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The response potential of demand-side resources is becoming increasingly significant in integrated energy system (IES) operations. In addition, to ensure the effective participation of system devices, their actual responsiveness at different timescales should be considered. Based on these considerations, this paper proposes an IES multi-timescale operation optimization strategy that incorporates multiple forms of integrated demand response (IDR) and considers the response characteristics of the equipment. First, the multi-timescale characteristics of IDR are analyzed. Moreover, a multi-timescale operation model of IES that comprises day-ahead, intraday, and real-time stages is further established. In the day-ahead dispatch, a low-carbon economic scheduling model is developed by considering the shifting demand response (DR) and the cost of carbon emissions. In the intraday scheduling, noting that cooling and heat energy transmission possess slow dynamic characteristics, a rolling optimization model for cooling/heating coupled equipment considering load shedding and substituting DR is established. In real-time scheduling, the output of electric/gas coupled equipment is adjusted. Finally, an industrial park-type IES in northern China was selected as an example for a case study. The results show that (1) the IDR multi-timescale response strategy can exploit different types of demand-side flexibility resources. After implementing the shifting DR, the peak-to-valley difference of the electric load curve was reduced by 20%, and the total system cost was reduced by 2.3%. After implementing load shedding, the maximum load differences per unit period of the electric, heat, and cooling load curves decreased by 18.7%, 40.0%, and 68.9%, respectively. (2) By refining the timescale of IES optimization, the proposed model can effectively ensure the energy supply and demand balance of the system under different load scenarios and reduce the system operation cost. After applying the model to simulation in three typical days (transition season, summer, and winter), the penalty costs of lost loads reduce by ¥3650, ¥3807, and ¥3599, respectively, and the total system costs decrease by 17.4%, 16.1%, and 16.2%, respectively. [ABSTRACT FROM AUTHOR]

The objective of this paper is to analyze the performance of the rooftop photovoltaic (PV) system, taking into account its shading impact on the rooftop surface and the eventual cooling load of the building. This paper tests three approaches of the rooftop PV system: zero tilt angle flat PV configuration; PV configuration with a monthly adjusted tilt angle; and PV configuration with a dual-axis sun tracking system. Each of the PV configurations is optimized to do the following: minimize the self-shading among the adjacent arrays; maximize the rooftop surface shading to curtail the cooling load; maximize the net energy yield; and minimize the net levelized cost of energy (LCOE) of the PV system. The existing building model is developed in SketchUp Pro. The model is simulated in an EnergyPlus environment to calculate the building's cooling energy consumption with different shading scenarios in various PV configurations. Various rooftop PV configurations are designed and simulated in a System Advisor Model (SAM) to analyze the effect of self-shading of the adjacent PV arrays on the PV performance. The optimal distance between the arrays (for maximum net energy yield and minimum net LCOE) is found to be 1.5 m. The net LCOE of the optimal scenario is 5.247 ¢/kW h and 4.112 ¢/kW h for monthly tilt and dual-axis tracking arrangements, respectively. The economic surplus of the optimized system is 0.422 ¢/kW h and 0.258 ¢/kW h for the monthly tilt and dual-axis tracking arrangements, respectively, as compared to the ground-mounted system. [ABSTRACT FROM AUTHOR]

Due to the higher energy efficiency as well as the higher flexibility and reliability of energy supply, multi-carrier energy systems (MCESs) have attracted extensive attention. However, the power imbalance caused by uncertainty, the complicated couplings among multiple carriers, and the communication obstacles among multiple MCESs bring challenges to the synergistic scheduling of multiple MCESs. To this end, this paper studies the synergistic scheduling of multi-MCES coupled with electricity, natural gas, heating, and cooling carriers, considering integrated demand response (IDR) program and load volatility. First, an IDR program with electricity, heating, and cooling loads is proposed, where the consumers can change their energy consumption patterns in response to price signals to reduce operating costs. Second, to smooth the electricity load curve and avoid load fluctuations, load volatility is taken into account when implementing the IDR program. In addition, the non-convex constraints of natural gas network are tackled via second-order cone relaxation, and the scheduling of multi-MCES is reformulated as mixed integer second-order cone programming (MISOCP). Finally, the synergistic scheduling model of multi-MCES considering IDR program and load volatility is solved by consensus-based alternating direction method of multipliers with limited boundary information exchange with neighboring MCESs. Numerical results illustrate the effectiveness of the proposed distributed IDR program in a multi-MCES. [ABSTRACT FROM AUTHOR]

To meet the cooling demands of high heat flow density hotspots in scenarios such as electronic chips, a novel three-dimensional stacked T-shaped thermoelectric cooler (STTEC) is designed in this study. Under steady-state conditions, a finite element method with coupled thermal–electrical–mechanical physical fields is utilized, and the temperature dependence of thermoelectric (TE) materials is considered. First, the cooling flux, coefficient of performance (COP), and minimum cooling temperature of STTEC under different input-current and thermal boundary conditions are investigated and compared to the traditional π-shaped thermoelectric cooler (π-TEC). Second, the effects of geometrical parameter variations under optimal currents on the cooling performance and reliability of STTEC are studied. Finally, the structural parameters are optimized. The results show that the STTEC altered the path of TE conversion and transfer, which significantly improved the optimal current. The STTEC has a remarkable advantage in cooling performance under low temperature differences or high cooling loads. Compared to the π-TEC, STTEC enhances cooling flux by 101.6%, rises COP by 358.5%, and lowers the cold-end temperature by 46.6 K. At optimal current conditions, by optimizing the thickness of the T-shaped copper slice and the height difference between the TE leg and the T-shaped copper slice, the thermal stress decreased by 18.4%. The STTEC’s novel design could inspire the manufacturing and commercialization of high-performance thermoelectric coolers. [ABSTRACT FROM AUTHOR]

The atomic structure of Al90Sm10 metallic glass is studied using molecular dynamics simulations. By performing a long sub-Tg annealing, we developed a glass model closer to the experiments than the models prepared by continuous cooling. Using the cluster alignment method, we found that "3661" cluster is the dominating short-range order in the glass samples. The connection and arrangement of "3661" clusters, which define the medium-range order in the system, are enhanced significantly in the sub-Tg annealed sample as compared with the fast cooled glass samples. Unlike some strong binary glass formers such as Cu64.5Zr35.5, the clusters representing the short-range order do not form an interconnected interpenetrating network in Al90Sm10, which has only marginal glass formability. [ABSTRACT FROM AUTHOR]

A model of a vacuum thermionic refrigerator with external heat transfer is proposed. The general expressions for cooling load and coefficient of performance (COP) are derived using the combination of finite time thermodynamics and nonequilibrium thermodynamics. The optimum regions of cooling load and COP are obtained and the effect of the heat reservoir temperature on the optimal performance of the device is analyzed by detailed numerical examples. The effects of work function on the cooling load and COP performances of the thermionic device are also investigated. By comparing the results obtained herein with those using the traditional analysis without considering external heat transfer, it is shown that the present analysis is more practical for real vacuum thermionic devices. The results may provide guidelines for the design and application of practical thermionic refrigerators [ABSTRACT FROM AUTHOR]

The high cost of cooling the cryoshroud in a molecular beam epitaxy system has been greatly reduced by replacing liquid nitrogen (LN2) as a coolant with a silicone polymer heat transfer fluid cooled to as low as -80 °C by a closed cycle chiller. Gallium arsenide epitaxial layers have been grown with two different cooling configurations of the shroud: conventional LN2 cooling and cooling to -70 °C with the chiller. The partial pressure of water in the chamber is a factor of about 2.5 higher with the closed cycle chiller operating at -70 °C than with liquid nitrogen in the shroud. No significant difference is observed in the density of deep levels in the GaAs, as determined by deep level transient spectroscopy. [ABSTRACT FROM AUTHOR]