Skyscrapers are full of glass, so some Spanish researchers have had an idea: let them serve as "solar panels"

Every 60 minutes, the Sun bathes the Earth with enough energy to cover the world’s consumption for an entire year. The data, remembered by the Polytechnic University of Madrid (UPM)it’s overwhelming. But there is a problem: harnessing all that energy in our cities hits a literal wall. Classic solar roofs are becoming too small for us in increasingly dense cities, and hanging rigid and heavy panels on the facades of buildings is not a realistic option.

To avoid this aesthetic and space blockage, the laboratories have found a pioneering solution: using new two-dimensional materials. These are microscopic layers that will allow the windows of any skyscraper to be converted into totally invisible solar panels.

With Spanish seal. The Silicon and New Concepts for Solar Cells (SyNC) research group of the Solar Energy Institute (IES) of the Polytechnic University of Madrid (UPM) has managed to manufacture micro-prototypes of ultra-thin and highly efficient solar cells.

The secret of this technology lies in the so-called two-dimensional photovoltaic materials. Imagine a sheet so thin that it is only a few atoms thick; For all practical purposes, it is so thin that physics considers it to lack a third dimension. Science knows this family of compounds with a complex name, transition metaldicalkogenides (TMDC), among which molybdenum disulfide (MoS2) and tungsten diselenide (WSe2) stand out. Their great rarity—and their greatest virtue—is that, despite being an almost invisible layer, they have an extraordinary capacity to absorb sunlight.

The actual scope. To understand this technology, researchers published a study in the scientific journal Nano Energy. In it, they simulated what would happen if the façade of a real skyscraper, the Torre Picasso in Madrid, were covered with semi-transparent windows made with these materials. The results estimate that between 16% and 23% of the building’s daily electricity consumption could be covered. If this technology is also combined with areas of opaque modules, the generation could exceed 30% of the energy needs of the skyscraper.

Natural light, real colors and savings on the bill Historically, the big “but” of solar windows has been the poor visual quality. Alternative technologies, such as organic or perovskite cells, often act as a filter that colors the light entering the room in unnatural reddish, yellow or brown tones.

As explained by UPM researchersthe structure of TMDC materials solves this root problem: they allow a very balanced absorption of visible light, which eliminates the problem of unwanted “coloring” of light. The result is lighting with a natural and warm tone, achieving a Color Rendering Index (CRI) greater than 90, a very high quality metric for work spaces.

In addition to generating electricity, in very sunny places like Spain, these glasses naturally block excessive glare. This means that the skyscraper not only produces its own energy, but also saves a lot of money by not having to turn on the air conditioning as much.

From the microscopic laboratory to the factory. Creating these ultra-thin solar cells is a work of very high precision. To manufacture the prototypes in the laboratory, the UPM team has used a technique called hot-pick-up. Using this method, they use a small transparent bubble to select, collect and deposit fragments of the materials, creating tailored stacks that combine the best properties of each one.

But the goal is not to stay in the laboratory. IES-UPM researchers are already working with new techniques to scale this process and cover large areas, such as entire windows. According to the scientists themselves“through spraying and deposition techniques of these solutions, manufacturing processes could be scaled, reducing costs and allowing the industrialization of this disruptive technology.”

The ace in the hole: catch the lost heat. The potential of these two-dimensional materials goes far beyond solar windows. Another investigation from the same team, published in the scientific journal ACS Applied Energy Materials, demonstrates that by modifying molybdenum disulfide (MoS2) with an element called niobium, the material acquires impressive thermoelectric properties.

More simply, this means that in the future, these materials could not only capture sunlight, but could also have applications in thermal sensors or in the recovery of energy from the heat wasted by machines or buildings themselves.

The new skin of the city. The lightness, flexibility and low manufacturing cost of these solar cells makes them one of the most promising options to achieve the desired “green cities”. Two-dimensional photovoltaic technology shows us that the ecological transition in dense urban environments no longer depends only on finding space on roofs to place large rigid panels. The real paradigm shift consists of transforming the very “skin” of buildings – their windows, their walls, their facades – into active sources of clean energy, ensuring that any surface can be an ally against climate change.

Image | Photo by Arthur Mazi on Unsplash 

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Skyscrapers are full of glass, so some Spanish researchers have had an idea: let them serve as “solar panels”

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Xataka

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Alba Otero

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