Energy Modeling Challenge: Net Zero Hospital
Published by Joanne Choi
Can a hospital be net zero energy? Eight energy modeling teams all using different energy modeling software tried to find out by participating in this year’s ASHRAE LowDown Showdown Energy Modeling Challenge. The challenge was held in conjunction with the ASHRAE and IBPSA-USA Simbuild 2016: Building Performance Modeling Conference this past August.
I, along with my fellow colleagues, Igor Seryapin and Irina Susorova from Cyclone, participated as part of the IES team, Insane Energy Savers, which won Most Innovative Workflow! Other team members included Kent Beason, Cory Duggin, Alexandra Gramling, Ken Griffin, Amy Jarvis, Shona O’Dea, Tristan Truyens, Brian Tysoe, Scott West, and Xiangjin Yang, with Megan Tosh from IES as the team coach.
The task was to model a 50,000 sf, three-story outpatient health care facility located in Omaha, Nebraska to be net zero (click here for more details on the requirements). This year’s task was definitely a tall order because hospitals typically have a high energy demand, have critical zones, and run 24/7, and Omaha’s climate zone has a significant heating season. Read on to see how my team, the Insane Energy Savers, rose up to the challenge!
First, the project building layout was re-designed to reduce heating gain and loss and take advantage of natural ventilation. The building was developed along an east-west axis to reduce direct solar heat gains, with stair stepping on the south facade to provide self-shading in the summer and passive heating in the winter, and glazing individualized per façade orientation to reduce direct solar heat gain while maximizing passive solar heating and daylighting. The building is also oriented NNW (-20°) for optimal wind exposure.
All critical spaces were placed on the 1st floor, while all non-critical spaces were moved to the 2nd and 3rd floors to allow for a 2-story atrium for daylighting and natural ventilation for the exam rooms and office spaces along the perimeter of the top two floors.
Envelope and Loads.
After optimizing the building layout, a high efficiency envelope further reduced heat loss.
Interior loads were reduced with high-performance LED lighting and occupancy sensors.
Heating and cooling were designed to be provided by a water-cooled, ground-coupled VRV system. Due to the critical zones on the 1st floor, however, the HVAC system was separated between the 1st floor and 2nd-3rd floors. The 1st floor system consists of a dedicated outside air system (DOAS) coupled with earth tubes for precooling and preheating of ventilation air, and the 2nd-3rd floor system consists of a separate DOAS coupled with a transpired solar collector for preheating.
Photovoltaic panels on the sloped roof of the atrium and on-site wind turbines were used to generate the energy required to get to net zero.
It was a challenging task, but an amazing experience being able to collaborate with talented team members from various companies (in both the U.S. and Canada!). We worked hard and brought together our different backgrounds and expertise with energy modeling to design a great net zero outpatient facility.
It was also exciting to see how different and innovative the other designs were from the other seven teams (check them out here!). It just shows how many different ways a building can be optimized to be more energy efficient, and how energy modeling can help us get there.