Thermoelectric waste heat harvesting in aero engines
In the LuFo TERA project, which was completed in 2017, the potential of mission fuel savings by transforming engine waste heat to electrical power was investigated. To this end, thermoelectric generators (TEG) were considered, which – without the need for moving parts or working fluids – convert a heat flux over a thermal gradient to an electric current. The load reduction on the conventional generators leads to higher engine efficiency and supports the progressive electrification of aircraft. As the conversion of waste heat is a downstream process, it may, in principle, be applied to any type of heat engine, including aero engines.
In order to evaluate the technology, a reference aircraft was defined to determine the impact on mission fuel consumption. At the considered place of installation, a positive, but small potential of the order of 1 ‰ was determined (typical TEG power << 10 kW, see top figure right). The area available for integration, system mass as well as local thermal conditions all have an influence on the overall potential, so these factors may be further optimised. One option that promises improved thermal conditions as well as higher output power densities is to consider placement within the hotter engine sections (see bottom figure right). Based on these and other insights, recommended actions for technology development were derived, which were recorded in the form of an R&D roadmap as part of the project report.
Das zugrunde liegende Vorhaben wurde mit Mitteln des Bundesministeriums für Wirtschaft und Energie unter dem Förderkennzeichen 20E1303 gefördert.
- Mission fuel savings potential: The minimum required power density is below 200 W kg-1, whereas TEG modules may provide up to 500 W kg-1. A theoretical TEG with 10 kW output power could reduce mission fuel by around 1 ‰.
- Potential for thermoelectric energy harvesting on engine level: For defined sections within the engine, the achievable power was determined based on fluid mechanics calculations (H/LPT: High-/Low-Pressure Turbine). At the nozzle, an area of 2.4 m² was assumed in this case.