Also what's cool about this plant, is that it doesn't use natural gas in the morning to heat up the molten salt (like other plants). The salt never cools completely during the lifetime of the plant.
Expensive though.. on a 25 year contract at 13.5 cents per kwh. That'll be renegotiated after the 25 years at a much lower rate. Utilities pay higher prices for new plants (gas, oil, etc) to pay off the cost of building it. After that, it drops to a more reasonable price.
And why sodium? It does not have a spectacular specific heat. Is it just convenient due to its high boiling point?
Molten salt is used because it's liquid at atmospheric pressure, is low-cost, its operating temperatures are compatible with the most efficient steam turbines, and it is non-flammable and nontoxic.
The only problem with PV is its variability. When there's cloud cover, in the evening, etc.. power drops. Which means you need some kind of storage to even it out and probably a gas plant for the evening/night time.
In comparison, CSP has a steady output, which lets them make adjustments easier.
I.e. solve the problem on the demand side rather than the supply side.
The hybrid approach you describe would require twice the surface area and probably wouldn't double the output.
I think I prefer the idea of having large plants like these, with 'night'-time capabilities and a relatively steady output. That sounds like it would work pretty well in combination with decentralized roof top solar + smallish home batteries.
Of course, there's nothing wrong with the photovoltaic part being distributed in the form of rooftop solar, which is what's already increaslingly happening. Home storage batteries for load leveling are picking up nicely too, which is good because they're going to become mandatory within the next decade if we want metropolitan power grids to survive tens of megawatts of sometimes-rapidly-fluctuating solar power being dumped into them.
And we didn't even start playing with Sodium as a replacement for Lithium in those batteries.
Batteries have two things going for improvements in the batteries themselves and more energy efficient homes and appliances. PC won't replace utilities in densely inhabited regions, but batteries may help evening out variable sources.
Hybrid just means that it uses both approaches. I'm suggesting a solar thermal plant which is generally lightly loaded or unloaded during the day, storing the heat in a large reservoir while a neighboring PV plant much more cheaply covers demand. Then when the PV plant can't generate due to cloud cover or night time, the thermal plant steps up and uses the stored heat to generate power.
It's no different in principle to a hybrid car where a battery electric drive system cheaply covers as much driving as it can, and an internal combustion engine kicks in when required.
This article  analyzes some of the merits of this approach.
 (Partial paywall) http://social.csptoday.com/technology/integration-csp-and-pv...
Ok, we've replaced that title with representative language from the article.
Also, I wonder how it compares to big batteries?
You could use molten salt to store electricity on its own, but I think the efficiency would make it undesirable. A steam turbine is something like 50% efficient and is probably the least efficient part of the system, so it just gets worse from there. For comparison, lead acid batteries are above 70% efficient.
I wonder if using the heat directly e.g. with a Stirling engine/generator would be any more efficient?
Lead acid batteries are an environmental nightmare compared to molten salt.
Current thinking about power grids is that power generation is cheaper at night because people are using it less. But in a solar powered system, power generation during the day is essentially free, it's the capture devices (and storage devices) that cost anything.
This notion helps the power companies share and distribute the storage costs while making the direct users of the power responsible for sizing their storage costs.
Also, the panels don't look like flat squares to me; they look curved, so that they concentrate the sunlight they reflect.
I was surprised that the Ivanpah fire wasn't mentioned in the Time article but then it seemed pretty rah-rah.
But given that the solar terminator moves at about cos(latitude) * 1668 km / h (so slower towards the poles), even at a generous mid-Europe latitude of 45° N it'd be moving at 1180 km / h, giving you only a 2-hour window to make use of such a scheme with the HDVC lengths we have now. But hours before sunset, you're probably not at peak solar production anyway.