Energies

Research

20 pages, 4506 KiB

Open AccessArticle

Modeling and Dynamic Simulation of a Hybrid Liquid Desiccant System with Non-Adiabatic Falling-Film Air-Solution Contactors for Air Conditioning Applications in Buildings

by Juan Prieto, Antonio Atienza-Márquez and Alberto Coronas

Energies 2021, 14(2), 505; https://doi.org/10.3390/en14020505 - 19 Jan 2021

Viewed by 2119

Abstract

This paper presents an experimentally validated, dynamic model of a hybrid liquid desiccant system. For this purpose, we developed new components for the air-solution contactors, which are of the non-adiabatic falling-film type with horizontal tubes (made of improved polypropylene) and the solution tanks. [...] Read more.

This paper presents an experimentally validated, dynamic model of a hybrid liquid desiccant system. For this purpose, we developed new components for the air-solution contactors, which are of the non-adiabatic falling-film type with horizontal tubes (made of improved polypropylene) and the solution tanks. We also provide new experimental correlations for both the tube-solution heat transfer coefficient and the mass transfer coefficient on the airside as a function of the air velocity. To validate the model, the results obtained from the dynamic simulations were compared with those obtained by monitoring a demonstration unit installed in a sports center in Taipei (Taiwan). Once validated, the model was used to perform a sensitivity analysis at different operational conditions, such as the inlet water temperatures in the air-solution contactors and the LiCl mass fraction at which the system operates. The results of the sensitivity analysis were used to optimize the seasonal performance in terms of comfort and energy required by the system. Compared with a conventional air-handling unit that controls air temperature and humidity, the annual energy savings of the liquid desiccant systems are 17%. Full article

(This article belongs to the Special Issue Sustainable and Efficient Impact in Building: Energy, Economic and Environmental Approach)

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28 pages, 15130 KiB

Open AccessArticle

Airtightness Analysis of the Built Heritage–Field Measurements of Nineteenth Century Buildings through Blower Door Tests

by Alexander Martín-Garín, José Antonio Millán-García, Juan María Hidalgo-Betanzos, Rufino Javier Hernández-Minguillón and Abderrahmane Baïri

Energies 2020, 13(24), 6727; https://doi.org/10.3390/en13246727 - 20 Dec 2020

Cited by 14 | Viewed by 4083

Abstract

Airtightness is a major issue in architectural design and it has a significant impact on the energy performance of buildings. Moreover, the energy behaviour of built heritage is due, to its singular characteristics, still a great unknown. The aim of this study is [...] Read more.

Airtightness is a major issue in architectural design and it has a significant impact on the energy performance of buildings. Moreover, the energy behaviour of built heritage is due, to its singular characteristics, still a great unknown. The aim of this study is to establish a better knowledge of the airtightness of historical buildings, based on an in depth field study using blower-door tests. A set of 37 enclosures were analyzed inside eight buildings located in historical areas of a Spanish city with a significant built heritage. They were constructed between 1882 and 1919 and include diverse construction typologies applied for many building uses such as residential, cultural, educational, administrative and emblematic. The results indicate lower values compared to other previous airtightness studies of historical buildings. The average air change rate was found to be n₅₀ = 9.03 h⁻¹ and the airtightness of the enclosures presented a wide range of between 0.68 and 37.12 h⁻¹. Three main levels of airtightness were identified with two thirds of the tested samples belonging to the intermediate level between 3–20 h⁻¹. To conclude, several correlations have been developed which provide a method to estimate air leakage and could serve as a basis for energy performance studies of these kinds of building. Full article

(This article belongs to the Special Issue Sustainable and Efficient Impact in Building: Energy, Economic and Environmental Approach)

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24 pages, 5721 KiB

Open AccessArticle

Influence of the Thermal Energy Storage Strategy on the Performance of a Booster Heat Pump for Domestic Hot Water Production System Based on the Use of Low Temperature Heat Source

by Ximo Masip, Emilio Navarro-Peris and José M. Corberán

Energies 2020, 13(24), 6576; https://doi.org/10.3390/en13246576 - 14 Dec 2020

Cited by 5 | Viewed by 1816

Abstract

Energy recovery from a low temperature heat source using heat pump technology is becoming a popular application. The domestic hot water demand has the characteristic of being very irregular along the day, with periods in which the demand is very intensive and long [...] Read more.

Energy recovery from a low temperature heat source using heat pump technology is becoming a popular application. The domestic hot water demand has the characteristic of being very irregular along the day, with periods in which the demand is very intensive and long periods in which it is quite small. In order to use heat pumps for this kind of applications efficiently, the proper sizing and design of the water storage tank is critical. In this work, the optimal sizing of the two possible tank alternatives, closed stratified tank and variable-water-volume tank, is presented, and their respective performance compared, for domestic hot water production based on low temperature energy recovery in two potential applications (grey water and ultra-low temperature district heating). The results show that the efficiency of these kind of systems is very high and that variable-water-volume tanks allow a better use of the energy source, with an 8% higher exergy efficiency and around 3% better seasonal performance factor (SPF), being able to provide similar comfort levels with a smaller system size. Full article

(This article belongs to the Special Issue Sustainable and Efficient Impact in Building: Energy, Economic and Environmental Approach)

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26 pages, 4722 KiB

Open AccessArticle

Influence of Atlantic Microclimates in Northern Spain on the Environmental Performance of Lightweight Concrete Single-Family Houses

by Daniel González-Prieto, Yolanda Fernández-Nava, Elena Marañón and Maria Manuela Prieto

Energies 2020, 13(17), 4337; https://doi.org/10.3390/en13174337 - 21 Aug 2020

Cited by 5 | Viewed by 1719

Abstract

The use of lightweight concrete for the construction of single-family houses has become increasingly popular in Spain. In this paper, single-family houses with different shape factors and window-to-wall ratios are analysed from both a thermal and environmental perspective using Passive House Planning Package [...] Read more.

The use of lightweight concrete for the construction of single-family houses has become increasingly popular in Spain. In this paper, single-family houses with different shape factors and window-to-wall ratios are analysed from both a thermal and environmental perspective using Passive House Planning Package (PHPP) software to calculate the energy demand. The study has been carried out for different Atlantic microclimates (coastal, inland, and mountain) in northern Spain. What most affects the thermal energy used for air conditioning is the variation of the microclimates, so the study focuses mainly on this aspect. Operational energy for heating has decreased greatly via the use of high degree of insulation and hence the next task is to decrease the total energy consumed taking into account the embodied energy. Impacts on Primary Energy and Global Warming Potential are calculated using a cradle-to-grave approach. The energy use for heating and domestic hot water is analysed for different thicknesses of insulation under three energy supply scenarios: electricity only (for 2018 and with the Spanish decarbonisation plan for 2030); heat pump plus electricity; and natural gas boiler. Even for houses with a good level of insulation, the ratio of operational-to-total impacts varies significantly: from 46% to 87% for primary energy and from 31% to 75% for global warming potential, depending on the shape factor of the house, the microclimate and the heat supply scenario. By applying future environmental policies, electricity can become a more environmentally friendly option than natural gas. Full article

(This article belongs to the Special Issue Sustainable and Efficient Impact in Building: Energy, Economic and Environmental Approach)

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18 pages, 3767 KiB

Open AccessArticle

Energy, Environmental and Economic Analysis of Air-to-Air Heat Pumps as an Alternative to Heating Electrification in Europe

by Olaia Eguiarte, Antonio Garrido-Marijuán, Pablo de Agustín-Camacho, Luis del Portillo and Ander Romero-Amorrortu

Energies 2020, 13(15), 3939; https://doi.org/10.3390/en13153939 - 01 Aug 2020

Cited by 15 | Viewed by 4169

Abstract

Heat pumps (HP) are an efficient alternative to non-electric heating systems (NEHS), being a cost-effective mean to support European building sector decarbonization. The paper studies HP and NEHS performance in residential buildings, under different climate conditions and energy tariffs, in six different European [...] Read more.

Heat pumps (HP) are an efficient alternative to non-electric heating systems (NEHS), being a cost-effective mean to support European building sector decarbonization. The paper studies HP and NEHS performance in residential buildings, under different climate conditions and energy tariffs, in six different European countries. Furthermore, a primary energy and environmental analysis is performed to evaluate if the use of HPs is more convenient than NEHS, based on different factors of the electric mix in each country. A specific HP model is developed considering the main physical phenomena occurring along its cycle. Open data from building, climatic and economic sources are used to feed the analysis. Ad hoc primary energy factors and greenhouse gas (GHG) emission coefficients are calculated for the selected countries. The costs and the environmental impact for both heating systems are then compared. The outcomes of the study suggest that, in highly fossil fuels dependent electricity mixes, the use of NEHS represents a more efficient decarbonization approach than HP, in spite of its higher efficiency. Additionally, the actual high price of the electric kWh hampers the use of HP in certain cases. Full article

(This article belongs to the Special Issue Sustainable and Efficient Impact in Building: Energy, Economic and Environmental Approach)

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14 pages, 2660 KiB

Open AccessArticle

Simulation and Thermo-Energy Analysis of Building Types in the Dominican Republic to Evaluate and Introduce Energy Efficiency in the Envelope

by Joan Manuel Felix Benitez, Luis Alfonso del Portillo-Valdés, Victor José del Campo Díaz and Koldobika Martin Escudero

Energies 2020, 13(14), 3731; https://doi.org/10.3390/en13143731 - 20 Jul 2020

Cited by 3 | Viewed by 2420

Abstract

The improvement of the energy performance in buildings is key for sustainable development, even more so in the case of the Dominican Republic (DR), which is committed to this goal but which has neither regulation nor specific social behavior in this field. The [...] Read more.

The improvement of the energy performance in buildings is key for sustainable development, even more so in the case of the Dominican Republic (DR), which is committed to this goal but which has neither regulation nor specific social behavior in this field. The main goal of this work is double; on one hand it is aimed at providing useable information for those who have the responsibly of making regulation norms and on the other, it is desirable to give an essential, technically proven and handy tool to those involved in the construction sector in improving the envelopes of buildings and to introduce good practices into the management of the energy systems of buildings. A case study of eight administrative buildings located in different climatic zones of the DR was carried out. A simulation tool was used for the study, and one of the buildings was monitored to verify the simulation work. Those factors that affect the development of the buildings in relation to thermo-energy consumption have been detailed. The large-scale heat gains resulting from the common glazing used by the tertiary sector in the Dominican Republic (including office buildings, hospitals and shops among others) illustrate the need for economically viable solutions in this sector. As a conclusion, it has been proved that the incidental thermal load of buildings could be reduced by up to 40%, thus in turn reducing the costs associated with the electricity needed to maintain the users’ desired thermal comfort level, as their influence in this sector is significant. Full article

(This article belongs to the Special Issue Sustainable and Efficient Impact in Building: Energy, Economic and Environmental Approach)

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30 pages, 10930 KiB

Open AccessArticle

Computational Simulation and Dimensioning of Solar-Combi Systems for Large-Size Sports Facilities: A Case Study for the Pancretan Stadium, Crete, Greece

by Dimitris Al. Katsaprakakis

Energies 2020, 13(9), 2285; https://doi.org/10.3390/en13092285 - 05 May 2020

Cited by 17 | Viewed by 2412

Abstract

The article examines the introduction of solar-combi systems in large-size sports facilities. The examined solar-combi systems consist of solar collectors, a biomass heater and thermal storage tanks. In a sense, they constitute hybrid thermal power plants. The full mathematical background is presented on [...] Read more.

The article examines the introduction of solar-combi systems in large-size sports facilities. The examined solar-combi systems consist of solar collectors, a biomass heater and thermal storage tanks. In a sense, they constitute hybrid thermal power plants. The full mathematical background is presented on the operation of such systems, along with a proposed operation algorithm, aiming at the maximization of the captured solar radiation. A case study is implemented for the coverage of the thermal energy needs for hot water production and swimming pools heating, met in the Pancretan Stadium, Crete, Greece. In this way, the article aims to indicate the technical and economic prerequisites that can guarantee the feasibility of the examined systems, highlighting the significant potential contribution of such systems towards the realization of energy transition plans from fossil fuels to renewables. The economic feasibility of the introduced system is based on the avoiding diesel oil and electricity procurement cost, consumed for the coverage of the thermal energy demands under consideration. The optimum dimensioning of the examined case study results to an annual thermal energy demand coverage balance of 55% by the solar collectors and 45% by the biomass heater, giving a payback period of 5–6 years. Full article

(This article belongs to the Special Issue Sustainable and Efficient Impact in Building: Energy, Economic and Environmental Approach)

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13 pages, 4421 KiB

Open AccessArticle

Energy Consumption Reduction of a Chiller Plant by Adding Evaporative Pads to Decrease Condensation Temperature

by Francisco J. Rey Martínez, Julio F. San José Alonso, Eloy Velasco Gómez, Ana Tejero González, Paula M Esquivias and Javier M. Rey Hernández

Energies 2020, 13(9), 2218; https://doi.org/10.3390/en13092218 - 02 May 2020

Cited by 5 | Viewed by 3627

Abstract

The high energy consumption of cooling systems justifies the need for strategies to increase the efficiency of the facilities, in order to reduce the related CO₂ emissions. This study aims to improve the performance and reduce the energy consumption of an 8.6 [...] Read more.

The high energy consumption of cooling systems justifies the need for strategies to increase the efficiency of the facilities, in order to reduce the related CO₂ emissions. This study aims to improve the performance and reduce the energy consumption of an 8.6 MW air cooled chiller. This installed capacity is biased due to the screw compressors, of 2.98 Energy Efficiency Ratio (EER) at full load (characteristics provided by the manufacturer). The chiller unit has been modified by placing evaporating cooling pads before the condensing coils. The chiller has been monitored for three months, recording over 544,322 measurements (5 min-step data), with and without the evaporative cooling pads, to assess the performance. Data comparison has been done by selecting two days (with and without evaporative panels) with the same health care load and temperatures. Implementing the proposed strategy yields an improvement in the European Seasonal Energy Efficiency Ratio (ESEER) from 3.69 to 4.83, while the Total Equivalent Warming Impact (TEWI) decreases about 1000 tCO₂. Energy savings of up to 32.6 MWh result into a payback period lower than 2 years. Full article

(This article belongs to the Special Issue Sustainable and Efficient Impact in Building: Energy, Economic and Environmental Approach)

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23 pages, 496 KiB

Open AccessArticle

A Novel Load Scheduling Mechanism Using Artificial Neural Network Based Customer Profiles in Smart Grid

by Zubair Khalid, Ghulam Abbas, Muhammad Awais, Thamer Alquthami and Muhammad Babar Rasheed

Energies 2020, 13(5), 1062; https://doi.org/10.3390/en13051062 - 29 Feb 2020

Cited by 15 | Viewed by 2736

Abstract

In most demand response (DR) based residential load management systems, shifting a considerable amount of load in low price intervals reduces end user cost, however, it may create rebound peaks and user dissatisfaction. To overcome these problems, this work presents a novel approach [...] Read more.

In most demand response (DR) based residential load management systems, shifting a considerable amount of load in low price intervals reduces end user cost, however, it may create rebound peaks and user dissatisfaction. To overcome these problems, this work presents a novel approach to optimizing load demand and storage management in response to dynamic pricing using machine learning and optimization algorithms. Unlike traditional load scheduling mechanisms, the proposed algorithm is based on finding suggested low tariff area using artificial neural network (ANN). Where the historical load demand individualized power consumption profiles of all users and real time pricing (RTP) signal are used as input parameters for a forecasting module for training and validating the network. In a response, the ANN module provides a suggested low tariff area to all users such that the electricity tariff below the low tariff area is market based. While the users are charged high prices on the basis of a proposed load based pricing policy (LBPP) if they violate low tariff area, which is based on RTP and inclining block rate (IBR). However, we first developed the mathematical models of load, pricing and energy storage systems (ESS), which are an integral part of the optimization problem. Then, based on suggested low tariff area, the problem is formulated as a linear programming (LP) optimization problem and is solved by using both deterministic and heuristic algorithms. The proposed mechanism is validated via extensive simulations and results show the effectiveness in terms of minimizing the electricity bill as well as intercepting the creation of minimal-price peaks. Therefore, the proposed energy management scheme is beneficial to both end user and utility company. Full article

(This article belongs to the Special Issue Sustainable and Efficient Impact in Building: Energy, Economic and Environmental Approach)

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