How modernizing your PV power plant pays off

Warum es sich lohnt, das PV-Kraftwerk zu modernisieren

When the inverter’s service life suddenly came to an end, low performance was threatening the profitability of Guntram Grieseler’s solar power plant. He decided to modernize his plant with innovative SMA string inverter technology. As a result, Guntram Grieseler’s plant is now producing even more energy than before. Here’s how it was done.

Project owner Guntram Grieseler has been operating the Saint Guillaume solar power plant in the French community of Lüe since 2011.

With an output of 2.9 megawatts peak, the power plant supplies solar power for 1,000 households.
The Lüe solar farm sustainably blends into its surroundings, as the PV modules are placed on the roofs of greenhouses where a local organic farmer grows his vegetables. Solar energy here allows a double harvest from the same area.

When the inverters’ service life suddenly came to an end, low performance was threatening the asset´s profitability – so Grieseler decided to modernize his plant with innovative inverter technology.


“With its broad portfolio, SMA made it possible to offer our customer a tailor-made solution.” 

Gerald Claus, E+WS Energie + Wasser Service GmbH

Modernizing needs to be economically and ecologically efficient

To ensure that the repowering project would be both economically and ecologically efficient, the SMA Repowering Team professionally analyzed the existing infrastructure. The challenge of replacing equipment in existing projects is to ensure that the new equipment can be easily and optimally integrated into the existing infrastructure. The cost-benefit ratio must be in balance.

Modernizing an existing PV plant with new string inverter technology

SMA Repowering Team found Sunny Highpower PEAK3 inverter would best meet Grieseler’s needs and could be optimally integrated into the centralized system layout.

An advantage not only during the coronavirus pandemic: The inverter provides optimal performance at a light weight. It is cheap to transport and the PV professional can install it in a one-man show. This reduces the PV plant’s downtime and significantly minimizes revenue losses.

Thanks to the repowering, the plant is now producing even more energy than it did before.


“We´ve repowered the inverters very efficiently within only two weeks. Thanks to the SMA inverter Sunny Highpower PEAK3, we could reuse all our cabling and the existing plant solutions. This was a great benefit.”

Guntram Grieseler, Geschäftsführer, Leonidas Optima GmbH


„Higher yields, better service“

When is it worth upgrading a system, and what are the most important things to bear in mind? We put these questions to Tobias Probandt, Key Account Manager, and Christopher Merz, System Development Engineer at SMA.

How can the system operator see that it is time to upgrade the system?

Tobias Probandt: There are various reasons for repowering. The system or some of its components may be defective; it might be falling short of its target power values; or it might no longer meet current technical requirements. It may also be the case that certain parts – or the system itself – were not installed properly or that original spare parts are no longer available. The devices fail increasingly often, affecting system availability. This has a direct impact on energy yields and thus on system amortization. The best thing that operators can do is to ensure reserves for this from the very beginning. Then you just need a little of courage to make the change. But you can be sure it will pay off.

How do repowering measures in decentralized system structures differ from those in centralized system structures?

Christopher Merz: Decentralized systems are usually equipped with string inverters of < 100 kW, which are distributed throughout the entire PV system. The strings are connected to the inverters individually, and the default AC voltage is 400 V or 480 V. Devices can often be replaced in a straightforward, one-to-one swap. If the on-site conditions permit, a more powerful inverter can also be installed to replace multiple existing devices. One 50 kW device, for example, could replace five 10 kW devices. The main challenge is thus rather upgrading system communication because old devices often use communication standards that are outdated. This is why it is important to plan repowering measures with the utmost care and precision.

When it comes to repowering centralized systems, the challenges relate to the electrical compatibility of the components with one another and also mechanical integration into the existing inverter station. It should always be ensured that as many components as possible – DC main cables, medium-voltage transformers, switchgears, etc. – can be reused. A lot of parameters need to be coordinated. PV modules can be grounded or ungrounded; DC voltages range from 600 V to 1500 V; and there is a variety of transformer types and AC voltage levels. Therefore, SMA replacement inverters are usually customized. Whether Sunny Central central inverters or string inverters like Sunny Highpower PEAK3, our customers take delivery of a device that is perfectly tailored to their specific application.

What specific aspects did you need to take into account in the Lue project?

SMA Christopher Merz

Christopher Merz

Christopher Merz: The most important thing was to retain the centralized system structure in Lue. It was also important to continue using the existing medium-voltage transformers. Thanks to the flexibility of the Sunny Highpower PEAK3, we had no problem meeting all these requirements. Two existing DC main cables were connected to each inverter. The AC voltage was parameterized to 340 V AC, allowing continued use of the medium-voltage transformers.

What are the benefits of repowering with string inverters?

Christopher Merz: The string inverter Sunny Highpower PEAK3 combines the benefits of a relatively small power class with those of a centralized system structure. The compact device simplifies delivery and on-site installation. Since only a part of the PV generator is connected to each inverter, generator faults (e.g., insulation errors) have much less impact on system yield and can be more easily localized. However, as the centralized system structure is retained, structural alterations are needed only in the immediate vicinity of the existing inverter station. The wiring to and from the station on the DC and AC sides can be left as it is.

Tobias Probandt: With our powerful inverters Sunny Highpower PEAK3 and Sunny Tripower CORE2 we offer outstanding quality and flexibility at highly competitive prices. New components also enable higher efficiency. Optimizing your PV system will help you to maximize yields over the long term and ensure a long service life. You will get new warranty periods and avoid expensive servicing. You will also benefit from new features like remote monitoring and data visualization.



Are you interested in finding out whether it’s worth upgrading your system and what are the benefits?

Repowering for PV power plants


For further questions send an e-mail to or fill out the contact form on the website.


This article was published in 2021. As we are constantly developing our solutions, there may be newer or additional options for the tips and techniques in this article.

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