Consider the source part 2: consideration of incorporated carbon
August 11, 2021
Photovoltaic solar panels – the symbol of industry – are a bit of Rorschach’s test. What do you see when looking at one? The starting point of renewable energy production or the end of a murky supply chain? Wonder of scientific innovation, or the shortcomings of global mass production? Maybe all that. A solar field is large, its modules contain multitudes. All we can say for sure is that every solar panel needs photons to generate electricity, the same photons our eyeballs use for sight. In our summer edition of the magazine (coming soon – subscribe here), we’ll highlight a few solar panel production and supply issues for you to see.
here is Part 1: The fight against forced labor in polysilicon if you missed it.
Solar photovoltaic technology produces electricity without generating carbon emissions, but the carbon is linked to the manufacturing, transportation and construction of the system itself. The “embedded carbon” of photovoltaic modules in particular is the subject of more scrutiny these days.
One example is the European Union, which is putting in place a mandatory carbon footprint disclosure requirement for photovoltaic panels this year. France has already included built-in carbon criteria for solar modules in its tenders, and South Korea has a similar policy.
“There’s no supply constraint here, it’s a question of market demand and developers’ willingness to get started,” says Andreas Wade, director of global sustainability at First Solar. “If you look at the PPA space, thought leaders here like Salesforce and Microsoft don’t say anymore, let’s look at the MW we’re buying. They want to look beyond and maximize their impact with the purchase of renewable energy.
Indeed, the Renewable Energy Buyers Alliance (REBA) is working with companies to enable a demand signal for carbon transparency in solar manufacturing through the DISC-e (Decarbonizing Industrial Supply Chain Energy) program. This will establish a standard language for tenders for the supply of low carbon modules and letters of request for environmental product declarations (EPDs) to be sent to module suppliers.
WattTime uses an analysis of avoided emissions combined with a life cycle analysis to determine a project’s net emissions benefit. Here is a “avoided emissions” schedule for four different PV technologies when installed in California. The arrows = zero emission net return on investment.
“Energy buyers from the commercial and industrial sectors who are currently participating in the DISC-e Solar Working Group have indicated their intention to prioritize RFPs. [RFP] offers with low-carbon solar panels starting next year, ”says Jen Snook, head of supply chain and international collaboration at REBA.
Why photovoltaic modules?
Cement, steel, and glass are carbon-intensive inputs into the solar supply chain, of course, but they are minor compared to polysilicon, the semiconductor of most PV modules. The difference in lifecycle emissions between the lowest and highest emitting technologies can vary by almost a factor of three, according to research by WattTime.
Polysilicon, in particular, is the result of an extremely energy-intensive process: quartzite is combined with charcoal or wood chips in a high temperature oven to leave metallic silicon 98-99% pure. This silicon metal is then sent for the production of polysilicon – a refining operation that converts the solid silicon metal into a gas, which is then ultra-purified by a chemical vapor deposition process and turned into a solid. This leaves solar grade polysilicon greater than 99.999999% pure. And that’s just the poly. Traditional wafer making uses a method known as Czochralski (Cz) ingot pulling, where this ultra-pure polysilicon is melted again, at over 1440 C, and a single crystal is literally extracted from the smelting for decades. time.
So, yes, to make a renewable omelet, you have to melt and remelt a few eggs. That’s why the location of this process – and what ultimately powers it – makes a big difference. The US Department of Energy’s Argonne National Laboratory noted in 2014 a 50% increase in the carbon footprint of a module made in western China powered by coal compared to a module made in Europe . That’s closer to 40% today according to Hemlock Semiconductor’s 2020 Sustainability Report.
“If you look at most of the US, European, and Malaysian producers, their poly is from hydropower or mixed grids. Most of the power plants in western China are 100% coal-fired, ”said Michael Parr, executive director of the Ultra Low Carbon Solar Alliance (ULCSA), which brings together manufacturers of photovoltaic panels across the supply chain reducing the carbon intensity of solar energy. manufacturing. “It’s heavily subsidized and there isn’t a lot of motivation for it to be energy efficiency.”
The manufacture of coal-fired modules means 260 lbs of coal burned in additional emissions compared to an ultra-low carbon module. REBA estimates that the deployment of low-carbon solar power compared to regular solar power over the next 20 years could avoid 2.1 gigatonnes (2.1 billion metric tons) of CO2 emissions, or the equivalent of emissions from the global aluminum industry.
“Solar power buyers can send a strong signal to decarbonize solar power manufacturing by purchasing low carbon modules,” Parr said. “An ultra low carbon solar ecolabel is being developed by an independent standards body. “
What to look for?
• Most Tier 1 vendors have performed a full ISO 14040 lifecycle assessment. Check them out.
• EPEAT labels. The ISO 14024-certified Global Electronics Council (GEC) manages the EPEAT Type 1 eco-label, which is a registry for sustainable electronics. Last October, GEC launched categories for photovoltaic modules and inverters. EPEAT criteria assess the complete product life cycle and are based on the industry’s premier sustainability leadership standard NSF / ANSI 457. It incorporates carbon embedded in this label.
• French carbon certificate. You could optionally specify modules that are sold in the French or South Korean markets, which have made their own calculations in terms of acceptable embodied carbon levels.
• The ULCS ecolabel. The GEC is also in the process of developing a ULCS designation for PV which will be added to its current EPEAT Sustainable PV Ecolabel. This will provide a unique eco-label for buyers looking for low carbon solar modules.
First Solar has the only PV module currently listed in the EPEAT registry. According to its 2020 Sustainability Report, in 2019 alone, First Solar reduced its GHG emissions intensity by almost 40%. Its manufacturing energy intensity (energy consumption per watt produced) decreased by 36% from 2018 to 0.16 kWh per watt, mainly due to increased throughput and efficiency of its manufacturing process. of Series 6. In 2019 and 2020, First Solar received an A- from the Carbon Disclosure Project (CDP) in recognition of the company’s disclosure and management of its climate change risks and gas emissions Greenhouse effect. In 2020, she joined RE100 and pledged to power its global operations with 100% renewable energy by 2028.
Green wafers on the way
A competitor seeking to reduce the carbon footprint of pads is NexWafe. Stemming from the ISE of the Fraunhofer Institute for Solar Energy Systems in 2015, NexWafe’s production of Green Silicon EpiNex silicon wafers “eliminates intermediate steps and avoids mechanical ingot machining,” explains the CEO of NexWafe, Davor Sutija. “This reduces waste to almost zero and means we form much thinner, high performance wafers. This doubles the amount of watts per gram of silicon. Since our inserts are not sawn from ingots, no etching is required to remove saw damage, which means they can be used in many low temperature cell processing lines.
NexWafe ensures that 95% of the silicon in the chlorosilane feedstock ends up in the wafers, minimizing waste and eliminating the many energy-consuming steps inherent in traditional Cz wafer manufacturing. The result is more watts per gram of Si raw material and 70% less energy used in the wafer manufacturing itself.
NexWafe focuses on n-type monocrystalline platelets for high throughput cell lines, especially those using HJT, TopCon or IBC cell technologies. NexWafe expects to complete its commercial readiness in 2022 and is positioned to scale up and innovate in a plant with a wafer capacity equivalent to the equivalent of 400 MW of cells.
Tags: Consider the Source, First Solar, Q Cells, REBA, Renewable Energy Buyers Alliance, Ultra Low-Carbon Solar Alliance