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In this paper, the analysis model of thermal performance and available energy of two-stage cascade cycle heat pump water heater (HPWH) was established. For the first time, the equivalent transformation thermodynamic analysis method and available energy consumption equation were employed to carry out the theoretical analyses of thermal performance and available energy consumption for two-stage cascade cycle HPWH. And the correctness of the analysis approach proposed in this paper was verified by an example. The calculation results showed a significant agreement with the results derived by the first law of thermodynamics and energy conservation law. The available energy analysis of two-stage cascade cycle HPWH clearly revealed the available energy consumption rates for different working processes, including heat transfers of heat exchangers, flow of heat-carrying fluid, working medium cycle, output of hot water, etc. This approach could be conveniently used in the analyses of thermal performance and available energy consumption for actual complex thermal system with irreversible process. This paper provided the theoretical basis for the actual optimization design and operation analysis of cascade type heat pump systems, and furthermore, the results of the calculation instance would also have a certain reference value. [ABSTRACT FROM AUTHOR]

The objective of the parameter optimization of thermal system is to increase the system efficiency and decrease the cost of unit output power under the condition which the total output power can meet the actual requirements in energy applications. In this paper, a new parameter optimization method for actual thermal system was proposed, which was called the Equivalent Transformation Constant State Finite-time Thermodynamic Analysis Method and had two calculation steps. The first step was choosing the optimum efficiency under the principle of taking into account both output power and efficiency weights, and the second step was calculating the optimum total heat transfer coefficient ratio and other concerned parameters with the optimum efficiency fixed. The related calculation principles and formulas for parameter optimizations of this method were given. That provided the guiding theoretical basis for actual thermal system efficiency increase and cost decrease of unit output power. [ABSTRACT FROM AUTHOR]

A new parameter named monochromic effective temperature Tλ is proposed, which represents the thermodynamic quality of monochromic blackbody radiation. The exergy of the monochromic blackbody radiation is expressed by Tλ. The monochromic effective temperature equation is developed, which shows that the product of Tλ and the wavelength is constant, which equals 5.33016×10-3 m·K. The exergy function of monochromic blackbody radiation is presented. The cause of the view that there is negative entropy production in photosynthesis can be explained by the results of this work. [ABSTRACT FROM AUTHOR]

Abstract A novel multi-segment mirror hybrid solar concentration photovoltaic/thermal (CPV/T) system using the spectral beam splitting technology is proposed, and its composition, working principle and structural design method are introduced in this paper. The Needle optimization method is employed to design the spectral beam splitter for the CPV/T system. The Monte Carlo Ray Tracing method is used to simulate the solar concentrating process and the results reveal that the CPV/T system can provide high uniformity of solar radiation flux density distribution on solar cells. The relationships of key structural and optical parameters of the CPV/T system are investigated. The results indicate that increasing the solar cell installation height and reducing the solar cell width can both improve the geometric concentration ratio of the CPV/T system. The sun tracking error effect analysis is carried out. The analysis results indicate that the CPV/T system has an overall optical efficiency higher than 76.3% when the sun tracking error is less than 1°. Furthermore, the thermodynamic analysis of the proposed CPV/T system is conducted and the results show that the PV conversion efficiency and overall energy efficiency of the CPV/T system are both higher than those of the CPV system under the same condition. Highlights • A novel hybrid solar CPV/T system with spectral beam splitter is proposed. • The proposed CPV/T system has a high solar concentrating uniformity for PV utilization. • The proposed CPV/T system has a higher overall energy efficiency than that of the CPV system. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel CPV/T hybrid system employing beam splitter and sloped linear Fresnel reflector concentrator was proposed. [•] Structural parameters of the system components were calculated and optimized. [•] Concentrated radiation distribution on the PV device surface shows a good uniformity. [•] The system performance was analyzed on the basis of the experimental data of components and showed a high efficiency. [Copyright &y& Elsevier]