Efficiency Gains Vary from 5 to 25 Percent

Expert Interview – Monday, March 02, 2020

Intersolar has showcased a lot of innovations in solar modules in recent years. What made this possible?

There are many cell concepts that have been in development for a long time and could have entered the market much sooner. But the long-term dominance of low-cost, multicrystalline silicon modules with aluminum backsheets prevented this from happening. In 2016, LONGi launched its low-cost monocrystalline wafers and modules, literally declaring war on multicrystalline wafers. Since then, increasingly complex, highly efficient PV modules have been appearing on the market. Bifacial modules in particular have the potential to push down solar electricity production costs even further in the coming years.

More and more manufacturers are also offering bifacial modules. These modules are capable of producing electricity on both the front and the rear side. What is their current market share, and what do you expect in the future?

Until 2019, around 5 gigawatts (GW) of bifacial PV systems had been installed worldwide, which is less than one percent of the total installed capacity of 600 GW. But this share is set to rise sharply in 2020. We are expecting additional installations to the tune of 15 GW, most of which are being manufactured in the USA, because there is currently a customs exemption for these types of modules. This corresponds to around 10 percent of annual deployment. As more and more large PV systems in deserts with an output of 500 GW or more are being equipped with bifacial modules, we anticipate that the annual market share will reach 40–50 percent by 2025.

How much additional yield can bifacial modules generate?

That is a complex question, because the additional yield of bifacial modules depends on at least four factors: the geographical location and the local diffuse irradiation, the module’s bifaciality factor (50–95%), the albedo factor, which is the amount of irradiation reflected by the ground and the resulting irradiation on the rear side of the module, as well as installation conditions. Bifacial gains of 20 percent are possible, but the ultimate question is how high the electricity production costs are. Module efficiency, in other words the costs per kilowatt hour, will always be more important than module costs, or costs per watt.

Where are bifacial modules employed?

Currently, bifacial modules with single-axis tracking systems are mostly used in deserts, in South America, the USA and the MENA region. Compared to fixed installations with monofacial modules, gains are around 30 percent. The single-axis tracking system can increase yields by 20 percent and the albedo factor may produce an additional bifacial gain of around 10 percent.
But bifacial modules can also be used to boost yields in Germany, for example on flat-roofs or carports, in building-integrated photovoltaics and in vertical applications, such as agricultural PV, or in noise protection walls along highways. In these cases, efficiency gains vary from 5 to 25 percent and must be calculated for each application.

What are the pros and cons for investors?

One advantage is the potential for lower PV electricity production costs. Also, bifacial modules are generally glass-glass modules, meaning that they have a longer service life. The disadvantage is that there is a lot of uncertainty due to the complexity of the topic and some sweeping statements that have been made. That is why we are providing information through our bifacial workshops.

What can participants expect from your bifacial workshops?

We present the current state of the art and profitability, and we give an overview of available modules. It is important to understand which factors influence yield and how they can be optimized depending on the application. Also, we have invited two or three utility companies that are already using bifacial modules to share their experience. Next2sun, Solitek and PVEL have already accepted.

What other innovations are you expecting to see at Intersolar in Munich?

In my opinion, the key trends are to be found in storage devices. They are the last piece of the puzzle to make photovoltaics completely sustainable for private households. Almost everyone is aware that for large systems, it’s possible to achieve PV electricity production costs of below 4 euro cents/kWh in Germany, and below 2 euro cents/kWh in other parts of the world. But the costs will go down even more: In two or three years’ time, we will see production costs of below 1 euro cent/kWh. What we need now are more affordable battery and hydrogen storage systems.

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