We will confess that the authors of the Applied Physics Letters article “Experimental Demonstration of Energy Harvesting from the Sky using the Negative Illumination Effect of a Semiconductor Photodiode” never used the acronym DAD or the phrase “dark absorbing diode.” But we thought it was too good to pass up. The research work uses a type of diode to generate small amounts of power from darkness. Admittedly, the amount of power is small, but it is still an important result and could result in — another coined phrase — negative solar cells providing energy by taking advantage of the temperature differential between the cell and the night sky.
In theory — and with no atmosphere — the technique could only result in about 4 watts per square meter. Not only is this low compared to a solar panel’s 100 to 200 watts per square meter, but it is also far from the prototype’s 64 nanowatts per square meter. Clearly, this technology has a ways to go to become practical.