From Scientific American:
In that spirit, the researchers created a super-thin silicone-rubber layer with a network of tiny sealed channels. When the rubber is stretched over a window, it’s completely transparent.
Water running through the channels absorbs heat and transfers it to the outside air. In the researchers’ model, a large window at 100 degrees Fahrenheit can be lowered to a much more manageable 86 degrees. And the energy needed to pump the water is far less than what would be needed to cool the room equivalently with air conditioning.
From Harvard University:
An artificial vasculature for adaptive thermal control of windows
Windows are a major source of energy inefficiency in buildings. In addition, heating by thermal radiation reduces the efficiency of photovoltaic panels. To help reduce heating by solar absorption in both of these cases, we developed a thin, transparent, bio-inspired, convective cooling layer for building windows and solar panels that contains microvasculature with millimeter-scale, fluid-filled channels. The thin cooling layer is composed of optically clear silicone rubber with microchannels fabricated using microfluidic engineering principles. Infrared imaging was used to measure cooling rates as a function of flow rate and water temperature. In these experiments, flowing room temperature water at 2 mL/min reduced the average temperature of a model 10×10 cm2 window by approximately 7–9 °C. An analytic steady-state heat transfer model was developed to augment the experiments and make more general estimates as functions of window size, channel geometry, flow rate, and water temperature. Thin cooling layers may be added to one or more panes in multi-pane windows or as thin film non-structural central layers. Lastly, the color, optical transparency and aesthetics of the windows could be modulated by flowing different fluids that differ in their scattering or absorption properties.