Decarbonizing Healthcare with Zero-carbon Reheat Systems

An innovative integrated AHU HEDS technology for dehumidification.

Front of Thorton Hospital AHU 12 and 13 HEDS FDA roof top HEDS Puerto Rico Rooftop installation site for HEDS AHU at Thorton Hospital.

Electric Power Research Institute, Inc.


Palo Alto, CA

Recipient Location


Senate District


Assembly District



Amount Spent



Project Status

Project Update

The existing HVAC system is being monitored following the pre-installation M&V plan. The construction documentation (CD) package for the replacement AHUs is complete and is being submitted to OSHPD in conjunction with an increased cost funding approval request to the Chancellor's office due to COVID, supply chain issues and a change in the scope of work.

The Issue

Healthcare buildings are the second largest consumer of energy per unit of floor area of all building types. As much as 50 percent of energy use in hospitals is for space heating and cooling. In the United States, the health care industry accounts for nearly 10 percent of total GHG emissions and between 2006 and 2016, these emissions have increased by 30 percent. The energy needed to precool hot humid air, dehumidify and reheat, is inefficient. California's energy goals cannot be fully met without addressing inefficiencies associated with air dehumidification and reheat in HVAC systems. A successful demonstration of the high efficiency dehumidification system integrated with the air handling unit will provide a working credible example to hospital facilities and HVAC design communities, who need evidence to support modern, efficient technologies.

Project Innovation

Sustaining hygienic conditioned spaces is critical to the indoor air quality of healthcare facilities. This project will will replace aging conventional Air Handling Units (AHUs) and demonstrate a more energy-efficient and effective ventilation system at a San Diego hospital. The AHUs will be equipped with an energy recovery technology called the High Efficiency Dehumidification System (HEDS). The HEDS technology substantially reduces or completely eliminates the need to provide new, natural gas-sourced energy to the reheat process that is part of relative humidity control in HVAC systems. By removing heat from the chilled water return line, HEDS also substantially reduces the thermal load on electric chillers, further increasing natural gas savings at the generation source. HEDS systems also reduce fan and pump requirements and reduce maintenance costs because of their simple construction with fewer moving parts than competing systems. The dual goal is to reduce or eliminate natural gas use for the cooling/dehumidification/reheat process. This easily accessible high-stakes working demonstration could help HVAC design and procurement communities overcome the reluctance of adopting new innovative technologies.

Project Goals

Demonstrate new, high-efficiency technology for air dehumidification is a better option than its conventional air handlers
Share results of technology and benefits with other building owners, energy managers and HVAC contractors.
Demonstrate an overall 30% reduction in gas use compared to a standard system with simple payback of less than 7 years
Move TRL of the HEDS technology from 7 to 9.

Project Benefits

The proposed HEDS AHU can reduce the cooling and re-heating load in large commercial buildings, such as hospitals. Reducing or eliminating the re-heat load is a major game changer and will result in year round reductions in natural gas use for hospitals and other large buildings. In addition to reducing or eliminating reheat, this technology has the potential of offsetting cooling energy use. The net impact of this project will be lower operating costs for building operators and reducing in greenhouse gas and other emissions.

Lower Costs


The system provides energy savings over conventional AHUs. In the right climate, the system will not require a boiler, and have indirect savings from smaller cooling fans and circulation pumps with lower maintenance requirements

Economic Development

Economic Development

Implementation of the technology in CA commercial buildings could result in over $1 B in savings.

Energy Security

Energy Security

The proposed system lowers cooling load by 24% and can potentially completely eliminate the need for fossil fuel fired boilers for reheating, thus improving energy security.

Environmental & Public Health

Environmental Sustainability

The system reduces greenhouse gas emission by over 4 M tons of CO2 and over 4K tons of NOx due to efficiencies that are higher than traditional AHUs and may eliminate boiler use. The system mitigates mold and corrosion.

Greater Reliability


The system can reduce the electricity peak cooling load, greatly benefitting a capacity-constrained system. The system also has no moving parts, which greatly reduces the need for maintenance and increases system reliability.

Increase Safety


The HEDS AHU mitigates mold and corrosion in buildings, which is critical for the health and safety of occupants within buildings, especially in healthcare facilities.

Key Project Members

Kazden Headshot

Agatha Kazdan

Technical Leader / Project Manager
Electric Power Research Institute, Inc. (EPRI)
Project Member

Jeanie Mar

CEC Project Manager

Contact the Team