Energy From Thorium Discussion Forum

It is currently Aug 20, 2018 7:56 am

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 73 posts ]  Go to page Previous  1, 2, 3, 4, 5  Next
Author Message
PostPosted: Aug 09, 2016 4:58 am 
Offline

Joined: Jun 05, 2011 6:59 pm
Posts: 1335
Location: NoOPWA
E Ireland wrote:
Finding a suitable salt that isn't enormously expensive is hard.
See my previous work on this forum on that topic.

Water is enormously cheap.
True, but you can't store 315ºC energy from a typical PWR core in water unless you have exceedingly expensive vessels. And NaNO3 will store that quite well and is not all that expensive.

_________________
DRJ : Engineer - NAVSEA : (Retired)


Top
 Profile  
 
PostPosted: Aug 09, 2016 5:42 am 
Online

Joined: Jun 19, 2013 11:49 am
Posts: 1546
It is too expensive for anything other than diurnal load storage.

EDIT:
Attempting to use pure sodium nitrate is going to run into all sorts of problems, it can't be used with a BWR practically and you will need to directly and intimately contact the PWR primary loop fluid with the salt to melt it, as it only melts at ~308°C.

You would need to use the solar salt eutectic but that only melts at ~225°C and costs ~$500/t, which is $3.1/MJt
AT 225°C you will be lucky to get ~30% - which is $10/MJe, which is ~$36/kWhe


Top
 Profile  
 
PostPosted: Aug 09, 2016 5:04 pm 
Online

Joined: Jun 19, 2013 11:49 am
Posts: 1546
An alterantive salt would be a eutectic micture of calcium and sodium nitrate - which melts at 232°C but calcium is considerably cheaper than potassium.
55-45 mol%.
Which comes to about 70% calcium nitrate by weight.
The price of Calcium nitrate is going to be essentially the price of nitric acid required to make it, perhaps under $100/t

Which means the salt ends up incredibly cheap, probably something like ~$150/t - although I have not found any latent heat data for that mixture but it is probably comparable to the Solar Salt figure.


Top
 Profile  
 
PostPosted: Aug 09, 2016 5:50 pm 
Offline

Joined: Sep 02, 2009 10:24 am
Posts: 511
This is brilliant - though I need to look at it with less wine. I had assumed this was feasible with MSRs - basically replace the third loop with a massive salt tank.

E Ireland wrote:
They appear to be able to build pit storage for water at 90-95C for roughly ~$26 per cubic metre, based on the stated costs of SUNSTORE 4. In their larger stores they are capable of large scale seasonal storage and assuming a water return temperature to the pit of roughly 40C you can store ~64kWh(t) per cubic metre. Losses are fairly minor in terms of storage capacity, and would be reduced in large stores due to a higher volume:surface area ratio.

Studies on district heating cogeneration performed in Sweden seems to indicate that hot water cogeneration by an ESBWR or EPR would allow 1400MWt to be produced at 95 Celsius at the cost of only 150MWe. So 9.33MWt/MWe. Essentially a virtual heat pump with an effective COP of 9.33.


Need to be careful with these. We see a lot of deflated cost estimates going around at the moment.

Also are you sure about the Swedish study? If the cold temperature is upped from 20C to 100C, with hot at 300C, Carnot efficiency falls from 49% to 35%, which suggests a bigger loss of output than 150MWe. Am I missing something?

Quote:

95 Celsius water in the store can then be held until peak demand and be provided to a organic rankine cycle system using a working fluid like propylene. If we assume a 25C condenser temperature and 95C inlet temperature (which probably requires PCHEs or similar high performance heat exchangers) then we can obtain ~14% gross efficiency.
After derating that to account for auxiliaries we might have ~9% efficiency, which is still ~84% effective 'round trip' efficiency. We traded 1MWh of electricity production in the off peak for 840kWh of production in the peak period, although the former never actually existed.

At ~9% efficiency each cubic meter of water can store ~5.8kWh(e).
Which translates as a storage capital cost of $4.50/kWh
Which is the lowest I have seen without requiring ludicrously high temperatures and molten table salt.


Compares to $100/KWh for long term battery predictions. Might make sense for seasonal storage.
$4.50/KWh = $45 million for a Dinorwig (a 10GWh unit).

That could be very handy for a nuclear scenario. It can even out intra day fluctuations and perhaps even seasonal fluctuations.

I'm finding that with a renewables scenario (for the UK) no conceivable amount of storage makes much difference on the amount of Gas capacity needed.
http://prntscr.com/c3q9vm (this relates to UK 2050 with average demand at 72GW and 280GW of wind and 100GW of solar capacity - full report to be published soon).
This could - but it relies on nuclear.


Top
 Profile  
 
PostPosted: Aug 09, 2016 6:06 pm 
Online

Joined: Jun 19, 2013 11:49 am
Posts: 1546
alexterrell wrote:
Need to be careful with these. We see a lot of deflated cost estimates going around at the moment.

Well those store costs are based on actual stores that you can go and look at today - so I would say they are probably relatively reliable.
alexterrell wrote:
Also are you sure about the Swedish study? If the cold temperature is upped from 20C to 100C, with hot at 300C, Carnot efficiency falls from 49% to 35%, which suggests a bigger loss of output than 150MWe. Am I missing something?

It aligns with another study from Finland about supplying Helsinki using a long district heat pipeline from a nuclear power station.
Steam cycles don't like very low exhaust temperatures due to the problems that appear at very low condensor pressures - it becomes difficult to avoid parasitic pressure drops due to friction and similar.
THis is why Organic Rankine bottoming cycles can improve plant efficiency.

alexterrell wrote:
I'm finding that with a renewables scenario (for the UK) no conceivable amount of storage makes much difference on the amount of Gas capacity needed.
http://prntscr.com/c3q9vm (this relates to UK 2050 with average demand at 72GW and 280GW of wind and 100GW of solar capacity - full report to be published soon).
This could - but it relies on nuclear.


I have given up trying to find more than 400-500GWh worth of storage in the UK, even with salt water pumped storage and fitting pumps to virtually every feasible hydro scheme in Scotland to turn them into pump storage plants.


Top
 Profile  
 
PostPosted: Aug 10, 2016 5:26 am 
Offline

Joined: Jun 05, 2011 6:59 pm
Posts: 1335
Location: NoOPWA
E Ireland wrote:
It is too expensive for anything other than diurnal load storage.

Since the diurnal variation is really all we need, that is all I am aiming for. The seasonal variability allows for reactors to be taken off line for overhaul, etc.

_________________
DRJ : Engineer - NAVSEA : (Retired)


Top
 Profile  
 
PostPosted: Aug 10, 2016 5:32 am 
Offline

Joined: Jun 05, 2011 6:59 pm
Posts: 1335
Location: NoOPWA
E Ireland wrote:
EDIT:
Attempting to use pure sodium nitrate is going to run into all sorts of problems, it can't be used with a BWR practically and you will need to directly and intimately contact the PWR primary loop fluid with the salt to melt it, as it only melts at ~308°C.

You would need to use the solar salt eutectic but that only melts at ~225°C and costs ~$500/t, which is $3.1/MJt
AT 225°C you will be lucky to get ~30% - which is $10/MJe, which is ~$36/kWhe


If we can't get NaNO3 to work because it has too high a melting point, then NaNO2 would probably do quite well instead.

The other thing to remember is that such thermal storage really won't be needed until a lot more 1x24/7 plants are built. By the time the 2x12/7 plants are needed, the choise of storage salt might be totally different because the reactor itself is totally different.

_________________
DRJ : Engineer - NAVSEA : (Retired)


Top
 Profile  
 
PostPosted: Aug 11, 2016 1:23 am 
Offline

Joined: Dec 05, 2008 8:50 am
Posts: 336
Just curious, what about compressed air for energy storage, instead ?


Top
 Profile  
 
PostPosted: Aug 11, 2016 6:54 am 
Online

Joined: Jun 19, 2013 11:49 am
Posts: 1546
KitemanSA wrote:
E Ireland wrote:
It is too expensive for anything other than diurnal load storage.

Since the diurnal variation is really all we need, that is all I am aiming for. The seasonal variability allows for reactors to be taken off line for overhaul, etc.


Unfortunately seasonal demand swings in an all-electric system in the United Kingdom appear to be on order 50+ GWe each year.
Since we are looking at one 2-3 week reactor outage every two years for each reactor that is far too much capacity in summer to eat up solely with overhauls etc.

I am looking at ways to couple ther eactors to industrial processes that could make productive use of very cheap electricity in the summer months, but cheap seasonal storage would make all that unnecessary and significantly reduce the required size of the reactor park.

Alex P wrote:
Just curious, what about compressed air for energy storage, instead ?

I've considered that as well - unfortunately on land pressure vessels will be far too expensive and since the loss of Ireland in '22 the UK has not had the easy access to very deep water close to sure required to make underwater gas bags very practical.
The deepest water close to shore is in a bay in the North West of Scotland - and given the current political situation that might not around for much longer either.


Top
 Profile  
 
PostPosted: Aug 11, 2016 10:26 am 
Offline

Joined: Dec 05, 2008 8:50 am
Posts: 336
Anyway, the wisest thing to do to store a lot of energy/electricity is to "convert" them to hydrogen (via higher efficiency low temp electrolisys) and then to useful liquid fuels, for example methanol or DME through biomass gasification (with external hydrogen and low temp heat, it needs a very bit of it). This is a smarter option because we will always need a lot of liquid fuels (at least for airplanes, ships, trucks, etc...) even in a deeply electrified energy system that is indeed the optimal way to go, rather than store electricity to have the same product as output (electricity -> electricity), either in the form of compressed air, heated salts or electric battery


Top
 Profile  
 
PostPosted: Aug 11, 2016 10:52 am 
Offline
User avatar

Joined: Dec 22, 2015 8:40 pm
Posts: 356
Location: Florida
From four years ago:
How it Works: CO2 + H2 = Jet Fuel

NRL has developed a two-step process in the laboratory to convert the CO2 and H2 gathered from the seawater to liquid hydrocarbons. In the first step, an iron-based catalyst has been developed that can achieve CO2 conversion levels up to 60 percent and decrease unwanted methane production from 97 percent to 25 percent in favor of longer-chain unsaturated hydrocarbons (olefins).

In the second step these olefins can be oligomerized (a chemical process that converts monomers, molecules of low molecular weight, to a compound of higher molecular weight by a finite degree of polymerization) into a liquid containing hydrocarbon molecules in the carbon C9-C16 range, suitable for conversion to jet fuel by a nickel-supported catalyst reaction.
Image

Proof-of-concept, correct? This is an electrolytic seacoast possibility for effectively storing the excess energy in synthetic carbon fuels that once burned, continue to keep the atmospheric carbon load at some equilibrium state. But that is on the side and off topic. Apologize, E. But your discussion is under "electricity storage" and if hot water has limits, Alex P's suggestion leads to work in this area.

For those who believe that global warming and ocean acidification due to increasing atmospheric carbon is NOT a hoax, as long as large-scale carbon capture and storage (CCS) is implemented with co-located nuclear make-up (LFTRs, SMRs) to compensate for the CCS energy consumption (that kills the CCS business case) together with new nuclear replacement of coal- and gas-fired generation, that creates a net decreasing atmospheric carbon load, the coastal electrolytic synfuel storage component is carbon-cycle neutral and slows the decreasing carbon load.

Already recognized for the industrial chemical processes is new nuclear direct thermal that skips the electrical step.

If you’re paying attention you might have noticed some problems with this plan. The most obvious is that to do all of this you need a ton of energy in the first place, not just to run the process but to pump up all this seawater initially. If your ship is generating electricity from fuel, then you’re going to end up burning more than you actually create with this process. In order for this to make sense, then, you need something more hardcore . . . something like the reactor on a nuclear-powered aircraft carrier.

In fact, if you actually read some of the reports out of this project, nuclear power is exactly where they’re going with it, but that point was completely missed by the International Business Times and other publications, as the American Spectator rightly points out.

That may not be such a big issue, though. Nuclear power is one of the cleanest and most practical alternative energy sources available at the moment, and even if fuel spun from seawater costs more to produce, you’re saving on the cost of getting that fuel to where it’s needed and ensuring that your fleet can operate even in the event that its supply chain is disrupted. Strategically, it makes a lot of sense.

_________________
"Those who say it can’t be done are usually interrupted by others doing it."

—James Arthur Baldwin, American novelist, essayist, playwright, poet, and social critic


Last edited by Tim Meyer on Aug 11, 2016 11:44 am, edited 5 times in total.

Top
 Profile  
 
PostPosted: Aug 11, 2016 11:18 am 
Offline

Joined: Dec 05, 2008 8:50 am
Posts: 336
For example, I remember a study where with electrolisys at moderate temperature (~ 150 °C) we can produce hydrogen at an energy cost of only 35 electric kWh per kg, rather than ordinary 60+ kWh/kg at ambient conditions (obviously, at an although tiny thermal energy cost). One mole of H2 is "free" from the gasification of biomass, thus through the reaction CO + 2H2 = CH3OH we can produce something in the range of 1250 liters of MeOH per tonn of dry biomass (IIRC) with an energy cost of 2 kWh of electricity per liter of MeOH (having half the LHV of gasoline), that it eventually can be easily converted to DME, a powerful diesel and gas turbine fuel. And at last we can even get an useful low temp heat as district heating (or partially to power the first step of the process as previously stated)


Top
 Profile  
 
PostPosted: Aug 11, 2016 1:27 pm 
Online

Joined: Jun 19, 2013 11:49 am
Posts: 1546
Based on the idea of using heat from a LWR to improve the efficiency of electrolysis I went looking for articles on high temperature alkaline electrolysis (based on the idea that those cells would be the easiest to engineer for enormous pressures) and found all sorts of interesting materials.

This article indicates that a cell operating at 240 Celsius and about 40 bar, using relatively cheap electrodes (most expensive material is small quantities of silver) can operate at 98-88% electrical efficiencies using heat input at temperatures that our LWRs are easily capable of providing using live steam.
At 1A cm-2 the cells would cost only ~$90/kW in raw material costs, even if an order of magnitude of that is the price including fabrication costs you are looking at under a dollar of watt.

At 1A cm-2 the cell voltage is ~1.5V, which leads to an electricity consumption of roughly 40kWh/kg of hydrogen produced, which is close to 100% efficiency on an electrical HHV basis.

If operated at 2A cm-2 the cell voltage is 1.75V requiring ~46.9Wh/kg. However the price of the elecrolyser materials will drop from ~$90/kW to ~$40/kW, leading to total cell capital costs of something like 50 cents per Watt in all up costs being plausible.

Especially as hydrogen and oxygen would be generated already compressed at 40 bar, which whilst not quite high enough to pump into a store directly, it will drastically reduce compression costs.

Either way you can produce hydrogen for easily under a dollar a kilogramme using summer electricity [which is worth the fuel cost pretty much], even accounting for some loss of electricity production in the form of live steam being diverted to keep the cells hot (probably in the face of heat leaving the cells in the produced gasses and heating the feedwater and losses through the cell walls).

EDIT:

More recent work by the same group as that first paper has produced this paper - which indicates 3.75A/cm-2 at 1.75V and 1.75A/cm-2 at 1.5V is now achievable at 200 Celcius and 20 bar. The latter is something like 99% HHV efficient with commercial current densities (1-2A/cm-2).


Top
 Profile  
 
PostPosted: Aug 11, 2016 3:13 pm 
Offline

Joined: Dec 05, 2008 8:50 am
Posts: 336
Tim Meyer wrote:
From four years ago:
How it Works: CO2 + H2 = Jet Fuel


IMHO, an approach starting from biomass gasification is more powerful, because : 1) the CO is "free" from gasification, unlike CO2 (it takes a lot of energy to take it from air or water), 2) starting from CO, it takes only two moles of H2 to produce one mole of MeOH, unlike 3 moles of H2, not producing any water steam with the reaction : CO2 + 3 H2 = CH3OH + H2O, 3) starting from CO and gasification one mole of H2 is also "free", basically gasification produces a syngas containg a molar ratio of CO/H2 ~ 1, 4) methanol and DME are the lightest thus the cleanest liquid fuels ever possible (respectively, as substitute of gasoline and diesel fuel or kerosene in airplanes), basically producing no soot or pollution, 5) both methanol and DME can be used in today vehicles with minimal modification and are very powerful and efficient IC fuels (high octane/cetane number).

EDIT: obviously, I know that within this approach we neeed a lot of "waste" biomass, while CO2 is "free" (actually, it isn't...), but indeed as I wrote before with external hydrogen and low temp heat, we only need a minimal amount of it, not a negligible quantity, but I think/hope a pratical amount, overall - particurally, if the aim is to store otherwise wasted electric energy, with an intrinsecally low market value (e.g. off-peak electricity) to produce high market value added transportation liquid fuels


Top
 Profile  
 
PostPosted: Aug 11, 2016 3:51 pm 
Offline
User avatar

Joined: Dec 22, 2015 8:40 pm
Posts: 356
Location: Florida
I find this an excellent discussion, E and Alex. E: You say LWR heat. Your focus here is storage independent of the source of heat?

Alex P: The CO from biomass is better. The Navy doesn't have that option at sea, of course.

_________________
"Those who say it can’t be done are usually interrupted by others doing it."

—James Arthur Baldwin, American novelist, essayist, playwright, poet, and social critic


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 73 posts ]  Go to page Previous  1, 2, 3, 4, 5  Next

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group