Crescent Dunes, a utility-scale solar power plant in the Nevada desert

http://time.com/4291347/crescent-dunes-solar-power-plant/?xid=time_socialflow_twitter

by prostoalex • 10 years ago

44 37 10 years ago

rgbrenner3• 10 years ago

"All night" isn't quite true. It has 10 hours of storage. And if you want full capacity, you have to start tapping into that in the evening.

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.

https://en.wikipedia.org/wiki/Crescent_Dunes_Solar_Energy_Pr...

honkhonkpants• 10 years ago

Doesn't "hours of storage" necessarily imply a rate of discharge? If you don't take any steam off it, doesn't it last more than 10 hours? It seems like they should just state the storage in terms of extractable energy stored.

And why sodium? It does not have a spectacular specific heat. Is it just convenient due to its high boiling point?

foota• 10 years ago

I believe it's because of the large temperature range between solid and gaseous phases, there is a ~800 degrees Kelvin difference between the boiling and melting points, which at a specific molar heat of 29 J/mol/K is greater than the energy to heat water to boiling for a ~100 degree difference at ~56 J/mol/K

rgbrenner3• 10 years ago

Yes.. they do state the storage in terms of energy. When plants state hours, it's at full capacity. So 110MW capacity x 10 = 1.1 GWH of storage. Of course it will operate longer if you use less than full capacity.

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.

dang• 10 years ago

"All night" isn't quite true.

Ok, we've replaced that title with representative language from the article.

taneq6• 10 years ago

Expensive indeed. I wonder how concentrated solar thermal compares with a simple photovoltaic plant these days? Given the precipitous drop in price for PV panels, even if solar thermal is currently cheaper, how much longer until it's just not competitive?

rgbrenner3• 10 years ago

PV is down to around 5 cents/kwh. I seem to remember a new plant recently that was 2-3 cents, but can't find it.

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.

london8882• 10 years ago

I think there's one being built in Israel too?

tomp• 10 years ago

This is really two things in one - a solar plant, and an energy storage system. Couldn't we decouple them? I.e. when electricity is cheap (Germany during the day can dip to zero), heat up the salt, and discharge it at night (actually, in the evening, when electricity is most expensive).

Also, I wonder how it compares to big batteries?

jws• 10 years ago

This is not a photoelectric plant. It is a sunlight concentrator to heat salt which stores energy which is eventually used to drive a steam turbine and turn a generator. All one thing.

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.

ams61102• 10 years ago

But if electricity is free during the day (I guess because of oversupply from wind and/or solar?) who cares about a 50% loss?

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.

markokrajnc• 10 years ago

In Spain already since May 2011: https://en.wikipedia.org/wiki/Gemasolar_Thermosolar_Plant

neolefty2• 10 years ago

No doubt they learned a lot from Gemasolar. The article describes Crescent Dunes as the first "utility scale" plant. The wikipedia page is a bit more quantitative, listing its capacity at 125 MW, vs Gemasolar's 20MW:

https://en.wikipedia.org/wiki/Crescent_Dunes_Solar_Energy_Pr...

MawNicker• 10 years ago

I'm sure they researched this but square panels seem suboptimal. I wonder if manufacturing made that determination. It seems like circular or hexagonal panels would better utilize the space. That or just grid aligned square panels. Maybe the space efficiency doesn't matter that much? Each configuration captures the entirety of indirect sunlight. The little bit extra you'd get from direct sunlight is likely insignificant compared to overall performance.

pdonis• 10 years ago

I don't think the panels are the limiting factor. Remember this isn't a photoelectric plant; the sunlight isn't being converted directly into electricity. All the panels are doing is reflecting sunlight to the central tower, where it heats up molten salt. The limiting factor for power generation is probably the heat capacity of the salt, not the amount of sunlight the panels can reflect.

Also, the panels don't look like flat squares to me; they look curved, so that they concentrate the sunlight they reflect.

Qwertious• 10 years ago

Circular panels would be a terrible idea, circles can't tessellate.

taneq6• 10 years ago

I don't think space efficiency is much of a consideration. These things tend to be built out in the desert where all you've got is space.

mkj• 10 years ago

To manufacture circles you'd probably be making squares then cutting off ~1/4 of the area and throwing it away.

london8882• 10 years ago

If transmitting power was more efficient we could just have solar in the lit time zones powering those in the dark.

neolefty2• 10 years ago

Exactly. With our current techniques -- high-voltage or superconducting lines -- as I understand it, it's more expensive to transmit than to generate "locally" (within a few hundred miles?). I'd be curious to see the tradeoff (1) researched better and (2) visualized quantitatively.

niftich2• 10 years ago

Sorry I don't have exact numbers for you, but there do exist some very long HVDC lines [1]. The longest as of writing is in Brazil at 2385 km. There is a fairly long one in the US at 1360 km between the Columbia River Gorge and the Los Angeles basin [2].

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.

[1] http://www.power-technology.com/features/featurethe-worlds-l...

[2] http://new.abb.com/systems/hvdc/references/pacific-intertie

ams61102• 10 years ago

That's not the only problem. You'd have to get the cooperation of many different countries who don't necessarily like each other. The political obstacles would be greater than the technical.

aaron695• 10 years ago

http://www.sciencealert.com/the-benefits-of-an-intercontinen...

RangerScience• 10 years ago

I drove by this plant to/from Further Future. The concentration of light around the central towers was so intense, it was visible - a light, glowing cloud (clearly in the "shape" of the reflected light) surrounding the central tower.

ChuckMcM• 10 years ago

Its great these things are coming online, they have issues when the mirrors get out of alignment. From lighting the lower parts of the tower on fire [1] to blinding pilots flying nearby [2].

[1] http://www.latimes.com/local/lanow/la-me-ln-solar-plant-fire...

[2] http://www.geek.com/news/worlds-largest-solar-power-plant-is...

jdeibele• 10 years ago

http://www.wired.com/2016/05/huge-solar-plant-caught-fire-th... has a decent summary of the problems with this type of solar.

I was surprised that the Ivanpah fire wasn't mentioned in the Time article but then it seemed pretty rah-rah.

bane• 10 years ago

I've started to become more and more convinced that the longer term view of the power grid is that it may no longer supply an assumed base-load. Instead every electronic device will end up having some measure of chargeable battery backup along with the building/facility the device is in. Over a day the batteries will soak up power and charge and at night they'll power the devices.

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.

Crescent Dunes, a utility-scale solar power plant in the Nevada desert

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