Thermoelectric energy harvesting increasing in automotive

  • December 29, 2014
  • News

December 29, 2014 - Up to 2014, there was only limited interest in thermoelectric energy harvesting in general and its use in automotive applications in particular. For instance, BMW had worked on it for 20 years without bringing anything to market. The theoretical maximum attainable efficiency was known to be one half of that for photovoltaics and some other options and the actual achievement was around one tenth of theoretical at 3% or so.

However, 2014 saw a sharp change in attitude. For example Komatsu KELK in Japan had trialed 1.5 kW thermoelectric modules on its huge construction vehicles showing that thermoelectric harvesting was no longer just about providing signal power. It had been most widely deployed by the EnOcean Alliance for tiny bursts of UHF signal to operate wireless, batteryless building controls where they were on heating radiators - EnOcean almost entirely uses only electrodynamic and photovoltaic harvesting on its devices. The thermoelectrics was just a back story.

Another pivotal occurrence was Komatsu and others more than doubling efficiency of its thermoelectric devices to up to 7.5%, at least for the smaller ones; for example, creating electricity from electronic components that run hot. Schneider Electric started to use them on wireless sensors triggered and powered by heat outages on such things as copper power busbars.

Thirdly, the day was getting close when thermoelectric energy harvesting on hybrid electric engines and exhausts would be viable. In IDTechEx visits to AIST in Japan, Komatsu KELK in Japan and the National Physical Laboratory in the UK (Dr Alexandre Cuenat working on standard tests and new devices) plus various electric vehicle events in Europe and the USA in 2014, the message was the same: thermoelectric energy harvesting will be in on-road vehicles in 2018. The only disagreement was whether hybrid cars would be first to adopt them or buses because they are sold not on up-front price but on cost of ownership and green credentials.

We enter 2015 with the following view at IDTechEx, "Thermoelectric energy harvesting will be on production hybrid electric on-road vehicles from 2018." It will be commonplace on hybrids in 2020 and almost entirely to charge the battery, or increasingly supercapacitor or supercabattery used for power. There will be little use on wireless devices through the vehicle because the necessary heat differences will not exist where most of these are positioned. Logically thermoelectric energy harvesting should go on large vehicles first including military ones because the increased efficiency does not just save money, it eases the problems of fuel logistics (the US Military plans 70% reduction in fuel consumption for this reason) and security of propulsion.

IDTechEx believes that hybrids will outsell pure electric vehicles that do not have adequate heat differences for thermoelectrics, until 2030 so the market is ongoing. We expect thermoelectrics to remain the only form of energy harvesting where the material cost is not the largest component of cost though work is ongoing to make these elements by additive processes instead of the current micro-machining. One implication is that the materials can be very profitable due to limited price sensitivity and breakthroughs such as less toxic materials and formable materials will be greatly valued. The addressable automotive market is therefore primarily hybrid cars for charging and that is around 9 million units in 2025 if paybacks are established.

Conventional cars?

More speculatively, conventional cars, which will still be the majority of cars made in 2025, are incorporating more and more energy harvesting to reduce fuel usage since the starter heating Ventilating Air Conditioning HVA batteries can be loaded at up to 500W in them these days. Some stop-start is electromechanical energy harvesting and some alternators work backwards in an equivalent of regenerative braking in EVs. It is therefore possible, but by no means demonstrated, that thermoelectric energy harvesting on all those hot conventional engines may prove viable adding tens of millions to our figure for addressable market in 2025.

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