To optimise the efficiency of the chiller and heating system at Northeastern University in Boston, global engineering firm, Arup, has installed a heat-recovery chiller.
It can simultaneously heat hot water and generate chilled water. This reduces the run-time of the boilers for laboratory re-heat in the summer and shoulder seasons and for pre-heat of the domestic and laboratory hot water systems.
Details of the project were made available last month when Arup celebrated the opening of the Interdisciplinary Science and Engineering Complex (ISEC) at the university.
Arup was selected by the architecture firm Payette to provide mechanical, electrical, and plumbing engineering, as well as energy modeling, façade consulting, sustainability and lighting design services for the 234,000-square-foot project.
Speaking at the event, Arup project manager, Julian Astbury, described the project as extraordinary.
"Sharing Arup's resources and expertise in sustainability and technology with the team made the experience a true collaborative process—a work of total design,” Astbury said.
Arup principal in charge, Mark Walsh-Cooke, said the facilities department at Northeastern wanted the most energy-efficient building possible.
By using advanced energy modeling software and building information modeling (BIM) early in the design process and holding biweekly workshop meetings with the architects and university representatives, Arup empowered the client to make better, more informed decisions about the design, enabling them to reach their sustainability goals.
The Massachusetts Stretch Energy Code calls for new buildings to perform 20 per cent better than required by base code.
The ISEC surpasses this requirement, achieving 33 per cent energy-cost savings over code and 75 per cent energy savings compared to typical laboratory performance. To accomplish this, Astbury said Arup engineered several major energy conservation measures.
He said the cascade air system is the biggest contributor to energy savings.
"This technology was new to the client and contractor, so our advanced energy modeling software studies were critical," Astbury said.
“In a typical scenario, laboratories have a dedicated HVAC system, an expensive feature to construct and operate.
“At the ISEC, the cascade system recovers conditioned air from the offices and atrium of the building, then transfers it to the lab, saving energy and reducing costs.”
Arup also used performance and life-cycle analysis to optimize the façade design, ensuring both occupant comfort and energy efficiency.
The northern part of the ISEC complex, which houses the energy intensive labs, is the focus of thermal improvements; at the southern exposure (where low-energy functions such as offices are located), triple-glazed windows and a shading system work to maximize daylight while minimizing energy consumption.
“Using active chilled beam technology significantly reduces the energy consumption compared to conventional air conditioning,” Astbury said.
In this system, supply air to the space is directed through nozzels on either side of a heat exchanger coil, creating a pressure difference. This pressure difference pulls air from the space over the coil, cooling or heating it, and then mixes with the supply air to be delivered to the space.
“Arup's comfort-modeling software balanced the downdraft and the ambient temperature to ensure a pleasant environment,” he said.
Arup also designed a hydronic run-around coil system to recovery energy from the lab exhaust air to pre-condition the outdoor air, targeting the heating as needed to either the offices or labs, and optimizing the efficiency of the system.
The coils are designed to minimize the size of the fan motor and extract as much energy as practical before the exhaust is discharged.
The winter outdoor air heating demand to the atrium is reduced by using a passive solar collector to preheat the outdoor air using radiant energy from the sun.