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

Silicon Production

[UdoKeir]

Slightly off-topic (or on-topic considering the bigger picture). Can this method of heat concentration be used in the refinement of silicon. My understanding is that silicon production is expensive because of the energy needed to generate heat for the process.

http://en.wikipedia.org/wiki/Silicon#Production

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.

Re:home use?

[benjamindees]

Efficiency directly affects cost.

If you're trying to argue that modifying some technology to make it more efficient will necessarily make it cost less per unit of energy, then that is patently false. I can make any thermoelectric device more efficient by making it out of diamonds and gold, but that won't make it cheaper. Any technology with a different efficiency is a different technology, full stop. If all we care about is cost/energy, there are lots of factors more important than efficiency to consider.

smaller turbines are less efficient

With CHP systems, turbine efficiency doesn't matter. You can heat your house or your hot tub with the 20% more waste heat that a small turbine generates. In fact, a small system can be more efficient as well as cheaper than a larger one by utilizing the 60% waste heat produced.

Smaller components can be built on assembly lines, using automated processes, instead of in a one-off fashion. This can make them less expensive and more reliable. Smaller components can be sourced from multiple producers, leveraging market forces to lower costs and increase quality. Smaller systems are also easier to finance, and can be more resistant to fraudulent investment schemes, legal barriers and market manipulation.

These are all more important factors to consider with renewable energy than mere efficiency. But cost is clearly the biggest factor. And it should be plainly obvious that the relationship between cost and efficiency is tenuous at best.