EDIT: Submarine power transportation is indeed on the list

Not transoceanic, but there are two projects currently proposed that will -- when constructed -- break the current record for the "longest undersea power transmission cable" (a record currently held by the North Sea Link at 720 km, or 450 miles.)

One of these projects is the Xlinks Morocco-UK Power Project which aims to lay 3,800 km (2,400 miles) of cable and sell Morocco's solar power to England.

There is, as of yet, not enough cable in the world to even begin this project. The company proposing the project is building factories to produce this cable.

The other is the Australia-Asia Power Link, which aims to provide Australian solar power to Singapore using a 4,500 km (2,800 miles) undersea cable.

Where the Xlinks project ran into a "not enough cable in the world" problem, Sun Cable's AAPL has apparently been running into a "not enough money in the world" problem, as it has repeatedly gotten into trouble with its investors.

EDIT: But also, storage is scaling up

@[email protected] provided a fantastic link to a lot of energy storage mediums that are already in use in various grids across the world. These include (and the link the professor provided gives an excellent short summary on each)

• Pumped hydroelectric
• Compressed Air Energy Storage (CAES)
• Flywheels
• Supercapacitors
• And just plain batteries

Also, this wasn't in the Gumby's answer, but Finland's Vatajankoski power plant uses a hot sand battery during its high-demand, low-production hours.

Hydrogen is projected to grow

@[email protected] noted that hydrogen has advantages no other energy storage medium possesses: duration of storage and ease of piping/shipping. This is probably why numerous governments are investing in hydrogen production, and why Wood Mackenzie projects what looks like a 200-fold increase in production by the year 2050. (It's a graph. I'm looking at a graph, so I am only estimating.)