Shedding Energy Loads
As retailers look for new ways to decrease their energy usage, they are showing increased interest in load shedding, a strategy whereby selected energy loads, such as lighting, are reduced because of a request from the utility, or to reduce the cost created by an excessive electrical demand. Andy Foerster, director, lighting control business, Square D/Schneider Electric, Palatine, Ill., spoke with executive editor Marianne Wilson about load shedding in the retail environment.
Chain Store Age: How have retailers reacted to load shedding?
Andy Foerster: Most merchandisers have responded to the whole issue of load shed with a grain of skepticism. Being unsure of the actual savings opportunities, their response has tended to be fear of losing customers due to having buildings that are either too hot or dim. But this does not have to be the case. Lighting should be considered foremost as a starting point when considering a load-shed design.
CSA: Why is that?
Foerster: Very often, lights can be dimmed 30% with little-to-no perception by customers. And because lighting very often makes up the bulk of a retailer’s total connected electrical load (often up to 60%), it is the obvious load to first consider.
Also, most peak-demand periods will occur during the summer months when the need for cooling is very high. By shedding lights, a huge burden is removed from the HVAC system. That means that temperatures within the store can be maintained at comfortable levels without creating huge electrical demand spikes.
CSA: What lighting-control technologies can be used for load shedding?
Foerster: Whole-building, schedule-based lighting control systems that are Web-enabled provide perhaps the best opportunity for retail store owners to reduce or turn off selected lighting loads. These systems are normally used to control energy costs by switching lights off during closed periods, but these same systems can also easily be used to reduce loads in response to a load-shed request.
Customers who have invested in Web-enabled technologies will have the added benefit of being able to issue load-shed commands either manually or automatically using their company’s internal wide area network.
CSA: Some retailers may still worry that dimming store lights will have a negative impact on sales. What advice do you have?
Foerster: Through proper selection of lights and fixtures, combined with a properly commissioned lighting-control system, customers should not see any discernible change in lighting during a load-shed period.
CSA: What is automated demand response and how does that fit into all this?
Foerster: Automated demand response is a load-shedding concept whereby the utility or energy-services provider automatically reduces a building load.
CSA: How does automated demand response differ from load shedding?
Foerster: In most load-shed applications today, the utility will call or e-mail the end user with the energy-reduction request, typically in the morning or the previous day. But with automated demand response, the utility would issue a signal to a retailer’s power meter or facility building automation system, which would then turn off pre-set, non-essential energy loads.
In the case of lighting, for example, a schedule-based, whole-building lighting control system, such as the Square D Powerlink lighting control system from Schneider Electric, often serves as a direct interface to the utility’s or service-provider’s shed signal.
CSA: What are the benefits of automated demand response to a retailer?
Foerster: A recent Pacific Gas & Electric report indicates that the energy and related cost savings of automated demand response could be significant. It projects that a department store could shed up to 30% of its electrical load dedicated to lighting, while a grocery store could shed as much as 25% of its lighting load. A high-end specialty store could shed as much as 40% of its lighting load. When the retailer is faced with variable-rate energy pricing, these reductions can be significant.
An additional benefit is that utilities will often negotiate an improved rate structure for retailers that choose to participate in an automated demand response program vs. those that do not.
CSA: Are there any other benefits?
Foerster: Yes. While lower peak demand charges and more comfortable temperatures during shed periods are foremost, these systems can also further reduce operating cost by using them during non-peak periods.
For instance, 24-hour operations can use these systems to reduce lighting levels during those late-night levels when few customers are in the store. In fact, a dimmer lighting grid can be perceived as being more desirable during these periods because customers’ eyes are dilated and the same level of light that is needed during mid afternoon is perceived as being harsh at 2 a.m. By dimming lights during these periods, electrical consumption is reduced and for some lighting, equipment life is extended.