We can use energy harvesting to provide electricity for items as small as cell phones or as large as satellites.

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The primary reasons for its usage are:
Convenience - Consumers wouldn't have to worry about changing or recharging batteries for devices such as laptops or cell phones or other electronic devices.
Backup Energy Sources - Such devices can serve as backups to primary power sources. This would increase their reliability, as a backup energy harvesting source would prevent power interruptions. This is important to operations such as hospitals that need energy even in emergencies such as blackouts.
Mobility - Wireless sensor networks can have mobile nodes that would still be secure, which is a useful feature for firefighters, the military, and law enforcement. By the same token, equipment that takes advantage of the networks would also be secure and mobile. One popular wireless network protocol is that from the ZigBee Alliance, which is developing a Green Power spec specifically for energy harvesting. This will allow devices such as sensors, switches, and detectors to harvest energy from solar cells, thereby precluding the need for batteries or connections to power lines.
Business Practices - Business costs for consumers would be reduced in terms of the packaging, development, disposal, longevity, and reuse of certain products. Product installation and maintenance would also have a reduced cost. An example is that of the costs that would be saved with the elimination of chemical batteries and rechargers, along with the extensive wiring they normally require, in the use of cell phones. There would be an automatic streamlining in their design, development, and packaging as a result.