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371 KiB

Open AccessArticle

Greening Public Buildings: ESCO-Contracting in Danish Municipalities

by Jesper Ole Jensen, Susanne Balslev Nielsen and Jesper Rohr Hansen

Energies 2013, 6(5), 2407-2427; https://doi.org/10.3390/en6052407 - 6 May 2013

Cited by 26 | Viewed by 7351

Abstract

This paper presents current research on Danish municipalities’ use of Energy Service Companies (ESCO) as a way to improve the standard of public buildings and to increase energy efficiency. In recent years more and more municipalities have used ESCO-contracts to retrofit existing public [...] Read more.

This paper presents current research on Danish municipalities’ use of Energy Service Companies (ESCO) as a way to improve the standard of public buildings and to increase energy efficiency. In recent years more and more municipalities have used ESCO-contracts to retrofit existing public buildings, and to make them more energy efficient. At the moment 30 municipalities (of the 98 municipalities in Denmark) are involved in, or preparing, ESCO contracts. Nevertheless, ESCO-contracting still faces many challenges on the Danish market, as there is a widespread skepticism towards the concept amongst many stakeholders. The purpose of this paper is to discuss the various experience gained so far by municipalities use of ESCO-contracting, the different approached to ESCO-contracting being used in practice, as well as the different viewpoints drivers and barriers behind the development. The strong growth in ESCO-contracts reflects that the ESCO-concept fits well with a number of present problems that municipalities are facing, as well as a flexible adaptation to the local context in different municipalities. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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854 KiB

Open AccessArticle

Evaluation and Optimization of a Traditional North-Light Roof on Industrial Plant Energy Consumption

by Sigrid Adriaenssens, Hao Liu, Mariam Wahed and Qianchuan Zhao

Energies 2013, 6(4), 1944-1960; https://doi.org/10.3390/en6041944 - 3 Apr 2013

Cited by 2 | Viewed by 12596

Abstract

Increasingly strict energy policies, rising energy prices, and a desire for a positive corporate image currently serve as incentives for multinational corporations to reduce their plants’ energy consumption. This paper quantitatively investigates and discusses the value of a traditional north-light roof using a [...] Read more.

Increasingly strict energy policies, rising energy prices, and a desire for a positive corporate image currently serve as incentives for multinational corporations to reduce their plants’ energy consumption. This paper quantitatively investigates and discusses the value of a traditional north-light roof using a complete building energy simulation and optimization framework. The findings indicate that the north-light system yields positive building energy performance for several climate zones, including: (i) Humid Subtropical; (ii) Semiarid Continental; (iii) Mediterranean; and (iv) Subtropical Highland. In the Subtropical Highland climate zone, for example, the building energy consumption of a north-light roof is up to 54% less than that of a conventional flat roof. Based on these positive findings, this paper further presents an optimization framework that alters the north-light roof shape to further improve its energy performance. To quantitatively guarantee a high probability of finding satisfactory designs while reducing the computational processing time, ordinal optimization is introduced into the scheme. The Subtropical Highland case study shows further energy building consumption reduction of 26% for an optimized north-light roof shape. The presented evaluation and optimization framework could be used in designing a plant with integrated north-lights roof that aim at energy efficiency while maintaining environmental occupant comfort levels. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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396 KiB

Open AccessArticle

Ventilation Heat Recovery from Wood-Burning Domestic Flues. A Theoretical Analysis Based on a Triple Concentric Tube Heat Exchanger

by Pierre Peigné, Christian Inard and Lionel Druette

Energies 2013, 6(1), 351-373; https://doi.org/10.3390/en6010351 - 15 Jan 2013

Cited by 13 | Viewed by 7737

Abstract

This paper presents a new air-heating system concept for energy-efficient dwellings. It is a system designed to heat a low-energy building by coupling a heat-recovery ventilation system with a three-fluid heat exchanger located on the chimney of a wood-pellet stove. The proposed work [...] Read more.

This paper presents a new air-heating system concept for energy-efficient dwellings. It is a system designed to heat a low-energy building by coupling a heat-recovery ventilation system with a three-fluid heat exchanger located on the chimney of a wood-pellet stove. The proposed work focuses on the heat transfer that occurs between flue gases, the ventilation air and the combustion air within a triple concentric tube heat exchanger with no insulation at its outer surface. The main objective is to predict outlet temperature for the specific geometry of the heat exchanger studied here. Thus, the governing differential equations are derived for a counter-co-current flow arrangement of the three fluids. Then analytical solutions for the steady-state temperature distribution are obtained as well as the amount of heat transferred to the outside. An expression for the effectiveness of the heat exchanger is also proposed. Based on these results, calculations are performed on a case study to predict the fluid temperature distribution along the heat exchanger. Finally, a parametric study is carried out on this case study to assess the influence of the relevant parameters on the effectiveness of the heat exchanger. In addition, computation of heat losses to the outside justifies whether insulation is needed. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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986 KiB

Open AccessArticle

Heating Energy and Peak-Power Demand in a Standard and Low Energy Building

by Miimu Airaksinen and Mika Vuolle

Energies 2013, 6(1), 235-250; https://doi.org/10.3390/en6010235 - 9 Jan 2013

Cited by 10 | Viewed by 6023

Abstract

Building energy efficiency legislation has traditionally focused on space heating energy consumption. This has led to a decrease in energy consumption, especially in space heating. However, in the future when more renewable energy is used both on site and in energy systems, the [...] Read more.

Building energy efficiency legislation has traditionally focused on space heating energy consumption. This has led to a decrease in energy consumption, especially in space heating. However, in the future when more renewable energy is used both on site and in energy systems, the peak energy demand becomes more important with respect to CO2 emissions and energy security. In this study it was found out the difference between space heating energy consumption was 55%–62% when a low energy and standard building were compared. However, the difference in peak energy demands was only 28%–34%, showing the importance of paying attention to the peak demands as well. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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1139 KiB

Open AccessArticle

Evaluation of the Water Scarcity Energy Cost for Users

by Chiara M. Fontanazza, Gabriele Freni, Goffredo La Loggia, Vincenza Notaro and Valeria Puleo

Energies 2013, 6(1), 220-234; https://doi.org/10.3390/en6010220 - 9 Jan 2013

Cited by 10 | Viewed by 7092

Abstract

In systems experiencing water scarcity and consequent intermittent supply, users often adopt private tanks that collect water during service periods and supply users when the service is not available. The tank may be fed by gravity or by private pumping stations depending on [...] Read more.

In systems experiencing water scarcity and consequent intermittent supply, users often adopt private tanks that collect water during service periods and supply users when the service is not available. The tank may be fed by gravity or by private pumping stations depending on the network pressure level. Once water resources are collected, the tank can supply users by gravity if it is located on the rooftop or by additional pumping if underground. Private tanks thus increase the energy cost of the water supply service for users by introducing several small pumping structures inside the network. The present paper aims to evaluate this users’ energy cost for different private tank configurations. A real case study was analysed, and the results showed that intermittent distribution causes inequalities not only in users’ access to water resource but also costs that users have to bear to have access to water. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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1025 KiB

Open AccessArticle

Experimental Study of a Triple Concentric Tube Heat Exchanger Integrated into a Wood-Based Air-Heating System for Energy-Efficient Dwellings

by Pierre Peigné, Christian Inard and Lionel Druette

Energies 2013, 6(1), 184-203; https://doi.org/10.3390/en6010184 - 8 Jan 2013

Cited by 14 | Viewed by 7651

Abstract

In this paper, experimental tests conducted on a new wood-based air-heating system for energy-efficient dwellings are presented. The main objective is to evaluate the resulting outlet temperatures and the amount of heat recovered by the ventilation air in order to assess feasibility and [...] Read more.

In this paper, experimental tests conducted on a new wood-based air-heating system for energy-efficient dwellings are presented. The main objective is to evaluate the resulting outlet temperatures and the amount of heat recovered by the ventilation air in order to assess feasibility and performance of coupling a mechanical ventilation heat-recovery unit and a triple concentric tube heat exchanger integrated into the chimney of a room-sealed wood-pellet stove to heat an entire house. After introducing the context of this work, the three main components of the combined system developed here, the coupling configuration adopted, as well as the protocol used and the sensors implemented on an experimental setup carried out in a laboratory are detailed in turn. Then, the heat transfer rates obtained from measurements for the various fluids as well as the effectiveness of the heat exchangers are presented and discussed. Finally, the resulting outlet temperatures of the three fluids exchanging in the triple concentric tube heat exchanger studied here are compared to those provided by analytical solutions obtained with a mathematical model. It is shown that heat transfer rates are predicted with a relative difference that is lower than 5% compared to experimental values and that such a system enables to cover all or most of heat losses in an energy efficient building. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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613 KiB

Open AccessArticle

Parameterization Studies of Solar Chimneys in the Tropics

by Alex Yong Kwang Tan and Nyuk Hien Wong

Energies 2013, 6(1), 145-163; https://doi.org/10.3390/en6010145 - 7 Jan 2013

Cited by 39 | Viewed by 10724

Abstract

The paper examines the effect of the solar chimney’s stack height, depth, width and inlet position on the interior performance (air temperature and speed at 1.20 m height above the ground) as well as proposes an optimal tropical solar chimney design. Simulations show [...] Read more.

The paper examines the effect of the solar chimney’s stack height, depth, width and inlet position on the interior performance (air temperature and speed at 1.20 m height above the ground) as well as proposes an optimal tropical solar chimney design. Simulations show that the output air temperature remains constant while the solar chimney’s width is the most significant factor influencing output air speed. The solar chimney’s inlet position has limited influence on the output air speed although regions near the solar chimney’s inlet show an increase in air speed. Furthermore, a regression model is developed based on the solar chimney’s stack height, depth and width to predict the interior air speed. To optimize solar chimney in the tropics, the recommendation is to first maximize its width as the interior’s width, while allowing its stack height to be the building’s height. Lastly, the solar chimney’s depth is determined from the regression model by allocating the required interior air speed. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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2787 KiB

Open AccessArticle

A Building Energy Efficiency Optimization Method by Evaluating the Effective Thermal Zones Occupancy

by Anna Laura Pisello, Michael Bobker and Franco Cotana

Energies 2012, 5(12), 5257-5278; https://doi.org/10.3390/en5125257 - 13 Dec 2012

Cited by 64 | Viewed by 10149

Abstract

Building energy efficiency is strongly linked to the operations and control systems, together with the integrated performance of passive and active systems. In new high quality buildings in particular, where these two latter aspects have been already implemented at the design stage, users’ [...] Read more.

Building energy efficiency is strongly linked to the operations and control systems, together with the integrated performance of passive and active systems. In new high quality buildings in particular, where these two latter aspects have been already implemented at the design stage, users’ perspective, obtained through post-occupancy assessment, has to be considered to reduce whole energy requirement during service life. This research presents an innovative and low-cost methodology to reduce buildings’ energy requirements through post-occupancy assessment and optimization of energy operations using effective users’ attitudes and requirements as feedback. As a meaningful example, the proposed method is applied to a multipurpose building located in New York City, NY, USA, where real occupancy conditions are assessed. The effectiveness of the method is tested through dynamic simulations using a numerical model of the case study, calibrated through real monitoring data collected on the building. Results show that, for the chosen case study, the method provides optimized building energy operations which allow a reduction of primary energy requirements for HVAC, lighting, room-electricity, and auxiliary supply by about 21%. This paper shows that the proposed strategy represents an effective way to reduce buildings’ energy waste, in particular in those complex and high-efficiency buildings that are not performing as well as expected during the concept-design-commissioning stage, in particular due to the lack of feedback after the building handover. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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763 KiB

Open AccessArticle

Development of a Terminal Control System with Variable Minimum Airflow Rate

by Young-Hum Cho

Energies 2012, 5(11), 4643-4664; https://doi.org/10.3390/en5114643 - 15 Nov 2012

Cited by 8 | Viewed by 6686

Abstract

A constant minimum airflow rate is used in conventional Single Duct Variable Air Volume Terminal Box control sequences. This control sequence can cause occupant discomfort or use excessive energy under partial load conditions. If the minimum airflow rate is higher than required; terminal [...] Read more.

A constant minimum airflow rate is used in conventional Single Duct Variable Air Volume Terminal Box control sequences. This control sequence can cause occupant discomfort or use excessive energy under partial load conditions. If the minimum airflow rate is higher than required; terminal boxes will have significantly more simultaneous heating and cooling; and AHUs will consume more fan power. Buildings will have indoor air quality problems if the minimum airflow rate is less than required. Many engineers and researchers have investigated advanced variable air volume terminal box control algorithms without a system retrofit for thermal comfort; indoor air quality and energy savings. In this study a developed control system with variable minimum airflow rate for Single Duct Variable Air Volume Terminal Boxes was applied and validated using an actual building and evaluated for comfort; indoor air quality and energy consumption. The energy consumption and thermal performance of terminal boxes using the conventional and proposed control algorithms were compared. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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1515 KiB

Open AccessArticle

An Energy and Water Resource Demand Estimation Model for Multi-Family Housing Complexes in Korea

by Dongjun Suh and Seongju Chang

Energies 2012, 5(11), 4497-4516; https://doi.org/10.3390/en5114497 - 13 Nov 2012

Cited by 13 | Viewed by 6714

Abstract

This paper proposes and develops a residential energy and resource consumption estimation model in the context of multi-family residential housing in Korea using a multi-layer perceptron (MLP) neural network. Eight indicators are introduced which affect the energy and water resource usage characteristics of [...] Read more.

This paper proposes and develops a residential energy and resource consumption estimation model in the context of multi-family residential housing in Korea using a multi-layer perceptron (MLP) neural network. Eight indicators are introduced which affect the energy and water resource usage characteristics of Korean residential complexes. The proposed model precisely estimated the electricity, gas energy and water consumption for each examined residential complex. In terms of validation, the results showed the highest level of agreement with actually collected datasets. The model shows promising prospects in providing necessary estimations, not only for optimally scaling and sizing energy- and water-related infrastructures, but also to promote reliable energy and resource savings through greenhouse gas (GHG) reduction planning in multi-family housing complexes. The model could also be of use in framing guidelines for the better planning of national or regional energy and resource policies and for forming a foundation of decision-making with definite references regarding the facility management of each apartment complex to enhance the energy and resource use efficiency at these locations. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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1652 KiB

Open AccessArticle

A DFuzzy-DAHP Decision-Making Model for Evaluating Energy-Saving Design Strategies for Residential Buildings

by Kuang-Sheng Liu, Sung-Lin Hsueh, Wen-Chen Wu and Yu-Lung Chen

Energies 2012, 5(11), 4462-4480; https://doi.org/10.3390/en5114462 - 9 Nov 2012

Cited by 36 | Viewed by 8155

Abstract

The construction industry is a high-pollution and high-energy-consumption industry. Energy-saving designs for residential buildings not only reduce the energy consumed during construction, but also reduce long-term energy consumption in completed residential buildings. Because building design affects investment costs, designs are often influenced by [...] Read more.

The construction industry is a high-pollution and high-energy-consumption industry. Energy-saving designs for residential buildings not only reduce the energy consumed during construction, but also reduce long-term energy consumption in completed residential buildings. Because building design affects investment costs, designs are often influenced by investors’ decisions. A set of appropriate decision-support tools for residential buildings are required to examine how building design influences corporations externally and internally. From the perspective of energy savings and environmental protection, we combined three methods to develop a unique model for evaluating the energy-saving design of residential buildings. Among these methods, the Delphi group decision-making method provides a co-design feature, the analytical hierarchy process (AHP) includes multi-criteria decision-making techniques, and fuzzy logic theory can simplify complex internal and external factors into easy-to-understand numbers or ratios that facilitate decisions. The results of this study show that incorporating solar building materials, double-skin facades, and green roof designs can effectively provide high energy-saving building designs. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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2324 KiB

Open AccessArticle

Effects of a Green Space Layout on the Outdoor Thermal Environment at the Neighborhood Level

by Luis Ma. Bo-ot, Yao-Hong Wang, Che-Ming Chiang and Chi-Ming Lai

Energies 2012, 5(10), 3723-3735; https://doi.org/10.3390/en5103723 - 25 Sep 2012

Cited by 20 | Viewed by 7465

Abstract

This study attempted to address the existing urban design needs and computer-aided thermal engineering and explore the optimal green space layout to obtain an acceptable thermal environment at the neighborhood scale through a series of building energy and computational fluid dynamics (CFD) simulations. [...] Read more.

This study attempted to address the existing urban design needs and computer-aided thermal engineering and explore the optimal green space layout to obtain an acceptable thermal environment at the neighborhood scale through a series of building energy and computational fluid dynamics (CFD) simulations. The building-energy analysis software eQUEST and weather database TMY2 were adopted to analyze the electric energy consumed by air conditioners and the analysis results were incorporated to derive the heat dissipated from air conditioners. Then, the PHOENICS CFD software was used to analyze how the green space layout influences outdoor thermal environment based on the heat dissipated from air conditioners and the solar heat reemitted from the built surfaces. The results show that a green space located in the center of this investigated area and at the far side of the downstream of a summer monsoon is the recommended layout. The layouts, with green space in the center, can decrease the highest temperature by 0.36 °C. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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4597 KiB

Open AccessArticle

Reducing the Energy Demand of Multi-Dwelling Units in a Mediterranean Climate Using Solar Protection Elements

by Ángel L. León, Samuel Domínguez, Miguel A. Campano and Cristina Ramírez-Balas

Energies 2012, 5(9), 3398-3424; https://doi.org/10.3390/en5093398 - 6 Sep 2012

Cited by 22 | Viewed by 7522

Abstract

It is known that glazed openings are very important elements in the energetic behavior of buildings, especially in Mediterranean climates where there are many hours of solar radiation. The objective of this study was to determine the influence of solar protection on the [...] Read more.

It is known that glazed openings are very important elements in the energetic behavior of buildings, especially in Mediterranean climates where there are many hours of solar radiation. The objective of this study was to determine the influence of solar protection on the energy demand of public housing structures in these climates. To this end, the reduction in energy demand achieved by fixed solar protectors in combination with mobile protectors (blinds) was quantified, including an evaluation of the influence of their geometry, dimensions, degree of openness, and the orientation of the opening. To analyze and quantify energetic demand, a block of public housing units in a neighborhood of Seville (latitude 37°23' N) was used as a model. This block is typical of public housing in the Mediterranean region. Simulated energetic models were created using DesignBuilder, achieving reductions in the annual energy demand from 10% to 27% according to the orientation chosen. The results and conclusions of the study are applicable to new construction, energetic rehabilitation projects, and/or the improvement of existing buildings. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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2258 KiB

Open AccessArticle

Impacts of Ventilation Ratio and Vent Balance on Cooling Load and Air Flow of Naturally Ventilated Attics

by Shimin Wang and Zhigang Shen

Energies 2012, 5(9), 3218-3232; https://doi.org/10.3390/en5093218 - 29 Aug 2012

Cited by 14 | Viewed by 7397

Abstract

The impacts of ventilation ratio and vent balance on cooling load and air flow of naturally ventilated attics are studied in this paper using an unsteady computational fluid dynamics (CFD) model. Buoyancy-driven turbulent ventilations in attics of gable-roof residential buildings are simulated for [...] Read more.

The impacts of ventilation ratio and vent balance on cooling load and air flow of naturally ventilated attics are studied in this paper using an unsteady computational fluid dynamics (CFD) model. Buoyancy-driven turbulent ventilations in attics of gable-roof residential buildings are simulated for typical summer conditions. Ventilation ratios from 1/400 to 1/25 combined with both balanced and unbalanced vent configurations are investigated. The modeling results show that the air flows in the attics are steady and exhibit a general streamline pattern that is qualitatively insensitive to the variations in ventilation ratio and vent configuration. The predicted temperature fields are characterized by thermal stratification, except for the soffit regions. It is demonstrated that an increase in ventilation ratio will reduce attic cooling load. Compared with unbalanced vent configurations, balanced attic ventilation is shown to be the optimal solution in both maximizing ventilating flow rate and minimizing cooling load for attics with ventilation ratio lower than 1/100. For attics with ventilation ratios greater than 1/67, a configuration of large ridge vent with small soffit vent favors ventilating air flow enhancement, while a configuration of small ridge vent with large soffit vent results in the lowest cooling energy consumption. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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406 KiB

Open AccessArticle

Are the Greenhouse Gas Implications of New Residential Developments Understood Wrongly?

by Jukka Heinonen, Antti-Juhani Säynäjoki, Matti Kuronen and Seppo Junnila

Energies 2012, 5(8), 2874-2893; https://doi.org/10.3390/en5082874 - 6 Aug 2012

Cited by 15 | Viewed by 7293

Abstract

Built environment carbon reduction strategies materialize predominantly in city-level greenhouse gas (GHG) management, where new residential development appears as one of the key instruments. However, city-level assessments are often incapable of producing data at a community or neighborhood level and thus they may [...] Read more.

Built environment carbon reduction strategies materialize predominantly in city-level greenhouse gas (GHG) management, where new residential development appears as one of the key instruments. However, city-level assessments are often incapable of producing data at a community or neighborhood level and thus they may heavily underestimate the emissions from new construction. This paper explores the implications of low-energy residential construction as an instrument of climate change mitigation in the built environment and demonstrates why city-level approaches easily fail to identify the significance of the emissions from construction. We employ a hybrid life cycle assessment (LCA) approach to demonstrate that, when the temporal allocation of emissions from the construction and use phases is taken into account, construction phase emissions come to have a central role in finding effective GHG mitigation strategies—even when the emissions from all consumption activities during the use phase are included in the assessment. In fact, their role would seem to be so central that new residential construction cannot be utilized as an instrument of city carbon management, even over a relatively long period. While we analyze a case study from Finland, the analysis intends to highlight the situation throughout the globe. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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1525 KiB

Open AccessArticle

Towards Energy Demand Reduction in Social Housing Buildings: Envelope System Optimization Strategies

by Samuel Domínguez, Juan J. Sendra, Angel L. León and Paula M. Esquivias

Energies 2012, 5(7), 2263-2287; https://doi.org/10.3390/en5072263 - 6 Jul 2012

Cited by 65 | Viewed by 8644

Abstract

This work evaluates the potential for the reduction of energy demand in residential buildings by acting on the exterior envelope, both in newly constructed buildings and in the retrofitting of existing stock. It focuses on analysing social housing buildings in Mediterranean areas and [...] Read more.

This work evaluates the potential for the reduction of energy demand in residential buildings by acting on the exterior envelope, both in newly constructed buildings and in the retrofitting of existing stock. It focuses on analysing social housing buildings in Mediterranean areas and on quantifying the scope of that reduction in the application of different envelope design strategies, with the purpose of prioritizing their application based on their energy efficiency. The analyses and quantifications were made by means of the generation of energy models with the TRNSYS tool for simple or combined solutions, identifying possible potentials for reduction of the energy demand from 20% to 25%, basically by acting on the windows. The case study was a newly built social housing building of a closed block type located in Seville (Spain). Its constructive techniques and the insulation level of its envelope are standardized for current buildings widespread across Mediterranean Europe. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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4048 KiB

Open AccessArticle

The Impact of Roof Pitch and Ceiling Insulation on Cooling Load of Naturally-Ventilated Attics

by Shimin Wang, Zhigang Shen and Linxia Gu

Energies 2012, 5(7), 2178-2196; https://doi.org/10.3390/en5072178 - 4 Jul 2012

Cited by 8 | Viewed by 8162

Abstract

A 2D unsteady computational fluid dynamics (CFD) model is employed to simulate buoyancy-driven turbulent ventilation in attics with different pitch values and ceiling insulation levels under summer conditions. The impacts of roof pitch and ceiling insulation on the cooling load of gable-roof residential [...] Read more.

A 2D unsteady computational fluid dynamics (CFD) model is employed to simulate buoyancy-driven turbulent ventilation in attics with different pitch values and ceiling insulation levels under summer conditions. The impacts of roof pitch and ceiling insulation on the cooling load of gable-roof residential buildings are investigated based on the simulation of turbulent air flow and natural convection heat transfer in attic spaces with roof pitches from 3/12 to 18/12 combined with ceiling insulation levels from R-1.2 to R-40. The modeling results show that the air flows in the attics are steady and exhibit a general streamline pattern that is qualitatively insensitive to the investigated variations of roof pitch and ceiling insulation. Furthermore, it is predicted that the ceiling insulation plays a control role on the attic cooling load and that an increase of roof pitch from 3/12 to 8/12 results in a decrease in the cooling load by around 9% in the investigated cases. The results suggest that the increase of roof pitch alone, without changing other design parameters, has limited impact on attics cooling load and airflow pattern. The research results also suggest both the predicted ventilating mass flow rate and attic cooling load can be satisfactorily correlated by simple relationships in terms of appropriately defined Rayleigh and Nusselt numbers. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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816 KiB

Open AccessArticle

CFD Simulation of a Concrete Cubicle to Analyze the Thermal Effect of Phase Change Materials in Buildings

by Miguel A. Gómez, Miguel A. Álvarez Feijoo, Roberto Comesaña, Pablo Eguía, José L. Míguez and Jacobo Porteiro

Energies 2012, 5(7), 2093-2111; https://doi.org/10.3390/en5072093 - 25 Jun 2012

Cited by 25 | Viewed by 8812

Abstract

In this work, a CFD-based model is proposed to analyse the effect of phase change materials (PCMs) on the thermal behaviour of the walls of a cubicle exposed to the environment and on the resistance of the walls to climate changes. The effect [...] Read more.

In this work, a CFD-based model is proposed to analyse the effect of phase change materials (PCMs) on the thermal behaviour of the walls of a cubicle exposed to the environment and on the resistance of the walls to climate changes. The effect of several days of exposure to the environment was simulated using the proposed method. The results of the simulation are compared with experimental data to contrast the models. The effects of exposure on the same days were simulated for several walls of a cubicle made of a mixture of concrete and PCM. The results show that the PCM stabilizes temperatures within the cubicle and decreases energy consumption of refrigeration systems. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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793 KiB

Open AccessArticle

Study on the Development of an Optimal Heat Supply Control Algorithm for Group Energy Apartment Buildings According to the Variation of Outdoor Air Temperature

by Jae-Ki Byun, Young-Don Choi, Jong-Keun Shin, Myung-Ho Park and Dong-Kurl Kwak

Energies 2012, 5(5), 1686-1704; https://doi.org/10.3390/en5051686 - 24 May 2012

Cited by 5 | Viewed by 7431

Abstract

In the present study, we have developed an optimal heat supply algorithm which minimizes the heat loss through the distribution pipe line in a group energy apartment. Heating load variation of a group energy apartment building according to the outdoor air temperature was [...] Read more.

In the present study, we have developed an optimal heat supply algorithm which minimizes the heat loss through the distribution pipe line in a group energy apartment. Heating load variation of a group energy apartment building according to the outdoor air temperature was predicted by a correlation obtained from calorimetry measurements of all households in the apartment building. Supply water temperature and mass flow rate were simultaneously controlled to minimize the heat loss rate through the distribution pipe line. A group heating apartment building located in Hwaseong city, Korea, which has 1473 households, was selected as the object building to test the present heat supply algorithm. Compared to the original heat supply system, the present system adopting the proposed control algorithm reduced the heat loss rate by 10.4%. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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1579 KiB

Open AccessTechnical Note

A Smart Green Building: An Environmental Health Control Design

by Shang-Yuan Chen and Jui-Ting Huang

Energies 2012, 5(5), 1648-1663; https://doi.org/10.3390/en5051648 - 21 May 2012

Cited by 8 | Viewed by 7356

Abstract

This study proposes the establishment of an environmental health information management platform providing residential users with a comfortable, healthy indoor environment. Taking the S House as an example, the study: (1) assigned environmental health performance indicators, (2) established constraints to maintain environmental conditions, [...] Read more.

This study proposes the establishment of an environmental health information management platform providing residential users with a comfortable, healthy indoor environment. Taking the S House as an example, the study: (1) assigned environmental health performance indicators, (2) established constraints to maintain environmental conditions, and (3) provided optimized management control mechanisms and methods. The environmental health information management platform provides an optimized control and solution pathway ensuring the quality of the indoor health environment and equipment energy conservation. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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