Using a supercapacitor for power management and energy storage in IoT

http://www.edn.com/design/power-management/4458294/Using-a-supercapacitor-for-power-management-and-energy-storage-with-a-small-solar-cell–Part-1

The environment has abundant energy but little power. Energy harvesting can tap the environment’s “infinite” source of energy, and avoids the cost of wiring to mains power or replacing of batteries. This article will look at using small solar cells. 
Depending on the light level, whether indoors or out, small solar cells may deliver sub mW to 10′s of mW. 

The peak application power needed for wireless communications may range from ~50mW for Bluetooth to ~7W for cellular transmission. So the problem becomes how to power wireless transmission. Supercapacitors solve this problem playing the roles of temporary energy storage and power delivery.

As an example, assume a remote location is reporting its status once per hour using an SMS that takes three seconds to transmit on a GPRS cellular network. The peak output power is ~7W. For GPRS class 8 (single slot transmission), the average power  = 7/8W and over three seconds ~2.6J of energy.