NTNU BOX can work sustainably for ten years, without any battery replacement to achieve autonomy. Every 30 minutes, the temperature, humidity, and the remaining power of battery were sent to the cloud via Sigfox LPWAN (Low-Power Wide-Area Network).
The cloud data can be viewed here: http://flexwave.fox-tech.co/
Here is more information:
Applicable environment :
The place with light intensity of 1000lux. (Outdoor or indoor by window)
1. Size of box: 12cm(L) x 10cm(W) x 5cm(H)
2. Box wight: 200g
3. PV box power: 250mW (@ 1 sun condition)
4. Sigfox: RCZ4, M2COMM module, Sigfox LPWAN
5. Solar power management: MPPT charger to rechargeable battery with efficiency over 80%.
6. Temperature and humidity sensor: DHT22
7. Rechargeable battery: 18650 Li-ion rechargeable battery
8. Antenna: 920-925MHz.
PS. The monitoring time interval of the system is available to adjust according to requirements. The following figure shows the hardware adjustment method.