Physics / mechanism
Energy harvesting converts ambient environmental energy—thermal gradients, mechanical vibration, RF fields, or photons—into usable electrical power. Core mechanisms: thermoelectric (Seebeck effect, ZT ≥ 1.5–2.0 in best-in-class BiTe alloys), piezoelectric (PZT, AlN on MEMS; output 10–500 µW/cm² at resonance), photovoltaic (indoor OPV/perovskite reaching 25–30% under fluorescent spectra), and RF rectenna (sub-µW to low-µW at –20 dBm input). Target envelope: µW to low-mW continuous power for always-on IoT nodes, wearables, and distributed sensors. Key constraint is power density vs. source intermittency; duty-cycled loads and ultra-low-power MCUs (sub-µA sleep) define the system budget.
Competitive landscape
Primary competition is the coin cell and thin-film primary battery—cheap, predictable, but replacement-cost-heavy at scale (billions of nodes). Secondary competition: energy-dense rechargeable (LiFePO4 micro-cells) combined with BLE duty cycling, which often beats harvesting on $/node deployed. Adjacent spaces include wireless power transfer (AirFuel, Qi, long-range RF beamforming) and fuel cells for industrial sensors. Material adjacencies: GaN-on-Si for rectenna efficiency, AlScN piezo films (higher coupling coefficient than AlN), and halide perovskite for flexible PV.
| Approach | Power density | Lifetime | Integration cost |
|---|---|---|---|
| Thermoelectric | ~50 µW/cm²/K | >10 yr | Medium |
| Piezoelectric MEMS | 10–500 µW/cm² | 5–10 yr | Low–Medium |
| Indoor PV (OPV) | 20–100 µW/cm² | 3–7 yr | Low |
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.