The Energy Utilization Rate

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The energy utilization rate throughout the ages can only be estimated in a rough manner. In early times, man was totally nontechnological, not even using fire. He used energy only as food, probably at a rate somewhat below the modern average of 2000 kilocalories per day, equivalent to 100 W. Later, with the discovery of fire and an improved diet involving cooked foods, the energy utilization rate may have risen to some 300 W/capita.

In the primitive agricultural Mesopotamia, around 4000 B.C., energy derived from animals was used for several purposes, especially for transportation and for pumping water in irrigation projects. Solar energy was employed for drying cereals and building materials such as bricks. Per capita energy utilization may have been as high as 800 W.

The idea of harnessing wind, water and fire to produce useful work is ancient. Wind energy has been in use to drive sailboats since at least 3000 B.C. and windmills were described by Hero of Alexandria around 100 A.D. Extensive use of windmills started in Persia around 300 A.D. and, only much later, spread to China and Europe.

Hero described toy steam engines that apparently were built and operated. Vitruvius, the famous Roman architect and author whose book, first published at the time of Hero, is still on sale today, describes waterwheels used to pump water and grind cereals.

In spite of the availability of the technology, the ancients limited themselves to the use of human or animal muscle power. Lionel Casson (1981), a professor of ancient history at New York University, argues that this was due to cultural rather than economic constraints and that only at the beginning of the Middle Ages did the use of other energy sources become "fashionable." Indeed, the second millennium saw an explosion of mechanical devices starting with windmills and waterwheels.

The energy utilization rate in Europe was likely 2000 calories per capita around 1200 A.D. when there was widespread adoption of advanced agriculture, the use of fireplaces to heat homes, the burning of ceramics and bricks, and the use of wind and water. Since the popular acceptance of such activities, energy utilization has increased rapidly.

Figure 1.2 illustrates (a wild estimate) the number of kilowatts utilized per capita as a function of the date. If we believe these data, we may conclude that the annual rate of increase of the per capita energy utilization rate behaved as indicated in Figure 1.3. Although the precision of these results is doubtful, it is almost certain that the general trend is correct— for most of our history the growth of the per capita energy utilization rate was steady and quite modest. However, with the start of the industrial revolution at the beginning of the 19th century, this growth accelerated dramatically and has now reached a worrisome level.


EUROPE / (industrial) /

MESOPOTAMIA J (primitive l agriculture) /



/ / J NEUROPE (advanced —----agriculture)


1500 1750 2000 Year

Figure 1.2 A very rough plot of the his- Figure 1.3 The annual rate torical increase in the per capita energy of increase of per capita energy utilization rate. utilization was small up to the

19th century.

One driving force behind the increasing worldwide per capita energy utilization was the low cost of oil before 1973 when the price of oil was substantially lower than what it is currently. t Perez Alfonso, the Venezuelan Minister of Oil in 1946, was among those who recognized that this would lead to future difficulties. He was instrumental in creating OPEC in 1954, not as a cartel to squeeze out higher profits but to "reduce the predatory oil consumption to guarantee humanity enough time to develop an economy based on renewable energy sources." Alfonso also foresaw the ecological benefits stemming from a more rational use of oil.

OPEC drove the oil prices high enough to profoundly alter the world economy. The result was that the overall energy utilization rate slowed its increase. Owing to the time delay between the price increase and the subsequent response from the system, several years elapsed before a new equilibrium was established in the oil markets. The result was a major overshooting of the oil producing capacity of OPEC and the softening of prices that we witnessed up to the 1991 Iraqi crisis.

The recent effort of less developed countries (LDCs) to catch up with developed ones has been an important factor in the increase in energy demand. Figure 1.4 shows the uneven distribution of energy utilization rate throughout the world. 72% percent of the world population uses less than 2 kW/capita whereas 6% of the population uses more than 7 kW/ capita.

t In 1973, before the OPEC crisis, petroleum was sold at between $2 and $3 per barrel. The price increased abruptly traumatizing the economy. In 2000 dollars, the pre-1973 petroleum cost about $10/bbl (owing to a 3.8-fold currency devaluation), a price that prevailed again in 1999. However, in 2004, the cost had risen to over $50/bbl.

J. P. Charpentier

% of Total Population

J. P. Charpentier

% of Total Population


Figure 1.4 Most countries use little energy per capita while a few developed ones use a lot.


Figure 1.4 Most countries use little energy per capita while a few developed ones use a lot.

There is a reasonable correlation between the total energy utilization rate of a country and its corresponding annual gross national product. About 2.2 W are used per dollar of yearly GNP. Thus, to generate each dollar, 69 MJ are needed. These figures, which are based on 1980 dollars, vary with time, in part owing to the devaluation of the currency, but also due to changing economic circumstances. It fact, it has been demonstrated that during an energy crisis, the number of megajoules per dollar decreases, while the opposite trend occurs during financial crises.

Further industrialization of developed countries may not necessarily translate into an increase of the per capita energy utilization rate—the trend toward higher efficiency in energy use may have a compensating effect. However, in the USA, the present decline in energy utilizationt is due mainly to a change in the nature of industrial production. Energy intensive primary industries (such as steel production) are phasing out owing to foreign competition, while sophisticated secondary industries (such as electronics and genetic engineering) are growing.

Technological innovation has resulted in more efficient use of energy. Examples of this include better insulation in houses and better mileage in cars. Alternate energy sources have, in a small measure, alleviated the demand on fossil fuels. Such is the case of using ethanol from sugar cane for the propulsion of automobiles. It is possible that the development of fusion reactors will, one day, bring back the times of abundant energy.

Introduction of a more efficient device does not immediately result in energy economy because it takes a considerable time for a new device to t

The use of energy by the American industry was less in 1982 than in 1973.

be widely accepted. The reaction time of the economy tends to be long. Consider the privately owned fleet of cars. A sudden rise in gasoline price has little effect on travel, but it increases the demand for fuel efficiency. However, car owners don't rush to buy new vehicles while their old ones are still usable. Thus, the overall fuel consumption will only drop many years later, after a significant fraction of the fleet has been updated.

Large investments in obsolete technologies substantially delay the introduction of more desirable and efficient systems. A feeling for the time constants involved can be obtained from the study of the "market penetration function," discussed in Section 1.7.

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Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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