As the post-pandemic globe progressively recovers with ever-increasing needs for electricity, weather-dependent environmental energy harvesting of solar heat, wind energy, and rain energy towards carbon sustainability and net zero is essential.
On the left is schematic drawing of non-planar dielectrics for modulated solar heat harvesting and raindrop energy conversion. On the right is comparison of normalized power output of non-planar device versus planar configuration. Image Credit: Science China
In general, seasonal and climate-dependent, ubiquitous ambient energy sources manifest as sunny/cloudy/rainy weather and diurnal cycles. Examples of these sources include solar illuminations, wind fluctuations, ground heat, humidity variations, and raindrops.
Recently, the output power density for sole solar heat harvesting utilizing pyroelectrics was reached, ranging from 10 to 1000 μW m–2. However, due to synchronous and uniform thermal field propagation across the entire device, these classic planar devices homogeneously collect solar heat, resulting in negligible temporal temperature variation and polarization shift.
For raindrop-based triboelectricity generation, however, this flat dielectric is not practical since triboelectrification and electrostatic induction rely on the temporal variation of the water droplet sliding area during the liquid-solid contact/separation process.
Other energy harvesting options that use curved or non-planar bulk dielectrics to achieve inhomogeneous local heat and electrostatic field propagation towards enhanced pyroelectricity and triboelectric output must be developed immediately for weather-adaptive energy recovery to get around these obstacles.
Yi Zhou and lab directors Prof. Jiaqing He and Prof. Ghim Wei Ho delve into the intriguing topic of how weather-adaptive environmental energy harvesting is facilitated by non-flat or non-planar dielectrics with high degrees of structural freedom, specifically on sunny, cloudy, night, and rainy days, in a recent research article that was published in the Beijing-based National Science Review.
By utilizing non-planar dielectrics to overcome the independence of conventional environmental heat and raindrop energy harvesters, the team presents a novel paradigm to “kill two birds with one stone.”
It was discovered that non-planar multi-layer dielectrics increase non-uniform spatial polarization and pyroelectricity by confining local solar heat propagation along the in-plane direction. Concurrently, the non-planar arrangement with a curved architecture and textured morphology encourages the spreading and separation of water droplets, increasing the total induced electrostatic charges in the direction of increased triboelectricity.
As a result, the non-planar generator is made of widely used plastics (Teflon and fluoropolymer). It allows for cost-effective solar heat and raindrop energy harvesting with an output power increment of 174.3% and 65.4%, respectively, according to lab measurements, without consuming additional solar heat and raindrop energies or modifying dielectric properties.
The researchers tested outdoor in-situ methods for all-weather energy collecting on sunny, overcast, night, and rainy days in addition to scalable manufacturing approaches.
These results not only pave a new way for environmental heat/rain recovery but also for inspiration in other high-entropy energy upcycling.
Yi Zhou, Research Fellow, Department of Electrical and Computer Engineering, National University of Singapore
Journal Reference:
Zhou, Y., et al. (2023) Non-planar dielectrics derived thermal and electrostatic field inhomogeneity for boosted weather-adaptive energy harvesting. National Science Review. doi:10.1093/nsr/nwad186