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Development, Analysis and Optimization of Sustainable Thermal Energy Systems and...
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Development, Analysis and Optimization of Sustainable Thermal Energy Systems and Technologies

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Energy Systems".

Deadline for manuscript submissions: closed (20 December 2022) | Viewed by 10442

Special Issue Editors

Dr. Mwesigye Aggrey

E-Mail Website
Guest Editor
Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, AB T2L 1Y6, Canada
Interests: thermodynamic optimization; geoexchange systems; alternative energy systems; solar thermal; heat transfer; ejector refrigeration systems; nanofluids; organic rankine cycles; thermal energy storage; phase change materials; building energy systems; renewable energy
Dr. Mohammad Moghimi Ardekani

E-Mail Website
Guest Editor
Department of Engineering, Staffordshire University, College Road, Stoke-On-Trent ST42DE, UK
Interests: solar thermal; thermal energy storages; clean energy technologies; computational fluid dynamics; optimization

Special Issue Information

Dear Colleagues, 

Thermal energy systems are made up of devices using one or more thermal energy sources for the production, generation, storage, distribution of heat, hot water, and/or cooling. They are fundamental to the generation and utilization of energy in our daily lives. The increasing concerns of climate change emanating from the increased emission of greenhouse gases necessitate the search, development, and optimization of energy systems utilizing renewable energy resources or improving existing systems to operate efficiently and sustainably. 

However, to integrate renewable energy resources into thermal energy systems and subsequently, into our energy mix, there are a number of challenges that need to be addressed. The cost of new technologies needs to be competitive with the energy from conventional systems, the intermittent nature of the available renewable energy resources requires hybridization or integration of energy storage and in most cases, these systems are not widely understood. There is therefore need for increased research efforts to develop novel thermal energy systems and enhance existing systems. 

This Special Issue on the “Development, Analysis, and Optimization of Sustainable Thermal Energy Systems and Technologies” aims to curate and present ongoing efforts and recent advances in the development, analysis, and optimization of sustainable thermal energy technologies. The issue welcomes experimental, analytical, and numerical investigations aimed at developing and optimizing the corresponding technologies. 

The topics include, but are not limited to:  

  • Thermal systems for distributed energy generation
  • Low carbon energy systems for space heating and cooling
  • Solar thermal/power energy systems
  • Geothermal energy systems
  • Emerging sustainable thermal energy technologies
  • Sustainable thermal energy systems and net-zero energy buildings
  • Heat transfer in sustainable thermal energy systems
  • Thermodynamic optimization of sustainable thermal energy systems
  • Thermal energy storage
Dr. Mwesigye Aggrey
Dr. Mohammad Moghimi Ardekani
Guest Editors

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 submissions that pass pre-check are 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. Processes is an international peer-reviewed open access monthly 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 2400 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

  • Distributed Energy Generation
  • Low Carbon Energy Systems
  • Net-Zero Energy Buildings
  • Renewable Thermal Technologies
  • Space Heating and Cooling
  • Sustainable Thermal Energy Systems
  • Thermodynamic Optimization
  • Thermal Energy Storage

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Published Papers (4 papers)

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Research

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21 pages, 4692 KiB  
Article
Investigation of a Novel Deep Borehole Heat Exchanger for Building Heating and Cooling with Particular Reference to Heat Extraction and Storage
by Jiaqi Zhang, Xinli Lu, Wei Zhang, Jiali Liu, Wen Yue and Feng Ma
Processes 2022, 10(5), 888; https://doi.org/10.3390/pr10050888 - 29 Apr 2022
Cited by 5 | Viewed by 1978
Abstract
Medium-depth and deep geothermal energy has been widely used because of its abundant resources and supply stability. Recently, attention has been given to the closed-loop heat extraction system using a deep borehole heat exchanger (DBHE), which enables geothermal energy to be harnessed almost [...] Read more.
Medium-depth and deep geothermal energy has been widely used because of its abundant resources and supply stability. Recently, attention has been given to the closed-loop heat extraction system using a deep borehole heat exchanger (DBHE), which enables geothermal energy to be harnessed almost everywhere. In this study, a check valve is adopted in a DBHE system in which the whole section of the well is used for heat extraction in winter during building heating and the upper part of the well is used for heat injection in summer during building cooling. The influence of injected water flowrates, water inlet temperatures, depths of the check valve and formation of thermal conductivities on the performance of this novel DBHE system has been investigated. It is found that heat injection through the upper part of the well in summer can improve the heat extraction rates to a certain extent during the heating season. In summer, the inlet temperature of water has a great influence on the heat injection rates. The increase in the depth of the check valve improves the heat injection rates of the novel DBHE system. When the depth of the check valve is 900 m, the heat injection rates in summer can reach 51.03 kW, which is 27.55% of the heat extraction rates in winter. In this case, the heat injection in summer has the greatest effect on the improvement of heat extraction in winter, which is 6.05 kW, accounting for 3.38% of the heat extraction in that year. It is found that the thermal conductivity of the formation has a great influence on the heat extraction rates in winter and heat injection rates in summer. The proposed novel DBHE system can be used to inject the heat discharged from the building in summer and extract geothermal energy for building heating in winter, forming a better heat balance at certain depths and resulting in a sustainable operation for heating and cooling. Another benefit of using this system is that the heat discharged from air conditioning into the air can be reduced in summer and “urban thermal pollution” can be alleviated. Full article
(This article belongs to the Special Issue Development, Analysis and Optimization of Sustainable Thermal Energy Systems and Technologies)
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22 pages, 2772 KiB  
Article
Theoretical Study of a Novel Power Cycle for Enhanced Geothermal Systems
by Changyou Geng, Xinli Lu, Hao Yu, Wei Zhang, Jiaqi Zhang and Jiansheng Wang
Processes 2022, 10(3), 516; https://doi.org/10.3390/pr10030516 - 4 Mar 2022
Cited by 3 | Viewed by 1980
Abstract
As obtained geofluids from enhanced geothermal systems usually have lower temperatures and contain chemicals and impurities, a novel power cycle (NPC) with a unit capacity of several hundred kilowatts has been configured and developed in this study, with particular reference to the geofluid [...] Read more.
As obtained geofluids from enhanced geothermal systems usually have lower temperatures and contain chemicals and impurities, a novel power cycle (NPC) with a unit capacity of several hundred kilowatts has been configured and developed in this study, with particular reference to the geofluid temperature (heat source) ranging from 110 °C to 170 °C. Using a suitable CO2-based mixture working fluid, a transcritical power cycle was developed. The novelty of the developed power cycle lies in the fact that an increasing-pressure endothermic process was realized in a few-hundred-meters-long downhole heat exchanger (DHE) by making use of gravitational potential energy, which increases the working fluid’s pressure and temperature at the turbine inlet and, hence, increases the cycle’s power output. The increasing-pressure endothermic process in the DHE has a better match with the temperature change of the heat source (geofluid), as does the exothermic process in the condenser with the temperature change of the sink (cooling water), which reduces the heat transfer irreversibility and improves the cycle efficiency. Power cycle performance has been analyzed in terms of the effects of mass fraction of the mixture working fluids, the working fluid’s flowrate and its DHE inlet pressure, geofluid flowrate, and the length of the DHE. Results show that, for a given geofluid’s temperature and mass flowrate, the cycle’s net power output is a strong function of the working-fluid’s flowrate, as well as of its DHE inlet pressure. Too high or too low of a DHE inlet pressure results in a lower power output. When geofluid temperature is 130 °C, the optimum DHE inlet pressure is found to be 11 MPa, corresponding to an optimum working-fluid flowrate of 6.5 kg/s. The longer the DHE, the greater the corresponding working-fluid flowrate and the higher the net power output. For geofluid temperature ranging from 110 °C to 170 °C, the developed NPC has a better thermodynamic performance than the conventional ORC. The advantage of using the developed NPC becomes obvious when geofluid temperature is low. The maximum net power output difference between the NPC and the ORC happens when the geofluid temperature is 130 °C and NPC’s working fluid mass fraction (R32/CO2) is 0.5/0.5. Full article
(This article belongs to the Special Issue Development, Analysis and Optimization of Sustainable Thermal Energy Systems and Technologies)
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19 pages, 3029 KiB  
Article
Simulations of Heat Supply Performance of a Deep Borehole Heat Exchanger under Different Scheduled Operation Conditions
by Jiaqi Zhang, Xinli Lu, Wei Zhang, Jiali Liu, Wen Yue, Dongxi Liu, Qingyao Meng and Feng Ma
Processes 2022, 10(1), 121; https://doi.org/10.3390/pr10010121 - 7 Jan 2022
Cited by 2 | Viewed by 1982
Abstract
With the changing world energy structure, the development of renewable energy sources is gradually accelerating. Among them, close attention has been given to geothermal energy because of its abundant resources and supply stability. In this article, a deep borehole heat exchanger (DBHE) is [...] Read more.
With the changing world energy structure, the development of renewable energy sources is gradually accelerating. Among them, close attention has been given to geothermal energy because of its abundant resources and supply stability. In this article, a deep borehole heat exchanger (DBHE) is coupled with a heat pump system to calculate the heat supply and daily electricity consumption of the system. To make better use of the peaks and valleys in electricity prices, the following three daily operating modes were studied: 24-h operation (Mode 1), 8-h operation plus 16-h non-operation (Mode 2), and two cycles of 4-h operation and 8-h non-operation (Mode 3). Simulation results show that scheduled non-continuous operation can effectively improve the outlet temperature of the heat extraction fluid circulating in the DBHE. The heat extraction rates of Mode 1 is 190.9 kW for mass flowrate of 9 kg/s; in Mode 2 and Mode 3 cases, the rates change to 304.7 kW and 293.0 kW, respectively. The daily operational electricity cost of Mode 1 is the greatest because of 24-h operation; due to scheduled non-continuous operation, the daily operational electricity cost of Mode 3 is only about 66% of that of Mode 2. After an 8-month period without heating, the formation-temperature can be restored within 4 °C of its original state; 90% recovery of the formation-temperature can be achieved by the end of the second month of the non-operation season. Full article
(This article belongs to the Special Issue Development, Analysis and Optimization of Sustainable Thermal Energy Systems and Technologies)
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Review

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21 pages, 48123 KiB  
Review
Progressive Development and Challenges Faced by Solar Rotary Desiccant-Based Air-Conditioning Systems: A Review
by Ranjan Pratap Singh and Ranadip K. Das
Processes 2021, 9(10), 1785; https://doi.org/10.3390/pr9101785 - 8 Oct 2021
Cited by 4 | Viewed by 3296
Abstract
A rotary desiccant-based air-conditioning system is a heat-driven hybrid system which combines different technologies such as desiccant dehumidification, evaporative cooling, refrigeration, and regeneration. This system has an opportunity to utilize low-grade thermal energy obtained from the sun or other sources. In this paper, [...] Read more.
A rotary desiccant-based air-conditioning system is a heat-driven hybrid system which combines different technologies such as desiccant dehumidification, evaporative cooling, refrigeration, and regeneration. This system has an opportunity to utilize low-grade thermal energy obtained from the sun or other sources. In this paper, the basic principles and recent research developments related to rotary desiccant-based cooling systems are recalled and their applications and importance are summarized. It is shown that with novel system configurations and new desiccant materials, there is great potential for improving the performance and consistency of rotary desiccant systems; at the same time, the use of solar energy for regeneration purposes can minimize the operating cost to a great extent. Some examples are presented to demonstrate how rotary desiccant air conditioning can be a promising solution for replacing traditional vapor-compression air-conditioning systems. Recent advances and ongoing research related to solar-powered hybrid rotary desiccant cooling systems are also summarized. The hybrid systems make use of a vapor-compression system in order to have better operational flexibility. These systems, although they consume electrical energy, use solar energy as the principal source of energy, and hence, significant savings of premium energy can be obtained compared to conventional vapor-compression systems. However, further research and development are required in order to realize the sustainable operation of solar rotary desiccant air-conditioning systems, as solar energy is not steady. Reductions in capital cost and size, along with improvements in efficiency and reliability of the system is still needed for it to become a player in the market of air conditioning. Full article
(This article belongs to the Special Issue Development, Analysis and Optimization of Sustainable Thermal Energy Systems and Technologies)
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