Comment | With higher revenue and lower operations expenditure, module-level power electronics provide superior lifetime value, writes Lior Handelsman.

The inverter landscape in the commercial PV market is rapidly evolving. This evolution is being driven by the growing role that inverters have in upfront costs (capital expenditure) and ongoing costs (operational expenditure) of commercial PV systems.

As the brain of PV systems, inverters are responsible for monitoring and managing energy generation.

While inverters may only account for about 10% of the system cost, they influence about 30% of system cost (inverter, electrical balance of systems and labour), manage 100% of system production and control operations and management expenses by enabling PV asset management.

Because of this, there has been a growing trend to move towards string inverters and module-level power electronics technology in commercial systems.

Central inverters were the standard for commercial systems over the past decade. A fundamental reason for this trend was the economy of scale which allows lower cost per watt for large inverters, thus decreasing the upfront cost of a commercial PV system. However, as the industry has matured the cons of central inverters have become more apparent.

Central inverters require a large footprint of land. They also require expensive maintenance contracts and can only be serviced by specialized teams, which leads to high operations and management expenses. In addition, generally inverter malfunction results in downtime in a significant section of the array, leading to revenue losses.

These disadvantages, along with the decreased cost per watt of string inverters, have prompted the transition to a decentralized architecture in commercial systems that uses multiple string inverters instead of central inverters.

According to research firm IHS, the market share of string inverters grew from 28% in 2014 to 34% in 2015. The main drivers for this trend are ease of operations and management, simple replacement (requires fewer employees on site and fewer skilled employees), higher system uptime and lower land use. An additional benefit of string inverters is that they provide multiple maximum power point tracking and higher-resolution monitoring than central inverters, but there is still room for improvement.

For these reasons, decentralized architecture is constantly gaining market share. However, the traditional topology of string inverters, which is still used in the majority of commercial installations, still has a number of significant drawbacks.

Commercial systems using traditional string inverters suffer from decreased output caused by module mismatch. Since modules are wired in a series, they usually do not work at their maximum power point and therefore suffer from energy loss. This topology also suffers from design limitations (that is, strings need to be at the same length, use the same type of modules, and be positioned at the same angle).

Real life installation constraints, especially in rooftop systems, result in either wasted roof space or unnecessary duplication of balance of system components. Additional drawbacks are safety concerns and lack of insight into module production and remote troubleshooting. To meet safety standards or insurance requirements can require the addition of costly equipment. Lack of module-level monitoring and remote troubleshooting not only can decrease revenue from reduced system uptime but also increase operations and management costs.

Because of these drawbacks, the same trend that is shifting the commercial market layout to string inverters is continuing to advance it towards including module-level optimisation. Module-level power electronics offer increased power production by not only eliminating energy loss for module-level mismatch but also allowing optimal roof utilisation and installation of more modules through constraint-free design.

In addition, module-level power electronics offers enhanced maintenance and remote troubleshooting which reduces lifetime operations and management cost and enhances asset management capabilities by lowering the number of site visits as well as time spent on site. Inherent to module-level power electronics technology is its ability to reduce safety risks for fire fighters, installers and maintenance personnel by enabling module-level shutdown of high DC voltages.

Even though module-level power electronics technology has become a larger part of the commercial market, there is still room for growth. Solutions with module-level power electronics offer investors and system owners potentially higher revenues throughout system lifetime because they enable more revenue generation from the system and the ability to future proof their asset against some unexpected variables that could lead to underperformance from module-level mismatch.

In addition, module-level power electronics reduces both balance of systems costs during installation and operations and management cost throughout the system lifetime. Bottom line, with higher revenue and lower operations expenditure, module-level power electronics provide superior lifetime value.


Lior Handelsman is vice-president marketing and product strategy at SolarEdge, which he founded in 2006.