Siemens researching thermoelectric waste heat recovery for lower grade exhaust; industrial and mobile application

23 October 2012

Siemens is researching technologies that would allow waste heat from vehicles and industrial facilities to be used efficiently. To date, exhaust gas has generally only been used if it was hundreds of degrees Celsius hot. For example, the gas turbines in natural gas power plants produce exhaust gas that is used to generate steam for the operation of a steam turbine. The chemical industry, as another example, uses waste heat from reactions in order to preheat other substances, for example. However, the lower the grade (lower heat), the more difficult it is to use.

Siemens’ global research unit Corporate Technology (CT) is now investigating a number of possible solutions to this problem, including the use of thermoelectric generators to produce carbon-neutral electricity in environments with temperatures between 200 and 300 degrees Celsius. Although the technology has potential because thermoelectric components are inexpensive and can be mass produced, researchers have not yet been able to create materials that can achieve a sufficiently high level of efficiency within the stated temperature range.

One of the challenges that must be overcome before thermoelectric generators can be used for industrial applications is the development of materials that operate efficiently at temperatures above 200 degrees Celsius. New kinds of joining technology have to be developed as well because conventional welding techniques cannot withstand the high temperatures and large temperature fluctuations involved. To address these issues, Siemens is working together with colleges and industrial partners in the EC-funded NEXTEC (Next Generation Nano-engineered Thermoelectric Converters – from concept to industrial validation) project. A lab demonstration model is currently under construction at CT.

Another area of research is the use of thermoelectric generators in vehicles. Although diesel locomotives and trucks harbor the greatest potential in this regard, according to Siemens, the technology could also benefit passenger cars. In this field, Siemens is cooperating with automotive companies on the EU-funded HeatReCar project. Here, a prototype is being used to study the potential of recovering heat from a car’s exhaust.