Thermoelectric solutions to generate electrical power from waste exhaust heat

Only a fraction of the energy released by burning fossil fuels is converted into mechanical or electrical energy, with most of the energy released as heat and written off as a loss. An EU initiative developed thermoelectric materials that may offer a solution to this energy problem.

Energy

While it has long been known that waste heat can be converted into energy, the efficiency of early thermoelectric power generation systems was so low that it limited their applications. The EU-funded project POWER DRIVER (An innovative environmentally friendly thermo-electric power generation system for automotive and marine applications that is powered by exhaust waste thermal energy to reduce fuel consumption) set out to design thermoelectric generators that could be mass produced for use in automotive waste heat recovery. Two small thermoelectric generators were designed: one based on silicide materials and another on telluride materials. Silicide and lead telluride-based materials were synthesised and then processed using spark plasma sintering to produce thermoelectric materials with performance comparable to that found in the literature. Separate joining techniques were developed for each generator based on the working temperatures that were calculated earlier for each module. A hot air exhaust heat exchanger was designed and optimised. This helped maximise heat transfer by not producing too much exhaust back pressure while maintaining positive net fuel economy. The team also designed, created and validated cooling plates. The thermoelectric devices were integrated with control and power electronics. The integrated automotive system was mounted onto a fully instrumented hot air test rig to simulate the exhaust of a two-litre gasoline car. Product guides were drafted and technology transfer events organised. A business plan focused on developing innovative core technology that will allow project partners to lead the development of thermoelectric generators in the automotive and marine industries. Other applications and target markets were also identified. The thermoelectric materials solutions require follow-up projects that will fully exploit and build on POWER DRIVER outcomes. Only then will the full socioeconomic and environmental benefits of a system for generating electrical power from waste exhaust heat be seen.