What is Daylight Harvesting?
Daylight harvesting, also known as daylighting control, is an automated lighting control strategy that reduces energy consumption by using natural light to illuminate a space. Instead of keeping electric lights at 100% brightness all day, a daylight harvesting system intelligently dims or turns off artificial lights when sufficient sunlight is available from windows, skylights, or other openings. This goes far beyond simple on/off occupancy sensors; it provides continuously optimized light levels, creating a more efficient and comfortable environment.
For facilities like warehouses, distribution centers, and manufacturing plants with high ceilings and skylights, the potential for savings is massive. Traditional metal halide (MH) or high-pressure sodium (HPS) fixtures lacked the ability to be dimmed intelligently. Modern LED UFO high bay lights, however, are perfectly suited for this technology. They are often equipped with 0-10V dimming drivers, allowing a control system to smoothly adjust their output from 100% down to 10% or even off, based on the amount of ambient light detected by a photosensor.
This approach directly tackles a major operational expense. A common mistake I see is facilities upgrading to LEDs for the initial efficiency gain but failing to implement controls. They leave money on the table every single day. By integrating daylight harvesting, you unlock the full economic potential of an LED retrofit, often accelerating the return on investment significantly.
How Daylight Harvesting Systems Work
A daylight harvesting system is composed of a few key components working in concert: a photosensor, a compatible dimmable driver in the LED fixture, and a controller that processes the sensor's input.
Core Components
- Photosensors (Daylight Sensors): This is the "eye" of the system. It continuously measures the total amount of light in a specific area, including both natural and artificial light. Its placement is critical for accurate performance.
- Dimmable Drivers: The power source for the LED fixture must be capable of dimming. The industry standard for commercial lighting is 0-10V dimming. This protocol uses a low-voltage DC signal (from 0 to 10 volts) to control the light output. A 10V signal corresponds to 100% brightness, a 1V signal to 10% brightness, and a 0V signal typically turns the light off.
- Controller: The controller is the "brain." It receives the light level reading from the sensor and compares it to a pre-programmed target light level (setpoint). If the measured light is above the target, the controller sends a lower voltage signal to the driver, dimming the lights. If the light is below the target, it increases the voltage, brightening the lights.
Open-Loop vs. Closed-Loop Control
There are two primary strategies for implementing daylight harvesting, and the choice depends on the architecture of the space.
- Open-Loop Systems: The photosensor is placed where it can measure only the incoming natural light (e.g., pointed directly at a skylight or window). It does not read the output of the electric lights it controls. This system works on the assumption that more daylight outside means more daylight inside. It's simpler to commission but can be less precise if interior conditions change.
- Closed-Loop Systems: The photosensor is placed so it reads the combined light from both natural and artificial sources within the controlled space (e.g., pointing down at the workplane). This is the most common and effective method for warehouses. The system actively works to maintain a constant target light level on the floor or racking, directly compensating for the available daylight. If a cloud passes over, the sensor detects the dip in light and tells the UFO high bays to brighten up to maintain the setpoint.
The Benefits: Beyond Simple Energy Savings
Implementing daylight harvesting is one of the most impactful energy conservation measures (ECMs) for commercial and industrial buildings. The benefits extend from direct cost reduction to regulatory compliance and improved workplace quality.
Drastic Energy Reduction and ROI
The primary driver for adopting daylight harvesting is cost savings. According to the U.S. Department of Energy, daylighting controls can reduce lighting energy use by 20-60% in buildings with significant daylight potential. In a large warehouse running lights 12-18 hours a day, this translates into thousands of dollars in annual savings. These savings, combined with utility rebates, dramatically shorten the payback period for a lighting retrofit project. Many utility rebate programs, often found through databases like the DesignLights Consortium (DLC) Qualified Products List (QPL), offer prescriptive or custom incentives for installing fixtures with advanced controls like daylight harvesting.
Meeting and Exceeding Energy Codes
Modern building energy codes are no longer optional. Standards like ASHRAE Standard 90.1 and the International Energy Conservation Code (IECC) now mandate daylight responsive controls in many spaces. For example, these codes often require automatic daylighting controls in "sidelit" and "toplit" zones—areas adjacent to windows and under skylights. California’s Title 24, Part 6 is even more stringent. Failing to include these controls in a new construction or major renovation project can lead to failed inspections and costly rework. Using UFO high bays with integrated daylight harvesting is a straightforward way to ensure compliance from the start.
A Better Environment for Employees
While harder to quantify, the quality of the work environment matters. Studies have shown that access to natural light can improve mood, reduce eye strain, and align with the body's natural circadian rhythms. A space that transitions smoothly with the day's natural light is a more comfortable and visually appealing place to work than one under the constant, unvarying glare of full-power artificial lights.
Practical Guide to Implementation and Commissioning
Proper planning and commissioning are what separate a successful daylight harvesting project from a frustrating one. A common myth is that these systems are prone to flickering or erratic behavior. In reality, these issues are almost always a result of improper setup, not a flaw in the technology itself.
Myth Debunked: "Daylight harvesting is complex and causes flickering."
This is a frequent concern I hear from facility managers who experienced early-generation fluorescent dimming systems. The truth is, modern 0-10V LED systems, when commissioned correctly, provide seamless and unnoticeable performance. The key is setting gradual dimming ramps (5 to 30 seconds) so the transition from bright to dim is imperceptible to the human eye. Setting a minimum light level (e.g., 10-20%) also prevents the lights from cycling on and off, which can be distracting. With proper setup, employees won't even notice the system is working—but the utility bill will.
Commissioning Checklist for Contractors
Commissioning is a systematic process of ensuring the system is installed and calibrated to meet the owner's project requirements. Skipping this step is a recipe for poor performance.
| Step | Action | Practitioner Insight |
|---|---|---|
| 1. Verify Sensor Placement | Confirm sensors are installed according to the lighting plan. | A huge mistake is using a single sensor in the center of a long bay. Place sensors in multiple zones—near skylights, in the middle, and at ends—to account for how light moves through the space during the day. Avoid mounting them too high or behind obstructions like structural beams or tall racking. |
| 2. Confirm Driver Compatibility | Check that the fixture's 0-10V driver is compatible with the sensor/controller (sinking vs. sourcing). | Mismatched components can lead to failure or erratic dimming. Also, specify the fail-safe behavior: should the lights go to full brightness or a minimum level if control is lost? I always recommend maintaining a minimum output for safety. |
| 3. Establish Control Zones | Group fixtures into logical zones that receive similar amounts of daylight. | Do not put fixtures near a large window in the same control zone as fixtures in a dark corner. Zone grouping is essential for effective and efficient control. |
| 4. Calibrate Target Light Levels | With natural light absent (at night or with skylights covered), turn the lights on and adjust them to the desired brightness on the work surface. | Use a handheld lux meter. For general warehouse aisles, a target of 200–300 lux is a common starting point, as recommended by the IES for industrial facilities. Calibrate for the workplane, not the ceiling. |
| 5. Set Minimum/Maximum Levels & Ramps | Program the minimum dim level (e.g., 10%) and maximum output. Set the fade time for dimming adjustments. | A gradual ramp of 5-30 seconds prevents noticeable changes. This is the simple fix that prevents most complaints about "flickering" or sudden shifts in light. |
| 6. Test and Validate | During operating hours, observe the system's behavior. Use the lux meter to confirm that target levels are being maintained as daylight conditions change. | Be sure to account for seasonal variations. A low winter sun angle is very different from a high summer sun. Provide a field-adjustable setpoint so the facility manager can make small tweaks without a service call. |
| 7. Document for Rebates | Save the commissioning report, including setpoints, zones, and validation measurements. | This documentation is often a mandatory requirement for securing utility rebates. It proves the system was installed and calibrated correctly. |
Choosing the Right UFO High Bay Lights
Not all LED high bays are created equal. To successfully implement daylight harvesting, your fixtures need a few key features. The goal is to select a professional-grade fixture designed for control and longevity.
When evaluating options, look for the following:
- Standard 0-10V Dimming: This is non-negotiable. The fixture must have a 0-10V dimmable driver to connect to sensors and controllers. Avoid fixtures that are 120V only or lack the dedicated low-voltage control wires.
- High Luminous Efficacy: A high lumens-per-watt (lm/W) rating means the fixture is already efficient at converting power to light. This provides a better baseline for savings and helps meet strict Lighting Power Density (LPD) requirements in energy codes.
- DLC Premium Certification: Look for fixtures on the DesignLights Consortium (DLC) Qualified Products List, preferably with a "Premium" rating. This not only ensures high performance and a 5-year warranty but also makes the product eligible for the highest tier of utility rebates.
- Field-Selectable Options: Fixtures like the Hyperlite LED High Bay Light - Black Hero Series, 21750lumens offer selectable wattage and color temperature (CCT). This provides immense flexibility during installation, allowing contractors to fine-tune light output and color on-site to perfectly match the facility's needs.
By selecting a sensor-ready, high-performance UFO high bay, you lay the foundation for a robust and effective daylight harvesting system.
Key Takeaways
Daylight harvesting is a proven, reliable, and cost-effective strategy for any high-bay facility with access to natural light. It represents the next level of energy efficiency, moving beyond a simple fixture-for-fixture LED upgrade to an intelligent, responsive lighting system.
To succeed, you must:
- Choose the Right Gear: Select high-efficacy, DLC-certified UFO high bay lights with standard 0-10V dimming capabilities.
- Plan Your Design: Thoughtfully place sensors in multiple zones to accurately measure light and avoid common pitfalls.
- Commission Thoroughly: Do not skip the calibration and tuning process. A properly commissioned system is stable, effective, and unnoticeable to occupants.
By integrating daylight harvesting, you can significantly reduce operating costs, ensure compliance with modern energy codes, and create a better-lit, more productive workspace.
Disclaimer: This article is for informational purposes only. Electrical work should be performed by a qualified professional in accordance with the National Electrical Code (NEC) and all applicable local regulations. Consult with a lighting designer or engineer for specific project requirements.
Frequently Asked Questions (FAQ)
What is 0-10V dimming?
0-10V dimming is a common method for controlling the brightness of commercial LED light fixtures. It uses a low-voltage direct current (DC) signal between 0 and 10 volts. At 10V, the light is at 100% brightness. As the voltage decreases, the light dims. At 1V, it's typically at its minimum level (e.g., 10%), and a signal below 1V usually turns the fixture off.
Can I add daylight sensors to my existing high bay lights?
It depends. If your existing LED high bay lights have 0-10V dimmable drivers with accessible control wires (usually purple and gray), you can typically add a compatible third-party sensor and controller. If your lights are non-dimmable, you will need to replace the fixtures to implement daylight harvesting.
How much money can daylight harvesting save?
Savings vary based on utility rates, hours of operation, and the amount of available daylight, but reductions of 20-60% in lighting energy costs are typical for suitable applications. For a large warehouse, this can amount to thousands of dollars per year.
Is daylight harvesting required by building codes?
In many cases, yes. Energy codes like ASHRAE 90.1, IECC, and California Title 24 mandate daylight responsive controls in areas under skylights and near windows for new construction and major renovations.
Will the lights flicker or change brightness suddenly?
No, not in a properly commissioned system. Modern controls use gradual dimming ramps (fade times) to make brightness adjustments slow and imperceptible. This ensures a stable and comfortable visual environment. Any noticeable flickering or cycling is a sign of an improper setup.