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Rooftop Unit and Autonomous Control and Communication for RTU Network - Supermarket

Lead Performer: Oak Ridge National Laboratory - Oak Ridge, TN
Project Partner: Emerson - St. Louis, MO
DOE Funding: $575,000
Cost Share: N/A
Project Term: Oct. 2012 - Sept. 2014

Project Objective

Supermarkets are one of the most energy intensive operations and stores with sales area around 3700 – 5600 m2 consume 2-3 million kWh annually per store. Refrigeration systems in these stores consume around 50% of the total store energy use. Often times the peak energy consumption of the refrigeration systems coincides with the peak demand for electricity as seen by utilities (mid to late afternoon during summer). These systems can participate in demand response strategies using advanced controller formulations that can respond to utility signals by 1) reducing the number of compressor cycles, 2) shifting peak load time to offset utility peak loads by scheduling mechanisms and use of inherent thermal storage, 3) robust control of the refrigeration systems for increasing energy efficiency and reduction in faults. Apart from advanced controls to optimize the refrigeration systems, fault detection and diagnosis to improve the refrigeration process can be very beneficial. For example, adjusting the suction pressure based on the ambient temperature for multi-stage refrigeration systems can improve the energy efficiency by 8-15%. Adaptive fine-grained synchronization of the refrigeration loads provides opportunities for building-to-grid integration potentially beneficial to building owners and local energy markets.

In this project, ORNL is investigating the requirements and designing supervisory controllers to engage commercial refrigeration systems to provide energy services to the electric utility. The controllers will be developed on the RTU Network platform. ORNL will collaborate with Emerson to analyze the potential to use supermarket refrigeration systems for providing demand response and ancillary services to electric grid while improving energy efficiency of the refrigeration systems. ORNL and Emerson will also develop partnerships with commercial supermarket refrigeration sites to demonstrate the advanced control platform. The project comprises of five tasks: (1) Evaluate potential for commercial refrigeration systems for providing demand-side energy services, (2) Develop formulation of refrigeration system control using model-based optimal controller strategies, (3) Extend RTU Network Platform to integrate commercial refrigeration systems, (4) Develop prototype application to perform optimal control for energy efficiency and utility requirements, and (5) Outreach and commercial partner engagement for prototypic testing and validation.

Project Impact

Integration of refrigeration loads in grid related activities require high performance control systems to handle complex dynamics imposed by varying loads and sources. Advanced control techniques have the potential to improve the energy efficiency by 20-30% thereby reducing energy costs by 20-30%. The proposed project will identify control and communication capabilities to support specific energy services, and will guide efforts that are currently underway in utility sector to use refrigeration loads for reducing the need to operate generation that provides peak support, spinning reserve, and other ancillary energy services.


DOE Technology Manager: Joe Hagerman
Lead Performer: Teja Kuruganti, Oak Ridge National Laboratory