https://www.sciencedirect.com/science/article/abs/pii/S0378775321010892 https://www.sciencedirect.com/science/article/abs/pii/S03787... I think the other aspec

https://www.sciencedirect.com/science/article/abs/pii/S0378775321010892 https://www.sciencedirect.com/science/article/abs/pii/S03787... I think the other aspect of “always on” is that the operator isn’t going to pick up the sensor years down the line. They’re just going to leave it dead and buried, especially if the sensors have to live inside the earth There’s ongoing work on harvesting electricity out of soil