Comprehensive methodology for identifying tariff zones of efficiency of hydrogen-thermal

ABSTR A C T In countries with developed nuclear energy, there are problems associated with non-uniformity of the daily electricity load, due to the economically justified need to load nu-clear power plants with a maximum installed capacity utilization factor. This is due to the cheapness of nuclear fuel compared to organic and, at the same time, high investment compared to thermal power plants, as well as the presence of technological limitations on maneuverability. Most organic fuel thermal power plants are switched to half-peak mode, which negatively affects their efficiency and reliability. In addition, the ever-increasing requires on the level of safety negatively affect the economic competitiveness of nuclear power plants. Improving safety through the intro-duction of passive heat removal systems of the reactor core is provided for in new NPP projects. These systems have several disadvantages: maintenance costs; a significant in-crease in capital investment; emergency cooling mode. To solve these problems, the authors developed a system of hydrogen-thermal accu-mulation, which, when combined with a nuclear power plant, allows one to accumulate cheap energy during the hours of a decrease in load in the power system due to electrolysis of water to produce hydrogen and oxygen, and thermal accumulation of hot water in heat-insulating tanks. Thanks to the use of hot water tanks, investment in the accumulation system is significantly reduced. Thanks to the use of a hydrogen-oxygen steam generator, the opportunity to generate an additional main steam and to use it in the additional steam turbine unit appears, which will allow to avoid costly modernization of the main equip-ment of the nuclear power plant and reducing its lifetime. The presence of a low-power steam turbine unit as part of the accumulation system ensures uninterrupted autono-mous power supply to consumers of the NPP own needs due to the possibility of using the energy of the reactor residual heat, when the station is completely blackout. The method of combining the hydrogen complex with thermal accumulators is completely new and has no analogues. The economic efficiency of the developed energy complex has been investigated. The accumulated net present value was determined depending on the off-peak electricity tariff for the three options of the half-peak electricity tariff, taking into account possibility to refuse expensive heat exchangers of the passive heat removal systems. It is shown that the use of the proposed scheme is advisable in regions with off-peak electricity tariffs in the range 0-0.32 cents/kW center dot h, 0-0.8 cents/kW center dot h and 0-1.25 cents/kW center dot h, respectively, depending on the forecast dynamics of the half-peak electricity tariff. The average payback period of the accumulation system for given conditions is equal to 3-15 years. (c) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

In countries with developed nuclear energy, the issue of non-uniformity in daily electricity load and the balance between safety and economic competitiveness are prominent. By utilizing a hydrogen-thermal accumulation system, these problems can be effectively addressed.