Monthly Discussion



Our Need for Hydrogen


The energy market is a niche where various primary energy sources coexist and compete with each other. It was in 1975 when Marchetti first applied the generalized substitution model and found surprisingly good description of worldwide data over a historical window of more than one hundred years. His updated results are reproduced in Exhibit 3 as published in PREDICTIONS.

During the last one hundred years, wood, coal, natural gas, and nuclear energy are the main protagonists in supplying the world with energy. More than one energy source is present at any time, but the leading role passes from one to the other. Wind power and water power have been left out because they command too small a market share.



Exhibit 3. Data, fits, and projections for the shares of different primary energy sources consumed worldwide. For nuclear, the dotted straight line is not a fit but a trajectory suggested by analogy. The futuristic source labeled 鉄olfus may involve solar energy and thermonuclear fusion. The small circles show how things evolved since 1982 when this graph was published in PREDICTIONS. *


In the early nineteenth century and before, most of the world's energy needs were satisfied through wood burning and to a lesser extent animal power not shown in the figure. Contrary to the popular image of coal-burning locomotives, wood remained the principal fuel for railroads in the United States up to the 1870s. The substitution process shows that the major energy source between 1870 and 1950 was coal. Oil became the dominant player from 1940 onward, as the automobile matured, together with petrochemical and other oil-based industries.

It becomes evident from this picture that a century-long history of an energy source can be described quite well耀mooth lines謡ith only two constants, those required to define a straight line. (The curved sections are calculated by subtracting the straight lines from 100 percent.) The destiny of an energy source, then, seems to be cast during its early childhood, as soon as the two constants describing the straight line can be determined.

There are other messages in Exhibit 3. By looking more closely at the data we see that world-shaking events such as wars, skyrocketing energy prices, and depression had little effect on the overall trends. More visible may be the effect of strikes. In the coal industry, for example, such actions result in short-term deviations, but the previous trend is quickly resumed.

Another observation is that there is no relationship between the utilization and the reserves of a primary energy source. It seems that the market moves away from a certain primary energy source long before it becomes exhausted, at least at the world level. And vice-versa; despite the ominous predictions made in the 1950s that oil would dry up in twenty years, oil use continued growing unhindered and more oil was found as needed. Oil reserves will probably never be exhausted because of the timely introduction of other energy sources. Well-established substitution processes with long time constants are of a fundamental nature and cannot be reversed by "lesser" reasons such as depletion of reserves.

Exhibit 3 also indicates that natural gas will replace oil progressively to reach a zenith in the 2020s and become more important worldwide than oil was in the 1970s. Supplying a major fraction of the world's energy needs by gas will require much more gas than today's proven reserves, but one need not worry about it; important natural gas fields are likely to be found. Searches for "dry" gas have also started. Gas is a more probable find than oil the deeper one goes underground, due to the thermal gradient of the earth's crust. Ultimately, if during the gas era the discovery of new gas fields does not keep up with demand, for whatever reason, oil or coal may be artificially processed to produce the amount of gas lacking. Synthetic gaseous fuels such as methanol could easily be used in cars.

But history since 1982 has proven the gas takeover inaccurate. The small circles in Exhibit 3 show important deviations from the projected trends for the shares of coal and natural gas. While the trajectories for oil and nuclear energy consumption turned out as predicted, the evolution of natural gas fell way below what had been expected, and the share of coal remained high deviating progressively more and more from the predicted course. How can these energy sources behave like species in natural competition for almost one hundred years, and then suddenly fall in disarray?

Cesare Marchetti argues that the deviation is due to legislative intervention by some governments (for example, U.K. and Germany) to keep coal production levels high. Such interventions can be considered "unnatural" and should be corrected sooner or later. According to this thinking, pressure must be building up for corrective action, which could take the form of miners' strike, social unrest, or other political intervention. But there is another problem. The extraordinary gains of coal depress the market share of natural gas instead of that of oil. In the substitution model there should be no interaction between phasing-in and phasing-out competitors; everyone competes against the frontrunner, in this case oil, and yet in Exhibit 3 natural gas, a phasing-in competitor, loses market share to coal, a phasing-out competitor. Oil, the competitor with the dominant market share, that normally should feel the competitive squeeze, behaves like a non-participating spectator of the coal-gas struggle. As if natural gas had become vulnerable prematurely.

The explanation may lie with the intimate relationship between energy source and means of transportation. We saw earlier that there is a coupling between energy and transportation in the sense that each type of transportation is associated with one principal fuel, even if early and late version of it may use different fuels. Coal was the principal fuel of railroads and oil that of automobiles. The principal fuel of the airplane could well be some gas (natural gas in the beginning, hydrogen eventually). But the corresponding airplane technology is still not there. With airplanes not requiring gas as fuel, the lack of important demand for gas translates to diminished competitiveness so that when coal persists in the market, gas suffers (out of turn) before oil.

Environmentalists have been very vocal in their support of natural gas. I wonder, however, what has really been their role in the greening of natural gas. The importance of gas in the world market has been growing steadily for the last ninety years, independent of latter-day environmental concerns. The voice of environmentalists reminds me of Ralph Nader's crusade in the 1960s for car safety, while the number of deaths from car accidents had already been pinned around 23 annually per 100,000 population since the 1930s!

Environmentalists had also taken a vehement stand on the issue of nuclear energy. This primary energy source entered the world market in the mid 1970s when it reached more than 1 percent share. The rate of growth during the first decade was disproportionably rapid, however, compared to the entry and exit slopes of wood, coal, oil and natural gas, all of which conformed closely to a more gradual rate (see Exhibit 3). At the same time, the opposition to nuclear energy was also out of proportion when compared to other environmental issues. As a consequence of the intense criticism, nuclear energy growth slowed down considerably, but did not stop. The little circles in Exhibit 3 are steadily approaching the straight line proposed by the model. One may ask what was the prime mover here葉he environmental concerns that succeeded in slowing the rate of growth or the nuclear energy craze that forced environmentalists to react?

Exhibit 3 suggests that nuclear energy has a long future. Its share should grow at a slower rate, with a trajectory parallel to those of oil, coal, and natural gas. But there is no alternative in sight. The next primary energy source庸usion and/or solar and/or other擁s projected to enter the picture by supplying 1 percent of the world's needs in the 2020s. This projection is reasonable because such a technology, once shown to be feasible, would require about a generation to be mastered industrially, as was the case with nuclear energy.

Let us try to be optimistic and suppose that progress gallops and a new clean energy source (possibly involving several technologies) enters the world market during the first decade of the twenty-first century. It will have to grow at the normal rate, the rate at which other types of energy have entered and exited in the past. Therefore, it will have an impact on nuclear energy similar to the way gas had an impact on oil. That is, nuclear energy, and to a lesser extent gas, will saturate at lower levels while the new energy will reach relatively higher shares. Still, nuclear energy will have played a role at least as important as oil did in its time.



When Will Hydrogen Come?


One of the most recent (and most vocal) concerns of environmentalists is CO2 (carbon dioxide) pollution, presumably responsible for global warming. Present levels of CO2 in the atmosphere have reached record-high values primarily due to coal burning worldwide and gas emissions from automobiles in developed countries. However, the environmentalists are once again blowing the whistle for a phenomenon that has been following a "wise" natural-growth path for more than one hundred years.

As we moved from one energy source to the next in Exhibit 3 the hydrogen content of the fuel increases. Wood is rich in carbon but natural gas is rich in hydrogen. When hydrogen burns it gives water as exhaust; when carbon burns it gives CO2 as exhaust. When wood burns very little hydrogen becomes oxidized to give water. Most of the energy comes from the carbon that oxidizes to give CO2. On the contrary, when natural gas burns lots of hydrogen become water and very little carbon becomes CO2. The molar ratio hydrogen/carbon for wood is about 0.1, for coal about 1, for oil about 2, and for natural gas (e.g., methane) about 4. For a fuel like hydrogen this ration becomes infinite and the CO2 emissions to the atmosphere null.*

The energy substitution described in Exhibit 3 took place in such a way that fuels rich in hydrogen progressively replaced fuels rich in carbon, and all that happened in a natural way (i.e., following an S-shaped pattern). We moved from one energy source to the next primarily in order to enhance the energy content of our fuel. One pound of coal has more energy in it than one pound of wood. Similarly, one pound of oil has more energy in it than one pound of coal. Still, one pound of natural gas has more energy in it than one pound of oil. In each substitution we are abandoning an energy source with less hydrogen atoms in it for an energy source richer in hydrogen. The end of this sequence will be when we finally use pure hydrogen as is actually done in rocket technology.

The combination of energy sources according to the shares shown in Exhibit 3 yields a hydrogen content that increases along an S-curve (see Exhibit 4). Society followed this S-curve on a global scale without the conscious intervention of governments or other influential decision makers. Bottom-up forces have safeguarded for one hundred and fifty years a smooth transition to energies that are more performing and less polluting.

The black dots in Exhibit 4 represent the mix of only fossil-based energy sources (there is no hydrogen involved in nuclear energy). As a consequence, a deviation from the S-shaped pattern becomes evident around year 2000 and becomes progressively more pronounced toward year 2050. The gray area in the figure represents the "missing" hydrogen content. This amount of hydrogen could be contributed by nuclear energy, if we want to continue the well-established natural course.

Nuclear energy can indeed do that in a number of different ways. For example seawater can be split into hydrogen and oxygen via electrolysis or by direct use of nuclear heat. It must be noted that nuclear energy is not indispensable for the natural path to be maintained. There is enough hydrogen in the fossil-based energies, so it suffices to simply adjust the mix differently. At the end, the ceiling of the S-curve in Exhibit 4 being around 80 percent could be achieved by using only natural gas and nothing else. Alternatively, nuclear energy could be replaced by solar, wind, hydroelectric or a combination thereof, but these technologies are still responsible for insignificant contribution to the energy picture worldwide. Moreover such scenarios would introduce important deviations from the natural paths in the evolution of the market shares of Exhibit 3. In fact, the deviations from model-substitution trends discussed earlier go the wrong way by aggravating the missing-hydrogen problem, one more factor contributing to the pressure that is slowly building up from the delay of hydrogen's introduction.



Hydrogen Content of the Primary-Energy Mix


Exhibit 4. The black dots indicate the evolution of the hydrogen-content percentage according to the energy mix of Exhibit 3. The thick gray line is an S-curve fit to the black dots over the period 1860-2008. The gray area reflects the amount of hydrogen that needs to be provided from non-fossil types of energy.


Interestingly, there is all ready a herald of the approaching hydrogen era: fuel cells. This technology is rapidly picking up momentum and is often mistaken for a solution to the energy question. But fuel cells need hydrogen to run. If hydrogen were readily available, we could just as easily put it in our cars. They would run faster and would produce no undesirable emissions whatsoever.

Another important recent development is catalytic hydrogen production, see project HYDROSOL, which permits extracting hydrogen from water at relatively low temperatures. This technique is of particular interest to countries with sunshine because a modest sun furnace can do the job.3.

* Adapted from a graph that originally appeared in Nebojsa Nakicenovic, 敵rowth to Limits, (Ph.D. diss., University of Vienna, 1984).

* Marchetti has published these molar-ratio estimates in 展hen Will Hydrogen Come? Int. J. Hydrogen

Energy, 10, 215 (1985).