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An optimal design of a regional integrated energy system (RIES) configuration is necessary to realize the efficient use of various energy resources as well to improve the energy efficiency and economic benefits of the integrated energy system (IES). Practical integrated energy projects often have problems with unreasonable capacity configuration which results in poor system economics and inoperability. In the current research on the capacity allocation of RIESs, the type of energy system is singular and the coupling relationship between various parts of the system is rarely considered. This results in a lack of theoretical guidance and calculation tools for the optimal designing of future RIESs. This study researches the optimization of the capacity allocation of IES based on typical residential area modules and typical commercial modules built on actual regional plots. TRNSYS is selected to simulate energy consumption, and Genopt has been selected to build the optimization system platform, couple the regional load demand, configure multi-energy system, and optimize the real-time results of the calculation. With aim to achieve the lowest life cycle cost of the IES, this research analyzes the optimized configuration of IESs including the composite cold and heat source system. This study establishes a fast and efficient IES optimal capacity ratio calculation model, which is 7.55% different from the actual energy consumption of the project. This study also provides theoretical methods and calculation tools for the ongoing research on the optimal design of RIESs, including composite cold and heat source systems and effectively improving system economics. [ABSTRACT FROM AUTHOR]

The paper describes a U-type deep borehole heat exchanger (DBHE) containing both two vertical boreholes and one horizontal boreholes for the application of medium-deep geothermal energy, the circulating fluid flows through every borehole in turn and therefore more underground heat can be absorbed. The boreholes are called as descending, horizontal and ascending boreholes, and the heat transfer tubes in the corresponding boreholes are called as descending, horizontal and ascending tubes, respectively. The backfill grout is set between borehole wall and the corresponding tube. The characteristics and the working principles of the U-type DBHE are discussed. The governing equations of heat transfer are established, and the numerical finite difference methods are employed to build the node equations for both the fluids in the heat transfer tubes and the underground medium, and the pursuit method is taken into consideration to obtain the temperatures used in the node equations. In addition, An actual project that uses U-type DBHE to heat the buildings was investigated. The research work can promote the further development and application of medium-deep geothermal heating technology. [Display omitted] • Describe the structural composition and working principle of borehole heat exchanger. • Explain the governing equations and the corresponding conditions. • Establish the node equations for fluid of tubes. • Establish the node equations for underground rock soil. • Investigate the change of important parameters of one actual project. This paper describes a U-type deep borehole heat exchanger (DBHE) containing both two vertical boreholes and one horizontal boreholes for the application of medium-deep geothermal energy, and presents the heat exchanger's characteristics and the working principles. Compared with the single DBHE, the ability of the U-type DBHE to extract underground energy is better, and therefore a higher heating load of buildings can be assumed. First, the preconditions are explained, and the governing equations of heat transfer are established. Second, the numerical finite difference methods are employed to build the node equations for both the fluids in the heat transfer tubes and the underground medium. In addition, the pursuit method is taken into consideration to obtain the temperatures used in the node equations. Accordingly, the temperatures of the different locations in both the tubes and the underground medium can be acquired. Finally, one actual project is studied based on the models and the corresponding equations; the nominal heat absorption is analyzed, and the factors that exert an influence on it are discussed; the inlet and outlet temperatures of the circulating fluid in vertical and horizontal boreholes are investigated, and then, the temperatures of the underground medium at typical locations near the DBHEs are explored. The research results for the U-type DBHEs are beneficial to the improvement of heat transfer models of medium-deep geothermal energy, and they promote the development of heating technology used in geothermal energy applications. [ABSTRACT FROM AUTHOR]