Author: Aditi Chandrasekar
For the 1.7-odd billion people worldwide who still don’t have a reliable electricity connection, solar power is proving to be a potential saviour in terms of clean and sufficiently effective power, at least when the sun is shining. Of course, the technology to store excess solar power during the dark hours is improving. However, if there is an opportunity to harness electricity from the night sky, it could be a major breakthrough in the world of clean energy. Good news is, researchers at Stanford and UCLA have done just that. It is not ready to be deployed and used everywhere just yet, but this stunning development could play an important role in the energy demands of the future. The technology employed by itself is not novel or new; the principles behind it were discovered almost 200 years ago. The way it works is simple-the device, a thermoelectric generator, uses temperature differences between two metal plates to generate electricity through the ‘Seebeck effect’. Basically, the greater the temperature difference, the greater the power generated. This technology is already in use to convert waste heat from sources such as industrial machinery and car engines and this new research simply applies the same technique to capture the temperature difference between the outside air and a surface facing the sky. The top plate of the device faces the cold air of the open night sky, while the bottom plate faces the ground and is kept enclosed in warmer air. So, the two plates sit on top of each other. We know that heat in general always radiates to cooler environments. The cooler the surroundings, the faster the heat is radiated. Following this principle, the open night sky is cooler than the enclosed air surrounding the bottom plate, so the top plate loses heat faster than the bottom plate. This generates a temperature difference between the two plates. In the study conducted by the researches, this temperature turned out to be around 4 to 5 degrees celsius.
At different temperatures, heat will also start to travel from the hotter bottom plate to the cooler top plate and the device harnesses this flow of heat to generate electricity. But the glaring flaw in this is that at such a small temperature difference, the power generated is very limited-The researchers’ device produced 25 milliwatts per meter square-just enough to power a small LED reading light whereas a solar panel of the same size would be enough to sustain three 32″ LED TVs. Another possible flaw is its performance being affected by the climate-The device will perform better in dry climates than it does in wet climates because in wetter climates, any moisture in the air condenses on the downward-facing bottom plate, cooling it and reducing the temperature difference between the plates. Still, these don’t take away from the fact that this is a breakthrough technology. With enough research and development, it could be a massive boon to the energy crisis.