Some earlier ammonia discussion.

How shall driving gain nuclear cachet?

This project has particular significance as Whyalla will be in the energy spotlight. BHP Billiton has said they want 690 MW for the Olympic Dam expansion presumably including a desal plant on the nearby coast. Other new mines (eg Prominent Hill) are planning transmission lines to Roxby Downs.

OneSteel has coke ovens supplied by coal ships from Newcastle. Water and gas pipelines run down the coast, water from the River Murray and gas from Cooper Basin. Santos has a gas fractionation plant about 30km out of Whyalla where LNG ships call in once fortnight I believe, until Cooper Basin runs out.

The linked news story doesn't give an electrical output for the CSP plant, but if it supplies 10,000 homes I'll infer that as 10 MW. While that seems large it is infinitesmal compared to other captured energy flows associated with the area. The article doesn't state how long this plant can maintain output in overcast weather. To me 'baseload' means the ability to supply a specified output 24/7, barring unplanned outages.

So I see this project as a David and Goliath battle of small scale renewable versus the fossil and nuclear juggernaut.

I'm pretty excited about this method because the dishes seem to build on work that was carried out in astronomy in Australia by Hanbury-Brown and Twiss. They measured the sizes of stars using a novel form of interferometer called the intensity interferometer built near Narrabri in the 1960s.

I'm hopeful these facilities will be used in a similar way at night once they get going.

Chris

A dumb question: Where does the ammonia (NH3) come from?

There are some questions I have about this post.

First, ammonia is a poison to fauna, so will it be environmentally benign in case of rupture?

Second, the storage medium is two gases; will that not require an enormous container to hold the substantial volume?

Third, hydrogen being what it is, will there not be a necessity for extra special materials to avoid losses thereof?

Nice animated GIF. That kind of a visual, which is quite unassuming IMO, is something you can't get from a textbook.

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Wait, I thought that ammonia was the high-energy state (seeing as you can burn it). Now they're saying that it takes energy to disassociate ammonia? I thought that disassociating ammonia would release energy, and making ammonia would require energy...

Or maybe this is how it works:
6H20 + energy --> 6H2 + 3O2
6H2 + 2N2 --> 4NH3 + energy
4NH3 + energy --> 6H2 + 2N2

Net reaction: 6H20 --> 6H2 + 302

So this is basically a way to store sunlight that goes beyond simply storing hydrogen (which is difficult to store) and oxygen, but which take the hydrogen and reacts it with atmospheric methane to produce ammonia, which can be easily stored. Right?

Lots of action in this area - Dr. John Holbrook has an active project to trickle charge ammonia from a hydro facility in order to use it to replace a natural gas peaker. I just stepped out of a meeting with a lobbyist and a similar plan is going in front of Duval Patrick, governor of Massachusetts, on the 12th of next month. Another thing happened today along these lines but it's high level and touchy ... not sure if I can say anything about it yet, or if I have to wait for the big heads to bless & reveal.

Oh, and this crapping solid state ammonia synthesis pilot plant grant is open in another window and the deadline is tomorrow.

Good times here in renewable energy land ... but we do need more money to apply to the problem.

Here's a strange thing, the uranium mines use a huge amount of ammonia

Following crushing, the ore is ground and processed through a sulfuric acid leach to recover the uranium. The pregnant liquor is then separated from the barren tailings and in the solvent extraction plant the uranium is removed using kerosene with an amine as a solvent. The solvent is then stripped, using an ammonium sulphate solution and injected gaseous ammonia. Yellow ammonium diuranate is then precipitated from the loaded strip solution by raising the pH (increasing the alkalinity), and removed by centrifuge. In a furnace the diuranate is converted to uranium oxide product (U3O8).

from the UIC website. No mention of leakages from this process. The connection is that Whyalla is the nearest port that has strong sea currents. Also if Olympic Dam mine is to open up to 4 X 3.5 X 1 (kilometres that is) then they will need a lot of explosives such as ammonium nitrate. However they also need .7 GW for mine power and water desalination, about half the output of the State coal and gas fired grid. Some have suggested a 1000MW nuke right next to where this solar plant is proposed.

Thus the solar ammonia plant looks to me like a hamster caught up in an elephant stampede. Still it could all turn around with the hamster outrunning everybody.

I am not an expert but IMO Ammonia offers a better route to a solution of Energy storage than Hydrogen from what I have read up about the liquid. It has many advantages over Hydrogen:

1. Perhaps most importantly it is currently a readily available and globally transported industrial commodity in bulk
2. It is a liquid at much higher temperatures and thus storage containers can be made smaller for a given energy density
3. Leakages are reduced and are readily detected as it 'stinks' (technical term! :o)
4. It can be synthesised using non fossil fuel resources -ideally an electrical process driven by renewables

-I'm sure there are more and would like to see further TOD articles on the subject. (I understand that the process above is unlikely to have any major impact for decades even if scaled rapidly btw. having been lurking here a while)

Nick.

Hi HI Big Gav. Thanks for this post. Great work. Two years ago I saw a (secret) plan for this system that included a geothermal loop. Excess production (sunny days) were marked as "over production" to be sold on. There were even capture/holding tanks for the collection of condensed water that formed on some parts of the infrastructure.

I guess the first question that comes to my mind is to ask what the efficiency of the two reactors are, and what the costs are? Or to put it a different way, how do the costs differ for the ammonia based system and a molten salt system which stores heat instead?

If I remember my high school chemistry, the combination of nitrogen and hydrogen to produce ammonia was one of the great challenges of inorganic chemists. This is because the reaction is highly ENDOTHERMIC not exothermic. Thus there is a FATAL FLAW in the process suggested (described above).

Germany was in dire need of nitrates for explosives during world war I and Fritz Haber developed a method for synthesis of ammonia from hydrogen and nitrogen (http://en.wikipedia.org/wiki/Haber_process)and then a process was developed to convert ammonia to nitric acid, used in manufacture of explosives. Thus for the first time a method was available to "fix" nitrogen chemically. He received a Nobel prize for this process for synthesizing ammonia.

This process is now the basis for producing fertilizers and as noted above makes possible the synthesis of many explosives in large quantities. HOWEVER, the produce demands large amounts of energy and the process is an equilibrium that only produces 15% ammonia in a single cycle. Thus it could not be used in the cycle described in this posting.

WTF?

Ammonia synthesis

The final stage is the crucial synthesis of ammonia using promoted magnetite, iron oxide, as the catalyst:

N2(g) + 3H2(g) → 2NH3(g), ΔHo = -92.4 kJ/mol

This is done at 150 - 250 atmospheres (atm) and between 300 and 550 °C, passing the gases over four beds of catalyst, with cooling between each pass to maintain a reasonable equilibrium constant. On each pass only about 15% conversion occurs, but any unreacted gases will be recycled, so that eventually an overall yield of 98% can be achieved.

http://en.wikipedia.org/wiki/Haber_process#Ammonia_synthesis

Ammonia synthesis is endothermic! It takes high temperatures and very high pressures to do it. Nowhere it is explained where will those come from, and where the energy for those will come from.

What is missing from this discussion (aside from a sufficient grasp of chemical thermodynamics at times) is that this is just a variant of hydrogen storage, but with nitrogen as the abetting partner instead of oxygen.

2NH3 <--> N2 + H2

vs

2(H2O) <--> O2 + 2H2

In both cases, the recombination (reverse direction of that shown) is exothermic -- meaning that it gives off heat as it occurs. However, the formation of water is much more so (-241.8 kJ/mol) than ammonia (-46.1 kJ/mol).

In both cases, you are using sunlight to split the molecules into the respective diatomics which are then stored and later recombined to release energy. The only apparent advantage for the ammonia-based system is that you can store all the reactants and products together in one vessel.

But the reason for this underscores its biggest disadvantage. Kinetics. Nitrogen and hydrogen in a closed container won't recombine to form ammonia because the kinetics are very slow. This is, of course, the reason catalysts are necessary for ammonia synthesis. And, even with modern catalysts, high temperatures are required to speed things up. But that drives the equilibrium back towards the reactants (N2 and N2). This is due to the entropy term, as in:

dG = dH - TdS (pretend that the d's are deltas)

To compensate, high gas pressures are used. Even so, multiple passes over the catalyst is necessary. True, you eventually get back the added thermal energy, but getting a lot of heat out of the overall process seems rather problematic. Why go this route?

Hydrogen and Oxygen are much happier to recombine, needing only a little encouragement (add spark -- or rough edge on something -- BOOM). Better still, they can be recombined in a fuel cell.

Note that this ammonia scheme is distinct from STORING ENERGY IN AMMONIA, which involves energy input to create the ammonia and then releasing energy via combustion or a fuel cell.

As in any scheme where you are storing energy in the form of hydrogen gas, you are limited by the volume you can store and/or the energy it takes to compress it. All of the limitations with hydrogen storage still apply.

If there are more advantages to a closed loop system involving ammonia vs. water, they haven't mentioned them.

Perhaps slightly OT, but has anyone any idea of the efficiency of using a zinc oxide to zinc reaction?
It seems from the discussion that elements of this ammonia scheme are problematic, so I wondered if this would do any better - concentrated solar could certainly be used, although I believe you would also need charcoal.

BG:

I'm puzzled by this scheme. The heat input from Sun seems to force ammonia to dissociate into N2 and H2, but they seem to remain mixed as they flow out of the reactor where the ammonia is broken down. What keeps this mixture stable? Can't the reverse reaction take place in the storage tank? I would think this is a serious problem because the reverse reaction, making ammonia from N2 and H2 is exothermic and, once started, will experience thermal run away. I don't doubt that they are making it work, but I do doubt that their marketing materials are telling the whole story. What are they *really* doing? Have you found a real chemical engineering discussion of this? Where?

I suspect it has to do with the heat exchangers at both the solar collector and the gas turbine in which stored energy is turned into mechanical energy. What is going on in these? What are the design criteria of these?

Also, in the pictures of the collectors, the reactor, which I suppose is at the focus of the parabola, is a very long distance from the parabola. This results in a rather low peak temperature for these collectors. Why do this? Again, I feel there is more to be said about what they are really doing.

What say you?