Although solar panels generally have a 25-year warranty and can continue to generate power for more than thirty years, the technology behind inverters and other system components can become outdated much faster. The easiest solution to ensure solar projects are operating at their peak is to replace inverters in a repower situation. World of solar energy spoke with Igor Mogilevski, product and solutions director of inverter manufacturer Solis, about repowering efforts and the small details that need to be considered before taking on these operational costs.
SPW: What is repowering?
Mogilevsky: Repowering addresses the widespread obsolescence of solar sites that were developed with central inverters about a decade or more ago, and it is necessary to maintain production at these sites. It’s an especially good option for system owners who want to get the power back online while keeping costs down. Many repowering projects focus on replacing inverters because solar panels can maintain performance longer, but it can also include upgrading additional system components.
What are the challenges in strengthening projects?
Lack of spare or replacement parts and lack of warranty support, especially in situations where OEM companies have gone out of business. Compatibility can also be a big problem. New central inverters often have significantly higher power capacities and voltage ratings compared to older models (1,500 V versus 600 V).
Alternatives to central inverters, such as string inverters, can provide the flexibility you need, but mainly require rewiring on the AC side, which can be a significant challenge for owners due to additional labor costs and physical location limitations.
When does repowering make financial sense?
It’s all about weighing the capital expenditure (CapEx) for repairs against the potential loss of revenue. Typically, only part of the site is underperforming, prompting owners to consider repowering as a cost-effective option; here labor is almost always the most important cost and decisive factor. Therefore, the decision balances technical solutions with implementation work.
How can I best select an inverter?
There are many factors to consider, but inverter selection is ultimately based on current and AC voltage requirements. For AC voltages between 360 and 480 we would choose our 75 to 100 kW series inverters; for 208 or 200 V we would use the inverter from the 30 to 60 kW series; and for higher voltages such as 690 to 800 we will typically use our 255 or 350 kW inverters.
Ultimately, the mains voltage determines which type of inverter is required for connection.
What are the advantages of a string inverter over a central inverter for repowering?
A very big advantage, which almost goes without saying, is the fact that there are currently more string inverters and their components available on the market – which also makes them easier to repair.
With central inverters, spare parts and repairs may no longer be available, leaving owners to solve the problems independently, which can be especially challenging for non-technical people. Meanwhile, string inverters provide a flexible solution for different voltages and configurations, making them suitable for a wide range of applications and locations.
What are the benefits of changing central inverters in a repower situation?
It is actually a very simple installation process. With central, existing components can often be left in place and the inverter is replaced one-on-one, which simplifies the whole process.
Any disadvantages?
I would say limited flexibility and availability. Today’s central inverter technology does not have the same type of inverters for drop-in replacement, as they typically have much more power than older inverters. Custom-developed products are an option, but this can be very expensive and result in long periods of reduced or discontinued energy generation.
Can you talk about the benefits of a backwards compatible string solution?
String inverters have historically been backward compatible, unlike central inverters, which often require significant rewiring between generations. For example, our older generation 100 kW series is backwards compatible with our current series, simplifying replacements. This obviously reduces costs associated with labor and equipment.
Can you provide a brief overview of a repowering proposal scenario?
At Solis we simplify the process. With just an existing single-line diagram, our engineers can create a technical/commercial proposal for repowering projects, including quotes for situations where only equipment is available and do not incur labor or other project costs, which are typically handled by the owner or EPC. We also help recommend products and configure designs to meet the unique needs of each project.
Supply chain issues appear to be a common problem in the search for new power. How does Solis guarantee delivery?
I understand. The expectation of a sharp increase in energy supply due to the aging of so many utilities, combined with competition for new installation resources, only underlines this concern. However, as Solis has an annual production capacity of 80 GW, we are well positioned to overcome any supply chain constraints. Furthermore, the automated nature of our production process ensures steady production of products with high efficiency and reliability. In my opinion, this is an important reason why Solis stands out in terms of resilience. SPW
