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PostPosted: Aug 12, 2016 9:17 am 
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E Ireland wrote:
If I do manage to create such a model I will share it with the forum. I can then input last years temperature data, adjust for COP and superimpose it on the electricity demand to create an overall heat demand model.


We should be publishing our model soon - just waiting for my co-author to get back from hols - and then I'll share the data.

I assumed slightly better heat pump performance and good thermal mass (relative to leakage) in the housing stock of 2050.


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PostPosted: Aug 12, 2016 9:32 am 
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Our real problem is even if we made all new houses have enormous 5000L thermal stores (which doesn't seem like a bad idea really) those houses will not make up a dominant part of the housing stock for decades.


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PostPosted: Aug 12, 2016 9:44 am 
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E Ireland wrote:
Alex P wrote:
I think that gasification of biomass is better anyway because convert all (or almost all) the carbon in biomass into useful hydrocarbon-based liquid fuels (again, particurally with external hydrogen and low temp heat), unlike fermatation (for example, fermantation of corn or sugar cane to get ethanol) or hydrolysis and it's basically a process that is quite simple, pratical and available still today, unlike many other exotic proposals, including final products infrastructures


I Was proposing fermentation to value added products, not commodity chemicals like bioethanol - I mean things like Pruteen and Quorn, or fine chemicals, or even humulin. Even humble xylitol (produced by hydrogenation of the xylose fraction) is worth well over $1000/t - which is an enormous value for its carbon and non water hydrogen content.

And lignin cracking can produce fine chemicals like vanillin and whatnot that are all worth considerably more per tonne than simple hydrocarbon fuels.


I think we are wandering a bit off - if our target is to store efficiently large amount of electricity, otherwise wasted or not used at its max, then producing biomass-based liquid fuels is an interesting way to go


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PostPosted: Aug 13, 2016 3:32 pm 
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E Ireland wrote:
Our real problem is even if we made all new houses have enormous 5000L thermal stores (which doesn't seem like a bad idea really) those houses will not make up a dominant part of the housing stock for decades.


But an old house might have 100 tons of bricks or concrete. Put the insulating shell around that, and you have your thermal store.

Modern houses with good thermal mass might only lose 1C per day with a 20C temperature differential.

Some modern techniques, like SIPs, are great for insulation, but poor for thermal mass.


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PostPosted: Aug 13, 2016 6:40 pm 
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It appears that DME can be held liquid at room temperature under only 5atm of pressure, so any of those storage depots could store it in liquid form easily, which means there is no need for cushion gas or any of that [can use a nitrogen purge to hold reservoir pressure up]. Salt caverns are workable because the material is not miscible with water and is not hydroscopic, so should not dissolve salt from the cavern walls.

300,000 cubic meters of DME at room temperature is about ~195kT of fuel.
Production process is not particularily exothermic, so the heating value of the input hydrogen seems likely to be preserved.

HHV is ~31.7MJ per kilogram. It requires something like 12kg of hydrogen to produce 46kg of DME from carbon dioxide. That means that at our 40kWh/kg hydrogen production target we require ~10.4kWh per kilogramme of DME produced. Call it eleven with various inefficiencies.
11kWh(e) in to produce something like ~5.3kWh(e) per kilogramme of fuel out at 60% net efficiency. Which is a lousy return rate really, but what can do you do. On the plus side at 5MWh(e) per tonne of DME fired in a CCGT the single store would have a storage capacity of 875 Gigawatt hours albeit at a 49% end to end efficiency assuming ~100% efficient electrolysis.

Improvements in turbine firing efficiency (which has already climbed to 61.5% as of January with a new plant in Germany) will help, and if we can get some heat recovery on the DME production plant.

Carbon dioxide could be obtained in the summer through a gas capture network (Established to avoid carbon taxes or similar for industrial concerns) or simply by electrically firing lime adjacent to the plant. THe lime being sold to pay for the limestone purchases and to partially defray the electricity cost.

EDIT:

It appears that dimethyl ether reactors are typically run at 60+ bar and ~260C - which is nice because it means waste heat released by them is going to generate steam conditions usable power for production, which means that waste heat can be recovered with ~25-30% efficiency.
Also our very high pressure electrolysis cells will reduce hydrogen compression costs.
If we use very high efficiency modern chopper rectifiers on the electrolysis system, run the electrolysers less hot, integrate the waste heat system properly and fit heat recovery turbines on the DME reactor (I think we can do a single 'pot' syntheiss with reverse water gas shift, methanol synthesis and dehydartion in the same reactor) I think we can get the input energy requirement down to ~10kWh(e) per kg DME.

Which gets us to the all important ~50% end-to-end efficiency, which is still abysmal but not bad for such a cheap ~Terrawatt-hour range energy store. Electrolysers and plant and the store itself probably could be built for a billion pounds or similar. If the US turbine efficiency programme manages to reach 65% net efficiency then we would reach ~49-55% efficiency with the modifications suggested above.

But if off peak electricity is charged at fuel, incidental maintenance and a token capital contribution then 55% efficiency to convert it into winter generating capacity is probably worth it. After all such electricity is producable for a marginal cost of only about ~$15/MWh


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PostPosted: Aug 14, 2016 11:08 am 
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If I remember correctly my own calculations, using the usual reaction of CO + 2 H2 = CH3OH and assuming one mole is "free" from biomass gasification and that with low temp electrolysis (at only 150 °C, if I recall it correctly) we can produce hydrogen at an energy cost of only 37,5 kWh per kg (plus a lot of low temp thermal energy, I don't remember the exact number), we can produce methanol at cost of a bit less than 2 kWh per liter, where LHV of MeOH is 20 MJ/kg, or 4,4 kWh per liter. From methanol, if needed, we can easily produce DME


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PostPosted: Aug 14, 2016 11:32 am 
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THat would require many millions of tonnes of biomass to produce that level though, if we go for the low-input model then even Miscanthus struggles to get above ten tonnes per hectare per year in the UK climate. And biomass is only ~40% carbon by mass.

If we really want to produce large quantities of methanol/DME without turning the country into one enormous biomass plantation we are going to struggle to get enough carbon to avoid direct hydrogenation of carbon dioxide.
Apparently much research has been done and catalytic systems have been discovered that are useful for direct hydrogenation of carbon dioxide to DME and Methanol.


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PostPosted: Aug 14, 2016 2:04 pm 
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E Ireland wrote:
Apparently much research has been done and catalytic systems have been discovered that are useful for direct hydrogenation of carbon dioxide to DME and Methanol.
"Much"? One effort by the U.S. Navy reported in 2014 but for "a liquid containing hydrocarbon molecules in the carbon C9-C16 range, suitable for conversion to jet fuel by a nickel-supported catalyst reaction."
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 [my emPHAsis] from 97 percent to 25 percent in favor of longer-chain unsaturated hydrocarbons (olefins).
But if tuned for max Me, still to get your target amounts, the seawater processor would have to be "huge" with major throughput—lots of energy needed for that (from thorium). But what a magnificent achievement that would be as long as marine life and ecosystems were protected at the intakes and discharges.

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PostPosted: Aug 14, 2016 3:20 pm 
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Plenty of work from what I can tell

EDIT:

If we drop the current density considerably, to 200mA cm-2 (on the old cell designs, probably a bit more with the later designs that I don't have precise figures for), the forward cell voltage drops to 1.25V. That means it would require 120MJ per kilogramme in electricity and 20MJ would be pulled from the heat in the cell, so would have to be provided in ~250C heat.
That 1kg of Hydrogen is then reacted as described above with carbon dioxide to produce 3.83kg of DME, 140MJ of hydrogen is used to produce something like [31.7*3.83] ~120MJ of DME. Which is handy, since the reactor is at ~260 Celsius that 20MJ of waste heat can be recycled to the electrolysis plant.

So essentially we require 120MJ of electricity and no excess heat (apart from steam for make up) to produce 3.83kg of DME.
Otherwise known as 31.3MJ(e) per kilogramme of DME. Or 8.3kWh per kilogramme DME.

So 8.3kWh will generate ~5kWh later using a high efficiency CCGT operating in cold weather.
So actually ~60% end to end, which is very nice. Although it requires a substantially larger electrolysis stack.


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PostPosted: Aug 15, 2016 2:24 am 
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E Ireland wrote:
THat would require many millions of tonnes of biomass to produce that level though, if we go for the low-input model then even Miscanthus struggles to get above ten tonnes per hectare per year in the UK climate. And biomass is only ~40% carbon by mass.

If we really want to produce large quantities of methanol/DME without turning the country into one enormous biomass plantation we are going to struggle to get enough carbon to avoid direct hydrogenation of carbon dioxide.
Apparently much research has been done and catalytic systems have been discovered that are useful for direct hydrogenation of carbon dioxide to DME and Methanol.


If I remember it correctly, with external heat and hydrogen we can even get 1250-1300 liters of methanol per dry tonn of biomass, thus for, say, a production of 50 billions liters per year (equivalent of 25 billions l/year of gasoline) and so a potential of electricity storage of ~ 2 kWh per liter* 50* 10^9 l/y = 100 TWh/year, we'd need 40 millions tonn/year of biomass, equivalent of about 5-10 million hectares - not a tiny amount, but I guess quite pratical for a mid-size European country like UK.

E Ireland wrote:


But where do you enivisage to get all that CO2 from? I do believe that this approach is a weak one, in the end, basically because starting from CO2, as I already said, needs three moles of hydrogen (so much more energy) instead of only one from CO and gasification and it takes a lot of energy to get the CO2 from air as well


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PostPosted: Aug 15, 2016 5:22 am 
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Alex P wrote:
But where do you enivisage to get all that CO2 from? I do believe that this approach is a weak one, in the end, basically because starting from CO2, as I already said, needs three moles of hydrogen (so much more energy) instead of only one from CO and gasification and it takes a lot of energy to get the CO2 from air as well


Regenerative lime kilns consume roughly 1MWh per tonne of lime in the form of very high temperature heat.
The gassing off of ~1.8 tonnes of limestone to produce ~1 tonne of lime will release ~800kg of carbon dioxide

So we require something like 1.25MWh of electricity to produce a tonne of carbon dioxide.
Which sounds like a lot, but when you consider it is produced in an essentially pure carbon dioxide stream from a raw material available almost anywhere and produces a very useful byproduct it is not that bad.

Since this is summer, $20/MWh is probably acceptable for the electricity, so that costs only $25, so $20 per tonne limestone and you are looking at a price of $36 for that.

So that is a materials and energy price of ~$61 to produce a tonne of carbon dioxide which will also produce ~1.25 tonnes of lime.
So your production cost for carbon dioxide could be as low as ~$20-30/t including capital on the regenerative kiln.
And since you can export lime easily on ships for very low costs if your kilns and quarries are properly sited, and ther eis literally no shrotage of limestone feedstock it can be scaled up to enormous production.

Hell you could probably hold the lime in solution in giant lagoons at sea if you wanted to soak up carbon dioxide from the atmosphere, which would also allow limestone costs to become negligible from recycling. Holding the cost down at about ~$35/t.

2.5 million of lime is produced in the UK every year anyway - which is potentially ~2 million tonnes of carbon dioxide before we even start on producing additional lime for export or disposal.

EDIT:

5-10 million hectares is 50,000-1000,000 square kilometres, which is 20%-40% of the entire land surface of the United KIngdom.


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PostPosted: Aug 15, 2016 3:26 pm 
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E Ireland wrote:
2.5 million of lime is produced in the UK every year anyway - which is potentially ~2 million tonnes of carbon dioxide before we even start on producing additional lime for export or disposal.

EDIT:

5-10 million hectares is 50,000-1000,000 square kilometres, which is 20%-40% of the entire land surface of the United KIngdom.


The UK avialable land is actually just about 20 million hectares, obviously UK is too small and densily populated, like any other European state, to be completely indipendent for every biomass need, including food, timber or bio-energy (either for heating or bio-fuels, that in this case are very inefficient like every biomass based liquid fuel today carried out).
On the other hand, UK clearly does NOT even need such a huge amount of bio-methanol (or DME) that is basically 1/3 or 1/2 of its entire liquid fuel consumption, including ships, airplanes, trucks, etc...50 billion liters of MeOH per year corresponds to about 55 million tonn/year of CO2, that is a monstrous amount...


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PostPosted: Aug 15, 2016 5:49 pm 
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Alex P wrote:
The UK avialable land is actually just about 20 million hectares, obviously UK is too small and densily populated, like any other European state, to be completely indipendent for every biomass need, including food, timber or bio-energy (either for heating or bio-fuels, that in this case are very inefficient like every biomass based liquid fuel today carried out).
On the other hand, UK clearly does NOT even need such a huge amount of bio-methanol (or DME) that is basically 1/3 or 1/2 of its entire liquid fuel consumption, including ships, airplanes, trucks, etc...50 billion liters of MeOH per year corresponds to about 55 million tonn/year of CO2, that is a monstrous amount...


Well that is only a tenth of UK Carbon Dioxide emissions.

And Methanol has the advantage that it can be used as a highly energy dense feedstock for the production of animal feed protein from the bacterium Methylophilus methylotrophus - lots of research was done under the brand name of Pruteen by ICI in the 1980s.
It could replace things like soybean meal imports that run to something approaching a million tonnes a year, and would enable a major expansion in food production in the UK by drastically reducing animal fodder crop requirements.
Assuming we can make it cheap enough - and we apparently can.

Methanol and DME can also be used as feedstocks for the manufacture of olefins and numerous other things through things like the Honeywell MTO process and the Methanol to Gasoline process, the name of which I forget, I do recall a lot of development work was done on the latter in New Zealand however.

Beginning to think we would need a national network of carbon dioxide pipelines and put a tax of ~$150/t of carbon dioxide release from industrial concerns, with the proviso that carbon dioxide will be taken away free by the national network, who will install pipelines to their facility on request, paid for by the tax receipts.

That would give us a huge supply of carbon dioxide.

EDIT:

It appears that whilst DME can be stored in salt caverns relatively easily (salt seems to have a solubility of less than 0.5g per kg solvent in it, so all the 175kT in that storage cavern would contain something like 80 tonnes of salt at most), Methanol will dissolve roughly ~1.4% of its mass of salt, which means that the salt cavern would lose over two kilotons of salt every time the reservoir was cycled.
It would not last that long under those conditions I would wager - however it may be possible to control the dissolution by simply using a multiple effect distillation plant to seperate methanol being removed from the depot from the salt dissolved in it, and then redissolving that salt into fresh methanol being pumped into the store. That way the introduced methanol would already be saturated and unable to dissolve any further salt from the walls of the cavern.

But I would have to do some research on that and consult more widely. But DME is good in these stores and I think they are politically the best choice, simply because they are out of sight and have enormous capacities for the cost of them, they can even be built at undersea sites without an enormous increase in cost.


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PostPosted: Aug 16, 2016 4:46 am 
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There is a body of research on salt storage. Water is too volatile for power production. It was developed for solar heat but there is no bar in using it for nuclear heat.
https://docs.google.com/viewer?url=http ... e-2013.pdf
DME, in my opinion, is only a good alternate as fuel at lower pressures. There will always be a requirement of liquid fuels for transportation.I wonder if fuel cell-electric propulsion will replace IC engines. A bigger battery may be handy and is already in initial use.


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PostPosted: Aug 16, 2016 10:25 am 
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Interesting enough, even using that very inefficient way to get the CO2 (from limestone/lime) and the most inefficient reaction to produce methanol (and thus DME : CO2 + 3 H2 = MeOH + H2O) the energy cost to produce CO2 is only a quite tiny fraction (~ 20% of the total, if I don't get it wrong) than the energy to produce the hydrogen required (assuming high efficiency low temp electrolysis at 35-40 kWh per kg H as usual) - or, if we prefer, the energy cost of hydrogen production is overwhelmingly preponderant on all the rest. I've never guessed about that !


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