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Net-zero energy buildings (NZEBs) have been considered as an efficient solution to limit the growing energy consumption and pollution emissions from buildings. The configurations and the capacities of the implemented renewable energy systems in NZEBs should be wisely selected to ensure the intended performance objective. This study aims to optimize, investigate and compare six renewable energy solution sets for designing NZEBs in three different climates: Indore (cooling dominant), Tromso (heating dominant), and Beijing (mixed climate). The optimization is carried out using a multi-criteria decision-making methodology. The implemented methodology is composed of two phases. In the first phase, the optimal sizes of solution sets in each climate are derived and analyzed. The effectiveness of optimal solution sets is evaluated with respect to economy, environment, energy and grid stress. In the second phase, recommendations for each region are offered according to the overall performance evaluation results. The evaluation criteria include life cycle cost, payback period, levelized cost of energy, CO 2 eq emissions, grid interaction index, load matching index, and total energy consumption. The analyses show that, in Indore (hot climate), it is recommended to utilize the solution set composed of air source heat pump for cooling and flat plate solar collectors for domestic hot water (DHW) production. In Tromso (cold climate), the use of a biodiesel generator is promising to produce both electricity and hot steam for heating as well as DHW use. In Beijing (mixed climate), it is recommended to utilize electric chillers for cooling and natural gas condensing boiler for heating and DHW usage. • Renewable energy solution sets for net zero energy building are optimized. • Hot, cold and mixed climates are investigated. • Building performance is analyzed in terms of energy, cost, and CO 2eq emissions. • Load matching and grid stress analysis is conducted. • Suitable design options for each climate are offered. [ABSTRACT FROM AUTHOR]

Abstract Worldwide, the residential buildings are consuming a considerable amount of energy. The high potential of buildings towards energy efficiency has drawn special attention to the passive design parameters. A comprehensive study on optimal passive design for residential buildings is presented in this paper. Twenty-five different climates are simulated with the aim to produce best practices to reduce building energy demands (for cooling and heating) in addition to the life-cycle cost (LCC). The occupants' adaptive thermal comfort is also improved by implementing the appropriate passive cooling strategies such as blinds and natural ventilation. In this respect, the implemented methodology is composed of four phases: building energy simulation, optimization, Multi-criteria Decision Making (MCDM), sensitivity study, and finally an adaptive comfort analysis. An optimal passive solution of the studied building indicates the potential to save up to 54%, 87% and 52% of the cooling demands (Qcool), heating demands (Qheat) and LCC respectively with respect to the initial configuration. The obtained optimal passive parameters are validated with the National Renewable Energy Laboratory NREL benchmark for low energy building's envelope. Additionally, the integrated passive cooling strategies have demonstrated its competency since it leads to a significant overheating decrease. Highlights • Residential building's passive design parameters are optimized. • Effect of different climates of Köppen Geiger classification is studied. • Thermal comfort and energy performance of the case-studies are significantly enhanced. • Passive cooling strategies lead to adequate thermal comfort and fewer cooling systems. [ABSTRACT FROM AUTHOR]

The performance of a flat-plate solar collector is usually assessed by its efficiency. This efficiency is normally defined on a steady-state basis, which makes it difficult to correctly track the instantaneous performance of the collector in various case-studies. Accordingly, this paper proposes an improved definition of instantaneous efficiency of a flat-plate solar collector used as a part of a solar water heating system. Using a predeveloped model by the authors for such a system, the proposed efficiency-definition is examined and compared with the conventional one for specific case studies. The results show that the improved definition of efficiency records reasonable values, i.e., no over-range values are observed contrast to the case of conventional efficiency-definition. Furthermore, this suggested efficiency approximately coincides with the conventional one at a wide range of time, as long as the system is operating in the so-called trans-steady-state phase or when the system is off-operational provided that the instantaneous rate of heat stored in the heat transfer fluid (HTF) is less than or equal to zero. As a result, the improved efficiency-definition yields more realistic results in reflecting the performance of a flat-plate collector in an active solar water heating system and is recommended to be used. [ABSTRACT FROM AUTHOR]

Enhancing efficiency, meeting environmental standards, and preserving fuel resources are highly important objectives in power generation systems, at a time where world is endangered by several energetic, environmental, and health crises. Thus, better designs are constantly sought to increase the performance of such systems. In this study, an environment friendly trigeneration system based on solid oxide fuel cell (SOFC) is selected and designed for domestic applications. Negligible emissions are thus recorded as the SOFC is fueled solely by hydrogen. The system is modeled following three steps: the energy simulation of residential building to determine its demands, the system’s prime mover–SOFC, and the trigeneration recovery system ensuring the maximum coverage of heating, cooling, and domestic hot water loads respectively. The system is then evaluated under the 4-E assessment criteria: energy, exergy, economy, and environment. Depending on these criteria, the system is multi-objectively optimized. Two operation strategies are adopted: off-grid following electrical load and on-grid base load operations. Optimization results show that the trigeneration system is energetically and economically superior and performs well under both strategies. The maximum energy and exergy efficiencies (65.2% and 45.77%) and minimum system cost rate (22.2 cents/kWh) are obtained under on-grid base load operation. [ABSTRACT FROM AUTHOR]

Energy demands and fuel costs are continuously increasing which necessitates either finding new energy resources or improving current energy systems. Multi-generation systems as cogeneration (CHP) and trigeneration (CCHP) are interesting solutions that can enhance energy generation performance and fix some interrelated reliability, safety, and flexibility issues. In this regard, many prime mover technologies are available in which the choice between each is greatly dependent on end-user conditions and preferences. Yet, it is prior to choose whether cogeneration or trigeneration is more suitable. Thus, this paper reviews the main differences between CHP and CCHP systems in most available prime mover technologies, after which a selection table is proposed in order to make appropriate multi-generation system installation choices, depending on specific case study parameters. In general, CHP and CCHP systems yield positive technical and environmental performance impacts. [ABSTRACT FROM AUTHOR]

The hybrid cooling system has proved to be an energy saving technology for building air conditioning. Numerous systems combining different cooling processes or cooling machines have been proposed and investigated in the literature. A properly selected hybrid cooling system offers a great reduction in energy consumption and a coefficient of performance improvement varying according to different climates and system designs. This paper provides a detailed review of existing hybrid cooling systems with their corresponding individual cooling machines. A brief state of the art of the most common individual cooling systems in hybrid cooling for building use is firstly presented. Then, the hybrid cooling systems are classified into five main categories according to the combination of cooling processes or machines: Vapor compression based cooling, absorption based cooling, adsorption based cooling, desiccant-evaporative and multi-evaporator cooling. In each category, the studied configurations and the benefits of each hybridization method are presented. It is found that each hybrid system combines the advantages of the different cooling processes used. However, a hybrid system could have a negative repercussion if it does not match the climatic zone where it will be used. Consequently, a selection scheme to recommend the best hybrid cooling system for minimum energy consumption and pollution emissions in buildings according to different parameters is proposed. [ABSTRACT FROM AUTHOR]

Cooling demand in the building sector is growing rapidly; thermal energy storage systems using phase change materials (PCM) can be a very useful way to improve the building thermal performance. The right use of PCM in the envelope can minimize peak cooling loads, allow the use of smaller HVAC technical equipment for cooling, and has the capability to keep the indoor temperature within the comfort range due to smaller indoor temperature fluctuations. This article presents an overview of different PCM applications in buildings for reducing cooling loads under different climate conditions, and the factors affecting the successful and the effective use of the PCM. Many drawbacks have been found in PCM applications, mainly the intense impact of summer weather conditions over the PCM performance, which prohibits its complete solidification during night, and thus, limiting its effectiveness during the day. Proposed solutions are reviewed in this article. Finally, a topology diagram is presented to summarize the steps leading to an effective use of PCM in building applications. [ABSTRACT FROM AUTHOR]

Electricity, heating, and cooling are the three main components constituting the tripod of energy consumption in residential, commercial, and public buildings all around the world. Their separate generation causes higher fuel consumption, at a time where energy demands and fuel costs are continuously rising. Combined cooling, heating, and power (CCHP) or trigeneration could be a solution for such challenge yielding an efficient, reliable, flexible, competitive, and less pollutant alternative. A variety of trigeneration technologies are available and their proper choice is influenced by the employed energy system conditions and preferences. In this paper, different types of trigeneration systems are classified according to the prime mover, size and energy sequence usage. A leveled selection procedure is subsequently listed in the consecutive sections. The first level contains the applied prime mover technologies which are considered to be the heart of any CCHP system. The second level comprises the heat recovery equipment (heating and cooling) of which suitable selection should be compatible with the used prime mover. The third level includes the thermal energy storage system and heat transfer fluid to be employed. For each section of the paper, a survey of conducted studies with CHP/CCHP implementation is presented. A comprehensive table of evaluation criteria for such systems based on energy, exergy, economy, and environment measures is performed, along with a survey of the methods used in their design, optimization, and decision-making. Moreover, a classification diagram of the main CHP/CCHP system components is summarized. A general selection approach of the appropriate CCHP system according to specific needs is finally suggested. In almost all reviewed works, CCHP systems are found to have positive technical and performance impacts. [ABSTRACT FROM AUTHOR]

Highlights: [•] Proposition of a hybrid water heating system. [•] Numerical dynamic modeling of the proposed hybrid system. [•] Simulations for typical winter and summer days in the Lebanese climate. [•] Development of an energetic, economic optimal management problem for the proposed hybrid system. [Copyright &y& Elsevier]

Abstract: This paper presents a dynamic simulation model to predict the performance of an ASHPWH (air source heat pump water heater). The developed model is used to assess its performance in the Lebanese context. It is shown that for the four Lebanese climatic zones, the expected monthly values of the average COP (coefficient of performance) varies from 2.9 to 5, leading to high efficiencies compared with conventional electric water heaters. The energy savings and GHG (greenhouse gas) emissions reduction are investigated for each zone. Furthermore, it is recommended to use the ASHPWH during the period of highest daily ambient temperatures (noon or afternoon), assuming that the electricity tariff and hot water loads are constant. In addition, an optimal management model for the ASHPWH is developed and applied for a typical winter day of Beirut. Moreover, the developed dynamic model of ASHPWH is used to compare the performance of three similar systems that differ only with the condenser geometry, where results show that using mini-condenser geometries increase the COP (coefficient of performance) and consequently, more energy is saved as well as more GHG emissions are reduced. In addition, the condenser “surface compactness” is increased giving rise to an efficient compact heat exchanger. [Copyright &y& Elsevier]

Abstract: This paper presents a review of the energy status, conventional and renewable, in Lebanon and illustrates their problems with the suggested recommendations. In addition, a detailed review of the principal directorates of the electricity of Lebanon Company (EDL) is also presented all along with the existing problems and recommended solutions. An economic, environmental optimization of different power sources is studied, where three scenarios are introduced based on the fuel source of different CCGT power plants. The results emphasized on the maximum possible use of wind energy and natural gas in electricity generation. Based on the optimization study, a five-year master plan for electricity generation is modeled. The suggested plan has an investment capital cost of 5553 M$ with the savings and additional incomes being 5900 M$ compared to EDL financial status in the adopted base year, 2009. In addition, this plan exceeds the trend to introduce a 12% share of renewable energy in the power sector by 2020, where the share is supposed to be about 15% out of the total installed capacity before this date. The concluding remarks highlight the role of politics in the development of the energy sector. [Copyright &y& Elsevier]

Integrating heat exchanger pipes with structural foundations in one system has created a new renewable solution for buildings' thermal loads. However, the interaction between thermal and geotechnical loads makes their design more complex and challenging. This review-study represents the current state of knowledge about the thermal and thermo-mechanical behaviors of energy piles. It also investigates the key parameters that affect their design concerning the piles' dimensions, the arrangement of pipes, concrete admixture, and fluid characteristics. It is found that the thermal efficiency improves significantly by increasing the number of pipes inside the piles and by adding thermally conductive materials to the concrete within acceptable limits. Besides, this paper reviews most of the studies conducted on optimizing vertical ground heat exchangers coupled with heat pumps. Objective functions, decision variables, design constraints, and optimization methods are specified and listed. It is concluded that a multi-objective optimization is highly recommended to enhance the dual performance of an energy pile system coupled with a heat pump using the 4E evaluation criteria (energy, exergy, economy, and environment) while ensuring the safety of the foundation under thermal cyclic loads. [ABSTRACT FROM AUTHOR]

Abstract The application of an innovative translucent superinsulated latent heat storage wall, combining transparent insulation material and phase change materials (TIM-PCM wall), on the envelope of a typical office under different climates is evaluated. Energy and economic analysis related to this application are presented. The simulation process is carried out using an experimentally validated numerical model. The results show that the incorporation of the TIM-PCM wall, on the south orientation, is more efficient than the use of a double-glazed in all considered climates. The optimum TIM-PCM wall area is evaluated economically through life-cycle cost and payback period analysis. The purpose is to ensure effective performance of the wall in each climate and at the same time to ensure economic viability. The results show that, in polar and subarctic climates, the application of the TIM-PCM wall has a high economic value and the investment appears to be attractive, the payback period being 10.5 years and 7.8 years respectively. In Dras (continental climate), the use of the wall is found economically unfeasible due to low energy prices and high discount rates. At current prices, the TIM-PCM wall investment in Sacramento (Mediterranean climate) and Toronto (Humid continental) does not offer economic benefits. Highlights • Application of the TIM-PCM wall under different climates. • Energy and economic analysis related to the application of the TIM-PCM wall. • Evaluation of the optimum TIM-PCM wall area in each climatic condition. • Economic viability depends on climatic conditions, energy price and investment cost. [ABSTRACT FROM AUTHOR]

This paper investigates the thermal performance of a translucent solar wall providing, concurrently, storage and restitution of heat, super thermal-acoustic insulation and daylighting to the interior environment. The wall is composed of glazing, silica aerogel used as a transparent insulation material (TIM) and glass bricks filled with fatty acid, an eutectic phase change material (PCM). To assess the TIM–PCM wall thermal behavior, experimentations were conducted in-situ in a full-sized test cell located in Sophia Antipolis, southern France. Experimental data shows that the tested wall is more effective in winter and might cause overheating during the summer mainly due to solar gains and un-cycling behavior of PCM which remains in liquid state. To enhance the energy performance of the wall in summertime, a numerical model describing the heat transfer mechanisms occurring in the PCM layer in combination with the other transparent wall layers is developed. Then, the model of the wall is linked to TRNSYS software to assess the thermal performance of the whole building. The numerical model is validated experimentally and a good agreement is shown comparing the simulated values with the measured data for seven consecutive days in summer and winter. The importance of considering the natural convection effect in the liquid PCM is also demonstrated. Moreover, it was shown that shading devices can effectively reduce overheating while natural night ventilation decreases the indoor temperature without affecting the PCM performance since the outdoor temperature is always higher than the phase change temperature. The use of a glass with selective solar reflection properties depending on the season instead of the ordinary glazing is shown also to be very effective way to overcome the overheating problem. Finally, the TIM-PCM wall is tested under different climate conditions and passive solutions are given to ensure thermal comfort in summer season. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a review of the progress made in analytical modeling of 2D and 3D textile composites is presented. The review covers the most known analytical models developed in the last 30years to evaluate the elastic properties of textile composites. A discussion of these models is presented, where the corresponding advantages and disadvantages are revealed. In addition, a comparative study of some selected analytical models is presented. Results obtained from previous analytical, numerical and experimental studies are presented in order to show the potential of investigated analytical models. It is shown that recently developed analytical models, applied on different kinds of textile composites, could yield good results, while maintaining more flexibility, easy to apply and the less time consuming in comparing with numerical FE (Finite Element) models. [Copyright &y& Elsevier]

Abstract: An improved analytical modeling, three stages homogenization method “3SHM”, of a 2.5D interlock woven composite is proposed. The development of the analytical model based on mixed iso-strain and iso-stress assembling models (the stiffness and the compliance averaging models) is presented. A finite element (FE) modeling is carried out in order to use its results in the development of the analytical model. It is proved that a model based only on an iso-strain condition could not give accurate results, while a mixed iso-strain and iso-stress model yields more accurate estimations. the developed homogenization method as well as the geometrical modeling, that takes into account the real geometry of undulated yarns, proposed by the analytical model leads to very good agreement in comparing with results obtained from FE models and available experimental data from the literature. [Copyright &y& Elsevier]

It is seen that 2.5D interlocks are particular reinforcements for high advanced applications (i.e., spatial and aeronautics fields) that are believed to have a high structural potential. This kind of reinforcement entails to consider the composite as a structure because interlocks are built by crossing the warp yarns with the weft (or fill) yarns in the three directions. In this article, a new numerical and analytical model is proposed. To evaluate the mechanical behavior, one may obtain numerically, the anisotropic elastic engineering constants from a finite element model (FEM). This technique of virtual testing consists of modeling the composite at the meso-scale to obtain a macro-scale response with a stress—strain analysis. At the moment, numerical simulations of such materials mainly involve geometrical models and automated tetrahedral meshes that make it difficult to cope with the orthotropic behavior of yarns materials. We thus propose a new meshing methodology to build an elementary volume made of tetrahedra for the isotropic matrix and of mapped hexaedra for the transversely isotropic yarns in order to achieve the FE discretization. A new analytical model is also been proposed, based on a geometrical modeling of the yarns using sinusoidal function and on homogenization at the macrolevel based on both iso-strain and iso-stress assumptions. This model allows the estimation of stiffness matrix of the composite in terms of the properties of its constituents and the geometry of the fabric. Two 2.5D interlock composites from the ‘layer—layer’ family are studied where the nine engineering constants are evaluated. The FEM and the analytical model show a good agreement with each other and with available in-plane Young’s modulus and Poisson’s ratio experimental results. [ABSTRACT FROM AUTHOR]

This study experimentally investigates the supercooling and natural convection behavior in three PCM, namely pure octadecane (organic), a eutectic PCM, and sodium acetate trihydrate (inorganic). The aim is to explore the effect of different factors on the degree of supercooling and on the natural convection, and to provide data for numerical simulation models. Results show that the type of PCM, the temperature of the cooling fluid, and mechanical shocks have a direct effect on the degree of supercooling. The supercooled PCM shows a high sensitivity to any changes in the applied conditions. The thermal insulation of the unheated PCM boundaries has a major effect on the solidification and melting dynamics and topology, particularly regarding the solid-liquid interface. The cross-sectional temperature profiles, the inclination of the solid-liquid interface, and the melting rate show that regardless of the PCM, natural convection plays a significant role during heating but not during cooling. [ABSTRACT FROM AUTHOR]

In this article, the problem that is faced when the developed analytical model is applied to 2.5D interlocks of the ‘yarn—yarn’ type is discussed. The difficulty encountered is taking into account the influence of the number of weft yarns covered by the warp yarn. Different architectures of these interlocks will have the same stiffness matrix when modeled with the developed analytical model that uses the volume proportion of the three phases: warp, weft, and matrix. The influence of the number of weft yarns on the longitudinal Young’s modulus is studied. A corrective function has been evaluated using a finite element numerical modeling of four fictive woven composites created with ‘ANSYS’ software. These woven composite have the same undulated warp and linear weft yarns, while they differ in the number of weft yarns covered by a warp yarn. The longitudinal Young’s modulus is evaluated for each composite using a numerical model which is also presented in this study. Moreover, a cross-ply laminate (0,90) is modeled by the classical laminate theory in the estimation procedure of the corrective function. The corrected longitudinal Young’s moduli show better agreement with numerical results compared to noncorrected ones. [ABSTRACT FROM AUTHOR]