By Chase Davis
When Duke Health began addressing the need to replace and relocate its existing generators to accommodate facility growth at its main campus in downtown Durham, NC, the healthcare institution partnered with RMF Engineering. Upon further evaluation, Duke Health realized updates were required for not just one building, but rather several buildings across campus that were considered out-of-date. The existing generators lacked the capacity to support the addition of 350 new beds, let alone further growth for the hospital down the line, and required attention to ensure system reliability for the critical healthcare facilities.
Situated within a rapidly growing corridor of North Carolina, Duke Health’s ambitious project required a team that understood the intricacies of a project of this nature and one that was familiar with both Durham and Duke Health. Having a team that specializes in central energy plants and infrastructure, and that has a presence in the city and existing relationship with Duke Health, RMF Engineering was a natural fit, rising to the occasion to design a building that would act as a Generator Hub for the broader healthcare campus. Working with Duke Health alongside project partners BSA LifeStructures, Robins & Morton, Starr Electric, and Thorburn, the firm created a reliable solution that supports 950,000 square feet of new and existing bed towers, with the connections in place to connect another medical office building and surgery center in the near future, with future expansion capacity to connect many more buildings over the coming years. This set Duke Health up for continued success through organizational growth for decades to come.
The 7,000-square-foot Generator Hub building features new paralleling gear, automatic transfer switches, and mechanical spaces on the lower level with three generators and a raised control room on the upper level of this two-story building. The building contains three 2.75-mega-watt diesel combustion generators and was designed to ultimately accommodate three 4-mega-watt generators. This will allow for the connection of future buildings without the burden of additional generators and thus allowing Duke to consolidate its maintenance and operation efforts to focus on a few key assets.
The building is sited adjacent to patient bed locations and a cafeteria, making acoustics and aesthetics critical factors in the design. First, it was decided to generate the power at a medium voltage (12.47 kV) to not only serve the new bed tower located 1,000 feet away, but many future and existing buildings as well. This decision was not made lightly, as Duke did not have in- house medium voltage equipment or staff. RMF worked closely with BSA LifeStructures, project architect, and a landscape architect, to ensure the building was low profile and aesthetically pleasing in an area very visible to patients and staff. Exhaust stacks from each of the three generators run up an exterior chase of the existing building patient tower.
The biggest challenge the team was confronted with was the particular location, which is in a dense area of downtown Durham; facilities like these can’t be placed on top of existing buildings and are not always the most attractive additions to a healthcare campus. After determining the Generator Hub would be supporting multiple buildings and inevitably creating a larger project, the only site available that met the demands was tucked into a nearby area that was already being renovated at the time. Given the limited footprint, the team double-stacked the building, locating the unit substation and mechanicals on the bottom floors and the generators on the top floor.
This approach caused the stack to interrupt sightlines for patients in nearby buildings, which meant extra attention needed to be paid to the building’s exterior facade. With the help of BSA LifeStructures as project architect, the team planned for the new construction to have the same surface finish and detailing of the patient tower to blend the building into its environment. From an aerial perspective, the rooftop is a visually pleasing green space. The building is topped off with a green roof and a rock garden with teal accents and complementary lighting design. The rock garden is dual-purpose, also hiding the roof hatches to be used for future generator replacements.
A key concern for hospital staff of the generator plant was noise pollution. The generators require hundreds of square feet of free louver area to satisfy the high airflow requirements which further complicate noise mitigation. RMF knew that this would require many different techniques including in line attenuators which restrict airflow. The team worked with Thorburn, a specialty acoustic consultant, and a specialized Computational Fluid Dynamics (CFD) subconsultant to review and analyze numerous custom solutions, all of which had impacts to plant footprint and layout. The result was an intensely iterative and collaborative process to come up with a solution that would satisfy plant airflow requirements while minimizing noise pollution and keeping the plant compact yet accessible. Finally, because the Generator Hub was surrounded by tall buildings, the team used CFD analysis to ensure the generator cooling air would not recirculate and overheat.
The Generator Hub was designed to be a “100 year building,” meaning it won’t only stand for 100 years, but it will also be continually operational – a critical assurance for hospitals. For patient safety and wellbeing, at no point can the facility go offline. This hub approach instills confidence in reliability, allowing Duke Health to perform tests weekly while not disrupting hospital operations. RMF worked closely with Duke Health operations to understand all maintenance and testing activities which led to the incorporation of other features such as the spacious and cooled control room, load bank transformer for generator load testing, and temporary generator connection boxes to facilitate all operations over the coming years.
The fast changing nature of healthcare, Duke Health’s expansion plans, and the Generator Hub’s ability to distribute power long distances with medium voltage production meant the team knew capacity would grow sooner than later and the Generator Hub would need to support that. But building a bigger building wouldn’t offer the right solution. RMF opted for a design that could accommodate the largest generators available to allow for the installation of larger generators when the time is right. The design is such that any piece of equipment could be taken offline (planned or unplanned), serviced, upgraded, or replaced without taking the plant out of a state of constant operational readiness.
This project’s success is a result of true collaboration between all project partners, especially Duke Health, setting the stage for the organization’s future. The Generator Hub is prepped for technological advances or campus expansion, enabling Duke Health to accommodate any situation that arises. Beyond redundancy, the resiliency of the system is credited to every single component, including airflow, cooling, fueling, and all the attention to detail. Through expertise and thoroughness, RMF and its partners ensured the Generator Hub was designed successfully so the power never goes offline, ensuring continual hospital operations through hurdles, whether planned or unexpected.
Chase Davis, PE, CEM is an Infrastructure Project Manager at RMF Engineering, based in the Raleigh, NC office. As a mechanical engineer working in RMF’s utility infrastructure group, Chase’s experience includes the analysis, design and construction administration of steam, heating water, chilled water and emergency power generation systems in various campus environments. He has provided services for university, healthcare, industrial and municipal clients. Specific knowledge areas for Chase include fuel systems, steam, hot water, chilled water systems in direct buried, trenched or tunnel installations. Prior to joining RMF in 2014, Chase worked in fuel cell, geothermal power, and with nuclear submarines. He earned a Master of Mechanical Engineering from Rensselaer Polytechnic Institute and holds a Bachelor’s Degree in Mechanical Engineering from the University of Connecticut.