As renewable energy penetration increases, energy storage is becoming urgently needed for several purposes, including frequency control, peak shifting, and relieving grid congestion. While battery research often focuses on cell...
Flare frequency distributions represent a key approach to addressing one of the largest problems in solar and stellar physics: determining the mechanism that counterintuitively heats coronae to temperatures that are orders of magnitude hotter than the corresponding photospheres. It is widely accepted that the magnetic field is responsible for the heating, but there are two competing mechanisms that could explain it: nanoflares or Alfvén waves. To date, neither can be directly observed. Nanoflares are, by definition, extremely small, but their aggregate energy release could represent a substantial heating mechanism, presuming they are sufficiently abundant. One way to test this presumption is via the flare frequency distribution, which describes how often flares of various energies occur. If the slope of the power law fitting the flare frequency distribution is above a critical threshold, α = 2 as established in prior literature, then there should be a sufficient abundance of nanoflares to explain coronal heating. We performed >600 case studies of solar flares, made possible by an unprecedented number of data analysts via three semesters of an undergraduate physics laboratory course. This allowed us to include two crucial, but nontrivial, analysis methods: preflare baseline subtraction and computation of the flare energy, which requires determining flare start and stop times. We aggregated the results of these analyses into a statistical study to determine that α = 1.63 ± 0.03. This is below the critical threshold, suggesting that Alfvén waves are an important driver of coronal heating.
Deep decarbonization of the power grid is only possible with mass-scale energy storage to overcome the spatiotemporal mismatch between supply from renewables and demand. Aqueous flow batteries fully decouple power and energy elements and can thus easily be scaled, a prerequisite for cheap long-duration energy storage, but low energy density is generally considered a key limitation of the technology. To date, the role of this metric for grid-scale installations has not been quantified, a crucial step for guiding further development of this potential trillion-dollar market. Here, we analyze the footprint of forty-four MWh-scale battery energy storage systems via satellite imagery and calculate their energy capacity per land area in kWh m−2, demonstrating that energy density is not critical for such installations and that the importance of this metric for grid-scale batteries is heavily overstated in academia. We suggest that a unique advantage of aqueous flow batteries, due to their intrinsic safety and vertical scalability, is their ability to provide reliable power in space-restricted sites, and we show that even with current chemistries and modest assumptions about storage tank sizes and footprints, areal energy densities five times as high as with the average lithium-ion based system can be achieved.
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