关键词: 智能可穿戴能源技术, 智能服装, 太阳能, 电磁能量, 电能变换, 纳电网

Abstract:

Objective At present, energy sources for wearable systems relies on chemical batteries or external power sources, which can bring inconvenience to the design and operation of the whole system, such as low energy supply, inconvenient charging and a lack of autonomous power supply for long periods of time. However, collecting energy from the external environment and the human body's daily activities to power wearable devices is a very promising solution. A nanogrid power system that integrate human wearable solar and electromagnetic energy harvesting devices is developed, aiming to solve the problems of low energy supply, inconvenient charging and poor user experience in the current power supply of wearable devices.

Method By integrating a highly efficient foldable solar cell and electromagnetic energy harvesting device, a human wearable nanogrid system integrating solar and electromagnetic energy harvesting devices was developed with the energy management circuit using SY3511 chip. The solar panel is glued to the experimental suit, and the electromagnetic energy harvesting device is glued to the tester's waist. According to the weather forecast data, the outdoor environmental conditions during the test are as follows: the temperature is 16 ℃, the weather is sunny, the wind is gusty, and the maximum wind speed is 32 km/h. The experimenter wore a test suit with the nanogrid system, and the voltage of the energy storage lithium battery is adopted to reflect the level of energy collected by the system.

Results The solar panels in the outdoor sunny state was shown to be able to directly achieve a stable voltage output of about 4.4 V, with a particularly smooth voltage waveform. The charging current of the lithium battery is about 50 mA, and accordingly the solar energy harvesting device provided a power output of about 200 mW during the daytime when the light is normal. During the human body movement, the magnet of the electromagnetic energy harvesting device was found to pass through the closed loop normally, and the amplitude of the induced alternating current electric energy was about 5 V, with the frequency of about 10 Hz. The diode rectified voltage is about 4.1 V, and the electric energy generated after shaking the magnet charges the energy storage battery. When the lithium battery was discharged to 0.6 V, about 1.5 h of normal human outdoor activities were able to charge the lithium battery to 3.7 V through the self-powered system, enabling the lithium battery for electrical energy output. Both energy collection modules were able to charge the lithium battery, the lithium battery would be able to charge the wearable device under unfavored environmental conditions. The conditions of the outdoor environment at the time of the test were as follows: the temperature was 16 ℃, the weather was sunny, with gusty winds and a maximum wind speed of 32 km/h. The results of a long test under these conditions showed that it took about 2.5 h to charge the mobile phone from 20% to 50%. The experimental results concluded that the wearable nanogrid system was able to harvest solar energy and electromagnetic energy, which verifies the feasibility of the wearable nanogrid system, which could be used for development and applications in wearable smart textiles in the future.

Conclusion Two forms of energy harvesting, solar and electromagnetic harvesting, are carried out through solar panels and electromagnetic energy harvesting devices, and energy management circuits are designed based on SY3511 to store the harvesting energy into a lithium battery. The test of the whole energy harvesting system shows that the designed wearable nanogrid can achieve the harvesting, storage, and output of energy enabling stable charging of cell phones for a long time. The feasibility of the wearable nanogrid system is also verified, which is expected to contribute to the development and application of wearable smart textiles in the future.

Key words: intelligent wearable energy technology, intelligent clothing, solar energy, electromagnetic energy, electric energy conversion, nanogrid