by Pavel BEZRUKIKH, Cand. Sc. (Tech.), head of Department, RF Ministry of Power Engineering
In recent time renewable energy sources have been attracting more and more attention. One of the main reasons for that has been the looming threat of an energy crisis. As experts point out, the global reserves of oil amount to not more than 400 bin t, and the annual volume of extraction approaches 3 bin t. And that means that at the present technological level of oil extraction and at the current level of oil prices these natural resources will last for no more than 50 to 75 years. And the situation is a very similar with natural gas. Coal reserves alone are big enough to meet our needs for the next 400 to 500 years. And the obvious conclusion is that we have to develop what experts call renewable power production, or renewable energetics, at the maximum possible rate.
The problem of development and utilization of renewable power sources is important for all countries. For some, especially industrially advanced states, which depend on fuel-and-energy imports, this, above all, is a problem of what one could call energy security. For others, with plenty of natural fuel resources-of greater importance is the ecological factor. And the most important factor for the developing countries is rapid, reliable and environment-friendly way of industrial development which can also help improve social welfare. And as for mankind in general, the use of renewable sources of energy is a clear guarantee of consistent progress.
According to the International Energy Agency, the total energy production in the world in 1999 reached 10.64 bin t in the oil equivalent, or 15.2 bin t of conventional fuel (c.f.). And the share of the "exhaustible" types amounted to 81.3 percent or 12.63 bin t c.f. At the same time, according to expert assessments, the world economic potential of renewable energy sources amounts to 19.5 bin t c.f. And that means that it is 1.55 times greater than the annual output of conventional exhaustible fuel. However, to give an example, in 1999 in the countries of the European Union the share of renewable sources of energy in electricity production (without hydrostations) was 2.69 percent, in the United States-2.21 percent and in Russia-0.24 percent. The objective of the European Union now is to obtain 22 percent of the required electri- city with the help of renewable energy sources.
Having said that, what is the current status and development prospects of different types of renewable energy sources?
LOW-CAPACITY HYDROELECTRIC INDUSTRY
To begin with, one has to point out that, according to the Russian rating, what are called micro-hydroelectric power stations (HPS) include stations or generators of up to 100 kWt and what are called minor or small ones-from 100 kWt to 30 MWt. At the present time these stations produce of the order of 10 percent (70 GWt in the year 2000) of the amount of electricity generated bybigHES.
Hydroenergetics, with its age-old history-is one of the most effective areas of utilization of renewable sources of energy, at the unit cost of a unit of HPS capacity of 1,200 - 3,000 dollars/ kWt, the cost of electricity is within 3 - 5 cents per kWt/h.
According to GOSKOMSTAT (State Committee on Statistics) Russia had 59 small hydrostations in the year 2000. Their aggregate capacity reached 513 MWt and annual electricity output was 2.3 bin kWt/h.
Over the next few years the leaders in the development of "minor" hydroenergetics will be Russia, China, India and Latin American countries. And Europe, too, expects to boost hydroenergy output from such hydroelectric power stations. As for our own country, it will have to be dealing with the following problems in this field: find constructive solutions providing for the operation of hydroelectric power (HPS) stations on small rivers in winter time; examine the possibilities of functioning of such small stations in the presence of thick layers of ice on such rivers; develop submersible free-flow and floating micro-HPS with the capacity of 1, 2, 5 and 10 kWt; develop design and structural solutions for reducing the specific costs of building such stations while providing for the minimum negative impact on shoals of spawning fish.
SOLAR THERMAL ENERGETICS
In this situation the energy supplied by our luminary, transformed into heat, is used for heating and hot-water supply of homes and industrial premises, drying of farm produce, etc. This process is implemented with the help of special collectors (liquid or air). In the year 2000 more than 70 mln m 2 of such units were functioning in the world and this figure will be doubled by 2005.
The scale of utilization of what we call solar collectors in countries with a large number of clear days in a year is really not surprising: USA (18 mln m 2 ), Japan (11), China (17.5), Israel (4.35), Australia (3.9), Greece (2.815), Cyprus (0.75 mln m 2 ). But even in places with not so much sunshine the scale of utilization of such collectors is also impressive: Germany (3.1 mln m 2 ), Austria (1.6) and Denmark (0.297 mln m).
Solar heating units and units for hot water supply represent an ecologically clean source of energy which have no restrictions either in different climates, or in different applications (homes, showers, swimming pools, etc.).
In Russia today solar heat energetics leave much to be desired. That is why of importance to us in the predictable future will be problems of technical perfection of such units on the basis of liquid solar collectors and reducing their
costs; development of air collectors and, on their basis, of systems of heating, hot- water supply (especially important for Siberia and the Far East); development of units with solar heat collectors for the production of hot water and electricity on steam-and- water generators.
The heat of the Earth has been used since long ago for the production of electricity and thermal energy (heating, hot water supply). From 1940 to 2000 the aggregate capacity of geo-thermal electric stations in the world rose from 130 to 7,974 MWt, or by 61 times. From 1995 to 2000 the growth reached 17 percent, i.e. by little more than 3 percent a year. The clear leaders in this respect have been the United States (2,228 MWt), Philippines (1909), Italy (785), Mexico (755), Indonesia (589.5), Japan (546.9) and New Zealand (437 MWt).
In Russia, the geothermal energetics statistics have so far been unimpressive. Put into operation in 1977 were three power units-located on the Kamchatka-Mutnovskaya geoelectric station (12 MWt) and in October 2002-two more (25 MWt each). In order to increase the scale of energetics of this kind it is necessary to develop the appropriate equipment and build a geothermal unit operating on the basis of a twin- circuit basis and geothermal heat-supply systems on the basis of heat pumps.
ENERGY OF BIOMASS
The registered capacity of electric stations using biomass in the world today approaches 30 GWt. According to expert forecasts this should be trebled by the year 2010.
These are several technologies of such energy production: burning of biomass, gasification, production of liquid fuel and biogas. The latter is practiced at smaller units for processing of domestic and agricultural wastes at small private farms. The total number of such units was over 6 mln (most of them in China and India). At the same time the number of big units for the processing of urban and industrial wastewater now exceeds 10,000. Over the past few years there have appeared many powerful "combined" factories for the processing of wastes from animal farms and farmsteads. Biogas produced by these units can be used for domestic applications, in water-heating and steam boilers and also in diesel-generators, and gas-turbine generators of electricity.
Among other technologies using biomass a prominent place belongs to electric stations burning solid urban wastes (USA, Denmark, Italy).
At the stage of what we call "experimental-industrial" operation now there are units fuelled by timber from special-
ly cultivated "energy" forests. Widely used today are wastes from timber-processing and logging operations (Scandinavian countries) producing heat and electricity by direct incineration or gasification.
Operating now (Germany, Czechia, etc.) are scores of mechanical units producing "biodiesel fuel" from rape-seed. Also being built are pilot-plant units for the production of liquid fuel by the method of "rapid pyrolysis" of biomass. Being heated at the rate of over 10 3 C/s it is produced in volumes of up to 75 percent of the dry weight of the input raw.
Summing it up, among the renewable energy sources the main share falls on the biomass. In future it can play the decisive role in the replacement of petroleum products. Its applications are especially important in farming, wood-processing and pulp-and-paper industries and also in municipal services in big cities.
From all the renewable energy sources the most rapid progress has been registered in photoenergetics. Over the past 5 years alone the annual growth of production of the required photocells reached 25 - 30 percent. In the year 2000 the aggregate capacity of solar photoelectric modules produced in the world reached 260 MWt. Over a period of 5 years it will increase by 2.5 times and 10 years later it will be trebled. The leaders are Japan (80 MWt in the year 2000), the United States (60), Germany (50), India (47 MWt). In Russia, unfortunately, the output does not exceed 3 MWt.
Dropping down at the same time in the world is the per-unit cost of photoenergetics. Over the past 50 years, for example, it dropped from 1,000 dollars/Wt (1950) to 4 - 5 dollars/Wt (2000). This represents truly colossal progress. But even to this day this is the most expensive source of renewable energetics and this is despite the efforts by experts in many countries to bring down the net unit/cost.
The development of this renewable energy source is promoted to a large extent by the fact that it can supply with electricity all kinds of users (from fractions of watt to hundreds of kilowatts-from domestic appliances to powerful coastal beacons, radio and TV stations, residential areas, offices, street lighting, etc.). It boasts some attractive working characteristics: "dependability" of batteries which have no spinning parts; longevity of photocells (25 - 30 years); complete automation; zero noise, relative ease and simplicity of installation (no need for heavy lifting cranes); low operating costs; ecological cleanness (photocells are the only source of electricity which can be used without any restrictions in wild-life preserves, recreational areas, etc.).
The progress of photoenergetics in Russia depends on coping with the industrial production of low-cost ecologically-safe techniques of production of silicon of "solar" grade (purity of 0.999) with a reduction of the cost of the raws by two and more times; boosting the efficiency of solar cells up to 20 - 25 percent; development of units with optical "concentrators" which do not require "tracking" of the sun.
Over the past 16 years the summary capacity of wind-powered generators in the world increased from 1,097 to 24,000 MWt. A record was set up in 2001 when the above figure increased by 35 percent over the level of the year 2000. Over the past four years the recent absolute leader in the field- the United States-lost its position in favor of Germany. The aggregate capacity of such units there in 2001 reached 8.754 GWt. Spain was second (3.337), the United States-third (2.525), Mowed by Denmark (2.417) and India (1.248 GWt).
And a rather optimistic picture can be observed with respect to prices. From 1981 to 2000, for example, the average per unit cost of wind units output dropped from 4,000 to 950 dollars/kWt. In a word, this type of renewable energetics is progressing at an accelerated pace, running ahead of all forecasts and being a competitive, ecologically clean producer of electricity. All these factors add up to its tremendous advantage.
Unfortunately in Russia, as different from other branches of renewable sources of energy, current rate of progress in this field gives ground for apprehensions. Out of our six wind electric stations with the total capacity of 7 MWt only one is operating on a more or less acceptable level-the wind-diesel one on the Bering Island (village of Nikolskoye, Kamchatka Region). The factor of utilization of its rated capacity reached 18.9 percent and all the other such units are far behind in this respect.
To remedy the situation within the shortest possible time it would be necessary to develop units of 16,30,50 and 100 kWt for their autonomous operation, or in conjunction with wind-diesel electric stations. It would also be necessary to set up a system of storage of electricity generated by these units; introduce technologies of medium (100 - 1,000 kWt) and greater capacity; develop inverters * of 1, 2, 5 and 10 kWt for guaranteed autonomous energy supply on the basis of wind- and photoelectric units.
And one more thing which has to be mentioned in conclusion. Russia, with its 2.4 percent of the Earth population, possesses 12 percent of the world oil resources, 35 percent of gas, 16 percent of coal and 14 percent of uranium, and that creates an illusion that we are facing no threat of an energy crisis. But this is not so because of the commonly known acute energy problems which appear now and then in a number of regions. This is the reason why our country has to spare no efforts for the development of renewable energetics in order to get by the year 2010 1,200 MWt of electric and 8,200 MWt of thermal power. Coping with this objective win help preserve considerable resources of organic fuels for the future generations, improve considerably power supplies of populated centers located far from electrical networks and improve the situation in ecologically strained regions.
* Inverter-electronic device transforming direct current into alternating one. - Ed.
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