• Energy Research
• other engineering and technologies close
• CA close
• Applied Energy close

Abstract Attention is devoted to the application of cylindrical-parabolic solar concentrators in the intermediate temperature range for which wide receivers are used. Suitable indices that describe the performance of the concentrator are defined and evaluated. The effect of each individual parameter on total concentrator performance is investigated. The results of the analysis are presented as a set of graphs which can be used easily when designing parabolic concentrators.

Abstract This paper introduces a new switching means giving a real time optimum connection mode of domestic appliances on either the electrical grid or a photovoltaic panel (PVP) output. A fuzzy algorithm makes the decision which ensures the optimal energy-management based on PVP generation and appliances states with respect to energy-saving criteria. Validation is driven on a 1 kW peak (kWp) PVP and domestic appliances of different powers installed at the Energy and Thermal Research Centre (CRTEn) in the north of Tunisia. Results confirm that energy saved during daylight is 80–90% of the PVP generated energy.

Applied Energy, 258 ISSN:0306-2619 ISSN:1872-9118

Abstract The transport of electrons through the gas diffusion layer (GDL) of polymer electrolyte membrane (PEM) fuel cells has a significant impact on the optimal design and operation of PEM fuel cells and is directly affected by the anisotropic nature of the carbon paper material. In this study, a three-dimensional reconstruction of the GDL is used to numerically estimate the directional dependent effective electrical conductivity of the layer for various porosity values. The distribution of the fibers in the through-plane direction results in high electrical resistivity; hence, decreasing the overall effective electrical conductivity in this direction. This finding is in agreement with measured experimental data. Further, using the numerical results of this study, two mathematical expressions were proposed for the calculation of the effective electrical conductivity of the carbon paper GDL. Finally, the tortuosity factor was evaluated as 1.7 and 3.4 in the in- and through-plane directions, respectively.

Abstract Smart energy management mandates a more decentralized energy infrastructure, entailing energy consumption information on a local level. Household-based energy consumption trends are becoming important to achieve reliable energy management for such local power systems. However, predicting energy consumption on a household level poses several challenges on technical and practical levels. The literature lacks studies addressing prediction of energy consumption on an individual household level. In order to provide a feasible solution, this paper presents a framework for predicting the average daily energy consumption of individual households. An ensemble method, utilizing information diversity, is proposed to predict the day-ahead average energy consumption. In order to further improve the generalization ability, a robust regression component is proposed in the ensemble integration. The use of such robust combiner has become possible due to the diversity parameters provided in the ensemble architecture. The proposed approach is applied to a case study in France. The results show significant improvement in the generalization ability as well as alleviation of several unstable-prediction problems, existing in other models. The results also provide insights on the ability of the suggested ensemble model to produce improved prediction performance with limited data, showing the validity of the ensemble learning identity in the proposed model. We demonstrate the conceptual benefit of ensemble learning, emphasizing on the requirement of diversity within datasets, given to sub-ensembles, rather than the common misconception of data availability requirement for improved prediction.

Abstract The Net Zero Energy House (NZEH) presented in this paper is an energy efficient house that uses available solar technologies to generate at least as much primary energy as the house uses over the course of the year. The computer simulation results show that it is technically feasible to reach the goal of NZEH in the cold climate of Montreal. In terms of the life cycle energy use, which considers the operating and embodied energy of the house, the energy payback time is 8.4–8.7 years, when the NZEH is compared with an average house that complies with the provincial code. The energy payback ratio of the combisystem is 3.5–3.8 compared with the heating system of conventional house. By converting solar energy, the combisystem supplies at least 3.5 times more energy than the energy invested for manufacturing and shipping the system. The life cycle cost analysis of the NZEH shows, however, that due to the high cost of the solar technologies and the low cost of electricity in Montreal, financial payback is never achieved.

Abstract The present paper examines the co-conversion of waste activated sludge and birchwood sawdust to bio-oil via hydrothermal liquefaction. The purpose of using the sawdust with sludge was to increase the solids concentration using another waste material for possible resource recovery. The operating conditions including reaction temperature, reaction time and solids concentration were optimized based on the response surface methodology for the maximum bio-oil production. A maximum of 33.7 wt% bio-oil yield was obtained at optimum operating conditions of 310 °C, 10 min, and 10 wt% concentration. Comparison of this oil with the oil produced from only sawdust showed a significant improvement in the molecular weight of the bio-oil by having lower molecular weight (hence less viscosity), indicating the presence of lighter components, with a slight decrease in bio-oil yield. The optimized operating condition could be used to effectively co-liquefy waste activated sludge and sawdust with the advantage of producing higher quality bio-oil with respect to molecular weight. The water-soluble product which is the largest fraction of by-products from the co-conversion was tested as a feedstock for biogas production through anaerobic digestion and resulted in 800 ml bio-methane production per 0.816 g of TOC or 2.09 g of COD of this waste stream.

Abstract A conventional thermal response test (TRT) provides a bulk estimate of the subsurface and borehole thermal properties over the length of the ground heat exchanger (GHE). The measurement of temperature inside the borehole during a TRT can be carried out to further determine thermal properties at different depths. The analysis of the transient temperature response is commonly performed with an analytical solution assuming a constant heat injection rate, which does not reproduce the effect of water flow along the pipe of the GHE. This heat transport mechanism can induce a temporal variation of the heat injection rate at depth although heat injection remains constant at the surface. Analysis of synthetic data generated with numerical simulations of TRTs in a layered subsurface was consequently carried out to verify this analytical approach. The program MLU was selected for analyzing the TRTs because of its capacity to take into account multiple layers. Results indicated that the analysis can be improved by accounting for variable heat injection rates determined inside the GHE. Estimation of both the subsurface thermal conductivity and the borehole thermal resistance was within 20% of the expected values, except when the thermal conductivity of the subsurface is low. For a simulation case carried out with a subsurface layer that had a thermal conductivity as low as 1 W m −1 K −1 , the borehole thermal resistance could not be determined with significant accuracy.