The challenge
HVAC is the largest energy use in most hospitals. Across US inpatient facilities it accounts for about 52% of total energy (space heating 29%, ventilation 12% and cooling 11%), based on CBECS data analyzed by Bawaneh et al. (2019), Energies. This figure is a national average, not this site's metered share.
At this New York City cancer center, the 1,200 TR chiller plant ran with static condenser water temperature setpoints that didn't respond to ambient wet-bulb conditions.
Patient safety and indoor air quality requirements in a hospital are non-negotiable, so any change to HVAC control had to hold strict temperature, humidity and filtration conditions.
The project changed one strategy at a live clinical site and measured the result over 12 months.
Site profile
Verified results
Measured over 12 months and validated through Con Edison's RTEM pilot
Savings were measured over a 12-month IPMVP Option B reporting period against a baseline model of plant energy as a function of cooling load and ambient wet-bulb temperature. R² describes how well that baseline model fits the measured data. Carbon is converted at 0.41 tCO2/MWh. No cost saving is reported for this site.
| Outcome | Verified result | Status |
|---|---|---|
| Energy saving | 5.9% reduction in chilled water plant energy | Verified |
| Annual kWh savings | 63,077 kWh per year | Verified |
| Carbon avoided | 26 tCO2 per year | Verified |
| Baseline model fit | R² = 0.987 (12-month IPMVP Option B regression) | Verified |
| Utility validation | Validated through Con Edison's RTEM pilot | Verified |
Verified: measured under IPMVP Option B over 12 months and validated through Con Edison's RTEM pilot.
The Exergenics approach
One strategy at a live clinical site
This project used a single strategy, the Dynamic Condenser Water Reset option. Exergenics generated the reset algorithm from the plant's own data, and it was implemented in the facility's existing BMS. Exergenics doesn't write to the BMS.
Set the clinical boundaries first
Temperature ranges, humidity tolerances and failsafe conditions for the clinical environment went into the model as constraints, so the strategy stays inside the limits the hospital requires.
Dynamic condenser water reset
The algorithm sets the condenser water temperature setpoint from ambient wet-bulb conditions and chiller load. That reduces compressor lift and plant energy without changing the chilled water supply temperature.
Measure for 12 months
Savings were measured over a 12-month IPMVP Option B reporting period. The baseline regression model fit the measured data with an R² of 0.987. The result was validated through Con Edison's RTEM pilot.