Energies

Research

16 pages, 4261 KiB

Open AccessArticle

Comparison between Direct and Indirect Heat Flux Measurement Techniques: Preliminary Laboratory Tests

by Luca Evangelisti, Leone Barbaro, Claudia Guattari, Edoardo De Cristo, Roberto De Lieto Vollaro and Francesco Asdrubali

Energies 2024, 17(12), 2961; https://doi.org/10.3390/en17122961 - 16 Jun 2024

Cited by 1 | Viewed by 1007

Abstract

Direct and indirect approaches can be employed for estimating the heat flow through components in different application fields. In the building sector, the thermometric method is often applied by professionals for thermal transmittance evaluations. However, miscalculations can derive from inaccurate total heat transfer [...] Read more.

Direct and indirect approaches can be employed for estimating the heat flow through components in different application fields. In the building sector, the thermometric method is often applied by professionals for thermal transmittance evaluations. However, miscalculations can derive from inaccurate total heat transfer coefficients, and a consensus regarding the appropriate value to employ remains to be determined. Here, an apparatus was realized for laboratory tests and heat flux measurements were performed following direct and indirect approaches. Data acquired through a common heat flow sensor were compared with those computed through a post-processing based on radiative and convective estimations. The results were affected by the specific correlation adopted for computing the convective coefficients, with the percentage differences ranging from −9.8% to −0.4%. New measurement systems could be designed for automatically computing heat fluxes through indirect approaches, thus providing alternative solutions in the panorama of non-destructive tests for building energy diagnosis. Full article

(This article belongs to the Special Issue Optimization and Innovation of Energy Efficient Buildings and Smart Cities)

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24 pages, 7037 KiB

Open AccessFeature PaperArticle

Analysis of the Hybrid Power-Heating System in a Single-Family Building, along with Ecological Aspects of the Operation

by Grzegorz Woroniak, Joanna Piotrowska-Woroniak, Anna Woroniak, Edyta Owczarek and Krystyna Giza

Energies 2024, 17(11), 2601; https://doi.org/10.3390/en17112601 - 28 May 2024

Viewed by 1324

Abstract

This study evaluates a hybrid heating system in a single-family building in northeastern Poland, which has a temperate continental climate. The analysis covers two heating seasons in 2021/2022 and 2022/2023. The hybrid heating system includes an air heat pump HPA–08 CS Plus with [...] Read more.

This study evaluates a hybrid heating system in a single-family building in northeastern Poland, which has a temperate continental climate. The analysis covers two heating seasons in 2021/2022 and 2022/2023. The hybrid heating system includes an air heat pump HPA–08 CS Plus with a heating power of 8.2 kW (AHP), a condensing gas boiler VC146/5–5 with a power of 14 kW (GB–Condens.), and a solid fuel boiler with a power of 11 kW for central heating. Additionally, hot water is heated by a Basic 270 (DHW’s AHP) air–water heat pump with a power of 2 kW, utilizing a tank with a capacity of 270 dm³ equipped with two heating coils. The building’s average electricity consumption is around 5400 kWh/year. A 4.96 kWp photovoltaic installation is installed on the building’s roof at a 40° angle towards the south to supplement the hybrid system. The study aims to assess whether the PV installation can adequately cover the energy needs of the hybrid heat source for heating and hot water. Furthermore, the study calculates the emission of pollutants (CO₂, SO_x, NO_x, CO, and PM10) into the atmosphere. The total annual electricity production from PV installations was 5444.9 kWh in 2021/2022 and 5684.8 kWh in 2022/2023. The excess electricity was stored in the PGE power grid as per the Prosumer settlement rules. The installed PV installation is sufficient to power the following devices annually: AHP, DHW’s AHP, and GB–Condens. However, the daily electricity production from the PV installation is not enough to cover the energy needs of the heat pump for heating during the cold months in Poland (I–III, XI–XII). It can meet the power needs of a PC all year round and can also be stored during the summer months, for example, in energy warehouses or by directly storing it in the PGE power grid. The use of the PV installation resulted in an average reduction in pollutant emissions into the atmosphere: CO₂—94.1%, SO_x—91.8%, NO_x—95.6%, CO—9.7%, and PM10—32.1%. Full article

(This article belongs to the Special Issue Optimization and Innovation of Energy Efficient Buildings and Smart Cities)

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21 pages, 6153 KiB

Open AccessArticle

Investigating Advanced Building Envelopes for Energy Efficiency in Prefab Temporary Post-Disaster Housing

by Lorenzo Rapone, Afaq A. Butt, Roel C. G. M. Loonen, Giacomo Salvadori and Francesco Leccese

Energies 2024, 17(9), 2008; https://doi.org/10.3390/en17092008 - 24 Apr 2024

Viewed by 906

Abstract

Prefabricated temporary buildings are a promising solution for post-disaster scenarios for their modularity, sustainability and transportation advantages. However, their low thermal mass building envelope shows a fast response to heat flux excitations. This leads to the risk of not meeting the occupant comfort [...] Read more.

Prefabricated temporary buildings are a promising solution for post-disaster scenarios for their modularity, sustainability and transportation advantages. However, their low thermal mass building envelope shows a fast response to heat flux excitations. This leads to the risk of not meeting the occupant comfort and HVAC energy-saving requirements. The literature shows different measures implementable in opaque surfaces, like vacuum insulation panels (VIPs), phase change materials (PCMs) and switchable coatings, and in transparent surfaces (switchable glazing) to mitigate thermal issues, like overheating, while preserving the limited available internal space. This paper investigates the energy and overheating performance of the mentioned interventions by using building performance simulation tools to assess their effectiveness. The optimization also looks at the transportation flexibility of each intervention to better support the decision maker for manufacturing innovative temporary units. The most energy-efficient measures turn to be VIPs as a better energy solution for winter and PCMs as a better thermal comfort solution for summer. Full article

(This article belongs to the Special Issue Optimization and Innovation of Energy Efficient Buildings and Smart Cities)

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21 pages, 7857 KiB

Open AccessArticle

Study on Thermal Performance of Electric Heating System with Salt Hydrate-PCM Storage

by Li Huang, Udo Piontek, Lulu Zhuang, Rongyue Zheng and Deqiu Zou

Energies 2023, 16(20), 7108; https://doi.org/10.3390/en16207108 - 16 Oct 2023

Viewed by 1195

Abstract

An electric radiator combined with salt hydrate-phase change material (PCM) storage was developed to replace the existing scattered coal burning systems for clean heating applications. It was designed to have an average heat output of 400 W and a thermal storage efficiency of [...] Read more.

An electric radiator combined with salt hydrate-phase change material (PCM) storage was developed to replace the existing scattered coal burning systems for clean heating applications. It was designed to have an average heat output of 400 W and a thermal storage efficiency of 65.6% for reducing the electricity peak load. The thermal performance was investigated experimentally and numerically by using various radiator configurations and electric heating powers, as well as three PCMs with a melting point of 58 °C (PCMI 58), 78 °C (PCMI 78) and 90 °C (PCMI 90). It was found that the radiator combined with PCMI 78 had an average heat output of 412 W, and the PCMI 78 could be completely charged within 8 off-peak hours at an electric heating power of 1270 W, in the case of the radiator external dimension L × B × H of 796 × 106 × 656 mm and the L/B ratio of 7.5. The experiment results indicated that the average room temperature could be maintained at 20.0 °C at an outdoor temperature of 5.2 °C when applying the electric radiator developed. Full article

(This article belongs to the Special Issue Optimization and Innovation of Energy Efficient Buildings and Smart Cities)

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31 pages, 31881 KiB

Open AccessArticle

A Retrofit Strategy for Real-Time Monitoring of Building Electrical Circuits Based on the SmartLVGrid Metamodel

by Rubens A. Fernandes, Raimundo C. S. Gomes, Ozenir Dias, Celso Carvalho, Israel G. Torné, Jozias P. Oliveira and Carlos T. C. Júnior

Energies 2022, 15(23), 9234; https://doi.org/10.3390/en15239234 - 6 Dec 2022

Cited by 2 | Viewed by 2296

Abstract

The Internet of things (IoT) paradigm promotes the emergence of solutions to enable energy-management strategies. However, these solutions may favor the disposal or replacement of outdated but still necessary systems. Thus, a proposal that advocates the retrofit of pre-existing systems would be an [...] Read more.

The Internet of things (IoT) paradigm promotes the emergence of solutions to enable energy-management strategies. However, these solutions may favor the disposal or replacement of outdated but still necessary systems. Thus, a proposal that advocates the retrofit of pre-existing systems would be an alternative to implement energy monitoring. In this sense, this work presents a strategy for monitoring electrical parameters in real time by using IoT solutions, cloud-resident applications, and retrofitting of legacy building electrical systems. In this implementation, we adapted the SmartLVGrid metamodel to systematize the insertion of remote monitoring resources in low-voltage circuits. For this, we developed embedded platforms for monitoring the circuits of a building electrical panel and application for visualization and data storage in the cloud. With this, remote monitoring of the consumer unit was carried out in relation to energy demand, power factor, and events of variations of electrical parameters in the circuits of the legacy distribution board. We also carried out a case study with the proposed system, identifying events of excess demand in the consumer unit, mitigating the individual contribution of the installation circuits in this process. Therefore, our proposal presents an alternative to enable energy management and maximum use of existing resources. Full article

(This article belongs to the Special Issue Optimization and Innovation of Energy Efficient Buildings and Smart Cities)

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20 pages, 3490 KiB

Open AccessArticle

Forecast of Energy Consumption and Carbon Emissions in China’s Building Sector to 2060

by Xingfan Pu, Jian Yao and Rongyue Zheng

Energies 2022, 15(14), 4950; https://doi.org/10.3390/en15144950 - 6 Jul 2022

Cited by 26 | Viewed by 2605

Abstract

The goal of reaching the peak of carbon in the construction industry is urgent. However, the research on the feasibility of realizing this goal and the implementation of relevant policies in China is relatively superficial. In view of the historical data of energy [...] Read more.

The goal of reaching the peak of carbon in the construction industry is urgent. However, the research on the feasibility of realizing this goal and the implementation of relevant policies in China is relatively superficial. In view of the historical data of energy consumption and building CO₂ emission from 1995 to 2019, this paper establishes a BP neural network model for predicting building CO₂ emissions. Moreover, the influencing factors, such as population, GDP, and total construction output, are introduced as the parameters in the model. Through the scenario analysis method explores the practical path to accomplish the peak of building CO₂ emissions. When using traditional prediction methods to predict building carbon emissions, the long prediction cycle will increase the possibility of significant errors. Therefore, this paper constructs the calculation model of building carbon emission and forecasts the future carbon emission value through the BP neural network to avoid the error caused by the nonlinear relationship between influencing factors and predicted value. It will effectively predict the feasibility of the carbon peak and the carbon-neutral target set by government, and provide a useful predictive tool for adjusting the new energy structure and formulating related emission reduction policies. Full article

(This article belongs to the Special Issue Optimization and Innovation of Energy Efficient Buildings and Smart Cities)

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12 pages, 2132 KiB

Open AccessArticle

How Do Temperature Differences and Stable Thermal Conditions Affect the Heat Flux Meter (HFM) Measurements of Walls? Laboratory Experimental Analysis

by Tullio de Rubeis, Luca Evangelisti, Claudia Guattari, Domenica Paoletti, Francesco Asdrubali and Dario Ambrosini

Energies 2022, 15(13), 4746; https://doi.org/10.3390/en15134746 - 28 Jun 2022

Cited by 2 | Viewed by 1934

Abstract

In recent years, experimental tests related to building components through laboratory facilities have relatively matured. The techniques are based on one-dimensional heat transfer by creating a permanent temperature difference over a specimen to control heat fluxes. The three main methods are the Guarded [...] Read more.

In recent years, experimental tests related to building components through laboratory facilities have relatively matured. The techniques are based on one-dimensional heat transfer by creating a permanent temperature difference over a specimen to control heat fluxes. The three main methods are the Guarded Hot Box (GHB) method, the Calibrated Hot Box (CHB) method, and the Heat-Flow Meter method (HFM). The HFM method is the most widely applied technique for measuring on-site U-values of building components and several scientific works stressed the need for high temperature differences between the environments, suggesting 10 °C or 15 °C. However, temperature stability and high temperature gradients are difficult to obtain, especially for Mediterranean climatic conditions. Starting from this, an experimental study was conducted through a GHB apparatus, setting temperature differences from 2 °C to 20 °C between the hot and cold chambers. Heat flow measurements were performed to compute the thermal conductance of a specimen characterized by a known stratigraphy, thus highlighting the effect of the low thermal gradient on data acquired by the heat flow sensor. It was found that, even for low temperature differences (2 °C) maintained by ensuring stable thermal conditions, the experimental results are comparable with those obtained for higher and usual temperature differences (20 °C). Full article

(This article belongs to the Special Issue Optimization and Innovation of Energy Efficient Buildings and Smart Cities)

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18 pages, 4102 KiB

Open AccessArticle

Efficiency Improvement of Photovoltaic Modules via Back Surface Cooling

by Piero Bevilacqua, Stefania Perrella, Daniela Cirone, Roberto Bruno and Natale Arcuri

Energies 2021, 14(4), 895; https://doi.org/10.3390/en14040895 - 9 Feb 2021

Cited by 33 | Viewed by 3024

Abstract

Crystalline silicon photovoltaics are a cardinal and well-consolidated technology for the achievement of energy efficiency goals, being installed worldwide for the production of clean electrical energy. However, their performance is strongly penalized by the thermal drift, mostly in periods of high solar radiation [...] Read more.

Crystalline silicon photovoltaics are a cardinal and well-consolidated technology for the achievement of energy efficiency goals, being installed worldwide for the production of clean electrical energy. However, their performance is strongly penalized by the thermal drift, mostly in periods of high solar radiation where solar cells reach considerably high temperatures. To limit this aspect, the employment of cooling systems appears a promising and viable solution. For this purpose, four different cooling systems, working on the photovoltaic (PV) panel back surface, were proposed and investigated in an experimental set-up located at the University of Calabria (Italy). Hourly electrical output power and efficiency were provided accounting for different meteorological conditions in several months of the experimental campaign. The results demonstrated that a simple spray cooling technique can provide an absolute increment of electrical efficiency of up to 1.6% and an average percentage increment of daily energy of up to 8% in hot months. More complex systems, based on ventilation or combining spray cooling and ventilation, were demonstrated not to be a viable option for PV performance improvement. Full article

(This article belongs to the Special Issue Optimization and Innovation of Energy Efficient Buildings and Smart Cities)

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