Grocery retailer monitors and manages energy

Demand-response program for energy in the US

US-based grocery retail company Supervalu has installed energy monitoring hardware and has enrolled in a demand-response program with Net Peak Energy Group. The program organises payment to the retailer for effectively ‘selling’ their electricity back to their utilities when demand is high. Additionally, the program can call for the retailer’s distribution centres to shed up to 1.2 MW of power.

Net Peak is typically able to provide one to two hours of advanced notice to initiate the emergency load shed. The dispatch specialists use custom designed interfaces for real-time monitoring of Supervalu’s energy consumption. Detailed data comes from a hardware device called an OptoEMU sensor, developed by Opto 22. The sensor provides the physical connections needed to remotely monitor and acquire real-time energy data, from a variety of systems, equipment and metering devices, and then sends the data to network databases and web-based applications.

The sensor monitors both pulse-emitting devices (such as utility meters and sub-meters) and the voltage and current of several load panels, chillers and refrigeration units. All communication takes place over the internet via standard TCP/IP, providing a simple and standards-based way to interface to the monitoring hardware.

Once notified, the company needs to quickly take action and begin curtailment of energy. To achieve this, an Opto 22 SNAP PAC system (programmable automation controllers and I/O) uses integrated circuit temperature detector (ICTD) sensors to monitor temperatures and analog and digital output signals to expertly manage compressors, control solenoids on evaporators, switch relays and provide immediate response to the Net Peak dispatch centre demand-response trigger.

The system handles about 1500 inputs and 500 outputs in total, enabling full demand-response automation of Supervalu’s industrial refrigeration and ventilation. The HVAC and lighting systems will also be handled soon.

The SNAP PAC system also carefully maintains specific refrigeration temperatures and is programmed to send alerts if these ever deviate from a predefined range. This ensures that food is always stored and preserved properly and no spoilage occurs.

The return on investment, resulting from the energy management initiatives, is twofold. Firstly, payments and savings for the demand-response participation and curtailment are estimated to generate approximately $75,000 to $115,000 in annual revenue. Secondly, the monitoring and control systems have led to more efficient cooling and overall reduction in the facilities’ energy consumption during everyday operations. This has resulted in an estimated energy savings of over $155,000 per year. The control system has also identified several refrigeration system inefficiencies that could push this figure even higher.