Primary frequency regulation in the power system by nuclear power plants based on hydrogen-thermal storage

Abstract

According to the Technical Requirements for Generating Equipment of Participants in the Wholesale Market of the Unified Energy System (UES) of Russia, from 2016 to participate in the general primary frequency regulation (PFR), the maneuverable characteristics of generating equipment of nuclear power plants with VVER reactors put into operation before 2009 should ensure frequency deviations guaranteed realization of the required primary power for loading up to 2% of the nominal electric power. For this, the current capacity of the reactor installation should be maintained at a level of not more than 98% of the nominal thermal power. The fulfillment of this requirement significantly reduces the installed capacity utilization factor (ICUF) of reactor plant.In addition, at present in the UES of the Russian Federation there is a tendency towards an increase in the deficit of peak and half-peak capacities. The majority of fossil fuel-fired thermal stations are switched to the half-peak mode, which negatively affects their efficiency and reliability. In addition, the rise in price of natural gas makes it more profitable to sell it abroad instead of burning at power plants. On the other hand, an increase in the share of nuclear power plants is observed in the UES, which exacerbates the problems associated with the passage of minima and maxima of the daily load in the power system, due to the economically and technically justified need to load NPPs with maximum CUF.The authors developed an approach to solving this problem by combining NPPs with an environmentally friendly energy source – an autonomous hydrogen power complex (AHPC), which includes heat accumulators and an additional multifunctional steam turbine unit. The developed energy complex will allow energy to be accumulated during hours of minima load in the power system due to the electrolysis of water to produce hydrogen and oxygen, as well as the accumulation of hot water in the storage tanks. The accumulated energy can be used to generate super-nominal electricity to cover the half-peak load zone in the power system. In addition, the presence of a low-power steam turbine installation will ensure uninterrupted power supply to consumers of their own needs at the NPP by using the energy of the residual heat from the reactor when the station is completely de-energized.Based on the proposed power complex, a method has been developed to ensure the participation of NPPs in the PFR in an energy system with a constant CUF. To assess the effectiveness of the proposed solution, a methodology for thermodynamic analysis of the power complex based on the combination of NPPs with AHPC was developed. The dependence of the required hydrogen fuel consumption and the efficiency of using off-peak electricity on the temperature of the feed water supplied to the hydrogen-oxygen steam generator from the hot water tanks is constructed.Based on the results obtained, the technical and economic efficiency of the developed power complex is considered. The accumulated net present value was determined depending on off-peak electricity tariffs with three variants of the forecast dynamics of the half-peak electricity tariff, taking into account natural gas savings, reduced investment in NPP safety systems and the economic effect of ensuring the participation of NPPs in the PFR with the plant load at 100%.