Use of Polar Heliostats to Improve Levels of Natural Lighting inside Buildings with Little Access to Sunlight

The growing need to increase environmental and energy sustainability in buildings (housing, offices, warehouses, etc.) requires the use of solar radiation as a renewable source of energy that can help to lower carbon footprint, making buildings more efficient and thereby contributing to a more sustainable planet, while enhancing the health and wellbeing of its occupants. One of the technologies deployed in the use of solar energy in buildings is heliostats. In this context, this paper presents an analysis of the performance of a heliostat illuminator to improve illumination in a classroom at the Campus of Rabanales of the University of Cordoba (Spain). A design of a system in charge of monitoring and measuring daylighting variables using Arduino hardware technology and free software is shown. This equipment develops the communications, programming and collection of lighting data. In parallel, installation of an artificial lighting system complementary to the natural lighting system is implemented. Finally, an analysis of the impact of the proposed solution on the improvement of energy efficiency is presented. Specifically, it is estimated that up to 64% of savings in artificial lighting can be achieved in spaces with heliostatic illuminators compared to those without them.

Hierarchical-Morphology Metal/Polymer Heterostructure for Scalable Multimodal Thermal Management

The cooling and heating energy consumption of buildings poses a serious threat to the energy supply and increases greenhouse gas emissions, thus adversely impacting global warming and the long-term climate change trends. Here, inspired by the structure of the louver, this work demonstrates a multimodal device that integrates radiative cooling, natural lighting, and solar heating to deal with the grand challenge of building energy consumption. The blades integrate a selective radiative cooling material with a solar heating material. The selective radiative cooling material (solar reflectance ∼97%, selective emittance ∼0.82 in the 8-13 μm waveband) combines a solar reflective melt-blown polypropylene film and a solar transparent mid-infrared emitter polyethylene/silicon dioxide film. In addition, the heating material (solar absorptance ∼91%, thermal emittance ∼0.04) is zinc (Zn) film deposited with copper (Cu) nanoparticles, based on the Cu-Zn galvanic-displacement reaction. Hence, by rotating the blades, the conversion of radiative cooling, solar heating, and natural lighting functions can be realized. In the daytime, the multimodal device displays a subambient temperature of 4 °C, a superambient temperature of 2 °C, and a superambient temperature of 5 °C for the cooling mode, transmitting mode, and solar heating mode, respectively. On the basis of the energy-savings simulation, integrating these modes and dynamic converting these modes in the corresponding climate could save ∼746 GJ in the contiguous United States for one year (38% of the baseline energy consumption), which is equivalent to ∼147 tons of carbon dioxide emission reduction. Because of its excellent multimodal thermal management performance, this multimodal device will push forward the transformative change of building thermal management toward decarbonization and sustainability and being more green.