Squid-like 'liquid windows' react to environment, saving energy costs
The University of Toronto Engineering researchers have developed a unique system that can reduce the energy costs of heating, cooling, and lighting buildings.
Their inspiration? The color-changing skin of the humble squid. The multilayered fluidic system can reduce energy costs by optimizing the wavelength, intensity, and dispersion of light transmitted through windows.
Buildings use a ton of energy to heat, cool, and illuminate the spaces inside them," recent graduate Raphael Kay, lead author, said in a statement. "If we can strategically control the amount, type, and direction of solar energy that enters our buildings, we can massively reduce the amount of work that we ask heaters, coolers, and lights to do."
The research is published in PNAS.
Design inspiration imbibed from a squid's skin
For now, we have certain 'smart' building technologies, such as automatic blinds or electrochromic windows, that can be used to control the sunlight entering the room. But, according to Kay, these systems are limited as neither can they differentiate between different wavelengths of light nor can they control light distribution flat plastic.
The prototype comprises flat plastic sheets permeated with millimeter-thick channels through which fluids can be pumped. The fluids can be composed of customized pigments, particles, or other molecules to control the kind of light that gets through and the direction of distribution.
These sheets can be combined in a multilayer stack, with each layer responsible for various functions such as "controlling the intensity, filtering the wavelength or tuning the scattering of transmitted light indoors".
This design takes direct inspiration from several species of squid with skin that contains stacked layers of specialized organs, including chromatophores, which control light absorption, and iridophores, which impact reflection and iridescence. These elements work in tandem to generate "unique optical behaviors".
"It’s simple and low-cost, but it also enables incredible combinatorial control. We can design liquid-state, dynamic building facades that do basically anything you’d like to do in terms of their optical properties,” said Kay.
Artificial intelligence to take the research further
Jakubiec built detailed computer models informed by physical properties measures from the prototypes. The team also simulated various control algorithms for activating or deactivating the layers in response to changing ambient conditions.
"If we had just one layer that focuses on modulating the transmission of near-infrared light — so not even touching the visible part of the spectrum— we find that we could save about 25 percent annually on heating, cooling, and lighting energy over a static baseline. If we have two layers, infrared and visible, it’s more like 50 percent. These are very significant savings," said Kay.
An interesting thing to be noted in this research is that though humans designed the control algorithms, optimizing them would be a task for artificial intelligence.
"The idea of a building that can learn, that can adjust this dynamic array on its own to optimize for seasonal and daily changes in solar conditions, is very exciting for us," said Hatton.
"We are also working on how to scale this up effectively so that you could actually cover a whole building. That will take work but given that this can all be done with simple, non-toxic, low-cost materials, it’s a challenge that can be solved," he said.
Hatton hopes their research will be a stepping stone towards more creative methods of managing energy in buildings.
Indoor climate control is among the most energy-intensive activities conducted by humans. A building facade that can achieve versatile climate control directly, through independent and multifunctional optical reconfigurations, could significantly reduce this energy footprint, and its development represents a pertinent unmet challenge toward global sustainability. Drawing from optically adaptive multilayer skins within biological organisms, we report a multilayered millifluidic interface for achieving a comprehensive suite of independent optical responses in buildings. We digitally control the flow of aqueous solutions within confined milliscale channels, demonstrating independent command over total transmitted light intensity (95% modulation between 250 and 2,500 nm), near-infrared-selective absorption (70% modulation between 740 and 2,500 nm), and dispersion (scattering). This combinatorial optical tunability enables configurable optimization of the amount, wavelength, and position of transmitted solar radiation within buildings over time, resulting in annual modeled energy reductions of more than 43% over existing technologies. Our scalable “optofluidic” platform, leveraging a versatile range of aqueous chemistries, may represent a general solution for the climate control of buildings.
Akhlesh Lakhtakia, Evan Pugh University Professor, has received a $300,000 grant from the Criminal Investigations and Network Analysis Center to explore a technique for creating 3D holograms of fingerprints.