Wireless Sensor and Actuator Networks for Lighting Energy ...

e used to control the lights in areas receiving similar amount of daylight so as to ensure
the same light level within the controlled zone. The locations of the photosensors need
to be carefully chosen according to the type of control algorithms to maintain the
required task illuminance. Commissioning the daylighting systems requires expertise
and is time-consuming, especially for calibrating the photosensors to respond correctly
to the light changes on the workplanes [27]. Various factors have to be taken into
account in order to result in good performance. These include the reflectance of the
furniture and interior, the ceiling/task illuminance ratio, the incident angle of daylight,
the maximum possible reception of daylight, etc. The extra commissioning expense on
top of the high installing/retrofitting cost makes the already expensive daylight
responsive systems even more economically unattractive.
Light level tuning only works for private offices with a single occupant, since
current technology on the market cannot balance the competing lighting preferences of
multiple occupants. Therefore, it is not possible to satisfy each occupant’s lighting
preference with this control strategy in shared-space offices, let alone generate energy
savings. For the occupancy sensing technology, unwanted switching off while people
are present has always threatened to render the sensing system obsolete. People would
rather rollback to manual switching of the lights than be bothered by the sudden falseoffs,
and consequently energy savings are jeopardized. The initial cost is also identified
as a barrier to the wide adoption of this technology [19, 25, 26].
In summary, exorbitant initial costs, complicated implementation, and
commonly poor performances prohibit daylight harvesting control strategy from
widespread adoption. Moreover, a lack of proper technologies renders energy savings
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