Thermoelectric energy harvesting is a failure when set against the publicity of participants over the last 30 years. "The roaring mountain gave forth a mouse". Current versions do not scale above kW and are rarely used above mW - serious because the market for energy harvesting above 1W is about 100 times the value market below.
Dr Peter Harrop, leading author of the IDTechEx report, Thermoelectric Energy Harvesting 2018-2028: Applications, Markets, Players advises, "We scour the universities and company research labs and we see nothing that encourages us to say that huge sales of high power thermoelectrics are round the corner. Indeed, the window of opportunity for thermoelectrics producing a useful 1kW on a car exhaust pipe has now gone with the advent of mild and full hybrids with much cooler exhaust and pure electric vehicles with no pipe at all. For wearables, thermoelectrics tend to be too expensive. The Seiko thermic watch years ago was withdrawn because it did not function well. And yet! A breakthrough is likely in affordable flexible thermoelectrics providing micro to milliwatts, notably working at room temperature. Based on the research pipeline, we forecast flexible thermoelectrics rising to 12% of the steadily growing thermoelectric harvesting business in 2028."
IDTechEx is seeking to validate information from within a major watch manufacturer that it will launch a thermoelectric watch. Flexible thermoelectrics is often requested for wearable and autonomous embedded devices: sensors, indicators, actuators, in the move from components-in-a-box to structural electronics. The IDTechEx report, Smart Materials as Structural Electronics 2019-2029 embraces optics, electrics, magnetics etc. in flexible, load-bearing protective or decorative coatings: a technology megatrend.
For flexible thermoelectrics, organics and inorganic/organic hybrids now look good. PEDOT:PSS, polyaniline, polypyrrole and certain fluoroelastomers are being trialled. The IDTechEx report, Fluoropolymers for Emerging Electronics and Electrics 2019-2039 puts those in context. Greater power is promised from more complex approaches to inorganic/organic hybrid thermoelectrics: organic/inorganic laminates and intercalation of organic molecules in layered inorganic compounds. Delightfully, the power required in envisaged applications is plummeting with frugal new electronics and electrics. The task just got easier.