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Author: Subject: Solar energy a pipe dream?
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[*] posted on 19-7-2011 at 01:38


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If someone invents an inexpensive, rapidly responsive, non-geography-dependent storage mechanism for renewable energy I'll go from cautiously optimistic about solar to downright bullish.


This is in my opinion the crux and the bag of sand tied to the bicycle that's trying to move towards renewable energy.
Even new uncommercialised energy storage technologies of today still have discouraging drawbacks that restrict them to someone's lab. Efficiency, longevity, robustness, cost, capacity, intricity, toxicity, etc are a few. I've spent hours reading about VRB's, Zn/Br redox, metal air, NaS batteries, NiH cells, K-ion cells, a spectrum of fuel cells, flywheels, supercaps, and whatever else I cannot recall now and all of these feature at least one nasty drawback, especially on a homeowner's level with PV's on the roof. It's a problem. We have environmental energy capturing appreciably sorted, we just don't have anywhere to effectively put that energy. Running a grid directly without load levelling is not an option either.
The most attractive energy storage technology I've found to be possible a candidate is the NiH battery (the pressurised type) with a longevity of over 10 000 cycles, far better than anything else out there, and it's not even new.




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[*] posted on 19-7-2011 at 14:11


I've always thought the first step for introducing solar should be domestic water heating. Its more efficient than PV's, and the water cylinder provides inherent energy storage. The tech can be anything from painted black pipes to mirror enhanced, vacuum encapsulated heat pipes with selective absorber coatings.
Heating water takes a lot of energy - taking that load off the grid makes sense to me.

I don't think there is a magic bullet for renewable energy - it is going to take a wide mix of technologies to create reliable energy supply, including fossil and nuclear sources. The trick is to change the balance from 10% renewables to 90% or more.

[Edited on 19-7-2011 by Twospoons]




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[*] posted on 21-7-2011 at 17:16


Come on guys. Just let the plants do the energy capturing for us. They've been fine tuning it for billions of years. And then you don't have to figure out how to power the transportation sector with electricity.

Switchgrass will grow damn near anywhere in the country, make at least 10 dry tons of biomass/acre/year. The energy input needed to plant and harvast it is near 5% of the energy captured. And it uses already mature hay processing technology. Eventually algae may end up being more productive, especially with direct capture of CO2 produced from various stationary sources.
Plasma gasify that shit (along with all the other collectable organic waste in the country) to high purity syngas. Conventional gasifications works too, but it seems really tough to get the tar production to a manageable level. From there you can generate electricity via IC engines, turbines, or fuel cells. Transportation fuel can be produced simply by catalytic reactions to form hydrocarbons through the Fischer-Tropsh route, or methanol (which has the advantage of being directly usable in fuel cells) along with all the other petrochemicals that we use to make plastics, etc. Hydrogen could be produced in high yield from syngas via the water gas shift reaction if you'd rather deal with the headache of hydrogen storage/transport.
All but the plasma gasification is well proven technology..
Ideally a relatively simple and cheap system could be developed using easily available parts that would allow fully decentralized production of liquid fuel, electricity and heat directly by anyone with a source of cheap biomass. Can't wait to see how the oil companies react to that! :D It seems at least somewhat possible since the entire (microwave) plasma gasification --> Fischer-Tropsh reaction can be performed at atmospheric pressures, and no expensive catalysts are required. You might even be able to decentralize the needed nitrogen fertilizer production using microwave plasma reaction of air to form NO..
I think the only way we're ever going to pay reasonable prices for energy is to decentralize it. That's the only way I can see to get real competition. The oil companies have a monopoly that they're not going to give up easily. The only way is to force them by making the technology available to a large number of people. The government is never going to help that happen either, so it's pretty much up to us..


[Edited on 22-7-2011 by 497]
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[*] posted on 21-7-2011 at 18:27


I agree that biomass will have a valuable role to play as feedstock for chemicals and aviation fuel, but for replacing fossil fuel electricity or automotive fuels it's lackluster unless you have a very low population-to-land ratio.

Plants aren't very good at converting solar energy to human-usable forms. You can get about 188 gigajoules (thermal) of energy back out of that acre's worth of switchgrass per year. Maybe 85 gigajoules electrical can be realized, if you burn it in a high performance supercritical steam turbine system. By comparison, an acre of 15% efficiency solar panels will yield 3980 gigajoules of electrical energy per year at average insolation in the USA. You can also site solar panels where switchgrass won't grow, like in deserts and on roof tops. Switchgrass gets some credit for providing its own energy storage system and for being cheaper to reproduce than manufactured panels, but not enough (IMO) to offset the 20 to 45-fold efficiency advantage of artificial systems.




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[*] posted on 21-7-2011 at 23:57


Good points. I did fail to emphasize the more important source of biomass: algae. Grow it in dirt cheap polyethylene bag photobioreactors on the ocean or anywhere else. 20-40 dry tons/acre/year is a reasonable estimate. Uses wastewater as nutrients and CO2 from power generation.

You also didn't mention how much an acre of solar panels costs.. From some quick googling it looks to be on the order of $3-6 million initial investment per acre plus maintenance. Then you must have a massive battery bank or other storage system to allow a smooth supply of power when its not sunny. And all with only a 30 year lifespan.. Additionally you didn't take into account the problems of providing transportation fuel from the electricity. A biomass source that can be directly converted to a liquid fuel usable by current vehicles seems to be very valuable thing.

Until someone figures out a good way to build your own PV panels, all those millions of dollars per acre will keep going to supporting the monopoly.

So I'll have to humbly disagree on this one. I'd much rather spend a thousands of dollars to outfit my acre of land with my home built photobioreactor-plasma gasifier system which could provide me with heat, power, fuel for my car, and potentially a supply of highly nutritious animal/people feed, than spend a few million on solar panels and batteries that will give me a bunch of electricity that I could most likely buy for around 12 cents/kwh.. And the damn utility companies won't even buy your power for that much in many places.

Edit:
After doing more research into algae I have found several very promising new ways to extract the valuable materials from algal cells. This patent basically runs the algae through an electrolysis cell to burst their cell wall and allow easy separation of the lipids in a flotation tank. Avoids the headache of filtering and drying the algae.
Even more interestingly, I found ways to extract goods out of algal cells without killing them. This obviously allows much higher production rates than traditional destructive extraction methods. They look quite viable for scaling down for use in decentralized systems. Basically you extract the compounds of interest from the living cell with a biocompatible immiscible solvent. Dodecane, etc is used. Kerosene should work :D Exciting stuff! This is a very detailed and long winded paper about extraction of beta carotene from algae. This is a patent based on the same principal, but directed toward lipid extraction rather than high value chemical extraction. They also figured out that sonocating the algae/solvent mixture was more effective than mechanic mixing. Thisis another interesting patent that details effective ways of cycling the conditions of an algal culture to maintain the dominance of the desired species in the presence of competitors, particularly in open pond style cultivation.

[Edited on 22-7-2011 by 497]
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[*] posted on 22-7-2011 at 03:05


Here is a nice large passive and cheap solar energy collector ... http://www.gizmag.com/enviromission-solar-tower-arizona-clea...

The thing about biomass is that currently we are, directly or indirectly, eating most of what we can produce, and I don't think that is going to change much in the near future.

Also, there is a little confusion about the source of CO2. The problem is with burning fossil fuels. Carbon that has been locked away from the biosphere for geological ages. Once in the biosphere it circulates between biomass and CO2 with a relatively short half life. Biomass, forests, algae, animals .... they are all just temporarily solid carbon. Part of the biosphere pool. It is the continual additions to that biomass/CO2 pool that are not reversible and that are of concern. So South Americans burning ethanol are not doing anything to the balance, but Shell Oil and their ilk and coal mining are another matter.
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[*] posted on 22-7-2011 at 03:28


Yeah I can't deny those passive towers are a cool idea. I still don't like the fact that it must be done on a massive multimillion dollar scale though.

The point is not to utilize fossil fuel CO2 (though that would be inevitable in the short term), but to utilize the very same CO2 that you get from burning the algae or other biomass to grow more algae. It just makes things more efficient because the algae can grow more rapidly with a high concentration of CO2. It makes no sense to dilute it with huge amounts of air and then make the algae work harder to extract it back out.
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[*] posted on 22-7-2011 at 04:54


Quote:
Come on guys. Just let the plants do the energy capturing for us. They've been fine tuning it for billions of years.


Unfortunately, their goal has not been to optimize energy storage efficiency; thus the efficiency of conversion to storage is not really very high.

Quote:
And then you don't have to figure out how to power the transportation sector with electricity.


Doesn't look like a whole lot more figuring out needs to be done. We have electric cars that work pretty well, with further advances in the pipeline.

Quote:
Switchgrass will grow damn near anywhere in the country, make at least 10 dry tons of biomass/acre/year. The energy input needed to plant and harvast it is near 5% of the energy captured.


What about the other inputs (NPK)?

Quote:
Eventually algae may end up being more productive,


Algae production of fuel will never be economical. The efficiency is too low, avoiding contamination by competing organisms too hard, and the workup (for want of a better term) to extract the fuel and recycle the nutrient matter is a PITA (at least economically).

Quote:
Plasma gasify that shit (along with all the other collectable organic waste in the country) to high purity syngas.


Nothing says 'easy and economical' like bringing plasma into it!

Really, you seem to know a lot about the processes, the chemistry, and the industry behind all this, but I don't think you've looked at the economics hard enough.
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[*] posted on 22-7-2011 at 05:22


Quote: Originally posted by Paddywhacker  
Here is a nice large passive and cheap solar energy collector ... http://www.gizmag.com/enviromission-solar-tower-arizona-clea...

The thing about biomass is that currently we are, directly or indirectly, eating most of what we can produce, and I don't think that is going to change much in the near future.

Also, there is a little confusion about the source of CO2. The problem is with burning fossil fuels. Carbon that has been locked away from the biosphere for geological ages. Once in the biosphere it circulates between biomass and CO2 with a relatively short half life. Biomass, forests, algae, animals .... they are all just temporarily solid carbon. Part of the biosphere pool. It is the continual additions to that biomass/CO2 pool that are not reversible and that are of concern. So South Americans burning ethanol are not doing anything to the balance, but Shell Oil and their ilk and coal mining are another matter.


Solar towers cheap? In what universe? :D
Do you have any idea how hard it is to build huge structures? That tower is twice the size of ESB.

No way, Jose.
Honestly, I thought that majority of people on this forum will understand the problems with renewables, becuase everyone si "sciency" and all that, but it seems to me that the situation is only slightly better than on other, general purpose forums.

Solar towers are a stupidity collosal almost as their size, rejected and laughed upon in the year following their popularity spike on the web, few years ago. I mean, solar molten salt with those reflectors is very expensive, let alone a big ass concrete tower with a huge hermetically sealed area. No one would want to pay for such expensive electricity, and the cost return time for money and energy would be incredible.

200 MW for 0.75 billion dollars? You can bet the price will jump over the 1 billion $.
11 years of return? This is a scam. OMG don't be naive.


The thing with energy is - we're fucked. Plain and simple. There's no magic solution, there're no "zero pollution" sources. And we have to deal with it, avoiding to fall into scams about certain recycling that in the ends pollutes even more.

[Edited on 22-7-2011 by Endimion17]




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[*] posted on 22-7-2011 at 09:43


Quote: Originally posted by 497  

Until someone figures out a good way to build your own PV panels, all those millions of dollars per acre will keep going to supporting the monopoly.

So I'll have to humbly disagree on this one. I'd much rather spend a thousands of dollars to outfit my acre of land with my home built photobioreactor-plasma gasifier system which could provide me with heat, power, fuel for my car, and potentially a supply of highly nutritious animal/people feed, than spend a few million on solar panels and batteries that will give me a bunch of electricity that I could most likely buy for around 12 cents/kwh.. And the damn utility companies won't even buy your power for that much in many places.


You can build a few-tons-per-annum plasma gasifier coupled to a Fischer-Tropsch synthesis system and miniature refinery all for under (say) 20,000 dollars? If you're right I will gladly eat my humble pie and come back for seconds. I'll be too excited that you were right to be sad that I'm wrong. But I don't think that this is realistic in the near term.

In the long term I can picture certain advancements that might make it practical, but in the long term I also think PV and electric vehicle prices will fall considerably, so I'm still not sure biomass is the most affordable way to go.




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[*] posted on 22-7-2011 at 10:37


I though bioconversion made sense since the collectors manufacture themselves particularly if floating ponds on the ocean could be used.

Solar conversion efficiency for algae is claimed to be 7%
http://biofuelsdigest.com/bdigest/2011/02/18/peer-reviewed-a...
Although it does not say if this includes all the energy consumed to grow and process the algae.

The grass miscanthus is claimed to have the highest conversion efficiency at 1.3 to 2%.
http://abstracts.aspb.org/pb2006/public/P02/P02017.html

In terms of efficiency these compare poorly to PVs for an electric economy.

Oil produced from algae is estimated to cost $8.00/ gallon
as opposed to $4/gallon for soybean oil (seems like the algae oil should be cheaper?)
http://www1.eere.energy.gov/biomass/pdfs/algalbiofuels.pdf
as opposed to ~$2/gallon for crude oil.
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[*] posted on 22-7-2011 at 21:56


How about coal to liquids? Anyone have a figure for how much it would cost to produce straight alkanes? How about reformed to gasoline?



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[*] posted on 22-7-2011 at 23:11


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We have electric cars that work pretty well


But how long to the entire world is using them? I can't deny that eventually that may be a good solution, but right now, its not the case.

Quote:
What about the other inputs (NPK)?


Actually very small compared to food crops. And where do you think all that ash from gasifying it would go? In the case of algae, the issue is even smaller since there is plentiful municipal and agricultural wastewater to be used. In fact the savings on water treatment can be large, potentially rivaling revenue from the fuel/power produced.

Quote:
The efficiency is too low, avoiding contamination by competing organisms too hard, and the workup (for want of a better term) to extract the fuel and recycle the nutrient matter is a PITA (at least economically)


In years past these things were true. Very recently, major advances have been made. Efficiency may be "low" but it is quite a bit higher than any plant. Effective high throughput low energy methods to selectively kill unwanted organisms have been developed. And as for the the workup, yes the traditional filter/centrifuge-press/solvent extract method was quite uneconomical, but there is a new way. You continuously suck the algae slurry out of the main reactor/pond, mix it with about an equal volume of kerosene, sonicate or stir it, allow the layers to separate, return the algae slurry to the main container, and you're left with a kerosene solution of quite pure triglycerides. The triglycerides can be removed from the solvent by various means such as absorption, distillation, or membrane reverse osmosis. The algae growth is unharmed and sometimes improved by this process due to removal of trace toxins that would normally accumulate. A process like this has been recently published to produce b-carotene at about 25 times the areal productivity of the only currently commercially used process, while requiring no handling or drying of concentrated algae, only the normal culture solution and a recyclable ~$6/gal solvent is handled. As far as I can tell no energy input other than pumping, briefly sonicating and separating the resulting solvent/algae oil solution is needed. Obviously these results were not directly applicable to algae oil production, but the do at least give an idea of possible improvements that can be made by the process, not to mention improvements from genetic engineering research which seems to be just beginning.

Additionally, the ability to grow algae on the oceans surface is a great advantage.

Quote:
Nothing says 'easy and economical' like bringing plasma into it!


When you realize that bringing plasma into it means a free microwave magnetron, some welded steel and hi temp furnace cement, yes it can be easy and economical. Especially when you get a gas out that requires minimal purification, versus the extensive multistep purification methods required for making usable syngas with a conventional gasifier.

Quote:

How about coal to liquids? Anyone have a figure for how much it would cost to produce straight alkanes? How about reformed to gasoline?


Cheap and totally doable in my opinion. Do people have actual evidence that it would not be way cheaper? Probably not as profitable to those who call the shots though. Not as preferable for pollution reasons too. Still shouldn't be any dirtier than the current system, maybe somewhat better even. It is also much less doable on a small scale, due to the coal mining and pollution issues probably. Plus the fact that economies of scale seem much more potent when dealing with coal.

Quote:
You can build a few-tons-per-annum plasma gasifier coupled to a Fischer-Tropsch synthesis system and miniature refinery all for under (say) 20,000 dollars?


I really can't blame you for being skeptical. But after a bit of research (much more still needs to be done) I have come to the conclusion that it is doable. Not saying it is for everyone, because I have access to highly skilled welding (stainless steel and aluminum too) along with many other common metal fabricating tools drills, compressor, cutting tools, a small lathe, etc for free nearby, and a source of at least 6-10 horses worth of manure+bedding on site as a feedstock (which must otherwise be removed by spending money) and a small bobcat loader on site for manipulating it. Also there is larger heavy equipment such as dump trucks around for nearly free use to potentially bring in other biomass, especially the nearby available sawdust from a sawmill.

10 tons per year is less than 3 pounds per hour. That is easily within the capabilities of one or two microwave magnetrons obtained for free. The plasma gasifier is not complex, just a simple adjustable waveguide (which I admit may require much trial and error) focusing the microwaves into a small perlite+furnace cement insulated chamber into which is fed (preferably preheated) biomass along with uncondensable gases coming from the FT reactor. The ash forms an easy to handle hard vitrified slag (versus the sticky powdery shit that conventional gasifiers make). The hot output gas from the chamber would be directly and very rapidly cooled by passing through a water fed venturi. The water may contain additives to help remove inorganic contaminants, and possibly CO2. Alternatively a second CO2 scrubber may be used. Then pass the gas into a condenser to remove most of the remaining water vapor. Then a heat exchanger using waste heat from the gasifier would reheat the gas to the appropriate temperature for FT conversion, about 250-300*C IIRC. Before the FT reactor it would pass through a canister of dirt cheap ZnO to scrub remaining sulfur. The FT reactor would most likely consist of a 2-4" dia vertical pipe and smaller downcomer tube. The tube is filled with a mineral oil suspension of iron particles made by reduction of dirt cheap iron oxide. The gas will be bubbled into the bottom and and after exiting the top will be passed into a condenser. If the temperature and flow rates in the FT reactor are right, the condensed liquid will be directly usable as gasoline without further processing. The unreacted syngas along with some methane/ethane/propane will be brought back into the gasifier (or used to run an stationary IC engine for example).

Only minimal syngas purification is required because a correctly running plasma gasifier will produce only nanograms of tar per m^3 of gas, versus a conventional gasifier that is tough to get below the grams/m^3 level, thus requiring vastly more expensive and complex purification to meet the requirements of the FT catalyst.

No pressure vessels required, unless you count a moderately pressurized cooling water feed.

What part of that looks expensive to you?

10 tons per year @ 50% moisture (for horse manure+bedding mixture, but any other biomass will work as well) = about 4500 pounds of C. At even 50% efficiency of conversion that will result in about 325-375 gallons per year, equivalent to $1300-1500 at current prices, which will undoubtedly be higher by the time its running. Since I live in a cold climate, all of the waste heat from every aspect will be used for building heating and will displace a very substantial amount of fuel oil that costs $3/gal. The waste heat may be reclaimed another way in warmer climates.

Quote:
Oil produced from algae is estimated to cost $8.00/ gallon as opposed to $4/gallon for soybean oil (seems like the algae oil should be cheaper?)


The past processes used to extract that algae oil were very inefficient and uneconomical. With newer methods the price can be dropped a long way. Exactly how far, I don't know yet. Hopefully we'll find out soon. Also, ocean surface algae production has yet to be developed much, as far as I can tell. . I'm guessing that estimate was not based on ocean surface production. With additional advances that require less "sterile" conditions, the cost of growing the algae should drop too. Imagine if relatively untreated seawater (maybe brought up from deep nutrient rich waters) could be used as a growth medium? Thin polyethylene sheet is pretty damn cheap. I've seen designs (untested yet as far as I know?) that consist of almost entirely of polyethylene sheet and various sheet plastic check valves, and plastic filter membranes etc at least up to the point of processing the algae cake or possibly transporting the crude algae oil. They used wave or tidal power to do all the work for pumping fluids around. They were probably drawn up before the non destructive extraction process was known. Combining that with the wave powered pumping, etc could be very attractive. Simple electromagnetic wave powered generators could be integrated to produce power needed to do various things including separate the solvent algae oil mixture at sea. The algae farm would have the capability to inflate/deflate floats (either holding less saline water or air) to sink below the surface in the event of a storm/boat. Tanker/pipe the crude oil to shore, maybe along with pretreated wastewater out and/or treated fresh water in, you get the picture. The farms could even double as rain collectors under certain circumstances.

Hah shit, you know I bet you could even use the finished biodiesel product or a close derivative of it as the solvent!

Yes there could be regulatory barriers. I'm pretty sure they could be dealt with, with proper design, and regulation in a responsible manner. I seriously doubt anything nearly as catastrophic as a large oil spill could occur, barring the release of an invasive genetically modified algae. Obviously serious steps need to be taken to prevent that from happening.

It seems to me that best way for truly rapid innovation to occur in an environment where very very powerful people want slow it down is to take it out of their hands. Out of the secrecy of the corporate and university labs that in one way or another are more concerned with keeping the oil company's good graces or getting rich of it. The only way for that to happen is to develop a process that is simple and small scale enough to be done by the individual. This is a challenging task, but one I believe may be vital to our futures if we want to maintain/improve our standards of living. Plant crop biodiesel and fermentation routes are a good start, but they're not going to go far enough for one reason or another. Some solar and hydrokinetic based methods like interesting and maybe eventually viable, but they seem much more thoroughly studied that algae based methods.

Hopefully now you can understand why I am not basing my statements on the pure large scale economics that many others rely on. Sorry for writing so much..

[Edited on 23-7-2011 by 497]
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[*] posted on 23-7-2011 at 10:11


Quote:
10 tons per year is less than 3 pounds per hour. That is easily within the capabilities of one or two microwave magnetrons obtained for free. The plasma gasifier is not complex, just a simple adjustable waveguide (which I admit may require much trial and error) focusing the microwaves into a small perlite+furnace cement insulated chamber into which is fed (preferably preheated) biomass along with uncondensable gases coming from the FT reactor. The ash forms an easy to handle hard vitrified slag (versus the sticky powdery shit that conventional gasifiers make). The hot output gas from the chamber would be directly and very rapidly cooled by passing through a water fed venturi. The water may contain additives to help remove inorganic contaminants, and possibly CO2. Alternatively a second CO2 scrubber may be used. Then pass the gas into a condenser to remove most of the remaining water vapor. Then a heat exchanger using waste heat from the gasifier would reheat the gas to the appropriate temperature for FT conversion, about 250-300*C IIRC. Before the FT reactor it would pass through a canister of dirt cheap ZnO to scrub remaining sulfur. The FT reactor would most likely consist of a 2-4" dia vertical pipe and smaller downcomer tube. The tube is filled with a mineral oil suspension of iron particles made by reduction of dirt cheap iron oxide. The gas will be bubbled into the bottom and and after exiting the top will be passed into a condenser. If the temperature and flow rates in the FT reactor are right, the condensed liquid will be directly usable as gasoline without further processing. The unreacted syngas along with some methane/ethane/propane will be brought back into the gasifier (or used to run an stationary IC engine for example).

Only minimal syngas purification is required because a correctly running plasma gasifier will produce only nanograms of tar per m^3 of gas, versus a conventional gasifier that is tough to get below the grams/m^3 level, thus requiring vastly more expensive and complex purification to meet the requirements of the FT catalyst.

No pressure vessels required, unless you count a moderately pressurized cooling water feed.

What part of that looks expensive to you?


If you want to spend no more than 3 hours per day operating the system, and it doesn't look like it can operate unattended for long, you need to process more like 20 pounds per hour (figure some time is spent on maintenance).

My skepticism is mostly a matter of scale. If you proposed to do bench-scale demonstrations with grams of material for any of the stages proposed, I wouldn't think you were unreasonable. To do it on a scale of even a few tons per year, with only one operator working a few hours a day, and with no online analysis to check product output or syngas H2:CO ratios, it seems that there are a lot of ways it could fail to meet expectations. But if you pull it it off, I will be very impressed.

[Edited on 7-23-2011 by Polverone]




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[*] posted on 23-7-2011 at 11:03


I've read quite a few papers where their bench scale model was in fact using pounds per hour, sometimes more than 3 even. The apparatus can afford to be pretty small when the residence time is very small.

I'm not really sure what you think the continuous attention would be needed for.. A hopper and auger feed are not a tough thing to accomplish and automate. Neither is an slag auger. Thermostatic control of heat exchangers and cooling water pumps is pretty doable. Manual feed hopper refilling, slag bin emptying, ZnO canister changing, and possibly partial catalyst exchanging can all be done on a weekly basis. I don't see why online analysis of product output and uncondensable gas output is that tough. Sure H2:CO ratios are harder to analyze, but they're not really critical for a high temperature FT reactor from what I've read. The unreacted gas will be utilized too. If the ratio was consistently low (the most likely scenario) it wouldn't be tough to add an iron catalyzed water gas shift reactor to improve it. I won't be the only one around to operate it either, especially after the initial period of optimizing its settings.

I think people underestimate how well these processes work on a small scale because that's just not the way they're ever run. I don't think it means they can't be done. How much effort do you think has ever even been put into scaling them down? In fact I know that some processes the FT reaction for example actually worked better on a bench scale and more problems were encountered in scale up.
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[*] posted on 23-7-2011 at 14:18


http://www.peat.com/pdtr-100.html


Here is a system that you can buy (130lbs/hour). It is targeted at disposing of
medical waste using a plasma torch. It does not appear to generate any net
power (130kW + CH4 + water + N2 in, about 25kW out).

Some of these systems do claim to generate net power, but it must be highly
dependent on what you feed it. For something like rubber tires yes. For damp
biomass I don't see how it could generate power given that you can't
burn the stuff.

It seems like a big problem would be that a large amount of power must
be cycled back to feed the plasma torch. Converting the syngas to electrical
can only be done at low efficiency without multi stage gas/steam turbines.


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[*] posted on 24-7-2011 at 01:16


Quote:
Some of these systems do claim to generate net power, but it must be highly dependent on what you feed it. For something like rubber tires yes. For damp biomass I don't see how it could generate power given that you can't
burn the stuff.


Microwave induced plasma tends to be can be considerably more efficient. Here is an example. On that page they also adress the water content issue:

Quote:
“One of the main differentiating aspects of our technology compared to plasma arc or torch technologies is that it utilizes water contained inside the waste, where the water actually becomes part of the chemical reaction to produce the syngas,” Tijerina said. “We can bring damp waste into our reactor and in some cases we might even inject water to increase the conversion yield of the waste.”


It seems like you guys are using a lot of information about something conventional to judge something that is unconventional. Not surprising since since it is the widely available and well known information..

Woo 497 posts!

[Edited on 24-7-2011 by 497]
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[*] posted on 24-7-2011 at 06:30


Quote: Originally posted by 497  
What part of that looks expensive to you?
The high-nickel alloys needed to deal with hydrogen embrittlement. They're not needed to make a short-lifetime prototype, though.
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[*] posted on 24-7-2011 at 13:04


Considering the system is not under pressure, I find it unlikely that 304 stainless would be weakened enough to fail. Very low loads are involved. From what I understand the parts of the system that were maintained at higher temperatures would not be nearly as susceptible. Further analysis is surely waranted. Even if more expensive allows were required, on a small scale I doubt would be anywhere near prohibitively expensive. Especially if copper or nonmetallic parts can be used for some purposes. According to this reference:

Quote:
Historically, carbon steel or stainless steel has been used to transport hydrogen. Gray, ductile, or cast iron and nickel steels have been used but are not considered suitable for highpressure hydrogen transmission (Mohipour et al. 2004). Austenitic stainless steels, aluminum (including alloys), copper (including alloys), and titanium (including alloys) are generally applicable for most hydrogen service applications. High-strength steels (above 100 ksi) are more susceptible to hydrogen embrittlement, so the use of thicker, low-strength steels is sometimes recommended for hydrogen pipelines. Polymer/fiberglass-reinforced pipes have been used in specific applications such as for in-plant piping at moderate temperatures.

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[*] posted on 26-7-2011 at 08:46


Having done the algae experiment myself a few years ago. Its not very efficient. I grew a large batch of algae, in artificial conditions, high light levels, high nutrients and then extracted the lipids with Heptane. For the amount of time it took and the volume of algae the yield was pretty pitiful. To then use this in an inefficient IC engine is madness. Electric cars are now in mass production, and i believe are the future.
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[*] posted on 26-7-2011 at 11:06


I remember reading in a study that the amount of lipids produced is higher when there is insufficient nitrogen.

There was a DOE study on algae farming back in the 80s
which is described in the following report.

http://www.nrel.gov/docs/legosti/fy98/24190.pdf
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[*] posted on 26-7-2011 at 22:49




Gregxy, that is a really interesting report.

I am surprised by the response to this thread. It seems a lot of people on sciencemadness are following renewable energy sources, maybe a sticky about green/alternative energy sources would be a good idea? Not only would it be fun to read, it would be nice to have a consolidated source of information about emerging energy technologies.

...just a thought...




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[*] posted on 3-8-2011 at 07:30


After reading a lot about alternative energy and energy conservation, I have to agree that cutting consumption is a good start (insulation, higher fuel economy, more efficient furnaces, less waste of power on lighting, computers left on all night, other obvious waste), then simple things like solar thermal hot water, geothermal heat pumps, LED lights, hybrids, etc are a good second step. And lastly, alternative energy (PV, windmills, tidal systems, biomass) and all of the fancy stuff that is expensive and hard to implement. If every house in America was just insulated, had a moderately efficient HVAC system installed, used Energy star appliances, low power lighting, got one more energy efficient vehicle, and some small amount of common sense was used, we could cut energy use in America by 30-50%, with almost no change in living standards. In fact, several of my friends have done it, and saved money within a short time, through insulation, geothermal heat pumps, better hot water systems (the new heat pump designs work well), and other small changes. Most of them will have a payback of 3-5 years at most.

Solar PV works best in places with 1) high electric costs, 2) good sun (southwest US, Hawaii, Florida) and 3) good tax breaks. So places like the west coast of the big island of Hawaii are great choices, due to high electric rates, poor grid and high costs of wiring infrastructure, and year round sunshine. Southern Cal. also is a quick financial payback.

Some of the best tax breaks in places like NJ where the amount of sunlight is not optimal, seem like a waste, especially given that solar panel production is one of the limiting factors in PV usage. I would rather see solar PV used first in places like Arizona, NM, Cal, Colorado, Texas, etc, where they give the most return of energy. As long as they are under 10% of the total energy use, the grid can buffer their production as the sun rises and sets and clouds move.

As for biofuels, I see them as a way to stretch our current petrofuels, not a replacement. if we could find a way to provide a crop that would generate 4 times more oil per acre than soybeans (about 10% usable weight of the crop is oil), then we could make a serious dent in the amount of diesel used, and eliminate the need for imported oil in that fuel sector. Since other crops in tropical areas provide way more oil per acre, I think the problem is a solvable one. Combine that with more productive ethanol production (we need to improve the energy input:output ratio to about 1:3 or 1:4 to be reasonable) and other ways to produce liquid fuels, and we can reduce our oil imports by a sizable margin. Coal to liquid fuels/gasoline has been done for years, is still
done by Eastman Kodak and SASOL today, and is financially reasonable at the current oil prices. That will eventually become another source of fuels.

And lastly, nuclear will have to continue to be part of the energy use on earth if the population keeps growing, as no other energy source is so scalable. I think the use of smaller, modular reactors, used in parallel, might be one answer, almost like a bunch of nuclear submarine sized reactors all put on the grid. In fact, those would be great , as they could be designed to work underwater in case of disaster. :-)

So our energy problems come about from several sources: growing population, higher standard of living world-wide, more dependence on energy intensive processed for raw materials, wide use of computers, electronics, cars and refrigeration, global warming potential, peak oil production, pollution, nuclear woes/fears, NIMBYism, ecological desires not to damn every river on earth, soccer moms driving 3 ton SUVs, etc.

So we need to work on parallel approaches to the solution, as I don't see any one answer to the problem. But if everyone even did the options that have short paybacks, and built new homes to higher energy standards, the problem would be reduced substantially. Habitat for Humanity here builds only super efficient homes, and the building costs only rise by a small amount, in part due to the ridiculously small HVAC systems needed, and they average $40 per month for all of the heating, cooling and hot water. So it is easy to do, and affordable.

Bob
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[*] posted on 9-8-2011 at 05:02


The culture of consumption is far too entrenched (and spreading) to allow much of the above to happen in a timely manner. To me, the possible outcomes look to be either the system runs itself into the ground and needed lowering of (percieved) standard of living is forced by the resulting catestrophic global reprocussions, or a profitable solution that maintains the general status quo is developed (with extra green colored packaging for piece of mind.)
If you ignore the irrationality and greed of humans there is a plethora of suitable alternative energy sources. But how many will work in the real world?
When so much human energy/will is devoted toward extracting money from their peers, perceptions become prioritized much more than efficiency, practicality or sustainability. The magnitude of this is still hitting me as I spend time in urban areas.
Efficiency and percieved socioeconomic status do not mix (past buying organic food and hybrid cars anyway.) To change this would require a direct reversal of the philosophies of the people who have the least to gain, the most to lose, and ever increasing power to manipulate the public's perceptions. Not likely to occur by choice, but one way or another it will happen. We can only hope for the ability to choose how..

As for nuclear, why the hell can't it be switched over to a gas cooled pebble bed style reactors? They seem so much more trustworthy with the bonus of being much harder to weaponize.. With recent events I really can't blame people for being wary though. I doubt it will ever be much of a solution to our energy problems.
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[*] posted on 17-8-2011 at 21:01


Consider that the sun is a large fusion energy source at an ideal distance away from the earth...

A very large portion of the energy we use on earth is from the sun already. Granted some of it like from oil has been captured by plants into chemical bonds, eaten by animals, and so on, decomposed and reformed, then drilled, pumped and refined... Oil is solar energy in one chemical form. With so many steps its not as efficient as solar panels or solar thermal uses, etc... But its easy at the moment. Any time someone says that oil is more efficient than solar photovoltaic... they don't get it. They are looking at oil as if it has always been here without thinking of how much energy it took to create it.

We think of solar energy as a pipe dream because we have been living off the oil from so long ago. We just pump it out, refine it, and burn it. We only see half of its life. You can think of the oil reserves on earth as a sort of rechargeable massive battery which was very inefficiently charged up by solar energy long ago... and which we are beyond the half-way point of draining, using very inefficient machines. A capacitor may be more accurate since we have been draining it so quickly... If we never had the oil to use, we would most certainly be using solar panels, solar thermal, nuclear, wind, etc... And these types of threads would not exist. If life would be around at all.

Solar voltaic, solar thermal, etc... are solar energy like oil, but more direct and more efficient. As are grown crops. The food you eat (hopefully) is solar energy. Calling solar energy a pipe dream is naive. Its everywhere. "You are made of star stuff (RIP Carl Sagan)." Calling the corpolitical consumer mindset sustainable... now that is more like a pipe dream.

These more readily renewable sources of energy are what we should have been using for a very long time... Why haven't we been using them in greater amounts? With more efficient machines? Corporations, government, politics. Money really. All sorts of these alternative energy sources and more efficient things have been known for a very very long time... and not implemented for profit reasons. IE Nickel-iron batteries and electric cars we could of had around the time of the model-T... Why weren't they? Because some companies wanted to sell lots of lead-acid batteries with shorter cycle lifes and gasoline because thats where there investments were. There is less profit in a battery you only need to buy once. Large cars and trucks we don't need to buy, but buy anyways because the media tells us to and hey, its cool. We use uranium nuclear reactors because of the plutonium byproduct which the military wants and because the companies were fully invested in uranium at the time... Never mind that thorium is dirt cheap, has by products with shorter half-lifes, and doesn't have a plutonium byproduct as an incentive to stockpile nuclear weapons. And we can't forget that the liquid thorium fluoride reactors are inherently safer than any uranium reactors since they don't depend on computers to shut them off.

Granted there are geothermal, tidal, nuclear, etc... sources of energy which are not necessarily 100% completely from the sun or the gases which coalesced to form our solar system. But in a way they are made possible by the sun none the less...

BTW, next energy era is likely to be the thorium era... then alternative energies or fusion depending on our technological and societal successes or failures.




So many ideas... too few dealing with chemistry.
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