Thermodynamics Vs Eco-Fantasy

Thermodynamics wins:

Hydrogen is only a source of energy if it can be taken in its pure form and reacted with another chemical, such as oxygen. But all the hydrogen on Earth, except that in hydrocarbons, has already been oxidized, so none of it is available as fuel. If you want to get plentiful unbound hydrogen, the closest place it can be found is on the surface of the Sun; mining this hydrogen supply would be quite a trick. After the Sun, the next closest source of free hydrogen would be the atmosphere of Jupiter. Jupiter is surrounded by radiation belts so intense that they are deadly to humans and electronics. It also has a massive gravity field that would severely impair hydrogen export operations. These would also be complicated by the 2.5-year Jupiter-to-Earth flight transit time (during which any liquid hydrogen launched would probably boil away), and the fact that upon re-entry at Earth, the imagined hydrogen shipping capsule would face heat loads about eight times higher than those withstood by a space shuttle returning from orbit.

So if we put aside the spectacularly improbable prospect of fueling our planet with extraterrestrial hydrogen imports, the only way to get free hydrogen on Earth is to make it. The trouble is that making hydrogen requires more energy than the hydrogen so produced can provide. Hydrogen, therefore, is not a source of energy. It simply is a carrier of energy. And it is, as we shall see, an extremely poor one.

The spokesmen for the hydrogen hoax claim that hydrogen will be manufactured from water via electrolysis. It is certainly possible to make hydrogen this way, but it is very expensive—so much so, that only four percent of all hydrogen currently produced in the United States is produced in this manner. The rest is made by breaking down hydrocarbons, through processes like pyrolysis of natural gas or steam reforming of coal.

Neither type of hydrogen is even remotely economical as fuel. The wholesale cost of commercial grade liquid hydrogen (made the cheap way, from hydrocarbons) shipped to large customers in the United States is about $6 per kilogram. High purity hydrogen made from electrolysis for scientific applications costs considerably more. Dispensed in compressed gas cylinders to retail customers, the current price of commercial grade hydrogen is about $100 per kilogram. For comparison, a kilogram of hydrogen contains about the same amount of energy as a gallon of gasoline. This means that even if hydrogen cars were available and hydrogen stations existed to fuel them, no one with the power to choose otherwise would ever buy such vehicles. This fact alone makes the hydrogen economy a non-starter in a free society.

And even if you are among those willing to sacrifice freedom and economic rationality for the sake of the environment, and therefore prefer hydrogen for its advertised benefit of reduced carbon dioxide emissions, think again. Because hydrogen is actually made by reforming hydrocarbons, its use as fuel would not reduce greenhouse gas emissions at all. In fact, it would greatly increase them.

To see this, let us consider an example. Let’s say you wanted to produce hydrogen. You choose to do it via steam reformation of natural gas, the most common technique used commercially today. The reaction is:

CH4 + 2H2O => CO2 + 4H2 ΔH = +59 kcal/mole (1)

As the positive enthalpy change indicates, the reaction is endothermic (that is, heat-absorbing) and will need an outside source of energy to drive it forward. This can be obtained by burning some methane, which releases 205 kcal/mole, via the following reaction:

CH4 + 2O2 => CO2 + 2H2O ΔH = 205 kcal/mole (2)


Assuming an optimistic 72 percent efficiency in using the combustion energy to drive the steam reformation, this would allow us to reform 2.5 moles of methane for every one that we burn (or 5 for every 2). So if we take five units of reaction (1) and add it to two units of reaction (2), the net reaction becomes:

7CH4 + 4O2 + 10H2O => 7CO2 + 4H2O + 20H2
(3)


As far as usable fuel is concerned, what we have managed to do is trade seven moles of methane for twenty moles of hydrogen. Seven moles of carbon dioxide have also been produced, exactly as many as would have been produced had we simply used the methane itself as fuel. The seven moles of methane that we used up, however, would have been worth 1435 kilocalories of energy if used directly, while the twenty moles of hydrogen we have produced in exchange for all our trouble are only worth 1320 kilocalories. So for the same amount of carbon dioxide released, less useful energy has been produced.

The situation is much worse than this, however, because before the hydrogen can be transported anywhere, it needs to be either compressed or liquefied. To liquefy it, it must be refrigerated down to a temperature of 20 K (20 degrees above absolute zero, or -253 degrees Celsius). At these temperatures, the fundamental laws of thermodynamics make refrigerators extremely inefficient. As a result, about 40 percent of the energy in the hydrogen must be spent to liquefy it. This reduces the actual net energy content of our product fuel to 792 kilocalories. In addition, because it is a cryogenic liquid, still more energy could be expected to be lost as the hydrogen boils away during transport and storage.

As an alternative, one could use high pressure pumps to compress the hydrogen as gas instead of liquefying it for transport. This would only require wasting about 20 percent of the energy in the hydrogen. The problem is that safety-approved, steel compressed-gas tanks capable of storing hydrogen at 5,000 psi weigh approximately 65 times as much as the hydrogen they can contain. So to transport 200 kilograms of compressed hydrogen, roughly equal in energy content to just 200 gallons of gasoline, would require a truck capable of hauling a 13-ton load. Think about that: an entire large truckload delivery would be needed simply to transport enough hydrogen to allow ten people to fill up their cars with the energy equivalent of 20 gallons of gasoline each.

Instead of steel tanks, one could propose using (very expensive) lightweight carbon fiber overwrapped tanks, which only weigh about ten times as much as the hydrogen they contain. This would improve the transport weight ratio by a factor of six. Thus, instead of a 13-ton truck, a mere two-ton truckload would be required to supply enough hydrogen to allow a service station to provide fuel for ten customers. This is still hopeless economically, and could probably not be allowed in any case, since carbon fiber tanks have low crash resistance, making such compressed hydrogen transport trucks deadly bombs on the highway.

In principle, a system of pipelines could, at enormous cost, be built for transporting gaseous hydrogen. Yet because hydrogen is so diffuse, with less than one-third the energy content per unit volume as natural gas, these pipes would have to be very big, and large amounts of energy would be required to move the gas along the line. Another problem with this scheme is that the small hydrogen molecules are brilliant escape artists. Hydrogen can not only penetrate readily through the most minutely flawed seal, it can actually diffuse right through solid steel itself. The vast surface area offered by a system of hydrogen pipelines would thus afford ample opportunity for much of the hydrogen to leak away during transport.

As hydrogen diffuses into metals, it also embrittles them, causing deterioration of pipelines, valves, fittings, and storage tanks used throughout the entire distribution system. These would all have to be constantly monitored and regularly inspected, tested, and replaced. Otherwise the distribution system would become a continuous source of catastrophes.

Given these technical difficulties, the implementation of an economically viable method of retail hydrogen distribution from large-scale central production factories is essentially impossible. Because of this, an alternative concept has been proposed wherein methane or methanol fuel would be transported by pipeline or truck, and then steam-reformed into hydrogen at the filling station itself. This would eliminate most of the cost of hydrogen transport, but would increase the cost of the hydrogen itself, since small-scale reformers are less efficient, both economically and energetically, than large-scale industrial units. Also, it is questionable how many service stations would want to buy, operate, and maintain their own steam reforming facility. The station would also need to operate its own 5,000 psi explosion-proof high pressure hydrogen pump, or a cryogenic refrigeration plant, both of which are very unappealing prospects. Such a scheme of distributed production stations would also eliminate any hope of implementing the hydrogen economy’s advertised plan to sequester underground the carbon dioxide produced as a byproduct of its hydrogen manufacturing operations. At bottom, the whole idea is ridiculous, since either the methane or methanol used as feedstock at the station to make the hydrogen would be a better automobile fuel, containing more energy, in less volume, at less cost, than the hydrogen it yields.

The idea of producing hydrogen via water electrolysis locally at filling stations is equally preposterous. To see this, consider the following. A kilogram of hydrogen has about the same energy content as a gallon of gasoline, so the owner of a filling station could only expect to obtain the same net income from a kilogram of hydrogen as from a gallon of gas. A reasonable figure for this might be $0.20 per kilogram. To obtain a modest net income of $200 per day from hydrogen sales would therefore require selling 1,000 kilograms per day. Since hydrogen requires about 163,000 kJ/kg to produce via electrolysis (assuming an 85 percent efficient electrolyzer), this means that 163,000,000 kJ = 45,278 kW-hr per day would be required by the station. At current grid power costs of $0.06/kW-hr, this would run the station an electric bill of $2,717 per day. If the electrolysis unit ran around the clock, it would need to be supplied with 1,900 kilowatts of electricity (about a thousand times the power draw of a typical house). This power would need to be supplied by the utility over special heavy-duty lines, and then transformed and rectified into direct current on site for use in the electrolyzer. Electrolyzers use high amp-low voltage power. In this case, at least several hundred thousand amps would be required. And the 1,900-kilowatt electrolyzer would not be cheap either. At current prices such a unit would cost the station owner over $10 million, which mortgaged over thirty years would cost him about $100,000 per month, assuming it lasted that long. (No one would want to do this, of course, since the same $10 million invested in five percent bonds would return $500,000 per year, or seven times the $200 per day hydrogen sales income under discussion, with no work and no risk.) Then the station owner would still need to buy and operate either a 5,000 psi explosion-proof compressor pump or a cryogenic refrigerator, and build and accept liability for high-pressure or cryogenic hydrogen storage facilities on his properties. Having paid for all that, there would then be the little matter of insurance.

This, as should be obvious, is economic insanity. For just $6,000 per day, plus insurance costs, you could make $200, provided you can find fifty customers every day willing to pay triple the going price for automobile fuel. I don’t know about you, but if I were running a 7-11, I’d find something else to sell.

I well remember my Thermodynamics course in college. It taught me the fundamentally conservative principle "There ain't no such thing as a free lunch" and to be wary of anybody trying to sell you one.