By Paul Carlson
This blog is the second in a three-part series exploring building management systems and energy efficiency strategies. This post focuses on how a holistic approach can reduce energy use and costs storewide. In part three, we’ll look at reducing costs at the enterprise level.
In my last post, I discussed how a central building management system could help refrigeration, lighting and HVAC equipment operate more efficiently. Introducing equipment-level efficiency strategies is an essential step to reducing costs, but it’s also important that this equipment work efficiently as a whole.
Taking a holistic approach to reducing operating costs begins with a quick lesson on how energy companies charge convenience stores. (Don’t worry, it’ll be painless. I promise.)
Most electric utility companies bill their customers based on total kWh used and peak kW demand. If a store goes above a specific “demand threshold,” even for a short time, its cost per kWh increases. So it’s important to stay below that threshold whenever possible. But, how is that possible when convenience stores are usually running all of their critical equipment simultaneously? That pushes the needle way up — and turning certain equipment off in the middle of the day isn’t an option.
That’s where a building management system comes in.
To avoid higher demand charges, building management systems stagger equipment run times to help prevent new peak demand levels. Here’s an example: A convenience store is running its refrigeration, partially dimmed lighting, HVAC, cooking appliances and electrical signs in the middle of the afternoon. As energy demand trends toward a new peak, the building management system cycles HVAC rooftop units or partially reduces their load to avoid breaching the programmed demand kW threshold. This helps the store remain in a lower-demand kW rate tier without affecting the store’s environment.
Because equipment uses more energy when it’s starting up, an intelligent controller can stagger equipment start-ups to keep multiple devices from starting at once, helping reduce the store’s demand. For example, before a store opens, a building management system could stagger individual HVAC units so they are not all starting at the same time. The system would keep the lights off until all the HVAC units are up and running and the store has reached the desired temperature, which avoids drawing additional loads from the lighting systems.
This strategy, often called optimized start/stop, is designed to handle pre-starts and pre-stops in the most energy-efficient manner possible. Over time, the building management system measures how long it takes to bring the store temperature from the previous setpoint to within the defined operating parameters of the new setpoint. In this way, the system is continuously learning and alters its function to match evolving store conditions.
By scheduling and operating equipment with the full knowledge of other systems in the store, building management systems can attain an entirely new level of operational efficiency. In addition to lowered energy usage and reduced utility costs, these systems can also reduce total operating costs, enhance the customer experience, and boost employee productivity.
Paul Carlson, Emerson’s vice president/general manager — foodservice, is an accomplished executive with engineering, operations and leadership experience in positions at Earth Energy Systems, Trane, Coca-Cola, Cornelius, Control Products and Emerson. Over his 30-year career in the alternative energy, food & beverage and electronics industries, Paul has worked with both public and privately held organizations in many functional capacities, including product development and engineering, sales, operations and general management.