Finland has inaugurated an industrial-scale sand battery this week in the southern town of Pornainen, where it'll take over heating duties from an old woodchip power plant for the municipality. It's set to reduce carbon emissions from the local heating network by as much as 70%, and is the largest…
You can’t really compare those efficiencies with each other, between different technologies.
With fuel, you’re talking about how much energy per kg.
With wind, you’re talking about how much energy per m/s wind.
With solar, you’re talking about how much energy over the whole solar spectrum that gets through the atmosphere. However, a single junction p-n diode made of silicon is only meant to work at a specific wavelength, and will only get energy from around this wavelength, and as such could only ever get a maximum theoretical efficiency of ~36% of the total solar spectrum of light wavelengths. In the lab I think some have achieved ~33%.
You can get higher efficiency solar cells, but you have to use novel materials and have multiple layers of different p-n junctions. Short wavelengths first, these materials are transparent to longer wavelengths, which are absorbed by lower layers. With a theoretical infinitely layered solar cell you could achieve ~88% of the solar spectrum energy. In reality it’s really hard to make a semiconductor diodes that fit certain wavelengths, leaving gaps in the spectrum even with multiple diode layers.
~30% for solar cells sounds ridiculously low compared to like, maybe, 70% for fuels. But it’s a completely different measurement. Grid scale battery systems are mayb 98-99% - but that’s just electrical energy in and electrical energy out over a short time.
There is no common denominator, but the solar energy is free.