Share of string inverters in the Indian solar market is increasing rapidly. It went up from only 1% until 2016 to 9% in 2017 for new utility scale solar capacity commissioned. We expect the trend to accelerate even further in the coming years.
Increased adoption of string inverters for utility scale projects is in line with experience in other international markets including USA and China. About 50% of utility scale capacity installed in China in 2016 used string inverters. In the USA, string inverter share is expected to grow up to 28% in 2020.
Key reasons for increasing share of string inverters are as follows:
- Flexibility and yield: Although efficiency of central inverters is usually higher in comparison to string inverters (about 99% vs 98.5%), string level optimization can deliver better power output with string inverters due to increased reliability and redundancy;
- Installation time: String inverters can be installed much faster than central inverters as they do not need special containers or civil structures for housing – useful for projects with tight deadlines;
- System availability and maintenance: String inverters can be easily replaced in case of any issue reducing the plant downtime whereas, owing to their large size, central inverters require dedicated on-site technical support;
Huawei and Sungrow, both Chinese companies, are the biggest proponents of usage of string inverters for utility scale segment.
The main advantage for central inverters is their low upfront cost and maintenance cost. However, string inverters provide savings in BOS costs due to no requirement of string combiner boxes, container or civil structures etc.
Further, falling capital and maintenance costs of string inverters means that cost advantage of central inverters has narrowed significantly in the last few years.
Ultimately, the decision of string vs central inverters depends on individual project factors such as location, size, site contours and uniformity, site accessibility and installation time available.