Lecture
In the 20th century, the power used by humans for heating, lighting, transport, industrial and agricultural production, processing and transmission of information, etc., reached on average 2 — 3 kW per person.
Per capita, modern man expends almost 100 times more energy than primitive man.
Thus, in the USA the specific power consumption of non-renewable fossil energy resources per person exceeds 10 — 12 kW per person
At present, humanity satisfies its energy needs mainly through carbon-containing fuels (coal, oil, gas, firewood, shale, peat) and uranium.
From 1973 to 1998, global consumption of energy carriers increased fivefold.
Proven reserves of coal are estimated at 1280 billion tons, oil — 137 billion tons (1993) (66% in the Middle East), gas — 142 trillion m3 (40% in Eastern Europe and the CIS, 36% — in Russia, 32% — in the Middle East (1993 data)).
Projected (unexplored) oil reserves in 1993 were estimated at 100—120 billion tons, coal — 3860 billion tons, gas — 400 trillion m3, including 236 trillion m3 in Russia. In 1995 oil production amounted to 3.32 billion tons per year (the Middle East accounted for 30% of production, the CIS — 13, Russia — 11, the USA — 11%), gas — 2.3 trillion m3 (CIS — 35, Russia — 29, USA — 25%). In 2000, oil production rose to 3.5 billion tons.
Thus, at the current level of oil and gas extraction, their reserves will run out after 2050.
Reserves of 235U uranium, which is used as fuel for thermal-neutron reactors, will be exhausted by 2050.
Alternative energy sources — wind, solar, geothermal energy (energy of hot underground waters), and current (tidal/ocean current) energy — still make an insignificant contribution to world energy production.
Firewood plays an important role in the lives of people in developing countries. According to FAO data, in 1998 more than 2 billion people in the countries of Asia, Africa and Latin America (approximately up to 90% of the rural and more than 30% of the urban population) used wood for cooking and heating. 80% of the wood consumed in developing countries is used for these purposes.
In a typical thermal power plant (TPP), carbon-containing fuel is burned, and under the action of this heat, steam arises in the boiler at a temperature T= 600 °C, which drives a turbine connected to the rotor of a three-phase synchronous generator.
Drawbacks:
1. The need to use flowing water, which is heated by the steam, leads to thermal pollution of the environment. In addition, the generation, transmission and use of electrical energy leads to electromagnetic pollution of the environment. As a result of thermal pollution of the air, the temperature around a TPP rises by 3°C, which leads to increased atmospheric haze and the occurrence of smog. Thermal pollution of the aquatic environment leads to a decrease in the dissolved oxygen content in water and the development of eutrophication processes.
2. The burning of carbon-containing fuels leads to the appearance of carbon dioxide CO2, which is released into the atmosphere and contributes to the creation of the greenhouse effect.
3. The presence of sulfur additives in the coal being burned leads to the formation of sulfur oxides, which enter the atmosphere and, after reacting with water vapor in clouds, create sulfuric acid, which falls to the ground with precipitation. This is how acid precipitation with sulfuric acid arises.
3. Another source of acid precipitation is nitrogen oxides, which arise in TPP furnaces at high temperatures (at ordinary temperatures nitrogen does not react with atmospheric oxygen). These oxides then enter the atmosphere, react with water vapor in clouds and create nitric acid, which falls to the ground together with precipitation. This is how acid precipitation with nitric acid arises. The total worldwide emissions of sulfur and nitrogen oxides amount to 250 million tons annually. In Russia, cases of precipitation with pH = 2.3 have been recorded, which corresponds to the acidity of vinegar. In Russia the affected areas include the Kola Peninsula, Norilsk, and Chelyabinsk.
A coal-fired TPP generating 1 GW = 109 W of electricity consumes 3 million tons of coal annually, releasing into the environment 7 million tons of CO2, 120 thousand tons of sulfur dioxide, 20 thousand tons of nitrogen oxides NO2, and 750 thousand tons of ash.
Nuclear power engineering plays an important role in many countries
In 2000, 437 nuclear power plant units were operating in the world. Electricity is generated at nuclear power plants in 25 countries of the world. In absolute capacity, the USA ranks first (109 reactors), France second (56 reactors), Japan third (51 reactors), Great Britain fourth (35 reactors), and Russia fifth (29 reactors).
The share of nuclear power in electricity generation in different countries was: 15% in our country, 19% in the USA, 28% in Japan, 34% in Germany, 51% in Sweden, 75% in France, and 17% worldwide.
The use of nuclear fuel does not create carbon dioxide CO2 at a nuclear power plant, i.e. does not contribute to the development of the greenhouse effect, nor does it create sulfur and nitrogen oxides that lead to acid precipitation. The calorific value of nuclear fuel is approximately 2 million times higher than that of carbon-containing fuel.
If all nuclear power plants in the world were replaced by TPPs (coal-fired), an additional 600 million tons of coal would be required, and 2 billion tons of carbon dioxide, more than 30 million tons of nitrogen oxides, 50 million tons of sulfur, and 4 million tons of fly ash would enter the environment. The operation of nuclear power plants saves the world 400 million tons of oil annually. The cost of energy at nuclear power plants in our country is 1.5 — 2 times lower than at TPPs. However, per unit of electrical energy produced, nuclear power plants release more heat into the environment than TPPs under comparable conditions. This is due to the lower efficiency of nuclear power plants.
Thermal pollution of the environment by nuclear and thermal power plants can be very significant. In Germany, a prospective plan was considered for the construction of 15 nuclear power plants and 8 thermal power plants in the Rhine basin; however, it turned out that when all the stations came into operation, the temperature in a number of Rhine tributaries would rise to 45 °C, and all life in them would be destroyed.
In addition, the presence of a large number of nuclear power plants leads to the reprocessing (vitrification of waste and burial in deep stable geological formations), transportation and disposal in mines or on the sea floor of large quantities of radioactive decay products capable of destroying all of humanity. Accidents at nuclear power plants, accompanied by the release of radioactive decay products into the atmosphere, also pose a danger to people.
The Chernobyl catastrophe.
The catastrophe at the Chernobyl nuclear power plant made an indelible impression on humanity. Due to design flaws in the reactor and erroneous actions by personnel, at 1:24 a.m. on 26 April 1986 the RBMK reactor of unit four went out of control, an explosion occurred, a fire began, and of the 180 tons of radioactive fuel, about 63 kg of radioactive fission products were thrown into the air, which is approximately 100 times more than the amount of fission products (740 g) in the atomic bomb dropped on Hiroshima. Hundreds of thousands of people were exposed to radiation. The half-life of some isotopes formed as a result of the fission of uranium, for example 131I, is quite short (8 days), while that of others (strontium 90Sr) exceeds 28 years. As a result, the territory around the Chernobyl nuclear power plant became dangerous for life for 300 years.
Radioactive clouds moved towards Europe through Belarus and Poland as far as Scandinavia, and to the south through Kiev, Bulgaria, and Turkey as far as Israel.
More than 2/3 of the radioactive fallout landed in Belarus and covered a fifth of its territory. The gene pool of the nation was placed under mortal threat. Within 5 years after the catastrophe, a 22-fold increase in the incidence of thyroid cancer among children was recorded, and the number of adults with sarcoma (blood cancer) increased 90-fold. The damage caused by Chernobyl to the Republic of Belarus exceeds 200 billion dollars. As a result of the Chernobyl catastrophe, about 58 thousand km2 of territory in Russia was contaminated, where 2 million 650 thousand people live. The greatest amount of radioactively contaminated territory is located in the Bryansk, Kaluga, Tula and Oryol regions. 30 million people found themselves in the affected zone.
As a result, world public opinion's attitude toward nuclear power changed dramatically. The Swedish parliament decided to close its first nuclear power plant in 1998, and its last one by 2010; a similar decision was made in Germany. By 1987, not a single reactor had been built in the USA since 1973. Many states, including Italy, abandoned the construction of new nuclear power plants. However, India, South Korea, Japan, Slovakia, Russia, Iran, Pakistan, Brazil, Ukraine, the Czech Republic, and France continue to build them.
In order to increase the safety of nuclear power plants, academician A.D. Sakharov proposed building them underground, calculating that construction costs would increase by only 20%. In France, safe reactors with two protective shells are being developed. The inner shell is designed to withstand the coolant pressure arising from the destruction of the reactor vessel and to contain fission products and nuclear fuel. The outer shell protects the reactor from external impacts (an aircraft crash, a terrorist act, etc.).
In our country in 1993, hydroelectric power plants generated 175 billion kWh • h of electricity — 18% of the total amount, compared with 12% in the USA. Hydropower is continuously renewed and will exist as long as the Sun's energy reaches the Earth.
However, the operation of hydroelectric power plants has a number of environmental drawbacks:
flooding of land suitable for agriculture (in particular, during the construction of the cascade of hydroelectric power plants on the Volga);
changes in climate in reservoir zones;
disruption of conditions for fish existence and spawning, reduction of fish stocks (in particular, on the Volga and Yenisei);
destruction of a hydroelectric power plant during military action would lead to the release of reservoir water and the occurrence of a wave tens of meters high, which could destroy towns located below the dam;
the construction of hydroelectric power plants leads to induced seismicity; in particular, earthquakes that destroyed hydroelectric power plants have occurred in the USA and India.
1. Solar energy. At present, research on the use of solar energy is being conducted on all continents. In the USA it is expected that by 2020, 10 to 30% of the country's energy needs will be met by solar installations. The flow of solar energy reaching the Earth's surface is 9 thousand times greater than the total energy currently produced in the world using organic fuels and uranium.
Solar energy has a number of advantages. It is available everywhere, practically inexhaustible, and available in the same form for an indefinitely long period of time. To meet its energy needs in 2100, humanity would only need to use less than 0.1% of the solar energy falling on the Earth, or one-fortieth of the solar energy falling on deserts.
Drawbacks. However, solar energy has a low flux density (800—1000 W/m2), and its intensity changes during the day and depends on the season, etc. Both direct and diffuse solar radiation are direct forms of solar energy. Indirect forms of solar energy include wind, wave, and tidal energy, ocean thermal gradients, hydropower, and energy obtained through photosynthesis.
Solar power plants have already been built in Italy and the USA. Their environmental drawbacks are large material costs and disruption of ecological balance beneath the solar panels, which occupy an area of several hectares.
2. Biotechnological fuel. One of the most promising processes for the future appears to be the decomposition of water into hydrogen and oxygen under the action of solar radiation. The fact is that the Earth's water reserves are practically unlimited, and hydrogen is a valuable chemical product that can be used as an environmentally clean fuel that produces no harmful waste. Hydrogen is the best fuel of all known types: in calorific value per unit mass it exceeds natural gas by 2.6 times and oil or gasoline by 3.3 times. In addition, according to a number of scientists, it can be transmitted through pipes over long distances at costs close to the cost of transmitting electrical energy.
Hydrogen can be extracted from water either electrolytically, which is quite expensive, or by a direct chemical (or photochemical) route. However, the visible part of sunlight practically does not decompose water. Therefore, the whole problem comes down to finding suitable catalysts.
3. Wind energy. The use of wind energy is attracting ever more attention, since on a planetary scale wind energy is 1000 times greater than hydropower. In Denmark in 1997, the blades of 4000 wind power plants were turning.
Denmark is the leading country in the use of wind energy. National programs for the development of wind energy have also been launched in the Netherlands, Canada, Germany, France, Sweden, China and other countries.
Experimental work carried out in Germany showed that modern wind power plants (WPPs) optimal in terms of energy output will be gigantic in size: propellers with a blade span of 80—100 m are to rotate on 90-meter towers, driving the rotors of the WPP's electric generators. The towers must be spaced 300 m apart, so WPPs now occupy large areas.
The main environmental drawback of WPPs is noted to be the infrasound noise they generate, which causes a constant state of depression, a feeling of discomfort and anxiety. As the experience of operating such installations in the USA shows, neither animals nor birds can tolerate this noise. Territories where high-power WPPs are located turn out to be practically unfit for habitation.
1500 wind installations of various capacities have been built in Russia. In our country it is advisable to use WPPs in the Kaliningrad region, on the coasts of the Caspian and Black Seas, on Lake Baikal, in Kamchatka and Sakhalin, and on the coast of the Arctic Ocean.
4. Geothermal power engineering based on thermal (hot underground) waters is developing quite intensively in the USA, the Philippines, Mexico, and Japan, where geothermal power plants have been built. In Russia, large geothermal energy resources are available in Kamchatka, Sakhalin and the Kuril Islands, and smaller ones in the Caucasus. Geothermal energy can be used in agriculture (heating greenhouses) and in municipal utilities (hot water supply).
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