Sometimes I wonder. No, sometimes I’m amazed how certain energy efficient technologies have fooled the industry and the public for years, possibly even decades, into a false sense and blind acceptance for energy savings. Want to see two technologies that are flexible, cheap, easy to use, and effective at saving energy? That’s it – the first two wonder technologies shown.
Instead, there are universally accepted incentives and “savings” that would make a charlatan blush. Exhibit A: the occupancy sensor for lighting control.
As I ranted in Oh Behave, I have found that this technology wastes energy by training occupants to leave the lights on. Possibly at one time, when the Cuyahoga River caught fire and automobiles weighed six thousand pounds, and the bumper alone had more rust-prone steel than an entire compact car does today, an automatic switch to turn the lights out would save energy.
Although it seemed like a good idea at the time, we still have this dumb technology in our office. Why? I don’t know. We paid for them? They are installed? They “work”? It costs money to disable or bypass them? That is probably the correct answer. One benefit: they provide a demonstration and insight into mass-market studies that show little to no savings for many/most applications.
Here are the problems with the technologies and I think some tips to minimize the resultant energy they waste. There is the infrared sensor – sample shown nearby. This demon works by detecting surface temperatures in a room. For example, the copy machine is 120F and human bodies, faces, and exposed skin are roughly 93F. It watches for moving blobs of temperatures. Come to think of it, it would be interesting to see if a rolling can of cold beer could turn the lights on.
The problem with these things is the blob needs to move about four feet to trigger the thing. In fact, if an occupant is a fast walker, they might walk several paces into the dark room, trip over a box of copy paper, fall and break their arm, and the lights come on just in time to see the arm bent in a 90 degree angle, where it has never bended before. I’ve seen this with my left arm and one of my toes. It‘s quite a sight and a “holy ___” feeling, impossible to forget. With the need of large blob movements, the delay time from detecting motion and opening the circuit to turn the lights off must be fairly long, e.g., after leaving the room. Cue the energy waste.
On the other end of the pun spectrum, we have the ultrasonic detector as shown with the next image. This demon is constantly blaring inaudible noise (if a tree falls in the forest?) and like sonar on a submarine, only dumber, senses changes in the reflected sonic waves. If something in its range moves, the reflected waves change form, and the demon knows it. Opposite the infrared demon, this thing is hyper sensitive. For example, make a thumbs up. Go ahead, it feels less dumb than closing your eyes. Now move your thumb one inch in any direction. That will trigger this sensor. The problem we’ve experienced with these is false-on signals. Just walking past a room with a sensor, and with an open door, flips the lights on. How cool is that?
The overarching problem is therefore: to ensure the lights don’t go out while a space is occupied, thus ensuring they don’t get overridden (god forbid we use less energy), lights are left on longer than needed.
This is all smarty pants anecdotal junk, but where’s the beef? Glad you asked.
We are approaching the conclusion of a massive statewide evaluation of occupancy sensors, and data show what I’ve said with few exceptions is true. These wonder widgets waste energy during the day because people turn lights off on their own more effectively than these controls do. In fact, preliminary data show zero savings every single hour of the day for offices (weighted composite results) and negative savings during the day when people are in the building. I wonder how to effectively weed out the bias; i.e. it compares apparently conscientious program participants that installed these demons against apparently clueless non-participants, the latter of which use their lights less.
So are they completely bad? No. For spaces where turning the lights out is a pain, where it might require walking a couple hundred feet in the dark to turn them on, do your business, and take a stroll again to turn them off – good application. Tie-ins with HVAC systems can also provide benefits, but that’s beyond the scope of this tale.
Moral of the story: give people control and they’ll do the right thing. Just don’t give them a space heater.