact the solar panels and their generation resulting in a change in the solar capacity planned. It is also possible that the roof might be totally covered in soot and installing a solar plant might not be a wise decision at all considering the generation loss due to the soot deposition.

Therefore, taking a look at the maps before visiting the site is highly recommended.

Now that you have seen the satellite image of the site, let us understand an effective way of conducting a site survey.

Site Survey

A thorough site survey is important because it helps with the smooth installation of a solar system and ensures that you can make the profit you expect without extra costs from delays or materials. If the site assessment is not done correctly, it could result in a bad design and installation of the solar panels. This would lead to problems like difficult maintenance, poor performance, and an unreliable system. During the site survey, you should be able to visualize where the solar plant and its components will go.

1. Things to carry

Let us understand the equipment that you should carry during any site visit.

1. Personal protective equipment (as applicable to site condition – mandatory in case of sloped and or industrial roofs)
2. Site Survey Form/Questionnaire + Notebook
3. A compass to record direction (Mobile app also works perfectly fine)
4. A measuring tape/ Laser Gun to measure area
5. An angle measuring equipment (Mobile app also works perfectly fine)
6. A working partner (Recommended for sites larger than 10kW)

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2. Accessibility and Storage

The site might be a residential, commercial or Industrial one, whichever it is, it is extremely important that it has safe and sufficient access for the installation team to reach the roof and carry solar panels, cables, etc.

Residential and Commercial site:‍

• Ensure the staircase is wide enough to carry the solar panels. A typical solar panel with capacity more than 540Wp will be more than 2m in length and 1 m in width, hence the staircase should be wide enough to carry these panels safely.

• In case of commercial buildings, if it is ahigh-rise building, carrying solar panels manually will be a difficult and time-consuming task. In such cases, it is recommended to check if the service elevator can accommodate the solar panels and structures. If a service elevator is not available, then check with the client if the passenger lift can be used to transfer the components to the roof and also check if it is big enough. If say elevator is not an option, estimate the extra charges that you will have to bear for manual transfer and also the extra time it will take. This will ensure that you are quoting the price and timeline which is realistic.

Industrial site:

• If it is a sloped roof, check what kind of access is available and if a new safe access is needed. Although solar installation is a one-time activity, but the client will have to maintain the solar plant for its lifetime and the plant also should be accessible in case of any emergency.

• If the site has only a monkey ladder, then you will have to account for the cost of hydra/machine to shift the solar panels and other equipment.

Also, check with the client to store the components during the installation period, some of your components will also need a covered space plus a safe space will ensure that no material goes missing or is stolen.

Moreover, check with the client for the nearest electrical connection as you will need a power supply during the installation.

3. Type of roof

The type of roof can make all the difference for a solar installation, right from the structure used, capacity that can fit, construction time, safety requirements, and even how the operation and maintenance is performed.

RCC roofs/Terrace  

• Ensure the parapet height is more than 0.8 m, ensuring complete safety during and post installation.

• Check with the client for the waterproofing situation on the roof and figure out the type of foundation fix, whether a penetrating or a non-penetrating solution is needed.

Metal roofs

• In case of metal roof, check whether the roof isa trapezoidal roof or a standing seam roof as the type of structure will vary as per the type of the roof. Also, measure the sheet profile dimensions to ensure you procure the right structure.

• Tilt angle and orientation (direction) of the roof is extremely important for estimating the generation and also ensuring that it is safe and practical for the installation team to work even with the help of safety harness.

• Also, ask the client for the as-built roof layout and elevation layout, this will ease the process of solar panel layout and reduce manual efforts of locating the purlins and rafters.

4. Safety and Risk assessment

To initially assess the structural integrity of a roof, you can check if you feel confident moving around the roof without hesitation and if there are no visible cracks present. Additionally, the age of the roof can also affect its structural integrity.

If, during your visual inspection, you feel that the structure may not be safe, it’s advisable to request a structural integrity report from the client’s architect. Only proceed with the installation after receiving confirmation from the architect to ensure safety and prevent any future accidents.

In case of sloped roof, determine the requirement of a safety line on the roof for installation and operation & maintenance. Ensure you plan the safety line right from the entry of the roof. Also, plan the installation such that, the safety line is installed prior to the actual installation of solar panels and other components to ensure a safe working environment.

5. Area –Obstructions

Probably the most important aspect of determining the size of the rooftop solar plant is the area available. Calculate the roof dimensions accurately and hand draw the roof layout if not already available. Note the dimensions of all sides. Also, it is important to note the dimensions of any obstructions as this area has to be excluded while planning the solar capacity.

In case there are too many obstructions, you can suggest the client an elevated roof that will not only ensure higher capacity but also act as a sit-out or a cafeteria.

In case of metal roofs, exclude the area of skylights, air vents etc. Also, note the dimensions and distance between these obstructions.

6. Shadow –Dimensions of objects

Objects that come in the path of the incident solar rays any time during the day, will cast shadows and hence reduce the solar generation. A taller object located in the east direction would cast shadows during morning and a taller object located in the west direction would cast shadows during the afternoon. When multiple rows are placed, one row can cast shadow on the other if not properly placed.

Important to Note:

• ‍Shading does not only lead to lower generation but can also damage the PV modules over a period of time.

• The Objective of shading analysis should noted with loss estimation but to understand and review unavoidable shadow, select appropriate inverter, and optimize string design to minimize loss due to shadow.

The most accurate and easy method to determine usable and shadow-free area is by using a reliable software. If the software shows shadow during most of the hours from 09:00 AM– 16:00 PM., then it is recommended not to install solar. If the shadow is only a few hours during morning or during sunset, the software will estimate the solar losses. To know more about the impact of shadow on a rooftop solar plant you can checkout this blog from our resource center.

7. Equipment positioning

Determine suitable location for inverters and other electrical equipment: ‍

1. Location of DCDB, ACDB, inverters should be such that their access is controlled.
2. Minimum distance from the PV array to reduce losses.
3. Inverter should be installed in such a place where there is enough space for cross ventilation, heat dissipation, and maintenance. The inverter manufacturer generally recommends this in their installation manual.

Identify cabling routes and therefore the required cable run distances:

Determine cable routes and hence cable length based on array location, combiner box location, inverter location, and location of the main switch board. Cable routes are not always the shortest paths of the cables. The cable routes have to be decided based on wiring rules, considering the safety of cables and personnel alike.

1. Verify the location of equipment and routing of the cable at the site and measure cable length and compare with the drawing / design documents.
2. Determine the length of conduit or cable tray required for the installation.
3. Prepare the cables according to the length and size as determined after site measurement

8. Plan for operation and maintenance

Operation and maintenance are crucial for the effective functioning of a solar plant. One important activity is the cleaning of solar panels, as any accumulation of dust or dirt can lead to a reduction in energy generation. It is essential to ensure that a water source is accessible for a rooftop solar plant. For larger solar plants, it is advisable to include a cleaning system equipped with pipes and nozzles in your quotation. Additionally, safety lines and harnesses are not only required during the installation phase but are also important for the operation and maintenance of the plant.

For your next installation, we hope that these pointers will help you thoroughly assess the site. This will assist you in installing a rooftop solar plant that is completed on time, is well designed, and functions properly.