NESL Technical Report #: 2006-3-2
Abstract: Power management is an important concern in sensor networks, because a tethered energy infras- tructure is not available and an obvious concern is to use the available battery energy e±ciently. However, in some of the sensor networking applications, an additional facility is available to ame- liorate the energy problem: harvesting energy from the environment. Certain considerations in using an energy harvesting source are fundamentally di®erent from that in using a battery be- cause, rather than a limit on the maximum energy, it has a limit on the maximum rate at which the energy can be used. Further, the harvested energy availability typically varies with time in a non-deterministic manner. While a deterministic metric such as residual battery su±ces to characterize the energy availability in the case of batteries, a more sophisticated characterization may be required for a harvesting source. Another issue that becomes important in networked systems with multiple harvesting nodes is that di®erent nodes may have di®erent harvesting op- portunity. In a distributed application, the same end-user performance may be achieved using di®erent workload allocations, and resultant energy consumptions, at multiple nodes and in this case it is important to align the workload allocation with the energy availability at the harvesting nodes. We consider the above issues in power management for energy harvesting sensor networks. We develop abstractions to characterize the complex time varying nature of such sources with analytically tractable models and use them to address key design issues. We also develop distributed methods to e±ciently use harvested energy and test these both in simulation and experimentally on an energy harvesting sensor network, prototyped for this work.
Public Document?: Yes
NESL Document?: Yes
Document category: Report