# 24 hour solar electric plant



## peakbagger (Oct 13, 2016)

http://www.powermag.com/crescent-du.../?hq_e=el&hq_m=3294726&hq_l=3&hq_v=e5802fd5a2

I am curious if they also have the problem with  "streamers" that Ivanpah has

http://www.csmonitor.com/Environmen...r-power-plant-scorches-birds-in-mid-air-video


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## Handsonautotech (Oct 13, 2016)

I made it to page two then had to do some work, does it mention how it stores the power ? Is it by storing the hot salts or by batteries?

Just got time to finish the atriclt, good one, It does store the hot salts to function at night, simple but genius. 

Reading between the lines it is also another example of a company getting rich off of tax dollars. They just got private funding to start two more plants in other countries. In my opinion they should be forced to use the financing to pay off the debt to the government. Also since their new plants are outside of the US they will not be generating any tax dollars either... So while we are footing the bill for the Nevada plant they will be raking in the funds from the new plants in other countries.


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## 7acres (Oct 13, 2016)

peakbagger said:


> http://www.powermag.com/crescent-du.../?hq_e=el&hq_m=3294726&hq_l=3&hq_v=e5802fd5a2
> 
> I am curious if they also have the problem with  "streamers" that Ivanpah has
> 
> http://www.csmonitor.com/Environmen...r-power-plant-scorches-birds-in-mid-air-video



I wanted to see the Ivanpah video to see a bird turn into a wisp of smoke in mid-air. What a disappointment.


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## iamlucky13 (Oct 14, 2016)

I'll bet they get plenty of streamers - it seems inherent to the technology. But they're selling higher value (schedulable) lower cost ($0.135 vs. $0.20 / kWh) electricity than Ivanpah (which has no storage and is having to burn natural gas to meet their power delivery commitments).

Crescent Dunes uses molten salt storage - enough to fill a small oil tanker. Nobody uses batteries on anything close to this scale (and Crescent Dunes is relatively small as far as power plants go).

Those shipping container batteries that some utilities are installing are really used for load balancing and frequency regulation, not storing a significant amount of power overnight. They're too expensive for large scale storage like Crescent Dunes is doing, and it would take several hundred, perhaps as many as 1000 of them to store as much energy as Crescent Dunes does.

The molten salt storage seems to add a premium of somewhere around $0.10/kWh (educated guess) compared to what the electricity would cost if generated live in an equivalent non-storage facility. A combination of their daytime live generation and tax credits enable the $0.135/kWh price they're contracted for.

The DOE estimates doing the same with lithium-ion batteries costs about $0.60/kWh, or with Vanadium flow batteries, about $0.45/kWh. Costs for an equivalent day/night mixed system of solar PV + batteries would be in the ballpark of half that overall (again, educated guess on my part, but peakbagger's article suggests similar on page 4).


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## woodgeek (Oct 17, 2016)

iamlucky13 said:


> The DOE estimates doing the same with lithium-ion batteries costs about $0.60/kWh, or with Vanadium flow batteries, about $0.45/kWh. Costs for an equivalent day/night mixed system of solar PV + batteries would be in the ballpark of half that overall (again, educated guess on my part, but peakbagger's article suggests similar on page 4).



I am not sure about your numbers.  If a conservative cost for large Li-ion batteries in 2016 is $300/kWh, and the batteries can do at least 1000 full equivalent cycles before they are so degraded as to be useless, then the storage cost is $300/1000 = $0.30/kWh.  While the rest of the facility cost is not included, it should be longer life and amortized. 

This is just half of your estimate from the DOE.  The cost of Li-in batteries was $600/kWh in 2011, so the $0.60 estimate might just be from that period?

Many claim that internal cell costs at many EV manufacturers are closer to $200/kWh, and I think that cycle counts for stationary applications can be >1000, so costs might already be <$0.20 per kWh today, and still falling.

The numbers I have seen on molten salt are ~$0.10.


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## peakbagger (Oct 17, 2016)

The power storage market is the "wild wild west" right now. Don't trust the claims that are in the press, many new firms and big firms all are scrambling to get installed base even if they cannot live up to their claims and are taking the work on at a loss. Its the standard growth curve on new technology, lots of firms see a high payoff so they scramble in to stake a claim and hope they can survive the inevitable shake out as one technology takes hold. It happened with PCs and is still happening with PV.

The molten salt storage concept is technically feasible I just wonder if it ever can survive without heavy upfront subsidy. My bet is on flow batteries, for utility storage. It uses industrial concepts (pumps and tanks) for the majority of the system. The actual cells are readily rebuildable. For those familiar with a plate and frame heat exchangers, that is effectively what the cell is roughly configured. Easier to deploy and integrate with the grid and quick to deploy. They also support distributed generation more effectively.

Banks of thousands of battery cells just don't make sense to me for utility scale. Recycling is going to be more difficult with individual cells as there is lot more packaging required per unit of energy stored than with flow cells.


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## woodgeek (Oct 17, 2016)

Totally agree.  Most EV companies are keeping their cell costs tight to their chest.  Of course, it seems unlikely that Li-ion will win both the mobile market (EVs) and the stationary market (which is less mass conscious)...but weirder things have happened....one learning curve is better than two.

Flow batteries are interesting, we'll see.

The problem with molten salt is of course the cost of the CSP, solar thermal....now left in the dust by PV.

As for battery recycling....cells **could** be designed for easy recycling of contents, e.g. by robots. Separate and dissolve/leach the components....has to be cheaper than many virgin materials.  But AFAIK, nobody is really thinking about that at this point.


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## georgepds (Oct 17, 2016)

you can read more here about their new plant


http://www.utilitydive.com/news/sol...ed-solar-plant-with-storage-in-nevada/428348/


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## iamlucky13 (Oct 17, 2016)

woodgeek said:


> I am not sure about your numbers.  If a conservative cost for large Li-ion batteries in 2016 is $300/kWh, and the batteries can do at least 1000 full equivalent cycles before they are so degraded as to be useless, then the storage cost is $300/1000 = $0.30/kWh.  While the rest of the facility cost is not included, it should be longer life and amortized.
> 
> This is just half of your estimate from the DOE.  The cost of Li-in batteries was $600/kWh in 2011, so the $0.60 estimate might just be from that period?
> 
> ...



I'm using the lower end of the figures from the latest copy of the DOE Electricity Storage Handbook (2015). Some of the figures may be slightly dated, but not by much. I think they're updating this handbook yearly with numbers from both manufacturers and utility purchasers of the technologies included:
http://www.sandia.gov/ess/publications/SAND2015-1002.pdf

Keep in mind, $200-300/kWh is just the cell cost, not the battery pack or system cost. The rest of the facility is a significant part of the overall cost, and financing costs and overhead have to be included, too. The hardware to convert and regulate that DC power and connect it to the grid is not cheap. Yes, it lasts longer, but some of it needs ongoing maintenance, too.

I generally hear around 2000 cycles life for stationary applications, at 80% depth of discharge, but it varies with charge and discharge rate. Faster than 2 hour charge or discharge rates start to significantly stress lithium-ion batteries.

Also, this is the passage from peakbagger's link I called out above:



> As expensive as CSP-plus-storage plants like Crescent Dunes are, their levelized cost of energy is still about half that of equivalently sized PV-plus-battery projects.



That suggests $0.27/kWh, which is in the same ballpark as what I guessed for a day and night plus generation costs average based on the DOE electricity storage handbook values.


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## iamlucky13 (Oct 17, 2016)

georgepds said:


> you can read more here about their new plant
> 
> 
> http://www.utilitydive.com/news/sol...ed-solar-plant-with-storage-in-nevada/428348/



Whoa. That's a huge jump in scale...I guess that's why they're calling it 10X.

If they actually build a 2GW farm with storage for $5 billion, it's also a huge drop in costs for solar thermal storage, even compared to Crescent Dunes. It's enough of a drop I actually wonder $5 billion is just the cost of the generating system, with storage capacity yet to be sized and priced.


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## iamlucky13 (Oct 17, 2016)

woodgeek said:


> As for battery recycling....cells **could** be designed for easy recycling of contents, e.g. by robots. Separate and dissolve/leach the components....has to be cheaper than many virgin materials.  But AFAIK, nobody is really thinking about that at this point.



It's being given some thought, but it sounds like we're still a few years away from lithium-ion recycling becoming common. A somewhat technical read here, but a decent overview of the status as of 2 years ago. Lithium-ion is covered in section 2.3:
http://www.sciencedirect.com/science/article/pii/S2214993714000037


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## georgepds (Oct 17, 2016)

iamlucky13 said:


> Whoa. That's a huge jump in scale....
> 
> I actually wonder $5 billion is just the cost of the generating system, with storage capacity yet to be sized and priced.



I thought the working fluid, salt,  was the "storage capacity" of the generating system. 

I suppose you could add more or less salt to to change the storage capacity, but, if I did it, I'd size the salt needed by the amount of energy generated in a day ( on average, or perhaps, peak) . My understanding is the storage is to  last on the matter of hours, not days weeks or months


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## peakbagger (Oct 17, 2016)

I believe the salt ultimately heats water to make steam and then its a conventional Rankine cycle. The salt just can store a lot of thermal energy.


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## woodgeek (Oct 18, 2016)

Indeed.  The heat/energy stored is associated with a phase change, the salt freezing to a solid, which occurs at a high enough temp to allow reasonably efficient thermodynamic conversion in the steam turbine.

This is a hassle as the salt filled plumbing must be kept warm when the sun goes down, e.g. by recirculation of heated salt., or the pipes freeze and restart is a bear 

This in turn increases parasitic heat losses, and means you must have some backup method for generating some heat on site (which in Ivanpah's case, you can also use to sell power).


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## iamlucky13 (Oct 18, 2016)

I don't think they ever let it cool enough for a phase change to occur. I believe the salt choice is mainly a matter of having a working fluid with a favorably high boiling temp, high specific heat, and large separation between freezing and boiling points, all of which support what you're saying about having reasonable thermodynamic efficiency, as well as the ability to store lots of heat without making the storage volume impractical.


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## woodgeek (Oct 18, 2016)

My understanding is that they do use the phase change when heating the steam....otherwise the mass is prohibitive.  There are a number of other high temp working fluids that do not solidify at room temps that they would use instead, were this not the case.


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