What is Daylight Harvesting?
Daylight harvesting is when buildings are designed around maximizing natural light in order to minimize energy costs and improve wellness. Commercial buildings consume 23% of their electricity from lighting; schools and hospitals consume 42%. By utilizing south-facing windows and skylights, artificial lighting can be dimmed or turned off all together; also lowering temperatures and cooling costs.
To fully optimize the energy saving potential, daylight sensors are applied. The automated lighting system then adjusts the lights to the appropriate lumens based on the available daylight. These sensors can be mounted in the wall, ceiling, or on any work surface to ensure you always have the perfect amount of light needed.
Types of Daylight Harvesting
- Open-loop systems monitor only the natural light, and do not count the electric lighting contributions. In this case the sensor is mounted on the building exterior or facing outward near a window or skylight. Because there is no feedback from the electric light, this is considered an open loop. These systems are often preferred for less accurate applications like hallways or parking garages. Open loop systems are typically set-up by programming set points that activate specific presets. As the light level changes to a specific range, the electric light output is adjusted to an appropriate level.
- Closed-loop systems measure the combined input from both natural and the electric light. Because the sensor measures both sources of light output, it needs to be located accordingly. It then gives itself feedback, making a closed loop, and a more accurate system. Each sensor controls its own zone, and must be appropriately calibrated to avoid frequent dimming or switching. Closed loop systems are commonly used for specific lighting levels like small offices, classrooms, or homes.
Whether you have new building, or are retrofitting an existing one, daylight harvesting can be implemented to save money on energy and cooling, and enhance wellness.