As urban populations continue to increase, smart cities have become essential for improving the quality of life and urban services. In this sense, Internet of Things (IoT) devices, which collect and process data in real time, are essential. These devices consume very little power -between 1 µW and 1 mW- but need to operate continuously, often in remote or off-grid areas. Currently, batteries are their primary power source, which is not ideal; batteries have limited lifespans, can harm the environment, and require regular replacement or recharging. A fundamental question arises: Can we power IoT devices without batteries, anytime and anywhere?
Traditional renewable sources like solar, wind or tidal energy are not always available and they still depend on batteries for storage. This project introduces a disruptive, battery-free solution that works 24/7, independent of ambient conditions. The idea is to combine two cutting-edge technologies: radiative cooling, which uses the cold of outer space to passively lower temperature, and thermoelectric generators (TEGs), which turn temperature differences into electricity. The project aims to develop a self-powered system that integrates:
· A radiative cooler made of 3D polymer metamaterials that can reflect sunlight and emit heat efficiently -even during the day. Unlike conventional coolers that work mostly at night, COOLed’s approach uses specially designed polymer structures that don’t need mirrors or reflective coatings, making them more versatile and effective.
· A TEG based on 2D transition metal selenides. To solve the problem of improving the efficiency of thermoelectric materials, COOLed will explore 2D selenides, offering a high performance with abundant, non-toxic materials, and manufactured using scalable, low-cost methods.
Together, these elements will form a lightweight, scalable, and eco-friendly energy source that can deliver 1 W/m² -sufficient to power IoT devices in urban or remote environments.
This is a multidisciplinary, cutting-edge initiative in materials science and energy harvesting. It explores new 3D and 2D material platforms, opens up new possibilities in how we power devices, and supports the green transition. From reducing electricity use and heat waste to supporting European sustainability goals, COOLed could help reshape how cities function in a more energy-responsible future.
