What is Exergy
At The ESG Institute, we believe that advancing sustainability starts with understanding the language that shapes it. Our "ESG Terms" series breaks down complex, often overlooked concepts in sustainability and Environmental, Social, and Governance (ESG) reporting—so you can stay informed, inspired, and one step ahead in your journey toward responsible business.
What is Exergy?
Exergy refers to the portion of energy in a system that is available to perform useful work. Unlike total energy, which includes unusable waste heat, exergy measures the actual potential of an energy source before inefficiencies reduce its effectiveness.
🔺 Why It Matters: Traditional energy efficiency focuses on reducing consumption, but exergy efficiency goes a step further—it identifies how much of the energy input is truly useful. By minimizing exergy losses in industries, power generation, and buildings, we can significantly reduce waste and optimize energy use.
🔺 Example: A power plant may have a high energy input, but only a fraction of it is converted into electricity—the rest is lost as heat. By capturing and repurposing this waste heat (e.g., in district heating systems), the exergy efficiency improves, making the entire process more sustainable.
🔺 Did You Know?: a report by the U.S. Department of Energy (DOE) estimates that between 20% to 50% of industrial energy input is lost as waste heat in the form of hot exhaust gases, cooling water, and heat lost from hot equipment surfaces and heated products. Additionally, a study published in Geoderma indicates that approximately 72% of global primary energy consumption is lost after conversion, with 63% of the considered energy being lost as waste heat.
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