Cold Storage and Release Characteristics of a Thermal Battery Unit Using Solid Nitrogen and Solid Nitrogen Impregnated in Metal Foam
Large cold storage capacity is very important to maintain the stable working condition of a superconducting magnet. Solid nitrogen is frequently used for cold storage at cryogenic temperatures. In this paper, we report the experimental investigation of the cold storage and cold release characteristics of a thermal battery unit using solid nitrogen, as well as the combination of solid nitrogen and copper foam under different conditions. In order to enhance the heat transfer without significantly compromising the cold storage capacity, the copper foam is adopted to enhance the effective thermal conductivity of solid nitrogen. It is found that the copper foam can effectively enhance the cold release process, making the cold energy stored effectively utilized.
Research on Cold Storage Multi-objective Optimal Operation with Photovoltaic Power Generation
As the total amount of cold storage increasing year by year, the disorderly access of heavy power load will make the power grid peak and valley difference increase. At the same time, the high operating cost will also increase the burden of users, so the optimal operation of the cold storage is crucial. Based on the TOU price policy, the optimal operation model of cold storage is established with the objective function of minimizing the operating cost and the load power variance. The optimal operation strategy of cold storage is solved by membership function and particle swarm algorithm, and the load and start of cold storage are calculated according to the 0-1 knapsack algorithm. The influence of different price on the operation strategy is analyzed. Making a garlic market in Henan as example analysis, shows the results that considering the PV and TOU case, optimal control strategy to reduce operating costs and power grid peak valley difference has obvious advantages, in which the cost saving rate in cold season and boom season are 199.4% and 92.6% respectively. 1
Double-Evaporator Thermosiphon for Cooling 100 kWh Class Superconductor Flywheel Energy Storage System Bearings
This paper presents an idea for a thermosiphon that uniquely implements two integrated evaporators to cool two HTS (High Temperature Superconductor) bulk sets in different locations, simultaneously. A so-called double-evaporator thermosiphon was designed, fabricated and tested using nitrogen as the working fluid under sub-atmospheric pressure conditions. The operating target temperature was approximately 65 K. To confirm the feasibility of the double-evaporator thermosiphon, experiments during the cool down process and steady state operation were extensively conducted on the double-evaporator thermosiphon (Ltot = 1075 mm, do = 160 mm). The double-evaporator thermosiphon worked successfully at steady state operation. The results showed that it had a maximum total temperature difference between the condenser and the evaporator of 1.3 K and a temperature difference between the two evaporators of 0.6 K at a heat flow of 87 W. This thermosiphon was designed for actual application to a 100 kWh SFES (Superconducting Flywheel Energy Storage) system. The potential impact of superior heat transfer characteristics of the double-evaporator thermosiphon is discussed in the paper.