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Author Topic: Fossil Fuels: Degraded Democracy and Profit Over Planet Pollution  (Read 30413 times)

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AGelbert

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    • Renwable Revolution
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AG: Hess's Law DOES NOT differentiate between WASTE HEAT ENERGY and USEFUL HEAT ENERGY.

True.      

As I said before:
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Palloy: Energy Density is how much Energy a fuel contains per unit of Volume or Mass.  In the case of FFs, you extract that Energy by burning the fuel, producing Heat Energy.  After that, what you do with the energy is up to you - no doubt some of it will be wasted, and some will do work.  But Energy Density is a feature that the fuel has BEFORE it is burned, when there is no waste.

There is definitely no inefficiency in Hess's Law - Thermodynamics wouldn't work if there was.
CH4 + 2O2 => CO2 + 2H2O (steam) + energy
∆H: -74.81 + 0 = -393.5 + 2*( -241.8 ) + X
X = 393.5 + 2*241.8 - 74.81
X = 802.29 kJ/mol

A mol of Methane has a Mass of (12 + 4*1) = 16 grams
So Methane has an Energy Density of 50.143 kJ/gram
This differs from your quoted figure of 55.496 kJ/gram because that assumes burning Methane produces liquid water, not Steam (they have different ∆H: -241.8 and -285.8 ).  If liquid water remained in the furnace, it would eventually flood the reaction, so the furnace output (not the boiler) MUST be steam.  The difference between your figure and the correct one is the energy it takes to turn the liquid H2O to steam.
Isn't Hess's Law neat?

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AG: But Hess's Law LOWBALLS the enthalpy of LOW WASTE HEAT biofuels like ETHANOL because they have LESS waste heat than hydrocarbons.

In a sane world of thermodynamics calculations on chemical compound combustion, the WASTE HEAT should be SUBTRACTED from the figure arrived at using Hess's Law.

No, that is wrong.

Hess's Law describes the chemical reaction - it doesn't say anything about what you are going to do with the heat after you've got it.

OK, so now you have your heat, 50.143 kJ/gram of Methane, what are you going to do with it? - boil water to produce steam.  Try as you might, that process is going to be less than 100% efficient because some heat will always be lost through the walls of the boiler to the atmosphere.  That Energy is Waste Heat, but it is NOT the fault of Hess's Law, it is the fault of the boiler's efficiency (an engine).

Then you are going to take that steam and run it through a steam turbine (maybe several in cascade).  That is another engine and it will have an efficiency of less than 100%.

Then you are going to take the Energy of the spinning shaft and couple it to an electrical generator, another engine, again with an efficiency of less than 100%.

So the complete process is:
(Mass of Methane * Energy Density) = Fuel Energy
and Fuel Energy * efficiency of boiler * efficiency of turbine * efficiency of generator = Electrical Energy
and (Electrical Energy / Fuel Energy) is the efficiency of the whole system.

Now the amount of Methane entering the system is known, and the amount of electrical energy leaving the system is known, so the efficiency of the whole system is known, and that is what is used in ERoEI calculations.

I can't see what your problem is, except that your 55.496 figure is wrong, it should be 50.143.
Hess's Law and its table of ∆H values is 100% correct and is nothing to do with waste.

Don't you ever get tired of thumbs down? Talk about wasting electrons.

What, exactly, is your problem with the enthalpy of COMBUSTION table I just gave you?


My math comes from published tables. If you have a problem with them, argue with wikipeda, not me.

You can rant and rave about efficiency and there allegedly not being any "inefficiencies" in Hess's Law until the cows come home, but I never said beans about the Hess Law "inefficiencies". I merely stated that the experimental basis for obtaining the energy density values, WHEN THEY CAN OBTAIN THEM (which is simply impossible in some cases), is through measurement of EXTERNAL combustion.

What part of that is too difficult for you to understand?

Every time the subject of the higher ERoEI of ethanol than other hydrocarbons comes up, you have spasms of uncontrollable twitching, for some reason.

You have often gone into great detail about how much of this, that and the other is fossil fuel based to deny the cost effectiveness of SEVERAL Renewable Energy technologies, not just ethanol and other biofuels.

YET, when I point out peer reviewed studies  that prove ethanol beats hydrocarbon fuels, you pull out your down thumb smiley. LOL!

Hess's Law had its place in contributing to the Law of Conservation of Energy, but it is an inappropriate method of basing the start of ERoEI calculations. Even wikipeda agrees that ERoEI calculation should ONLY INCLUDE USEFUL ENERGY. Gross Energy density values include potentially useful and potentially useless energy known as waste. Deny it all you wish, but those are the thermodynamic facts.

Quote
In physics, energy economics, and ecological energetics, energy returned on energy invested (EROEI or ERoEI); or energy return on investment (EROI), is the ratio of the amount of usable energy delivered from a particular energy resource to the amount of energy used to obtain that energy resource.[1][2] It is a distinct measure from energy efficiency as it does not measure the primary energy inputs to the system, only usable energy.

A fuel or energy must have an EROEI ratio of at least 3:1 to be considered viable as a prominent fuel or energy source.[3][4]

The irony of the above quote is that wikipeda then proceeds to post all the Charles Hall fossil fuel and nuclear power happy talk ERoEI charts.

But, to their credit, they do admit that ERoEI calculations have no actual standard rigorous and required inputs. Therefore, ERoEI math is a fossil fuel industry cherry picking paradise.

Quote

Measuring the EROEI of a single physical process is unambiguous, but there is no agreed-upon standard on which activities should be included in measuring the EROEI of an economic process. In addition, the form of energy of the input can be completely different from the output. For example, energy in the form of coal could be used in the production of ethanol. This might have an EROEI of less than one, but could still be desirable due to the benefits of liquid fuels.

How deep should the probing in the supply chain of the tools being used to generate energy go? For example, if steel is being used to drill for oil or construct a nuclear power plant, should the energy input of the steel be taken into account, should the energy input into building the factory being used to construct the steel be taken into account and amortized? Should the energy input of the roads which are used to ferry the goods be taken into account? What about the energy used to cook the steelworker's breakfasts? These are complex questions evading simple answers.[28] A full accounting would require considerations of opportunity costs and comparing total energy expenditures in the presence and absence of this economic activity.

However, when comparing two energy sources a standard practice for the supply chain energy input can be adopted. For example, consider the steel, but don't consider the energy invested in factories deeper than the first level in the supply chain.

Energy return on energy invested does not take into account the factor of time. Energy invested in creating a solar panel may have consumed energy from a high power source like coal, but the return happens very slowly, i.e. over many years. If energy is increasing in relative value this should favour delayed returns. Some believe this means the EROEI measure should be refined further.

Conventional economic analysis has no formal accounting rules for the consideration of waste products that are created in the production of the ultimate output. For example, differing economic and energy values placed on the waste products generated in the production of ethanol makes the calculation of this fuel's true EROEI extremely difficult.

They also break down the three prominent ERoEI calculations, while ignoring the fact that the Charles Hall type SUNY "studies", whether they allegedly  ;) use 'point of use' or 'extended' (FORGET 'societal' - the dirty energy corporations don't DO 'societal') exclude inconvenient costs and include gamed dirty energy subsidies that artificially give fossil fuel and nuclear power "high" ERoEI and lowball Renewable Eenrgy ERoEI.

Quote
There are three prominent expanded EROEI calculations, they are point of use, extended and societal. Point of Use EROEI expands the calculation to include the cost of refining and transporting the fuel during the refining process. Since this expands the bounds of the calculation to include more production process EROEI will decrease.[21]

Extended EROEI includes point of use expansions as well as including the cost of creating the infrastructure needed for transportation of the energy or fuel once refined.[30]

Societal EROI is a sum of all the EROEIs of all the fuels used in a society or nation. A societal EROI has never been calculated and researchers believe it may currently be impossible to know all variables necessary to complete the calculation, but attempted estimates have been made for some nations.


https://en.wikipedia.org/wiki/Energy_returned_on_energy_invested




Things were simpler in the middle of the 19th Century

Hess's Law of the constant summation of heat was obviously a special case of the law of the conservation of energy, which had not yet been formally stated.

But that was then. NOW the polluters use Hess's Law to our detriment and their profit.
 
The REALITY of WASTE HEAT in fuels for internal combustion engines, as well as the ENERGY REQUIRED to ameliorate the POLLUTION those fuels produce when combusted, is excluded. This convenient fiction distorts the value of selected energy sources, resulting in the use of NEGATIVE ERoEI, inefficient and polluting, hydrocarbon fuels to run industrial civilization.

In the REAL world we live in called the biosphere, this is unsustainable because the balance of energy radiated to space versus that received from the sun is altered towards life destroying heat.

It IS a closed system. ALL factors must be computed. Hess's Law is an ABERRATION of the Law of Conservation of Energy because it reduces the concept of "energy" to heat, whether or not it is waste (i.e. USELESS for work and damaging to the biosphere) heat.

TODAY, Hess's Law is used BY THE FOSSIL FUEL INDUSTRY and the CHEMICAL MANUFACTURING INDUSTRY to arbitrarily to exclude inconvenient thermodynamic FACTS in order to downplay the value of Renewable energy based technologies that produce fuels, textiles, plastics, medicines, etc.

Hess's Law, because it is the most basic enthalpy step to obtain energy density values for chemical compounds that are subsequently used in Energy Return on Energy Density (ERoEI) calculations, has helped the Fossil Fuel Industry Perpetuate the following MYTH: It Takes More Energy to ­Produce Ethanol than You Get from It!


Most ethanol research over the past 25 years has been on the topic of energy returned on energy invested (EROEI). Public discussion has been dominated by the American Petroleum Institute’s aggressive distribution of the work of Cornell professor David Pimentel and his numerous, deeply flawed studies. Pimentel stands virtually alone in portraying alcohol as having a negative EROEI—producing less energy than is used in its production.

In fact, it’s oil that has a negative EROEI. Because oil is both the raw material and the energy source for production of gasoline, it comes out to about 20% negative.

That’s just common sense; some of the oil is itself used up in the process of refining and delivering it (from the Persian Gulf, a distance of 11,000 miles in tanker travel).

The most exhaustive study on ethanol’s EROEI, by Isaias de Carvalho Macedo, shows an alcohol energy return of more than eight units of output for every unit of input—and this study accounts for everything right down to smelting the ore to make the steel for tractors.

But perhaps more important than ERoEI is the energy return on fossil fuel input. Using this criterion, the energy returned from alcohol fuel per fossil energy input is much higher. In a system that supplies almost all of its energy from biomass, the ratio of return could be positive by hundreds to one.

Put your DOWN THUMB out there all you want, Palloy. You are wrong about high ERoEI for fossil fuels and low ERoEI for Renewable energy..
He that loveth father or mother more than me is not worthy of me: and he that loveth son or daughter more than me is not worthy of me. Matt 10:37

 

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