Powering up. Perfecting your rooftop solar’s efficiency

After a slow start, rooftop solar installations are picking up in India and have just reached 15 GW, of which about 3 GW is residential and the rest commercial and industrial. Residential rooftop solar installations, being typically small, are however, spread across lakhs of homes. Here’s what you should know when you opt for rooftop solar.

Should you put the modules on the roof or at an elevation?

The modules are mounted on a structure, which is galvanised iron for RCC roofs and aluminium rails for tin shed. However, the roof’s orientation and angle play a critical role in energy capture. If it is suboptimal or if shading from nearby structures is a concern, elevating the panels can be a more effective solution.

For elevated installations, it’s helpful to understand the different types of structures based on height. Typically, there are three categories: low-rise systems, which are less than 3 ft above the ground at their lowest point, mid-rise systems, and high-rise systems, which have an elevation of 6-8 ft from the ground.

Low-rise systems are suitable for open areas with good sunlight exposure but may still be subject to shading. Mid-rise systems strike a balance between accessibility and performance, allowing for better airflow and reduced shading. High-rise systems are ideal for maximising sunlight capture, especially in areas with obstacles like trees or buildings, but they also require careful engineering to ensure stability and safety. Additionally, elevated installations facilitate better airflow around the panels, which helps in cooling them and improving their efficiency. For homes, a high-rise structure can create a gazebo/pergola thereby ensuring that residents don’t lose the roof space and can use it as a seating area.

Maintenance is also a significant consideration. Rooftop installations may limit access, making routine maintenance and cleaning more challenging. If the panels are elevated, it often provides easier access for inspections and maintenance tasks, which can enhance the longevity and performance of the solar system.

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How can one ensure that the modules do not get damaged or fall off?

One of the first considerations during the initial design phase is to position the modules in a shadow-free area. This is essential because shading can lead to the formation of hotspots on the panels, which can cause localised overheating and ultimately damage the solar cells. By conducting thorough site assessments and shadow studies, we can identify the optimal locations for installation, maximising both performance and safety.

During installation, torque marking is an important practice to secure the modules properly. By applying the correct torque to the mounting hardware and marking it for future reference, we can ensure that all components are tightened to the manufacturer’s specifications. Over-tightening can lead to hotspots, ultimately causing the glass to crack, whereas not tightening them enough can reduce weather resistance. Ensuring proper placement and secure installation is extremely important for the panels to generate DC power reliably over 25 years.

Should the structure be galvanised iron or painted?

It’s better to use hot-dipped galvanized iron (HDGI) structures for their superior durability and resistance to rusting. Unlike painted steel, which can deteriorate over time due to wear and tear and exposure to the elements, galvanised iron undergoes a protective coating process that significantly extends its lifespan, making it a more reliable choice for long-term installations. This rust resistance is especially important in environments with high humidity or in coastal conditions, where corrosion can occur more rapidly.

It is important to avoid site fabrication works whenever possible. By opting for prefabricated structures, which are manufactured under controlled conditions, customers can ensure that the quality of the components meets stringent standards.

How to decide the right tilt?

Generally, the tilt angle is based on the latitude of the geography; for most parts of India, this is between 8 to 30 degrees. However, a 10-degree tilt is optimum for southern India based on seasonal energy needs.

Are trackers a good option?

Trackers can enhance solar energy production by following the sun’s path, maximising exposure. However, when it comes to rooftop installations, trackers are generally not the best option because rooftop spaces are limited with power capacity of less than 100 kW and the additional complexity of installing and maintaining tracking systems can outweigh the benefits.

How to maximise electricity generation?

First, ensure a shadow-free area during the initial design stage, by conducting site assessments to identify potential obstructions. Further, all components of the solar should meet the standards set by regulatory authorities (MNRE, BIS and SECI) to ensure safety, efficiency and reliability.

Proactive monitoring is essential for identifying any issues that may arise during operations. This involves using smart monitoring systems that provide real-time data on energy production. It is important to monitor real-time alerts for early resolution. Analysing the generation data will help identify any upcoming defects. Additionally, keeping the solar panels clean is vital, as dust build-up and debris accumulation can obstruct sunlight and decrease efficiency.

If I opt for battery storage, what kind of batteries should I go for?

Lithium Ferro Phosphate (LFP) batteries are recommended due to their high energy density, longer cycle life and faster charging capabilities compared to traditional lead-acid batteries.

Capacity is another critical factor, measured in amp-hours (Ah), which indicates how much energy the battery can store and deliver. Depth of Discharge (DoD) is also important, as it specifies how much of the battery’s capacity can be safely used without affecting its lifespan; lithium-ion batteries typically offer a higher DoD than lead-acid batteries. Additionally, consider the battery’s charge and discharge rates, as these affect how quickly energy can be drawn from or replenished in the system. Finally, it’s essential to assess the thermal management requirements of the battery, as temperature extremes can significantly impact performance and safety.

(This is the second part of the two-part feature about rooftop solar, presented with inputs from Co-Chairman and CEO of Fenice Energy, a leading rooftop solar company. The first part was published on November 11.)