Earlier, the assumption was unused energy from the environment, machines, people, and so on could be used to power valuable devices and this would be done for free. The assumption was based on the convergence of four key technologies to enable mass adoption of energy harvesting—efficient voltage converters, efficient harvesting devices, low-power sensors, and low-power microcontrollers. However, it was soon realized that although energy harvesting does operate for free, the system needs investment, which is not free. That has led to the thinking that perhaps energy harvesting may not be the right technology for powering smart energy applications.
Now, with the growth of IoT devices, more sophisticated sensors, more pervasive connectivity, and secure, low-power microcontrollers, there are more devices to be powered than ever before. With most devices being small and battery powered, design engineers are facing challenges such as energy efficiency and long battery life.
In reality, it is no longer worthwhile using sensors for measuring and analyzing the energy consumption of individual light bulbs, since the cost of such a system would be more compared to the energy cost to run the lamp. In addition, there are numerous low-energy-consuming light sources available.
Development of engineering systems now place more emphasis on maximizing performance and saving energy. This is because most IoT devices spend a significant part of their life sleeping or hibernating, where the part is neither operating nor completely shut down. In this state, the device is actually drawing quiescent current, and this places the maximum impact on battery life, as it contributes to the standby power consumption of the system.
The development of nanoPower technology has led to great advancements in maximizing performance and saving energy. Newer products, with advanced analog CMOS process technology, now operate in their quiescent state with nanoampere currents that are almost immeasurable. The trick in maximizing energy-saving benefits from these products is first by duty-cycling them, and secondly by decentralizing the power-consuming architecture.
Benefits of nanoPower technology also extend to their ability to turn off circuits within the system. For instance, the nanoPower architecture may allow powering critical components such as real-time clocks and battery monitoring, while cutting off power to major consumers such as the RF circuits and the microcontroller, which can either turn off or enter their lowest power-consumption mode.
System monitoring ICs play a huge role here with their small packages and nanoamp quiescent current levels. Comparators, op amps, current sense amplifiers, and more help ensure important issues such as the voltage levels on microcontrollers are at proper levels. For instance, a nanoPower window comparator monitors the battery voltage and provides an alert if the battery voltage goes beyond allowable levels. Apart from being a valuable safety function, this also helps to extend the battery life, as the microcontroller need not operate until it has received an alarm from the comparator.
Another power-saving scheme is OR-ing the battery supply with voltage from a wall wart or an additional battery, using OR-ing diodes. These are Schottky diodes in series with the battery supply for limiting the voltage drop. For instance, MAX402000 diodes can save tens to hundreds of milliWatts of battery power when used in a smart way.