Boston’s Fraunhofer CSE demonstrates how energy-efficient technologies can be adapted for existing buildings
The science of heating and cooling.
Part of Boston’s 1,000-acre Innovation District, the Fraunhofer Center for Sustainable Energy Systems’ Building Technology Showcase is a renovated six-story, three-bay loft structure originally built in 1913 for wholesale leather merchant W. Herbert Abbot. Fraunhofer CSE worked with the Fort Point Channel Landmark District Commission and the National Park Service’s Historic Preservation Program to retrofit the building with energy-efficient technologies while still respecting its character. Researchers and staff moved into the building in April.
“Due to the very large installed base of existing buildings, increasing the scale and depth of energy-saving retrofits is essential to achieving the United States’ energy efficiency and climate change mitigation goals,” explains Dr. Kurt Roth, Fraunhofer CSE’s director of building energy technology. “In particular, an intense need exists to develop, test, evaluate and demonstrate emerging energy-saving technology practices for existing buildings that can deliver significant energy savings at a reasonable cost, while enhancing the quality of the built environment and maintaining each building’s architectural qualities.”
Founded in 2008 and supported by the Massachusetts government, Fraunhofer CSE is an applied research and development laboratory dedicated to accelerating the commercialization of clean energy technologies. To accomplish this goal, it engages in collaborative research and development with private companies, government entities and academic institutions, Roth says.
It is part of an international research network spearheaded by Germany’s nonprofit Fraunhofer Society, Europe’s largest contract research and development organization. In Germany, the Fraunhofer CSE partners with the Fraunhofer Institute for Solar Energy Systems in Freiburg and the Fraunhofer Institute for Building Physics in Stuttgart.
Using scientific research to understand building performance is the core of the CSE’s mission: To accelerate the development and commercialization of energy-saving building technologies and practices at scale.
“We typically take a systems perspective in our projects and often evaluate the impact of technologies not only on a specific energy end-use, such as HVAC, but also their whole-building impact,” Roth explains. “We do this by first understanding how the performance of different technologies depends on different variables.
“With a sound understanding of the underlying physics of technologies, we can then apply whole-building energy models to evaluate the performance of different systems in different building types and climates, as well as for a range of occupant behaviors.”
In the CSE Building Technology Showcase, the building automation system measures many building performance parameters, he adds. Researchers use them to evaluate the performance of different HVAC components and systems. An ongoing commissioning system monitors the performance of the HVAC systems. As it detects and diagnoses less-than-optimal operations, it provides recommendations for improving their performance.
One of Fraunhofer CSE’s goals is to test a radiant heating/cooling system and see how well each technology works. Many homes and buildings in this country that have radiant floor heating systems also have separate air-conditioning and ventilation systems. One system that can provide heating and cooling efficiently is a more economical option for building owners than installing separate systems.
Viega’s ProRadiant heating and cooling systems are installed on the first and third floors of the building — a total of 18,000 sq. ft. — with 16,000 ft. of 1/2 in. ViegaPEX barrier tubing, 11 manifolds and six enhanced mixing stations to integrate into the Siemens building management system. Quincy, Mass.-based Northeastern Mechanical installed the radiant floor system.
The German connection is how Viega came to be a partner for the new Fraunhofer CSE building, says Rudi Tillman, a Viega sales engineer who was involved in the beginning stages of the project. Viega America’s parent company, The Viega Group, has partnered with the Fraunhofer Society on many joint research projects in Germany, so it was open to collaborating with the research institution again when the decision was made to build the CSE’s Building Technology Showcase in Boston.
“The partnership is twofold,” he explains. “The first part is we want to promote technology to anyone in the industry — architects, contractors and building owners. The second part is we want a ‘living lab’ to do applied research.”
The mixing stations allow for heating and cooling control in each zone, making occupants much more comfortable throughout the building, Tillman notes.
“In any kind of big commercial building, on one end people are cold and on the other end people are hot,” he says. “In the CSE building, there is no central mixing device. Instead, it has what I call ‘local mixing’ or decentralized mixing. This helps maximize the thermal comfort for the people working in the building.”
The mixing stations also alleviated the engineer’s concerns with the radiant cooling system and possible condensation in the floor, says David Desjardins, Viega’s ProRadiant project manager.
“Many times in a commercial building you can put positive pressure and excess air in the environment to control the humidity in the air and control the water temperature going to the floor, eliminating condensation,” he explains. “With this building, concerns were expressed about the leakage of air, especially in the lobby vestibule and the back loading dock. So the ability to easily adjust water temperatures in different areas of the building was needed.”
Other heating technology products donated to the research center were Taco distribution systems and Smith’s Environmental Products high-efficiency radiant baseboards.
Since the building envelope can be a major source of heat loss, insulation techniques also are being studied at CSE — vacuum insulation panels from Dow Corning, rock wool by Roxul and polyisocyanurate roof insulation by Hunter Panel.
Roth notes that current, planned and past HVAC research projects at Fraunhofer CSE focus on: ductless minisplit heat pumps; displacement ventilation (cooling); natural and mixed-mode ventilation; programmable thermostat usage and the application of multiple HVAC technologies together (e.g., radiant floor cooling with displacement ventilation).
“Our group works at the intersection of people and technology — many problems with newer technologies occur there,” he adds. “Accordingly, our HVAC research often has a human factors/behavior dimension, such as comfort, occupant/household acceptance and controls.”
The CSE Building Technology Showcase is examining several types of hydronic cooling systems to see how well they improve efficiency and lower energy costs.
“Radiant slab cooling, chilled beams, chilled sails and chilled radiant panels are all low-lift cooling technologies, that is, they typically operate with a significantly higher supply water temperature than a conventional air-based system,” Roth says. “This reduces the temperature ‘lift’ of the chiller, improving chiller efficiency.”
- Chilled beams. Passive chilled beams have a heat exchanger with chilled water flowing through it, he explains, cooling the air in contact with the heat exchanger. This cooler, denser air descends, which creates a natural convection circuit that causes warmer room air to flow into the beam’s heat exchanger.
Active chilled beams, donated by Price Industries, distribute supply air through the beams, which encourages the additional flow of room air through a heat exchanger that conditions the air. This increases their capacity relative to passive chilled beams. Active chilled beams and sails form a major part of the Fraunhofer CSE’s hydronic cooling system.
- Chilled radiant panels/sails. Chilled radiant panels and chilled sails, also donated by Price Industries, are both hydronic passive cooling elements — they do not use forced airflow to enhance heat transfer, Roth notes. They are cooled with water to allow them to absorb heat from the surrounding environment. Chilled sails typically having regular spaces between the radiant surfaces. Both transfer heat via radiation and convective heat transfer, providing the same level of comfort to occupants as conventional air conditioning.
Ventilation technologies studied at CSE include energy recovery ventilation, which preconditions the air by running it through a heat exchanger. Heat and moisture are exchanged between the outdoor air drawn into the building and the air being exhausted from the building. This cools and dehumidifies the air, lowering the perceived temperature of the building. Not only can this conserve energy, it can reduce building costs by decreasing the amount of HVAC equipment installed.
A demand-controlled ventilation system measures the CO2 levels in the building, enabling it to estimate how many people are in the building and adjust the intake of outdoor air accordingly. Variable-frequency drives from Taco and Yaskawa help with the adjustment by allowing pumps and fans to run slower or faster, depending on current loads rather than on a fixed speed.