Reliable Energy Sources as a Foundation for Reliable Intermittent Systems

This paper defines architectural and operational principles for simple and reliable energy harvesting devices that can be used in service of high-level applications. For many maintenance and monitoring tasks, we propose that it is more valuable to have reliable, trusted affirmations that nothing has changed than it is to know the exact moment that something has failed. This presents an opportunity for a new class of highly reliable, but not necessarily timely, intermittent devices. These are devices that are capable of sending messages at reasonable, fixed intervals (e.g. once an hour or once a day). They cannot activate more often, but they also promise not to activate less often. To establish this reliability, we look to opportunities for energy scavenging that are often ignored as their instantaneous power delivery capability is very limited. However, unlike higher power scavenging opportunities, many of these sources are not intermittent. Such sources may provide less than a microwatt, but their trickle of energy will be continuously, reliably available for months to decades. This enables the creation of devices that can be guaranteed to activate at predictable intervals, which allows for the construction of non-intermittent systems atop intermittent devices.