When the UK’s largest subsidy-free solar farm opens later this year, there will be something a bit different about its panels: unlike traditional panels that absorb energy on only one side, these panels will be absorbing sunlight from both sides.
The new solar farm in York, developed by Gridserve, uses “bifacial” modules, a technology that has become one of the fastest-growing trends in solar because it helps solar panels generate more electricity.
The 35-megawatt plant will generate enough power for 10,000 homes. “Bifacial panels are a no-brainer,” says Toddington Harper, chief executive of Gridserve. “In our opinion, they will be the panel of choice for the utility-scale market.” He estimates the solar farm will generate 20 per cent more energy due to its combination of bifacial solar panels and trackers that enable each panel to follow the sun, compared with traditional static photovoltaic panels.
Solar has become the world’s biggest source of new electricity — it is bigger than wind, gas, or coal in terms of new installed capacity each year, according to S&P Global. Last year some $131bn was invested in solar, in spite of decreasing government subsidies, according to BloombergNEF.
However the solar sector has been relatively slow to innovate on the traditional photovoltaic panel, which is now seen as a low-margin, commoditised product. While the price of solar panels has fallen dramatically in the last decade, the improvement in the physical performance of standard panels has not changed nearly as much.
That could shift though, as subsidies for renewable decline, according to solar executives and analysts. In the absence of subsidies, projects that are more efficient and perform better have a greater economic advantage, they say.
“There is a lot of room for further performance improvements [in solar],” says Cedric Philibert, senior renewables analyst at the International Energy Agency. In addition to bifacial modules, he says that technologies combining different types of substrate material into panels to capture more of the light spectrum also offer potential to grow.
“Bifacial technology captures more light, and it is not very much more expensive, so it makes sense,” he says. The first large-scale bifacial projects are only one or two years old, he points out, adding that the technology started to take off “only very recently”. In a bifacial panel, the back of the panel is replaced with glass, allowing energy to be absorbed from both directions. To date only about 1GW of bifacial projects have been built globally — representing less than 1 per cent of all solar projects — but that figure is expected to grow.
Bifacial panels could be more than a third of the solar panel market by 2028, according to an estimate in a recent academic paper in Energy and Environment Science. Bifacial modules were a core element of one of the lowest solar bids recorded — at just 1.79 cents per kilowatt-hour for a 300MW project in Saudi Arabia, the 2017 bid was the cheapest solar project ever proposed up to that point. However Saudi Arabia’s government, which awarded the project, instead awarded the contract to developers using traditional one-sided panels despite their higher price. The government did not give a reason for its decision; analysts however attribute it to a view prevalent two years ago that the technology was too unproven for such a big project.
Oliver Davies, renewables performance manager at Rina, a certification consultancy, says uncertainty about how the new design will perform has slowed its adoption. “One of the biggest barriers on utility scale projects is getting that comfort and reducing those risks for investors,” he says. It is hard accurately to model how much sunlight will be reflected off the ground and on to the back of a bifacial panel. This varies depending on whether the ground is covered with dirt or plants and can also vary from season to season.
“A key focus is looking at the ‘albedo’ of the ground, which is essentially the reflection of the ground,” says Mr Davies. This allows for an accurate prediction for how much power bifacial panels will be able to generate on a specific site. He says a typical gain is 5 -15 per cent. “The good thing about bifacial technology is that it is more of an evolutionary step, rather than a completely different technology,” he adds. “It is considered as an easy gain.”
Mr Harper of Gridserve points out that bifacial panels like those to be used at their new solar farm in York cost nearly the same as regular one-sided panels. Bifacial made a “huge difference” to the economics of the project, which does not have a feed-in-tariff subsidy, he adds. “I knew that fundamentally we should be able to make it work without subsidies,” he says. “A key piece of that is to try to generate as much value as possible from a project, without increasing the costs.”