Designing energy-aware sensor systems

Owing to constraints on physical size/weight, the energy capacity of the battery in sensor nodes is typically limited. Hence, energy optimization can either increase the lifetime of the node or enable more powerful operations at a sensor node. In order to tackle the limited battery capacities, many sensors scavenge energy from the external environment in addition to using batteries. However, the amount of power that can be harnessed this way is very limited (typically, in the range of 100 mW). Therefore, energy optimizations are important even in these environments. Energy consumption has a significant impact on the weight of the battery pack and consequently of the entire sensor node. For example, to limit the recharge interval to 10 h, it requires a 0.5 lb battery to operate a system that consumes 1W.1