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Hot dry rock is a new type of geothermal resource which has a promising application prospect in China. This paper conducted a comparative research on performance evaluation of two eligible bottoming cycles for a hot dry rock power plant in the Gonghe Basin. Based on the given heat production conditions, a Kalina cycle and three organic Rankine cycles were tested respectively with different ammonia-water mixtures of seven ammonia mass fractions and nine eco-friendly working fluids. The results show that the optimal ammonia mass fraction is 82% for the proposed bottoming Kalina cycle in view of maximum net power output. Thermodynamic analysis suggests that wet fluids should be supercritical while dry fluids should be saturated at the inlet of turbine, respectively. The maximum net power output of the organic Rankine cycle with dry fluids expanding from saturated state is higher than that of the other organic Rankine cycle combinations, and is far higher than the maximum net power output in all tested Kalina cycle cases. Under the given heat production conditions of hot dry rock resource in the Gonghe Basin, the saturated organic Rankine cycle with the dry fluid butane as working fluid generates the largest amount of net power.

The integration and accommodation of the wind and solar energy pose great challenges on todays power system operation due to the intermittent nature and volatility of the wind and solar resources. High efficient large-scale electrical energy storage is one of the most effective and economical solutions to those problems. After the comprehensive review of the existing storage technologies, this paper proposes an overall design scheme for the Non-supplementary Fired Compressed Air Energy Storage (NFCAES) system, including system design, modeling and efficiency assessment, as well as protection and control. Especially, the design principles of the multistage regenerative, i.e. heat recovery system which is used to fully recycle and utilize the waste heat from compression are provided, so as the overall system efficiency evaluation method. This paper theoretically ascertains the storage decoupling rules in the potential and internal energy of molecular compressed air and reveals the conversion mechanism of gas, heat, power, electricity and other forms of energy. On this basis, a 500-kW physical simulation system of CAES system (TICC-500, Tsinghua-IPCCAS-CEPRI-CAES) is built, which passed a system-wide 420-kW load power generation test with less pollution and zero carbon emissions. Besides, the multi-form energy conversion of multi-stage regenerative CAES and storage efficiency is verified, especially its incomparable superiority in solving the uncertainty problem in wind and solar power generation. Finally, the propaganda and application scenario of the CAES system in China is introduced.

The present study proposes a novel refrigerator in theory, which uses 4He as working fluid to directly reach 2.3 K and uses a small amount of 3He to attain the temperature below 1.7 K. The compact and highly efficient new refrigerator works with the Vuilleumier cycle. The novel refrigerator is driven by a thermal compressor which creatively uses mix-refrigerants J-T refrigerator alternative to liquid nitrogen as the power source. Furthermore, the Vuilleumier cycle can be used to achieve temperature below liquid helium with the improvement of the ultra-low temperature regenerator material. A new method of reaching the temperature below 1.7 K is proposed on the regenerative refrigerator, which could be an important breakthrough for the cryogenic science and technology.