7 minute read
Lighten The Load
By Jennifer Brons Light and Health Research Center at Mount Sinai
A version of this article appeared in designing lighting (dl), October/November 2025 issue
How Outdoor Systems Can Support Grid Stability
Utility companies are facing increasing challenges in balancing electric supply and customer demand. For over a century, electrical generation has been accomplished with a limited number of power plants that are carefully designed to meet maximum electrical needs.
As electrical demand continues to rise, solar and other renewable power generation have helped to offset construction of more nuclear or fossil fuel power plants.
Managing this balancing act efficiently while maintaining grid stability is a key concern (Figure 1). Demand for electricity has always varied by time of day, season, and region. But, with the growth of renewables, power generation itself has been added as a time-dependent variable. This can be a particular problem when the timing of demand does not match generation schedules.
When electrical demand exceeds supply, utilities must purchase electricity or use inefficient plants, which can create logarithmic price increases. Conversely, when electrical supply from renewables exceeds demand, efficient plants must be taken offline to balance supply and demand. This, too, is costly for utilities.
To achieve this balance of supply and demand, utilities are looking for alternatives to “shave” the demand peaks and “fill” the supply valleys. Figure 2 illustrates how this would work with a common and a new type of load profile. By charging batteries during times of low demand and using that power in times of high demand, the utility goal of “flattening” the load is closer to being reached.
Parking lot lighting presents an ideal opportunity for load flattening because as the sun sets, photovoltaic production decreases, and demand for electric outdoor illumination increases.
Switching between battery charging (when demand is low) to battery use (when demand is high) for parking lot and other forms of outdoor lighting can help to keep utility costs down and grid reliability high.
Here we present the results of a study where parking lot lighting used battery storage in this manner.
PROTOTYPE DEVELOPMENT
Funded by the Northwest Energy Efficiency Alliance, the Light and Health Research Center recently developed a simple prototype referred to as a “load shed” system. While there are numerous potential uses for this technology, we focused on a proof-of-concept design for lighting a small to medium-sized parking lot adjacent to our laboratory in Menands, NY, between September 2024 and June 2025.
TESTING RESULTS
The load shed prototype performed well and successfully demonstrated non-emergency nightly shifting for multiple operating parameters. The battery charged and discharged properly, both in the depths of a Northeastern winter and during a summer heatwave.
When the length of the winter evening exceeded the battery’s capacity, the system automatically switched to mains electricity as designed. The system also powered the luminaire during a simulated power failure, providing functionality not commonly available in parking lots.
The prototype’s battery was positioned in a pole-mounted enclosure (Figure 3) along with other energy storage equipment (charger/monitor), electrical equipment (ac/dc inverter, relays), controls (photocell, timer, clock, cellular interface), and monitoring equipment. (Detailed schematics of the design are available from the author on request.)
We designed the system to maintain the same light output regardless of power source.
We also tested demand emergencies that simulated a utility company sending an automated demand response signal to override the system’s scheduled programming and operate the luminaire via battery beyond the system’s nightly flex load shed parameters.
While the cellular communication we used for the test showed minimal lag time, there were a few instances when wireless commands were not getting through to the system due to a spontaneous disconnection from our cellular network. Fortunately, the system continued to operate with the previous program settings, allowing nightly flex load to shift to a less expensive time of day as designed.
BUSINESS OPPORTUNITIES
Based on data from the U.S. Department of Energy,2, 3 we estimate that 53–83 million parking lot lights were operating in the US as of 2020. Assuming an average power demand of about 155 watts per light, this translates to a nationwide parking lot lighting demand of 8,220 to 12,870 megawatts that could be shifted to off-peak demand times.
Our calculations show that shifting this demand would variably reduce energy costs, depending on market factors. A similar system installed in Idaho, for example, would see a payback period of 37 months whereas one installed in Southern California would yield a payback in only 18 months. Incentives offered by utilities to encourage the adoption of load shed systems could further enhance the proven economic benefits.
A principal limitation to adopting load shed technology is the significant impact of season on electrical demand. During autumn through spring in much of the US, daily peak demand occurs a couple of hours after parking lot lighting turns on. Summertime peak demand, on the other hand, occurs before the lighting turns on, potentially making demand management less useful for electrical utilities.
In fact, because annual demand for electricity peaks during the summer in some regions, some utilities incentivize demand management efforts during the summer only, for limited hours of the day. But demand profiles are changing, especially with increasing electrification (e.g., vehicle charging at night).
FUTURE CONSIDERATIONS
Our research revealed several considerations for effectively bringing load shed technology to market.
♦ Maintaining a load shed system’s wireless connectivity is important for its capability to respond to grid emergency signals.
♦ Battery capacity should be based not only on the size of the load, but also on intended duration of operation. A smaller battery could be used for a few hours of nightly flex load. A larger battery may be needed for grid emergencies.
♦ Consider integration of load shed technology in luminaire heads. This may reduce AC/DC conversions but will limit physical size/form factor of battery and duration of operation. While integration would avoid an ungainly enclosure connected to a pole, it would add complication to luminaire housing design. Luminaire integration might also offer opportunities to expand load shed technology to street lighting.
♦ Pole-mounted load shed technology would be suitable for small to medium-sized parking lots with about 1 kilowatt of outdoor lighting. For lighting larger sites, we calculated that a centralized battery system would be more practical for load management.
♦ While many utilities in North America already publish special rates to encourage demand management, many have minimum loads (e.g., ≥ 50 kilowatts) for eligibility, which most potential end-users of this load shed technology would not meet.
♦ To accommodate minimum load requirements, a “curtailment service provider” could be used to aggregate load shed savings from a client portfolio in the utility’s territory as part of a suite of solutions that aggregators could offer their clients.
Outdoor lighting presents opportunities for commercialization and aggregation of simple load shed technology for sites across the country. We expect this technology to offer nightly opportunities for electrical flex load management that will help utilities balance supply and demand in the future.
ACKNOWLEDGMENTS
The author wishes to acknowledge Chris Wolgamott of the Northwest Energy Efficiency Alliance for providing inspiration and support for this research. The project was also made possible by the design and fabrication efforts of Light and Health Research Center staff and Namreiba LLC of Albany, NY. To learn more about this load shed technology, contact us for detailed schematics.
REFERENCES
1 U.S. Energy Information Administration. Hourly Electricity Consumption Varies Throughout the Day and Across Seasons. Washington, DC: U.S. Energy Information Administration, 2020. [Available from https://www.eia.gov/todayinenergy/detail.php?id=42915].
2 Buccitelli N., Elliott C., Schober S., Yamada M. 2015 U.S. Lighting Market Characterization. Washington, DC: U.S. Department of Energy, 2017. [Available from https://www.energy.gov/sites/default/files/2017/12/f46/lmc2015_nov17.pdf]
3 Elliott C., Lee K. Adoption of Light-Emitting Diodes in Common Lighting Applications. Washington, DC: U.S. Department of Energy, 2020. [Available from https://www.energy.gov/eere/ssl/articles/2020-led-adoption-report?nrg_redirect=453978].
