Our vision for a smart office space is truly tether-less. A truly tether-less environment is free from wires not only for communication but also for power.
The idea of wireless transmission of power has been around since Tesla [Brown,McSpadden]. Modern applications that have been proposed range from beaming power by microwave to aircraft to beaming solar energy from stations in outer space to the ground. Indeed one could argue that almost all wireless communications are specific cases of wireless power transmission. Several applications of this technology ranging from electric power transmission to microwave beam powered aircraft have been publicly demonstrated. However the applications considered so far have been on a grand scale at power levels of 500 watts or higher. Proposals also have been made to build generating stations, using photovoltaics and other technologies, on the moon, on nearby asteroids or satellites, from where the power would be beamed down to earth.
At the other end of the spectrum, very low power and extremely short-range wireless powered devices are already in use in medicine. In certain surgical implants it is considered risky or undesirable to include batteries - an external battery carried by the patient is used instead to power the implant wirelessly. Contactless transfer of power to isolated integrated circuits by inductive means also has been proposed [Selvidge].
With increasing power efficiencies of semiconductor computing and peripheral devices, there is an incentive to power devices directly using radio frequencies (RF) which are currently being used for communications. Examples could be electronic product labels and price tags in supermarkets where battery-free operation would be ideal or an embedded temperature sensor in a smart office. Battery-free operation is very attractive considering that there would be fewer environmental side effects.
However, as appealing as the idea of eliminating the battery sounds at first, several applications require disconnected operation both from a wired or wireless power source as well as from the data network. We also have to be careful not to replace a dependence on batteries with a dependence on irradiation. It is more appealing to seek a hybrid approach that both provides power and also recharges an internal battery through wireless means. For example, consider that solar powered watches almost always have an internal rechargeable battery.