An Analytical Approach for Computing the Coefficient of Refrigeration Performance in Giant Inverse Magnetocaloric Materials

An analytical approach for computing the coefficient of refrigeration performance (CRP) was described for materials that exhibited a giant inverse magnetocaloric effect (MCE), and their governing thermodynamics were reviewed. The approach defines the magnetic work input using thermodynamic relationships rather than isothermal magnetization data discretized from the literature. The CRP was computed for only cyclically reversible temperature and entropy changes in materials that exhibited thermal hysteresis by placing a limit on their operating temperature in a thermodynamic cycle. The analytical CRP serves to link meaningful material properties in first-order MCE refrigerants to their potential work and efficiency and can be employed as a metric to compare the behaviors of dissimilar alloy compositions or for materials design. We found that an optimum in the CRP may exist that depends on the applied field level and Clausius–Clapeyron (CC) slope. Moreover, through a large literature review of NiMn-based materials, we note that NiMn(In/Sn) alloys offer the most promising materials properties for applications within the bounds of the developed framework.

UASB Performance and Perspectives in Urban Wastewater Treatment at Sub-Mesophilic Operating Temperature

UASBs present several advantages compared to conventional wastewater treatment processes, including relatively low construction cost facilities, low excess sludge production, plain operation and maintenance, energy generation in the form of biogas, robustness in terms of COD removal efficiency, pH stability, and recovery time. Although anaerobic treatment is possible at every temperature, colder climates lead to lower process performance and biogas production. These factors can be critical in determining the applicability and sustainability of this technology for the treatment of urban wastewater at low operating temperature. The purpose of this study is the performance evaluation of a pilot-scale (2.75 m3) UASB reactor for treatment of urban wastewater at sub-mesophilic temperature (25 °C), below the optimal range for the process, as related to biogas production and organic matter removal. The results show that, despite lower methane production and COD removal efficiency compared to operation under ideal conditions, a UASB can still achieve satisfactory performance, and although not sufficient to grant effluent discharge requirements, it may be used as a pretreatment step for carbon removal with some degree of energy recovery. Options for UASB pretreatment applications in municipal WWTPs are discussed.

Heat Flux and Thermal Characteristics of Electrically Heated Windows: A Case Study

Energy loss through windows can be high relatively compared to other opaque surfaces because insulation performance of fenestration parts is lower in the building envelope. Electrically heated window systems are used to improve the indoor environment, prevent condensation, and increase building energy efficiency. The purpose of this study is to analyze the thermal behaviors of a heated window under a field experiment condition. Experiments were conducted during the winter season (i.e., January and February) with the energy-efficient house that residents occupy. To collect measured data from the experimental house, temperature and heat flux meter sensors were used for the analysis of heat flow patterns. Such measured data were used to calculate heat gain ratios and compare temperature and dew point distribution profiles of heated windows with input power values under the changed condition in the operating temperature of the heated glazing. Results from this study indicated that the input average heat gain ratio was analyzed to be 75.2% in the south-facing and 83.8% in the north-facing at nighttime. Additionally, compared to January, reducing the operating temperature of the heated glazing by 3 °C decreased the input energy in February by 44% and 41% for the south-facing and north-facing windows, respectively. Through such field measurement study, various interesting results that could not be found in controlled laboratory chamber conditions were captured, indicating that the necessity of establishing various control strategies should be considered for the development and commercialization of heated windows.

PERFORMANCE OF DIFFERENT PHOTOVOLTAIC TECHNOLOGIES FOR AMORPHOUS SILICON (A-SI) AND COPPER INDIUM GALLIUM DI-SELENIDE (CIGS) PHOTOVOLTAIC MODULES

In this work, the analysis of performance of two types of photovoltaic (PV) (Amorphous Silicon (a-Si) Copper Indium Gallium Diselenide (CIGS) technologies were achieved out under under Iraqi (Baghdad)climate conditions. The elevation of the selected site is 9 m above ground level. The experimental work covered the eight commercially available PV technologies. The two technologies that employed in this work are, Amorphous Silicon (a-Si) and Copper Indium Gallium Diselenide (CIGS). The total period of the experimental work was 7 months, and the data were analyzed simultaneously. Special attention is given to the influence of temperature and solar radiation the performance of the PV modules. Where, it was proposed a simple I-V curve test for PV modules. The results showed that the proposed system successfully experimentally extracted I-V curves of the selected two PV modules (amorphous and CIGS solar modules). The maximum values of power (Pmax) at solar radiation intensity 750 W/m² are 2.742 W, and 2.831 W for amorphous silicon and copper indium gallium di-selenide respectively. This is occurred because the lowest solar module operating temperature (19 oC and 17 oC for solar radiation 750 and 1000 W/m2 respectively) and ambient temperature (7 oC) and for Jan., 2021 than other months. Consequently, the same behavior for the two modules at solar irradiance 1000 W/m2 with the highest power value; 2.680 W, and 3.198 W of amorphous silicon and copper indium gallium di-selenide respectively. Furthermore, the minimum values of power (Pmax) at solarradiation intensity 750 W/m² are 2.530, and 2.831 for amorphous silicon and copper indium gallium di-selenide respectively because we have the highest solar module operating temperature (57 oC, and 55 oC respectively) and ambient temperature (45 oC) for April, 2021 than other months. Consequently, the same behavior for the two modules at solar irradiance 1000 W/m2 with the highest power value; 2.680 W, and 3.198 W of amorphous silicon and copper indium gallium di-selenide respectively. The highest efficiency can be notes for CIGS solar module with a value 7.3%, while the lowest one is 5.5% for amorphous solar module.

High-operating-temperature MWIR photodetector based on a InAs/GaSb superlattice grown by MOCVD

We demonstrate a high-operating-temperature (HOT) mid-wavelength InAs/GaSb superlattice heterojunction infrared photodetector grown by metal–organic chemical vapor deposition. High crystalline quality and the near-zero lattice mismatch of a InAs/GaSb superlattice on an InAs substrate were evidenced by high-resolution X-ray diffraction. At a bias voltage of –0.1 V and an operating temperature of 200 K, the device exhibited a 50% cutoff wavelength of ~ 4.9 μm, a dark current density of 0.012 A/cm2, and a peak specific detectivity of 2.3 × 109 cm·Hz1/2 /W.