Chapter 5 - Energy harvesting via human body activities

Abstract

Energy consumption in wireless sensor network (WSN) is one of the most critical issues. WSNs are conventionally battery operated sensor nodes which have short lifetime due to limited battery power and replacement of battery regularly is a costly and complicated task. Furthermore, in case of Wireless Body Area Sensor Network (WBASN), the problem arises due to its increasing cost and being uncomfortable in some cases (where replacement takes place). Energy harvesting is one of the solutions for any wireless network. There are several novel methods to generate energy from the environmental sources such as wind, solar, vibration, biological, and chemical. Besides these conventional sources, human body, with its many intended and unintended activities, is another source of energy. And it offers a reasonable solution to the issue in terms of renewable energy. Based upon appropriate power consumption from different harvesting methods, they can be used in a better way of required application. Human energy expenditure from different activities and how do we use that energy as electric sources and their power consumptions have been discussed here. The demand of a healthcare monitoring network with long life without replacement is also resolved by energy harvesting technologies. Here, first we have presented reviews on methods of energy harvesting techniques through human activities and, second, those technologies then would be used for biological applications (healthcare applications) as well as consumer electronics. Among all possible way of harvesting technologies (kinetic energy, biological fuel cell, and thermal energy), piezoelectric harvester technology becomes more appropriate model for powering sensors in biomedical implants, because it delivers tens of μW to few mW of power which fulfill the criteria of powering the sensor nodes. Adopting an advanced synchronized switched harvester on inductor (SSHI) makes the energy harvester more efficient and stable device. It gives a stable output and removes low voltage start-up problem and a good controller piezoelectric energy harvester. A brief comparison of various available energy harvesting technology and their power consumption for extending the battery lifetime has been presented.