Feedwater Heater Research Articles

Thermodynamic, economical and environmental performance evaluation of a 330 MW solar-aided coal-fired power plant located in Niger

The integration of solar thermal energy into a coal-fired power plant is one of the best ways to reduce the environmental impact of the latter linked to the release of carbon dioxide (CO2) into the atmosphere. In this paper, solar energy is used before the boiler, just after the first high-pressure feed water heater via a solar preheater (Water/Heat Transfer Fluid exchanger). It should be noted that in this study, there is no feed water heater displacement, and so the plant will operate in pure fuel-saving mode. To carry out an analysis of the integration of solar thermal energy in a coal-fired power plant, a 330 MW Solar Aided Coal Power Plant (SACPP) in northern Niger was studied. The results bring out that the annual solar energy production is 208 GWh, and solar energy can contribute up to approximately 15 % in the production of electricity. The considered SACPP significantly reduces the environmental impact of coal-fired power plants, leading to a reduction in CO2 emissions of around 381358 tons/year. In addition, the annual energy production cost from solar energy in the hybrid system is obtained as 0.0357 $/kWh and the investment payback period is around 12 months.

A Reduced-Order Model of a Nuclear Power Plant with Thermal Power Dispatch

This paper presents reduced-order modeling of thermal power dispatch (TPD) from a pressurized water reactor (PWR) for providing heat to nearby heat consuming industrial processes that seek to take advantage of nuclear heat to reduce carbon emissions. The reactor model includes the neutronics of the reactor core, thermal–hydraulics of the primary coolant cycle, and a three-lump model of the steam generator (SG). The secondary coolant cycle is represented with quasi-steady state mass and energy balance equations. The secondary cycle consists of a steam extraction system, high-pressure and low-pressure turbines, moisture separator and reheater, high-pressure and low-pressure feedwater heaters, deaerator, feedwater and condensate pumps, and a condenser. The steam produced by the SG is distributed between the turbines and the extraction steam line (XSL) that delivers steam to nearby industrial processes, such as production of clean hydrogen. The reduced-order simulator is verified by comparing predictions with results from separate validated steady-state and transient full-scope PWR simulators for TPD levels between 0% and 70% of the rated reactor power. All simulators indicate that the flow rate of steam in the main steam line and turbine systems decrease with increasing TPD, which causes a reduction in PWR electric power generation. The results are analyzed to assess the impact of TPD on system efficiency and feedwater flow control. Due to the simplicity of the proposed reduced-order model, it can be scaled to represent a PWR of any size with a few parametric changes. In the future, the proposed reduced-order model will be integrated into a power system model in a digital real-time simulator (DRTS) and physical hardware-in-the-loop simulations.

Performance Analysis and Techno-Economic Evaluation of Solar Energy Retrofitting for Coal-Fired Power Plant in Central Kalimantan Province

The power generation sector significantly contributes to climate change. Mitigation efforts are crucial to adhering to the global commitment to limit temperature increases below 2°C. One potential solution is retrofitting existing power plants with technologies that integrate renewable energy. This study explores the integration of solar energy into the operational processes of a coal-fired power plant in Central Kalimantan, replacing the extraction steam turbine in the high-pressure feed water heater No. 7. Using STEAG EBSILON for simulation, this research evaluates the power plant's performance before and after retrofitting in both power-boost (PB) and fuel-save (FS) modes under varying load conditions. The results demonstrate that thermal efficiency in both PB and FS modes increased by up to 2% compared to the base scenario. Specific fuel consumption decreased by 15.05 g/kWh in PB mode and 15.75 g/kWh in FS mode, leading to a reduction in coal consumption and CO2 emissions by 4.69% and 4.94% respectively. Additionally, the study observed that the solar percentage and solar-to-electricity efficiency increased as the load decreased. In FS mode, the solar electricity proportions at VWO, 100%, 75%, and 50% load rates were 5.23%, 5.53%, 7.76%, and 11.92%, respectively. The levelized cost of energy (LCOE) for solar electricity was calculated to be 431.82 IDR/kWh, with an expected investment return period of 5.87 years.

Numerical modeling of discharge modes and evaluation of the major characteristics of latent heat thermal energy storage at a nuclear power plant

Under conditions of uneven power consumption schedules, construction of renewable power plants and low maneuverability of nuclear power plants (NPPs), combining NPPs with latent heat thermal energy storage systems (LHTES) can improve efficiency and maneuverability of NPPs. Combination of the LHTES with an additional low-capacity steam turbine will allow not only meeting peak electricity loads, but also increase the NPP safety by additional reservation of its own needs using this multifunctional turbine in emergency situations of complete blackouts. A scheme for combining a PCM-based thermal storage system with a two-circuit nuclear power plant is proposed, where the LHTES is charged with part of fresh steam from steam generators in the night hours of off-peak loads in the power grid and heating feed water above the nominal temperature during the peak loads. Non-stationary heat transfer between the heat storage material and feed water during the LHTES discharge was modeled using the finite volume method. The design characteristics of the LHTES as part of the NPP and the weight-size parameters of the thermal accumulator have been determined. The rational phase change material and the types of finned tubes have been determined. A solution has been proposed to ensure stable water temperature at the outlet of the PCM-based thermal accumulator during its discharge within the NPP that will significantly increase efficiency of its performance. Heat losses from the LHTES to the environment during the day have been calculated.

A novel design of multilevel disk-type axial flux eddy current heating (AFECH) device: A sustainable approach for feed water heating in reverse osmosis desalination

A novel design of multilevel disk-type axial flux eddy current heating (AFECH) device: A sustainable approach for feed water heating in reverse osmosis desalination

Techno‐economic and carbon footprint analyses of steam Rankine cycle

AbstractSteam Rankine cycle (SRC), which is mainly utilised in power generation sector, faces external irreversibility in its daily operation causing inefficiency in the system. To address this issue, reheat Rankine cycle (RHRC) and regenerative Rankine cycle (RRC) have been widely studied and implemented in power plants to improve thermal efficiency and reduce external irreversibility of Rankine cycle. This study investigates the implementation of different RRC configurations in a combined heat and power plant, including RRC with modified thermal deaerator, RRC with open feed water heater (OFWH) and closed feed water heater (CFWH). A base case simulation model was first constructed using commercial simulation software Aspen HYSYS for the basic SRC system based on actual plant data. Various scenarios were then evaluated for their profitability and sustainability through techno‐economic analysis (TEA) and carbon footprint analysis (CFA). From both analyses, the scenario of RRC with CFWH showed the greatest long‐term potential, generating the highest annual profit of $ 771 691 and carbon footprint reduction of 14.63%, while RRC with modified thermal deaerator showed the greatest potential in the short run with the highest return of investment (ROI) of 201.51% and shortest payback period (PBP) of 0.50 year.

PENGARUH PERUBAHAN TERMINAL TEMPERATUR DIFFERENCE (TTD) DAN DARIN COOLER (DCA) FEED WATER HEATER TERHADAP PERFORMA PLTU MENGGUNAKAN SIMULASI CYCLE TEMPO 5.1

Feedwater heater (FWH) performance can be monitored periodically by reviewing the terminal temperature difference (TTD) and drain cooler approach (DCA) values. Monitoring this value by comparing the actual condition and the value resulting from commissioning. The lower the TTD and DCA values, the better the work effectiveness of FWH. In general, the TTD value ranges between 2.8 ºC to -2.8 ºC while the DCA is between 5.6 ºC to 1 ºC. In this research, modeling was carried out using a cycle tempo simulation of the Molotabu Gorontalo 2 x 12.5 MW PLTU generator to review how much influence the changes in TTD and DCA values ​​of the low feedwater and hight feedwater heaters have. The variations used respectively are TTD with a value (°C) of 2.8; 2; 0; -2 and -2.8 while DCA) respectively (°C) 5.6; 5; 4 ; 3; 2 and 1. The aim of the research is to find out how heat transfer occurs in the two FWHs resulting from modeling and its effect on the Net Plant Hear Rate (NPHR) and the efficiency of the PLTU system. Based on the simulation results obtained using variations of TTD and DCA on the low feedwater heater, the heat transfer in the heater is 144830 kW and 1761.48 kW. Meanwhile, the high feedwater heater produces heat transfer to the heater of 3400.13 kW and 3795.24 kW. As for energy balance, the lowest gross power was 26.32% and the highest was 26.5%. Based on the analysis results, the highest NPHR value was 21634.24 kg/kJ/h, getting an efficiency value of 25.87%. while the lowest NPHR is 25130.43 kg/kJ/h low NPHR produces the highest efficiency of 26%.

Hybrid geothermal-fossil power cycle analysis in a Polish setting with a focus on off-design performance and CO2 emissions reductions

Growing demand for electricity due to economic development contributes to increased greenhouse gas production, especially CO2. However, emissions can be limited by enhancing the efficiency of primary energy conversion, such as integrating geothermal energy into coal-fired power plants. Therefore, this paper proposes replacing conventional feed-water heaters with geothermal preheaters to create a hybridized system. This study was based on a numerical model validated at a selected Polish power unit. The model was subsequently calibrated for off-design conditions to facilitate partial load analysis. The obtained characteristics outperformed those of the non-hybrid unit, generating over 18 MW of electric power output. Such an improvement could potentially boost the unit's net efficiency by more than 2.6 %. This enhancement is significant as power units typically operate under part load for approximately 90 % of the time, hence the need to evaluate the performance characteristics of hybridized units in those states. Furthermore, the research outlines the potential decrease in the plant's CO2 emission factor, with reductions reaching up to 6.5 % under off-design conditions. Based on a gap analysis of the existing literature, this paper's comprehensive partial load evaluation serves as a new addition to research on hybridized systems.

Thermal energy storage integration for increased flexibility of a power plant with post-combustion CO2 capture

Flexible operation of thermal power plants will become increasingly relevant in the coming years. This work evaluates the effect of integrating a steam accumulator into a 598 MW supercritical coal-fired power plant with moving bed temperature-swing adsorption CO2 capture. Charging the accumulator with reheat steam from the turbine train can reduce the net power output by up to 1.4 % (8.2 MW) for around 200 min. Small charging flow rates are recommended to maximize the final pressure of the accumulator. Covering the sorbent regeneration duty and meeting the demand of two feedwater heaters were considered as alternatives for discharging of the accumulator. Thermal storage discharging was found to give relative power plant load increases between 1.7 and 11.2 % (10.2–66.9 MW) for up to 37.5 min, which exceeds the requirement for primary reserve. Increases in the electrical energy output of 10.5–11 MWh were achieved. The flexibility modes studied in this work are compatible with high CO2 recovery rates.

Enhancement of thermal power plant performance through solar-assisted feed water heaters: An innovative repowering approach

Increasing the efficiency of a power plant by optimization or repowering has always been a crucial challenge for energy analysts. At the same time as natural energy resources are limited, the integration of renewable energy sources such as solar energy has been prioritized for the past few decades. This study presents a way of enhancing a thermal power plant with a regenerative reheating Rankine cycle, evaluating the impact of solar-powered heat exchangers on feed water heating at 200 MW single unit of the Shahid Montazeri Power Plant operating at 13 MPa and 540 °C. Increases in energy-exergy efficiencies, power output and fuel save due to this modification have been studied in 14 different cases which have been analyzed in Engineering Equation Solver (EES). The case studies cover replacing single, double, and triple Feed Water Heaters (FWH). Parametric analysis of the four most promising cases has been performed in varying operating conditions such as main steam and reheat steam temperature and pressure and condensation pressure. In the most favorable configuration (case 12), the net thermal power output increases to 225 MW while energy and exergy efficiency increases to 39.73 % and 43.99 % respectively. Exergy and energy loss across different major components have been presented as well which indicates room for further improvement and contributes valuable insights to thermal power plant optimization for sustainable and efficient energy solutions in the future.

Dynamic exergy analysis of feed water heater in nuclear power plant during start-up process

In order to study the thermal economy of the feed water heater (FWH) start-up process (SUP), a dynamic mechanism model has been established, and the dynamic exergy analysis was conducted using this model. The effects of step and continuous changes in extraction steam flow on the exergy characteristics of the SUP were investigated. For the step change study, the step amplitude of extraction steam flow increased from 12.5 % to 100 % and the effects on the exergy characteristics were analyzed. To study the effects of the continuous change in extraction steam flow, the exergy was characterized and analyzed with three types changes: the quick opening, the linear and the equal percentage. The dynamic characteristics of the exergy parameters during the SUP of the FWH were then clearly defined. The highest steady-state exergy efficiency (95.72 %) was achieved for the FWH when the step amplitude was at 50 %. The more optimal start-up method should have the equal percentage extraction steam flow change characteristics with the highest process average exergy efficiency (94.07 %) and the lowest accumulated exergy destruction (21.339 GJ). This study could provide important guiding significance for the SUP of the FWH.

Insulation of feed water tank in arrangement of transportable boiler plant with direct-flow steam boiler

A transportable boiler plant is used to provide consumers with steam of high energy characteristics, while saving costs for the construction of stationary boiler houses. A transportable boiler plant can be placed in the conditions of the Far North on an oilfield site. It is therefore necessary to organize reliable and safe operation of the boiler house, consisting of a steam direct-flow boiler of the coil type, a feed pump, a feed water tank and other auxiliary elements of the thermal circuit. One of the important elements in the thermal circuit is the feed water tank, in which water accumulates after chemical purification. It is where the water is also heated, increasing the efficiency of the boiler. Methods for calculating the diameters of main steam pipelines and feed water pipelines are described. The theoretical foundations of the operation of the feed water tank, its use in thermal power plants, combined heat and power plants, district industrial and heating boilers using various thermal arrangements of the above-mentioned enterprises are considered. The operation of the feed water tank in the thermal circuit of a steam unit is discussed. A thermal circuit of an industrial boiler house has been designed to generate saturated steam for consumers using direct-flow steam boilers of the coil type. The diameters of the inlet and outlet pipelines of the storage tank are calculated. The effective thickness of thermal insulation required to minimize heat losses during operation of a transportable boiler plant has been determined. Modeling of the design of the feed water tank and heat losses through its surface is carried out. A 3D model of the designed tank is presented, as well as heat losses through the surface of the tank walls when using a thermal insulation material. The importance of using thermal insulation of various tanks for storing feed water, petroleum products, hydrocarbons and other various media is noted.

Ways of TPP Power Units Modernization During Their Conversion to Ultra-Supercritical Steam Parameters

The approach to solving the applied problem of modernization of the 300 MW series power units produced by JSC "Ukrainian Energy Machines" by converting them from supercritical to ultra-supercritical steam parameters, provided that regenerative feed water heating system is preserved as much as possible, which will lead to an increase in the energy efficiency of the TPP with minimal conversion, is analyzed in the paper. The conversion of the K-300-240-2 power unit to the parameters of fresh steam 650 °C/30 MPa and intermediate superheated steam 650 °C/7 MPa, determined as optimal as a result of previous studies, can be carried out by completely replacing the high-pressure cylinder of the existing unit for a new high-pressure cylinder with ultra-supercritical steam parameters and superstructure with an additional intermediate-pressure cylinder while fully preserving the parameters and designs of the intermediate- and low-pressure output parts. Two options for modernization of the 300 MW series power unit thermal circuit structure were considered, and the scale of conversion of the regenerative feed water heating system was evaluated. In the first option of the thermal scheme, the 1st steam selection is organized from the cold threads of the modernized high-pressure cylinder with ultra-supercritical steam parameters, and the 2nd one – from the cold threads of the additional intermediate-pressure cylinder. In this case, two high-pressure heaters and a turbo drive of the feed pump are subject to replacement. The disadvantage of this option is that due to a significant increase in steam parameters, it is impossible to choose high-pressure heaters from the existing model range, and a new design must be developed. The electrical efficiency for this modernization option increases from 36.5% (the initial thermal circuit of the K-300-240-2 turbine) to 42.5%. In the second option, it is proposed to install an additional turbine with a capacity of 3 MW, to the input of which a steam from cold threads of the high-pressure cylinder with ultra-supercritical steam parameters is supplied with a loss equal to the sum of the 1st and 2nd selections of the original version of the turbine, on the same shaft with a turbo drive of the feed pump for the sake of preserving the existing high-pressure heater. The steam from the additional turbine selections goes to high-pressure heaters HPH9 and HPH8 with parameters corresponding to the output data of the existing turbine. Taking this into account, high-pressure heaters will not be replaceable. In addition, the power of the additional turbine is sufficient to ensure the operation of the feed pump together with the turbo drive of the feed pump to obtain a water pressure of 34 MPa. In view of this, the turbo drive of the feed pump also remains unchanged, except for the additional turbine installation. The electrical efficiency for the second option of the modernization scheme of the K-300-240-2 power unit is 42.4%. It was determined that the payback period of the modernization according to the first option is 5 years, taking into account the modernization of the boiler unit, and according to the second one – 4.5 years. It is proposed to choose the option of the thermal scheme with an additional turbine, since in this case it is possible to modernize the K-300-240-2 power unit with the maximum possible preservation of the regenerative feed water heating system while increasing its energy efficiency by almost 14%.

A dual-weight domain adversarial network for partial domain fault diagnosis of feedwater heater system

Domain adaptation (DA) approaches have received significant attention in industrial cross-domain fault diagnosis. However, the scarcity of sufficient labeled fault data, particularly under varying loading conditions and harsh operational environments, can give rise to distinct label spaces between two domains, thereby impeding the application of DA-based diagnosis methods. In this paper, we propose a novel dual-weight domain adversarial network (DWDAN) for diagnosing partial domain faults of feedwater heater system in a large-scale power unit, where the target label space is a subset of the source domain. Firstly, domain adversarial network with an instance-based feature learning strategy is constructed to capture domain-invariant and class-discriminative features hidden in raw process data, thereby enhancing feature extraction and generalization abilities of fault diagnosis. Furthermore, a dual-stage reweighted induction module is designed to quantify the contribution of samples from both class-level and sample-level for selective adaptation. This module can automatically eliminate outlier fault categories in the source domain and facilitates alignment of feature distributions for shared fault categories. Comprehensive experiments conducted on the feedwater heater system of a 600 MW coal-fired generating unit demonstrate the outstanding performance of DWDAN.

Optimal design of a concentrated solar power plant with a thermal energy storage system using the Downhill Simplex Method

In this work, a concentrated solar power (CSP) plant with a thermal energy storage system to produce 120 megawatts of electrical energy was designed using Thermoflex. As non-renewable resources are limited, to move towards sustainable development, the importance of developing alternative technologies such as optimized solar power generation systems becomes considerable. To eliminate the gap between electricity demand and power supply in solar power plants, it is necessary to use optimized thermal energy storage systems. So, in this study the Nelder-Mead algorithm as a novel optimization method was coupled with Thermoflex in the Excel environment to obtain an optimized techno-economic design. Finding the minimum of the Rosenbrock benchmark function confirmed that the simplex algorithm can find optimal solutions in a short time for complicated optimization problems. For plant optimization, twelve parameters that have the greatest effect on the objective function were selected as decision variables. The optimization results after 77 iterations demonstrated that in the optimal case, the objective function decreases from 4.48 to 4.38. This was equivalent to a 2.98 MWe power increase, while the cost of CSP components remained at an acceptable level. The total heat transfer for the solar boiler and feed water heater train sections before and after optimization is 391.816 MWth and 395.033 MWth, respectively.

Seasonal dynamic modeling and simulation of solar thermal membrane desalination system for sustainable freshwater production: a case study of Tanta, Egypt

AbstractMembrane distillation (MD) is an effective process for desalinating seawater, combining the merits of both thermal and membrane distillation. In this context, the sizing methodologies and optimization strategies are developed from the balance of the system’s energy demand. Therefore, accurate numerical modeling of the heat transfer and thermodynamic behavior of the MD systems is crucial for the optimal design of solar-based MD systems. The interest in utilizing solar thermal heating techniques for feed water heating in MD systems is increasing worldwide for sustainable freshwater production and lowering energy consumption. Hence, in this research, a coupled analytical modeling based on heat transfer, mass transport, and thermodynamic analysis is created to dynamically simulate a solar direct contact membrane distillation system (SDCMDS) driven by vacuumed tubes solar collectors (VTSCs) to analyze its performance, under real weather of Tanta, Egypt. The influences of the solar collecting area on the performances of the proposed SDCMDS for augmenting the freshwater production of the SDCMDS are studied. Four cases of the proposed SDCMDS are investigated: two identical VTSCs of 1.80 m2 each unit in summer (Case I), two identical VTSCs in winter (Case II), four identical VTSCs in summer (Case III), and four identical VTSCs in winter (Case IV). The results show that the utilization of four VTSCs connected in series significantly improved the feed seawater temperature range from 30.0 to 70.5 °C compared to a feed temperature range of 30.0–49.5 was achievable by utilizing only two VTSCs. Moreover, the daily averaged permeate flux were 2.21, 1.29, 3.41, and 2.07 L/day per m2 of solar harvesting area with daily cumulative distilled water yield of 7.48, 4.60, 23.04, and 14.78 L/day for Cases I, II, III, and IV, respectively, at a saline flowrate of 0.20 kg/s. The daily average total efficiency of the SDCMDS was obtained to be 14.70%, 12.50%, 24.95%, and 22.50% for Cases I, II, III, and IV, respectively.

Electrothermal interfacial evaporation through carbon-nanostructured composite membranes

High energy demand required in membrane distillation (MD) process to heat feed water and maintain the necessary temperature gradient across the membrane presents a challenge to widespread adoption of MD. In response to this challenge, surface heating membrane distillation (SHMD) has emerged as a promising solution. SHMD can employ solar or electrical energy to directly heat the membrane and feed, eliminating the need for an external heat source to heat feed water. In this study, we explore electrothermally-driven interfacial evaporation using a multi-walled carbon nanotube (MWCNT)-based composite membrane and further envision its utilization for high-efficient SHMD. Upon application of voltage, the resistance of the MWCNT leads to the conversion of electrical energy into heat, which is then uniformly transferred to feeds. The MWCNT-based composite membrane exhibited an evaporative water flux of up to 2.34 kg m−2h−1 with an associated energy efficiency of 61% and demonstrated outstanding localized surface heating performance. The employed membranes exhibited no significant variations in either resistance or surface temperature, regardless of the direction of the applied electric field. Energy parameters from the electrothermal membranes showed quantitative agreement with values reported for various electrothermal MD systems, suggesting the potential of the composite membranes in energy-efficient and cost-effective localized heating MD applications.

Enhancing conventional steam power plant performance through feed water heating repowering

ABSTRACT Repowering of old steam power plants is a viable solution to increase power and improve efficiency. This study investigates the feasibility of feed water heating repowering for the Neka steam power plant by considering the influences of steam mass flow rate on the condenser performance and the heat rate of the new cycle. Energy and exergy analyses were conducted using the first and second laws of thermodynamics and heat transfer relations in each scheme. The effect of increasing the steam mass flow rate on the performance of the condenser and the cycle was also investigated. The repowered cycle was simulated using Thermoflow software, and the results were validated with small errors. The results showed that replacing low and high-pressure heaters with new heat exchangers increased the power of the steam unit and the repowered cycle, energy, and exergy efficiencies by 15.7%, 49.3%, 5.93%, and 2.17%, respectively. Although the condenser pressure increased by 19 millibars, leading to a 0.63% increase in the heat rate, the total heat rate of the repowered cycle improved by 4.62%. Overall, the findings demonstrate that feed water heating repowering can be an effective strategy to increase the efficiency and power of conventional steam power plants.

Extraction turbines and feed-heating in geothermal binary plants: A thermodynamic performance assessment

The use of extraction turbines in conjunction with multiple feedwater heaters is standard practice in conventional fossil or nuclear steam electrical generating stations as a way to conserve fuel by raising the final feedwater temperature entering the boiler. One way to improve the thermal efficiency of geothermal binary plants is to include a heat recuperator that uses the expanded, but still hot working fluid leaving the turbine to preheat the working fluid leaving the feed pump prior to reaching the main brine heat exchangers. However, the use of partially-expanded working fluid from an extraction turbine to further preheat the working fluid has not been widely deployed in geothermal binary plants. This paper will describe this technique in a feed-heating cycle, develop the working equations to assess the performance for a variety of geofluid temperatures, to determine whether or not this approach can be as effective in geothermal binary plants as it is in conventional nuclear power plants. Finally, we will discuss the practical aspects of this system in geothermal binary plants, and suggest some further studies to extend this concept to other geothermal applications.

АЭС малой мощности с аккумулятором теплоты фазового перехода

Nuclear power plants (NPP) are characterized by low maneuverability. This fact exacerbates the problem of the balance of generated and consumed power when nuclear power plants are used as an energy source. This problem is especially relevant for isolated power systems. One of the ways to increase the maneuverability of nuclear power plants is to use heat accumulators directly in the NPP circuit. The study is carried out for two most attractive options of including a heat accumulator in the NPP circuit: 1) parallel to a high-pressure heater to heat feed water; 2) to generate additional steam for a low-pressure cylinder. The efficiency of each of the options is determined based on the calculation of thermal schemes of nuclear power plants with a heat accumulator. The authors have calculated the power of the turbine unit and electricity generation when a heat accumulator is included in the nuclear power plant circuit. The analysis of the data obtained shows that when using a heat accumulator in the NPP circuit in parallel with high pressure heater to heat feed water, the power of the turbine unit is increased by 7,2 % in the accumulator discharge mode, and additional electricity generation due to accumulated heat is 0,63 MJ for each kilogram of waste steam. When using a heat accumulator to generate additional steam for a low-pressure cylinder, the power of the turbine unit is increased by 6,6 % in the accumulator discharge mode, and the additional power generation due to the accumulated heat is 0,40 MJ per kilogram of waste steam. Application of heat accumulators in the NPP circuits will allow using the accumulated heat to generate additional electricity during high demand hours. Thus, the use of heat accumulators in NPP circuits is a way to increase the maneuverability of nuclear power plants, to reduce the negative impact of maneuverable modes on NPP equipment, and to reduce the number of liquid radioactive waste. The most effective and simple way to use the heat accumulator in the NPP circuit is to install it in parallel to the high-pressure heaters. In future, it is planned to determine the design of the heat accumulator, to model heat exchange processes in the heat accumulator