Utilizing Solar Power: The Impact of a Small Panel on the Cortex-M — Part 3

February twenty-third, twenty twenty-four


Harnessing Sunlight: How a Tiny Panel Woke Up the Cortex-M — Part 3

This three-part series details a case study on the utilization of minute solar panels in powering IoT Devices. Be sure to peruse the lower section of the article for Parts 1 and 2!

Our investigation reveals that photovoltaic panels can be beneficial in specific IoT scenarios. In real-world applications, petite solar panels exhibit potential for various IoT devices. For instance, in smart agriculture, solar-powered sensors can monitor soil moisture and environmental conditions, harnessing sunlight accessible in open fields. In metropolitan environments, solar power can fuel smart parking sensors, which only necessitate sporadic bursts of power. Moreover, in remote monitoring applications, like wildlife tracking or forest fire detection, the minimal energy requirements of these sensors complement the capabilities of photovoltaic panels. Even in interior settings, low-energy devices such as temperature or air quality sensors can operate effectively in well-lit zones, utilizing indoor illumination. The crucial aspect is to pair the power necessities of the device with the anticipated energy yield from the PV panels, taking into account factors like device slumber modes and energy-efficient communication protocols.

Nevertheless, their prevailing capabilities are constrained by daylight hours and may not consistently provide dependable and perpetual power for a broader array of IoT devices, particularly in less optimal environmental conditions. Yet, with the proper configuration of the device’s computing power algorithms, continual operation solely on solar power is viable not solely during daylight time. Based on our investigation, we can derive critical conclusions regarding the applicability of tiny solar panels:

The Effectiveness of Voltaic Panels

The Voltaic P121 R1L panel exhibited high efficiency in intense sunlight, but its ability to preserve stable operation of IoT devices in less than ideal conditions remains uncertain. This is particularly notable if we intend to execute more intricate device modes, where the IoT board’s peripherals will be utilized more intensively, often with considerably higher power usage.

The P122 R1J panel, while suitable for particular applications, has extant limitations, particularly in less sunny conditions, and may only be suitable in particular circumstances where the IoT device necessitates a fusion of increased voltage with low current for rare and brief intervals of peak activity.

Versatility of the Epishine Module

This module demonstrated efficiency in dim lighting, rendering it potentially appropriate for indoor IoT applications. However, its capacity to maintain prolonged device operation without an additional power source is confined, particularly considering variable indoor artificial lighting conditions. Analogous to the Voltaic panels, uninterrupted power provision from a singular module will largely hinge on the proper power consumption settings of the IoT device itself, to use its peripherals and performance capabilities solely when genuinely needed.

PV Panel Type

Epishine Light Energy Harvesting Module

Voltaic P121 R1L

Voltaic P122 R1J

PV Panel Characteristics

Optimized for 20-1000 lux, Output Voltage: 1.8V to 3.3V, Output Current: up to 300mA

Max Power: 0.3 W, Voltage: 5.9 V, Current: 60 mA

Max Power: 0.32 W, Voltage: 2.3 V, Current: 150 mA

Capacitor Type

Onboard GA230F 400mF CAP-XX SuperCapacitor

Voltaic C116 with Vinatech 250F VEL13353R8257G Capacitor

Voltaic C116 with Vinatech 250F VEL13353R8257G Capacitor

Capacitor Characteristics

Energy Storage: 1.9Ws at 3.3V to 3.4Ws at 1.8V

Output: 2.5 to 3.8 V, Capacity: 250 F

Output: 2.5 to 3.8 V, Capacity: 250 F

Indoor Performance

Efficient in low-light conditions. Stores up to 3.4Ws. Operational time with maximum NRF52832 load: ~35s at 3.3V, ~145s at 1.8V.

Maintains sufficient energy output indoors with artificial lighting.

Enhanced efficiency with the capacitor, affording continuous power to NRF52832 in low light.

Outdoor Performance

Preserved operation in outdoor sunlight. Efficiency confirmed in diverse lighting conditions.

Generated ~120 mA under sunny conditions, surpassing NRF52832’s startup current of 70 mA.

Produced approximately 43 mA outdoors, inadequate to start NRF52832 without a capacitor.

NRF52832 Op Time with zero solar input (on the capacitor, hours)

More than 12



ATM3202 Op Time with zero solar input (on the capacitor, hours)

More than 18



Remark: The operational time for each PV panel and capacitor setup without solar input (e.g., nighttime) was computed based on the following working mode:

  • Advertising Mode: The device transitions to this mode once per hour for 5 seconds.
  • Connecting State: Immediately following advertising, the device engages in this state for 10 seconds.
  • Sleeping Mode: The device is in a low-power sleeping mode for the remainder of the hour.

These consumption rates were employed to ascertain the total energy usage per hour, which was subsequently juxtaposed against the energy storage capacities of the capacitors paired with each PV cell.

Role of Capacitors and Batteries

The utilization of supercapacitors and supplementary batteries as auxiliary power sources proved essential for upholding 24/7 IoT device operation where PV panels cannot furnish adequate power supply. We posit that PV panels with such integrated capacities, coupled with extensive options for adjusting output current and voltage, hold the most promise for further advancement and market enlargement in the context of integrating one module into one IoT device.

In a market where IoT necessitates increasingly intricate computing capabilities at the individual device level, exploration seeking the essential equilibrium between computational power and energy consumption will perpetually continue.

Solar panel manufacturers routinely proffer newer, more sophisticated, and efficient solutions. Such progressions will open up more prospects for employing diminutive solar panels in IoT devices, inherently prompting the exploration of leveraging heightened computing power at the device level. Hence, we perceive the ability to judiciously select, configure, and even innovate IoT devices as a pivotal element in this unceasing race.

A validation of our commitment to this domain is our recent triumph story. In this initiative, we furnished a client with an innovative solar-powered IoT device for ecological monitoring in urban regions. This device, adept at gauging air quality, noise pollution, and meteorological conditions, embodies a noteworthy leap in our endeavors to unite high-efficiency IoT solutions with renewable energy sources.

At Sirin Software, our aim is to cultivate IoT technologies that consume less energy while upholding efficacy. This encompasses fabricating sensors and devices that synergize well with the energy supplied by both current and forthcoming solar technologies. We persevere in pursuing future research to contribute to the advancement of renewable energy utilization for embedding eco-friendly technologies into our day-to-day routines.

Editor’s Comment: To access more details, peruse:

Valerii Haidarzhy, a seasoned tech author at Sirin Software, brings over 25 years of technical experience to his role, particularly enriching research through his collaboration with industry specialists and his personal investigations. His body of work spans a broad array of topics, with a focused expertise in Embedded Linux, the Internet of Things (IoT), and Hardware development.

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