While the potential applications of the Internet of Things are many and varied, they do share some key characteristics. The devices that collect the data need to be small, easy to use and available almost all the time. These requirements are perhaps most readily apparent in the wearable devices that are already used by millions of people around the world to track their activity, monitor their fitness and improve their well-being.
To collect the necessary data, wearables need to be worn almost constantly. Hence they need to be small and comfortable and they need to be capable of operating continuously for long periods. Smart home sensor nodes and other Internet of Things applications face similar demands.
That raises the question of how to power these devices. Ideally, they would draw energy direct from their environment so that they would always have power. While great strides are being made in reducing power consumption and improving energy harvesting, this ideal remains some distance off. For the foreseeable future, we will need to rely on batteries as the primary power source. In particular, to minimize waste from the billions of devices, rechargeable batteries are likely to be the power source of choice for some years.