What is Energy Harvesting?
Energy harvesting is the process by which energy is derived from external sources (e.g. solar or light energy, thermal energy, and kinetic energy) and stored for small, wireless autonomous devices like those used in Wireless Sensor Nodes (WSNs).
Energy Harvesting Devices (EHDs) provide a very small amount of power for low-energy electronics. Solar modules are the most popular EHDs, since they are readily available, easy to use and low cost. The power generated is proportional to the the size of module and varies with brightness. Piezoelectric and electromagnetic EHDs generate AC power from kinetic energy such as vibration. They can generate large amounts of power with high voltage, but the challenge for these EHDs is to provide a vibration source of constant predictable frequency. Because of this, a typical application for a vibration EHD is attaching to a motor. A thermoelectric generator (TEG) can generate power with high current from heat. Similar to the vibration EHD, you have to ensure a constant temperature gradient for this device to provide usable power.
Energy Harvesting Power Management ICs (PMICs)
An Energy Harvesting PMIC is part of an Energy Harvesting System (EHS) that includes the EHD and a Storage Device. The PMIC receives the intermittent, very low-energy generated by the EHD and transforms that energy for storage in the Storage Device. The Storage Device, which is typically a battery, conventional capacitor, or supercapacitor, then is connected to the rest of the system, providing the power needed to operate.
The Energy Harvesting PMIC provides the following capabilities:
- Receives the intermittent, very low- energy from the EHD and transforms that extracted power into energy for the Storage Device. Depending on the type of EHD, the PMIC offers buck, boost, or linear DC/DC conversion.
- Manages the outflow of power from the Storage Device, while ensuring that power is not drawn when the stored energy is below a threshold value.
- Manages its own start-up sequence when sufficient energy is present.
Cypress has a full line of Energy Harvesting PMICs that are tailored to different application requirements.