by Thomas Schubert, PE, Electrical Engineer
Most people would agree that saving energy is a good thing.
Unfortunately, a problem often occurs when we shift from principle into practice. Don’t get me wrong, there are certainly those individuals who turn off the lights when they leave a room, wear a sweater instead of turning up the thermostat, and prefer to drive the speed limit, knowing going any faster would waste fuel. But they are the minority. Most people aren’t motivated by the higher good but by simplicity. “Does saving energy take more effort? Not interested!”
This is why a shift in approach is necessary. Instead of trying to force building users to care enough to take the extra step to save energy, we should instead be making it easy for them to do so. Within the realm of lighting, this could be implementing lighting control systems that incorporate additional energy reduction, require no or minimal extra effort from users, yet doesn’t take away their ability to make lighting choices.
Occupancy vs. Vacancy Sensors
By this point everyone has experienced the occupancy-controlled room. When you enter, the lights turn on automatically. Upon departure, and after a set time, the lights turn off. While this scheme saves energy by eliminating the accidental illumination of an empty room for an evening or more, it also wastes energy when someone pops into the room for a moment or the sensor catches someone walking past it.
Most codes fix this problem with vacancy sensors. Instead of the lighting turning on automatically, with a vacancy sensor the user must press the light switch to turn on the lights. The sensor still works in the vacant case, turning off the lights after a set period of inactivity. This empowers the user to ask themselves if they need the lights on.
On to 50 Percent
Most of us are used to the traditional on-off switch. Flick a switch, and lights turn on to 100% full brightness; flick it the opposite direction, and the room becomes completely dark. Dimming is available, but has always come with an additional cost in any fluorescent fixture. Plus, people quickly learned that if they needed more light, they had to push the diming slider all the way to full lighting; they weren’t thinking about the quantity of light needed, only that they needed it.
A simple, yet powerful control strategy is to default all lights to turn on at 50% of their total output. The user then has the option to remain at the lighting switch, holding down the “on” button for a few seconds to increase the levels up to 100%. This allows for the user to have access to the lighting they need for the task, but also requires them to take a moment to request the extra lighting instead of giving it to them automatically.
Most indoor spaces are over-lit. This stems from the need to light at a specific level for a specific space, a desk, or a work surface. However, instead of lighting that area, we typically fill the whole room with an equal amount of light. Every task requires a different amount of light, from working on a computer to writing a letter to building a circuit board. We don’t need the same lighting levels to walk to our desk as we do to work at our desk, so why do we provide it?
When designing lighting for a space, we first must understand the function of that space, and then layer lighting to each task. General lighting can be at a lower level, with specific lighting for the tasks being performed. The users should be able to decide when they need the additional lighting – and when it’s not required. Providing vacancy controls integral to the task lighting saves even more energy.
At the end of the day, as lighting design professionals, it is important that we create a new paradigm, and evolve beyond the unsuccessful model of solely relying upon users to make informed decisions to save energy, and instead provide the lighting systems and controls behind the scenes, simplifying the users’ decision-making process.