Maria-Paz Gutierrez University of California, Berkeley
The objective of this proposal is to establish self-active building envelope regulation systems (SABERs) by integrating optical and hygrothermal sensor and actuator networks on a thin membrane. The system is specifically designed for lightweight membrane applications such as deployable emergency housing in tropical climates with the aim to supplant the use of traditional air conditioning systems responsible for the most significant energy expenditure in built environments in these regions. The expected outcome of this research is the development of a membrane prototype that consists of a self-activated optomechanical sensor/actuator polymeric network that controls airflow due to the temperature, light and humidity changes. It is composed by activating air mechanics (ventilation and dehumidification) though microvalves controlled by integrated optomechanical and hygrothermal sensors and actuators associated to an internal desiccant membrane to block moisture. The second phase of the research will test the prototype?s ventilation rates, light transmission control efficiency, water vapor adsorption in order to evaluate the system?s ability to facilitate climatic comfort.
SABERs will provide a basis for the future development of newly integrated environmental sensor technologies for thin film building membranes applicable to building climatic regulation (light and hygrothermal). Self-activated architectural membranes of thin and flexible constitution bring forth advantageous weight reduction, functional broad applicability, low structural impact, and higher calibration sensitivity.
Background and Motivation: The U.S. Energy Information Administration diagnosed in 2000 that buildings in this country are the largest responsible sector for energy consumption and carbon emission, accounting for almost half of its total expenditure. Space conditioning accounts, in the average American home, for over 50% of this energy use. The bulk of this energy expenditure is needed to compensate for heat and cooling losses that occur through the building envelope. These patterns are quite similar throughout the world where space conditioning is also the key factor of energy expenditure in the construction sector. The need is particularly strong in developing countries located in tropical climates, where the cost of energy used for climatic conditioning is expected to be five times higher than those of developing nations. Most current building envelopes have separate controls for environmental flows such as humidity, cooling, and light transmission that lack precision and are difficult to calibrate. The climatic self-regulation of building envelopes can reduce the impact of inefficient, artificial space conditioning. We have developed a biologically inspired optical and hygrothermal material-based Self-Activated Building Envelope Regulation System ("SABERs") that has the potential to replace expensive and large robotic/mechanical systems. SABERs provides a basis for the future development of innovative building membranes with smart integrated environmental sensors and actuators. Our research has established the basis for an enclosure system can control increased air intake associated with an internal dehumidification membrane - employing integrated material sensor technologies through temperature, relative humidity and spectral selectivity, creating an alternative to traditional air conditioning systems. Self-regulated biologically inspired building envelopes with a hygrothermal control can radically innovate current conditioning technology. Key Outcomes: Building membranes must selectively control the transfer of humidity, light, air, and temperature while resisting weathering. Architectural membranes with self-actuation capabilities can be highly effective for sustainable indoor climate regulation. With this purpose, we have established SABERs, a temperature responsive membrane with pores which open of fully close based on temperature changes. Through our research we have designed and analyzed systematically the volume change of the temperature dependent pore opening based on height difference between middle and top layer. SABERs comprises of an optimized geometry of the hydro-thermal responsive Poly isopropylamide (PNIPAM) hydrogel material yielded a pore with an asymmetrical thickness d (= di / wfilm) of 0.05 to 0.7 to create a stress gradient. Matching the critical temperatures required for human physiological micro-environments, a displacement (DRnorm) is accomplished at T = 20oC to yield a closed pore and a pore diameter of 1.5mm is achieved at T = 40oC. The material mechanism takes 20 minutes to open while complete closure was reached in 10 min. Due to structural stability, the repeated and reversible actuation cycling yielded no unfavorable residual deformation. We expect that by improving curing efficiency and modification of functional groups of PNIPAM, the displacement of the structure can be further optimized. As part of the fabrication research of SABERs our team developed a custom 3D printer that enables elastomeric printing using multiple prototype syringes. Using a material already widely used in construction, the custom extruder was able to print geometries with a wide range of overhangs from 65.5o up to 116.5o through chemical curing without relying on heat, UV radiation, or support material. Early estimates are demonstrating that this 3D printer technology opens new opportunities for low cost and materially efficient fabrication not only for construction applications, but also for elastomeric applications in other fields such as biomedical industry. Opportunities for training and professional development were provided through three academic courses covering the full spectrum of academic level. An interdisciplinary thesis graduate seminar (master level) titled "Elastomers & Nature" that was offered during the spring 2013 semester in the department of architecture at the University of California, Berkeley. This seminar focused on smart and flexible membranes gave students an opportunity to learn about the fabrication and design of smart architectural materials. In this process, students met with scientists and researchers from different departments to explore their interdisciplinary projects. An upper level undergraduate studio course on smart skins, sensors and actuators for pneumatic structures was offered in the fall 2012 semester in the department of architecture at the University of California, Berkeley. SABERs research has been presented at a wide range of scientific, engineering, architecture, and social science forums, nationally and internationally. SABERs present a paradigm shift for sustainable building membranes where through self-regulation climatic control is accomplished.
