Special Issue "Refrigeration, Air Conditioning and Heat Pumps: Energy and Environmental Issues"

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "Thermal Management".

Deadline for manuscript submissions: closed (30 June 2019).

Special Issue Editor

Prof. Fabio Polonara
E-Mail Website
Guest Editor
Dipartimento di Ingegneria Industriale e Scienze Matematiche Universita' Politecnica delle Marche Via Brecce Bianche 60131 Ancona, Italy
Tel. +39 071 2204432; Fax: +39 071 2204770
Interests: refrigeration; refrigerants; thermodynamic properties; heat pumps; demand side management; energy planning; LNG
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Special Issue Information

Dear Colleagues,

Refrigeration, air conditioning and heat pumps (RACHP) have an important impact on the final energy uses of many sectors of modern society, such as residential, commercial, industrial, transport, and automotive.

Moreover, they have also an important environmental impact due to the working fluids that deplete the stratospheric ozone layer and which are being phased out according to the Montreal Protocol (1989).

Last, but not least, high-Global-Working-Potential (GWP) working fluids (directly) and energy consumption (indirectly) are responsible for a non-negligible quota of Green House Gas (GHG) emissions in the atmosphere, therefore impacting on climate change. To cope with this aspect, the Kigali Amendment of the Montreal Protocol (2016), has started a phase down procedure for HFCs, to be completed by the mid-21st century.

All these issues will pose great challenges to the RACHP industry over the next few decades, such as:

  • the search for new working fluids, able to substitute high-GWP HFCs,
  • the safety aspects associated to the mostly flammable alternatives to high-GWP HFCs,
  • the expected growth of air conditioning in developing countries and the subsequent increase in GHG emissions,

The common ground for all these challenges is that the energy efficiency of components and systems has to increase in order to keep energy consumption and GHG emissions associated with RACHP under control.

The topics to be addressed by this Special Issue on “Refrigeration, Air Conditioning and Heat Pumps” include, but are not limited to:

  • Search for alternative, low-GWP working fluids,
  • Natural refrigerants and their applications,
  • Advanced thermodynamic analyses of reverse cycles and their applications,
  • Energy efficiency of vapor compression components and systems,
  • Demand Side Management and integration with Renewables,
  • Safety issues and risk assessment for flammable refrigerants,
  • Control and operations,
  • Not-In-Kind alternatives to vapor compression,
  • Energy Efficiency of RACHP applications (domestic, commercial, industrial, residential, transport, automotive)
  • Environmental impacts of RACHP,
  • Market trends and analyses.

Prof. Fabio Polonara
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Refrigeration
  • Air Conditioning
  • Heat Pumps
  • Natural Refrigerants
  • Hydro-Fluoro-Carbons (HFCs)
  • Hydro-Fluoro-Olefins (HFOs)
  • Ozone Depletion Potential (ODP)
  • Global Warming Potential (GWP)
  • Green House Gases (GHG)
  • Total Equivalent Warming Impact (TEWI)
  • Life Cycle Climate Performance (LCCP)
  • Vapor compression
  • Thermodynamic analysis
  • Energy Efficiency
  • Not-In-Kind Technologies
  • Absorption and Adsorption
  • District Cooling
  • Evaporative Cooling
  • Magnetic Refrigeration
  • Demand Side Management
  • Renewable Energy
  • Components and Systems
  • Cold Chain and its applications
  • Safety issues
  • Risk Assessment

Published Papers (8 papers)

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Research

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Open AccessArticle
Energetic and Exergetic Analysis of Low Global Warming Potential Refrigerants as Substitutes for R410A in Ground Source Heat Pumps
Energies 2019, 12(18), 3538; https://doi.org/10.3390/en12183538 - 16 Sep 2019
Abstract
In the European Union (EU), buildings are responsible for about 40% of the total final energy consumption, and 36% of the European global CO2 emissions. The European Commission released directives to push for the enhancement of the buildings energy performance and identified, [...] Read more.
In the European Union (EU), buildings are responsible for about 40% of the total final energy consumption, and 36% of the European global CO2 emissions. The European Commission released directives to push for the enhancement of the buildings energy performance and identified, beside the retrofit of the current building stock, Heating, Ventilation, and Air Conditioning (HVAC) systems as the other main way to increase renewable energy sharing and overall building energy efficiency. For this purpose, Ground Source Heat Pumps (GSHPs) represent one of the most interesting technologies to provide energy for heating, cooling, and domestic water production in residential applications, ensuring a significant reduction (e.g., up to 44% compared with air-source heat pumps) of energy consumption and the corresponding emissions. At present, GSHPs mainly employ the refrigerant R410A as the working fluid, which has a Global Warming Potential (GWP) of 2087. However, following the EU Regulation No. 517/2014 on fluorinated greenhouse gases, this high GWP refrigerant will have to be substituted for residential applications in the next years. Thus, to increase the sustainability of GSHPs, it is necessary to identify short time alternative fluids with lower GWP, before finding medium-long term solutions characterized by very low GWP. This is one of the tasks of the UE project "Most Easy, Efficient, and Low-Cost Geothermal Systems for Retrofitting Civil and Historical Buildings" (acronym GEO4CIVHIC). Here, a thorough thermodynamic analysis, based on both energy and exergy analysis, will be presented to perform a comparison between different fluids as substitutes for R410A, considered as the benchmark for GSHP applications. These fluids have been selected considering their lower flammability with respect to hydrocarbons (mainly R290), that is one of the main concerns for the companies. A parametric analysis has been performed, for a reversible GSHP cycle, at various heat source and sink conditions, with the aim to identify the fluid giving the best energetic performance and to evaluate the distribution of the irreversibilities along the cycle. Considering all these factors, R454B turned out to be the most suitable fluid to use in a ground source heat pump, working at given conditions. Special attention has been paid to the compression phase and the heat transfer in evaporator and condenser. Full article
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Open AccessArticle
Potential of District Cooling Systems: A Case Study on Recovering Cold Energy from Liquefied Natural Gas Vaporization
Energies 2019, 12(15), 3027; https://doi.org/10.3390/en12153027 - 06 Aug 2019
Abstract
District cooling systems (DCSs) are networks able to distribute thermal energy, usually as chilled water, from a central source to industrial, commercial, and residential consumers, to be used for space cooling/dehumidification. As cooling demand will increase significantly in the next decades, DCSs can [...] Read more.
District cooling systems (DCSs) are networks able to distribute thermal energy, usually as chilled water, from a central source to industrial, commercial, and residential consumers, to be used for space cooling/dehumidification. As cooling demand will increase significantly in the next decades, DCSs can be seen as efficient solutions to improve sustainability. Although DCSs are considered so relevant for new city developments, there are still many technical, economic, and social issues to be overcome to let such systems to spread out. Thus, this paper aims to highlight the advantages and issues linked to the adoption of DCSs for building cooling when cold is recovered from a specific application. A case study based on liquified natural gas (LNG) cold energy recovery from the transport sector is presented. Starting from the estimation of the free cooling availability, a DCS design method is proposed and the potential energy saving is investigated. Results show that a DCS using the cold waste derived from LNG can provide a relevant amount of electricity saving (about 60%) for space cooling compared to traditional solutions, in which standard air conditioning systems are installed in every building. Full article
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Open AccessArticle
Ground-Source Heat Pumps with Horizontal Heat Exchangers for Space Cooling in the Hot Tropical Climate of Thailand
Energies 2019, 12(7), 1274; https://doi.org/10.3390/en12071274 - 02 Apr 2019
Cited by 1
Abstract
The cooling of spaces in tropical regions, such as Southeast Asia, consumes a lot of energy. Additionally, rapid population and economic growth are resulting in an increasing demand for space cooling. The ground-source heat pump has been proven a reliable, cost-effective, safe, and [...] Read more.
The cooling of spaces in tropical regions, such as Southeast Asia, consumes a lot of energy. Additionally, rapid population and economic growth are resulting in an increasing demand for space cooling. The ground-source heat pump has been proven a reliable, cost-effective, safe, and environmentally-friendly alternative for cooling and heating spaces in various countries. In tropical countries, the presumption that the ground-source heat pump may not provide better thermal performance than the normal air-source heat pump arises because the difference between ground and atmospheric temperatures is essentially low. This paper reports the potential use of a ground-source heat pump with horizontal heat exchangers in a tropical country—Thailand. Daily operational data of two ground-source heat pumps and an air-source heat pump during a two-month operation are analyzed and compared. Life cycle cost analysis and CO2 emission estimation are adopted to evaluate the economic value of ground-source heat pump investment and potential CO2 reduction through the use of ground-source heat pumps, in comparison with the case for air-source heat pumps. It was found that the ground-source heat pumps consume 17.1% and 18.4% less electricity than the air-source heat pump during this period. Local production of heat pumps and heat exchangers, as well as rapid regional economic growth, can be positive factors for future ground-source heat pump application, not only in Thailand but also southeast Asian countries. Full article
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Open AccessArticle
Perspectives on Consumer Habits with Domestic Refrigerators and Its Consequences for Energy Consumption: Case of Study in Guanajuato, Mexico
Energies 2019, 12(5), 860; https://doi.org/10.3390/en12050860 - 05 Mar 2019
Cited by 1
Abstract
This work presents the main behaviors shown in the habits of consumers of domestic refrigerators, which influences the energy consumption of this appliance. This study is based on a series of surveys answered by 200 consumers from four cities in the State of [...] Read more.
This work presents the main behaviors shown in the habits of consumers of domestic refrigerators, which influences the energy consumption of this appliance. This study is based on a series of surveys answered by 200 consumers from four cities in the State of Guanajuato, Mexico. The questions were arranged with the aim of evaluating the general characteristics and usage habits such as refrigerator age, door opening frequency, damper position, load of food supplies, external and internal cleaning habits, and nearby heat sources, among other things. The randomly interviewed consumers were individuals between 20 and 60 years of age, who were interviewed using handmade surveys by experts in the field of refrigeration. In some cases, photographic evidence was gathered from the consumers’ refrigerators to represent the typical usage habits. In general, the results show that better usage habits are necessary from an energy point of view. Most consumers agree with adopting best practices for using their refrigerator. Full article
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Open AccessArticle
Energy Evaluation of Multiple Stage Commercial Refrigeration Architectures Adapted to F-Gas Regulation
Energies 2018, 11(7), 1915; https://doi.org/10.3390/en11071915 - 23 Jul 2018
Cited by 8
Abstract
This work analyses different refrigeration architectures for commercial refrigeration providing service to medium and low temperature simultaneously: HFC/R744 cascade, R744 transcritical booster, R744 transcritical booster with parallel compression, R744 transcritical booster with gas ejectors, R513A cascade/R744 subcritical booster, and R513A cascade/R744 subcritical booster [...] Read more.
This work analyses different refrigeration architectures for commercial refrigeration providing service to medium and low temperature simultaneously: HFC/R744 cascade, R744 transcritical booster, R744 transcritical booster with parallel compression, R744 transcritical booster with gas ejectors, R513A cascade/R744 subcritical booster, and R513A cascade/R744 subcritical booster with parallel compression. The models were developed using compressor manufacturers’ data and real restrictions of each system component. Limitations and operating range of each component and architecture were analysed for environment temperatures from 0 to 40 °C considering thermal loads and environment temperature profiles for warm climates. For booster systems, cascade with subcritical booster with parallel compression provide highest coefficient of performance (COP) for temperatures below 12 °C and above 30 °C with COP increases compared basic booster up to 60.6%, whereas for transcritical boosters, architecture with gas ejectors obtains the highest COP with COP increases compared to the basic booster up to 29.5%. In annual energy terms, differences among improved booster systems are below 8% in the locations analysed. In Total Equivalent Warming Impact (TEWI) terms, booster architectures get the lowest values with small differences between improved boosters. Full article
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Open AccessArticle
Assessing the Demand Side Management Potential and the Energy Flexibility of Heat Pumps in Buildings
Energies 2018, 11(7), 1846; https://doi.org/10.3390/en11071846 - 14 Jul 2018
Cited by 7
Abstract
The energy demand in buildings represents a considerable share of the overall energy use. Given the significance and acknowledged flexibility of thermostatically controlled loads, they represent an interesting option for the implementation of demand side management (DSM) strategies. In this paper, an overview [...] Read more.
The energy demand in buildings represents a considerable share of the overall energy use. Given the significance and acknowledged flexibility of thermostatically controlled loads, they represent an interesting option for the implementation of demand side management (DSM) strategies. In this paper, an overview of the possible DSM applications in the field of air conditioning and heat pumps is provided. In particular, the focus is on the heat pump sector. Three case studies are analyzed in order to assess the energy flexibility provided by DSM technologies classified as energy efficient devices, energy storage systems, and demand response programs. The load shifting potential, in terms of power and time, is evaluated by varying the system configuration. Main findings show that energy efficient devices perform strategic conservation and peak shaving strategies, energy storage systems perform load shifting, while demand response programs perform peak shaving and valley filling strategies. Full article
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Review

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Open AccessFeature PaperReview
Multi-Ejector Concept: A Comprehensive Review on its Latest Technological Developments
Energies 2019, 12(3), 406; https://doi.org/10.3390/en12030406 - 28 Jan 2019
Cited by 3
Abstract
The adoption of the EU F-Gas Regulation 517/2014 and the resulting development of the multi-ejector concept have led carbon dioxide to take center stage as the sole refrigerant (R744) in several applications. Therefore, a knock-on effect on the number of supermarkets relying on [...] Read more.
The adoption of the EU F-Gas Regulation 517/2014 and the resulting development of the multi-ejector concept have led carbon dioxide to take center stage as the sole refrigerant (R744) in several applications. Therefore, a knock-on effect on the number of supermarkets relying on “CO2 only” refrigeration systems has been experienced. Additionally, a global consensus of commercial multi-ejector based R744 units is also intensifying as a consequence of both the promising results obtained and the other measures in force for environment preservation. Furthermore, the multi-ejector concept is expected to offer significant energy savings in other high energy-demanding buildings (e.g., hotels, gyms, spas) as well, even in warm climates. In this investigation, the evolution of R744 ejector supported parallel vapor compression system layouts for food retail applications was summed up. Furthermore, their technological aspects, the results related to the main theoretical assessments and some relevant field/laboratory measurements were summarized. Also, the experience gained in the adoption of the multi-ejector concept in transcritical R744 vapor-compression units aimed at other energy intensive applications was presented. Finally, the persistent barriers needing to be overcome as well as the required future work were brought to light. Full article
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Open AccessReview
Control Strategies in Multi-Zone Air Conditioning Systems
Energies 2019, 12(3), 347; https://doi.org/10.3390/en12030347 - 23 Jan 2019
Abstract
In a commercial building, a significant amount of energy is used by the ventilation systems to condition the air for the indoor environments to satisfy the required quantity (temperature and humidity) and quality (amount of fresh air). For many years, Variable Air Volume [...] Read more.
In a commercial building, a significant amount of energy is used by the ventilation systems to condition the air for the indoor environments to satisfy the required quantity (temperature and humidity) and quality (amount of fresh air). For many years, Variable Air Volume (VAV) systems have been considered as the most efficient solutions by balancing the airflow volume based on the demand making them energy efficient when compared with the traditional Constant Air Volume (CAV) systems. However, the setpoints in VAV systems are often misread by the sensors due to stratification and formation of pollutant pockets and responding to design levels that overestimate the real-time demand conditions, which result in waste of energy, thermal discomfort and unhealthy air. In general, VAV devices are expensive, complicated and prone to failures and they are used only in medium and large projects. More recently, new technologies have evolved to solve this issue. In one of the new solutions, VAV motors terminals are replaced with flaps which are simpler and less expensive thus, they can be implemented in a wider range of projects. In systems, balancing and supplying the optimal airflow to reduce the energy consumption while delivering ideal thermal and Indoor Air Quality (IAQ) levels are the main challenges. In this paper, a comparison of the recent technologies with traditional VAV systems is presented to be used as a guild line for researchers and designers in the field of Heating Ventilation Air Conditioning (HVAC). Full article
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