Introduction
IntroductionA national food supplier sought to expand its Boca Raton, Florida, USA distribution center to match growing business demand. This project required additional refrigeration equipment, which potentially meant higher energy bills. The company was looking to reduce energy costs and modernize its control system.
Global Controls Solutions LLC (GCS), a system integrator, wanted to achieve the company’s goal by using a PROFINET industrial Ethernet network with help from programmable logic controllers (PLCs). This network transmits data from the refrigeration system to help the facility limit electrical charges in real-time.
“At $0.02/kilowatt hour (kWh), energy wasn’t a big issue, but now at $ 0.145/kWh, it represents a significant operating burden,” said Vito Lampugnano, GCS president. “Calculations after the control system upgrade showed roughly 960 kW were load shed, which calculates into a savings of approximately $125,000 per year in utility charges.”
To achieve savings, GCS implemented a two-phase approach: load shedding and load shifting.
Phase 1: Load shedding
During phase 1 operations, the facility’s electrical system is designed to shed “on” peak loads to take advantage of favorable electric rate schedules. Known as “peak shaving” or “load shedding,” it enables the facility to reduce equipment energy consumption during peak electric utility cost times. During daily load shedding, selected refrigeration equipment and parts of the electrical system are load shed (turned off).
Phase 2: Load shifting
During phase 2 operations, the facility’s energy supply shifts from the electric utility to the on-site generator. This “load shifting” refers to the ability to take the facility off the grid at peak times or at the request of the utility. The refrigeration plant is set up so the local electric utility can ask the facility to go offline during power outages, shortages, and weather-related incidents. During load shift operations, all electrical loads and refrigeration equipment are in full operation, powered by the generator.
A 2 MW generator was installed as part of the expansion along with a 4,000 A main switchgear that was interfaced with the existing switchgear. The generator and switchgear were networked to operate the facility during load shifting. A standby generator originally was used to operate the plant at nominal energy levels during normal power outages; the generator is designed as a full-time run unit. Fuel oil is sent automatically from large storage tanks to the day tanks used to feed the generator.
PROFINET Network, Annual Savings
The national food supplier is equipped with a PROFINET network for their Boca Raton distribution facility. GCS delivered an industrial Ethernet network suitable for energy management. The network upgrade is expected to translate into $125,000 of utility savings per year. This installation did not use PROFIenergy, a PROFIBUS & PROFINET International (PI) energy management application profile for PROFINET. Future installations using PROFIenergy would allow the food supplier to realize more savings. Devices using the profile could be programmed to go into an energy-saving sleep mode when not in use. The profile could help with extracting appropriate data from the network and with the application of energy management algorithms.