Degradation of the Traditional Steam-Turbine Cycle — the Main Trend in the Development of Global Energy

S. V. Polozhii

(Presented by the scientific seminar of the Department of TEU)

The development of modern energy is based on the use of the traditional steam-power cycle of regions I and II: the traditional cycle of region I in installations with organic fuel of small capacity, in maneuvering power units, and in powerful base-load nuclear power plants; the traditional cycle of region II in powerful unit base-load thermal power plants with supercritical and subcritical pressure. Steam-turbine thermal power plants with the traditional cycle of region I up to superhigh steam parameters have low thermal efficiency and high calculated costs of producing electric power, but they have simple power equipment and high maneuverability, and meet well the requirements of the variable operating regime of power systems. Steam-turbine thermal power plants with the traditional cycle of region II have high thermal efficiency in base-load operation and low calculated costs, have complex power equipment, are non-maneuverable, and do not correspond to the operating conditions of electric power systems in the variable part of load schedules.

The development of energy in the past, at the present stage, and in the future is determined entirely by the objective properties and regularities of the traditional cycle of regions I and II, the disclosure and study of which provide the theoretical basis for technical progress in energy, make it possible correctly to assess the current state and prospects for the development of unit thermal power plants, to reveal the causes of erroneous decisions and forecasting in energy, and the degradation of the traditional cycle of region I in the past and of region II in the future. The development of energy at all stages, especially with the traditional cycle of region II, is characterized by clearly expressed empiricism, without deep theoretical foundations in the development of the traditional cycle or knowledge of the objective laws of its development.

Empiricism in the development of energy is expressed in the adoption of erroneous technical decisions in the construction of unit thermal power plants, in unfounded forecasts of technical progress in energy in the past for the present time and at present for the future. The failure to identify many problems in the development of unit thermal power plants with the traditional cycle of region II, the introduction of units with nonoptimal and technically unacceptable initial steam parameters, and the construction only of base-load thermal power plants without taking into account their transition into the variable part of the load schedules of electric power systems also-

are the result of an empirical approach to the development of power engineering. This explains the failure to foresee the actual results from the introduction into power engineering of unit thermal power stations—such as increases in specific fuel consumption and in calculated costs for the production of electric power as a result of introducing and mastering unit thermal power stations, instead of their reduction from the introduction of such new equipment (USA, England).

In the 1950s, for the 1970s, the use of large thermal power stations at 400–500 ata, 700–750°C was forecast, with low theoretical specific fuel consumption and high efficiency in the development of power engineering. In accordance with such forecasts, in the USA at the beginning of the 1950s construction and operation began of large units with practically inadmissibly high steam parameters of up to 350 ata, 650°C. The objective conditions and possibilities of the traditional cycle of Region II led in practice to the establishment of limiting initial steam parameters and thermal economy for large unit thermal power stations at a significantly lower level, not exceeding 240 ata, 540–560°C, as technically feasible, economically expedient, and operationally acceptably reliable for the operating conditions of such units in base-load mode with a high number of hours of utilization of installed capacity. The further development of units led to the establishment in power engineering of a world “standard” for the initial steam parameters of 240 ata, 540°C.

Power engineers throughout the world over the past 15–20 years have become convinced of the low limiting possibilities of traditional units in improving thermal economy even under base-load operating conditions, and have finally abandoned the original technical solutions and forecasts as not corresponding to the real possibilities of the traditional cycle. The actual time required to master units with the traditional cycle of Region II proved unexpectedly very long, or else it was not possible at all to realize the design performance indicators of units with super-barrier (540–560°C) steam temperature. Also not foreseen were the exceptionally high degree of novelty of supercritical-pressure units, many new problems and difficulties in mastering unit thermal power stations, as well as the inefficient operation of units over many years, high accident rates, and calculated costs for the production of electric power. Uncertainty arose in the time required for mastering, in the reliability of operation of units, and in the achievement of their design performance indicators. All calculated, theoretical, and planned indicators of their operation from technical progress in power engineering were disrupted. Overcoming this period of mastering and operation of unit thermal power stations caused great damage to the development of power engineering in many countries of the world. All this likewise was not regarded as an objective regularity in the development of the traditional cycle of Region II.

In world power engineering there is no concept of dividing the traditional cycle into the first and second regions; there are no studies of the properties and regularities of the traditional cycle and of the inevitable degradation of the traditional cycle of Region II in the developed countries of the world in future power systems. The present stage in the development of world power engineering is characterized by the groundlessness of forecasts for the development of the power engineering of the future, by the failure to identify the final degradation of the traditional cycle of Region II—the continuous increase in specific fuel consumption and calculated costs for the production of electric power in the condensing power stations of the developed countries of the world, associated with the mass transition of thermal power stations into the variable part of the load of power systems.

At the past stage of development of unit thermal power stations, and at the present time, conditions have already been laid for the inefficient operation of future power systems owing to the construction only of large unit thermal power stations for base-load operation,

the mass introduction of such units, the incompatibility of their characteristics with the requirements of the variable operating mode of electric power systems, the technical unsuitability and techno-economic inexpediency of using base-load units in the variable part of the load schedules of power systems, and also the need for the simultaneous development and commissioning of uneconomical, but cheaper, special peak-load and semi-peak-load thermal power plants, while at the same time transferring base-load units into the variable part of the load schedules of electric power systems.

The degradation of the traditional cycle of area II, with the successful assimilation of unit thermal power plants, has manifested itself especially clearly over the last 8–10 years in the electric power industry of the United States. It is expressed in a continuous increase in the specific fuel consumption in U.S. electric power systems over the last decade as compared with fuel consumption in 1963. The actual specific fuel consumption in the United States increased in 1970 over this period by 6–7% (Fig. 1) in connection with the mass transition to unit thermal power plants and the successful assimilation of such units. In the near future, the increase in specific fuel consumption in U.S. electric power engineering will reach maximum values when unit thermal power plants are fully transferred into the variable part of load schedules in connection with the development of base-load nuclear power stations.

The operation of base-load units in the semi-peak and peak portions of the load schedules of electric power systems sharply increases the specific fuel consumption from 330–340 to 400–420 g/kWh. The use for this purpose of special semi-peak steam-turbine thermal power plants or gas-turbine units leads to an even sharper increase in the specific fuel consumption, up to 450–500 g/kWh (Fig. 2). However, the calculated costs of producing electric power at special semi-peak thermal power plants and gas-turbine units are smaller than when base-load units operate in the semi-peak mode (Fig. 3).

Fig. 1. Dynamics of the increase in specific fuel consumption in connection with the degradation of the traditional cycle of area II in the U.S. electric power industry. A — record level of minimum fuel consumption in the U.S. electric power industry; A, B, C — beginning of the degradation of the traditional cycle of area II, increase in specific fuel consumption in the country, decrease in the efficiency of using unit thermal power plants with improved reliability and economy of operation of units in base-load mode; C, D — further degradation of the traditional cycle of area II in future power systems; D, D′, D″ — possible situations in the future development of the U.S. electric power industry according to TPI forecasts in connection with the degradation of the traditional cycle; D — maximum development of nuclear power plants, considerable capacity of maneuverable thermal power plants of low thermal economy, a large share of the operation of unit thermal power plants in the variable part of the load schedules of electric power systems, low or normal capacity reserve in power systems; D′, D″ — low share of nuclear power plants in power systems, low share of peak-load and maneuverable thermal power plants in electric power systems, large capacity reserves, less significant flattening of the load schedules in electric power systems; A′, E, F, K — forecast specific fuel consumption in the U.S. electric power industry from the transition of electric power engineering to large, highly economical units in future U.S. electric power systems without allowance for the degradation of the traditional cycle in the region; A, B, C — actual economy of the U.S. electric power industry from the transition to large SVD and SKD units and their successful assimilation, determined by the degradation of the traditional cycle of area II; BB′ — excess of actual specific fuel consumption in the United States in 1967; CC′ — the same in 1969; BE, CF — excess of specific fuel consumption in 1967 and 1969 relative to that forecast from the introduction of unit thermal power plants in the United States.

The use for this purpose of special semi-peak steam-turbine thermal power plants or gas-turbine units leads to an even sharper increase in specific fuel consumption, up to 450–500 g/kWh (Fig. 2). However, the calculated costs of producing electric power at special semi-peak thermal power plants and gas-turbine units are smaller than when base-load units operate in the semi-peak mode (Fig. 3). The production of electric power in the sharp-peak mode is associated with

even higher specific fuel consumptions, on the order of 550–600 g/kWh. The introduction of special maneuverable thermal power plants of low thermal efficiency proves more advantageous in terms of calculated costs than the operation of base-load units in the variable part of load schedules; but, most importantly, such maneuverable thermal power plants of low thermal efficiency provide a technical solution to the problem of the variable operating regime of power systems, in view of the unsuitability of base-load unit thermal power plants for these purposes.

In the FRG, even at the present time, they are already being forced to abandon the construction of powerful unit thermal power plants with supercritical pressure for base-load operation and to switch to the production of maneuverable units with reduced parameters and low thermal efficiency.

Fig. 2. Increase in the specific fuel consumption by power installations when thermal power engineering is shifted into the variable part of power-system load schedules.
1. Number of hours of utilization of installed capacity. Units K-200, K-300, K-500, and GT-750 according to data of the PEI, Siberian Branch of the USSR Academy of Sciences, and the State Committee for Science and Technology under the USSR Council of Ministers [3]. AF-500 units according to data of TPI.

Fig. 3. Increase in the specific calculated costs for the production of electric energy when thermal power engineering is shifted into the variable part of power-system load schedules.
1. Specific calculated costs for the production of electric energy, kopecks/kWh; 2. Number of hours of utilization of installed capacity, h/year. Units K-200, K-300, K-500, and GT-750 according to data of the PEI, Siberian Branch of the USSR Academy of Sciences, and the State Committee for Science and Technology under the USSR Council of Ministers [3].

low efficiency. In the USA, in the near term, base-load unit thermal power plants with supercritical pressure will be pushed into the variable part of load schedules, with high specific fuel consumptions and calculated costs for the production of electric energy (Figs. 4, 5). Such a prospect for the development of power engineering with the traditional cycle has not been recognized in world practice. The continuous expansion of power engineering by means of powerful base-load thermal power plants continues without taking into account the transition of such units to a variable operating regime, which is unsuitable for these units for either technical or techno-economic reasons. Parameters of 240 ata, 540/540°C are still being forecast for the distant future, when unit thermal power plants will be used with a small number of operating hours per year. The thermal efficiency of such units for conditions of variable operation is excessively high—

is increased; the capital investments for the conditions of their operation in future power systems are unacceptably high.

The damage that may be inflicted on the power engineering of the future by a failure to foresee the objective regularities of the traditional cycle of region II will prove more significant than was the case in the past with the difficulties of assimilating unit thermal power plants in base-load operation with the traditional cycle. The specific fuel consumptions, and especially the estimated costs of producing electric power, will increase substantially in comparison with the present level of already-assimilated unit thermal power plants (USA, FRG), and still more in comparison with the predicted effect of technical progress in power engineering, on the basis of which the development of future power systems is being carried out. Such a directly opposite result from technical progress in power engineering with the traditional cycle of region II in the power systems of the future will also prove—

Fig. 4. Dynamics of the reduction in live-steam temperature and steam reheat temperature (1962–1975) in connection with the degradation of the traditional cycle of region II in U.S. power engineering. 1—live steam; 2—first reheat; 3—second reheat; 4—no second steam reheat; 5—years of commissioning. \(T_{0}^{\mathrm{av}}\)—average live-steam temperature in U.S. power engineering, °C. \(T_{\mathrm{pr}}^{\mathrm{av}}\)—average temperature of the first reheat, °C. \(T_{\mathrm{spr}}^{\mathrm{av}}\)—average temperature of the second steam reheat, °C.

Fig. 5. Dynamics of the change in the initial steam pressure and in the structure of generating capacities in connection with the degradation of the traditional cycle of region II in U.S. power engineering. 1–4. Base-load units: 1—less than 126 ata; 2—126–146 ata; 3—152–184 ata; 4—235–264 ata. 5–6. Maneuvering units: 5—152–184 ata; 6—126–148 ata. 7. Years of commissioning.

unexpected and is the result of empiricism in the development of unit thermal power plants, a consequence of failing to take into account the objective regularities in the development of the traditional cycle of region II. This is the essence of the development of power engineering with the traditional cycle of region II (Fig. 6).

Theoretical studies of the traditional cycle, its properties and regularities, the establishment of the inevitable degradation of the traditional cycle of region II as a law of the development of world power engineering, carried out and identified at the Tomsk Polytechnic Institute in formulating and solving the problem of transferring power engineering to adiabatic phase-foaming—

Fig. 6. Diagram of the objective development of world thermal power engineering in connection with the degradation of the traditional cycle of region II. 1. Level of technical progress in world power engineering. 2. Years of development of power engineering. I—II. Ascending period in the development of power engineering with the traditional cycle. \(A—A'—A''\)—stages in the development of power engineering with the traditional cycle of region I. \(A—B\)—initial period in the development of power engineering with the traditional cycle of region II. \(A''—II_{\text{or}}\)—transition to unassimilable and technically-economically inexpedient large-capacity units in the USA. \(II_{\text{or}}—II\)—rejection of the erroneous decision and transition to optimal units with reduced steam parameters in the USA. \(II—C\)—limiting parameters of units; establishment of the world standard of limiting steam parameters for large-capacity units with the traditional cycle of region II. \(C—III_{\text{op}}\)—erroneous forecast of the 1960s for the 1980s–1990s, with stabilization of modern limiting steam parameters at 240 ata, 540/540°C in future power engineering. \(B—III_{\text{lp}}\)—false forecast of the first period for the 1970s concerning the use of very high steam parameters in power engineering. \(C—III\)—descending period in the development of power engineering in future power systems with the traditional cycle of region II. \(BC\)—period of stabilization and the beginning of a decline in the technical-economic efficiency of US power engineering with the traditional cycle of region II. \(C—III\)—degradation of the traditional cycle of region II in future electric-power systems; mass or 100% transfer of steam-turbine thermal power plants to the variable part of load schedules of electric-power systems; mass introduction of peak and semi-peak thermal power plants with high specific fuel consumption and large calculated costs for producing electric power; decrease—\(P_0, t_0, t_{\text{pp}}, \eta_t, \eta_{oi}, \eta_{ku}\); abandonment of \(t_{\text{pp}}\), HPWH, gas intermediate superheating; increase—\(t_{\text{ex}}, P_k, B_t, Z_{\text{pr}}\). IV—transfer of power engineering to adiabatic phase transformation. \(C—IV\)—progress in thermal power engineering when thermal power plants are transferred to adiabatic phase transformation. \(A—A'—A''—B\)—increase—\(P_0, t_0, t_{\text{pp}}, \eta_t, \eta_{oi}, \eta_{ku}\); decrease—\(t_{\text{ex}}, P_k, b_t, Z_{\text{pr}}\). \(C\)—attainment of the highest degree of perfection of steam-turbine installations with the traditional cycle of region II, of the thermodynamic cycle and heat-flow diagrams, and of minimum calculated costs, specific fuel consumptions, and specific capital investments in the construction of thermal power plants.

…receive brilliant confirmation in recent years in the development of U.S. power engineering. The degradation of the traditional cycle of the second domain in U.S. power engineering has occurred over the last decade in accordance with the incompatibility of the properties and regularities of the traditional cycle of the second domain with the conditions and requirements of power systems at the present and future stages of development of world power engineering. This degradation of the traditional cycle of the second domain is characterized by the following circumstances:

1. A continuous increase in the specific fuel consumption rates over the last 7–8 years at U.S. thermal power plants as power units have been technically improved. In five to ten years, one should expect a further significant rise in the specific fuel consumption rates at U.S. thermal power plants (Fig. 1).

2. An increase in the calculated costs of producing electric power at individual base-load thermal power plants owing to their transfer into the variable part of the load schedules of power systems and the mass operation of special maneuverable thermal power plants under peak and semi-peak load [2–6].

3. A reduction in the construction of highly economical base-load thermal power plants with supercritical steam parameters in U.S. power engineering (Fig. 5), a transition to the construction of uneconomical maneuverable thermal power plants with reduced steam parameters and feedwater temperatures, with simplified boilers and turbines, and other measures aimed at reducing the cost of thermal power plants and increasing their maneuverability.

No branch of world production in the period of a technical revolution, of intensive development of the productive forces, science, and technology is accompanied, in the long term, by a deterioration of techno-economic indicators and an increase in calculated costs, as is observed in the development of thermal power engineering with the traditional cycle of the second domain. This contradicts general progress and requires elimination as an abnormal phenomenon in the development of the productive forces of society.

In recent years, increasing attention has been devoted in all developed countries of the world, and especially in the United States, to questions of the development of power engineering, forecasting, and its trends [14–18]. At the same time, the production of electric power in future power systems is being sought out and optimized on the basis of traditional power installations under conditions of the development of powerful base-load nuclear power plants, the transfer of unit thermal power plants with supercritical steam parameters and supercritical pressure into the variable part of power-system load schedules, and the mass introduction of gas-turbine units for peak load, without global conclusions about the complete degradation of the traditional steam-turbine cycle of the second domain in the near future (Fig. 6).

In U.S. power engineering at the present time, intensive restructuring and changes are being observed in the structure of generating capacities and in the technical characteristics of steam-turbine thermal power plants in accordance with the conditions and requirements of developing power systems at the present and prospective stages [1–3, 17, 18].

In domestic power engineering, as applied to the Unified Electric Power System, solving the problem of optimizing generating capacities and covering the variable part of the load schedule of power systems is a principal problem of exceptional importance [4–6].

The only method known so far for overcoming the degradation of the traditional cycle of the second domain, and the regression of thermal power engineering in the long term, is to transfer it to adiabatic phase formation [7–13].

LITERATURE

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