Restvarme

Restvarme, or residual heat, refers to heat energy that remains after a process or energy conversion and would otherwise be wasted. It is typically found in exhaust gases, hot water, wastewater, or ventilation air and is often at lower temperatures than primary heat sources. Recovering restvarme can reduce overall energy demand and associated emissions.

Common sources include industrial processes such as steelmaking, glass, cement, and chemical production; electricity generation exhaust streams; data centers where server cooling releases heat; and building ventilation systems or municipal wastewater networks. The temperature and quality of the heat influence how it can be reused and what technologies are appropriate.

Technologies forrestvarme recovery include heat exchangers and recuperators to transfer heat between streams, plate or shell-and-tube heat exchangers, and ventilation heat recovery systems. For lower-temperature heat, heat pumps or Organic Rankine Cycle systems can upgrade energy for reuse or power generation. Restvarme can be used directly for space heating or preheating of process streams, fed into district heating networks, or converted into electricity or cooling through appropriate cycles.

Benefits of recovering restvarme include lower primary energy consumption, reduced operating costs, and lower greenhouse gas emissions, along with potential improvements in process efficiency and system resilience. Challenges involve variable heat quality and availability, fouling and corrosion in heat-transfer equipment, capital costs, maintenance needs, and the need for integrated planning across processes and heating networks.