Energy Efficiency: Are Weeknight Setbacks Worth the Trouble?

This is the third article of a five-part series on industrial energy efficiency. This month we cover Part Three of the series: Weeknight Setbacks. This is the practice of reducing or eliminating an industrial facility’s energy usage during weeknight off-periods.

Energy is complex. With so many moving pieces, it’s easy to get overwhelmed when trying to improve efficiency. And industrial facilities, with multiple independently-controlled systems, are equally complex.

Let’s see if we can’t simplify the strategy for setting up a weeknight setback procedure in your facility.

Identify the Baseload

First, identify the amount of energy used during weeknight off-shift periods.

Buildings don’t turn off at night, they turn down. Overnight load (or “baseload”) is something you always want to minimize if your facility is unoccupied. It sounds like a no-brainer, but even the most efficient buildings may present a baseload energy management opportunity.

Differences in baseload are often easy to spot. For instance, if you’re seeing only shallow drops in energy demand, that probably means that few pieces of equipment are actually shutting down during these off-periods.

Ask yourself, “What do we turn off on Saturday night that we don’t on weeknights?”

A Walk-Through Energy Audit

A walk-through audit of your facility after hours can really shed some light.

  • Is there any equipment routinely left on that could be shut off? Any motors operating unnecessarily (such as a ceiling fan in an unoccupied space)?
  • What about computers and office equipment? Any that don’t go into “sleep” mode after a period of inactivity? This could be a real power drain.
  • With regard to lighting, occupancy sensors and timers can capture significant energy savings. But they need to be combined with lighting systems that can be effectively controlled. Is your staff trained to turn off all lights when closing?
  • Space heaters are huge energy hogs. If they’re being used in your facility, that usually indicates poor HVAC system control. You’ll want to investigate.
  • Is your rooftop ventilation unit equipped with exhaust fans? You can set them to run only when spaces are occupied.

Temperature Setbacks

Did you know that heating and cooling your facility can account for up to 50% of your energy use?

One of the most cost-effective means of reducing energy consumption is by setting the temperature back during weeknight off-periods. (Typical thermostats are set between 65°F to 70°F for heating and 72°F to 78°F for cooling.)

The Department of Energy projects that you can reduce your energy cost by  5% – 12% with a 3°F to 10°F setback. A 10°F to 20°F setback can result in a 9% – 18% energy cost reduction!

 

Programmable thermostats are typically classified as three types:

Electromechanical thermostats use an electrical clock and a series of pins and levers to control temperature. These are the least expensive programmable thermostats. They’re also easy to control, but offer limited flexibility.

Digital thermostats allow you to tailor settings to varying schedules for different days of the week, or up to four different “setpoints” per day.

Occupancy sensor thermostats maintain the setback temperature until triggered by a person entering the controlled space. The trigger mechanism can be a switch, button, light, or motion sensor.

Is It Worth It?

Once you’ve implemented a weeknight setback program, you need to determine if it’s paying off.

Fortunately, new technologies now allow industrial businesses to compare energy use over time to see how setback sequences change. Having access to historical demand data to create a relative performance benchmark is a key consideration when contemplating an energy efficiency strategy.

According to the Department of Mechanical and Aerospace Engineering at the University of Dayton, the easiest way to track your progress is by using data analysis software that compiles available temperature, production and utility billing data.  Anything more complicated may be too complex for widespread use.

The EPA’s Energy Star Portfolio Manager is a reasonable choice. Not only does this online tool measure energy and water consumption, but it tracks greenhouse gas emissions as well. And it can be used to benchmark the performance of a single building or multiple buildings.

Up Next…

Hard starts are rough on equipment, causing premature wear and tear. And they can lead to unintended peak- demand charges. Our next article, “Start-Up Spikes,” will look at how to avoid them.


Sources:

Business Energy Advisor

NC Energy Office

Gridium.com