Bifacial tracking, the real deal

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Data obtained at BiTEC indicates that bifacial modules on a Soltec SF7 solar tracker achieve a bifacial gain of up to 19.2% in conditions of high albedo. With medium albedo, the bifacial gain of the SF7 bifacial tracker achieved almost 12%. Initial data shows that the SF7 bifacial solar tracker achieves a 2.4% higher bifacial gain compared to trackers with modules in a 1-in-Portrait configuration.

The field of bifacial module technology has once again revolutionised the solar energy arena. Bifacial technology is influencing both the design of fixed solar power tracking assemblies as well as the design of the plants themselves, albeit to a lesser extent. Design aspects that used to be considered as insignificant with monofacial modules are increasingly important and are making the difference between efficient and inefficient bifacial plants. This difference could represent millions of Euros.

Bifacial plants must optimise production on both the front and the rear sides of the module to improve the bifacial gain, in other words, the energy gain produced on the rear side of the module as opposed to the front side. This is affected by parameters such as the albedo, the height of the mounting, shadows, module temperature and the distance between rows.

With the aim of analysing every parameter that impacts on bifacial gain, in July 2018, leading solar tracking company Soltec, inaugurated its Bifacial Tracker Evaluation Center (BiTEC) in California. This centre aims to enhance its knowledge of bifacial behaviour by adapting the modules to enable continued advancement in the technological development of bifacial solar tracking. The research centre is equipped with 18 solar trackers (300 kWp) installed in areas with different albedo conditions, pitches and heights. For this, Soltec is working with the National Renewable Laboratory (NREL), Black & Veatch and the Renewable Energy Test Center (RETC), as well as with the leading module manufacturers such as Canadian Solar, Hanwha Q CELLS, Jinko, LG, LONGi and REC.

BiTEC has enabled Soltec to measure the bifacial gain of the solar trackers under real conditions in addition to comparing the two most widely used configurations on today’s solar tracker market: 1-in-Portrait (1P) and 2-in-Portrait (2P). The results for the first period, analysed following the methodology endorsed by Black & Veatch, show that the solar panels mounted on the SF7 bifacial solar tracker in a 2P configuration demonstrated a 2.4% higher gain over the same modules in a 1P configuration.

The measurements taken at BiTEC between September and November 2018 show bifacial gains of over 19% for individual bifacial modules on an SF7 bifacial tracker with an albedo of 63% and white ground cover. It is estimated that even with lower albedo values and bifacial gain, the economics of a hypothetical project that uses bifacial modules on SF7 bifacial trackers continue to be better than those of the same project using bifacial or monofacial modules on 1P trackers. The bifacial gain of the individual bifacial modules on an SF7 bifacial tracker is 2.4% higher than that of the same modules on a IP solar tracker, according to data gathered at BiTEC. The greatest bifacial gain of the SF7 bifacial tracker is due to the absence of shadows on the rear side of the modules meaning that they can operate at a lower temperature.

Based on the results obtained at BiTEC, estimates from Soltec indicate that the use of bifacial modules in place of monofacial trackers in PV plants can generate economic advantages and thereby improve the return on investment.

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