Transient and power-neutral computing: a paradigm shift for embedded systems?

Embedded systems powered from time-varying energy harvesting power sources, for example solar PV or mechanical vibration, have traditionally operated using the principles of energy-neutral computing. That is, over a sensible period of time (e.g. 24 hours), the energy consumed is equal to the energy that was harvested. This has the advantage of making the system ‘look like’ a battery-powered system, yet typically results in large, complex and expensive power conversion circuitry and introduces challenges such as fast and reliable cold-start. In recent years, the concept of transient computing has emerged to challenge this, whereby low-power embedded systems can be designed to operate and perform useful computation when energy is available, and carefully ‘hibernate’ when the power disappears such that it can continue where it left off when supply is regained. In this talk I will explain this shift towards transient computing and the different approaches that have been proposed, and the new challenges that are raised as a result. I will also discuss a complementary approach to the powering of transient systems, named power-neutral computing. Instead of equating energy consumption to energy supply, as is the case in energy-neutral systems, power-neutral systems attempt to match instantaneous power consumption to the instantaneous power supplied. This fine-grained control permits better use of available resources while overcoming the disadvantages of energy-neutral computing; furthermore, it can work alongside aforementioned transient computing techniques if supply disappears altogether