Questions about a Hydrogen Economy; Scientific American

[Ivan Seeking]

The key issue with electrolysis is not that a new source of energy is found, it is that sources once limited to the production of electricity, such as fission or [hopefully] fusion power, in addition to solar, wind, and hydro, can now be used via H2 as a fuel source for nearly any application. This, in addition to the many non-electrolytic approaches to H2 production broadly diversifies the energy base for transportation.

 

[zoobyshoe]

The key issue with electrolysis is not that a new source of energy is found, it is that sources once limited to the production of electricity, such as fission or [hopefully] fusion power, in addition to solar, wind, and hydro, can now be used via H2 as a fuel source for nearly any application. This, in addition to the many non-electrolytic approaches to H2 production broadly diversifies the energy base for transportation.

This may be true, but hydrogen has no appeal to me on this basis. The ability to broaden nuclear power to run cars, in fact, bothers me. I like hydrogen because it can be generated with solar and wind and then stored, and because when you burn it all that results is water.

 

[Ivan Seeking]

ssssshhhhhh. It is still a nice carrot for the pro-nuclear crowd.

Even on fission my mind is still open.[edit: hey, that's kind of funny] We have a family member who is a retired, high ranking [GE] nuclear engineer who remains active in the industry in various ways. He is quite sold on fast flux reactor technologies. Also, methods that make melt down impossible are now explored - such as by using ceramic encapsulated Pu beads for a core. I have been anti-nuclear for about twenty five years now, but on this point of new technologies I try to remain open.

Fusion may be great! We will just have to wait and see.

 

[zoobyshoe]

ssssshhhhhh. It is still a nice carrot for the pro-nuclear crowd.

_{Whoops! Sorry!}

Also, methods that make melt down impossible are now explored - such as by using ceramic encapsulated Pu beads for a core. I have been anti-nuclear for about twenty five years now, but on this point of new technologies I try to remain open.

I thought I had heard that this non-meltdownable thing was already up and running in Canada.

Regardless, I'm very much less concerned about meltdowns than about disposal of the waste.

 

[Ivan Seeking]

Regardless, I'm very much less concerned about meltdowns than about disposal of the waste.

This is my main objection as well. On this point I am told that the French do a pretty good job of recycling. Still, I am no advocate for nuclear power. I really wish I could be. High hopes for fusion still.

Tokamak, Tokamak, Tokamak!

 

[Janitor]

Elaborating on the energy requirement issue-

I found a table which said bond energies in kJ/mol are:

H-H 436
O=O 499
O-H 463

So in order to approximate the energy requirements for 2 H20 --> 2H2 + O2, figure 4*463 to tear apart two water molecules, then get back 2*436 for the recombining hydrogen atoms plus 499 for the recombining oxygen atoms. The net energy required is thus 1,852 - 872 - 499 = 481. But a single water molecule would only require half that, 240.5 kJ/mol, to be split. This number is between the two numbers already given in this thread. This calculation ignores subtleties, such as that the O-H bond energy listed above would not apply exactly when the O already has another hydrogen attached to it.

 

[Ivan Seeking]

According to the Scientific American article, in practice, electrolytic production of H2 results in a 22% efficiency- as required to create the H2. H2 production by steam reforming techniques can be over 60% efficient.

This steam reforming option [cracking natural gas with steam], when combined with hydrogen fuel cells, is claimed to yield the best source-to-wheels effiiency of all options - about 22%. This is better than gasoline internal combustion, diesel combustion, compressed natural gas, compressed H2 for combustion, gasoline hybrids, diesel hybrids, gasoline fuel cell, methanol fuel cell, ethanol fuel cell, or H2 by electric; which all land around 12% to 16% for a source-to-wheels efficiency.

 

[Ivan Seeking]

Note that this does not address electrolysis combined with catalytic materials, or some of the more advanced techniques being explored.

 

[zoobyshoe]

In the other thread I posted about the process of dissociating water into hydrogen and oxygen by high temperature created with a parabolic mirror from sunlight. Efficiency is moot with this, since the energy is free. The problem, they say, is developing materials for the equipment that can withstand the high temperatures.

Water spontaneously dissociates at 2,730C (4,946F). This isn't that hard to achieve with a parabolic reflector: it's a matter of size. In the 1700s they ground a 20ft dia glass lens that would instantaneously vaporize stones placed at the focal point. So, I think a mirror about that size is probably what we're talking about to dissociate water by heat.

The hydrogen and oxygen would be lead to a water quench and then separated by gravity. I'm very fond of this idea.

 

[Ivan Seeking]

Not to be negative since work is definitely going on here, but efficiency is a consideration as a function of the cost of production per square foot of light incident area, the total mass rate of production of H2 as a function of this area, and the maintenance and lifespan of the system. This all affects the final cost of energy per watt, to the consumer - in whatever form it may take. So, from what I have seen and only as a hypothetical example, at some point it might make more sense to fill the Mojave Desert with solar panels and wind generators as opposed to light focusing systems. Likewise, focusing technologies may be more practical in Death Valley.

The cost of photoelectric panels is supposed to drop precipitously as production techniques improve. I have seen some really encouraging reports in the tech news in recent years.

On the high temp, focused light side, I have seen some neat work being done. I think that that liquid lithium is used in one system to generate steam.

 

[Ivan Seeking]

Something that I am just learning about now...with reforming technologies in mind.

Methane Hydrates -
The Gas Resource of the Future...

...Worldwide, estimates of the natural gas potential of methane hydrates approach 400 million trillion cubic feet -- a staggering figure compared to the 5,000 trillion cubic feet that make up the world's currently known gas reserves. [continued]

http://www.fe.doe.gov/programs/oilgas/hydrates/

 

[BCRion]

This is my main objection as well. On this point I am told that the French do a pretty good job of recycling. Still, I am no advocate for nuclear power. I really wish I could be. High hopes for fusion still.

Tokamak, Tokamak, Tokamak!

There are some interesting technologies using transmutation to convert the particularly bad fission products into more stable products that are much easier to handle and have less disposal time. The advancements in the past five years have been quite encouraging, although the economics still need work.

Keep in mind that only 1-2% of spent fuel is actually fission product waste. The rest is Plutonium and other Actinites (2%) and good old U-238 (96%). This is potentially a valuable fuel in the future.

As far as the issue of waste disposal, at least it can theoretically be disposed of. Fossil fuels really do not give us this option. There is simply way too much waste. It's a trade off. Everything has costs.

DT fusion has serious materials problems to commercialization. The neutron damage to the reactor vessel could prove to be uneconomic as it would require constant replacement. Also, Tritium can be some pretty bad stuff especially in the GigaCurie quantities. Perhaps D-3He fusion would be more economic. However, we would need to go to the moon for that. 3He-3He would be great...nuclear power with no nuclear waste.

 

[Cliff_J]

Our tranmission grid is in a state of affairs where it needs hundreds of billions to get it fixed? Wasn't this deregulated just a few years back in the 80s? The History channel program "Modern Marvels" on the power grid mostly focused on challenges with power generation and glossed over the issues with transmission. They did cover the NY blackout in the late 60s, the CA issues, and the NE blackout and its roots. They talked about the challenges of monitoring transmissions as being the 'key' to avoiding problems in the future. Is this what you're referring to, or to the actual transmission lines and routing, or something more substantial like redundant lines to mitigate single-point failures?

The 4 trillion dollar PV farm is to me like asking if we could scrounge auto salvage yards and pick up old motors with their generators and make a megawatt powerplant. Possible, but horribly inefficient. But I find it facisnating that we could farm out a few sq miles of dessert in the SW and produce enough energy to effectively 'run' the country. From a producers point of view, how long before the we could get the technology to the point where the yield from H2 production could exceed the profit from growing crops? Even better is using land not currently in a production capacity and without much environmental impact. The Marlborlo man on horseback image replaced with an image of a PhD drinking Starbucks riding an electric scooter while making sure the array is fully functional.

Personally I think it makes more sense to keep the costs centralized because even at 3x the capacity the expense should be fractional (large fixed small variable costs model) or as a worst case scenario exponential, but regardless far easier to implement first. Similar to Arnold's ambitious "...build it and they will come..." proposals. Hopefully with better success than GM had with their EV1 car. $400 a year doesn't really pay for the cost of the fuel cell in the near future, and a big set of government subsidies on cars that will depreciate quickly seems wasteful instead of infrastructure investments that the general public could access after a retrofit to their existing autos.

Lots of interesting things in store though, hopefully sooner than later. I just want to setup a small PV cell hooked to an electrolysis still, and buy another lawn mower to attempt a H2 conversion on a little Briggs & Stratton engine. Low cost, low risk...maybe next year.

Cliff

 

[Ivan Seeking]

One thing that scares me a bit is the idea that land use for food might come into competition with land use for energy, but typically it seems that solar is best where food does not grow well, such as in deserts, and wind generators do not really compete for land directly as do PV panels. Biomass need not be anything useful, and coal is coal.

As for the chicken and the egg problem, what I see as one possibility is that in addition to small test programs, industry will apply H2 technologies in such a way that small test communities will emerge. For example, let’s imagine that Weyerhaeuser discovers that they can produce H2 as a byproduct of some process used in the production of paper. All of the company cars could then be converted to run using H2 as a fuel source. I have seen this done for years in other applications. My uncle worked for Richfield [now ARCO] for forty years. He drove a natural gas powered company vehicle for as long as I can remember.

So, along with engineered test communities that are created through various means, such as through research, private funding, and government test programs, my hope is that industry might lead the charge through the practical application of existing technologies. In some cases at least, simply adding a few steps to an existing process can yield an untapped supply of energy that was sometimes even lost as waste. Also, I would assume that certain large population centers that have an H2 advantage, say for example Phoenix or Vegas [with PV in mind], will see the economic justification for H2 fueling stations and local H2 production before most other places. Maybe we will even see auto dealers selling H2 to get things started.

As with anything new, there will have to be a bleeding edge.

 

[Ivan Seeking]

Again, on a related note

Far more natural gas is sequestered on the seafloor—or leaking from it—than can be drilled from all the existing wells on Earth. The ocean floor is teeming with methane, the same gas that fuels our homes and our economy.

In more and more locations throughout the world’s oceans, scientists are finding methane percolating through the seafloor, bubbling into the water column, collecting in pockets beneath seafloor sediments, or solidifying in a peculiar ice-like substance, called methane hydrates, in the cold, pressurized depths of the ocean.

Massive deposits of methane hydrates could prove to be abundant reservoirs of fuel. But in the past, these massive storehouses of methane also may have “thawed” suddenly and catastrophically, releasing great quantities of climate-altering greenhouse gas back into the atmosphere [continued]

http://oceanusmag.whoi.edu/v42n2/whelan.html

Also:

METHANE FUEL PUTS PLANET IN DANGER: Scientistswarn of global warming catastrophe in hunt for new energy. IT HAS been hailed as the fuel of the future, a source of energy that could powerour planet throughout the next century. But now scientists have warned thatthe world’s largest untapped energy reserves—huge deposits of methane gaslocked under the ocean floor–could trigger a catastrophic bout of atmosphericwarming that would cause global devastation. [continued]

http://216.239.51.104/search?q=cach...thane.pdf+Worlds+known+methane+deposits&hl=en

 

[Ivan Seeking]

For a list of who’s who in Hydrates?

Who Studies Gas Hydrate?
http://woodshole.er.usgs.gov/project-pages/hydrates/who.html

 

[russ_watters]

I'm not sure about methane. Its certainly preferable to other forms of hydrocarbons, but it is still a hydrocarbon. Whether you convert it to hydrogen to burn in a hydrogen fuel cell, use it as methane in a fuel cell, or burn it, the chemical reaction is about the same and as a result, the pollution is about the same.

 

[Ivan Seeking]

On this point it is argued that clean, carbon based technologies are practical on a large scale but not on a small scale; such as on a car by car basis. It is within our reach, some say, to build large, clean, H2 reforming plants that use carbon based fuels as the primary energy source. This includes reforming coal for H2. In the most ideal sense this is a transitional technology that addresses the practical concerns about an energy base. Also, Methane -> H2 -> Fuel cell is now the most efficient option from source to wheels. In principle, if we could convert instantly to fossil fuel fired H2 production from methane, and then if we used this H2 in fuel cell powered cars, we would instantly require about 2% less energy in total - according the Sci American data [Edit: note that I had said 5%, the correct number is about 2.5%+-0.5% from what I can see]. Allegedly this includes the efficiency of production of the H2 as well as the efficiency of the auto; from energy source to fuel cell to wheels.

Note also that the total of greenhouse emissions through this channel is about 140 grams of gh gas per mile. This compares to 380 grams per mile for autos burning fossil fuels directly. Apparently this does not assume clean, carbon based H2 production, so this might be a worst case only estimate - i.e. if this happened today with established technologies.

BTW, I'm not convinced that this is the best path but this seems to be the state of the consensus for now. I still think we may ignore huge energy losses in the production of fuel cells and in the efficiency of the fuel chain for gasoline and diesel. I will provide related information as I'm able. It also possible, God forbid, that my previous evaluation of this issue is wrong :surprise: but I'm not buying into that just yet.

Minor edits for clarity.

I should add that the article stresses that this issue is very complex.

 

[Ivan Seeking]

The NHA's Hydrogen Commercialization Plan
http://www.hydrogenus.com/commercializationplan.asp

A sustainable hydrogen energy industry - an energy system based upon the extensive use of hydrogen as an energy storage and transportation medium - must be established if an environmentally and economically sustainable world is to be left to our children and grandchildren. Few doubt that the hydrogen energy industry will eventually evolve. Many debate the timing of such a development. Only by defining the nature of a future hydrogen energy system, by identifying the path to such a system, and by actively taking the first steps along that path will we, as a world society, achieve that goal in time to avoid serious environmental and economic disruptions.

The National Hydrogen Association, in conjunction with the U.S. Department of Energy, is embarking upon the process of defining the path and beginning the journey. The NHA believes that this journey will only be successful by working together in an industry/government partnership. [continued]

The NHA's Hydrogen Implementation Plan
http://www.hydrogenus.com/implementationplan.asp

The 1999 Implementation Plan provides a path to achieve the near-term goals of the NHA’s Hydrogen Commercialization Plan.

The Hydrogen Commercialization Plan, as first drafted in 1996, challenged industry and others to show their commitment to making hydrogen a major “energy carrier” in three major markets — autos, buses, and power generation. Industry, government, and other sectors are responding to this challenge through the development of hydrogen products with aggressive milestones and field tests. The Implementation Plan lays out a strategy which, if followed, would achieve the near-term goals of the Hydrogen Commercialization Plan. Achievement of these goals will also establish niche markets or a market presence important for hydrogen energy systems. [continued]

 

[Ivan Seeking]

I should have included this in the quote from the Implementation Plan above.

Roles:

...Academia

The key role of academia is to increase public awareness and acceptance through education of high school and college students about hydrogen systems, and informing the public of the true cost of fossil fuels, far more than simply the price at the pumps.

In addition, academia can solve long-term technical issues for future generations through research and development. This may be accomplished through government and industry support.

 

[russ_watters]

On this point it is argued that clean, carbon based technologies are practical on a large scale but not on a small scale.

Economies of scale - yes, that's certainly a possibility. But the cynic in me says that its currently possible with existing coal-fired plants too - and it isn't beng done. A simple law to require it could vastly reduce the US's pollution output in a very short amount of time (and add maybe 1% to our energy costs). This can/needs to be done independent of (and easier than) converting to a hydrogen economy.

Also, Methane -> H2 -> Fuel cell is now the most efficient option from source to wheels. In principle, if we could convert instantly to fossil fuel fired H2 production from methane, and then if we used this H2 in fuel cell powered cars, we would instantly require about 2% less energy in total - according the Sci American data [Edit: note that I had said 5%, the correct number is about 2.5%+-0.5% from what I can see]. Allegedly this includes the efficiency of production of the H2 as well as the efficiency of the auto; from energy source to fuel cell to wheels.

Not sure about "well-to-wheel" efficiency. I've heard it before and I don't see the relevance because its generally used in apples to oranges comparisons. IE, what is the well-to-wheel efficiency of solar-powered electrolysis->hydrogen fuel cell? I think the more important number would be $$$$ per mile.

Also, what's 2%? Half a terawatt (from all sources - electric power, gas heat, cars)? At face value, that's a ton of energy, but our usage is growing by at least that that rate every year.

 

[Ivan Seeking]

Economies of scale - yes, that's certainly a possibility. But the cynic in me says that its currently possible with existing coal-fired plants too - and it isn't beng done. A simple law to require it could vastly reduce the US's pollution output in a very short amount of time (and add maybe 1% to our energy costs). This can/needs to be done independent of (and easier than) converting to a hydrogen economy.

I completely agree.

Not sure about "well-to-wheel" efficiency. I've heard it before and I don't see the relevance because its generally used in apples to oranges comparisons. IE, what is the well-to-wheel efficiency of solar-powered electrolysis->hydrogen fuel cell? I think the more important number would be $$$$ per mile.

The two are unavoidably connected. I think a key concept here is that certain "energy" solutions appear to be more beneficial than in fact. The "well-to-wheels" efficiency is merely an attempt to quantify the complete energy costs for a given technology.

Consider solar panels [edit: ie. photovoltaic]. Solar technology promises to get cheap very quickly, but until now it is quite possible that the complete energy costs to produce the panels was greater than the energy recovered over the life of the panel. If we consider the entire process from the mining, transport, and smelting or raw material, material processing and handling, right through to the actual production of the panel, a lot of energy is spent per square inch of the final product. Many hidden fossil fuel costs contaminate this so called "clean" technology. So, this brings to light the concept the "fossil fuel [energy] battery". Fossil fuel energy invested in the panel gets returned as the panel is used. So for some time - presumably the life of the panel until now - this is really fossil fuel power, just delayed.

The same argument applies to wind powered generators. In this context at least I think the need to quantify all of this becomes obvious. Also, it should be possible to gauge the energy cost of a technology wrt another by looking at the cost per KwH over the lifespan of the application. How closely this actually tracks, I don't know. I do know that an economic comparison of solar or wind to standard public utilities is just now showing the economic justification to change for some select areas. In most cases, putting solar panels on your home was a losing proposition.

Also, what's 2%? Half a terawatt (from all sources - electric power, gas heat, cars)? At face value, that's a ton of energy, but our usage is growing by at least that that rate every year.

To me the significance is that we have passed the break even point. I would expect that for the first time, the economy of some energy options finally can compete with fossil fuels. This strikes me as being fairly significant. Also, we get a 63% reduction in ghg emissions.

 

[zoobyshoe]

What do you think of this one? This one sounds great to me. Imput:solar heat. Output: Hydrogen. Everything else is recycled over and over. Clean. Cheap.

"Multi-step metal oxide cycles for solar-thermal water splitting"
**** The goal of my research is the discovery of a feasible means of transforming solar energy into chemical energy in the form of hydrogen, thus uncovering a renewable, sustainable pathway to the "hydrogen economy."* The pathway I am focusing on is a solar thermal water splitting cycle utilizing metal oxides.* A metal oxide (e.g. ZnO) is passed through a solar thermal reactor and undergoes a thermal dissociation reaction.* The reduced metal or metal oxide is collected and the oxygen gas is allowed to escape.* The reduced metal or metal oxide can then be fed to another reactor containing water, where an oxidation reaction occurs, splitting the water, releasing hydrogen, and forming once again the original metal oxide.* This metal oxide can be recycled to the solar reactor, forming an overall cycle where the only feed is water and the only products are hydrogen and oxygen.
The solar thermal dissociation is performed in a high flux solar furnace, where radiant energy from the sun is concentrated up to 10,000 times by parabolic mirrors and focused on a chemical reactor.* With this configuration, temperatures up to 3000 K and heating rates of 1,000,000 K/s can be achieved, providing access to reaction regimes not available to any other renewable energy technology.
The cycle currently of most interest to me utilizes zinc oxide (ZnO) as the metal oxide energy carrier.* ZnO is used in the thermal dissociation step, and thermodynamic simulations suggest that it should react to completion between 2100 K and 2300 K.* The water splitting step employs the reduced Zn metal, and will react exothermally around 700 K.* Due to the exothermic nature of this reaction, it can be run autothermally.* My current work with the ZnO cycle focuses on determining the intrinsic kinetics of the ZnO dissociation reaction and attempting to engineer methods to prevent recombination of the Zn and oxygen products in the cooling stage of the reactor.
Chris Perkins at TEAM WEIMER
Address:http://www.colorado.edu/che/TeamWeimer/perkins.htm Changed:6:21 PM on Thursday, June 17, 2004******************************************* ***
*
******* ****

 

[zoobyshoe]

Others working on the same process:
ETH - Renewable Energy Carriers

Address:http://www.pre.ethz.ch/cgi-bin/main.pl?research?project6

Solar Production Of Zinc: Concentrated solar energy is used as the source of process heat for the dissociation of zinc oxide
Address:http://solar.web.psi.ch/daten/projekt/zno/roca/roca.html Changed:6:37 PM on Thursday, June 17, 2004

Mechanical Engineering "Power & Energy," March 2004 -- "Packaging Sunlight," Feature Article
Address:http://www.memagazine.org/pemar04/pckgsun/pckgsun.html Changed:12:46 PM on Monday, March 8, 2004

 

[Ivan Seeking]

I would say this approach looks really promising. Here is some more related information. It seems that there are many different reactions explored here.

In the course of the past several decades, many thermochemical cycles have been devised for production of hydrogen from water. It has been shown that thermochemical water splitting cycles (TCWSCs) have potential to deliver overall system efficiencies in excess of 40%...

i. Bunsen reaction involving iodine and thermal
decomposition of HI. As depicted in Figure 1, in
addition to the sulfuric acid decomposition step, the
following reactions are employed:
SO2 + I2 + 2H2O = 2HI(aq) + H2SO4 (aq)
followed by thermal decomposition of
hydroiodic acid:

2HI = H2 + I2
This is the General Atomics process with the
revised cycle having improved energetics and an
overall efficiency of about 50%. A variation of this
TCWSC is the so-called Bowman-Westinghouse
cycle that employs a reaction involving bromine
(instead of iodine) and electrolysis of hydrobromic
acid (in lieu of thermal decomposition of HI). The
electrolytic decomposition of HBr requires a cell
voltage of about 0.80 V (for acid concentration of 75
wt%...

University of Tokyo). The UT-3 process is one of the
most studied thermochemical hydrogen production
cycles in the world. It should be noted that the UT-3
process is being developed for coupling to nuclear
power reactors. The reported cycle efficiency is in
the range of 40 to 50%. The cycle involves the
following four gas-solid reactions:
CaBr2 (s) + H2O (g) = CaO (s) + 2HBr (g)(1170 K)(1)
CaO (s) + Br2 (g) = CaBr2 (s) + ½ O2 (g)(700 K) (2)
Fe3O4 (s) + 8HBr (g) = 3FeBr2 (s) + 4H2O (g) + Br2 (g)(130 K) (3)
3FeBr2 (s) + 4H2O (g) = Fe3O4 (s) + 6HBr (g) + H2 (g)(810 K) (4)...

iii. Zn/ZnO process. This is the so-called "SynMet"
process developed at PSI. The process combines
ZnO-reduction and CH4-reforming within a solar
reactor. It consists of a gas-particle vortex flow
confined to a solar cavity receiver that is exposed to
concentrated solar irradiation. A 5-kW reactor has
been built at PSI and subjected to tests in a high-flux
solar furnace. Natural gas is used as a reducing agent
to process ZnO according to the following overall
reaction:
ZnO + CH4 = Zn + 2H2 + CO(5)
The process reforms methane in the absence of
catalysts and is being optimized to produce syngas
especially suited for methanol synthesis, and coproduction
of Zn and syngas avoids CO2 emissions
in the traditional carbothermal reduction of ZnO.
Even though the PSI process is the only system
developed for direct solar interface, it is not,
however, a typical TCWSC, per se. [continued]

etc, etc, etc. This seems to be a very active field.

Also

Technical Barriers

This project addresses the following technical barriers from the Hydrogen Production section of the Hydrogen, Fuel Cells and Infrastructure Technologies Program Multi-Year R,D&D Plan:

• V. High- and Ultra-High-Temperature Thermochemical Technology
• W. High-Temperature Materials
• Y. Solar Capital Cost

http://216.239.39.104/search?q=cach...solar+furnace"+efficiency+cost+problems&hl=en

I would imagine that the reaction chambers don't last long. Zooby, did you spot anything that describes the actual cost of operating a system like this? I would think that there must be problems or we would be doing this on a large scale already. It would be nice to identify the difficulties faced with each type of technology. AFAIK we have found no magic bullet. Each energy option still needs work. I would hope that the grant money is starting to flow. If not yet, soon.

 

[Ivan Seeking]

It looks like the chemical processes have some competition.

ABSTRACT
The Department of Energy’s (DOE) Concentrating Solar
Power (CSP) Program is investigating the viability of
concentrating photovoltaic (CPV) converters as an
alternative to thermal conversion devices such as Stirling or
Brayton cycle engines that have historically been supported
by the program. Near-term objectives for CPV-related
activities within the program include development of inhouse
analytical tools and experimental facilities in support
of proof-of-concept demonstrations of high-concentration
CPV components and systems. SolTrace, a Monte Carlobased
optical simulation tool developed at the National
Renewable Energy Laboratory (NREL), has been used
extensively to analyze primary, secondary and receiver
optics associated with in-house and industrial CPV
configurations. NREL’s High-Flux Solar Furnace (HFSF)
has been adapted and used for preliminary testing of densepacked
arrays. Several research and development
subcontracts have been awarded for the development and
fabrication of components and systems. Hardware resulting
from these subcontracts has been delivered to NREL and is
undergoing evaluation at a CSP test facility located on
South Table Mountain, Golden, Colorado.[continued]

http://www.nrel.gov/docs/fy02osti/31143.pdf
sorry, no html version available

 

[Ivan Seeking]

Also

Abstract A solar-thermal aerosol flow reactor process is being developed to dissociate natural gas (NG) to hydrogen (H2) and carbon black at high rates. Concentrated sunlight approaching 10 kW heats a 9.4 cm long x 2.4 cm diameter graphite reaction tube to temperatures ~ 2000K using a 74% theoretically efficient secondary concentrator. A pure methane feed has been dissociated to greater than 75% for residence times less than 0.1 s. The resulting carbon black is 20 – 40 nm in size, amorphous, and pure. A 5 million (M) kg/yr carbon black / 1.67 M kg/yr H2 plant is considered for process scale-up. The total permanent investment (TPI) of this plant is $12.7 M. A 15% IRR after tax is achieved when the carbon black is sold for $0.66/kg and the H2 for $13.80/GJ. This plant could supply 0.06% of the world carbon black market. For this scenario, the solar-thermal process avoids 277 MJ fossil fuel and 13.9 kg-equivalent CO2/kg H2 produced as compared to conventional steam-methane reforming and furnace black processing.[continued]

This brings up another issue. The separation of H2 can result in valueable byproducts that then can be used or sold. This can reduce the effective cost per KWH significantly. In some cases, one might even imagine that the H2 production becomes secondary to the value of the "byproducts".

A solar-thermal process (Figure 8) for co-producing hydrogen (1670 t/yr) and carbon black (5000 t/yr) has been conceptualized and costed (± 30%; percentage of delivered equipment cost).

More about this particular project:

The 16.6 MWth plant has been designed for the Phoenix, AZ (USA) area (0.38 solar capacity factor). Produced carbon black will be sold into the carbon black market (world market is 7.9 M metric tonnes (t)/yr) and produced hydrogen will be supplied to a hydrogen pipeline at a pressure of 2.2 MPa. The plant will dissociate 7300 t/yr of natural gas (NG). Any mercaptans and H2S in the NG feed will be removed using an upstream hydrogenation reactor and ZnO bed. The NG will be dissociated at 70% conversion per pass in a fluid-wall aerosol flow reactor operating at 2000 K. The reactor consists of 3 tubes - an outer quartz protection tube and two inner graphite tubes. The most inner graphite tube is porous and allows recycled H2 to flow radially inward through the pores (fluid-wall), thus, preventing the deposition of carbon black along the inside wall of the reactor assembly. The H2 and carbon co-products and unreacted NG are then cooled in an expanded cooling zone and passed through a baghouse filter to separate the carbon black. The H2 and CHx are then fed to a pressure swing adsorber where approximately 80% of the H2 fed is purified and either sent to the H2 pipeline as product or recycled as purge and fluid-wall gas to the reactor. The reactor is sized from the kinetics rate expression developed by Dahl et al [12]. The inner porous graphite tube is approximately 20 cm in diameter and 2.2 m long. It is compact because the reaction rate at these temperatures is so rapid. The heliostat field is estimated to be 29,000 m2 area per calculations described by Spath and Amos [10].[continued]

http://216.239.39.104/search?q=cach...solar+furnace"+efficiency+cost+problems&hl=en

 

[zoobyshoe]

I would imagine that the reaction chambers don't last long. Zooby, did you spot anything that describes the actual cost of operating a system like this?

Yes, the temperatures are pretty high, of course. I only found the one site that had an operational systen in place, and it is a "demonstration model" so to speak, not at work constantly producing hydrogen. They didn't go into cost.

The chamber where they dump the hot zinc into the water would probably not wear out that fast. The chamber where they heat the zinc to drive the oxygen off would suffer the most thermal stress.

I would think that there must be problems or we would be doing this on a large scale already.

I don't think the notion that if it were a good system, we would already be using it, is true. I didn't find out about this system till today, and apparently you hadn't either. This thread has pointed out that hydrogen minded people are all scattered all over the place each exploring different ways to skin the hydrogen cat. That being the case, someone like a Westinghouse who might champion one method or another, has too many choices.

A good idea can be held back, also, for stupid reasons. There is a problem with some beaches in San Diego where the sand is all being washed away. A guy went to the city council and suggested they smash up old glass bottles and jars and tumble them till all the sharp edges are gone, put it through a screen to collect all the sand sized pieces and put this on the beach. It would save the beaches and landfill space. The council decided such a thing would require an environmental impact study. He tried to convince them that glass would have no effect on the environment that the original sand didn't have because glass was just sand in the first place, but they wouldn't believe him.

Hs conclusion was something to the effect that politicians are most concerned with not making any mistakes. The best way to assure they don't make any mistakes is to make sure nothing gets done. My point: a good idea not already being implemented.

 

[zoobyshoe]

This brings up another issue. The separation of H2 can result in valueable byproducts that then can be used or sold. This can reduce the effective cost per KWH significantly. In some cases, one might even imagine that the H2 production becomes secondary to the value of the "byproducts".

Any byproduct that has a use is good. Any system for producing H2 that produces a byproduct that has to be gotten rid of, is, of course, a waste of time.

In the case of H2 being the byproduct, you'd have to have a convenient entity for them to sell it to, and it would have to be convenient for that entity to buy it.

 

[russ_watters]

Consider solar panels [edit: ie. photovoltaic]. Solar technology promises to get cheap very quickly, but until now it is quite possible that the complete energy costs to produce the panels was greater than the energy recovered over the life of the panel.

Is it really that bad? For sure though, one of the toughest things to figure out in all of this is the economic implications - especially how fast/economically production of whatever new technology can be ramped up.