Bifacial Panels Key to Boosting Solar Energy Output

The use of two existing technologies could allow solar panels to boost electricity output by 35%.

Photovoltaic panels are seen on November 22, 2020 in Stoke-on-Trent, England.

Nathan Stirk/Getty Images

Double-sided solar panels featuring tracking technology to follow the sun’s path are the most cost-effective way of harnessing the sun’s energy, a new study says. 

Bifacial panels absorb solar radiation from both the top and the rear sides, while single-axis tracking technology tilts panels during the course of the day to ensure they are always facing the sun.

By using these two technologies in tandem, photovoltaic (PV) systems can produce 35% more energy than standard PV systems that rely on fixed, single-sided panels, says the study, which was sponsored by the Solar Energy Research Institute of Singapore (SERIS).

When the additional costs of bifacial and single-axis tilting technology are factored in, these set-ups produce electricity that is, on average, 16% cheaper than the power produced by standard fixed panels. 

A solar farm using both technologies could cost about 15% more than an installation that used fixed, monofacial panels, but the study argues that the additional investment will pay off.

"The results are stable, even when accounting for changes in the weather conditions and in the costs from the solar panels and the other components of the photovoltaic system,” said lead author Carlos Rodríguez-Gallegos, a research fellow at SERIS.

Rodríguez-Gallegos said there is plenty of evidence showing that these technologies are “a safe bet for the foreseeable future” but cautioned “transitions take time, and time will have to show whether the advantages we see are attractive enough for installers to make the switch.” 

The study indicates that by adopting these two technologies, future solar farms could produce more green energy, helping countries around the world slash carbon emissions from the electricity sector.

Thanks to lower investment costs and strong policy support from 120 governments around the world, new installed PV capacity worldwide will increase by 145 gigawatts in 2021 and 162 gigawatts in 2022, up from the 135 gigawatts added in 2020, the International Energy Agency forecasts.

Technologies in Tandem

This graphical abstract summarizes how this work performs a comprehensive techno-economic analysis worldwide for photovoltaic systems using a combination of bifacial modules and single- and dual-axis trackers.
This graphical abstract summarizes how this work performs a comprehensive techno-economic analysis worldwide for photovoltaic systems using a combination of bifacial modules and single- and dual-axis trackers. Rodríguez-Gallegos et al./Joule

Bifacial solar panels have a top side that harnesses energy coming directly from the sun and a rear side that captures the albedo—solar radiation that bounces back from the ground. They have been around since the 1960s but they didn’t take off until a few years ago, when production costs came down, and are quickly becoming the top choice for new solar farms around the world. 

Wood Mackenzie forecasts that bifacial modules will account for 17% of the global market for solar panels in 2024. The agency said that by then, the installed generation capacity of bifacial solar panels will quadruple, reaching 21 gigawatts. The main reason for the fast growth is “growing affordability,” says WoodMac.

Single-axis tracking technology that allows panels to tilt toward the sun has also been around for a while and although it is expensive, it is often used in large-scale solar projects. Double-axis tracking technology can allow panels to capture even more solar radiation but is not always cost-effective because it has an even higher price tag—unless the panels are installed near the Earth’s poles, which receive less solar energy.

The study notes R&D efforts have long focused on improving solar cell efficiency to boost the amount of energy captured by panels but argues that the key to increasing production is to install panels that feature both single-axis tracking and bifacial technology.

To reach that conclusion, study authors analyzed satellite data from NASA’s Clouds and the Earth's Radiant Energy System (CERES) to measure the total radiation that reaches different parts of our planet’s surface each day. Taking into account the sun’s position during the day, the panels’ orientation, and the effect of the weather, the researchers came up with an estimate for the cost of the electricity the panels would generate through their 25-year lifetime.

Their calculations are valid only for large solar farms with thousands of modules, not for small setups that have higher construction costs per panel but, hopefully, there will be a time when these technologies become affordable enough for homeowners.

"As long as research continues to take place, the manufacturing costs of these materials are expected to keep on decreasing, and a point in time might be reached when they become economically competitive and you might see them on your roof," says Rodríguez-Gallegos.

View Article Sources
  1. Rodríguez-Gallegos, Carlos D., et al. "Global Techno-Economic Performance of Bifacial and Tracking Photovoltaic Systems." Joule, vol. 4, no. 7, 2020, pp. 1514-1541, doi:10.1016/j.joule.2020.05.005

  2. "Renewable electricity." iea.