Patent ID: 11940226
Assignee: STIESDAL STORAGE A/S
Field: Thermal processes and apparatus (Mechanical engineering)
Classification: CPC F | IPC F

Claim 0:
1. A method of operating a thermal energy storage, TES, system having a thermodynamic gas flow circuit including:
a gaseous working fluid that is not in liquid phase but maintained in gas phase throughout the gas flow circuit;
a first TES container, wherein the first TES container has a top and a bottom and contains a first TES medium for storing thermal energy, the first TES medium having an upper end and a lower end,
a second TES container, wherein the second TES container has a top and a bottom and contains a second TES medium for storing thermal energy, the second TES medium having an upper end and a lower end,
an energy converter for converting between electrical energy and thermal energy of the gaseous working fluid in the gas flow circuit; the energy converter comprising an electrical motor, an electrical generator, and a compressor/expander system, the compressor/expander system comprising a compressor and an expander, wherein the compressor is functionally connected to the motor for being driven by the motor during a charging period, and the expander is functionally connected to the generator for driving the generator during a discharging period;, the method comprising, during a charging period:
interconnecting the top of the first TES container and the top of the second TES container through the compressor and the bottom of the first TES container and the bottom of the second TES container through the expander,
driving the compressor by the electric motor, receiving the gaseous working fluid from the top of the second TES container by the compressor, and adiabatically compressing the gaseous working fluid by the compressor for increasing a temperature of the gaseous working fluid,
providing the compressed gaseous working fluid into the top of the first TES container and through the first TES medium for transferring heat from the gaseous working fluid to the first TES medium during movement of the gaseous working fluid from the top of the first TES container to the bottom of the first TES container,
receiving the gaseous working fluid from the bottom of the first TES container by the expander and adiabatically expanding the gaseous working fluid for decreasing the temperature of the gaseous working fluid,
after the expansion, receiving the gaseous working fluid by the bottom of the second TES container, and by flow through the second TES medium towards the top of the second TES container transferring thermal energy from the second TES medium to the gaseous working fluid;, the method comprising, during a discharging period:
interconnecting the top of the first TES container and the second TES container through the expander and the bottom of the first TES container and the second TES container through the compressor,
receiving the gaseous working fluid from the top of the first TES container by the expander and driving the generator for producing electrical power by work from the expander due to adiabatic expansion of the gaseous working fluid through the expander,
guiding the gaseous working fluid from the expander into the top of the second TES container and through the second TES medium for transferring thermal energy from the gaseous working fluid to the second TES medium during movement from the top of the second TES container to the bottom of the second TES container,
receiving and adiabatically compressing the gaseous working fluid by the compressor,
after the compression, receiving the compressed gaseous working fluid at the bottom of the first TES container for transfer of thermal energy from the first thermal medium to the gaseous working fluid during its flow towards the top of the first TES container;, wherein the system comprises a latent TES system including:
a latent fluid flow path containing a latent working fluid that comprises a phase change material,
a heat exchanger located in the gas flow circuit between the compressor/expander system and the bottom of the second TES container, the heat exchanger separating the latent working fluid from the gaseous working fluid by a thermally conducting wall for exchange of thermal energy between the gaseous working fluid in the gas flow circuit and the latent working fluid in the latent flow path;
a pump for pumping the phase change material through the heat exchanger and creating turbulence in the phase change material during the transfer of the thermal energy in the heat exchanger;, wherein the method further comprises:
during the charging period, after adiabatic expansion of the gaseous working fluid by the expander, guiding the gaseous working fluid through the heat exchanger and transferring thermal energy from the latent working fluid to the gaseous working fluid for increasing the temperature of the gaseous working fluid before receiving the gaseous working fluid by the bottom of the second TES container,, wherein the phase change material is in the form of ice slurry during operation of the system and the method comprises:
during the discharging period, guiding the gaseous working fluid from the bottom of the second TES container through the heat exchanger and transferring thermal energy from the gaseous working fluid to the latent working fluid prior to the adiabatic compression by the compressor.