Chapter 1
Problems of the Energy Economy

The energy economy of nearly all and, in particular, of the industrialized countries is based on the use of stored energy, mainly fossil energy in the form of coal, oil, and natural gas, as well as nuclear energy in the form of the uranium isotope 235U. Two problems arise when we use our reserves to satisfy our energy needs. A source of energy can continue only until it is depleted. Well before this time, that is, right now at the latest, we have to consider how life will continue after this source of energy is gone and we must begin to develop alternatives. Furthermore, unpleasant side effects accompany the consumption of the energy source. Materials long buried under the surface of the Earth are released and find their way into air, water, and into our food. Up to now, the disadvantages are hardly perceptible, but they will lead to difficulties for future generations. In this chapter, we estimate the size of the fossil energy resources, which, to be precise, are composed not only of fossil energy carriers but also of the oxygen in the air that burns with them. In addition, we examine the cause of the greenhouse effect, which is a practically unavoidable consequence of burning fossil fuels.

1.1 Energy Economy

The amount of chemical energy stored in fossil energy carriers is measured in energy units, some more and some less practical. The most fundamental unit is the joule, abbreviated J, which is, however, a rather small unit representing the amount of energy needed to heat 1 g of water by a quarter of a degree or the amount of energy that a hair drier with a power of 1 kW consumes in 1 ms. A more practical unit is the kilo Watt hour (kWh), which is 3.6 × 106 J. 1 kWh is the energy contained in 100 g of chocolate. The only problem with this unit is that it is derived from the watt, the unit for power, which is energy per time. This makes energy equal to power times time. This awkwardness leads to a lot of mistakes in the nonscience press such as kilowatt per hour for power, because most people mistake kilowatt to be the unit for energy, which they perceive as the more basic quantity. The energy of fossil fuels is often given in barrels of oil equivalents or in (metric) tons of coal equivalents (t coal equiv.).

The following relations apply:

1. 1 kWh = 3.6 × 106 J = 1 kWh
2. 1 t coal equiv. = 29 × 109 J = 8200 kWh
3. 1 kg oil = 1.4 kg coal equiv. = 12.0 kWh
4. 1 m3 gas = 1.1 kg coal equiv. = 9.0 kWh
5. 1 barrel oil = 195 kg coal equiv. = 1670 kWh

The consumption of chemical energy per time is an energy current (power) taken from the energy reserves. Thus, the consumption of one ton of coal per year, averaged over one year amounts to an energy current of

We look at Germany as an example of a densely populated industrialized country. Table 1.1 shows the consumption of primary energy in Germany in the year 2002, with a population of 82.5 × 106. These figures contain a consumption of electrical energy per year of

The energy consumption per capita in Germany of 5.98 kW is very high compared with the energy current of 2000 kcal/d = 100 W = 0.1 kW taken up by human beings in the form of food, representing the minimum requirement for sustaining life.

Table 1.1 Primary Energy Consumption in Germany in 2002

Table 1.2 shows the consumption of primary energy in the world in 2002, with a population of 6 × 109. This energy consumption is supplied from the available reserves of energy with the exception of hydro, wind, and biomass. The current remaining reserves of energy are shown in Table 1.3. This is the amount of energy that is estimated to be recoverable economically with present-day techniques at current prices. The actual reserves may be up to 10 times as large, about 10 × 1012 t coal equiv.

Table 1.2 World Primary Energy Consumption in 2002

Table 1.3 The World's Remaining Energy Reserves

The global energy consumption of 13.2 × 109 t coal equiv. per year appears to be very small when compared with the continuous energy current from the Sun of

that radiates toward the Earth.

In densely populated regions such as Germany, however, the balance is not so favorable if we restrict ourselves to the natural processes of photosynthesis for the conversion of solar energy into other useful forms of energy. The mean annual energy current that the Sun radiates onto Germany, with an area of 0.36 × 106 km2, is about 3.6 × 1014 kWh/a = 4.3 × 1010 t coal equiv./a. Photosynthesis, when averaged over all plants, has an efficiency of about 1% and produces around 400 × 106 t coal equiv./a from the energy of the Sun. This is insufficient to cover the requirements of primary energy of 494 × 106 t coal equiv./a for Germany. What is even more important is that it also shows that over the entire area of Germany plants are not able to reproduce, by photosynthesis, the oxygen that is consumed in the combustion of gas, oil and coal. And this does not even take into consideration that the biomass produced in the process is not stored but decays, which again consumes the oxygen produced by photosynthesis. This estimate also shows that solar energy can cover the energy requirements of Germany over its area only if a substantially higher efficiency for the conversion process than that of photosynthesis can be achieved. The fact that no shortage in the supply of oxygen will result in the foreseeable future is owed to the wind, which brings oxygen from areas with lower consumption. Nevertheless, well before we run out of oxygen we will be made aware of an increase in the combustion product CO2.

1.2 Estimate of the Maximum Reserves of Fossil Energy

For this estimate [1] we assume that neither free carbon nor free oxygen was present on the Earth before the beginning of organic life. The fact that carbon and oxygen react quickly at the high temperatures prevailing during this stage of the Earth's history, both with each other to form CO2 and also with a number of other elements to form carbides and oxides, is a strong argument in support of this assumption. Since there are elementary metals on the surface of the Earth even today, although only in small amounts, it must be assumed that neither free carbon nor free oxygen was available to react.

The free oxygen found in the atmosphere today can therefore only be the result of photosynthesis occurring at a later time. The present-day amount of oxygen in the atmosphere thus allows us to estimate a lower limit to the size of the carbon reserves stored in the products of photosynthesis under the assumption that all oxygen produced by photosythesis is still present as free oxygen.

During photosynthesis, water and carbon dioxide combine to form carbohydrates, which build up according to the reaction

A typical product of photosynthesis is glucose: C6H12O6 = 6 × CH2O. For this compound and also for most other carbohydrates, the ratio of free oxygen produced by photosynthesis to carbon stored in the carbohydrates is

The mass of the stored carbon mC can therefore be found from the mass of free oxygen :

The greatest proportion of the oxygen resulting from photosynthesis is found in the atmosphere and, to a lesser extent, dissolved in the water of the oceans. The fraction in the atmosphere is sufficiently large to be taken as the basis for an estimate.

From the pressure pE = 1 bar = 10 N cm-2 on the surface of the Earth resulting from the air surrounding our planet, we can calculate the mass of air from the relationship mair × g = pE × area:

Multiplying by the surface of the Earth gives the total mass of air

Since air consists of 80% N2 and 20% O2 (making no distinction between volume percent and weight percent), the mass of oxygen is: . The amount of carbon produced by photosynthesis and now present in deposits on the Earth corresponding to the amount of oxygen in the atmosphere is therefore:

There may be even more. The large...