UC Boulder’s Solar Decathlon Entry Open to Public

Solar Decathlon entry, CU Boulder

As of April 22, the University of Colorado at Boulder offers tours of its 2007 entry in the Solar Decathlon competition, which took third place in the engineering category and seventh place overall in this nationwide design competition for solar dwellings, sponsored yearly by the Departmant of Energy. The most original aspect is the building’s provision for heating, ventilating, and air-conditioning. Here is the team’s description:

The heat pump connected between the hot and cold tanks will heat the hot tank and cool the cold tank at very high efficiency. The storage tanks enhance the efficiency of the system compared to a conventional heat pump by optimizing the time – and temperatures – at which energy is transferred to and from the outdoor environment. For example, in winter, the main heating needs occur at night when it is coldest outdoors… The storage tanks in our system allow us to bridge the gap between day and night to improve system efficiency. The cold tank even includes encapsulated ice to expand the thermal storage capacity with a relatively small tank volume.

While it’s true that the system works optimally in a Colorado-like climate, that climate does prevail over much of the western part of the United States. Generally, it’s dry, the sun shines all day, and at night the temperature drops dramatically. Like buildings equipped with the passive systems we’ve been used to, this house makes use of the natural temperature variations, only it uses mechanical systems to manage the transfer of energy. The peculiarities of the climate make it feasible to use radiant cooling.

The house contains a modular, prefabricated engineering spine, made from surplus shipping containers, which holds the heat exchangers along with the kitchen, bathroom, laundry and equipment spaces. Since the windows are high-performance and the house is well insulated, the perimeters can take care of themselves, so the centralizing of heat and cold at the spine provides several advantages.

The design team used EnergyPlus energy simulation software to predict air and surface temperatures and operative temperatures, and PHOENICS, a program that anaylzes flow and stress, and TRNSYS, which simulates the transient performance of thermal energy systems.

Solar energy heating and cooling systems are described in lavish detail in the Services section of Architectural Graphic Standards, 11th Edition. After structural considerations, HVAC is considered the second most important area of building design to get right, since it impacts the budget so greatly both in the construction phase and ever afterwards in the operating expense due to energy use. It can occupy as much as 10% of a building’s floor area, and deeply affect the building’s aesthetics. The comfort of occupants is of course a primary consideration in most buildings, and can be of critical importance when a building is used for storage, processing or manufacturing.

Now that the CU Boulder team’s house is back from the competition in Washington, D.C., and various other travels, it will be made available not only for tours but even for private parties — by reservation only, of course.

SOURCE: “Heat from Ice?” (no author or date given)
photo courtesy of Jeff Kubina , used under this Creative Commons license

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