10-01-2022 | | By Robin Mitchell
A recent development from e-peas demonstrates how energy harvesting can be highly advantageous in remote security applications. What challenges do remote devices face, what have e-peas demonstrated, and will energy harvesting play a vital role in tomorrow’s sensors?
When integrating technology into remote areas, several challenges quickly arise that are rarely seen in the office or home environments. One major challenge can be a lack of connectivity as Wi-Fi and cellular may be inaccessible. Some network technologies exist (such as LoRa), but even then, careful consideration has to be given to what connectivity technology is used.
The second major challenge is power. Homes and offices come with a wide range of power sources that can be tapped into, but remote locations can be utterly devoid of power. This leads engineers into deciding how their device will obtain power, whether it is via batteries or energy harvesting systems. Batteries can provide large amounts of current and voltage, but this comes at the price of requiring frequent charging. If a device’s location is so remote that it rarely sees human activity, having devices run on batteries can quickly become problematic.
The other option with power is energy harvesting, including solar, wind, stray RF, and mechanical movement. While this can provide power, it is often in extremely limited amounts, and thus designs need to be as energy-efficient as possible.
This is where the third challenge faced by remote designs comes in; energy efficiency. Regardless of whether a device runs on batteries or energy harvesters, both power sources will require a highly energy-efficient design. A battery design would require energy efficiency to help extend battery life, while an energy-harvester design would require energy efficiency to help operate on such small amounts of energy.
E-peas, a company that specialises in energy harvesting solutions, has recently developed and released a low-energy microcontroller specifically aimed at applications utilising energy harvesters. The new microcontroller, called the EDMS105N, incorporates a 32-bit ARM core clocked at 24MHz and has 256KB of flash combined with 32KB of SRAM and 8KB of deep-sleep SRAM. The current consumption of the EDMS105N is 18µA per MHz when operating in normal mode, and the entire CPUs current consumption during deep sleep is only 340nA.
The new microcontroller was demonstrated at CES2022 along with other power management and harvesting technologies produced by e-peas, including an AEM10941 power management IC and AEM30940 PMIC for RF energy harvesting. The demonstration showed how such an arrangement could be used to create a battery-free security monitoring system that counts the number of individuals walking past an area.
The use of the AEM30940 RF harvester allows a device to absorb energies in the frequency range of 0.4GHz to 10.6GHz. While such frequencies may not be commonplace in extremely remote areas, it is a very active band in areas closer to human activity, such as towns and cities. The use of an omnidirectional antenna also allowed the demonstration device to absorb RF in all directions, which can be highly beneficial in applications that need to be installed and forgotten.
The attitude towards energy harvesters has taken an interesting turn, and if energy efficiency in microcontrollers continues to improve, then energy harvesters could become a dominant energy source. In the past, energy harvesters have often been looked at as niche energy sources that can power one or two unique projects. This has generally been a result of the large amount of power needed by microcontrollers. However, as energy-efficient microcontrollers become a reality, the tiny amounts of energy provided by energy harvesters will soon become more than sufficient for typical operation.
Furthermore, the increased use of radio technologies gives energy harvesters more sources of power. Compared to 20 years ago, the use of radio has increased dramatically. The addition of many millions of devices all help create a radio spectrum that is plentiful in energy (keep in mind that this “plentiful energy” is subjective).
However, it should be understood that devices such as smartphones will never be powered using energy harvesters, and devices that do will be used to monitor the environment and transmit small amounts of information. This doesn’t mean that energy harvesters are useless; it simply means that they will only be used in low-energy applications.
Of all potential applications for energy harvesters, it is most likely that they will most likely be used in smart city projects that connect thousands of buildings and roads together for the sake of environmental monitoring. Such sensors can easily be placed on the sides of buildings and underneath roads without needing a power source or internet connection. Their close proximity to one another could help create low-power mesh networks that keep these devices connected.