Building a Light Energy Harvesting Product

A light energy harvesting (LEH) product converts ambient indoor light into usable power, letting a device run for years with no batteries to replace and no cables to install. But the device is never defined by the solar cell alone. True energy autonomy comes only when the solar cell, power management, energy storage, microcontroller, communication, and software are designed together as one integrated system.

How a light energy harvesting system works

Ambient light is captured by the solar cell and converted into electrical power. This energy is routed through a power management unit, which regulates and optimizes the energy flow before storing it in an energy storage component, typically a rechargeable cell or a supercapacitor.

The stored energy powers the microcontroller, which manages the system. The microcontroller communicates with the sensors in the product, runs the device logic, and acts as the communication manager toward the outside world.

Finally, a radio, either built into the microcontroller or a separate chip, transmits that data using a low-power protocol such as Bluetooth, Zigbee, Sigfox, mioty, or LoRaWAN.

Key considerations when designing an LEH device

Designing a light energy harvesting device involves several considerations, such as understanding what the application needs, the environment the device will operate in, how it integrates into the product, and how the components work well together.

1. Application needs
   Define how the product will be used and how often it needs to process and transmit data, as these factors determine the energy demand. Wireless communication is one of the most energy-consuming functions, so consider carefully how often data needs to be sent.

2. Operating environment
   Consider where the device will be installed to understand the light availability that can be harvested. Indoor light levels vary widely, so design around the real conditions at the installation point rather than ideal light.

3. System goal
   Clarify whether the objective is a fully energy-autonomous system or simply an extended battery lifetime. This guides the architecture and the design decisions that follow.

4. Product integration
   Consider how the solar cell will fit into the final product design. Because the cells are thin and flexible, they can follow curved designs or be built in as an interactive surface.

5. Minimize quiescent current
   Reduce all continuous power consumption. Any leakage or quiescent current, components that draw power even when inactive, can significantly affect the energy a low power electronics design needs.

6. Maximize time in sleep mode
   Keep the system in sleep mode as much as possible. Active operation should occur only when necessary.

7. Optimize the system as a whole
   Performance depends on how well the solar cell, power management, energy storage, microcontroller, and radio work together, and on how well they are matched to the application and operating conditions.
   

From light to a self-powered product

Design with these considerations in mind, and a light energy harvesting device can run quietly for years on indoor light alone, powering sensors, asset trackers, electronic shelf labels, and other connected products without a single battery change. The result is lower maintenance, less electronic waste, and a device that takes care of its own power.