ECO-STRUCTURE recently caught up with David Cook, project engineer for Hale Pilihonua, the University of Hawaii’s entry for the U.S. Department of Energy’s 2011 Solar Decathlon. (The project was withdrawn from the competition before installation in Washington, D.C. due to financial challenges.)
How is your solar paneling unique?
Our solar paneling is integrated into a canopy of panels and shading louvers that cloaks the main structure of the house, harvesting energy, filtering daylight, and giving the house its distinctive form. Supported by a free-form space frame connected to the shell of the main structure, the canopy is doubly curved and smoothly morphs from one end of the house to the other. The precise form and dimensions of the canopy were engineered for optimum solar-collection efficiency within the boundaries of the desired aesthetic, and the resulting canopy-integrated solar-panel array was found to represent the best compromise between aesthetic and functional performance.
What other sustainable features have you incorporated into your design?
Insulation mounted on a thermally broken steel frame and sandwiched between two layers of fiber-reinforced polymer skin constitutes a translucent yet well-insulated tubular shell that enables natural daylighting of the entire house without sacrificing thermal performance. The natural lighting of the house can be controlled by the external canopy of operable louvers. Thermally broken aluminum-frame opening glass walls at both ends of the shell can be opened to take full advantage of natural cross ventilation. When mechanical climate control is necessary, a high-efficiency water-source heat pump connected to a 1,500-gallon tank of water and phase-change material located under the floor (which also serves as ballast to resist overturning in high wind) supplies conditioned air into the living space through diffusers in the floor. High-efficiency LEDs embedded in the shell can be controlled using motion tracking and recognition technology to make the shell glow with a desired brightness—a technology both convenient and energy-efficient. In addition, the house is constructed from long-lasting materials that are resistant to rot, corrosion and insects—common problems in the tropics.
What was the inspiration of your design, and does it display any regional influences?
We were inspired by rolling waves, tropical flora and fauna, and other prominent elements of Hawaii's ecology. The multilayered light-filtration concept creates diffuse shadows, as though cast by a grove of bamboo. With its durable materials, light-filtering devices, water-tight construction, and stable tectonics, the design also addresses the challenges of rot, corrosion, insects, high solar radiation, flooding and hurricanes posed by the tropical environment.
How has the new affordability criteria affected the design of your house?
Like many other teams, we found it difficult to meet the new affordability criteria and still pursue some of our more interesting design ambitions. In our case, the latter won over the former. We realized early on that our house would be costly, but we viewed this as an indication of its sophistication and innovation, and still think that it could be affordably mass-produced.
What will happen to the house after the Solar Decathlon?
The house is supposed to be installed in the private museum of one of our sponsors, in Pusan, Korea. This will provide a semipermanent home for the house and avoid any potential issues regarding disassembly and the disposal or recycling of materials.