20 years after the first solar boom, some large-scale PV plants are now approaching the end of their official service life. It is often unclear whether the systems are fit for continued operation, and if yes, how. Is it necessary to replace components, and what are the business models for continued operation? This is where repowering comes into play. Revamping, by contrast, involves improving the yield and performance of existing systems.
Both concepts are becoming increasingly important in our mature solar market. In connection with a conference session on the topic at the Intersolar Europe Conference 2024, we spoke to Tomaso Charlemont, Head of PV Revamping / Repowering EMEA at BayWa r.e., about repowering and revamping. Baywa r.e. has already implemented more than 250 Mwp of PV revamping and repowering projects.
Systems are revamped when they are inefficient or when their components, such as modules, inverters, transformer stations or cables, have technical defects. These upgrades are often necessary for technical reasons, as failures due to defects can cause downtime. Revamping only becomes relevant when replacing individual components during maintenance is not enough or no longer possible, or when all – or most – of the key components need replacing.
Repowering eventually follows, or may follow, due to the components’ technological development over last few years. Today's modules are twice as efficient as those of a decade ago. To be more precise, ten years ago, modules had about 12 percent efficiency, today they are at 24 percent. There are two options for replacing old modules with new ones: You can either considerably boost the system’s rated output, or keep the same rated output, maintaining the original feed-in tariff while freeing up two-thirds of the space used. The second option raises the question of what to do with the extra space. If the system gets an additional grid connection, deploying additional capacity obviously makes more sense. The huge advantage is that this does not require a new construction permit, including site studies, because the old system has already been granted a permit. Building a new solar installation in the same location as a previous one does not require a new construction permit.
Just like with any new building project, there are several options for marketing the electricity. One option is the spot market, or else you can opt for a PPA (power purchase agreement) or for self-consumption. Of course, securing a new feed-in tariff is also possible.
There is no specific point in time because technical issues can occur at any time. Take modules, for example: Some will start having technical problems after only ten years of exposure to the elements. That was part of the learning curve. Ten years ago we used certain materials that have now proved to be unsuitable. But there are also solar modules that were installed between ten and 20 years ago that show no signs of fatigue. Besides modules, we also need to consider the inverters. Many inverter manufacturers no longer exist, meaning there is nobody to provide proper maintenance or spare parts. Other weak points include cables and transformer stations. At the time of installation, everybody wanted to get things built quickly without necessarily considering the durability of the materials.
However, based on some of the fault-prone solar modules installed back then, I would say that a system might need to be optimized after about ten years of service life. When it comes to deciding what to replace, I can only say that it varies from once case to the next. It generally makes sense to replace several types of components at once to give the operator peace of mind for the next 25 years. Components cost a tenth of what they did a decade ago.
Of course, this is not a must. We have modernized systems by merely replacing modules, and left the ten-year-old inverters in place. Thanks to high manufacturer quality and regular maintenance, they were still in perfect working order.
Yes it is, even if its not declared as such, because it involves modernizing a system. You might think that it is possible to replace a component with the exact same one. But the truth is that as components have evolved, modules have gotten bigger and inverters have gotten smaller.
Exactly. The question is whether the substructure can be adapted. One argument for revamping is that new modules are lighter, despite being larger. In other words, new modules do not add weight. So you can keep the old substructure. Typically, you need fewer square meters for the same installed capacity thanks to the higher efficiency. But the substructure often needs to be adapted because the width and length of the modules are not the same. It may be necessary to move the mounting clamps.
In some cases, the original manufacturer may still be around, continuing to serve the customer. They might say: “We know the system, we still have the drawings – let us handle it.” But in other cases, the company may no longer exist.
Absolutely. Unlike in the case of new constructions, where you can easily drive posts into the ground and lay trenches for the cables in a field, everything is already installed, which makes it harder to replace components. That is why optimizing an existing system requires precise planning.
A system’s PR depends on two factors: On of them is the modules and inverters. The yield of the modules is measured in electricity and compared to what is theoretically possible according to the manufacturer’s data, based on global irradiation. This is to determine whether the modules have maintained their level of efficiency. Modern modules only lose 0.2 percent capacity each year due to aging – modules of the first generation lost as much as 0.4 percent. Now, is the calculated efficiency loss within the expected range or has it increased? The PR value answers that question.
But the PR value is often also calculated based on the inverters’ degree of availability. Inverters are typically expected to work 90 to 98 percent during periods when electricity can be produced. Let’s say the system works 92 percent of the time, as planned: If the inverter stops working, you have to order spare parts. Since the inverter is turned off, the system is down for two weeks – easily bringing down that 92 percent to 80 percent or even less. This means that the inverters’ reliability rate is key. That is what the PR factor shows. This value is an important basis for discussing with our customers how to solve the problem. Maybe it is not the modules – maybe it is the inverter, or the underground cables. We had a case in the UK where replacing the transformers and inverters increased the PR value by 39 percent, making the system more reliable. It does not generate more electricity, but thanks to its increased reliability, it is able to feed electricity into the grid at a more consistent rate.
The second factor is yield, in other words, power generation. How many megawatt hours can the system generate? This depends on the efficiency of the modules. Today’s modules are more efficient and can generate more electricity. Inverters have become more efficient, reaching 99 percent efficiency, up from 96 percent, which means a higher energy yield. Considering that in certain cases, it is possible to switch from a fixed substructure to a tracking system – in Germany, the latest change in legislation has made this possible – generating even more power. Depending on the location and system, a tracking system can increase the amount of electricity produced by up to 40 percent. This produces two effects: System reliability is improved and additional power can be generated. Investors and system owners will find this very appealing.
Once the system comes to the end of its economic life – in other words, when the feed-in tariff and the lease are about to expire – the system should generally be dismantled, or decommissioned. However, this does not need to mean that a new system cannot be installed in its place, which is known as repowering.
When a system is decommissioned, the system owner is required to restore the piece of land to the way it was before. Alternatively, they could sign a new 30-year lease. They already have a construction permit for the property, and if the permit for the grid connection can also be extended, a repowering project makes sense. So decommissioning does not rule out repowering. For new projects, the usual obstacles are unavailability of land and a grid connection – and an existing system already has both.
Germany was among the last countries to make such changes. France, Italy and Spain already made this possible four or five years ago. The specifics of these legislative changes differ significantly from one country to another. In Germany, we currently have the best conditions. While up until 2023, the law was still very restrictive – only allowing the replacement of individual modules if you could prove they were faulty – we now have maximum flexibility. This allows the optimization of an entire system, as long as it maintains the original rated output.
Exactly. Germany is a sleeping giant. We see great potential in this country.
It usually starts with the realization that the system generates less electricity than expected. There are several ways to search for defects. In most cases, the first step is to analyze the measurement data from the inverters, i.e. the yields and efficiencies, to determine the extent of the problem. The modules are then inspected using drones with infrared cameras to identify potential hotspots and weak points – even in inverters.
You can then remove individual components and test them in a laboratory. We usually also perform an optical inspection to detect problems such as peeling back sheets. All of this is entered into full report with recommendations for the system owner.
The analysis is purely financial, which means that we simply assess whether it is of financial interest to replace an inefficient component with a new one and how much more electricity that would produce. We recommend that system owners to do this analysis themselves, as they understand the financial side of their system and its profitability. As technical advisers, we can provide an outlook and calculate potential future yields. However, if a system has a technical defect, for example a fault in the modules that may cause a fire, we have an obligation to warn the customer of potential risks and advise them on what may happen if they do not replace it.
The challenges are great and often underestimated. Many people think of revamping or repowering as simply replacing components, as if solar technology were built like Lego. But that is not the case. Unlike a new system that is built on a green field, revamping and repowering involve working on an existing system. Parts of the system are already connected to the grid. Therefore the tasks to be performed must be planned separately. You have less space, there is a fence and the system itself. The system’s entire design will change. It has to be very well planned and the companies involved need to have the necessary skills. The planning and engineering for this type of project is a very specific job.
Today, over 95 percent of the material in solar modules can be recovered. Recycling has become economically feasible. The installed components are the property of the system owner. We offer advice and arrange for the collection by suitable companies. Ownership is transferred, and the modules are redefined as electronic waste. The transfer is documented. This process is important, because according to the European WEEE (Waste from Electrical and Electronic Equipment) Directive, the system owner must ensure that the components are properly disposed of and recycled.
