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Alternatively the heat of compression can be thermally stored before entering the cavern and used for adiabatic expansion extracting heat from the thermal storage system.

You can do these searches for yourself, you know. But look here and here for a start.

I'm sorry, but solar panels do dramatically reduce in power on cloudy days. The absolutely do not "operate surprisingly close to the same capacity as on a non-cloudy day." Here's what a daily generation profile looks like on a day with scattered clouds. Here you can see a mixture of cloudy, sunny, and partly cloudy days.

Your statement was simply wrong.

Literally nothing you wrote in your post was correct. UV is a nearly irrelevant source of energy at the surface. Clouds do provide some UV blocking, and they're nearly opaque to IR, not just "a bit". Normal solar panels can't run on IR, and are either highly inefficient with or can't use UV at all. And no, solar panels do not "operate surprisingly close to the same capacity as on a non-cloudy day"

"Wind and solar are viable, they just don't lessen the needed amount of fossil fuel capacity needed"

I call bullshit. We could put in HVDC transmission lines (Max distance around 3500km or 83% of the width of the contiguous United States) running from east to west and north to south. Those lines are each longer than a weather system is big, so you ship wind power from windy areas to calm areas that need power, and from sunny daylight areas to dark or cloudy areas that need power.

For the rest of the balancing needed, we could, for example, put in one gigantic hydrogen electrolysis and storage and fuel cell generator facility in the geographic center of the country. It would only be 30% round-trip efficient (energy out compared to energy in) however then you just need to install three times the wind and solar you would otherwise need, and Bob's your Uncle. If you don't want to do that, use a bunch of large compressed air storage facilities http://energystorage.org/advan... running at 70% round-trip energy efficient.

And if you still don't want to do very large storage for some reason, then tap into the enormous geothermal energy rersources under the US. Way more than enough energy for the country's needs there. No GHG emissions.

How about a combination of all these strategies. The technology is there. The price is becoming reasonable, and a small and not too punitive carbon tax would make it economical to build all this new infrastructure fast. We just need to get off our asses and do it.

There are plenty of less expensive, lower risk options for energy storage. e.g. flywheels, molten salt, water reservoirs, etc.

You can create an energy storage system with a pumped-storage hydroelectric systems pumped-storage hydroelectric systems . In essence, you use wind or solar to pump the water up, and then you use a hydroelectric generation system to produce power even during periods when there is no sun or wind. There are other systems, like pumped heat electrical systems as well.

I don't know where you went to school, but when I was in school they taught about this fancy amazing thing called "potential energy". There are other ways to store energy other than big-ass batteries.

And, of course, some forms of renewables are fairly constant. In some areas, geothermal is the answer.

Also pumped hydro energy storage is an existing utility scale option for intermitent renewables. With limited transmission capacity such as between the pacific northwest's hydro dams and California it is a great way to store energy from off peak transmission for use during peak usage.

This is true, but even without renewables energy storage is a good tool to have available to the grid. Batteries and inverters are capable of sourcing and sinking power, as well as ramping up and down fast, making them good candidates for frequency regulation and other ancillary services. For example, by spacing storage systems around, you can also help avoid congestion on large transmission lines.

They do that already with pumped-storage.

Pumped storage has an RTE (round-trip-efficiency) of about 80%. Modern li-ion batteries are over 90%. Pumped storage requires very specific geography (two reservoirs separated by a hill). Batteries will work anywhere.

There are also some liquid batteries.

The most common "flow" batteries are based on vanadium redox, and have an RTE of 65-75%.

Li-ion is just too expensive and maintenance-intensive to use grid scale.

Well, the point of this announcement is that Li-ion is getting cheaper. Li-ion grid storage still won't make sense in the middle of America, where power is cheap, and grids are wide. But it make make sense in places like Hawaii ($0.40 / kw-hr), where grid stability is already a problem.

The round trip efficiency of hydrogen storage is only 30% to 50%. That means that you would have to put in two to three times the energy that you get out. In the base of that electricity stored in hydrogen will cost 2 to 3 times as much a usual.
Secondly hydrogen is difficult to store in large quantities. It leaks through solid steel and unless cryogenicly stored has a very low energy density.