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This work investigated comprehensively the impacts of non-ideal optical factors, including incident angle, sunshape and optical errors on the performance of the parabolic trough collector (PTC). Each optical factor was defined based on their geometrical principles. It was revealed that the heat flux distribution distorted by optical factors was the main cause of changing performance of the PTC. The temperature distribution was completely dependent on the heat flux distribution. The incident angle caused cosine loss and end loss, which respectively reduced the effective incident solar radiation and produced a near-zero heat flux section at one end of the absorber. Based on the effective incident solar radiation, the collector efficiency was reduced by 41.11% with the incident angle increasing from 0° to 60°. Larger circumsolar ratios produced more uniform circumferential temperature distribution, while reduced greatly the collector efficiency. The specularity error and tracking error affected slightly the receiver's safety, while the slope error reduced obviously the threat to the receiver. When specularity error was small enough (

A new algorithm for obtaining the critical tube diameter and intercept factor of parabolic trough solar collectors (PTCs) under the condition of tube alignment error has been developed theoretically, which, compared with the Monte Carlo Ray Tracing (MCRT) method, reduces the computing time remarkably. The results produced by the proposed method comply very well with the results obtained by MCRT. The critical tube diameters for different alignment errors can be precisely calculated using the algorithm, which can also be used to explain well the variation of optical efficiency. Effects of structural parameters on the optical performance are also discussed comprehensively. It is revealed that the offset direction that is perpendicular to the focus-edge connection line is most likely to cause rays-escaping. There exists an aperture width range (and also focal length range) in which the optical efficiency decreases with increasing offset angle, which is contrary to the conclusion presented in previous literature that the effects of X-direction offset (a = 0°) is greater than that in Y-direction (a = 90°). The proposed algorithm establishes the foundation for further geometric study on the coupling effects of multi-errors on PTCs’ performance, and can also be used for quick calculation and analysis in practice.

The exploration of the thermal energy storage potential of building thermal mass is an important and economic means to increase the flexibility of energy use in buildings. Feasible ways to increase the flexibility characteristic, however, are still rare. In this study, the energy consumption and thermal performance of a building with a novel ventilated electric heating floor were investigated through a simplified thermal network model, which was validated by on-site measurement. Aimed at analyzing the performance of the building in different energy systems, multi-energy sources were assumed to supply power to the heating system, including a common power grid and an independent residential wind turbine. The impact of five parameters was simulated, including the floor thickness, the diameter and the distance of air ducts, the ventilation mode and the ventilation rate. To reduce the number of simulated cases, the orthogonal testing method was adopted. Based on the goal of reducing energy consumption from the power grid, increasing consuming wind power and improving thermal comfort, the best structural parameters of the floor were obtained. In traditional systems, it is found out that the ventilated floor with these structural parameters can maximally reduce the heating energy consumption by 46.3% when the fan is on throughout the period. In the hybrid energy system, the consumption of energy in the power grid is also reduced, but the wind power consumption is not increased with the ventilation rate under the set operational rules. The thermal comfort, however, is significantly improved by ventilation.

The adhesion and accretion of ice on ground aircraft always pose potential problem to aircraft engine operation and safety performance. Currently, chemical deicing technology is often used for aircraft deicing. However, it is effective, but not environmental-friendly, cost-effectively and always compromises material performance of aircraft. Infrared ray (IR) deicing technology, by contrast, is proved to be a promising deicing technology due to its high efficiency, safety performance and environment protection. However, the energy efficiency of IR deicing technology and physical process of ice melt have not been fully researched and understood. It is therefore necessary to study them to improve the IR deicing performances. In this paper, some important characteristics of IR deicing were firstly investigated, including ice melt rate, variation of ice temperatures and mass. Secondly, the heat transfer mechanism through whole deicing process was studied. Finally, based on the experiment results, the energy efficiency of IR deicing was calculated and discussed. And the studied results showed that the maximum energy efficiency of IR deicing could reach 53.1% at the highest setting temperature 2273 K. For melting 6.5 kg ice, the melt time was 1746 s and 1002 s at setting temperature 1073 K and 2073 K, respectively.

A novel dry-expansion shell-and-tube evaporator (DESTE) integrated with function of defouling was developed as a component of wastewater source heat pump (WWSHP). To compare the performance of the DESTE-WWSHP with the conventional immersed evaporator (IE) based wastewater source heat pump (IE-WWSHP), an experimental platform was built by installing a DESTE and an IE unit in parallel in a same WWSHP system. The performance tests were conducted with the wastewater collected from downstream of a commercial sauna center in Shenzhen, China. Several operating parameters were investigated, including water heating capacity, coefficient of performance (COP), hot water temperature settings, wastewater discharge rate/pattern, and hot water discharge mode (continuous or intermittent). Results showed that the DESTE-WWSHP delivered comparable heat transfer performance to the IE-WWSHP, and thus, could serve as a replacement for the latter design. Specifically, the water temperature in the water storage tank was more uniformly distributed in the DESTE-WWSHP than the IE-WWSHP; the DESTE-WWSHP exhibited higher water heating capacity than the IE-WWSHP in the continuous hot water discharge mode. The DESTE has a heat transfer coefficient 3.1 times higher than that of the IE unit on the wastewater side. At the same heating capacity, the DESTE was far more compact with its compactness 7 times higher and its volume 91.71% smaller than the IE unit, leading to considerable savings in room space and materials. Additional benefits offered by this DESTE-WWSHP included reduced labor and power costs for cleaning heat exchanger, and decreased odor nuisance.

Being environmental friendly and with the potential of energy-efficiency, ground-source heat pump (GSHP) systems are widely used. However, in southern China, there exists large difference between cooling load in summer and heating load in winter. Thus the increase of soil temperature gradually year-by-year will decrease the COP of the GSHP system. In this paper, the configuration of a vertical dual-function geothermal heat exchanger (GHE) used in an integrated soil cold storage and ground-source heat pump (ISCS&GSHP) system, which charged cold energy to the soil at night and produced chilled water at daytime in summer, and supplied hot water for heating in winter, is presented. This is then followed by reporting the development of the mathematical model for the GHE considering the impact of the coupled heat conduction and groundwater advection on the heat transfer between the GHE and its surrounding soil. The GHE model developed was then integrated with a water-source heat pump and a building energy simulation program together for a whole ISCS&GSHP system. Then the operation performance of the ISCS&GSHP system used for a demonstration building is studied. These simulation results indicated the system transferred 71.505% of the original power consumption at daytime to that at nighttime for the demonstration building. And the net energy exchange in the soil after one-year operation was only 2.28% of the total cold energy charged. Thus we can see the feasibility of the ISCS&GSHP system technically.

Being environmental friendly and with the potential of energy-efficiency, more and more ground-source heat pump (GSHP) systems are being widely used. However, the influence of groundwater advection on the performance of the geothermal heat exchanger (GHE) in a GSHP is not still clearly known. In this paper, the configuration of a vertical dual-function GHE used in an integrated soil cold storage and ground-source heat pump (ISCS&GSHP) system, which charged cold energy to soil at night and produced chilled water in daytime in summer, and hot water for heating in winter, is firstly presented. This is then followed by a report on a mathematical model for the GHE considering the impact of the coupled heat conduction and groundwater advection on the heat transfer between the GHE and its surrounding soil. The GHE model developed was then integrated into a previously developed simulation program for an ISCS&GSHP system, and the operating performances of the GHE in an ISCS&GSHP system having a vertical dual-function GHE have been studied by simulation and reported. These simulation results, firstly seen in open literature, are much helpful to the design of a GHE buried in soil and widely used in GSHP systems or ISCS&GSHP systems.

The recovery of condenser heat in air conditioners is attractive because of its great economy and environmental value. This work experimentally studies a modified air conditioner with a domestic hot water supply (ACDHWS) that operates in the space-cooling and water-heating mode. The working principles and the basic features of the ACDHWS are introduced in this paper. This is followed by an experimental study on dynamic operation characteristics, hot water supply performance, energy efficiency and the temperature distribution of hot water in the storage tank of the unit. The results show that the ACDHWS can reliably be used to heat domestic hot water without losing its cooling capacity when it is controlled well in different operation conditions. Comparatively, the coefficient of comprehensive energy performance (COP2) of the ACDHWS is about 38.6% higher than that of the original unit. Furthermore, it is proved that the ACDHWS can continuously supply hot water for householders if a suitable hot water storage tank is installed. All these may be much helpful to develop a perfect ACDHWS product.