Smart Mode Control Valve Retrofit at CSU Dominguez Hills
A pilot project at CSU Dominguez Hills demonstrated the potential for energy savings and improved diagnostics by installing advanced chilled water valves having “smart mode” operation. The new valves reduced central plant pumping and chilled water energy, and also provide improved performance data to facilities staff. The pilot was supported by Southern California Edison’s Emerging Technologies program, which covered installation costs, energy analytics and evaluation of the results. The manufacturer of the valves donated the equipment, resulting in no hard costs to campus, yet providing ongoing energy savings and a technology assessment that may be useful to other campuses and utility customers.
This pilot evaluated smart-mode chilled water valves, which provide advanced sensing and actuation to save energy and also improve campus diagnostic capabilities.
The new valve technology addresses the potential inefficiencies that result when temperature differentials of central plant chilled water do not match design parameters of components on the loop. Optimizing the temperature differential between supply and return water (delta-T) is important to manage pump energy, motor longevity, and system stability. Many campuses still rely on pneumatic or first generation direct digital controls (DDC) on air handlers. These may be coupled with older ‘pressure dependent’ chilled water valves that do not react to load requirements efficiently. Newer VAV systems use ‘pressure independent’ valves that control flow based on a control signal, an improvement but still far from optimal, especially at partial load conditions at which buildings commonly operate.
The new smart-mode valve (SMV) devices, Belimo Energy Valves, measure both water temperature and flow to determine the heat transfer within an air-handling unit (AHU). The devices have integrated delta-T management logic, which works in conjunction with building management systems to improve energy performance and to serve other functions, such as maintenance and troubleshooting. The valves apply full-range control to match flows with load conditions in the spaces to maintain the desired delta-T. In addition to energy savings, the SMVs are less likely to produce the overcooling that may occur with pressure dependent valves, and may result in improved occupant comfort.
Belmo Energy Valves were evaluated in a pilot installation at CSU Dominguez Hills.
For the pilot at CSU Dominguez Hills, six SMVs were installed in the Student Health Center and Welch Hall, in three AHUs per building. A third-party contractor installed the equipment, campus staff wired and programmed the valves, and energy analytics were provided by EcoVox. After installation and commissioning were completed, three monitoring periods were established, each lasting a minimum of two weeks. In the first baseline period, the valves were set to operate in the conventional (and generally least efficient) pressure-dependent mode. In the second period, they operated in pressure-independent mode, and in the third period they operated in full smart mode operation.
Data was collected on the university’s energy management system, and was exported to a third party for evaluation. The data was normalized to account for the outside air temperature differences between the three periods. Results in both buildings were very promising. For the smaller Student Health Center, which operates 5:00 am to 6:00 pm only on weekdays, cooling savings in smart mode was 11 percent compared to the baseline. In this building, there was little difference between pressure independent and smart mode, in fact, the latter was slightly less efficient. In the larger Welch Hall, which operates 24/7, cooling savings in smart mode was 22 percent. (The pressure independent mode provided no savings.) Extrapolated to a full year, utility cost savings are estimated to be $19,600 annually for the two buildings.
The technology offers benefits besides the cooling energy savings. For example, it provides additional data that is useful for building energy managers and central plant managers. During the few weeks of these tests, data from the valves helped campus building operators to identify problems both at the scale of the individual buildings and at the central plant. Kenny Keeton, Central Plant and Energy Manager, notes that “the valves give us good visibility into how the system is working. Before, with just the mechanical valves, problems were hard to find, as there was no metering at the level of individual buildings. Now all the points go into the Metasys system, where we can see the data live, and can go to the AHU and see if GPM is 30 when it should be 300, now we can diagnose problems.”
The final evaluation report (not released publicly at the time of this writing) outlines technology benefits, including data management, troubleshooting, leak detection, and potential demand reduction. Although savings from this technology will vary based on operational considerations, the report conservatively estimates average savings of nine percent across much of California.
Images copyright CSU Dominguez Hills (top) and Belmo (inset).