By Bryan Lang, PE
Sutter Health demonstrated commitment to energy savings with a goal to reduce the Energy Use Intensity (EUI) of their acute care facilities to 200 kBtu/ft2 by 2030. As one early step of this commitment, the network hired ETC Group to perform a Retrocommissioning (RCx) Assessment for the Eden Medical Center. This 130-bed, 230,000-sqft acute care hospital, located in Castro Valley, CA, had a higher EUI than comparable facilities in the Sutter network and was identified as a good candidate for achieving energy savings. ETC Group’s focus was to identify measures utilizing existing equipment and systems for low-cost energy savings.
Bryan Lang, PE
Eden Medical Center’s mechanical HVAC equipment is summarized as follows:
- Water-cooled constant-primary-variable-secondary chilled water plant
- Constant-primary-variable-secondary heating hot water plant
- Eight (8) single-duct VAV air handlers with terminal hot water reheat
ETC Group’s preliminary audit identified energy saving measures totaling nearly $200,000 per year in utility savings. Project savings comprised of 1,020,000 kWh and 7,830 dTh per year, reducing the facility EUI by 15%.
The suggested energy conservation measures included the following:
- Repairing airside economizers
- Revising central plant condenser water temperature and cooling tower fan controls
- Implementing chilled water supply temperature and pressure setpoint resets
- Programming air handler supply air temperature setpoint resets based on VAV feedback
Figure 1: Average Baseline Total Building Power (kW) by Time-of-Day and Outside Air Temperature
After Sutter Health decided to proceed with the energy project identified in the preliminary audit, detailed sequences of operation were drafted for all air handlers and the chilled water plant to operate according to the intent of the measures identified.
All proposed operational changes were approved by Eden Medical Center’s facility staff and reviewed with the commissioning agent and BAS programmer to confirm all intentions and operating modes were met.
Once the new sequences of operation were complete and approved, the programmer spent one week pre-programming the changes to be made in the existing logic of the air handlers and the chiller plant.
Actual implementation occurred over a two-week dedicated effort. The first week was spent implementing the new programs and the second week utilized for testing, commissioning, and tuning of setpoint reset responses and staging timers.
The decrease in energy from the baseline performance was apparent immediately and occurs under almost all operating conditions. Verified energy savings achieved total over $240,000 per year.
Figure 2: Implementation Day – Example Changes to Equipment Performance
Figure 3: Average Retrofit Total Building Power (kW) by Time-of-Day and Outside Air Temperature
||$246,000 per year
|Total Project Cost:
|Natural Gas Reduction:
|Site EUI Reduction:
|Carbon Dioxide (CO2) Reduction:
||870 tons per year
||*Equivalent to planting 13,000 trees
Figure 4: Average Total Building Power Draw Savings at a Specific Hour and Temperature