Switchable windows provide intriguing opportunities for addressing the challenges of modern building skins. In particular, indoor comfort and the control of radiative heat transfer into and out of the building require adaptive and tunable solutions for shading and emissivity. Here, a switchable, ultrathin suspended particle device (SPD) for large‐area integration with smart facades is presented. The system is based on a fluidic window, manufactured at low cost from a laminate of structured, rolled glass and a thin cover with high surface strength. Loading the circulating fluid with magnetic nanoparticles enables active shading and solar‐thermal energy harvesting, whereby the loading state and, hence, the optical properties of the liquid can be controlled through remote switching in a particle collector‐suspender device. In the fully shaded state, a typical harvesting efficiency of 45% of the incoming solar power is obtained. For an average solar irradiance of 1000 W m−2 during 800 h a−1, this corresponds to a solar thermal harvesting capacity in the range of 360 kWh a−1 m−2. In comparison to alternative SPD concepts, this enables high flexibility and compatibility with established production lines. In addition, there is no need for further electrical contact, transparent conductive layers, or electrolytes.

improving the energy efficiency of a building is to minimize the heat exchange at the building interface. This is presently achieved through improvements on the building envelope, and facilitated through various material innovations, e.g., efficient thermal insulation materials, [11][12][13] emission-control coatings and surface layers, [14][15][16] or passive cooling systems which target enhancing the albedo of the urban environment, implemented either on the roof [17][18][19][20] or in façades. [21][22][23] Furthermore, active systems which adapt to environmental conditions are also studied, for example, chromogenics, [24][25][26][27][28][29][30] suspended particle devices, [29,31,32] liquid crystal devices, [29,31,[33][34][35] or evaporative or transpiration coolers. [36] Besides building envelopes, indoor cooling and air-conditioning systems represent a second area of major interest. This involves primarily the compensation of thermal load (originating from solar input as well as from electronic appliances, lighting, or human activity). Currently, the evacuation of latent and sensible heat is achieved using air-based cooling systems connected to chillers which operate with a fluid temperature of around 7-12 °C [37] and reach a seasonal performance factor of around 4. However, those systems are often conceived as being uncomfortable because of strong chill, convection, vertical gradients in air temperature, and noise. [38,39] Hydronic cooling systems for integration with building components (e.g., ceilings, walls, floors) are hence proposed as serious alternatives, enabling improvements on indoor comfort at significantly reduced energy consumption. [40][41][42][43] In this context, we now present a new type of hydronic system for sustainable cooling of indoor spaces and individual zones. Making use of visually transparent, large-area fluidic panels for wall, ceiling, and window integration, [44][45][46] we avoid negative effects such as draught or noise emitted by conventional air-conditioning systems which circulate cold and dry air. To facilitate significant reductions on energy consumption, the present system operates at very low flow rates and strongly reduced temperature gradients.As depicted in Figure 1, the device relies on cold water circulating through densely packed channels within a glassglass laminate such as recently reported for large-area integration with adaptive facades [44,47] or flat-panel algae reactors. [48] Adapted cooling performance is achieved by controlling the temperature and the flow rate of the circulating fluid, with More than 20% of the global energy demands are caused by heating, ventilating, and air conditioning in buildings. In particular during summer seasons and in warm climates, cooling loads are mostly neutralized by conventional air-conditioning systems. Due to often very low primary temperature, these require high energy input, cause significant noise, uncomfortably cool draughts, and vertical air temperature gradients. Here, an energy efficient planar cooling device for...

For decades, various technologies have been developed aiming to enhance the energy efficiency of buildings. As a recent example, fluidic windows have been reported which literally enable to wrap buildings into a liquid layer and to transform the building envelope into a thermally active system for energy harvesting, distribution and storage. Elaborating on this concept, we now consider the performance of insulation glass units (IGU) which implement glass-glass capillary panels for liquid circulation. Such devices contain a scalable heat pump that can reversely be operated in active cooling or heating modes. By bridging the insulation panel inside the window, also passive cooling functionality is achieved. Long-term computational performance analysis shows that adequate thermal comfort can be ensured with different window-to-floor size ratios, and for different internal heat gain, for example, caused by differences in room occupation. For a size ratio of 0.4, we demonstrate a competitive seasonal performance factor, i.e., ∼6.5 for heating and ∼10.9 for cooling. On-device photovoltaic power can cover more than four fifths or the annual electricity consumption of all auxiliary components. For the size ratio of 0.4 in a highly-occupied office room, the device specific primary energy consumption ensuring year-over thermal comfort is as low as ∼2.9 kWh/(m 2 a).