E-mail: veziroglu@miami.edu
T. Nejat Veziroglu
Clean Energy Research Institute University of Miami, Coral Gables, FL 33124, USA
HYDROGEN ENERGY SYSTEM AS A PERMANENT SOLUTION TO GLOBAL ENERGY - ENVIRONMENTAL PROBLEMS
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ABSTRACT
Fossil fuels (i.e., petroleum, natural gas and coal), which meet most of the world energy demand today, are being depleted fast. Also, their combustion products are causing the global problems, such as the greenhouse effect, ozone layer depletion, acid rains and pollution, which we are posing great danger for our environment and eventually for the life in our planet. Many engineers and scientists agree that the solution to these global problems would be to replace the existing fossil fuel system by the Hydrogen Energy System. Hydrogen is a very efficient and clean fuel. Its combustion will produce no greenhouse gases, no ozone layer depleting chemicals, little or no acid rain ingredients and pollution. Hydrogen, produced from renewable energy (e.g., solar) sources, would result in a permanent energy system, which we shall never have to change.
However, there are other energy systems proposed for the post-petroleum era, such as a synthetic fossil fuel system. In this system, synthetic gasoline and synthetic natural gas will be produced using abundant deposits of coal. In a way, this will ensure the continuation of the present fossil fuel system.
The two possible energy systems for the post-fossil fuel era (i.e., the solar hydrogen energy system and the synthetic fossil fuel system) are compared with the present fossil fuel system by taking into consideration production costs, environmental damages and utilization efficiencies. The results indicate that the solar hydrogen energy system is the best energy system to ascertain a sustainable future.
1. ENERGY RELATED GLOBAL PROBLEMS
Soon after the invention of the steam engine in the 1860's, when the Industrial Revolution started to replace humans' and beasts' toil with nature's energy sources, a bright future seemed to be certain for the humankind. More and more of nature's energy, initially in the form of wood and coal, later as oil and natural gas, were being harnessed for the benefit of humans. This resulted in mass production of goods, with corresponding reduction in prices and rising living standards.
Communities asked for factories, railroads, highways, seaports and airports. These meant more jobs, more income, more goods and more services. The world's standard of living was rising. When the Industrial Revolution started, the annual gross world product per capita was in some tens of dollars; today, it is $6,600 and rising exponentially.
Fossil fuels, which fed this amazing economic growth, were the medicine to cure deprivation. But it was an untested medicine, at that. As the planet Earth consumed more and more fossil fuels, two important predicaments started to emerge: (1) the fossil fuels would be depleted in a foreseeable future, and (2) the fossil fuels and their combustion products were causing global environmental problems.
1.1. Depletion of Fossil Fuels
The demand for energy continues to rise because of two main reasons: (a) the continuing increase in world population, and (b) the growing demand by the developing countries in order to improve their living standards. At the present time, a large portion (about 65%) of the world energy demand is met by the fluid fossil fuels.(i.e., petroleum and natural gas), because of their availability and convenient use. However, it is expected that the world fossil fuel production will soon peak, and thereafter begin to decrease [1-4]*. Figure 1 shows estimates of the production rates of the fossil fuels and the world demand.
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Figure 1. Estimates of World Fossil Fuel Production
It can be seen that the fluid fossil fuel production worldwide will continue to rise for the next 15 years, and then will start to decrease. The coal production - because of the environmental reasons - is expected to remain nearly constant for the next decade and then start to decrease.
Meantime, as a result of the growing world population and the desires of the peoples to better their living stand-
Numbers in square brackets refer to references listed at the end of the paper.
**1 GJ of energy is approximately equal to the energy contained in 3.4 gallons of petroleum.
ards, the world demand for fluid fuels is rising (Fig. 1). It is expected that the world population (which is about 6 billion at the moment and rising at 1.5% per year) growth will slow down and reach about 10 to 12 billions by the end of the next century [5]. Consequently, the world demand for fluid fuels will slow down and reach around 1.6 X 1012 GJ** per year. There will be a growing gap, starting within the next ten years, between the demand and production of fluid fuels.
1.2. Environmental Damage
The second predicament involving the fossil fuels is the environmental damage being caused by the fossil fuels and by their combustion products. Technologies for fossil fuel extraction, transportation, processing and particularly their end use (combustion), have harmful impacts on the environment, which cause direct and indirect negative effects on the economy. Excavation of coal devastates the land, which has to be reclaimed and is out of use for several years. During the extraction, transportation and storage of oil and gas, spills and leakages occur, which cause water and air pollution. Refining processes also have an environmental impact. However, most of the fossil fuel environmental damage occurs during the end use. The end use of all fossil fuels is combustion, irrespective of the final purpose (i.e., heating, electricity production or motive power for transportation). The main constituents of fossil fuels are carbon and hydrogen, but also some other ingredients, which are originally in the fuel (e.g., sulfur), or are added during refining (e.g., lead, alcohols). Combustion of the fossil fuels produces various gases (CO^ SOx, NOx, CH), soot and ash, droplets of tar, and other organic compounds, which are all released into the atmosphere and cause air pollution. Air pollution may be defined as the presence of some gases and particulates which are not a natural constituent of the atmosphere, or even presence of the natural constituents in an abnormal concentration. Air pollution causes damage to human health, animals, crops, structures, reduces visibility, and so on.
Once in the atmosphere, triggered by sunlight or by mixing with water and other atmospheric compounds, the above stated primary pollutants may undergo chemical reactions, change their form and become secondary pollutants, like ozone, aerosols, peroxyacyl nitrates, various acids, etc. Precipitation of sulfur and nitrogen oxides, which have dissolved in clouds and in rain droplets to form sulfuric and nitric acids is called acid rain; but also acid dew, acid fog and acid snow have been recorded. Carbon dioxide in equilibrium with water produces weak carbonic acid. Acid deposition (wet or dry) causes soil and water acidification, resulting in damages to the aquatic and terrestrial ecosystems, affecting humans, animals, vegetation and structures.
The remaining products of combustion in the atmosphere, mainly carbon dioxide, together with other so called greenhouse gases (methane, nitrogen oxides and chlorofluor-ocarbons), result in thermal changes by absorbing the infrared energy the Earth radiates into the atmosphere, and by reradiating some back to Earth, causing global temperatures to increase. The effects of the temperature increase are melting of the ice caps, sea level rise and climate changes, which include heat waves, droughts, floods, stronger storms, more wildfires, etc.
Using the studies by scores of environmental scientists, the above stated damages have been calculated for each of the fossil fuels [6]. Table I presents the results for each type of damage, in 1998 U.S. dollars.
It can be seen that the environmental damage for coal is $14.51 per GJ of coal consumed, for petroleum $12.52 per GJ of petroleum consumed, for natural gas $8.26 per GJ of natu-
ral gas consumed, and the weighted mean damage in the world is $12.05 per GJ of fossil fuel consumption. These damage costs are not included in the prices of fossil fuels, but they are paid for by the people directly or indirectly through taxes, health expenditures, insurance premiums, and through a reduced quality of life. In other words, today fossil fuels are heavily subsidized. If the respective environmental damages were included in the fossil fuel prices, it would force earlier introduction of cleaner fuels, such as hydrogen, with many benefits to the economy and the environment.
In order to see the worldwide dimensions of the fossil fuel environmental damage, Table II has been prepared. It can be seen that 37% of the total damage is caused by coal, while the coal consumption is 31% of the total fossil fuel consumption. On the other hand, only 20% of the damage is caused by natural gas, which has a market share of 29%. It is clear that increasing the natural gas consumption at the expense of coal and petroleum will be environmentally beneficial. This would also prepare the way for greater public acceptance of gaseous fuels, which would result in a smoother change to hydrogen, also a gaseous fuel.
It can also be seen from Table II that the annual worldwide environmental damage caused by fossil fuels is 1998 $4,345 billion, or equal to 11% of the gross world product. This is a very large figure. Conversion to a cleaner fuel, such as hydrogen, would enable the world to save this enormous sum and perhaps use it to improve the quality of life worldwide.
2. REASONS FOR HY
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