Solar is one of the cleanest power sources we’ve obtained. But it could be even greener.


There are solely 4 corporations that manufacture polysilicon, a crucial materials for photo voltaic panels and semiconductors, in the United States. This spring, one of them obtained an enormous inflow of money. In April, a Korean firm referred to as Hanwha Solutions introduced it had turn into the largest shareholder of REC Silicon, which may produce 16,000 metric tons of polysilicon yearly from a refinery in Washington State—sufficient to fulfill greater than 1 / 4 of the U.S. photo voltaic trade’s demand. Hanwha, which already operates the largest U.S. photo voltaic panel manufacturing facility in Georgia, described the acquisition as half of a plan to “revitalize the U.S. photo voltaic market” by making a made-in-America provide chain from uncooked supplies to completed merchandise.

If that plan is profitable, it wouldn’t solely reveal the U.S. is, the truth is, in a position to make photo voltaic panels with domestically sourced supplies — a key coverage aim of the Biden administration. It would additionally present that polysilicon refining, the most energy-intensive step in photo voltaic manufacturing, could be made significantly greener in the course of.

In the pantheon of local weather options, low-carbon polysilicon might not sound significantly attractive. But it has turn into a scorching matter in the world of photo voltaic as companies and governments begin considering severely about how you can drive their emissions all the solution to zero, together with in the so-called upstream provide chains that present supplies and elements for renewable power. Already, photo voltaic photovoltaic, or PV, panels generate amongst the lowest carbon emissions of any power supply on the market over their whole life cycle, together with manufacturing. But as the trade grows, even the comparatively small emissions related to manufacturing PV panels could turn into vital in mixture, doubtlessly peaking at ranges similar to the present yearly emissions of giant industrialized nations like France or Germany. 

A current research discovered that in a state of affairs the place the world deploys photo voltaic quickly, PV manufacturing could result in 25 to 30 billion tons of cumulative carbon dioxide emissions by the center of the century, consuming up roughly 10 % of the remaining carbon funds for limiting world warming to 1.5 levels Celsius (2.7 levels Fahrenheit). If we don’t quickly embrace renewables like photo voltaic, we have now little likelihood of assembly that local weather goal. Still, it is doable to extend our odds by cleansing up polysilicon manufacturing, which accounts for roughly half of the local weather affect of photo voltaic PV.

REC Silicon is exhibiting how the trade would possibly do this. The firm’s polysilicon manufacturing facility in Moses Lake, Washington, makes use of low-emissions hydropower from the native electrical grid, as an alternative of the coal that’s typically used to power polysilicon refineries in China. What’s extra, as an alternative of utilizing the energy-intensive course of to purify silicon that’s normal in the trade, the Moses Lake facility has pioneered the commercialization of an alternative course of that REC Silicon claims makes use of as much as 90 % much less power. 

The Moses Lake facility has been closed since 2019 because of Chinese import tariffs that priced the silicon maker out of the photo voltaic market. Now, due to Hanwha’s funding, REC Silicon has begun the course of of bringing the facility again on-line. 

“We have a really steady, low price of power to supply polysilicon that’s additionally very low carbon,” REC Silicon CEO James May instructed Grist. “And that’s what we wish to do.”

To perceive why polysilicon manufacturing produces emissions, it’s important to perceive how it works. Originating from quartz, a humble, ample mineral,  polysilicon is a extremely refined type of silicon that converts daylight into electrons inside a PV panel. To make it, producers warmth quartz in a furnace to supply metallurgical-grade silicon, which is about 99 % pure. Typically, metallurgical-grade silicon then will get reworked right into a fuel, which is launched right into a superheated reactor the place it resolidifies onto seed rods as polysilicon, a type of silicon upwards of 99.999999 % pure. This course of, often called the Siemens course of, is how greater than 95 % of polysilicon is refined round the world as we speak, based on the clear power analysis agency BloombergNEF.

Rods of polysilicon stacked in a facility
Rods of polysilicon are saved in a Hemlock Semiconductor facility.
Hemlock Semiconductor

While the Siemens course of has been round for many years and is thought-about the most dependable solution to refine polysilicon, it has a draw back. As the silicon rods are forming at the heart of the reactor, the reactor partitions must be stored cool to forestall the silicon from crystallizing there. Maintaining that temperature distinction is “actually power intensive,” Jenny Chase, who heads photo voltaic evaluation at BloombergNEF, instructed Grist. To make polysilicon affordably, corporations arrange their refineries in locations with entry to low-cost and ample electrical energy. In China, the place 78 % of world polysilicon manufacturing occurred final yr, this implies areas the place the electrical grid consists of tons of coal.

“Most individuals are very conscious of what occurs with photo voltaic as soon as it’s put in the subject — that it generates zero-carbon electrical energy,” stated Michael Parr, the government director of the Ultra-Low Carbon Solar Alliance, an trade group targeted on driving down emissions throughout the photo voltaic provide chain. “Most individuals don’t know that upstream, in manufacturing, there can be fairly excessive carbon emissions, significantly in the Chinese provide chain.”

One method for the photo voltaic trade to scrub up this provide chain is by enhancements in manufacturing effectivity. This is already taking place: Data shared by BloombergNEF reveals that between 2014 and 2019, the quantity of electrical energy wanted to refine a kilogram of silicon declined 22 %. At the identical time, the silicon content material of photo voltaic panels is falling as producers proceed to make photo voltaic cells — the particular person, wafer-like items of silicon inside a photo voltaic panel — thinner and lighter. And the efficiency of these cells, or their capability to transform daylight into electrical energy, is steadily rising

“The effectivity of the photo voltaic cells has improved by about 50 % in the final 25 years, and quantity of silicon we use is lower down by an element of two or three,” Meng Tao, a photo voltaic sustainability researcher at Arizona State University, instructed Grist.

Greater effectivity means much less power and emissions are expended to fabricate a photo voltaic panel. Further local weather beneficial properties are doable if producers power their operations renewably. Right now, U.S. electrical grids are inclined to be much less carbon-intensive than their Chinese counterparts, which means there’s a great local weather case for onshoring the energy-intensive steps like polysilicon manufacturing. That hasn’t escaped the Biden administration: In a February report on the photo voltaic provide chain, the U.S. Department of Energy, or DOE, recognized ramping up polysilicon refining as the high factor the U.S. could do to safe a steady photo voltaic provide chain. Such an trade, the DOE famous, could take benefit of low-emissions hydropower in the Northwest and elsewhere. 

“Economics is on our aspect right here,” Garrett Nilsen, appearing director of the Solar Energy Technologies Office at DOE, instructed Grist in an e mail. “Hydropower is one of the least expensive varieties of electrical energy in the nation, so polysilicon producers naturally find their crops accordingly.” The DOE, he stated, is additionally investing in packages to deploy further wind and photo voltaic power extra cheaply round the nation, doubtlessly creating new renewable power hotspots the place polysilicon makers could arrange store. 

When it comes again on-line, REC Silicon’s Moses Lake facility will use hydropower produced on Washington State’s Columbia River to supply polysilicon for photo voltaic panels. The largest U.S.-based polysilicon producer, Hemlock Semiconductor, produces polysilicon for each the photo voltaic and the semiconductor trade in Hemlock, Michigan. There, the electrical grid already features a vital quantity of hydroelectric storage capability, and it’s getting steadily cleaner as the native utility phases out coal and brings extra photo voltaic power on-line. Hemlock photo voltaic business supervisor Phil Rausch instructed Grist that per kilowatt-hour of power used, the emissions related to the electrical energy the firm purchases are about half of its rivals’ electrical energy emissions. 

A person wearing a mask and headphones sorts polysilicon
A Hemlock Semiconductor worker breaking and sorting polysilicon in a cleanroom.
Hemlock Semiconductor

Beyond enhancements in manufacturing effectivity and getting power from greener grids, a handful of polysilicon makers have turned to different processes which might be much less power intensive than the Siemens course of. Chief amongst these is the so-called “fluidized mattress reactor,” or FBR, course of REC Silicon makes use of at its Moses Lake facility. Hot, silicon-rich fuel is fed right into a chamber containing pellets of silicon, which develop in dimension as extra silicon crystallizes on them. Because warmth is launched from exterior the reactor, no cooling is required, permitting appreciable power and value financial savings, based on May.

Industry consultants say it is harder to supply ultra-high-purity polysilicon with FBR expertise in contrast with the Siemens course of, limiting its adoption in the trade. Rausch of Hemlock stated that his firm investigated the FBR course of “extensively” over the final decade however in the end decided that the polysilicon it produced “didn’t meet the wants of the trade.” May, nevertheless, is assured that REC Silicon can use the technique to make polysilicon that meets the more and more stringent purity necessities of photo voltaic producers due to a sequence of current upgrades to its Moses Lake facility. 

Parr of the Ultra-Low Carbon Solar Alliance is cautiously optimistic. FBR “is a harder expertise to get higher purity from,” he stated, however REC Silicon has spent years bettering its course of. “I believe like several expertise, it takes some time to excellent it, however it is inherently decrease power, decrease carbon expertise, in order that’s promising.”

Any polysilicon maker that may ship a greener product — whether or not that’s because of extra environment friendly manufacturing strategies or cleaner power sources — is more likely to have a rising benefit in the photo voltaic market as corporations or governments begin paying extra consideration to provide chain emissions. 

“We’re already seeing the downstream purchaser turning into far more delicate to the embodied carbon in the provide chain,” Rausch stated. As an instance, he notes that a number of years again, when France started taking the carbon footprint of photo voltaic panels under consideration in its public procurement course of for clear power, corporations shopping for polysilicon from Hemlock began doing higher in that market. New labeling schemes, like an eco-label for photo voltaic that the Global Electronics Council is growing in partnership with the Ultra-Low Carbon Solar Alliance, are more likely to drive additional curiosity in clear polysilicon.   

Efforts to make photo voltaic manufacturing extra sustainable shouldn’t detract from the must deploy photo voltaic power as rapidly as doable, says Garvin Heath, an power sustainability researcher at the National Renewable Energy Laboratory, or NREL. Across the whole life cycle, NREL researchers have discovered that photo voltaic PV already generates 10 to twenty instances decrease carbon emissions than fossil gas power sources like fuel and coal. Solar is already a crucial device for preventing local weather change, regardless of manufacturing emissions. 

At the identical time, the trade ought to do the whole lot in its power to maintain its emissions as little as doable, contemplating how little carbon we have now left in the financial institution to keep away from crossing harmful local weather thresholds.

“We shouldn’t cease deploying PV as a result of we wish to make it higher,” Heath stated. “We ought to deploy as a lot as doable and make it higher.”




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