Building Energy Demand Research Articles

Building energy demand of urban blocks in Xi'an, China: Impacts of high-rises and vertical meteorological pattern

High-rise buildings have been promoted in high-density cities. The impact degree of urban high-rises on the building energy demand at the urban block scale is determined by many factors, including the effects of the vertical meteorological pattern (VMP), which have been discussed insufficiently. In this study, the VMP of urban areas in Xi'an, China was observed, and a building energy simulation model that revealed the “urban block form–outdoor climate–building energy” nexus was developed with the URBANopt plugin on the Grasshopper platform. The impacts of the VMP on the building heating and cooling energy demands of different urban blocks were then predicted. In January, the VMP led to building heating load increases of 0.7–1.6 kWh/m2 (16–52%) and 0.0–1.1 kWh/m2 (0–35%) in the residential and mixed-use blocks, respectively. In July, the ranges of the building cooling load changes produced by the effects of the VMP were 0.0–0.1 kWh/m2 (0–1%) and −0.3–0.2 kWh/m2 (−2%) in the residential and mixed-use blocks, respectively. Furthermore, the VMP affected the relationship between the urban block form and the building energy demand. Based on the relationship, we provided form-optimization advice for different functional urban blocks. The urban high-rise mechanisms in high-density cities and their impacts on the building energy demand were discovered in this study. This can help decision-makers to optimize urban planning while promoting urban sustainability.

Performance analysis of the phase-change heat-storage tank based on numerical simulation

Phase-change heat storage system contributes to the smooth operations of building energy supply and demand. In this paper, the numerical model of the heat-storage tank with phase change material blocks is established. The charge and discharge process of the heat-storage tank is analyzed with the numerical model. The performances of the heat-storage tank with and without phase change material blocks are compared by experiment and numerical simulation. The effects of structural parameters of phase change material blocks on the heat storage and release rate are comprehensively discussed, including the number and size of phase change material blocks. The results indicate that under the experimental conditions, the charge capacity and duration of the tank with phase change material blocks are extended by 7.43% and 8.3% respectively under the condition of replacing 6.75% volume of hot water with phase change material. The thermal stratification phenomenon in the heat-storage tank without phase change material blocks is more obvious. For certain volume of the phase change material, the performance analysis of three cases with different amount and size of phase change material blocks is investigated. The results show that the phase change material blocks with number and size of 24 and 0.45 m × 0.1 m × 0.1 m reduces the charge and discharge duration by 2.47% and 3.78% compared with those of 12 and 0.9 m × 0.1 m × 0.1 m.

A Brief Review of the Latest Advancements of Massive Solar Thermal Collectors

Technologies that can contribute to the reduction of greenhouse gases are mandatory, and those based on solar energy are good candidates to achieve this. In this sense, massive solar thermal collectors are suitable technologies for supplying the primary energy demand of buildings. To design these devices, it is necessary to fully understand the physics of the problem before proposing any new optimized solution. This review aims to briefly summarize significant aspects regarding the current state of development of these solar technologies. Attention is paid to works devoted to experimental studies to analyze the behavior of these systems, as well as numerical models to predict the physics of the problem. Furthermore, the future directions and prospects in the field of massive collectors are briefly described. The main novelty of this review is to provide a comprehensive overview that summarizes the works done so far in the field over the past 30 years, which allows the reader to delve deeper into the topic. According to the reviewed works, it can be concluded that these technologies can contribute to the reduction of greenhouse gases while at the same time being excellent examples of the integration of solar energy devices with buildings.

Analysis of the Energy Performance of a Retrofitted Low-Rise Residential Building after an Energy Audit

The main reason for this research is to support the Korean government building retrofitting program initiated to evaluate energy usage trends, propose energy-saving technologies, and focus on reducing the energy demand in residential buildings through energy efficiency improvement. This is achieved by assessing the energy saved after introducing a simple retrofitting measure to an existing residential building. The energy savings in the building were realized after collecting relevant data from the house occupants, analyzing electricity bills, and introducing energy conservation measures (ECMS), leading to an improvement in the energy performance of the building. The building envelope saved 2098 kWh and 6307 kWh of energy via the heating and cooling equipment with an initial incremental cost of USD 500, fuel cost savings of USD 306, and a simple payback of 1.6 years. The analysis takes the occupants 2.6 years to recoup the initial cost of USD 2400 invested with an electricity savings of 2144 kWh. Also, 3.3 tons of CO2 emissions per year were reduced, equivalent to 3.3 people reducing energy use by 20%. Finally, the actual and simulated data are almost the same for the consumption period, with only a slight difference in October and December, given 0.92 as the Pearson Correlation coefficients.

Predicting Building Energy Demand and Retrofit Potentials Using New Climatic Stress Indices and Curves

Building energy requalification in Italy and Europe has been much discussed in recent years due to the high percentage of existing buildings with poor energy performance. In this context, it is useful to obtain a user-friendly and fast tool to predict the thermal energy demand (TED) for space conditioning and the related primary energy consumption (PEC) as a function of climatic stress. In this study, the SLABE methodology (simulation-based large-scale uncertainty/sensitivity analysis of building energy performance) is used to simulate representative Italian buildings, varying parameters such as geometry, envelope and HVAC (heating, ventilating and space conditioning) systems. MATLAB® in combination with EnergyPlus is used to analyze 200 buildings belonging to two structural types (multi-family buildings and apartment blocks) built in 1961–1975. Nine scenarios (as-built scenarios and eight retrofit ones) are investigated in 63 climatic locations. A regression analysis shows that the classical HDDs (heating degree days) approach cannot give an accurate prediction of TED because solar radiation is not accounted for. Thus, new climatic indices are developed alongside solar radiation, including the heating stress index (HSI), the cooling stress index (CSI) and the yearly climatic stress index (YCSI). The purpose of our work is to obtain climatic stress curves for the prediction of TED and PEC. Testing of this novel approach is performed by comparison with another building energy simulation tool, showing a low discrepancy, i.e., the coefficient of variation of the root mean square error is between 12% and 28%, which confirms certain reliability of the approach here proposed.

Carbon neutral projections of public buildings in China under the shared socioeconomic pathways: A tertiary industry perspective

As the energy demand of public building (PB) in China continues to increase, it is meaningful for forecasting the future trend of carbon emissions (CE) of PB. This study analyzes the drivers of CE that affect the operational stage of PB in China by the Generalized Divisia Index Method (GDIM), which considers the effect of the output value and structural transformation of the tertiary industry and makes a scenario prediction of the future carbon-neutral trajectory of CE in PB under the Shared Socioeconomic Pathway (SSP). The results show that from 2010 to 2020, the added value of the tertiary industry (AVTI) is the strongest positive driver of CE from PB (31.912% of the total contribution), which correspond to a cumulative contribution of 212.3 million tons (MtCO2) in 11 years. Regulating the CE per unit of the AVTI is the key indicator in reducing CE from PB, with a cumulative reduction of 130.1 MtCO2. The results of the five scenarios under the SSP framework differ significantly, with SSP1 peaking first in 2026 at 884.5 MtCO2 (876.2–893.9 MtCO2) and SSP5 peaking latest in 2049 at 1372.3 MtCO2 (1362-1389.7 MtCO2). SSP1 yielded the smallest projection in 2060 with 189.8 MtCO2 (185.4–194.3 MtCO2). The findings could help public buildings to implement carbon reduction and provide more scientific and rational decision support for possible paths to achieve carbon neutrality in China.

Supporting climate-neutral cities with urban energy modeling: a review of building retrofit scenarios, focused on decision-making, energy and environmental performance, and cost

Climate deadlines are fast approaching, and city action plans must address slashing carbon emissions using scarce financial resources. Urban energy modeling (UEM) supports building sector transformation by quantifying energy use and emissions in baseline and retrofit scenarios. Additionally, many UEM studies evaluate retrofit costs and financial returns. This review of 26 UEM studies critically analyzes how studies decide to model retrofit measures or impose scenario constraints, and how energy, emissions, and costs are quantified. The results show divergent quantification approaches among the reviewed literature, hindering the usefulness and comparability of the studies for policymakers. The findings also indicate challenges with renewable energy production and heating via heat pumps, including increased peak electrical loads and seasonal mismatches in generation and consumption, which are mitigated by measures reducing building energy demand and energy use, demand-response measures to curtail peaks, and district sources of endogenous energy. The value of the decision-making analysis is to signal pathways toward innovation and stakeholder collaboration for city plans, highlighting approaches using context analysis to generate and share energy in districts, economic criteria to mirror real-world conditions, and stakeholder engagement to meet local priorities. Finally, perspectives for future UEM studies support policymakers guiding the transformation to climate neutrality.

A Facility’s Energy Demand Analysis for Different Building Functions

A more accurate determination of energy demands for buildings is of utmost importance for estimating future energy demands. This article presents two novel ideas that have the potential to contribute to a more precise determination of expected energy demands. The first idea involves accounting for a building’s function more thoroughly, which enables the determination of different energy demands for two or more identical buildings, depending on their respective usage functions. According to a case study, the heating energy demand can be up to twice as high in a commercial facility compared with a residential building. Similarly, the cooling energy requirement can also differ. The second idea concerns determining the heating degree day (HDD) and cooling degree day (CDD) values from the daily minimum and maximum temperatures. This idea may be relevant when few instantaneous values are available for the daily mean temperature. According to the case study, the calculated values from the daily minimum and maximum temperatures follow the HDD and CDD values specified from the daily mean temperature. However, the difference is less than 2% for the heating season and higher for the cooling season. Therefore, further research is required to refine the constants in the cooling equation.

Integrating Urban Heat Island Impact into Building Energy Assessment in a Hot-Arid City

Dense cities usually experience the urban heat island (UHI) effect, resulting in higher ambient temperatures and increased cooling loads. However, the typical lack of combining climatic variables with building passive design parameters in significant evaluations hinders the consideration of the UHI effect during the building design stage. In that regard, a global sensitivity analysis was conducted to assess the significance of climatic variables and building design features in building energy simulations for an office building. Additionally, this study examines the UHI effect on building energy performance in Qatar, a hot-arid climate, using both measurement data and computational modeling. This study collects measurement data across Qatar and conducts computational fluid dynamics (CFD) simulations; the results from both methods serve as inputs in building energy simulation (BES). The results demonstrate that space cooling demand is more sensitive to ambient temperature than other climatic parameters, building thermal properties, etc. The UHI intensity is high during hot and transition seasons and reaches a maximum of 13 °C. BES results show a 10% increase in cooling energy demand for an office building due to the UHI effect on a hot day. The results of this study enable more informed decision-making during the building design process.

A design optimization method for solar-driven thermochemical storage systems based on building performance simulation

The challenge of the temporal mismatch between energy supply and demand in buildings is growing with the increasing share of renewable energy in total energy consumption. Among all the state-of-the-art energy storage solutions, thermochemical heat storage shows a unique potential thanks to its considerable energy density, acceptable cost, and negligible heat loss. For this reason, it becomes a promising alternative to common sensible heat storage solutions for building applications. The integration of such a novel technology in buildings necessitates a method for the assessment of its potential impact and benefit, the comparison to common alternatives, and the optimization of the system design. This work proposes a method based on modeling and simulation of the interaction between the thermochemical heat storage system and the building using a data-driven surrogate model of the storage system in combination with a building performance simulation engine. The data-driven model was developed and validated based on laboratory measurements of a novel closed-loop thermochemical heat storage system, the heat battery (HB). The method was demonstrated in a case study to identify the optimal size of the HB in a solar-driven configuration based on a residential building use case. The results show that the heat battery can digest the thermal energy transferred from the solar thermal collector to reduce the original electricity consumption for heating the detached house (0.7 MWh to 1.0 MWh in considered cases) without any obvious sacrifice in thermal comfort and that the small-scale HB (with a storage volume below 160 l) shows efficient usage of the designed storage capacity.

Life Cycle Assessment of Residential Building Envelopes

The building industry consumes a significant amount of energy due to various factors such as building facade, floor area, energy resource demand, temperature variability, and construction and usage practices. Construction envelopes and the efficiency of building energy demand and equipment contribute to increased energy consumption. Different envelope materials are available, each with different environmental impacts. This research aims to establish a decision-making framework for selecting appropriate building envelopematerials. This paper focuses on conducting a life-cycle assessment (LCA) over a 50-year period for two envelope systems in Indian cities. It considers factors affecting the life cycle assessment of residential buildings, including construction, maintenance, and operational aspects of the building envelope systems. Evaluating building envelope performance is essential for reducing residential energy consumption and maximizing the quality of envelope materials through the application of LCA. The research outlines a comprehensive and systematic approach for selecting building envelopes, providing valuable insights for decision-making regarding envelope materialswith maximumefficiency for residential construction.

Thermal performance analysis of PCM solar wall under variable natural conditions: An experimental study

Low-carbon technologies are critical for mitigating climate change and achieving net-zero emission buildings. Phase change material (PCM) solar wall as a low-carbon technology is a passive heating/cooling system with the potential to cover a significant portion of building energy demand. To better understand the potential of PCM solar walls in different climates, further research into their performance is needed. This research is based on an experimental investigation of the performance of the Solar wall test cell in changing natural conditions for cold and warm seasons. A series of experiments were conducted in both seasons by recording the variation of exterior and interior temperature, as well as solar radiation. Statistical tools were used to analyze the influence of variations in external air temperature and solar radiation on the thermal characteristics of the solar wall in the cell. The results showed a significant difference between external and internal temperature variations for both seasons. Particularly, the wall had the potential during the heating season to maintain the temperature of the test cell above 20 °C for up to 7 h, while in the cooling season, it is observed that the wall keeps room temperature for about 17 h within the comfort range.

Numerical study on the influence of embedded PCM tubes on the energy storage properties of the geothermal energy pile

Geothermal energy pile is a remarkable alternative energy source that can provide heating and cooling energy to meet the energy demands in buildings. This study aims to quantify and expand the knowledge on the thermal storage performance of the geothermal pile system embedded with phase change material containers as compared to the one without, as a goal to expand the wide application of the system. In this study, numerical predictions were conducted on lab-scale energy pile systems, namely Design A (i.e., no PCM) and Design B (i.e., with PCM). The work aimed to investigate and quantify the energy storage properties of geothermal energy piles, and the influence of the incorporation of paraffin wax PCM tubes in the pile, at different flow rates. Incorporating PCM in a geothermal energy pile demonstrated considerable improvement in the amount of energy stored and extracted compared to the one with no PCM. For 735, 1470 and 2100 mL/min, Design B exhibited an increase in the energy stored by 42.21%, 44.71% and 46.23%, respectively compared to Design A. On the other hand, for the flow rate 735, 1470 and 2100 mL/min Design B illustrated an increase in the energy extracted by 45.87%, 53.09% and 59.55%, respectively compared to Design A. The use of PCM in the energy pile has a promising solution to enhance the storage capacity and improve the heat exchange capacity.

Influence of the urban context on solar protection of the vertical envelope and the cooling energy demand of buildings in Cuba

Due to global climate change, new approaches are needed to address energy efficiency in buildings and long-term decarbonization. Solar protection of the vertical envelope of buildings is crucial to achieve this goal by reducing the cooling energy demand. However, the Cuban standard for energy efficiency in buildings (NC220-1, 2009) does not establish solar protection requirements based on the orientation of the exterior walls. The study modelled a generic modular space into a building within Energy Plus. The building was located in three geometric urban scenarios (compact, semi-compact and open) with East, Southeast, South, Southwest, and West orientations. In addition, the exposed vertical envelopes of the space were also studied for the North, Northeast and Northwest orientations in the compact context, as it has the greatest influence on sun protection. The study demonstrated that taking into account the influence of the urban built context and the orientation of the building envelope can reduce the cost of solar protection and cooling demand of buildings. The cost-benefit analysis revealed that the payback period of the sun protection elements can be less than 20 months in 7 of the 8 vertical envelope orientations studied. Furthermore, it does not exceed 15 months in the five least favourable orientations (East, Southeast, South, Southwest, and West). The recommendations provided are pioneers in the field of building energy efficiency in Cuba and should be integrated with architectural and urban guidelines in the short term to achieve an effective impact on the economy and for human well-being.

The kindergarten of Crosara by Sergio Los: reassessing a pioneering thermally efficient building

ABSTRACT Given the environmental and energy crises, European directives are targeting building energy efficiency. Architects must improve the thermal performance of their designs to approach Nearly-Zero Energy Building (NZEB) standards. Energy-efficient experimental buildings from the 1970s are often held up as inspiring examples of energy-conscious architectural design. However, the lack of quantitative data about their thermal performance, measured using current evaluation standards and units, makes their legacy difficult to interpret today. This study aims to verify the relevance of 1970s energy-efficient architecture by quantifying the thermal performance of an exemplary case: the kindergarten designed by Sergio Los in Crosara (Italy). The thermal performance of the building in its original configuration is re-assessed using energy simulation software and discussed relative to past and present standards, including carbon emissions. The results quantify the contributions of different energy-conscious strategies and show that the building’s pioneering performance results primarily from the architect’s bioclimatic design decisions. The study demonstrates how architects reduced building energy demands in the 1970s and explores the impact of their strategies relative to contemporary efficiency priorities.

Green roof cooling and carbon mitigation benefits in a subtropical city

Green roofs are promoted as an effective nature-based urban heat island mitigation strategy. Green roof cooling and energy-saving benefits have been simulated for various climatic zones, but mainly at the building scale. Due to a lack of fact-based information on neighborhood cooling benefits, green roof construction lags and has rarely been incorporated into urban planning actions. This study investigated the thermal benefits and energy savings of green roofs for the central area of the Xianlin Campus of Nanjing University at the neighborhood scale. Three scenarios were simulated for a hot summer day using a validated ENVI-met model: a base case (S0), extensive green roofs (EGRs) (S1), and intensive green roofs (IGRs) (S2). The air temperature cooling benefit from green roofs extended downwards to the pedestrian level. The EGR scenario achieved a maximum 0.29 °C air temperature reduction at the pedestrian level and 0.37 °C at the rooftop level. The IGR scenario achieved a maximum 0.35 °C air temperature reduction at the pedestrian level and 0.45 °C at the rooftop level. EGRs and IGRs reduced energy demands for air-conditioning by 0.39 kWh·m−2·d−1 and 0.56 kWh·m−2·d−1 and CO2 emissions by 31,997 kg·d−1 and 45,967 kg·d−1, respectively. These results confirm that green roofs yield substantial cooling and carbon mitigation benefits. Our study provides essential data to establish green roofs as mainstream cooling technology in subtropical cities. The results also imply that urban planners and policymakers may need to embrace the implementation of green roofs in long-term planning and building design practices to improve urban thermal environments, reduce building energy demand, and curb carbon emissions.

Prospects for creating surfaces with vegetation on buildings in Poland

According to the World Green Building Council, energy demand in buildings will increase double, by 2050. Worldwide, construction and the built environment contribute about 39% of global carbon dioxide (28% from operational emissions, from energy needed to heat, cool and power them, and the remaining 11% from materials and construction) and 50% of the world’s resource consumption. Thus, maximising energy efficiency and improving the environment are the main directions of construction development. Both tasks can be solved using green structures that connect living plants with building structures (green roofs, living facades and living interior walls). The data from the main organisations in the branch has been analysed: United Nations, The World Green Building Council, European Parlament and Council, and also Global Alliance for Buildings and Construction. They state the need for green and blue infrastructure, and sustainable urbanisation, incl. decarbonising of buildings and mitigation of urban heat islands. Greening of buildings is a measure to achieve the requirements. In addition, it improves health and well-being or increases biodiversity. Poland has the corresponding norms to stimulate the greening of buildings. The term “biologically active area” is defined as the area with an area arranged in a way that ensures natural vegetation of plants and rainwater retention; such an area also covers 50% of the surface of terraces and flat roofs with a vegetation layer with vegetation and other surfaces (e.g. green facade), providing natural vegetation of plants, with an area of not less than 10 m2, surface water in this area. Special tax policies give privileges to those who green their building(s). These measures have a good result in spreading green structures, which is proved by the objects represented in the article.

The effectiveness of the Iranian building code in mitigating climate change in Bandar Abbas

Climate change has a varying impact on building energy demand. In Bandar Abbas, a city on the southern coast of Iran, global warming is expected to exacerbate an already harsh climate. Although the Iranian building code has an energy efficiency ranking with specific design requirements, its effectiveness in mitigating climate change is still to be fully understood. Furthermore, Iran's energy mix based on fossil fuels makes filling this gap even more urgent. This study assesses the magnitude of the impact of global warming on a real-case multi-apartment building in this region and evaluates the effectiveness of the different energy efficiency levels designated in the building code in reducing energy consumption under present and future climate conditions. Depending on the projected shared socioeconomic pathways scenarios, the annual electricity consumption may increase by 14 % to 21 % and 21 % to 40 % in 2050 and 2080 timeframes, respectively. When implementing Iranian building code requirements for the envelope's higher levels of energy efficiency, energy consumption reduces substantially, thus contributing to mitigating the impact of global warming. By applying these regulations, energy savings of 5 % to 19 % and HVAC electricity reductions of 9 % to 26 % can be achieved for units on different building floors. In order for Iran to meet the carbon neutrality targets, we recommend making the highest energy efficiency level of the building code mandatory immediately and pushing forward new and more stringent legislation.

A comparative study of machine learning and deep learning methods for energy balance prediction in a hybrid building-renewable energy system

Globally, the construction industry is experiencing an increase in energy demand, which has significant environmental and economic repercussions. To address these issues, it is now possible for buildings, vehicles, and renewable energy sources to collaborate and function as an advanced, integrated, and environmentally favorable system that meets the high energy demands of contemporary buildings. To attain maximum efficiency, however, it is necessary to create reliable energy demand forecasting models. In this research, by introducing the energy model of a neighbourhood with buildings with solar panels and electric vehicles, the final balance of energy production and consumption for each building and the whole neighbourhood as a micro grid is predicted. DesignBuilder is used to model neighbourhood buildings, and K-Nearest neighbor (KNN), Regression Support Vector (SVR), Adaptive Boosting (AdaBoost), and Deep neural networks (DNN) algorithms in machine learning are used to predict the final energy balance. a comparative analysis of the performance of the KNN, SVR, AdaBoost, and DNN algorithms was conducted to determine which algorithm is the most effective in predicting energy balance. Finally, the Root Mean Square Error (RMSE) has been used to validate the prediction models. The results show that the KNN, SVR, AdaBoost, and DNN algorithms had RMSE values of 0.56, 0.92, 0.95, and 0.53, respectively. Among these algorithms, the DNN and KNN algorithms had more accurate results than the other used algorithms and as a result of this research, An accurate forecast of neighbourhood energy balance was made. This study takes a novel approach by developing a model that takes into account an integrated system of houses, solar cells, and electric consumption for each building in a neighborhood, which can help to optimize energy consumption and reduce environmental impact.

Nano-enhanced thermal energy storage coupled to a hybrid renewable system for a high-rise zero emission building

Renewable energy sources suffer from intermittent availability. Adding a latent heat thermal energy storage (TES) is often proposed as an efficient solution to address their stability. In this study, a hybrid renewable energy system consisting of solar photovoltaic panels, evacuated tube collectors, and a ground source heat pump (GSHP) is investigated. The system was coupled with an underground nano-enhanced TES system for improved performance to meet the energy demand of a high-rise residential building in Toronto, Canada. The applied energy storage system in this study consists of nano-enhanced phase change material pipes buried vertically underground to address the temperature stability of the ground. To investigate the effectiveness of this hybrid renewable energy system, a novel co-simulation methodology is adopted. The efficiency of this system is analysed on the component-scale using CFD simulations. The results show that adding nanoparticles increases the thermal storage capacity of the GSHP by 26.4 %. Then the impact of the hybrid renewable energy system with improved storage capacity on the building scale was assessed using TRNSYS. The economic, environmental, and energy consumption impacts of the proposed system was evaluated. Without TES, 296 borehole heat exchangers with a depth of 243 m would be needed to meet the heat and cooling demand; however, considering the modified ground source heat pump, the number of boreholes were reduced to 197 with a depth of 163 m. The results showed a significant impact on the drilling cost reduction, and the life span increase of the geo-exchange system. The coefficient of performance of the final system increases by 27.1 %, while the building energy consumption decreases by 36.7 %.