Extracting from the winter / summer cycle, the day / night cycle, and the consistent deep ground / surface air temp differential.
Granted day / night might not have enough variation to take advantage of in a lot of places - but surely some cool tech has come out of desert areas right?
For a given kwh of storage that is round-tripped daily, a 1% loss of efficiency loses 3.65kwh per year. For a kWh of storage that is round-tripped once per year, you only lose 0.01kwh. At 70% conversion efficiency the yearly storage still loses only 1/10 the energy as a daily system at 99%.