High-power string inverters can significantly reduce the balance of system (BOS) costs compared to central inverter solutions as they require fewer inverters per block and have a better DC-to-AC conversion ratio, a panel of industry experts at a webinar hosted by Mercom India said.

The impact of inverters on project performance, stability, and the levelized cost of energy (LCOE) is substantial.

The webinar, titled “How to Save Costs with High Power String Inverters in Large Scale Projects,” highlighted how high-capacity string inverters could help save costs for large-scale solar projects.

The panelists were Nilesh Mahajan, CEO and Director of Roofsol Energy; Yogish HN, AVP-BD at Enerparc; Kannan Devaraji, Senior Manager at Enerparc; Gajanan Sawant, Senior Manager – Design and Engineering at Cleanmax; Sunil Panigrahi, Country Manager – India at Hopewind and Rakesh B P, Solution Manager at Hopewind.

Priya Sanjay, Managing Director, Mercom India, moderated the session.

Cost Savings

As high-power string technology requires fewer inverters per block, the costs associated with cabling, combiner boxes, junction boxes, mounting structures, and other electrical equipment are reduced. This brings down installation, operations, and maintenance expenses over the project’s lifecycle.

“We have calculated that using high-power string inverters in large-scale projects can save around $8,000 to $9,000 per MW in costs,” said Panigrahi . “For a 100 MW project, the savings become really substantial when you multiply across the entire capacity.”

“On the DC side, you can reduce the number of cables, and on the AC side, you can reduce the cable size. By this, you can reduce the project cost,” he added.

Apart from reduction in capital costs, developers also look at savings in LCOE over the life of the inverter, explained Nilesh Mahajan. “At the end of the day, we also want to see how the inverter will perform. Apart from capital costs, developers and EPC contractors also look at the costs associated with the inverters after installation, during maintenance, and the lifespan of the inverters and the critical components that need to be replaced.”

Better Conversion Ratios

Another key advantage highlighted was the higher AC/DC conversion ratios achievable with string inverters. “This higher DC overloading allows capturing more energy from the solar modules and accounts for any mismatch losses or degradation over time,” explained Rakesh.

Distributed string inverter configurations also provide more design flexibility than centralized solutions. If a fault occurs in one string, the entire plant is not shut down, unlike a central inverter.

Flexibility in OEMs

The introduction of high-power string inverters also offers increased flexibility when using various original equipment manufacturers (OEMs). Implementing high-power string inverters allows for the integration of multiple module technologies and ratings, providing developers and EPC firms greater flexibility.

“By introducing high power inverters, we have the flexibility to use different OEM and different technology because module costs are one of the deciding factors in the system as well as BOS costs,” said Kannan Devaraji.

Earlier conventional solar setups with a single central inverter could utilize only a single OEM of modules, limiting options when it came to costs and supply timelines.

“The cost and supply of a module also plays a role in overall costs,” added Devaraji.

Technological Challenges

However, string inverters also face technology challenges that need to be addressed. A major concern was derating, especially for hot, arid regions like Rajasthan, where temperatures routinely exceed 50°C. Developers stressed the need for more intelligent cooling systems.

“One of the major criteria before selecting an inverter is how it performs in extreme temperatures, along with reliability and safety aspects,” said Mahajan. “Certification is another aspect we look for. Since the projects are connected to the grid, we have to comply with the requirements of the grid operator,” he added.

Another requirement is faster response time to support dynamic reactive power requirements for large plants. Gajanan Sawant felt that under one-second response time is needed to provide grid services like frequency regulation, as opposed to about five seconds currently.

Highlighting the advantage of string inverters when it comes to response time, Rakesh explained that a lower number of inverters usually leads to faster response time. “When you connect a lower number of inverters, the response time is faster.”

Cyber security to safeguard the distributed assets from potential hacking was another area of focus for the panelists. They felt that inverters must have advanced security measures, certifications, and secure servers to prevent any data breaches or manipulation attacks.

Later this month, Mercom will host a webinar on how insurance can help protect renewable energy projects from commercial cybersecurity attacks.

Last year, Mercom hosted a webinar exploring the rising demand for high-capacity string inverters and larger solar modules with a power rating of 600W+. The webinar found that the shift to larger modules had prompted upgrades in project designs and other equipment to accommodate higher generation.

Sign up for Mercom’s next webinar on – How to Protect Renewable Energy Projects from Commercial Cyber Threats with Insurance