Wireless sensors and smart devices can be controlled by the internet anytime and anywhere with the IoT concept .Wireless sensor networks (WSNs) mostly seen in detecting events and identifying surrounding information. Since sensors which are in wearable devices are powered by portable battery , recharging the batteries of smart devices by home electricity is very hard to achieve.For the most of smart online operations, energy generating studies have recently been much attention through the research topics. Energy management is the most important technology for prolonging the network lifetime of WSNs. The design of efficient energy management involves several aspects, including physical, MAC and network elements as well as application aspects.Energy harvesting is a novel and promising solution that sees each node equipped with a harvesting module.
Recent research efforts in energy harvesting can be classified into two categories: energy scavenging and energy transferring. In energy scavenging technologies, the sensor can be recharged from the ambient environment, including electromagnetic waves, thermal energy and wind energy. In energy transferring technologies, the mobile node can play the role of charger which is able to wirelessly transfer energy to those sensors located within its recharging range.Low-power wearable may soon bid to batteries and start drawing energy generated by body heat and movement, and ambient energy from the environment. Consumer electronics devices are getting smaller but conventional batteries are not, and it’s important to start implementing new energy harvesting techniques to keep devices powered for long periods of time.
There will be billions of Internet-connected devices supplying real-time information in the coming year. Data-gathering instruments today are designed around the size of batteries, and self-powered devices could resolve some power and size issues.