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Building Renewable Energy and Thermal Energy Storage System 2019

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "G: Energy and Buildings".

Deadline for manuscript submissions: closed (20 October 2019) | Viewed by 32394

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Prof. Dr. Yanping Yuan

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Guest Editor

School of Mechanical Engineering, Southwest Jiaotong University, Chengdu 610031, China
Interests: built environment for underground space; phase change materials; heat and mass transfer; solar thermal and power generation; heat pumps; refrigeration; air conditioning
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Prof. Dr. Xudong Zhao

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Guest Editor

1. Centre for Sustainable Energy Technologies, Energy and Environment Institute, University of Hull, Hull HU6 7RX, UK
2. Center of Intelligent Acoustics and Immersive Communications, Northwestern Polytechnical University, 127 Youyi West Road, Xi’an 710072, China
Interests: solar thermal and power technologies and systems; PV/thermal; heating; cooling; energy efficiency; heat and mass transfer
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Dr. Liangliang Sun

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Guest Editor

School of Mechanical Engineering, Southwest Jiaotong University, Chengdu 610031, China
Interests: solar thermal and power systems

Special Issue Information

Dear Colleagues,

Owing to continuously growing energy demands in buildings, renewable energy applied in buildings and related research have attracted more and more public attention. Currently, buildings consume one third of the total energy supply in developed countries and one quarter in developing countries. Reducing building energy demands and effectively utilizing renewable energy in buildings are considered to be principal routes towards low energy and sustainable buildings. Due to the instability of the renewable energy supply, thermal energy storage technologies are also crucial to the widespread application of renewable energy in buildings.

As one of the most important renewable energies, solar energy technologies have been investigated for many years. Solar thermal (ST) technology, solar photovoltaic (PV) technology and photovoltaic/thermal (PV/T) technology are regarded as the most feasible renewable solutions for building applications. ST technology, which is the most mature technology among all currently available solar energy technologies, has a much higher solar conversion efficiency and shorter payback time. Although, currently, PV installations in buildings are still small-scale, PV technology has already developed into a mature technology, both technically and commercially. With continuous technical advances, reduced costs and legal policies in renewable energies, the applications of PV technology will continue to grow quickly and will eventually become an important electrical energy source. PV/T technology, which can simultaneously generate electricity and heat, takes advantages of both PV and solar thermal technologies. Due to its higher overall solar conversion efficiency and more effective use of space, the market potential of PV/T technology is expected to be higher than individual PV and solar thermal technologies.

Ground-coupled heat pump (GCHP) technology has been increasingly attracting attention as a renewable energy technology of high energy efficiency and its environmentally friendly mechanism for space cooling and heating. The most important component of the GCHP system is the ground heat exchangers (GHEs). Compared to other types of GHEs, vertical GHEs have more benefits, such as the smaller space taken for installation and superior energy efficiency. Heat transfer analysis of vertical GHEs has always been a key issue in designing GCHP systems. In addition, another key issue for GCHP systems is that the heat rejected into the ground is usually not equal to that absorbed from the ground, which will cause heat accumulation or heat attenuation in the ground. One of the cost-effective solutions is to promote GSHP systems in so-called hybrid GSHP systems. The design and applications of hybrid GSHP systems have become a special interest in the research of GCHP technologies.

Thermal energy storage (TES) technologies, including seasonal and short-term storage technologies, are considered to be important in solving the problems of instability in renewable energy supply and the mismatching between building energy demands and a renewable energy supply. Phase change materials (PCMs), which are widely used in various thermal energy storage systems, are particularly attractive materials due to their high energy storage densities and stable phase change temperatures. However, research work is required to improve the thermal properties of PCMs, such as low thermal conductivity and high super-cooling temperature, to increase the overall heat transfer efficiency. Furthermore, the investigation of new PCM materials is very important for the development of effective latent thermal storage. Additionally, good design and control strategies for PCM units are crucially important for promoting the applications of PCMs in thermal storage energy systems.

We invite researchers to contribute original research articles, as well as review articles. Your contributions will promote public understanding of the operational principles of various building-applicable renewable energy technologies and thermal energy storage systems. We are particularly interested in articles presenting novel materials, new method and theories, or innovative aspects in practical applications that can help to enhance the efficiency and reduce the costs of building renewable energy and latent heat thermal storage systems. Potential topics include, but are not limited to:

Solar thermal systems: Domestic hot water, space heating and cooling
Photovoltaic and building integrated photovoltaic (BIPV) technologies
Photovoltaic/Thermal technologies
Heat transfer of GHEs
Design and operation strategy of hybrid GSHP
Heat transfer in PCMs and enhancement techniques
Characterization and development of new PCMs
Thermal energy storage systems in buildings
Thermal management system using PCMs
Integration methods and application of building renewable energy and heat storage system in buildings

Prof. Yanping Yuan
Prof. Xudong Zhao
Dr. Liangliang Sun
Guest Editors

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Keywords

Renewable energy
Ground source heat pump
Solar thermal
Solar power
PV
PV/T
Heat storage
Latent heat
Thermal management
PCMS
Integration
Building

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Published Papers (9 papers)

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Research

16 pages, 3983 KiB

Open AccessArticle

On the Study of a Hybrid Indirect Evaporative Pre-Cooling System for Various Climates

by Xin Cui, Le Sun, Sicong Zhang and Liwen Jin

Energies 2019, 12(23), 4419; https://doi.org/10.3390/en12234419 - 21 Nov 2019

Cited by 14 | Viewed by 3004

Abstract

A hybrid air-conditioning system has been proposed by integrating an indirect evaporative pre-cooling unit. In the proposed system, the room exhaust air is employed in the indirect evaporative cooler (IEC) to pre-condition the ambient intake air. The mathematical formulation has been judiciously established for the pre-cooling IEC. The validation of the numerical model has been conducted by comparing the simulated results with the experimental data in terms of the outlet temperature and the heat flux along the heat exchanger surface. The pre-cooling performance of the IEC is theoretically investigated for the climate in representative cities selected from five different climate zones. The psychrometric illustration of the air conditioning variation has indicated that the ambient air can be pre-cooled and pre-dehumidified through the IEC. The possibility of water vapor condensation depends on the humidity ratio of the ambient intake air. The simulation result demonstrates the capability of the pre-cooling IEC to fulfill part of the cooling load of the ambient intake air resulting in a marked energy saving potential. Full article

(This article belongs to the Special Issue Building Renewable Energy and Thermal Energy Storage System 2019)

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25 pages, 7327 KiB

Open AccessArticle

Climate Compensation and Indoor Temperature Optimal Measuring Point Energy Saving Control in VAV Air-Conditioning System

by Xiuying Yan, Cong Liu, Meili Li, Ating Hou, Kaixing Fan and Qinglong Meng

Energies 2019, 12(22), 4398; https://doi.org/10.3390/en12224398 - 19 Nov 2019

Cited by 5 | Viewed by 3782

Abstract

Temperature measuring point is the key to room environment control. Temperature measuring points and climate changes are directly related to the room control effect. It is of great theoretical and practical significance to study the temperature measuring points and control strategy based on climate compensation. In this study, first, the climate compensation concept in a heating system was introduced into a variable air volume (VAV) air-conditioning system. The heating load was modeled as a function of supply air temperature by analyzing the heat exchange. Based on each control link of subsystems, a climate compensation scheme is proposed to determine the optimal set-point of the supply air temperature. At the same time, a layout of multiple temperature measuring points of an air-conditioned room was studied. Furthermore, the optimal indoor temperature measuring point was determined using an adaptive weighted fusion method. Finally, simulation results show that the proposed method has better control effects on indoor temperature adjustment compared with the traditional method. The optimal supply air temperature in summer and winter was determined according to the proposed climate compensation scheme, and the supply air temperature was controlled using an improved single-neuron adaptive control strategy. Experimental results show that the maximum energy saving can reach up to 35.5% in winter and 6.1% in summer. Full article

(This article belongs to the Special Issue Building Renewable Energy and Thermal Energy Storage System 2019)

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22 pages, 3960 KiB

Open AccessArticle

Cooling Benefits of an Extensive Green Roof and Sensitivity Analysis of Its Parameters in Subtropical Areas

by Yu Zhang, Lei Zhang, Luyao Ma, Qinglin Meng and Peng Ren

Energies 2019, 12(22), 4278; https://doi.org/10.3390/en12224278 - 9 Nov 2019

Cited by 8 | Viewed by 2594

Abstract

The present study aims to further demonstrate the cooling benefits of an extensive green roof (EGR) and fill the gap existing in the literature in terms of a sensitivity analysis of an EGR, especially in subtropical areas. First, onsite measurements were performed. The results indicated that the peak air temperatures in the chamber with the EGR were 4.0 °C and 1.9 °C lower, respectively, compared to those in the chamber with a bare roof on sunny and rainy days. Moreover, the EGR decreased the daily electricity consumption from air conditioning by up to 16.7% on sunny days and 6.7% on cloudy days. Second, the measured values were employed to validate the green roof module (GRM) in EnergyPlus. The results demonstrated that the GRM yielded accurate results in quantifying the cooling benefits of the EGR. Finally, we selected 16 factors of the EGR, each with four levels, to perform the sensitivity analysis. Range and variance analyses revealed that the factors that most significantly impacted the EGR performance were the R-value of roof construction, substrate (soil) thickness, the thermal conductivity of dry substrate, the leaf area index, leaf emissivity, and the solar absorptance of the substrate. These factors contributed 90.8% to the performance index. Full article

(This article belongs to the Special Issue Building Renewable Energy and Thermal Energy Storage System 2019)

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16 pages, 2426 KiB

Open AccessArticle

Energy Performance of an Encapsulated Phase Change Material PV/T System

by Xiaojiao Yang, Jinzhi Zhou and Yanping Yuan

Energies 2019, 12(20), 3929; https://doi.org/10.3390/en12203929 - 16 Oct 2019

Cited by 11 | Viewed by 2294

Abstract

This study aimed to investigate the performance of a novel encapsulated phase change material (PCM) photovoltaic/thermal (PV/T) system. A PCM, which has a high latent heat capacity, can absorb energy from a PV cell and reduce the operating temperature, improving both the electrical and thermal efficiencies of the panel. In this study, a computer model based on a PCM PV/T panel is developed, and its accuracy is verified using experimental data. The effect of the phase change temperature on the performance of the panel was analyzed by numerical simulation. When the phase change temperature was 30.1 °C, the system exhibited a maximum electrical efficiency of 8.2% and a thermal efficiency of 71.8%. When the phase change temperature was 20.24 °C, the system had a maximum exergy efficiency of 33.7%. In general, the temperature of the PCM integrated into the PV/T system should not be too high. Full article

(This article belongs to the Special Issue Building Renewable Energy and Thermal Energy Storage System 2019)

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13 pages, 2807 KiB

Open AccessArticle

Optimizing Water Droplet Diameter of Spray Cooling for Dairy Cow in Summer Based on Enthalpy Difference Theory

by Tao Ding, Baoxi Sun, Zhengxiang Shi and Baoming Li

Energies 2019, 12(19), 3637; https://doi.org/10.3390/en12193637 - 24 Sep 2019

Cited by 5 | Viewed by 2306

Abstract

Spray cooling is widely used in relieving heat stress in dairy cows during summer, in which the cooling effect is highly correlated to the diameter of water droplet. To optimize the average diameter of spraying droplet (ADSD) in the process of heat transfer, a theoretical analysis was performed based on the enthalpy difference theory in this study. A platform was built to simulate the processes of spray cooling and its heat stress alleviation to dairy cows in field, and a field experiment was applied to verify the diameter of water droplets suitable for spray cooling. Heat exchange was calculated for eighteen different ADSD in three different environment conditions in the laboratory. The spraying droplets with eighteen diameters were formed by using six different nozzles under the combinations of three pressures and two wind speeds conditions, which were controlled by heaters. The relationship between the ADSD and heat exchange was established with the purpose to determine the appropriate diameter for practical production. In the field test, body temperature, rectal temperature, and respiratory rate of dairy cows were monitored, and the heat exchange was analyzed to verify the optimal diameter spraying cooling in summer. Results showed that the heat exchange generally increased as ADSD increased, and maximum heat exchanges were reached when the ADSD was averaged at 0.914 mm and 0.995 mm, under which the models of the corresponding nozzles were 9080 and 9010, respectively. After that, the heat exchange decreased as the ADSD continued to increase. Field experiment indicated that the best cooling effect could be achieved with the ADSD of 0.947 mm, and the water consumption for spray cooling was reduced by 22.8% under the scenario. Full article

(This article belongs to the Special Issue Building Renewable Energy and Thermal Energy Storage System 2019)

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9 pages, 1917 KiB

Open AccessArticle

Microencapsulation of Paraffin with Poly (Urea Methacrylate) Shell for Solar Water Heater

by Weiguang Su, Yilin Li, Tongyu Zhou, Jo Darkwa, Georgios Kokogiannakis and Zhao Li

Energies 2019, 12(18), 3406; https://doi.org/10.3390/en12183406 - 4 Sep 2019

Cited by 15 | Viewed by 2880

Abstract

Previous research has demonstred that microencapsulated phase change materials (MEPCMs) could significantly increase the energy storage density of solar thermal energy storage (TES) systems. Compared with traditional phase change materials (PCMs), MEPCMs have many advantages since they can limit their exposure to the surrounding environment, enlarge the heat transfer area, and maintain the volume as the phase change occurs. In this study, a new MEPCM for solar TES systems is developed by encapsulation of paraffin wax with poly (urea formaldehyde) (PUF). The experimental results revealed that agglomeration of MEPCM particles occurred during the encapsulation process which affected the uniformity of the particle size distribution profile when sodium dodecyl sulfate was used as an emulsifier. The differential scanning calorimetric (DSC) analysis results showed that the melting temperatures were slightly increased by 0.14–0.72 °C after encapsulation. A thermogravimetric (TG) test showed that the sample weight decreased while the weight loss starting temperature was slightly increased after encapsulation. Overall, the sample UF-2, fabricated with the binary emulsifiers of Brij 35 and Brij 30 and 5% nucleating agent, resulted in good particle dispersion and shell integrity, higher core material content and encapsulation efficiency, as well as improved thermal stability. Full article

(This article belongs to the Special Issue Building Renewable Energy and Thermal Energy Storage System 2019)

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17 pages, 8136 KiB

Open AccessArticle

Cooling and Energy-Saving Performance of Different Green Wall Design: A Simulation Study of a Block

by Jiayu Li, Bohong Zheng, Wenquan Shen, Yanfen Xiang, Xiao Chen and Zhiyong Qi

Energies 2019, 12(15), 2912; https://doi.org/10.3390/en12152912 - 29 Jul 2019

Cited by 44 | Viewed by 9448

Abstract

To mitigate the urban heat island (UHI) and release the low carbon potential of green walls, we analyzed the cooling and energy-saving performance of different green wall designs. Envi-met was applied as the main simulation tool, and a pedestrian street named Yuhou Street was selected as the study object. Four designs of walls were summarized and simulated, demonstrating the living wall system (LWS). Super soil had superiority in cooling and energy saving. Outdoor air temperature, indoor air temperature, outside wall surface temperature, and inside wall surface temperature were analyzed. Apart from the outdoor air temperature, the other three temperatures were all significantly affected by the design of green walls. Finally, energy savings in building cavities were determined. The indoor energy saving ratio of the LWS based on super soil reached 19.92%, followed by the LWS based on boxes at 15.37%, and green facades wall at 6.29%. The indoor cooling powers on this typical day showed that the cooling power of the LWS based on super soil was 8267.32 W, followed by the LWS based on boxes at 6381.57 W, and green facades wall at 2610.08 W. The results revealed the difference in cooling and energy-saving performance of different green walls in this typical hot summer area. Full article

(This article belongs to the Special Issue Building Renewable Energy and Thermal Energy Storage System 2019)

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18 pages, 6312 KiB

Open AccessArticle

Energy-Efficient Improvement Approaches through Numerical Simulation and Field Measurement for a Data Center

by Fujen Wang, Yishun Huang and BowoYuli Prasetyo

Energies 2019, 12(14), 2757; https://doi.org/10.3390/en12142757 - 18 Jul 2019

Cited by 9 | Viewed by 2691

Abstract

The power density of electronic equipment increased dramatically recently. Data center and data processing and telecommunication facilities are facing the exceptionally high sensible heat loads which result in a large amount of energy consumption. In this study, a numerical simulation using computational fluid dynamics (CFD) was conducted to investigate the influence of alternative approaches to avoid bypassing and recirculation for air distribution in a full-scale data center. Field measurements were extensively conducted to validate the simulation results. Various performance indexes were adopted to enhance the evaluation of the thermal performance of the data center. The simulation results revealed that the practice with hot aisle enclosure and the installation of blocking panels for the unoccupied racks can provide satisfactory airflow distribution and thermal management under low load conditions. The return temperature index (RTI) can be improved by 3% through CFD simulation through installation of the blank panels, which reveals the reduction of recirculation airflow. The return heat index (RHI) increases by 8%, which presents a reduction of bypass airflow. A practical experiment using physical air curtains was conducted to enclose the hot aisle in the data center, which also reveals an 8% improvement for bypass airflow. Higher cooling performance can be achieved via reduction of recirculation and bypass airflow in the data center. Through the simulation of different improvement approaches in the data center, the optimum practice for cooling airflow arrangement can be identified accordingly. Full article

(This article belongs to the Special Issue Building Renewable Energy and Thermal Energy Storage System 2019)

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16 pages, 8672 KiB

Open AccessArticle

Experimental Investigation on Performance Comparison of Solar Water Heating-Phase Change Material System and Solar Water Heating System

by Liangliang Sun, Nan Xiang, Yanping Yuan and Xiaoling Cao

Energies 2019, 12(12), 2347; https://doi.org/10.3390/en12122347 - 19 Jun 2019

Cited by 7 | Viewed by 2756

Abstract

Phase change material can be used as heat transfer fluid in the solar water heating system, which is the latest way to improve thermal efficiency. In this paper, graphene composite paraffin emulsion is used as heat transfer fluid in a solar water heating-phase change material (SWH-PCM) system. By comparing with the traditional solar water heating (SWH) system, the thermal performance characteristics of SWH-PCM system have been investigated experimentally. The SWH-PCM system has higher heat storage than the SWH system. The heat storage of SWH-PCM system and SWH system all increase with the increase of solar irradiance, while the thermal efficiency has the opposite trend. The flow rate has a greater influence on the thermal efficiency of SWH-PCM system than that of the SWH system. With the flow rate of 200 L/h, the thermal efficiency of SWH-PCM system is 14.21% higher than that of the SWH system. In summary, the SWH-PCM system is a promising solar water heating system with high heat storage and thermal efficiency. Full article

(This article belongs to the Special Issue Building Renewable Energy and Thermal Energy Storage System 2019)

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