Building a Foundation for Sustainable Construction MaterialsPosted to Electric Power Research Institute (EPRI)
image credit: EPRI: An electric arc furnace for steel production
- Oct 16, 2020 9:11 pm GMTOct 16, 2020 4:41 pm GMT
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In recent decades, advances in heating, lighting, and building envelope technologies have driven impressive gains in building energy efficiency. Yet, there is still much room for improvement with respect to energy use associated with buildings.
According to a recent report from the United Nations Environment Programme and the International Energy Agency, buildings accounted for 36% of the world’s final energy use and 39% of energy-related carbon dioxide emissions in 2018. One area with significant potential for reducing energy use is the materials that go into the world’s buildings. The same report indicated that production of building construction materials such as steel, glass, and cement accounted for 9% of the world’s final energy use and 11% of energy-related carbon dioxide emissions in 2018. The main reason for these high numbers: the manufacturing processes require high-temperature industrial heat typically generated by burning coal and natural gas.
Electric Arc Furnaces to Produce Steel
About 70% of the world’s steel is produced by heating iron ore with coke (a high-carbon fuel made from coal) in a blast furnace. Heat is provided by combustion of coke. The process results in molten iron that can be formed into steel.
The remaining 30% of the world’s steel is produced in electric arc furnaces—a technology in use since 1907 that heats recycled scrap metals using electrodes charged with AC or DC electricity. The electrodes are positioned close enough to the metal to create an arc that melts the metal, which is then formed into steel.
Relative to blast furnaces, electric arc furnaces use one-tenth the energy to produce the same amount of steel. The capital costs of arc furnaces are also lower than blast furnaces. According to the industrial gas company Air Products and the metal flow engineering company Vesuvius, the capital investment required for a traditional blast furnace is $1,100 per ton compared to under $300 for an electric arc furnace.
Blast furnaces typically run continuously because it is too expensive and time-intensive to turn them on and off. Arc furnaces can be easily turned on and off in response to the demand for steel, reducing operational costs. With coal plants closing at a record pace, coal production may decline, which could drive some steel producers to transition to electric arc furnaces.
A potential downside of electric arc furnaces is their reliance on recycled raw materials that fluctuate in cost and availability. Arc furnaces also require significant electric infrastructure. “These facilities have 15- to 30-megawatt loads and may need dedicated substations or even transmission-level service,” said Baskar Vairamohan, principal project manager in EPRI’s Electrification program. “The industrial customer often has to build a substation or expand its own infrastructure to power the electric arc furnace.”
Sometimes, high costs of upgrading facility infrastructure can make the project economically unfeasible. However, utilities can help by sharing the costs of the additional infrastructure or by offering incentives, such as a reduced electricity rate for the first few years or a rate that doesn’t include demand charges (which are based on a facility’s maximum hourly power needs) for a certain amount of time.
Electric Resistance Heating to Make Glass
Glass is made by melting a mixture of sand, soda ash, limestone, and recycled glass in a furnace at more than 3,000°F. Once melted, the liquid glass can be poured on top of flat metal surfaces to make windows. According to the U.S. Energy Information Administration, natural gas accounts for 73% of the fuel used to provide heat in U.S. glass production.
Electric resistance heating offers potential advantages over natural gas heating. With this technology, current runs through electrodes immersed in the sand mixture, directly heating the mixture. In contrast, natural gas furnaces heat both the sand mixture and the surrounding air, so there are greater heat losses. Electric heating has a thermal efficiency nearly double that of natural gas heating—and it uses about 35% less energy. It requires less maintenance and has much lower carbon dioxide, nitrogen oxide, and sulfur oxide emissions. With electric heating, a facility can adjust temperatures more quickly, enabling production of different glass products requiring different heat regimens.
A cost comparison between natural gas versus electric resistance heating in glass production can vary depending on site-specific factors. While higher cost electricity in some regions can reduce the competitiveness of electric resistance heating, superior energy and thermal efficiency can partially offset the advantage of natural gas. Although electric heating systems have lower upfront costs than their natural gas alternatives, they last between 2 and 7 years compared to 10 or 20 years for natural gas furnaces.
In Europe, the majority of glass is made using electric resistance heating. According to a report by Lawrence Berkeley National Laboratory, Norwegian glass manufacturer Moss Glassverk’s switch from natural gas to electric that resulted in a 64% annual energy savings and payback of 1.5 years.
“Europe uses a lot of electric technologies in part because European regulatory bodies are enforcing low-carbon rules,” said Vairamohan.
Utilities can provide glass manufacturers with outreach and education on the benefits of electric resistance heating. “Often when it is time to replace equipment, companies purchase a newer version of the same product because they know it works,” said Vairamohan. “A different product may not be considered unless someone explains why it is better over the long run.”
The barriers to electrifying steel and glass production are significant. In a 2019 report on industrial heat decarbonization, the Innovation for Cool Earth Forum noted that core components in industrial facilities can cost hundreds of millions of dollars and may take 30-60 years to replace, with some facilities operating more than 80 years and still making revenues. Because construction materials are commodities traded on global markets, even small increases in production costs can result in a significant loss of sales for the producer. The report points to ways that national and state governments can address these and other barriers, such as standards for procurement of construction materials and financial incentives for capital expenses.
This article appreared in the September issue of EPRI's Efficient Electrification newsletter. To sign up to receive future issues, visit: https://www.electrificationcommunity.com/contact-form.