Abstract
Ambient light is an energy-harvesting source that can recharge a battery with less human interaction and can be used to prolong the operational time of the Internet of Things, e.g., mobile phones and wearable devices. Available light energy is insufficient for directly charging mobile phones and wearable devices, but it can supplement batteries to power some low-energy-consuming critical functions of the wearable device, especially in low-power consumption wearables. However, in an emergency scenario when the battery’s operational time is not sufficient or a battery charging source is unavailable, a solution is required to extend the limited battery span for mobile and wearable devices. This work presents the bottlenecks and new advancements in the commercialization of photovoltaics for smartphones and wearable technologies based on ambient light energy harvesting. A new technique, in which a smartphone cover is used as a solar concentrator to enhance light energy harvesting associated with algorithms, is experimentally demonstrated. Our research outcomes show that solar concentrators can improve light intensity by approximately 1.85 and 1.43 times at 90° and 71° angles, respectively, thus harvesting more ambient light energy at 2500 lx light intensity in a typical office environment. Type-1 PV and Type-2 PV cells were able to charge the additional battery in 8 h under 2500 lx lighting intensity in an indoor office environment. A system and logic algorithm technique is presented to efficiently transfer harvested light energy to perform low-energy consumption operations in a device, in order to improve the operational time of the device’s battery.
Highlights
New technologies integrate information and data into our lives using sensing, smartphones, and wearable devices
Previous studies discourage the possible applications of currently available solar cells in smartphones and IoT devices, but consider PV energy charging with a supplemented operating system (OS) in low-power mode that can enhance the user’s experience, behavior, and utility [49,50]
In contrast to the traditional photovoltaic-based battery charger, which charges mobile phones using a USB port, this work emphasizes a simple approach where PV is an integral part of the smartphone and its wearable device
Summary
New technologies integrate information and data into our lives using sensing, smartphones, and wearable devices. PV energy harvesters can be used to supplement external battery charging [48] This can be helpful in a scenario where low-power devices record and wirelessly transmit data after a long (~10 s) time interval [48]. Previous studies discourage the possible applications of currently available solar cells in smartphones and IoT devices, but consider PV energy charging with a supplemented operating system (OS) in low-power mode that can enhance the user’s experience, behavior, and utility [49,50]. We use a commercialized PV cell, small enough to be installed on a smartphone or wearable device surface, and analyze their output power under indoor light conditions.
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