Automated Demand Response : Preparing Multi-site Businesses for the Smart Grid
By Jonathan Histed, Senior Marketing Manager, at Novar a division of Honeywell International
For a few days each year, demand for electricity outstrips supply. Historically, demand spikes have occurred at the hands of weather extremes - heat waves and cold snaps, for instance, cause the consumption of energy to exceed its creation. When this occurs, grid operators have only two options - they can call up "peaking" power plants (typically gas or diesel generators) that are very expensive to maintain and operate, or they can buy capacity from other consumers of energy who are willing and able to reduce their energy load.
This second option is called demand response. When using a demand response program to reduce load, a utility or ISO (independent system operator, a third-party responsible for maintaining balanced distribution of power on the grid) will notify enrolled customers that an "event" is necessary. These events can require fast (ten minute or less) response, or could be scheduled hours or even a day ahead. By getting commitments from customers to reduce load, the ISO or utility can better plan how to respond to the peak demand on the grid.
As more variable generation capacity comes online through renewable energy sources such as wind and solar, the need to balance supply and demand on the grid will increase, and so will the complexity inherent in the balancing act. Even small nuances in weather will have a significant impact on energy demand and management. Widespread cloud cover, for instance, can affect both supply and demand, reducing the kW generated by solar panels and increasing the energy consumed by hundreds or even thousands of buildings reliant on light harvesting by two-thirds or more as those buildings are forced to compensate for daytime darkness by lamping. As a result, demand response will become a much more important part of day-to-day grid operation.
Site-Level Demand Response Variables
There are many ways to respond to a peak demand event by reducing
load within a building. The challenge is to do so while maintaining
optimal conditions for customers in the site. In retail settings,
for instance, temperature set points and lighting standards are
tied directly to the customer's comfort level and store experience,
and thus, these environmental factors can impact the brand.
In retail settings, some common approaches to reducing peak load during a demand response event include:
- Lighting adjustments. Reduced lighting levels in employee-only areas or across the entire site can deliver significant load reductions. While branding requirements will likely limit changes to accent lighting, overhead lights can be lowered or even turned off in some areas without impacting the consumer experience. In fact, many consumers have indicated that lower lighting makes a store feel cooler.
- HVAC manipulation. Pre-cooling the space prior to an event can provide some short term load reduction, however intelligent throttling of each RTU (rooftop unit) is essential to managing load over a long (multi-hour) demand response event. In these cases, the EMS (energy management system) should determine a strategy based on outdoor temperature and humidity to create an indoor environment that remains comfortable, while reducing the total electric load. In addition, the EMS can manage cooling cycles to ensure that other demand response measures are maximized when additional cooling is required.
- Refrigeration manipulation. Pre-cooling of refrigerated or frozen cases can deliver medium-term load reduction by utilizing the thermal mass of the cooled product. In addition, a smart grid-ready EMS can coordinate the operational needs of the refrigerated cases with the HVAC and lighting loads to ensure defrost and cooling cycles do not cause spikes in demand.
Reducing the Management Burden Through
Automation
When a demand response event occurs on the grid, the coordination
of these adjustments in manual fashion across a multisite
enterprise is impractical and ineffective. Manual management of a
demand response event requires energy or facility managers to
actively initiate and deactivate DR events, taking his or her focus
away from more important duties. It's also ineffective because it
requires a conscious decision to act at a personal level, an
approach fraught with forgetfulness and manual error.
The alternative is ADR (automated demand response), which is enabled by a modern EMS. ADR eliminates manual intervention from the response to a demand event, allowing multisite businesses to maximize the benefits of the smart grid. Communication of the event is coordinated between the utility and the appropriate site equipment in machine-to-machine fashion, managed only by exception (e.g. if the retailer chooses to opt out of the event). Even communication with store-level managers is automated; the system notifies them when and for how long the event will take place, and what actions are being taken. Many retailers even choose to automate pre-recorded messages over the stores' audio systems when an event is in process, informing shoppers of the impending power consumption adjustments and thus improving the brand's sustainability standing among consumers.
The maturation of the smart grid brings with it new complexities, but also many opportunities for multisite businesses to improve control of their energy spending. ADR, facilitated through a modern EMS, prepares those businesses to take full advantage as the future of energy supply, demand, and consumption takes shape.