In 2013 ETC released a White Paper written by Bryan Palmer on Daylight Harvesting Methods and Practice, which is still useful today.
Daylighting for energy savings and conservation has become common design practice. Daylight harvesting is something that is required by some energy codes, and soon to be adopted by others. Instead of being encouraged by energy programs, it’s becoming required. California’s Title 24, IECC 2012, and ASHRAE 90-1 already have daylighting guidelines; and they are likely to become more stick over the coming years. Most commercial buildings that have windows and skylights are required to have some type of daylight harvesting control in the adjacent area. Green sentiment and construction practices bring additional attention to energy saving practices like Daylighting, help to further acceptance of the practice, and grow the technology that makes it possible Daylight harvesting’s proposed value is simple: As natural light levels increase, electric light levels can be decreased to maintain an acceptable level of light in a space, and save energy (and money). Daylighting systems automate this process, removing the human element of control by using a light sensor that measures light levels and sends them to a controller that is connected to the lighting control system. The control system can then dim or switch electric lights in response to the measured level. The light sensor is typically small, and uses a light-sensitive photocell, input optics and an electronic circuit used to convert the photocell signal into a control signal. Light Sensors may be mounted on walls, ceilings and even as a part of light fixtures.