Land O' Lakes, Inc. is committed to environmental stewardship – leveraging sound science and state-of-the-art technologies to improve sustainability and conserve natural resources in its many operations throughout the globe. The company took steps to exemplify this commitment by improving energy efficiency at its corporate headquarters in Arden Hills, Minnesota.The majority of the headquarters' chilled water needs are handled by a single, closed-loop driven by a central chilling plant. The plant features two 300-ton centrifugal chillers (600 tons total). A total of six air handling units handle the cooling load for the headquarters – four in the office building and two in the R&D facility. When examining the operation of HVAC systems and equipment to identify areas where efficiency could be gained, Land O'Lakes, Inc. energy officials uncovered a costly issue in the AHUs' chilled water coils. Much of the time, Delta T across the coils was lower than its design specifications. In addition to increasing electricity costs due to over-pumping, this resulted in suboptimal heat transfer and significant inefficiency at the building level. After conducting a thorough review of piping, valves, and instrumentation, officials concluded various infrastructural improvements would have to be made—the process of searching for a solution, which eventually led them to the Belimo Energy Valve™.
Requirements: Save Energy, Improve Occupant Comfort, Enhance Operational Visibility
- Increase Delta T in chilled water coils to their design specifications and achieve energy savings through increased pumping efficiency.
- Improve occupant comfort, particularly in the summer months.
- Gain visibility into the operation of air handlers and chilled water coils. In recent years, the chilling plant had been unable to cool the facility adequately. Energy officials at Land O' Lakes, Inc. wanted to determine if that was due to insufficient chilling capacity or inefficiency at the building level.
The Solution
The installation of Belimo Energy Valves on all six (6) of the AHU's chilled water coils (AHU-1 through AHU-6). The valves replaced the 3-way pneumatic valves that were installed when the facility was initially commissioned in 1980. The project also consisted of replacing all chilled water coils in the AHUs and making improvements to piping and adding new motors and variable frequency drives (VFDs) to allow for more precise control of the chilled water loop. Two additional Energy Valves were also installed on hot water coils that supply the R&D facility.
The installation of Belimo Energy Valves on all six (6) of the AHU's chilled water coils (AHU-1 through AHU-6). The valves replaced the 3-way pneumatic valves that were installed when the facility was initially commissioned in 1980. The project also consisted of replacing all chilled water coils in the AHUs and making improvements to piping and adding new motors and variable frequency drives (VFDs) to allow for more precise control of the chilled water loop. Two additional Energy Valves were also installed on hot water coils that supply the R&D facility.
Belimo's Platinum Control Contractor, NAC Mechanical and Electrical Services, performed all mechanical and electrical work. This included the installation of the Energy Valves and all new air handler coils, VFDs, electrical motors, and modifications to pipe and electrical infrastructure.
The Belimo Energy Valve can operate as either a pressure dependent or pressure independent control valve. The mode of operation can be changed through the valve's built-in web-based user interface (UI). Belimo's patented Power Control and Delta T Manager™ can also be enabled or disabled through the UI and allows the valve to achieve a user-defined delta T setpoint.
The intent at Land O' Lakes, Inc. was to operate the Energy Valves in Flow Control Mode (pressure independent) with Delta T Manager enabled. By installing the Energy Valves and making various infrastructural improvements to buildings, Land O' Lakes, Inc. officials aimed to return water at or near the chillers' design temperature. In doing so, the amount of flow required to provide cooling to the building would be substantially reduced, and the central chilled water plant's energy consumption would be decreased. Officials also sought to utilize the Energy Valve diagnostic capabilities to increase visibility into the operation of the cooling system, and more specifically, to determine the specific tonnage per air handler.
The Result
For 31 days, the chilled water operation was monitored, and data recorded to quantify the Energy Valves effect on the chilled water system. Flow savings in the table calculate the difference between actual flow and projected flow. The actual flow is measured by the built-in flow meter. Projected flow is determined by calculating the flow based on the valve position requested by the DDC system versus the actual valve position. To summarize, the data collected from the six Belimo Energy Valves indicate a potential flow savings of 6,210,964 gallons of pumped water over two months (June to August). Measurements also showed an increase Delta T closer to the design specifications of the chilled water plant, resulting in optimal heat transfer and more efficient chiller operation. In previous years, the lowest discharge air temperature that could be achieved at the facility was approximately 58°F (14.5°C). After the Energy Valves were installed, discharge air temperature as low as 52°F (11°C) was observed. Overall, the installation of the Energy Valves, coupled with various infrastructural improvements to building cooling systems, helped Land O' Lakes, Inc. cut kilowatt usage in July and August by roughly 15% when compared to the same months the previous year. The hot water Energy Valves installed at the R & D facility will be monitored throughout the upcoming heating season. Data will be recorded to quantify their impact on energy savings.