The weekend read: Solar needs aluminum, but it has a carbon problem – pv magazine International
https://www.pv-magazine.com/...05/the-weekend-read-solar-needs-aluminum-but-it-has-a-carbon-problem/
The energy transition, the World Bank says, will require more aluminum than any other metal. In order to keep temperatures below a two-degree increase, clean energy technologies will need almost six million tons of the metal each year by 2050. By comparison, the combined total of lithium, cobalt and nickel, the mineral poster children of the energy transition for their use in batteries, is not expected to pass four million tons. These estimates rely heavily on myriad assumptions, but they underline the importance that metals have along the path to zero-emission energy.
Almost all this aluminum for clean energy will be used in solar module frames. Its resistance to corrosion and light weight make it an optimal choice for exposure to the elements and ensuring modules structural stability.
Aluminum’s energy challenge
Aluminum may be needed for the climate, but the industry’s main environmental challenge is its own climate impact, according to engineering professor Guðrún Sævarsdóttir at the University of Reykjavik. Production is reaching ever higher volumes, but so are the industry’s carbon emissions.
“There has been a large increase in the production volume of aluminum [over the past two decades], it has more than doubled since the year 2000,” says Sævarsdóttir. “And a lot of that development has been based on coal power, unfortunately.”
New Chinese aluminum smelters have driven the spike in production, and they now produce more than half the world’s new aluminum. While the country relies on coal for 70% of its power, the power mix of aluminum smelters is more than 90% coal, according to Sævarsdóttir’s research.
Mining, refining and smelting new aluminum produces nearly 2% of the world’s total carbon emissions. Every ton of aluminum produces on average roughly 15 tons of CO2 equivalents. That’s almost four tons higher than 20 years ago. By some measures the jump in aluminum production may mean 400 million more tons of CO2 equivalents each year by 2040.
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The process is not only energy intensive, but the mineral’s oxygen combines with carbon anodes to emit CO2. The direct carbon emissions make up roughly 10% of the process’s total emissions, and electricity consumption contributes 71%, according to Sævarsdóttir’s work.
“We’re not going to get rid of these emissions unless something is done about the process,” says Sævarsdóttir.
Recycling dramatically reduces the energy required to feed the metal into circulation, and aluminum is in theory infinitely recyclable. The Aluminum Association, an industry representative body, estimates that 75% of all aluminum ever produced is still in circulation. Mining companies are inching toward investing in recycling plants, such as Rio Tinto’s Canadian plant announced in September.
In the World Bank’s two-degree scenario, the proportion of recycled aluminum will grow, but it will still only cover 61% of demand. The ASI expects to release proposed standards to address climate impacts in the next several months for consultation, but establishing a path for carbon reduction may take much longer.
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Smelting often requires an order of magnitude more energy than other steps. To ensure they are supplied by renewable energy, some smelters in China are discussing whether to transport entire operations to areas where the grid relies on renewables, Jones says, but none have moved yet.
Smelters are designed for constant power, but German firm Trimet has transformed some of its furnaces in an aluminum smelter to adapt to variable power. While smelters need to keep materials in a molten state, engineers add flexibility that allows the smelter to work with 25% less or 25% more power than typically used. When there is excess electricity available on local grids, sometimes a result of surplus solar and wind generation, process controls ensure that electrolysis chambers only freeze on the edges, allowing smelting to continue, albeit at lower capacity. In a sense, such a smelter acts as a form of battery on the grid.
“It can really be a significant contribution to stabilizing the grid, so we should not ignore that opportunity,” says Sævarsdóttir.
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While electricity is responsible for a quarter of the world’s emissions, industry is close behind at 21%, according the IPCC.
“Someone needs to work on the 21%. Everyone wants to work on renewable energy, but someone needs to work on this, otherwise we will not reach carbon neutrality… I think this is the biggest opportunity to help the climate.”