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20 pages, 9153 KiB

Open AccessArticle

Performance Assessment of Two Different Phase Change Materials for Thermal Energy Storage in Building Envelopes

by Ruta Vanaga, Jānis Narbuts, Ritvars Freimanis, Zigmārs Zundāns and Andra Blumberga

Energies 2023, 16(13), 5236; https://doi.org/10.3390/en16135236 - 7 Jul 2023

Cited by 1 | Viewed by 1244

Abstract

To meet the 2050 EU decarbonization goals, there is a need for new and innovative ideas to increase energy efficiency, which includes reducing the energy consumption of buildings and increasing the use of on-site renewable energy sources. One possible solution for achieving efficient [...] Read more.

To meet the 2050 EU decarbonization goals, there is a need for new and innovative ideas to increase energy efficiency, which includes reducing the energy consumption of buildings and increasing the use of on-site renewable energy sources. One possible solution for achieving efficient thermal energy transition in the building sector is to assign new functionalities to the building envelope. The building envelope can function as a thermal energy storage system, which can help compensate for irregularities in solar energy availability. This can be accomplished by utilizing phase change materials as the energy storage medium in the building envelope. In this paper, two phase change materials with different melting temperatures of 21 °C and 28 °C are compared for their application in a dynamic solar building envelope. Both experimental and numerical studies were conducted within the scope of this study. The laboratory testing involved simulating the conditions of the four seasons through steady-state and dynamic experiments. The performance of the phase change materials was evaluated using a small-scale PASLINK test stand that imitates indoor and outdoor conditions. A numerical model of a small-scale building envelope was created using data from laboratory tests. The purpose of this model was to investigate how the tested phase change materials perform under different climate conditions. The experimental findings show that RT21HC is better at storing thermal energy in the PCM and releasing it into the indoor area than RT28HC. On the other hand, the numerical simulation results demonstrate that RT28HC has an advantage in terms of thermal storage capacity in climates found in Southern Europe, as it prevents overheating of the room. Full article

(This article belongs to the Special Issue Energy Efficiency and Optimization Strategies in Buildings for a Sustainable Future)

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18 pages, 6519 KiB

Open AccessArticle

Design and Parametric Analysis of a Solar-Driven Façade Active Layer System for Dynamic Insulation and Radiant Heating: A Renovation Solution for Residential Buildings

by Emmanouil Katsigiannis, Petros Antonios Gerogiannis, Ioannis Atsonios, Ioannis Mandilaras and Maria Founti

Energies 2023, 16(13), 5134; https://doi.org/10.3390/en16135134 - 3 Jul 2023

Cited by 1 | Viewed by 1418

Abstract

The constantly increasing energy demand in aged households of urban areas highlights the need for effective renovation solutions towards nZEB to meet the European Commission’s energy reduction and decarbonization targets. To address these targets, a variety of retrofitting interventions are proposed that incorporate [...] Read more.

The constantly increasing energy demand in aged households of urban areas highlights the need for effective renovation solutions towards nZEB to meet the European Commission’s energy reduction and decarbonization targets. To address these targets, a variety of retrofitting interventions are proposed that incorporate hydronic systems into the building envelope, minimizing heat loss through the external walls and occasionally heating or cooling adjacent thermal zones. The present study analyses a low-temperature solar-powered hydronic active wall layer attached to the skin of a residential building in combination with solar collectors for heat generation. A typical floor of a five-storey, post-war, poorly insulated multi-family building is modelled considering two different climatic conditions: Berlin (Germany) and Kastoria (Greece). The design parameters, such as the area of the collector, the temperature of the fluid entering the active layer, the volume of the buffer tank and insulation thickness have been determined in order to optimize the impact on the heating system. Techno-economic assessment—followed by sensitivity analysis—has been conducted to scrutinize the feasibility of such a renovation solution. Last but not least, the nZEB compliance for both cases is examined based on EU and national nZEB definitions. The results indicate that a reduction of heating demand by up to 93% can be achieved, highlighting that such a renovation solution can be profitable in both examined locations while at the same time reaching the nZEB state. Full article

(This article belongs to the Special Issue Energy Efficiency and Optimization Strategies in Buildings for a Sustainable Future)

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28 pages, 6714 KiB

Open AccessArticle

Energy Efficiency and Optimization Strategies in a Building to Minimize Airborne Infection Risks

by Nasim Samadi and Mahdi Shahbakhti

Energies 2023, 16(13), 4960; https://doi.org/10.3390/en16134960 - 26 Jun 2023

Cited by 2 | Viewed by 1155

Abstract

Heating, ventilation, and air conditioning (HVAC) systems play a crucial role in either increasing or decreasing the risk of airborne disease transmission. High ventilation, for instance, is a common method used to control and reduce the infection risk of airborne diseases such as [...] Read more.

Heating, ventilation, and air conditioning (HVAC) systems play a crucial role in either increasing or decreasing the risk of airborne disease transmission. High ventilation, for instance, is a common method used to control and reduce the infection risk of airborne diseases such as COVID-19. On the other hand, high ventilation will increase energy consumption and cost. This paper proposes an optimal HVAC controller to assess the trade-off between energy consumption and indoor infection risk of COVID-19. To achieve this goal, a nonlinear model predictive controller (NMPC) is designed to control the HVAC systems of a university building to minimize the risk of COVID-19 transmission while reducing building energy consumption. The NMPC controller uses dynamic models to predict future outputs while meeting system constraints. To this end, a set of dynamic physics-based models are created to capture heat transfer and conservation of mass, which are used in the NMPC controller. Then, the developed models are experimentally validated by conducting experiments in the ETLC building at the University of Alberta, Canada. A classroom in the building is equipped with a number of sensors to measure indoor and outdoor environmental parameters such as temperature, relative humidity, and

{CO}_{2}

concentration. The validation results show that the model can predict room temperature and

{CO}_{2}

concentration by 0.8%, and 2.4% mean absolute average errors, respectively. Based on the validated models, the NMPC controller is designed to calculate the optimal airflow and supply air temperature for every 15 min. The results for real case studies show that the NMPC controller can reduce the infection risk of COVID-19 transmission below 1% while reducing energy consumption by 55% when compared to the existing building controller. Full article

(This article belongs to the Special Issue Energy Efficiency and Optimization Strategies in Buildings for a Sustainable Future)

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32 pages, 11596 KiB

Open AccessArticle

Techno-Economic Potential of Urban Photovoltaics: Comparison of Net Billing and Net Metering in a Mediterranean Municipality

by Enrique Fuster-Palop, Carlos Prades-Gil, Ximo Masip, J. D. Viana-Fons and Jorge Payá

Energies 2023, 16(8), 3564; https://doi.org/10.3390/en16083564 - 20 Apr 2023

Cited by 2 | Viewed by 1592

Abstract

Solar photovoltaic self-consumption is an attractive approach to increase autarky and reduce emissions in the building sector. However, a successful deployment in urban rooftops requires both accurate and low-computational-cost methods to estimate the self-consumption potential and economic feasibility, which is especially scarce in [...] Read more.

Solar photovoltaic self-consumption is an attractive approach to increase autarky and reduce emissions in the building sector. However, a successful deployment in urban rooftops requires both accurate and low-computational-cost methods to estimate the self-consumption potential and economic feasibility, which is especially scarce in the literature on net billing schemes. In the first part of this study, a bottom-up GIS-based techno-economic model has helped compare the self-consumption potential with net metering and net billing in a Mediterranean municipality of Spain, with 3734 buildings in total. The capacity was optimized according to load profiles obtained from aggregated real measurements. Multiple load profile scenarios were assessed, revealing that the potential self-sufficiency of the municipality ranges between 21.9% and 42.5%. In the second part of the study, simplified regression-based models were developed to estimate the self-sufficiency, self-consumption, economic payback and internal rate of return at a building scale, providing nRMSE values of 3.9%, 3.1%, 10.0% and 1.5%, respectively. One of the predictors with a high correlation in the regressions is a novel coefficient that measures the alignment between the load and the hours with higher irradiance. The developed correlations can be employed for any other economic or demand scenario. Full article

(This article belongs to the Special Issue Energy Efficiency and Optimization Strategies in Buildings for a Sustainable Future)

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29 pages, 5504 KiB

Open AccessArticle

Mutual Influence of External Wall Thermal Transmittance, Thermal Inertia, and Room Orientation on Office Thermal Comfort and Energy Demand

by David Božiček, Roman Kunič, Aleš Krainer, Uroš Stritih and Mateja Dovjak

Energies 2023, 16(8), 3524; https://doi.org/10.3390/en16083524 - 18 Apr 2023

Viewed by 1091

Abstract

Upgrades in building energy efficiency codes led to differences between buildings designed according to outdated codes and those with most recent requirements. In this context, our study investigates the influence of external wall thermal transmittance, thermal inertia, and orientation on energy demand (heating, [...] Read more.

Upgrades in building energy efficiency codes led to differences between buildings designed according to outdated codes and those with most recent requirements. In this context, our study investigates the influence of external wall thermal transmittance, thermal inertia, and orientation on energy demand (heating, cooling) and occupant thermal comfort. Simulation models of an office building were designed, varying (i) the thermal transmittance values (0.20 and 0.60 W/(m²K)), (ii) the room orientation (four cardinal directions), and (iii) the wall thermal inertia (approximately 60 kJ/(m²K) for low and 340 kJ/(m²K) for high thermal inertia. The energy demand for heating and cooling seasons was calculated for Ljubljana using EnergyPlus 9.0.0 software. The reduction of the external wall thermal transmittance value from 0.6 W/(m²K) to 0.2 W/(m²K) contributes to significant energy savings (63% for heating and 37% for cooling). Thermal inertia showed considerable potential for energy savings, especially in the cooling season (20% and 13%, depending on the external wall insulation level). In addition, the orientation proved to have a notable impact on heating and cooling demand, however not as pronounced as thermal inertia (up to 7% total energy demand). Comparison of the thermal comfort results showed that when internal air temperatures are identically controlled in all the rooms (i.e., internal air temperature is not an influencing factor), the external wall thermal transmittance, thermal inertia, and room orientation show negligible influence on the average occupant thermal comfort. The simultaneous achievement of thermally comfortable conditions in the working environment and low energy use can only be achieved by simultaneously considering the U-value and thermal inertia. Full article

(This article belongs to the Special Issue Energy Efficiency and Optimization Strategies in Buildings for a Sustainable Future)

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28 pages, 7106 KiB

Open AccessArticle

Decision Support for Defining Adaptive Façade Design Goals in the Early Design Phase

by Michael P. Voigt, Daniel Roth and Matthias Kreimeyer

Energies 2023, 16(8), 3411; https://doi.org/10.3390/en16083411 - 13 Apr 2023

Cited by 1 | Viewed by 1461

Abstract

Compared to conventional façades, adaptive façades (AFs) can adjust their properties in response to environmental changes and user requirements. Often performed through the integration of actuators, sensors, and control units, this provides benefits such as reduced energy consumption in buildings but also increases [...] Read more.

Compared to conventional façades, adaptive façades (AFs) can adjust their properties in response to environmental changes and user requirements. Often performed through the integration of actuators, sensors, and control units, this provides benefits such as reduced energy consumption in buildings but also increases the complexity of the façade design. To efficiently deal with the higher complexity, this article aims to provide suitable decision support for the early design phase, identify suitable design goals, and compare these to previously implemented Afs (make-or-buy decision). There is particular focus on the AF-specific characteristics, as these are new compared to well-known conventional façades. To systematically develop decision support, requirements are identified in expert interviews and the literature, and the current state of the art is evaluated against these. Research gaps found in current methods are addressed in this article, and continuous decision support is developed for the early design phase of an integrated design process. This support includes a checklist with AF-specific characteristics and a digitally implemented database of AFs. Based on the requirements, an evaluation is performed for both methods: this includes the comparison of the results to three ongoing AF projects and the assignment of 40 case studies to the database. Full article

(This article belongs to the Special Issue Energy Efficiency and Optimization Strategies in Buildings for a Sustainable Future)

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28 pages, 6448 KiB

Open AccessArticle

Retrofitting of the District Heating System Based on the Application of Heat Pumps Operating with Natural Refrigerants

by Damir Požgaj, Branimir Pavković, Boris Delač and Vladimir Glažar

Energies 2023, 16(4), 1928; https://doi.org/10.3390/en16041928 - 15 Feb 2023

Cited by 3 | Viewed by 1771

Abstract

The implementation of renewable energy sources and heat pumps with natural refrigerants in the existing 3rd-generation district heating (DH) systems is a promising technology for the conversion to a 4th-generation DH system. This paper aims to investigate this transition through a case study [...] Read more.

The implementation of renewable energy sources and heat pumps with natural refrigerants in the existing 3rd-generation district heating (DH) systems is a promising technology for the conversion to a 4th-generation DH system. This paper aims to investigate this transition through a case study for the existing DH system in Croatia. The district of Rijeka, which is considered in the case study, has an existing 3rd-generation DH system with a capacity of 9.2 MW, which was originally designed for a temperature regime of 130/70 °C and produces thermal energy from natural gas. In order to use heat pumps efficiently in such a system, the temperature of the distribution system and the energy consumption should be reduced. Trnsys software was used to perform complete dynamic simulations of the DH system. Used baseline models were validated according to the actual energy consumption reported by the heat supplier. The application of heat pumps with natural refrigerants in combination with on-site electricity production (PV system) can almost eliminate system CO₂ emissions, reduce primary energy consumption and lower operation costs. Simulations were performed for 18 different scenarios that included 2 different building envelope variants. The results were compared, then discussed and conclusions were drawn. Full article

(This article belongs to the Special Issue Energy Efficiency and Optimization Strategies in Buildings for a Sustainable Future)

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16 pages, 1941 KiB

Open AccessArticle

Numerical Analysis of Thermal Impact between the Cooling Facility and the Ground

by Paweł Sokołowski, Grzegorz Nawalany, Tomasz Jakubowski, Ernest Popardowski, Vasyl Lopushniak and Atilgan Atilgan

Energies 2022, 15(24), 9338; https://doi.org/10.3390/en15249338 - 9 Dec 2022

Cited by 1 | Viewed by 1057

Abstract

The article presents the results of research on the range of the impact of a cooling facility on the surrounding ground. An analysis of the heat exchange with the ground and through the building partitions was carried out. The analysis was carried out [...] Read more.

The article presents the results of research on the range of the impact of a cooling facility on the surrounding ground. An analysis of the heat exchange with the ground and through the building partitions was carried out. The analysis was carried out on the basis of the results of actual field tests carried out throughout the measurement year. The object of the research was an agricultural cold store located in southern Poland. The computational analysis of the interaction between the cooling facility and the ground was based on the numerical elementary balances method. The validation of the calculation model was performed based on the adopted boundary conditions. Calculations for the analyzed variants were carried out on the basis of a geometric model of the cooling facility built in the WUFI^®plus program, corresponding to the actual dimensions. The analysis of the energy balance of the studied facility showed that the share of energy flow through the floor to the ground constitutes 8.2% of all energy flows through other partitions and the ventilation system. In order to maintain the set air temperature inside the studied building, intensive cooling was required with an energy demand of 5184.5 kWh/year. The results of the research showed that the range of the thermal impact of the building changes depending on the location of the studied ground area in terms of cardinal direction. The external and internal microclimate characteristics also affect the extent of the impact of the cooling facility on the surrounding ground. Under the assumption of stable values of Θ_i within a range of 0.0–4.0 °C, the largest range of influence (4.0 m) occurs in the summer. Full article

(This article belongs to the Special Issue Energy Efficiency and Optimization Strategies in Buildings for a Sustainable Future)

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18 pages, 3825 KiB

Open AccessFeature PaperArticle

A Novel Temperature-Independent Model for Estimating the Cooling Energy in Residential Homes for Pre-Cooling and Solar Pre-Cooling

by Simon Heslop, Baran Yildiz, Mike Roberts, Dong Chen, Tim Lau, Shayan Naderi, Anna Bruce, Iain MacGill and Renate Egan

Energies 2022, 15(23), 9257; https://doi.org/10.3390/en15239257 - 6 Dec 2022

Cited by 1 | Viewed by 1790

Abstract

Australia’s electricity networks are experiencing low demand during the day due to excessive residential solar export and high demand during the evening on days of extreme temperature due to high air conditioning use. Pre-cooling and solar pre-cooling are demand-side management strategies with the [...] Read more.

Australia’s electricity networks are experiencing low demand during the day due to excessive residential solar export and high demand during the evening on days of extreme temperature due to high air conditioning use. Pre-cooling and solar pre-cooling are demand-side management strategies with the potential to address both these issues. However, there remains a lack of comprehensive studies into the potential of pre-cooling and solar pre-cooling due to a lack of data. In Australia, however, extensive datasets of household energy measurements, including consumption and generation from rooftop solar, obtained through retailer-owned smart meters and household-owned third-party monitoring devices, are now becoming available. However, models presented in the literature which could be used to simulate the cooling energy in residential homes are temperature-based, requiring indoor temperature as an input. Temperature-based models are, therefore, precluded from being able to use these newly available and extensive energy-based datasets, and there is a need for the development of new energy-based simulation tools. To address this gap, a novel data-driven model to estimate the cooling energy in residential homes is proposed. The model is temperature-independent, requiring only energy-based datasets for input. The proposed model was derived by an analysis comparing the internal free-running and air conditioned temperature data and the air conditioning data for template residential homes generated by AccuRate, a building energy simulation tool. The model is comprised of four linear equations, where their respective slope intercepts represent a thermal efficiency metric of a thermal zone in the template residential home. The model can be used to estimate the difference between the internal free-running, and air conditioned temperature, which is equivalent to the cooling energy in the thermal zone. Error testing of the model compared the difference between the estimated and AccuRate air conditioned temperature and gave average CV-RMSE and MAE values of 22% and 0.3 °C, respectively. The significance of the model is that the slope intercepts for a template home can be applied to an actual residential home with equivalent thermal efficiency, and a pre-cooling or solar pre-cooling analysis is undertaken using the model in combination with the home’s energy-based dataset. The model is, therefore, able to utilise the newly available extensive energy-based datasets for comprehensive studies on pre-cooling and solar pre-cooling of residential homes. Full article

(This article belongs to the Special Issue Energy Efficiency and Optimization Strategies in Buildings for a Sustainable Future)

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15 pages, 4427 KiB

Open AccessArticle

Potential of CO₂ Emission Reduction via Application of Geothermal Heat Exchanger and Passive Cooling in Residential Sector under Polish Climatic Conditions

by Natalia Fidorów-Kaprawy and Łukasz Stefaniak

Energies 2022, 15(22), 8531; https://doi.org/10.3390/en15228531 - 15 Nov 2022

Cited by 3 | Viewed by 1828

Abstract

The article summarizes the results of the 25-year time horizon performance analysis of the ground source heat pump that serves as a heat source in a detached house in the climatic conditions that prevail in Wrocław, Poland. The main aim is to assess [...] Read more.

The article summarizes the results of the 25-year time horizon performance analysis of the ground source heat pump that serves as a heat source in a detached house in the climatic conditions that prevail in Wrocław, Poland. The main aim is to assess the potential of ground regeneration and reduction of CO₂ emission by passive cooling application. The study adds value to similar research conducted worldwide for various conditions. The behavior of the lower source of the heat pump was simulated using EED software. The ground and borehole properties, heat pump characteristics, heating and cooling load, as well as the energy demand for domestic hot water preparation have been used as input data. Based on the brine temperatures for all analyzed cases including the ground with lower and higher values of conductivity and heat capacity, the borehole filler of inferior and superior thermal properties, and the passive cooling option turned on and off, the seasonal efficiencies of the heat pump have been calculated. The energy and emission savings calculations are based on the values obtained. The application of passive cooling reduces the brine temperature drop by 0.5 K to over 1.0 K in consecutive years in the analyzed cases and the thermal imbalance by 65.0% to 65.9%. Electric energy savings for heating and domestic hot water preparation reach 4.5%, but the greatest advantage of the system is the possibility of almost emission-free colling the living spaces which allows reducing around 33.7 GWh of electric energy and 1186–1830 kg of CO₂ emission for cooling. Full article

(This article belongs to the Special Issue Energy Efficiency and Optimization Strategies in Buildings for a Sustainable Future)

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30 pages, 4363 KiB

Open AccessArticle

Energy Analysis and Cost-Effective Design Solutions for a Dual-Source Heat Pump System in Representative Climates in Europe

by Maciej Milanowski, Antonio Cazorla-Marín and Carla Montagud-Montalvá

Energies 2022, 15(22), 8460; https://doi.org/10.3390/en15228460 - 12 Nov 2022

Cited by 5 | Viewed by 1670

Abstract

Ground-source heat pumps are an efficient technology for heating and cooling in buildings. However, the main limitation of their widespread application is the borehole heat exchanger’s (BHE) high investment cost. Hybridizing GSHP systems may overcome this limitation. This research work analyzes the long-term [...] Read more.

Ground-source heat pumps are an efficient technology for heating and cooling in buildings. However, the main limitation of their widespread application is the borehole heat exchanger’s (BHE) high investment cost. Hybridizing GSHP systems may overcome this limitation. This research work analyzes the long-term energy performance of a dual-source heat pump (DSHP) system, which uses the air or the ground as external heat/sink sources, in three representative European climates. First, a BHE cost-effective design solution is proposed for each climatology; then, a complete energy analysis is carried out, and the optimal source control parameters that best enhance the system performance in each climate are determined with the use of a complete dynamic model of the DSHP system developed in TRNSYS. Simulations were carried out for a 25-year operation period. Results show that the DSHP maintains the efficiency during the simulated period, with deviations lower than 1.7% in all cases. Finally, the source control optimization method results in only slight efficiency gains (<0.35%) but with a stronger effect on the ground/air use ratio (up to 25% use of air in cold climates), reducing the thermal imbalance of the ground and leading to a consequent BHE size length and cost reduction. Full article

(This article belongs to the Special Issue Energy Efficiency and Optimization Strategies in Buildings for a Sustainable Future)

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17 pages, 6042 KiB

Open AccessArticle

Interaction between a Cyclically Heated Building and the Ground, for Selected Locations in Europe

by Grzegorz Nawalany and Paweł Sokołowski

Energies 2022, 15(20), 7493; https://doi.org/10.3390/en15207493 - 12 Oct 2022

Cited by 2 | Viewed by 1120

Abstract

The aim of the study was to verify the impact of the location of a cyclically heated building on its energy needs and interaction with the environment. The model building was a large-scale broiler house located in southern Poland. In the examined facility, [...] Read more.

The aim of the study was to verify the impact of the location of a cyclically heated building on its energy needs and interaction with the environment. The model building was a large-scale broiler house located in southern Poland. In the examined facility, year-round measurements of selected parameters of the internal and external microclimate were carried out. The tests also covered the temperature of the soil in three measurement columns. The obtained measurement results were used for further computer analyses. A geometric model of the building was made and a calculation model specification was introduced, supported by specialized software for the physics of WUFI^®plus structures. The numerical analysis included validation. The validation results were assessed on the basis of the Coefficient of Determination method (R2) and the Goodness of Fit (GOF) method. Due to the lack of normality of the data distribution, a Rang-Spearman correlation analysis was carried out, which showed a very strong data correlation (0.94). The analysis of the R2 coefficient of determination confirmed the high reliability of the model (83%). In the case of the GOF method, a compliance value of 87% was obtained. Differentiated locations were adopted for further analysis, while maintaining the structure of the examined building in reality. Six European locations were selected: Kraków (Poland), Málaga (Spain), Brest (France), Visby (Sweden), Umea (Sweden), and Kiruna (Sweden). The analysis included three variants, in which the length of the technological break was adopted accordingly. A technological break between production cycles was assumed, the three variants of which lasted 3, 7, and 14 days. The analysis of the obtained results showed that the external microclimate significantly determines the energy interaction between the building and the ground. The length of the technological break is very important in a climate dominated by low temperatures (Northern Scandinavia). The south-western part of Europe allows the technological break to be extended without significant differences for heating purposes. The length of the technological break in the range of 3 to 14 days does not significantly affect the intensity of heat exchange with the ground on a yearly basis, regardless of the location of the building. There were differences of no more than 2% between the technological break lasting 3 days and the 14-day break. Full article

(This article belongs to the Special Issue Energy Efficiency and Optimization Strategies in Buildings for a Sustainable Future)

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34 pages, 14199 KiB

Open AccessArticle

Long-Term Evaluation of Comfort, Indoor Air Quality and Energy Performance in Buildings: The Case of the KTH Live-In Lab Testbeds

by Davide Rolando, Willem Mazzotti Pallard and Marco Molinari

Energies 2022, 15(14), 4955; https://doi.org/10.3390/en15144955 - 6 Jul 2022

Cited by 10 | Viewed by 2086

Abstract

Digitalization offers new, unprecedented possibilities to increase the energy efficiency and improve the indoor conditions in buildings in a cost-efficient way. Smart buildings are seen by many stakeholders as the way forward. Smart buildings feature advanced monitoring and control systems that allow a [...] Read more.

Digitalization offers new, unprecedented possibilities to increase the energy efficiency and improve the indoor conditions in buildings in a cost-efficient way. Smart buildings are seen by many stakeholders as the way forward. Smart buildings feature advanced monitoring and control systems that allow a better control of the buildings’ indoor spaces, but it is becoming evident that the massive amount of data produced in smart buildings is rarely used. This work presents a long-term evaluation of a smart building testbed for one year; the building features state-of-the-art monitoring capability and local energy generation (PV). The analysis shows room for improving energy efficiency and indoor comfort due to non-optimal control settings; for instance, average indoor temperatures in all winter months were above 24 °C. The analysis of electricity and domestic hot water use has shown a relevant spread in average use, with single users consuming approximately four times more than the average users. The combination of CO₂ and temperature sensor was sufficient to pinpoint the anomalous operation of windows in wintertime, which has an impact on energy use for space heating. Although the quantification of the impact of users on the overall energy performance of the building was beyond the scope of this paper, this study showcases that modern commercial monitoring systems for buildings have the potential to identify anomalies. The evidence collected in the paper suggests that this data could be used to promote energy-efficient behaviors among building occupants and shows that cost-effective actions could be carried out if data generated by the monitoring and control systems were used more extensively. Full article

(This article belongs to the Special Issue Energy Efficiency and Optimization Strategies in Buildings for a Sustainable Future)

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30 pages, 3790 KiB

Open AccessArticle

Evaluation of Alternatives for Energy Supply from Fuel Cells in Compact Cities in the Mediterranean Climate; Case Study: City of Valencia

by Irene Martínez Reverte, Tomás Gómez-Navarro, Carlos Sánchez-Díaz and Carla Montagud Montalvá

Energies 2022, 15(12), 4502; https://doi.org/10.3390/en15124502 - 20 Jun 2022

Cited by 1 | Viewed by 1840

Abstract

A study of energy supply alternatives was carried out based on a cogeneration fuel cell system fed from the natural gas network of compact Mediterranean cities. As a case study it was applied to the residential energy demands of the L’Illa Perduda neighbourhood, [...] Read more.

A study of energy supply alternatives was carried out based on a cogeneration fuel cell system fed from the natural gas network of compact Mediterranean cities. As a case study it was applied to the residential energy demands of the L’Illa Perduda neighbourhood, located in the east of the city of Valencia and consisting of 4194 residential cells. In total, eight different alternatives were studied according to the load curve, the power of the system, the mode of operation and the distribution of the fuel cells. In this way, the advantages and disadvantages of each configuration were found. This information, together with the previous study of the energy characteristics of the neighbourhood, enabled selection of the most promising configuration and to decide whether or not to recommend investment. The chosen configuration was a centralised system of phosphoric acid fuel cells in cogeneration, with approximately 4 MW of thermal power and an operating mode that varied according to the outside temperature. In this way, when heating is required, the plant adjusts its production to the thermal demand, and when cooling is required, the plant follows the electrical demand. This configuration presented the best energy results, as it achieved good coverage of thermal (62.5%) and electrical (88.1%) demands with good primary energy savings (28.36 GWh/year). However, due to the high power of the system and low maturity (i.e., high costs) of this technology, would be necessary to make a large initial economic investment of 15.2 M€. Full article

(This article belongs to the Special Issue Energy Efficiency and Optimization Strategies in Buildings for a Sustainable Future)

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25 pages, 5254 KiB

Open AccessArticle

Waste Heat Driven Multi-Ejector Cooling Systems: Optimization of Design at Partial Load; Seasonal Performance and Cost Evaluation

by Luca Viscito, Gianluca Lillo, Giovanni Napoli and Alfonso William Mauro

Energies 2021, 14(18), 5663; https://doi.org/10.3390/en14185663 - 9 Sep 2021

Cited by 3 | Viewed by 1494

Abstract

In this paper, a seasonal performance analysis of a hybrid ejector cooling system is carried-out, by considering a multi-ejector pack as expansion device. A 20 kW ejector-based chiller was sized to obtain the optimal tradeoff between performance and investment costs. The seasonal performance [...] Read more.

In this paper, a seasonal performance analysis of a hybrid ejector cooling system is carried-out, by considering a multi-ejector pack as expansion device. A 20 kW ejector-based chiller was sized to obtain the optimal tradeoff between performance and investment costs. The seasonal performance of the proposed solution was then evaluated through a dynamic simulation able to obtain the performance of the designed chiller with variable ambient temperatures for three different reference climates. The optimized multi-ejector system required three or four ejectors for any reference climate and was able to enhance the system performance at partial load, with a significant increase (up to 107%) of the seasonal energy efficiency ratio. The proposed system was then compared to conventional cooling technologies supplied by electric energy (electrical chillers EHP) or low-grade heat sources (absorption chillers AHP) by considering the total costs for a lifetime of 20 years and electric energy-specific costs for domestic applications from 0.10 to 0.50 €/kWhel. The optimized multi-ejector cooling system presented a significant convenience with respect to both conventional technologies. For warmer climates and with high electricity costs, the minimum lifetime for the multi-ejector system to achieve the economic break-even point could be as low as 1.9 years. Full article

(This article belongs to the Special Issue Energy Efficiency and Optimization Strategies in Buildings for a Sustainable Future)

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Review

Jump to: Research

29 pages, 2489 KiB

Open AccessReview

The Evolution of Crop-Based Materials in the Built Environment: A Review of the Applications, Performance, and Challenges

by Sina Motamedi, Daniel R. Rousse and Geoffrey Promis

Energies 2023, 16(14), 5252; https://doi.org/10.3390/en16145252 - 8 Jul 2023

Cited by 3 | Viewed by 1274

Abstract

The use of bio-based building materials as an alternative to replacing concrete or insulation materials is called to become a growing trend in the construction industry. On Science direct, publications concerning “bio-based materials” have increased from 4 in 2002 to 1073 twenty years [...] Read more.

The use of bio-based building materials as an alternative to replacing concrete or insulation materials is called to become a growing trend in the construction industry. On Science direct, publications concerning “bio-based materials” have increased from 4 in 2002 to 1073 twenty years later, demonstrating a growing interest in these materials However, among bio-based materials, crop or plant-based materials are not as popular. Due to their relative novelty, little is known about their potential applications, physical characteristics, and environmental impacts. The aim of this review is to qualitatively investigate the technical and environmental viability of crop-based materials in modern building applications. The specific objectives of the study consider greenhouse gas (GHG) emissions using life cycle assessment (LCA) approaches, contribution to the circular economy, and physical and hygrothermal characteristics. Another objective is to examine the progress of crop-based materials’ R&D, current bottlenecks, and a future roadmap for their evolution in state-of-the-art renewable buildings. The paper is broad enough to capture a large readership rather than experts in the domain. The review reveals that crop-based materials have the potential to replace traditional, highly emissive building materials. They offer low environmental impacts, in all stages of their life cycle. Full article

(This article belongs to the Special Issue Energy Efficiency and Optimization Strategies in Buildings for a Sustainable Future)

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