Special Issue "Modeling, Control, and Optimization of Hybrid Energy Systems in Buildings"

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

Deadline for manuscript submissions: closed (31 October 2019).

Special Issue Editor

Prof. Sumin Kim
E-Mail Website
Guest Editor
Department of Architecture & Architectural Engineering, Yonsei University, Seoul, Korea
Interests: building energy; building environment and materials; eco-friendly materials

Special Issue Information

Dear Colleagues,

The significant increase of energy consumption in buildings is considered a current issue worldwide due to population growth and rapid economic growth. Building energy consumption amounts to 40% of total energy demand, leading to greenhouse gas (GHC) emissions due to the consequent energy demand. Therefore, the development of building energy systems will play a significant role in reducing energy consumption in buildings.

As a innovative way to handle the issues of climate change and the increase of energy consumption in the building sector, Modelling, Control, and Optimization of Hybrid Energy Systems will prove to be an effective solution.

This Special Issue will contribute a practical and comprehensive forum for exchanging novel research ideas or empirical practices that bridge the optimization of energy techniques, sustainable building energy systems, and energy saving in buildings.

Papers that analyze aspects of energy systems in buildings, which are useful for increasing our knowledge of energy systems, on the basis of one or more of the following topics, are welcome in this Special Issue:

  • building energy
  • improvement of energy performance in buildings
  • hybrid energy systems in buildings
  • energy simulation in buildings
  • thermal energy storage system
  • improving thermal comfort technologies
  • optimization of air conditioning system
  • HVAC and other technical systems
  • building environment and materials
  • energy-saving building materials
  • lighting control system
  • computational fluid dynamics

Prof. Sumin Kim
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • building energy
  • energy simulation
  • hybrid energy systems
  • passive
  • active
  • thermal comfort
  • energy-saving building materials

Published Papers (14 papers)

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Research

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Open AccessArticle
Development of Virtual Air Flow Sensor Using In-Situ Damper Performance Curve in VAV Terminal Unit
Energies 2019, 12(22), 4307; https://doi.org/10.3390/en12224307 - 12 Nov 2019
Abstract
In this study, we developed a virtual air flow sensor using an in-situ damper performance curve to secure the stability of control of the variable air volume (VAV) terminal unit, and also established the in-situ measurement procedure. The minimum air flow rate of [...] Read more.
In this study, we developed a virtual air flow sensor using an in-situ damper performance curve to secure the stability of control of the variable air volume (VAV) terminal unit, and also established the in-situ measurement procedure. The minimum air flow rate of the VAV terminal unit was related to the energy consumption, it was important to determine the minimum air flow rate suitable for the situation of each room in terms of energy saving. However, it was difficult to set the minimum air flow rate low setpoint due to the low accuracy of the air flow sensor of the VAV terminal unit. This paper suggested a virtual air flow sensing method using an in-situ damper performance curve in the VAV terminal unit. The input factors of the virtual sensor were developed on the basis of the supply fan speed and damper opening ratio, which could be easily obtained from the existing control system. In addition, the in-situ measurement procedure of the virtual air flow sensor was developed by dividing the procedure into five steps. Finally, reliability of the virtual air flow sensor was evaluated through uncertainty analysis of input variables and relative error analysis, in comparison with the conventional air flow rate measurement method. The developed virtual air flow sensor was found to have an uncertainty of up to 8.8%, and it was also found that the closer to the maximum the values of the input variables, the lower the uncertainty. In addition, verification of relative error with respect to the measured values by the hot-wire anemometer was conducted by varying operation conditions to a total of 12 cases, and as a result, relative error was found to be up to 5.6%. In addition, the results of long-term experiment showed that relative error was within about 9.5%, and thus, the feasibility for field application and control was confirmed. Full article
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Open AccessArticle
Potential Analysis of Hybrid Renewable Energy Systems for Self-Sufficient Residential Use in Germany and the Czech Republic
Energies 2019, 12(21), 4185; https://doi.org/10.3390/en12214185 - 02 Nov 2019
Abstract
Independence from the power grid can be pursued by achieving total self-sufficient electricity supply. Such an energy supply model might be particularly interesting for settlements located in rural areas where enough space is available for energy generation installations. This article evaluates how and [...] Read more.
Independence from the power grid can be pursued by achieving total self-sufficient electricity supply. Such an energy supply model might be particularly interesting for settlements located in rural areas where enough space is available for energy generation installations. This article evaluates how and at what cost electricity demand of residential users across Germany and the Czech Republic could be covered by hybrid renewable energy generation systems consisting of photovoltaics, micro-generation wind turbines and batteries. High-resolution reanalysis data are used to calculate necessary system sizes over a large area by simultaneously accounting for the temporal variability of renewable energy. For every potential location in the research area, the hybrid system requirements for clusters of 50 self-sufficient single-family houses are calculated. The results indicate no general trend regarding the size of the respective technologies, although larger areas where PV-wind power complementarity enables lowering the total system costs and required storage capacities were determined. Assuming that the cluster of households could be constituted and depending on the location, the total installation and operation costs for the proposed systems for a lifetime of 20 years range between EUR 1.8 Million and EUR 5 Million without considering costs of financing. Regions with the lowest costs were identified mainly in the south of Germany. Full article
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Open AccessArticle
Development of Operating Method of Multi-Geothermal Heat Pump Systems Using Variable Water Flow Rate Control and a COP Prediction Model Based on ANN
Energies 2019, 12(20), 3894; https://doi.org/10.3390/en12203894 - 15 Oct 2019
Cited by 1
Abstract
As the global energy trend continues, the importance of energy savings and efficient use is being emphasized, and the installation and operation of geothermal heat pump systems is increasing. In many buildings, where an actual geothermal heat pump system has been installed, problems [...] Read more.
As the global energy trend continues, the importance of energy savings and efficient use is being emphasized, and the installation and operation of geothermal heat pump systems is increasing. In many buildings, where an actual geothermal heat pump system has been installed, problems of efficiency deterioration occur frequently because of the inefficient operation after installation of the heat pump system. The purpose of this study was to develop and verify the operating method for energy saving and performance improvement of multiple geothermal systems. A coefficient of performance (COP) prediction model using an artificial neural network for real-time COP predictions was developed. The operating method of a multi-geothermal heat pump system using a variable water flow rate control method and COP prediction model was developed. The geothermal heat pump system operates sequentially depending on the water flow rate of the circulation pump. The COP prediction model enabled real-time performance prediction during system operation. The circulation water flow rate was reduced by up to 29% compared to the existing operating method. Approximately 23% of the energy was saved. The COP system, including the consumption power of the circulation pump, was improved. Full article
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Open AccessArticle
Development of Thermal Comfort-Based Controller and Potential Reduction of the Cooling Energy Consumption of a Residential Building in Kuwait
Energies 2019, 12(17), 3348; https://doi.org/10.3390/en12173348 - 30 Aug 2019
Abstract
In Kuwait, where the government subsidizes approximately 95% of residential electricity bills, most of the country’s energy consumption is for residential use. In particular, air-conditioning (AC) systems for cooling, which are used throughout the year, are responsible for residential electric energy consumption. This [...] Read more.
In Kuwait, where the government subsidizes approximately 95% of residential electricity bills, most of the country’s energy consumption is for residential use. In particular, air-conditioning (AC) systems for cooling, which are used throughout the year, are responsible for residential electric energy consumption. This study aimed to reduce the amount of energy consumed for cooling purposes by developing a thermal comfort-based controller. Our study commenced by using a simulation model to investigate the possibility of energy reduction when using the predicted mean vote (PMV) for optimal control. The result showed that control optimization would enable the cooling energy consumption to be reduced by 33.5%. The influence of six variables on cooling energy consumption was then analyzed to develop a thermal comfort-based controller. The analysis results showed that the indoor air temperature was the most influential factor, followed by the mean radiant temperature, the metabolic rate, and indoor air velocity. The thermal comfort-based controller-version 1 (TCC-V1) was developed based on the analysis results and experimentally evaluated to determine the extent to which the use of the controller would affect the energy consumed for cooling. The experiments showed that the implementation of TCC-V1 control made it possible to reduce the electric energy consumption by 39.5% on a summer representative day. The results of this study indicate that it is possible to improve indoor thermal comfort while saving energy by using the thermal comfort-based controller in residential buildings in Kuwait. Full article
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Open AccessArticle
Flexibility Potential of Space Heating Demand Response in Buildings for District Heating Systems
Energies 2019, 12(15), 2874; https://doi.org/10.3390/en12152874 - 26 Jul 2019
Abstract
Using an integrated demand-supply optimization model, this work investigates the potential for flexible space heating demand, i.e., demand response (DR), in buildings, as well as its effects on the heating demand and the operation of a district heating (DH) system. The work applies [...] Read more.
Using an integrated demand-supply optimization model, this work investigates the potential for flexible space heating demand, i.e., demand response (DR), in buildings, as well as its effects on the heating demand and the operation of a district heating (DH) system. The work applies a building stock description, including both residential and non-residential buildings, and employs a representation of the current DH system of the city of Gothenburg, Sweden as a case study. The results indicate that space heating DR in buildings can have a significant impact on the cost-optimal heat supply of the city by smoothing variations in the system heat demand. DR implemented via indoor temperature deviations of as little as +1 °C can smoothen the short-term (daily) fluctuations in the system heating demand by up to 18% over a period of 1 year. The smoothening of the demand reduces the cost of heat generation, in that the heat supply and number of full-load hours of base-load heat generation units increase, while the number of starts for the peaking units decreases by more than 80%. DR through temperature deviations of +3 °C confers diminishing returns in terms of its effects on the heat demand, as compared to the DR via +1 °C. Full article
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Open AccessArticle
Residential End-Use Energy Estimation Models in Korean Apartment Units through Multiple Regression Analysis
Energies 2019, 12(12), 2327; https://doi.org/10.3390/en12122327 - 18 Jun 2019
Abstract
The aim of this study was to develop a mathematical regression model for predicting end-use energy consumption in the residential sector. To this end, housing characteristics were collected through a field survey and in-depth interviews with residents of 71 households (15 apartment complexes) [...] Read more.
The aim of this study was to develop a mathematical regression model for predicting end-use energy consumption in the residential sector. To this end, housing characteristics were collected through a field survey and in-depth interviews with residents of 71 households (15 apartment complexes) in Seoul, South Korea, and annual data on end-use energy consumption were collected from measurement systems installed within each apartment unit. Based on the data collected, correlativity between the field-survey data and end-use energy consumption was analyzed, and effective independent variables from the field-survey data were selected. Regression models were developed and validated for estimating six end uses of energy consumption: heating, cooling, domestic hot water (DHW), lighting, electric appliances, and cooking. Regression analysis for ventilation was not applied, and instead a calculation formula was derived, because the energy-consumption proportion was too low. The adj-R2 of the estimation model ranged from 0.406 to 0.703, and the maximum error between measured and estimated values was around ±30%, depending on the end use. Full article
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Open AccessArticle
Climate Classification for the Use of Solar Thermal Systems in East Asia
Energies 2019, 12(12), 2286; https://doi.org/10.3390/en12122286 - 14 Jun 2019
Abstract
To examine the effects of solar heat utilization, it is necessary to classify the solar-use climate in East Asia based on climatic factors that affect load reduction by solar heating systems. In this study, annual load simulations are performed on weather data in [...] Read more.
To examine the effects of solar heat utilization, it is necessary to classify the solar-use climate in East Asia based on climatic factors that affect load reduction by solar heating systems. In this study, annual load simulations are performed on weather data in 842 sites in Japan to analyze the climatic factors that impact the load reduction effect of the solar heating system. The analysis results were based on three climatic factors that strongly affect the heating load of a building: heating degree day (HDD18-18), daily solar global horizontal irradiance, and solar-heat available days. Furthermore, to distinguish the climate for the use of solar heat in East Asia, climate classification was done according to three climatic factors using the weather data of 1176 sites in East Asia. Consequently, the climate of solar thermal utilization in East Asia can be classified into 88 areas. Based on the regional classification for solar heat utilization proposed in this study, it will be possible to examine the effect of load reduction and applicability according to the use of solar heat in each region in the future. Full article
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Open AccessArticle
Influence of Freeze/Thaw Cycles on Mechanical and Thermal Properties of Masonry Wall and Masonry Wall Materials
Energies 2019, 12(8), 1464; https://doi.org/10.3390/en12081464 - 17 Apr 2019
Cited by 2
Abstract
In this study, the influence of freeze/thaw cycles on the mechanical and thermal properties of bricks and mortar as building parts of masonry walls, as well as the influence on the masonry wall itself is investigated. At the material level, the influence of [...] Read more.
In this study, the influence of freeze/thaw cycles on the mechanical and thermal properties of bricks and mortar as building parts of masonry walls, as well as the influence on the masonry wall itself is investigated. At the material level, the influence of freeze and thaw cycles on the mechanical and thermal properties of masonry components (bricks and mortar) was investigated; at the construction level, the influence of freeze and thaw cycles on the mechanical and thermal properties of a masonry wall was studied. To study the influence of freezing on the energy demand characteristics of masonry buildings, in terms of energy conservation and greenhouse gas emission, a case study was investigated on a typical structure of a historical building located in Croatia, that had undergone a process of energy certification. The applied freeze/thaw regime negatively influenced the compressive strength and the thermal properties of bricks and mortar, as well as the mechanical and thermal properties of the wall. Considering the thermal properties of the material before and after its exposure to freeze/thaw cycles, we concluded that the annual energy consumption, the heating costs, and the CO2 emission of a family house could increase up to 3.7% after frost action in the studied case. Full article
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Open AccessArticle
Improvement in Energy Performance of Building Envelope Incorporating Electrochromic Windows (ECWs)
Energies 2019, 12(6), 1181; https://doi.org/10.3390/en12061181 - 26 Mar 2019
Abstract
The present study sets out to review the thermal and optical properties of electrochromic windows (ECWs) through an analysis of the improvement in the energy performance of a building resulting from their application. The performance analysis was based on the change in the [...] Read more.
The present study sets out to review the thermal and optical properties of electrochromic windows (ECWs) through an analysis of the improvement in the energy performance of a building resulting from their application. The performance analysis was based on the change in the room temperature according to the solar transmittance and the orientation of the ECWs, the energy consumptions of the building’s heating/cooling systems, and that of the building’s lighting according to the visible light transmittance (VLT). To achieve this, the Quick Energy Simulation Tool (eQUEST), a building energy interpretation program, was used. The solar heat gain coefficient (SHGC) of the ECWs was found to be significantly reduced. This had the effect of lowering the room temperature in summer, such that the effect on the summer cooling energy consumption was also remarkable. However, with a reduction in the VLT, the lighting energy consumption increased. The net result of the changes in the heating/cooling and lighting energy consumptions was a reduction of about 11,207 kWh/yr (8.89%). The ECWs were found to realize a greater reduction in a building’s energy consumption than was possible with windows glazed with low-E coated glass. Full article
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Open AccessArticle
Technology Roadmap for Eco-Friendly Building Materials Industry
Energies 2019, 12(5), 804; https://doi.org/10.3390/en12050804 - 28 Feb 2019
Abstract
As quality of life has improved, the need for high-performance building materials that meet specific technological requirements has increased. Residential environments have also changed owing to climate change. A technology roadmap could define and systematically reflect a timeline for the development of future [...] Read more.
As quality of life has improved, the need for high-performance building materials that meet specific technological requirements has increased. Residential environments have also changed owing to climate change. A technology roadmap could define and systematically reflect a timeline for the development of future core technologies. The purpose of this research is to build a technology roadmap that could be utilized for the development of technology in the eco-friendly building material industry. This research is composed of multiple analysis processes—patent analysis, Delphi, and analytic hierarchy process analysis—that minimize the uncertainty caused by the lack of information in the eco-friendly construction industry by securing objective future forecast data. Subsequently, the quality function deployment test is implemented to verify the feasibility of the technology roadmap that is constructed. The design of various types of functional, low-carbon building materials could reduce carbon emissions and save energy by ensuring a hazardous-material-free market in the future. This design development roadmap is required to complement this technology roadmap. Full article
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Open AccessArticle
Evaluation of Alternatives for Improving the Thermal Resistance of Window Glazing Edges
Energies 2019, 12(2), 244; https://doi.org/10.3390/en12020244 - 14 Jan 2019
Abstract
To reduce condensation and ensure occupant comfort, the Korean Design Standard for Preventing Condensation in Apartment Buildings was enacted in 2014. However, glazing edges remain vulnerable to condensation. Because this design standard is recent, few window products satisfy the condensation resistance requirement for [...] Read more.
To reduce condensation and ensure occupant comfort, the Korean Design Standard for Preventing Condensation in Apartment Buildings was enacted in 2014. However, glazing edges remain vulnerable to condensation. Because this design standard is recent, few window products satisfy the condensation resistance requirement for glazing edges, especially in the coldest region, and there have been limited investigations on improvement measures. This study evaluates and verifies various treatments for improving the glazing edge thermal resistance of double-glazed four-track horizontal sliding windows to reduce condensation risk and satisfy the design standard. Three-dimensional heat transfer simulations are performed for each alternative to obtain the surface temperature and temperature difference ratio (TDR) for the bottom edge of the glazing. The U-factors of the alternatives satisfying the required TDR for the coldest region are simulated, and the effects of increased local thermal resistance in the glazing edge on the U-factor of the window are analyzed. Mock-up tests are performed on the most economical and best-performing alternatives satisfying the coldest region TDR, and the TDRs and U-factors from the simulations and mock-up tests are compared to verify the performance of the most economical alternative. Insulating spacers, frame extensions, and low-emissivity coatings are effective in various cases. Full article
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Review

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Open AccessReview
Building Energy Retrofit Measures in Hot-Summer–Cold-Winter Climates: A Case Study in Shanghai
Energies 2019, 12(17), 3393; https://doi.org/10.3390/en12173393 - 03 Sep 2019
Abstract
Building retrofit measures provide a significant means of mitigating the effect of climate change on buildings by enhancing building energy performance at a beneficial cost-effectiveness. An insight into the applicable building retrofit measures within a climate zone will guide the optimisation framework to [...] Read more.
Building retrofit measures provide a significant means of mitigating the effect of climate change on buildings by enhancing building energy performance at a beneficial cost-effectiveness. An insight into the applicable building retrofit measures within a climate zone will guide the optimisation framework to attaining sustainability in architecture and the built environment. This article presents a brief overview of recent studies on retrofit measures and its application on a variety of buildings in hot-summer–cold-winter climates, with emphasis on Shanghai. Findings show that the major retrofit measures include improvement in the building envelope, heating, ventilation and cooling (HVAC) and lighting, supported by photovoltaic (PV) systems, accordingly. Furthermore, the study identifies key elements and plausible challenges for the evaluation of building retrofit measures in this region. In this regard, financial barriers and lack of standards and regulatory support are the main challenges identified. These insights provide a systematic approach to guide building researchers, practitioners and decision-makers in the design and development of existing and new retrofit measures for the future of rapidly growing cities with a broad climate variation scope. Full article
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Open AccessReview
Forecasting Energy Use in Buildings Using Artificial Neural Networks: A Review
Energies 2019, 12(17), 3254; https://doi.org/10.3390/en12173254 - 23 Aug 2019
Cited by 1
Abstract
During the past century, energy consumption and associated greenhouse gas emissions have increased drastically due to a wide variety of factors including both technological and population-based. Therefore, increasing our energy efficiency is of great importance in order to achieve overall sustainability. Forecasting the [...] Read more.
During the past century, energy consumption and associated greenhouse gas emissions have increased drastically due to a wide variety of factors including both technological and population-based. Therefore, increasing our energy efficiency is of great importance in order to achieve overall sustainability. Forecasting the building energy consumption is important for a wide variety of applications including planning, management, optimization, and conservation. Data-driven models for energy forecasting have grown significantly within the past few decades due to their increased performance, robustness and ease of deployment. Amongst the many different types of models, artificial neural networks rank among the most popular data-driven approaches applied to date. This paper offers a review of the studies published since the year 2000 which have applied artificial neural networks for forecasting building energy use and demand, with a particular focus on reviewing the applications, data, forecasting models, and performance metrics used in model evaluations. Based on this review, existing research gaps are identified and presented. Finally, future research directions in the area of artificial neural networks for building energy forecasting are highlighted. Full article
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Open AccessReview
Notes on the Economics of Residential Hybrid Energy System
Energies 2019, 12(14), 2639; https://doi.org/10.3390/en12142639 - 10 Jul 2019
Abstract
Despite advances in small-scale hybrid renewable energy technologies, there are limited economic frameworks that model the different decisions made by a residential hybrid system owner. We present a comprehensive review of studies that examine the techno-economic feasibility of small-scale hybrid energy systems, and [...] Read more.
Despite advances in small-scale hybrid renewable energy technologies, there are limited economic frameworks that model the different decisions made by a residential hybrid system owner. We present a comprehensive review of studies that examine the techno-economic feasibility of small-scale hybrid energy systems, and we find that the most common approach is to compare the annualized life-time costs to the expected energy output and choose the system with the lowest cost per output. While practical, this type of benefit–cost analysis misses out on other production and consumption decisions that are simultaneously made when adopting a hybrid energy system. In this paper, we propose a broader and more robust theoretical framework—based on production and utility theory—to illustrate how the production of renewable energy from multiple sources affects energy efficiency, energy services, and energy consumption choices in the residential sector. Finally, we discuss how the model can be applied to guide a hybrid-prosumer’s decision-making in the US residential sector. Examining hybrid renewable energy systems within a solid economic framework makes the study of hybrid energy more accessible to economists, facilitating interdisciplinary collaborations. Full article
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