Author: Jason Deign
Italy needs to cover around 1,000 km2 with solar panels over the coming decade if it is to hit its target of net zero emissions by 2050. Could repowering existing sites be a more sensible option?
From Lake Como in the North to Sicily in the South, Italy is a land of outstanding natural beauty. It is also a country committed to preserving the environment, with plans to cut carbon emissions by 60% between now and 2030. But slashing emissions while looking after the land could be a challenge. Most of Italy’s decarbonization push will come from the installation of new onshore wind and solar PV capacity.
According to a paper published this April in Nature, the country may need a fourfold increase in PV capacity to deliver the 100 TWh of solar electricity a year forecast in the Italian Integrated Energy and Climate Plan for 2030. Assuming a PV module efficiency of 22%, that would equate to more than 1,000 km2 of land given over to ground-mounted solar capacity. That is a lot of space in a country where the landscape is a national asset. But perhaps this new capacity will not need new land after all.
One suggestion offered up by the paper’s authors is to focus on infrastructure-integrated PV. This includes rooftop solar and building-integrated PV (BIPV). Solar arrays on buildings have the advantage of being located on or close to sources of electricity demand, minimizing the need for transmission infrastructure.
And rooftop PV is booming in Italy after the introduction of a 110% ‘super bonus’ tax break for renovation projects that was introduced in May 2020 and extended through to the whole of 2022 in December. But the number of rooftops due for renovation is limited. And the other component of infrastructure-integrated PV, BIPV, has so far failed to live up to its promise not only in Italy but also in the rest of the world. There is, however, another space-saving option.
The case for repowering Italy’s older PV plants
As the Nature paper authors point out, there is ample scope to repower existing utility-scale solar plants in Italy. Most of the existing PV capacity in the country is over a decade old, fruit of a boom that saw Italy becoming Europe’s largest solar market in 2011. By the end of that year, Italy had installed more than 13 GW of solar power. That is almost 61% of the total capacity in the country at the start of 2021, according to figures from the International Renewable Energy Agency.
Investors at the time were most likely expecting their plants to last at least 25 years, and probably did not envisage upgrading them after a mere 10. But they may not have anticipated how far solar technology would go within a decade. PV modules today, for example, are a far cry from their predecessors 10 years ago. Thanks to an increase in wafer size from 156 mm in 2011 to 210 mm today and other technological innovations such as Multi Busbar, PERC Mono and high-density interconnection solutions, module power has more than tripled, from approximately 250 W to an expected 670 W by the end of this year.
Roughly speaking, this means you can almost triple the output from a 2011 plant by upgrading it today. It is important to note that this increase in power is a relatively recent trend. Five years ago, the average module rating was approximately 250 W. And even today, a reference module offers 585 W. But Trina Solar’s Vertex DEG21C.20 bifacial module can already deliver up to 670 W of power. And as well as getting more power per module, from backside and frontside, developers can now get more modules per string. An open-circuit voltage of 45.9 V can accommodate around 20 kW per string with Vertex modules compared to 15 kW for standard modules.
Getting a lot more power per string, with higher-quality products
This results in 5 kW of extra power per string compared to today’s reference modules—and significantly more for modules installed 10 years ago. It is not just module power that has improved over the last decade, either. Manufacturing standards have come a long way, too. Trina Solar’s fully automated Vertex factories, for instance, employ non-destructive cell cutting technology and intelligent manufacturing to deliver products guaranteed to deliver a minimum 85% of rated power even after 30 years of operation, such as the Vertex 670W TSM-DEG21C.20.
This is a million miles away from the state of the art in 2011, when the solar industry was still maturing. And many Italian developers at the time were not even using state-of-the-art products, but settling for whatever they could find in the rush to meet installation deadlines for subsidies. Improvements in module efficiency, design and manufacturing alone would provide a compelling reason to upgrade many of Italy’s older solar plants. But other plant technologies have evolved too, adding to the argument for repowering.
One of these is the inverter admissible voltage, which has more than doubled from 600 V to 1,500 V. Combined with low-voltage modules, this increase allows for significantly more power to be harvested per string, greatly reducing the balance of system costs in modern PV plants. Another important area of development involves solar trackers. The value of tracking systems in boosting yield has long been known, but recent years have seen not only an improvement in the accuracy of trackers, but also in their cost and reliability. TrinaTracker offers different tracking solutions, such as Vanguard and Agile, which adapt to all project needs.
Storage and the benefits of a single solution provider
Thirdly, perhaps the biggest source of solar innovation in the last five years has been the ability to combine PV plants with reliable, low-cost battery storage systems. These are becoming an increasingly indispensable component of European solar plants as PV penetration increases and price cannibalization starts to affect the profitability of projects.
Importantly too for repowering projects, the addition of a battery allows developers to significantly increase the output of their plants without having to upgrade their grid connections, since any excess production above the capacity of the connection can simply be stored and delivered later. One final trend is worth noting. In the past, developers would have had to rely on a range of vendors for project development. Now, however, an original equipment manufacturer such as Trina Solar can provide modules, trackers and storage as an integrated solution provider.
That could be just what Italy needs to reach its solar targets.