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19 pages, 6828 KiB

Open AccessArticle

Experimental Study on Heat Transfer Coefficients in an Office Room with a Radiant Ceiling During Low Heating Loads

by Piotr Michalak

Energies 2025, 18(7), 1591; https://doi.org/10.3390/en18071591 - 22 Mar 2025

Viewed by 408

Abstract

Estimation of the heating or cooling capacity of radiant systems requires selecting appropriate internal heat transfer coefficients by convection (CHTCs) and radiation (RHTCs). Due to practical reasons, their measurement during the normal use of buildings is very troublesome. This study attempts to present [...] Read more.

Estimation of the heating or cooling capacity of radiant systems requires selecting appropriate internal heat transfer coefficients by convection (CHTCs) and radiation (RHTCs). Due to practical reasons, their measurement during the normal use of buildings is very troublesome. This study attempts to present the results of measurements of CHTCs and RHTCs taken in an office room located in a passive building with a heated concrete ceiling. Special attention was paid to the proper choice of reference temperatures. For better accuracy, view factors for radiant heat exchange were calculated using Matlab. Average values of CHTCs and RHTCs calculated from measurements amounted to 0.80 W/m²K and 5.66 W/m²K. RHTCs showed a significant correlation against the ceiling temperature, with the coefficient of determination being R² = 0.96. Finally, the total heat transfer coefficient of 6.47 W/m²K was obtained. These values are comparable with other studies and standards and confirm that measurements were performed correctly. Full article

(This article belongs to the Special Issue Energy and Buildings: Thermal Storage, Emissions, Transports, Control and Their Effects)

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23 pages, 3618 KiB

Open AccessArticle

An End-to-End Relearning Framework for Building Energy Optimization

by Avisek Naug, Marcos Quinones-Grueiro and Gautam Biswas

Energies 2025, 18(6), 1408; https://doi.org/10.3390/en18061408 - 12 Mar 2025

Viewed by 378

Abstract

Building HVAC systems face significant challenges in energy optimization due to changing building characteristics and the need to balance multiple efficiency objectives. Current approaches are limited: physics-based models are expensive and inflexible, while data-driven methods require extensive data collection and ongoing maintenance. This [...] Read more.

Building HVAC systems face significant challenges in energy optimization due to changing building characteristics and the need to balance multiple efficiency objectives. Current approaches are limited: physics-based models are expensive and inflexible, while data-driven methods require extensive data collection and ongoing maintenance. This paper introduces a systematic relearning framework for HVAC supervisory control that improves adaptability while reducing operational costs. Our approach features a Reinforcement Learning controller with self-monitoring and adaptation capabilities that responds effectively to changes in building operations and environmental conditions. We simplify the complex hyperparameter optimization process through a structured decomposition method and implement a relearning strategy to handle operational changes over time. We demonstrate our framework’s effectiveness through comprehensive testing on a building testbed, comparing performance against established control methods. Full article

(This article belongs to the Special Issue Energy and Buildings: Thermal Storage, Emissions, Transports, Control and Their Effects)

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22 pages, 5792 KiB

Open AccessArticle

Advanced Fuel Based on Semi-Coke and Cedarwood: Kinetic Characteristics and Synergetic Effects

by Andrey Zhuikov, Lily Irtyugo, Alexander Samoilo, Yana Zhuikova, Irina Grishina, Tatyana Pyanykh and Stanislav Chicherin

Energies 2024, 17(19), 4963; https://doi.org/10.3390/en17194963 - 4 Oct 2024

Viewed by 1091

Abstract

This paper presents the results of analytical studies of the combustion process of semi-coke, cedar sawdust, and their mixtures using the TGA method at three different heating rates with the determination of the main characteristics of heating: the presence of synergetic interaction between [...] Read more.

This paper presents the results of analytical studies of the combustion process of semi-coke, cedar sawdust, and their mixtures using the TGA method at three different heating rates with the determination of the main characteristics of heating: the presence of synergetic interaction between the components of the mixture affecting the maximum rate of combustion and kinetic parameters. Calculations of activation energy and pre-exponential multiplier of the Arrhenius equation by the Friedman and Ozawa–Flynn–Wall priori methods for initial combustibles and their mixtures have been carried out. Semi-coke was obtained by thermal treatment of brown coal at 700–900 °C to remove volatile substances, which makes it more environmentally friendly than the original coal. Semi-coke has a higher heat of combustion than biomass, and biomass has a higher reactivity than semi-coke. The combustion process of biomass occurs in a lower temperature range, and adding biomass to semi-coke shifts the combustion process to a lower temperature range than such for biomass. Adding at least 50% of biomass to semi-coke increases the combustion index by at least 1.1 times. Regardless of the heating rate of mixtures, synergetic interaction between the mixture’s components increases the maximum combustion rate of coke residue by 20%. Full article

(This article belongs to the Special Issue Energy and Buildings: Thermal Storage, Emissions, Transports, Control and Their Effects)

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35 pages, 17147 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Utilizing Wastewater Tunnels as Thermal Reservoirs for Heat Pumps in Smart Cities

by Fredrik Skaug Fadnes and Mohsen Assadi

Energies 2024, 17(19), 4832; https://doi.org/10.3390/en17194832 - 26 Sep 2024

Cited by 2 | Viewed by 1097

Abstract

The performance of heat pump systems for heating and cooling heavily relies on the thermal conditions of their reservoirs. This study introduces a novel thermal reservoir, detailing a 2017 project where the Municipality of Stavanger installed a heat exchanger system on the wall [...] Read more.

The performance of heat pump systems for heating and cooling heavily relies on the thermal conditions of their reservoirs. This study introduces a novel thermal reservoir, detailing a 2017 project where the Municipality of Stavanger installed a heat exchanger system on the wall of a main wastewater tunnel beneath the city center. It provides a comprehensive account of the system’s design, installation, and performance, and presents an Artificial Neural Network (ANN) model that predicts heat pump capacity, electricity consumption, and outlet temperature across seasonal variations in wastewater temperatures. By integrating domain knowledge with the ANN, this study demonstrates the model’s capability to detect anomalies in heat pump operations effectively. The network also confirms the consistent performance of the heat exchangers from 2020 to 2024, indicating minimal fouling impacts. This study establishes wastewater heat exchangers as a safe, effective, and virtually maintenance-free solution for heat extraction and rejection. Full article

(This article belongs to the Special Issue Energy and Buildings: Thermal Storage, Emissions, Transports, Control and Their Effects)

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14 pages, 280 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Energy Awareness, Energy Use, and Energy-Saving Opportunities in the Caribbean: The Island Curaçao as a Case Study

by Richenel R. Bulbaai and Johannes I. M. Halman

Energies 2024, 17(19), 4829; https://doi.org/10.3390/en17194829 - 26 Sep 2024

Cited by 1 | Viewed by 1292

Abstract

Household energy consumption represents a significant share of global energy usage, highlighting the importance of understanding the factors that influence energy use and identifying potential strategies for conservation. The Caribbean region faces unique challenges in energy sustainability, driven by its heavy dependence on [...] Read more.

Household energy consumption represents a significant share of global energy usage, highlighting the importance of understanding the factors that influence energy use and identifying potential strategies for conservation. The Caribbean region faces unique challenges in energy sustainability, driven by its heavy dependence on fossil fuels and rising energy demand. The primary aim of this study is to evaluate the current levels of energy awareness and energy consumption among households on the tropical Caribbean island of Curaçao and to determine practical energy-saving opportunities that can significantly reduce both energy consumption and costs. This paper is one of the first to evaluate energy awareness, energy use, and energy-saving opportunities among households in the Caribbean. The study included a literature review of key theories, concepts, and energy-saving strategies, along with a telephone survey of 382 households in Curaçao to examine household energy use, the factors shaping energy behavior, and the connections between energy consumption, behavior, and household income. The main findings of this study reveal that energy-efficient appliances are predominantly used in high-income households, with much lower adoption rates in middle- and low-income households. Cost savings, rather than environmental concerns, emerge as the primary motivation behind energy-saving behavior. Notably, the study highlights that most households in Curaçao are largely unaware of the full range of energy-efficient options available to them for reducing energy consumption. Based on the field study results, several recommendations are offered to enhance energy awareness, expand energy-saving opportunities, and ultimately reduce energy usage. Full article

(This article belongs to the Special Issue Energy and Buildings: Thermal Storage, Emissions, Transports, Control and Their Effects)

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15 pages, 2983 KiB

Open AccessFeature PaperArticle

Importance of Window Installation in Residential Building Envelopes Having Continuous External Insulation in Order to Realize Energy Efficiency

by Bipin Shah, Mahabir Bhandari and Mengjia Tang

Energies 2024, 17(17), 4273; https://doi.org/10.3390/en17174273 - 27 Aug 2024

Viewed by 1358

Abstract

Residential buildings are one of the prime candidates in the United States for reducing energy consumption. Continuous exterior insulation (CEI) is being used increasingly often in residential buildings to improve energy efficiency. Windows constitute 15–40% of a building envelope and are the weakest [...] Read more.

Residential buildings are one of the prime candidates in the United States for reducing energy consumption. Continuous exterior insulation (CEI) is being used increasingly often in residential buildings to improve energy efficiency. Windows constitute 15–40% of a building envelope and are the weakest component in energy performance. The installation of windows in walls with CEI has not been well evaluated. We identified four cases of installing windows in walls with CEI of 25–76 mm (1–3 in.) thickness and analyzed the energy loss between the window and wall interface (flanking loss), structural issues, air leakage, and moisture penetration. Thermal analysis showed that the insulation value (RSI) of the 305 mm (12 in.) perimeter wall surrounding a window decreased by 7.6–34.5% in the four cases when compared with the RSI of the wall without the window. A window installation method is proposed to address the issues likely to occur with installation methods currently being used in the field. An out-of-the-box installation system was also designed to achieve a better thermal performance, cost effectiveness, and structural performance in high-performance residential buildings. Full article

(This article belongs to the Special Issue Energy and Buildings: Thermal Storage, Emissions, Transports, Control and Their Effects)

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Review

Jump to: Research, Other

27 pages, 15839 KiB

Open AccessReview

A Systematic Review of Sensitivity Analysis in Building Energy Modeling: Key Factors Influencing Building Thermal Energy Performance

by Rajendra Roka, António Figueiredo, Ana Vieira and Claudino Cardoso

Energies 2025, 18(9), 2375; https://doi.org/10.3390/en18092375 - 6 May 2025

Viewed by 221

Abstract

Improving building thermal energy performance is essential to reducing energy consumption, minimizing carbon emissions, and enhancing occupants’ thermal comfort. For this purpose, there is an increasing research interest in this field of building energy performance. This review aims to present a precise and [...] Read more.

Improving building thermal energy performance is essential to reducing energy consumption, minimizing carbon emissions, and enhancing occupants’ thermal comfort. For this purpose, there is an increasing research interest in this field of building energy performance. This review aims to present a precise and systematic overview of the sensitivity analysis in optimizing the thermal energy performance of buildings. The investigation covers various aspects, including sensitivity analysis techniques, key measures and variables, objectives and criteria, software tools, optimization methods, climate zones, building typology, and climate change effects. The findings reveal that sensitivity analysis is a powerful technique for optimizing energy performance and identifying adaptive strategies such as dynamic shading, reflective coatings, and efficient HVAC set points to address climate change. Most of the study also highlights that the temperature set point is the key influential parameter in both heating-dominant and cooling-dominant climate zones. This review offers critical insights on advancing sustainable building design, informing policy, and guiding future research in energy-efficient building solutions. Full article

(This article belongs to the Special Issue Energy and Buildings: Thermal Storage, Emissions, Transports, Control and Their Effects)

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Other

Jump to: Research, Review

19 pages, 2485 KiB

Open AccessBrief Report

Conversion to Fourth-Generation District Heating (4GDH): Heat Accumulation Within Building Envelopes

by Stanislav Chicherin

Energies 2025, 18(9), 2307; https://doi.org/10.3390/en18092307 - 30 Apr 2025

Viewed by 115

Abstract

This study investigates improving district heating (DH) systems by analyzing the effects of low-temperature operation on network efficiency, heat losses, and indoor temperature stability. A mathematical model is developed to simulate building heat performance under different supply temperatures, substation connection types, and envelope [...] Read more.

This study investigates improving district heating (DH) systems by analyzing the effects of low-temperature operation on network efficiency, heat losses, and indoor temperature stability. A mathematical model is developed to simulate building heat performance under different supply temperatures, substation connection types, and envelope materials. The methodology involves detailed hourly heat load simulations and optimization techniques to assess the impact of temperature flexibility and heat accumulation within buildings. The results reveal that a 10 °C reduction in supply temperature leads to a heat loss decrease of up to 20%, significantly improving system efficiency. Moreover, buildings with higher thermal inertia and indirect substation connections exhibit better resilience to short-term temperature fluctuations, ensuring more stable indoor conditions. The analysis also demonstrates that optimizing temperature control can reduce operational costs by 19%, primarily by minimizing excessive heat supply and utilizing stored thermal energy effectively. Despite slight temperature fluctuations in extreme conditions, the system maintains indoor comfort levels within acceptable limits. This study concludes that transitioning to a lower-temperature DH system is feasible without compromising reliability, provided heat accumulation effects and supply flexibility are carefully managed. These findings offer a replicable approach for improving DH efficiency in networks with diverse building configurations. Full article

(This article belongs to the Special Issue Energy and Buildings: Thermal Storage, Emissions, Transports, Control and Their Effects)

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