Paul the most cost efficient form of energy storage is molten salt storage.
Among renewable energy soruces, only CSP is compsatable with Molten Salt energy storage. CPS as an energy source is limited by levelized cost, daytime clouds, and winter limitations on sunlight. CPS is not cost competitive with nuclear power, and never will be, and CSP with storage is even less competative.
It is possible to build Nuclear Power Plants that can take advantage of the potential benefits of Molten Salt Storage without the high costs or sunlight variability of CSP.
The Small High Temperature Advanced reactor appears particularly attractive for short term development because it is capable of producing large amounts of Molten Salts, at temperatures as high as 750 degrees C, and from small nuclear unites that cost less to build than small light water reactor units. Such systems can be used to produce industrial process heat, can be located any where in the world, can be air cooled thus fo not require to coolant water, are extremely safe, and can be designed to produce only small amounts of short lived nuclear waste. They will cost less to build than conventional reactors of equivalent output. With molten salt storage, SmAHTRs can provide peek serve as peak electricity at a low cost.
Clearly then renewable advocates who are considering the combination of renewable energy and energy storage are barking up the wrong tree. Nuclear power systems offer superior reliability at lower levelized costs and are compatable with low cost energy storage systems that lack the geographic limitations of renewable systems with storage.