Here a Watt, There a Watt

One of 10 retrofit LEDs that failed within eight months of installation.
One of 10 retrofit LEDs that failed within eight months of installation.

Last month, I wrote about the high electric demand on the utility system during summer and some of its effects. Demand-side management (DSM) is the phrase utilities use for ways to reduce the electrical demand of a facility all year. This helps the grid when heat waves come through by reducing the potential for sustained low-voltage conditions or service interruption. It also reduces expenses year round and puts money in your pocket, not the utility’s.

The first step in reducing electrical energy usage is to know how much is being used and where. No one can save more than is being used, despite claims by some vendors.

If there isn’t a full-time energy monitoring system in place, rent a few energy monitors. Then do a week-long survey by moving them around each day to different distribution panels or even right at the loads that are suspected energy hogs. Once the biggest users are determined, you can see if the return-on-replacement is worth it, no matter if it’s lighting, motors, heaters or any other large loads.

In most industrial and commercial facilities, it’s not just the electrical energy consumption in kilowatt-hours that matters. The demand charge can be a larger portion of the monthly bill than the energy consumption. The demand charge is based on the largest average kilowatt (kW) value over the demand interval, which is usually 15 minutes. While a single motor starting up doesn’t usually cause that value to rachet up (and stay there for months or even years), if the entire facility turns its loads on within the same demand interval, that could be the culprit.

Air conditioning loads on very hot days are often the peak demand offender. The Department of Energy estimates savings of about 1% for each degree of thermostat adjustment per eight hours. However, this should come with the fine-print disclaimer that “Your savings may vary” because there are many dependent factors. By increasing the setting from 70°F to 74°F on days when the forecast is over 90°F, it will save customers money and no one will melt.

Equally important is reducing unnecessary heat generation. Turning off equipment that doesn’t need to be on during such times means less HVAC is needed. Closing blinds to block out direct sunlight is also an effective heat reducer. Even cutting the amount of lighting to levels that don’t impact safety or productivity is a savings in both energy consumption and the HVAC cooling costs.

Check with the local electric utility to see if it offers any demand-response programs. This is where people voluntarily reduce specified levels of electrical energy use when they request to balance their supply with the overall demand. This may require some wiring configuration changes so that discretionary loads can be grouped in a manner that they can be turned off without affecting those that need to remain in operation. This can also involve running off of alternative power sources such as a backup generator.

A few notes of caution before you start implementing your own DSM program. Make sure that the savings are real, can be measured and are verifiable before and after implementation.

As stated before, no one can save more than what the load(s) consume. One such occurrence was for a lighting retrofit program. The vendor showed the facility manager the savings that would be obtained by changing all of the lighting over to his latest offerings. Based on the information from the energy monitoring system, we were able to calculate the lighting load by the difference of the kilowatt usage at 6:55 and 7:05 p.m. as the cleaning staff turn off the lights when they leave at 7 p.m. It came to 40 kW, but the energy rates back then was a little over $2,000 a year in lighting energy costs. The only way that the vendor’s claims of a $3,000 savings would be if his lights doubled as solar panels and generated energy.

It’s also impossible to save money using devices that don’t actually save energy, such as surge suppression strips. There are no measurable efficiency gains at your watt-hour meter from clamping the peaks of transients and diverting the energy through transient voltage suppressing devices. The IEEE Std 1889-2018 “IEEE Guide for Evaluating and Testing the Electrical Performance of Energy Saving Devices” is an invaluable resource for determining what’s real and what’s not. The guide has methods to evaluate and test the electrical performance of energy-saving devices, detailed protocols, description of step-by-step testing circuits, the type and accuracy of evaluation instrumentation and the order of the test measurements. Make sure that the replacement equipment has a good track record of reliability as well. I investigated a customer call about blinking and nonworking lights that had been installed only eight months before and discovered that 10 of the 30 retrofit LEDs had failed due to components burning up in the power supply section.

Don’t be overwhelmed by implementing your own DSM. Its like the old adage “How do you eat an elephant? One bite at a time.” The payback on a DSM is achieved by saving a kilowatt here, and a kilowatt there and continually reviewing and revising the program. And you don’t have to wait until summer to start. Savings are year-round.

About the Author

Richard P. Bingham

Power Quality Columnist

Richard P. Bingham, a contributing editor for power quality, can be reached at 732.248.4393.

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