Any theoretical physicist or astronomers here?

[GneissGuy]

Originally Posted by ..

i disagree. even building a fuelcell which uses pure methane is non-trival. NG as fuel is much worse!

Note also, the bloom box is a electrical phys-chem. system thus NOT governed by the carnot-cycle, yet with NG as fuel it's not more efficient than a well-designed heat combusion engine.

1) You misunderstand my point. The idea of a fuel cell using various fuels is not new. The basic physics is not new. The trick is building one that works well and economically in real world conditions. I think it's been done before, but the problems have been cost, efficiency, lifetime, etc.

2) Absolutely correct. A fuel cell is not a heat engine, so Carnot's law is irrelevant. Carnot's law does not limit the theoretical efficiency of a fuel cell. I wonder if there are some other basic theoretical limits to a fuel cell's efficiency?

I'm not claiming the Bloom box is or isn't practical. I'm just pointing out the physics and engineering involved.

[Darth]

This is a VERY interesting discussion!! I am glad I stumbled upon it!! I have envisioned a similar idea as well, and the conclusion I have come to is not energy production problems, but energy storing problems...I.E.--the best we have now is batteries--which, as mentioned before have a limited lifespan, and are brutally expensive to replace in the types of numbers you would need. Solar, or wind, or any of 1000 renewable energy ideas have the same limitations generally--they don't store energy. A good solar array on a sunny day will produce plenty of power at the time--but when sun goes down-no power. The solution I have considered is a combination Solar/Wind/Fuel Cell/Electrolysis solution...It goes like this; a large power production method--getting the best efficiency wind turbines/solar cells/ micro hyrdo power to produce the power--Ensure that the power required to run your farm is less that what you system will produce on an AVERAGE day. The excess power runs the electrolysis process in the background continually--Store the hydrogen in tanks buried underground in the backyard, and send the oxygen into the house to make it fresh and clean! Every day, when you hit that point where due to darkness, or lack of wind your system loses any excess power, the hydrogen will automatically be pumped back into the fuel cell to make up the difference. Voila' your power storage problem is solved! There are limitations I have thought of--how do you compress the hydrogen in the tanks to such a point that the flow rate will be good enough to produce continuous power when on the Fuel Cell? I am sure there are other limitations to this that I haven;t thought of, but it sure seems like a good solution--and I have NO IDEA how cost effective it would be!!

[GneissGuy]

This will probably take several posts.

Originally Posted by npita

Also you (I think) stated something about the bloom box not using the Carnot cycle. That makes their claims stranger still. The Carnot cycle is the most efficient process you can create without violating the second law of thermodynamics (and creating a perpetual motion machine). Other cycles can have the same efficiency, but not using the Carnot cycle is not an argument that implies the bloom box could be more efficient in not doing so.

I understand your confusion about Carnot's law. Lots of people throw it around without understanding it.

Someone else (".." is the userid) brought up Carnot's law, not me, but he is correct. Carnot's law does NOT apply to the Bloom box or any other fuel cell. Or to batteries, either. Fuel cells are electrochemical devices. The Carnot cycle only applies to heat engines.

I'll simplify this somewhat.

A heat engine is a device that takes energy in the form of heat from a reservoir at one temperature and puts heat energy out to another reservoir at a lower temperature, producing mechanical energy in the process.

A good example of a heat engine is a steam boiler and turbine in a coal fired power plant. The heat engine is the boiler through the turbine. The hot reservoir is the hot gas in the burner. The cold reservoir is the ambient air. The output of the heat engine is mechanical energy from the turbine that drives the generator.

Carnot's law says that the maximum energy efficiency of a heat engine is T1-T2/T1. T1 is the temperature of the hot reservoir, T2 is the temperature of the cold reservoir. Temperature is expressed in an absolute scale, such as Rankine, Kelvin or any other scale where Absolute zero = 0 degrees.

Carnot's law only applies to heat engines.

A fuel cell is not a heat engine. The heat energy in a fuel cell does no work, the heat produced by the device is simply a waste byproduct of the energy production. The fuel cell does need to be heated to a high temperature to function, but the heat produces no energy. In concept, a fuel cell would operate even if the ambient air was at the same temperature as the fuel cell itself.

The same concept would apply to a battery. An alkaline battery can operate with the internal parts of the battery being the same temperature as the surrounding air. If Carnot's law applied to batteries, a battery could not produce any energy at all. Carnot's law doesn't apply to everything, only to heat engines.

If a device is not a heat engine, Carnot's law does NOT limit the efficiency of the device. There may be other considerations that impose a limit on the theoretical efficiency of a fuel cell.

In theory, a fuel cell generation system could always exceed the efficiency of the Carnot limit. Simply take the fuel cell waste heat and use it to drive a Carnot cycle heat engine. You get the efficiency of the Carnot engine plus the efficiency of the fuel cell.

By the way, the Carnot cycle is not a characteristic of a fuel, it's a characteristic of a system. You can increase the Carnot limit of a system by increasing the temperature of the hot reservoir or decreasing the temperature of the cold reservoir. There are usually practical problems that limit the temperatures you can use, though.

[GneissGuy]

Originally Posted by Celder1

This is a VERY interesting discussion!! I am glad I stumbled upon it!!...

Electrolysis as a means of energy storage is one of the many ideas being considered for renewable energy storage. Unfortunately, electrolysis/hydrogen storage seems to be less practical than the other available means of energy storage.

[tcreative2]

There have been several fuel cell attempts but none that I know of has figured out a way to strip the hydrogen off of the methane without using electricty. Plug Power, a NY residential fuel cell manufacturer, was down right deceptive in it's advertising and early stock promotion ......... it intimated freedom from the power grid but required 120/240V to run it's cell. Don't get excited about the Bloom box quite yet.

A really sharp energy storage device is currently under production in Austin. The German U-boats in WWII used a flywheel storage device that could produce enough electrical power to start the diesels if the batteries ran too low while submerged. The Austin start up took that idea and ran with it using a massive spinning flywheel supported above the generator gear by magnetic fields. A flywheel coupled with a generator could store energy and be geared to allow a slow and steady retrieval. Using mag.lev bearings the system could be very efficient. The flywheel device produced in Austin is designed to produce a very high amount of energy in a short period of time to fill in the gap between a power outage and the startup of back up generation. It's finding market acceptance and is replacing the massive battery facilities that are conventionally used for uninteruppted power supply. A similar product geared for residential photovoltaics could be easily designed.

[GneissGuy]

Originally Posted by npita

I noted that I was referring to hydrocarbons,

Your statement was:

Originally Posted by npita

All of those but (3) make sense. The end result of a reaction that produces energy from a hydrocarbon and oxygen is CO_2 and water (and if the original hydrocarbon contains radicals with other elements, like sulfur, that will be in the waste as well). If it's more efficient, the conversion will produce more CO_2. Inefficient processes just produce waste that contains other hydrocarbons.

My statement #3 was:

Originally Posted by GneissGuy

The possible advantages of Bloom box vs. grid power is: ... 3) Less CO2 from natgas bloom vs. grid coal power source.

See http://en.wikipedia.org/wiki/Greenhouse_gas

Coal produces 205 or more lbs of CO2 per million BTU.
Natgas produces 117 lbs of CO2 per million BTU.

You get 75% more CO2 per unit of total energy produced from coal vs. natgas. Anything consuming natgas instead of coal starts off with a 75% advantage in terms of energy per unit of CO2 output. How the final energy and CO2 efficiency comparison comes out will be something we find out after more real world experience with the Bloom box is obtained.

I do NOT assume the Bloom box is 100% efficient.

Originally Posted by npita

However, the only thing bloom energy has made public is that methane (or whatever) goes in and electricity comes out.

They've published info that makes it clear that it's a natgas fueled ceramic based fuel cell. Other people have produced these before. These have been produced before and are well proven to work. Economical use in the real world is another question.

Originally Posted by npita

How can the science be clear without the secret information?

Nothing they've claimed violates any laws of physics. The principles are well understood. Similar devices have been built and work from a technical standpoint. They have not given out the details of what makes their natgas ceramic fuel cells better than the competition.

If you have problems with the semantics, that's your problem, not ours.

Once again, I don't claim it's efficient, it's reliable, it's cost effective, etc. I'm just saying that nothing they claim is impossible. It's not even that implausible. Time will tell how well it works in the real world.

[Fast Gunn]

Okey, then let's chart what we've all said here:

Is Everything clear?

[winemaker]

Originally Posted by npita

``When a hydrocarbon burns in oxygen, the reaction will only yield carbon dioxide and water.''

Your missing the point and comparing apples to oranges. The point is that if you pick a hydrocarbon, which in the case of the bloom box, means methane, complete combustion (or 100% efficiency) produces only CO_2 and water in the proportions given above. The heat produced (or absorbed) in ANY chemical reaction depends only on the difference in binding enegies of the reactants and products.

For a hydrocarbon, that means the reactants consist of a hydrocarbon (a molecule consisting of carbon and hydrogen) and the products produced with a given amount of oxygen. If you supply enough oxygen for complete combustion (100% efficiency) you get water and carbon dioxide..

Well, errr, NO.
1) There is no concept of 100% conversion effeciency in reality
2) Natural Gas is not just methane
3) It requires a PURE oxygen environment to get what you are stating, not "merely" enough oxygen.
Reaction kinetics of other pollutant molecules (i.e. adulterants ), will have reaction byproducts, such as Carbon Monoxide, etc.

5) Since it requires a rich oxygen environment, where is the source for the O2 ? Highly doubt its atmospheric pressure. So, then you have to now include the amount of energy required to create the pressurized O2 for the device itself.

When you look at the total system energy requirements, all of a sudden things start looking pretty ineffecient.


They are probably using a zeolitic material as the ceramic, been pretty standard in the petrochemical industry for years.

[GneissGuy]

e**iπ + 1 = 0 therefore God exists.

[Sinning]

Preface: I'm no physicist. In fact, my formal education ended when the dean of engineering asked me to come back when I was more mature. BUT, I compensate for my ignorance with tenacity.

Where to start.....

1. While I do believe there are some very difficult times ahead, my concerns are grounded in simple, proven, socioeconomic and behavioral principles, not 2012 fantasies.

2. I enjoy "science projects". Rather than spend my free time idly surrendering IQ points to the television, I like to spend my time with my family working on something that stimulates the mind.

3. Like most folks, my resources are finite. Anything I can do to consistently improve the production of those resources, or reduce our consumption of them comfortably, serves us well.

That said......

I've started with a pretty standard hoffman apparatus, powering the reaction via the DC output from the photovoltaic panels. Purified water was not conductive, so I switched to tap. The electrodes are platinum, but the O2 side is oxidizing. The impurities will occasionally need to be cleaned but it is currently producing about a 1/2 cubic inch per hour H2, and about 1/3 that O2. As for storage, I do not intend to store much of either gas, but instead to funnel the diatomic gases across ionized plates (essentially battery) to generate the electricity to be stored in a deep cell battery rack (I am unconcerned with the economic viability - only that the principles are sound. We all know that theory rarely translates into reality precisely as conceived) The following are the general guidelines I am trying to adhere to for this project.

A.) Use materials commonly found in nature, or easily refined using mundane tools.

B.) Materials should be recycled, reused where possible.

C.) Final working model must have as few degrading and/or consumable parts that require replacement as possible, unless satisfactorily meeting A & B.

The concept is to produce electricity as autonomously (requiring little or no interaction), efficiently (100% is impossible, but how close can it get?), renewably, safely, and as maintenance free as possible. Storage and distribution is easy if you take the economics out of it.

So.....here are a few of my questions:

1) What materials would oxidize least as electrodes (or more slowly than platinum)?

2) What about using Erbium to somehow enhance this solution, or any solar power related project? It occurs in nature more commonly than lead, produces more energetic photons than it absorbs, and has a relatively low toxicity level?

[GneissGuy]

Originally Posted by Sinning

As for storage, I do not intend to store much of either gas, but instead to funnel the diatomic gases across ionized plates (essentially battery) to generate the electricity to be stored in a deep cell battery rack

If you're not storing the hydrogen, there's no reason to have the electrolysis cell and fuel cells. Just feed the electricity from the solar cells directly into the batteries.

[Sinning]

Solar cells only generate a small amount of electricity per panel, and in tornado alley weather, are less than desirable as a single power source. Additionally, the design I'm using can run 24 hrs consistently, and is a more versatile solution. Should I have need of a fuel for combustion, it can easily be extracted.

[GneissGuy]

Originally Posted by Sinning

Solar cells only generate a small amount of electricity per panel, and in tornado alley weather, are less than desirable as a single power source. Additionally, the design I'm using can run 24 hrs consistently, and is a more versatile solution. Should I have need of a fuel for combustion, it can easily be extracted.

You're throwing away most of your power unnecessarily in the electrolysis/fuel cell step. Charge the batteries directly from the solar cells. Even if you already have a working electrolysis/fuel cell combination, it makes no sense to convert the electricity to H2 and O2 and then combine it back into H2O to charge the battery.

The only way the electrolysis step helps you is if you have a way to store lots of hydrogen. Even then, it's probably not really a viable solution. Buying additional storage batteries will be cheaper, more efficient, and more practical.

[pjorourke]

Now if you guys want to talk theoretical physics:

Our Universe at Home Within a Larger Universe?