Evaluation of NPP Efficiency Using Phase-Transition Batteries

In the context of the growing share of nuclear power plants in the energy systems of the European part of Russia and the shortage of flexible generating capacities, it becomes necessary to involve nuclear power plants in covering the variable part of the load schedule. With relatively low prices for nuclear fuel (at present, the equivalent cost of a uranium fuel load is five to six times lower than the cost of natural gas inside the country) and high specific capital investments in nuclear power plants, it is not economically efficient to unload them. Therefore, the combination of nuclear power plants with latent heat thermal energy storage (LHTES) and an additional steam turbine makes it possible to accumulate thermal energy generated at night and use it during peak hours to generate electricity with the maximum use of nuclear fuel, i.e., without changing the power of the nuclear reactor. In addition, the presence of an additional turbogenerator in emergency situations with a complete blackout of the NPP makes it possible to ensure the operation of the cooling systems by using the residual heat of the reactor to drive the turbine and, thereby, increase the safety level of the NPP. The analysis of prices for electricity in the wholesale electricity and capacity market of the Unified Energy System of Russia (WECM UES) and in the energy system of France (with the highest share of nuclear power plants) was carried out. The impact of the operation of the NPP power unit with a thermal energy storage system was assessed in addition to the alternative option: the construction of a pumped storage power plant (PSPP) at the WECM. Calculations of technical and economic indicators of the use of LHTES-based thermal energy accumulators at NPPs are carried out depending on the level of thermal power of the latter as well as the increase in the regulation range for electricity supply. It is shown that if we do not take into account the multifunctional properties of the energy complex based on LHTES and an additional turbine (increased safety, NPP participation in primary frequency control) with the existing difference in prices for electricity generated during peak and night periods on the day-ahead market, the payback of the NPP energy complex for LHTES-based is not provided. The return on investment in phase-change batteries and an additional turbine in the considered example can be achieved provided that the difference between the average prices for electricity generated during peak and night hours over a billing period of 25 years is 3400 rubles/(MW h) and the charging time/LHTES discharge exceeds 7 h per day.