CA's First Molten Salt Energy Plant Approved

An anonymous reader writes "This year we've seen molten salt power plants start to pick up steam around the world, and now the technology is heating up stateside — California just approved its first molten salt energy plant. Designed by SolarReserve, the plant uses heliostats to focus thermal energy on a power tower filled with salt, which is able to reach very high temperatures (over 1000 degrees Fahrenheit) and can hold heat for an extraordinary length of time. Heat from this reserve of molten salt can then be pumped through a steam generator to provide on-demand energy long after the sun has set."

Comments

Heat retention for how long ?

[Taibhsear]

Does anyone know exactly how long the reservoir tanks will keep the molten salt at a high enough temp to be useful? It says it can run for 24 hours but should an abnormally long string of cloudy days occur would this inhibit its usefulness? I realize it's California so it should be fairly sunny year round but I'm not familiar with the area it's being built at. Looked up the salt as well. (Had a hard time thinking it would be sodium chloride...) It's a mixture of sodium and potassium nitrate. I was a bit worried as nitrates tend to be violently reactive/explosive but this would only be with reducing agents. (so it should be relatively fairly safe if there was a leak.) However when potassium nitrate is heated above 560C (as it would in this plant) it turns to potassium nitrite and gives off oxygen. I'm curious if this would be an issue or if the sodium nitrate or something else in the mixture inhibits this. I imagine the oxygen would either stick in the solar collector part as a gas bubble or just be dissolved in the molten salt mixture. Anyone know? (My expertise is more in biochemistry than inorganic/industrial chemistry)

Re:Heat retention for how long ?

[corbettw]

It's being built in the Mojave Desert. Anything capable of causing sufficiently cloudy days for long enough to prevent solar collection is going to be a bigger problem by itself that not being able to pump out heat from the now-cooled salt. An eruption of the Yellowstone Caldera, comet impact, nuclear attack, something on that order is what we're talking about.

Re:Heat retention for how long ?

[Biogenesis]

I've been doing some research into renewable energy in an Australian context at the University of Newcastle. The most commonly thrown around figure is 1C/day of loss at operating temperatures.

In doing some simple simulations (using real world demand, wind farm output and direct solar irradiance data) I've found that 50GW of wind farms (peak, scaled by 50x from Australia's current ~1GW peak wind capacity) and ~42GW of concentrated solar thermal (roughly 53x53km square area, spread across Australia on 12 sites) with 24hrs of storage is able to supply all of Australia's current electricity demand. The thermal storage dropped to ~10% capacity at it's lowest point.

The simulation tried to closely model the Beyond Zero Emissions Zero Carbon Australia 2020 plan. Their modeling uses a different demand profile, one scaled to a proposed 2020 level after compensating for growth, electrification of cars etc.