R. Z. Aminov

Assessment of the efficiency of hydrogen cycles on the basis of off-peak electric energy produced at a nuclear power station

The main factors influencing the efficiency of using off-peak electric energy to run hydrogen cycles at a nuclear power station are considered. Indicators characterizing the efficiency of using a hydrogen cycle at a nuclear power station during its operation with superheating live steam in a steam-hydrogen mode are presented. A comparison between the steam-turbine hydrogen cycle and a pumped-storage hydraulic power station in the efficiency of generating peak electric energy (power) and capital investments is given.

Evaluating the thermodynamic efficiency of hydrogen cycles at wet-steam nuclear power stations

Various schematic solutions for implementing a hydrogen cycle on the basis of thermal and nuclear power stations are discussed. Different approaches to construction of cooling systems for the combustion chambers used in hydrogen-oxygen steam generators are described. An example of solution is given in which the combustion chamber is cooled by steam, which is the most efficient one in the thermodynamic respect. Results from an assessment of the thermodynamic efficiency of hydrogen cycles organized on the basis of the power unit of a wet-steam nuclear power station equipped with a K-1000-60/1500 turbine are presented. The thermodynamic efficiency of different schematic and parametric versions of implementing a hydrogen cycle, including those with a satellite turbine operating on displaced steam, is carried out. It is shown that the use of satellite turbines allows the power output and efficiency of the power unit of a wet-steam nuclear power station to be upgraded in a reliable and effective manner.

Efficient ways for setting up the operation of nuclear power stations in power systems in the base load mode

The results obtained from studies of efficient ways and methods for organizing the operation of developing nuclear power stations in the base load mode are presented. We also show comparative efficiency of different scenarios for unloading condensing thermal power stations, cogeneration stations, combined-cycle power plants, nuclear power stations, and using off-peak electric energy for electricity-intensive loads: pumped-hydroelectric storage, electric-powered heat supply, and electrolysis of water for producing hydrogen and oxygen.

Thermal and nuclear power plants: Competitiveness in the new economic conditions

In recent years, the conditions of development and functionality of power generating assets have notably changed. Considering the decline in the price of hydrocarbon fuel on the global market, the efficiency of combined-cycle gas-turbine plants in the European part of Russia is growing in comparison with nuclear power plants. Capital investments in the construction of nuclear power plants have also increased as a result of stiffening the safety requirements. In view of this, there has been an increasing interest in exploration of effective lines of development of generating assets in the European part of Russia, taking consideration of the conditions that may arise in the nearest long-term perspective. In particular, the assessment of comparative efficiency of developing combined-cycle gas-turbine plants (operating on natural gas) in the European part of Russia and nuclear power plants is of academic and practical interest. In this article, we analyze the trends of changes in the regional price of hydrocarbon fuel. Using the prognosis of net-weighted import prices of natural gas in Western European countries—prepared by the International Energy Agency (IEA) and the Energy Research Institute of the Russian Academy of Sciences (ERIRAS)—the prices of natural gas in the European part of Russia equilibrated with import prices of this heat carrier in Western Europe were determined. The methodology of determining the comparative efficiency of combined-cycle gas turbine plants (CCGT) and nuclear power plants (NPP) were described; based on this, the possible development of basic CCGTs and NPPs with regard to the European part of Russia for various scenarios in the prognosis of prices of gaseous fuel in a broad range of change of specific investments in the given generating sources were assessed, and the extents of their comparative efficiency were shown. It was proven that, at specific investments in the construction of new NPPs in the amount of 5000 dollars/kW, nuclear power plants in the European part of Russia become less efficient as compared to CCGTs operating on natural gas.

Estimation of lifespan and economy parameters of steam-turbine power units in thermal power plants using varying regimes

The use of potent power units in thermal and nuclear power plants in order to regulate the loads results in intense wear of power generating equipment and reduction in cost efficiency of their operation. We review the methodology of a quantitative assessment of the lifespan and wear of steam-turbine power units and estimate the effect of various operation regimes upon their efficiency. To assess the power units’ equipment wear, we suggest using the concept of a turbine’s equivalent lifespan. We give calculation formulae and an example of calculation of the lifespan of a steam-turbine power unit for supercritical parameters of steam for different options of its loading. The equivalent lifespan exceeds the turbine’s assigned lifespan only provided daily shutdown of the power unit during the night off-peak time. We obtained the engineering and economical indices of the power unit operation for different loading regulation options in daily and weekly diagrams. We proved the change in the prime cost of electric power depending on the operation regimes and annual daily number of unloading (non-use) of the power unit’s installed capacity. According to the calculation results, the prime cost of electric power for the assumed initial data varies from 11.3 cents/(kW h) in the basic regime of power unit operation (with an equivalent operation time of 166700 hours) to 15.5 cents/(kW h) in the regime with night and holiday shutdowns. The reduction of using the installed capacity of power unit at varying regimes from 3.5 to 11.9 hours per day can increase the prime cost of energy from 4.2 to 37.4%. Furthermore, repair and maintenance costs grow by 4.5% and by 3 times, respectively, in comparison with the basic regime. These results indicate the need to create special maneuverable equipment for working in the varying section of the electric load diagram.

Calculating the Caloric Properties of Dissociated Steam at High Temperatures

Lookup tables and the hs-diagram of the caloric parameters of dissociated steam are drawn up in the temperature and pressure ranges 1250–4000 K and 0.1–10 MPa for calculating the processes in thermal power installations that use dissociated steam as working fluid. Unlike the existing tables for thermophysical properties of dissociated steam, the enthalpy presented in the proposed tables has positive values in the entire range of the considered parameters. The enthalpy of mixture includes the entire energy spent in the chemical reaction of dissociation for breaking the bonds in steam molecules. The caloric parameters are determined from the reference temperature equal to 0°C adopted in the methods for calculating the parameters of nondissociated steam, due to which it becomes possible to carry out coordinated calculations of processes in thermal power installations. Supplements to the existing tables for calculating the above-mentioned caloric parameters are developed. Dissociated steam expansion processes are calculated for the conditions with and without recombination of dissociation products at the same values of initial parameters and final pressure. It has been determined that the change of enthalpy and the work done in the expansion process without recombination are smaller than they are in the process involving recombination of dissociation products. The error of the performed calculations of caloric parameters is less than 0.1%.

Equations for calculating the properties of dissociated steam

The equations of state for dissociated steam have been developed in the temperature and pressure ranges of 1250–2300 K and 0.01–10.00 MPa for calculating thermodynamic processes in thermal power units operating on high-temperature steam. These equations are based on the property tables for dissociated steam derived at a reference temperature of 0 K. It is assumed that the initial substance is steam, the dissociation of which—in accordance with the most likely chemical reactions—results in formation of molecules of hydrogen, oxygen, steam, hydroxyl, and atoms of oxygen and hydrogen. Differential thermodynamic correlations, considering a change in the chemical potential and the composition of the mixture, during the steam dissociation are used. A reference temperature of 0.01°С used in the calculation of parameters of nondissociated steam has been adopted to predict processes in thermal power units without matching the reference temperatures and to account for transformation of dissociated steam into its usual form for which there is the international system of equations with the water triple point of 0.01°С taken as the reference. In the investigated region, the deviation of dissociated steam properties from those of nondissociated steam, which increases with decreasing the pressure or increasing the temperature, was determined. For a pressure of 0.02 MPa and a temperature of 2200 K, these deviations are 512 kJ/kg for the enthalpy, 0.2574 kJ/(kg K) for the entropy, and 3.431 kJ/(kg K) for the heat capacity at constant pressure. The maximum deviation of the dissociated steam properties calculated by the developed equations from the handbook values that these equations are based on does not exceed 0.03–0.05%.

Optimization of the operating conditions of gas-turbine power stations considering the effect of equipment deterioration

In recent years in most power systems all over the world, a trend towards the growing nonuniformity of energy consumption and generation schedules has been observed. The increase in the portion of renewable energy sources is one of the important challenges for many countries. The ill-predictable character of such energy sources necessitates a search for practical solutions. Presently, the most efficient method for compensating for nonuniform generation of the electric power by the renewable energy sources—predominantly by the wind and solar energy—is generation of power at conventional fossil-fuel-fired power stations. In Russia, this problem is caused by the increasing portion in the generating capacity structure of the nuclear power stations, which are most efficient when operating under basic conditions. Introduction of hydropower and pumped storage hydroelectric power plants and other energy-storage technologies does not cover the demand for load-following power capacities. Owing to a simple design, low construction costs, and a sufficiently high economic efficiency, gas turbine plants (GTPs) prove to be the most suitable for covering the nonuniform electric-demand schedules. However, when the gas turbines are operated under varying duty conditions, the lifetime of the primary thermostressed components is considerably reduced and, consequently, the repair costs increase. A method is proposed for determination of the total operating costs considering the deterioration of the gas turbine equipment under varying duty and start–stop conditions. A methodology for optimization of the loading modes for the gas turbine equipment is developed. The consideration of the lifetime component allows varying the optimal operating conditions and, in some cases, rejecting short-time stops of the gas turbine plants. The calculations performed in a wide range of varying fuel prices and capital investments per gas turbine equipment unit show that the economic effectiveness can be increased by 5–15% by varying the operating conditions and switching to the optimal operating modes. Consequently, irrespective of the fuel price, the application of the proposed method results in selection of the most beneficial operating conditions. Consideration of the lifetime expenditure included in the optimization criterion enables enhancement of the operating efficiency.

The effectiveness of power-generating complexes constructed on the basis of nuclear power plants combined with additional sources of energy determined taking risk factors into account

The effectiveness of combining nuclear power plants equipped with water-cooled water-moderated power-generating reactors (VVER) with other sources of energy within unified power-generating complexes is analyzed. The use of such power-generating complexes makes it possible to achieve the necessary load pickup capability and flexibility in performing the mandatory selective primary and emergency control of load, as well as participation in passing the night minimums of electric load curves while retaining high values of the capacity utilization factor of the entire power-generating complex at higher levels of the steam-turbine part efficiency. Versions involving combined use of nuclear power plants with hydrogen toppings and gas turbine units for generating electricity are considered. In view of the fact that hydrogen is an unsafe energy carrier, the use of which introduces additional elements of risk, a procedure for evaluating these risks under different conditions of implementing the fuel-and-hydrogen cycle at nuclear power plants is proposed. Risk accounting technique with the use of statistical data is considered, including the characteristics of hydrogen and gas pipelines, and the process pipelines equipment tightness loss occurrence rate. The expected intensities of fires and explosions at nuclear power plants fitted with hydrogen toppings and gas turbine units are calculated. In estimating the damage inflicted by events (fires and explosions) occurred in nuclear power plant turbine buildings, the US statistical data were used. Conservative scenarios of fires and explosions of hydrogen-air mixtures in nuclear power plant turbine buildings are presented. Results from calculations of the introduced annual risk to the attained net annual profit ratio in commensurable versions are given. This ratio can be used in selecting projects characterized by the most technically attainable and socially acceptable safety.

The comparative effectiveness of serving peak loads in the variants of providing nuclear power plants with a base load

The present paper reports the results of an investigation into the effectiveness of serving peak loads in the variants of providing nuclear power plants with a base load through unloading condensing power plants, combined heat and power (CHP) plants, combined-cycle thermal power plants during night-time off-peak hours, the use of the off-peak electric power for power and heat supply, and water electrolysis with the use of hydrogen and oxygen for production of the peak electric power, as compared with the variant of the development of pumped storage hydropower plants.