Hospital conserves energy by 27% with heat recovery chiller system

Hospital conserves energy by 27% with heat recovery chiller system

FORT BELVOIR, VA. — Scheduled to open in spring 2011, the military community hospital located here will be the first hospital in the country to be built to meet the U.S. Green Building Council LEED Silver requirements and the Energy Policy Act of 2005 regulations, plus it will also incorporate the latest research findings of evidence-based design (EBD).

Since hospitals consume a large amount of energy, building an energy-efficiency medical facility was paramount for this project, along with utilizing water conserving products and systems, while upholding EBD principles.

To provide the best possible healing and working environment for patients, visitors, and staff, hospitals require precise temperature and humidity control, maintained outside air ventilation and proper air pressurization. Air pressurization plays an important part in infection control in modern health care facilities by directing the filtered supply air from the clean areas towards the less-clean or contaminated spaces, thus containing infections and protecting patients from illness. However, this process requires a large amount of air to be circulated 24 hours per day, seven days a week, and the conditioning of the air requires a significant amount of energy.

The Fort Belvoir community hospital will consume 27.6% less energy (based on regulated energy savings) than a typical hospital and will also save approximately 4,000 tons in CO2 emissions.

Besides adhering to LEED Silver requirements, the hospital will meet the Energy Policy Act of 2005, requiring 30% energy reduction when compared to the ASHRAE standard 90.1-2004 baseline, according to Lidia Berger, vice president and eastern director of sustainable design solutions at HDR, the project’s architectural, engineering and consulting firm, based in Omaha, Neb.

Much of the energy savings can be attributed to a Multistack heat recovery chiller system for reheating, high-efficiency variable speed drive chillers and variable air volume devices.

High-efficiency chillers with variable speed drives were selected for the project based on the results of a life-cycle cost study, according to Theodore E. Zsirai, senior vice president of HDR.

“Chillers must be sized for the maximum building cooling load, but most of their operation is at conditions below peak capacity,” explained Zsirai. “To maximize efficiency at a partial or minimum load, variable speed drives are used to reduce impeller speed. This results in a system that consumes much less energy during the year than any other capacity control method.

“Similar to chillers, most fans, pumps, and other turbo machinery seldom operate at peak capacity,” added Zsirai. “By reducing the speed of this equipment when full capacity is not required, overall efficiency is increased, assuring the most cost-effective method of transporting heating and cooling energy to the point of use.”

Modular heat recovery chillers will provide reheat hot water for the facility while producing chilled water to supplement the central utility plant during summer months. During winter months, these chillers will provide a large portion of the building’s hot water heating load.

Waste heat from fan coil units, serving the electrical and communication rooms, water cooled hospital and laboratory equipment, and other process cooling loads, will be used as the energy source for cooling. Additional energy will be derived from the air handling units’ cooling coils.

Instead of using 100% outside air for cooling in the winter, some of the units will operate with minimum outside air. Cooling will then be provided for these air handling units by the heat recovery chillers, transferring the energy to the hot water side.

“The combined heating and cooling system (COP) is estimated to be 5.2 at the maximum 140° F hot water temperature and 45° F chilled water supply,” said Zsirai. “This COP can be increased even further during intermediate seasons by reducing the discharge hot water temperature and increasing the chilled water temperature.”

Building operators will have the option of using either the primary heating boilers in the central utility plant or the heat recovery chillers to provide the most cost-effective operation.

The hospital will also utilize lighting and thermal controls, occupancy sensors, daylight harvesting and control systems to conserve as much energy as possible.

Water Conservation

Low-flow plumbing fixtures, dual flushed water closets and sensor-activated faucets will be utilized in appropriate areas of the hospital. An integrated rainwater and condensate water collection system is able to store up to 160,000 gallons of reusable water. Water will be funneled from the hospital’s swooped roofs, and captured and stored in two large underground cisterns in the hospital’s courtyards.

According to Berger, potable water savings per year will be approximately 1.6 million gallons of water.

“This is a 60-acre site,” explained Berger. “Sixty percent of it will be restored with native and adaptive vegetation. One of our water efficiency strategies comes from the fact that native vegetation typically requires little to no irrigation. All irrigation needs for the site will come from collected rainwater.”

Evidence-based design

Evidence-based design is defined by The Center for Health Design as the process of basing design decisions about the built environment on credible research to achieve the best possible outcomes in patient healing.

Even though it is possible to design and build an energy-efficient hospital that follows EBD, as this project exemplifies, some EBD principles can create challenges when designing mechanical systems.

The Military Health System, along with Tricare Management, the civilian care component of the Military Health System, and Noblis, a non-profit science, technology and strategy organization, reviewed the research results from the last decade and developed four EBD principles to be considered for all Department of Defense projects. The goals are to provide safe and sustainable facilities focused on patient- and family-centered care, provide a positive work environment, and design for maximum standardization, future flexibility and growth.

“Over the last decade, evidence-based design has evolved, almost as its own discipline,” said Barbara Dellinger, eastern director of healthcare interiors at HDR. “Using the latest evidence, many design ‘interventions,’ as the solutions are called, can be applied to help improve efficiency or safety in many areas.”

The EBD requirement that has the greatest impact on mechanical system design is the higher level of air filtration required in areas occupied by immune-deficient patients, according to Zsirai, and there is evidence that using HEPA filters with 99.997% efficiency in filtering the supply air significantly reduce the infection rate of these patients.

HEPA filters reduce infection incidences for immuno-compromised and other high-risk patients at rate of 99.97% (MHS). They will also contribute to the achievement of LEED IEQ Credit 5.

Utilizing low-flow fixtures is also a challenge because of infection control. Laminar flow is needed to prevent bacteria, and potable water is being used for irrigation only due to EBD principles.

“Designing sustainable hospitals can be challenging, mainly because hospitals are already highly regulated facilities,” explained Berger. For example, installing low-flow faucets throughout the hospital was an issue because of infection control.

Once the hospital opens, educational programs will be in place for visitors, staff and the community to learn about the sustainable systems used in the facility. Many of the educational program components are under development right now.

The hospital’s construction phase, managed by the Norfolk, Va., District of the U.S. Army Corps of Engineers, is expected to be completed in late summer 2011. At this time, construction of the 2.7 million-sq.ft. facility is approximately 50% completed. Once finished, the facility will be turned over to the U.S. Army Medical Command to staff and equip for subsequent operation.

The hospital will be part of an integrated health care network providing medical services to the nation’s wounded soldiers and their families. The hospital is one piece of a realignment designed to increase hospital and outpatient care to all service members and veterans under BRAC 2005. Other elements of the health care network include the realignment of Walter Reed Army Medical Center and the Naval National Medical Center in Bethesda, Md.