How To Decide If, And When, To Revamp, Repower Or Retrofit A Solar PV Plant
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18 July, 2019

As the solar sector continues to mature, advancing in terms of size, penetration and technology, what does this mean for the first-generation utility-scale plants that are reaching the end of their intended lifespan? When does it make sense to invest in improving a solar plant’s efficiency or operational lifespan through revamping or repowering?

Revamping And Repowering

PV plants’ performance declines slightly every year due to the inherent degradation in PV modules. Compounded by a range of factors, the amount of energy produced by the plant begins to reduce. A decrease in production can be mitigated through revamping or repowering — replacing components in order to make a plant more efficient, to achieve economic benefits or to correct defective or sub-optimal components. Repowering is leveraged to mitigate power degradation or to boost the project. Retrofitting is a type of revamping related to the adaptation of a solar PV plant to new requirements, usually driven by regulatory changes. The voltage dip adaptation needed in Spain in 2010 is an example of retrofitting.

There are many different solutions that can enhance the plant's performance, including retrofitting performance-boosting "coatings" to panels, fitting tilt trackers (to follow the sun’s path, rather than static tracking systems) or adding energy storage batteries. In my experience, owners of solar PV plants striving for operational excellence must prioritize an ongoing cycle of maintenance and assessment to ensure all assets are performing as expected over time, and carefully consider repowering and revamping options as appropriate.

What is the opportunity?

In the United States, there is over 30 GW of operating utility-scale solar PV capacity. If an additional 5% of generation could be achieved from these assets, more than 1.5 GW of clean power would be produced — the equivalent of replacing three coal power plants or supplying energy to approximately 700,000 U.S. households. While repowering alone will not achieve clean energy production goals, it’s contribution should not be overlooked.

There are already many solar plants 10 years old or more, reaching or surpassing the boundaries of their components’ warranties. According to the PV Installation Tracker, more than 40 GW of PV systems in Europe above 100 kW are more than 5 years old. These solar PV plants were built with the technology, and on a viable business case, at that time. Yet as efficiency or reliability decreases, operating expenditure increases. Replacing equipment that is failing, and may not be manufactured anymore, would improve availability and reduce costs. The performance increase of retrofitting measures was found to be in the region of 5-10% in technical studies in the United States and greater than 3% in a detailed study in Italy when a multidisciplinary approach was taken (i.e., technical, financial, legal, regulatory).


From 2010 to 2017, utility-scale total installed cost reductions in many markets (including China, Japan, Germany and the United States) had exceeded 70%. The dramatic decline of component costs, for example, the decline of module prices by more than 75% in the last five years, has been matched by equally dramatic improvements in components’ technology, quality and performance. This equates to fewer problems, more availability and lower operational expenditure.

A number of module and inverter companies have exited the market, which can leave asset owners facing serious challenges in terms of warranty claims and technical support. Inadequate service and expired warranties can mean asset owners have to seek replacements. In fact, a new sales channel has opened up in mature markets for PV component manufacturers offering solutions to component defects or underperformance in plants constructed in the rush to meet feed-in tariff deadlines.

While costs have dropped, efficiency has increased: Power of the modules has multiplied itself by four or five depending on the year of the plant, which means four or five times less space is needed for the same power generation.

Avoiding The Pitfalls

The opportunity to extend the capacity of the plant if the grid connection or off-grid market exists, although it is not always as simple as it seems and underestimating this can lead to serious pitfalls.

You should understand the critical importance of compliance with all applicable regulations, especially in feed-in tariff plants. For example, increasing the total output of your plant could be an issue if the new production exceeds a given feed-in tariff band because new permits will be required.

You should consider the benefits in an integrated way, with legal, regulatory, financial and technical considerations. For example, a higher module power can lead to greater efficiency but inverter voltage changes mean it is not always possible to adapt the input of the transformers, giving rise to "knock-on" problems — and costs — such as the need to change the transformer to adapt the voltage, which requires legal, financial and regulatory considerations.

Each plant has to be studied on a case-by-case basis, not only due to its design specification but also its permit restrictions and in-country regulations. In many cases, it would not be possible to change the physical aspect of the solar PV plant, while on other occasions, the grid connection conditions cannot be changed without applying for new permits.

Conclusion: Not All Solar PV Plants Are Equal

Boosting the output of existing plants, with high feed-in tariffs, or reducing operating costs by replacing components at today’s prices and performance, sounds compelling — and deceptively straightforward. Yet each case requires a detailed analysis of specific considerations, from technical limitations to the policy framework, before any intervention can be made.

Even if repowering seems unsuitable, asset managers can review other areas of operations. More efficient inverters can help to increase output and upgrades to monitoring equipment can help with the predictive diagnosis of issues and standardize performance.

For those agile and astute enough to make the calculation, the prize could be very worthwhile in terms of benefits accrued — lower operational costs, an extended and/or higher revenue stream or the possibility to increase actual performance ratio by as much as 10%. When reviewing your plant's current efficiency, consider not only the regulations attached to PV plants but also innovations that ensure maximum energy retention and gain.



Joern Hackbarth

EVP, Global Head of Engineering and Construction, Sonnedix, overseeing the design and construction of assets for global solar PV platform.

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