The escalator may not be the first place you look to cut energy costs, but it should be.
Escalators are the most efficient way to move huge groups of people, but because most escalators remain constantly ready to take on a peak load, they pale in comparison to elevators for moving small crowds. Add in building standards that prevent you from stopping the escalator when it's not in use and you have a device crying out for modernization.
Unfortunately, basic escalator technology hasn't changed much over the years, says Alan Taylor, senior vice president of business development at Power Efficiency Corporation, an energy efficiency technology developer. The steps are driven by a moving chain, which is powered by a motor. Aside from construction and design changes to make installation more cost-effective, escalators simply haven't evolved the way elevators have.
Though most green options involve replacing most, if not all, of the device, there are a few simpler options to modernize an old escalator, adds Brent Andrews, product manager for escalators at KONE.
Replace the Drive
Replacing the drive with a smarter modern version can cut energy directly by feeding the escalator less power when it's not in use or by changing to a low-energy mode.
"The only thing you can do to make it more mechanically and electrically efficient is to put in a drive system that would reduce the energy consumption when it's lightly loaded, or put a drive system in place that would allow the escalator to slow down," Taylor says.
A variable voltage drive will note when the escalator is carrying a light load (or none at all) and drop the voltage flowing to it until more people step on, cutting the energy consumption when full capacity isn't needed.
Similarly, a variable frequency drive tailors its behavior based on its load, but instead of directly cutting energy availability, it dramatically slows down the escalator's speed to a crawl that requires less power. Variable voltage-variable frequency (VVVF) drives tackle energy consumption on both fronts.
The national average for a 15-horsepower drive is about $2,500 to $3,000, but can vary widely due to regional labor costs, Taylor adds. With an average of 2 hours in labor for the installation, most drive replacements can save enough energy to pay for themselves in about 3 years.
Modernize with an Energy Management Approach
A soft start device for certain types of older escalators starts the escalator with a gradually increasing level of current instead of feeding it full power immediately, Andrews says. This helps increase the useful life of the motor, delaying costly motor repairs and replacements. Some soft start devices also incorporate energy-saving features that supply less electricity when fewer people are riding the escalator, he adds.
A combination device built to save energy "will constantly change how much electricity is being applied. That's where the energy savings really come into play," says Andrews. "We can see anywhere from 10 to 40% energy savings on an existing unit, just because of how those units are manufactured and the age of the equipment."
If adding one of these is not an option, try a modernization project that replaces the guts of the escalator, but not the entire unit. This involves gutting an old escalator down to its truss frame, cleaning it up, and retrofitting most of a new escalator onto the existing frame, costing $200,000 to $500,000 per unit. However, choosing not to replace the entire unit allows you to cut down or avoid replacing the surrounding flooring and walls, reconfiguring electrical service to the escalator, and other costs.
"A lot of customers do not want to open up the facade of their building, rip out a 20,000-pound escalator, and bring in a new one," Andrews says. "We can keep at least one escalator in a pair running at all times. When you're doing full replacement, you have to shut down both escalators together."
Don't Forget to Clean
Energy efficiency isn't just a replacement or renovation issue. A thorough cleaning and realignment once a year will save a surprising amount of energy and ensure a smooth ride, Taylor says.
"Keeping proper maintenance on the escalator is probably one of the biggest pushes that needs to be done," he adds. "Over time, escalators get out of alignment and start dragging, which requires more energy to move the escalator. There's a big difference in power usage between one that's been cleaned and one that's been running for 8 months."
is associate editor of BUILDINGS.