Wearable Solar-driven Pyro-thermoelectric Hybrid Generator

With the gradual development of smart wearable devices towards low power consumption and portability,the demand for flexible wearable micro-generators that can power them is also increasing.Among various power generation modes,the use of natural energy to generate electricity has the advantage of being environmentally friendly and clean.Thermal energy is a ubiquitous natural energy source,and wearable power generation devices based on thermal energy have broad research prospects.Thermal power generation technology can be simply divided into two forms.One is the pyroelectric effect that collects electrical energy through dynamic temperature changes,and the other is the thermoelectric effect that collects electrical energy through static temperature gradients.Traditional wearable generators usually consist of one of these two thermal power generation systems,so that the energy conversion rates are relatively low.Compared with the wearable thermal energy generator based on either the pyroelectric or the thermoelectric effect,the hybrid thermal energy generation system composed of the combination of these two effects can hold great promise for achieving higher power output capacity.Through ingenious structural design,temperature fluctuations and thermal energy can be obtained from the heat source at the same time,so as to better meet the power supply needs of low-power-consuming devices.Besides,for traditional wearable generators,their heating input commonly arises from the human body heat,but this is quite limited.With recent development of photo-thermal energy conversion technologies,solar energy could be possibly converted into thermal energy and utilized as a more sufficient thermal energy source.Based on these concerns,we successfully developed a novel wearable solar-driven pyro-thermoelectric generator by fabricating and assembling a high-efficient photothermal absorption layer,a pyroelectric generator and a thermoelectric generator.The research work carried out is as follows:(1)Novel wearable solar-driven pyro-thermoelectric hybrid generator was successfully designed and fabricated.From its top to bottom,this device consisted of three function parts,which included a photothermal absorption layer,a pyroelectric generator and a radiated thermoelectric generator.The photothermal absorption layer achieved energy conversion from solar energy to thermal energy,while the pyroelectric generator and the thermoelectric generator converted the temperature changes and the spatial temperature gradient into electricity,respectively.(2)The solar thermal absorption layer was composed of carbon nanotube(CNT)/carbon conductive adhesive(CT).It had a porous and rough microstructure and was conducive to the realization of multiple reflections of light inside the absorption layer.In the full solar spectral range,its absorption rate reached up to 98.9%.The pyroelectric generator was assembled with a poly(vinylidene fluoride)(PVDF)pyroelectric film,while under one sun illumination condition,its maximum power output density was 380μW/m~2.The thermoelectric generator was composed of poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate)(PEDOT:PSS)thermoelectric yarns.At a temperature difference of 9 K,the output voltage was～0.7 m V and the output power density of 1.4μW/cm~2.(3)The solar-driven pyro-thermoelectric hybrid generator was tested under both simulated and practical solar illumination conditions.Under 1.5 simulated solar light intensity,the hybrid generator successfully charged two commercial capacitors to 3.7 V within 800 s,and the total energy could light 73 LED bulbs.The hybrid generator was worn on a hat and exposed to sunlight for 30 minutes in a real outdoor environment.The hybrid generator charged the two capacitors to 2.5 V.These results demonstrated the practical application capability of the device.In summary,a novel solar-driven pyroelectric-thermoelectric hybrid generator was successfully developed by combining photothermal,pyroelectric and thermoelectric conversion technologies.This work not only provides a solution to the power supply issue of wearable electronic devices,but also opens up a new way to integrate various photo-thermal-electricity energy conversion technologies.