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Advances in Low-Temperature Solar Organic Rankine Cycle System

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

Deadline for manuscript submissions: closed (20 August 2020) | Viewed by 5457

Special Issue Editor

Department of Natural Resources Management & Agricultural Engineering, Agricultural University of Athens, Iera Odos 75, 11855 Athens, Greece
Interests: low-temperature heat-to-power conversion with ORC; solar sub-critical ORC prototypes (power generation and desalination) design, manufacturing and testing; volumetric expanders and heat exchangers design, manufacturing and testing; super-critical, TransCritical prototypes design manufacturing and testing; trilateral flash cycle
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Special Issue Information

Dear Colleagues,

Solar energy is a renewable energy of high importance and a further boost of utilization is crucial towards de-fossilizing the continually increasing energy demand and mitigating global warming. Solar energy is capable to satisfy effectively both electricity and thermal energy needs while a wide range of technologies is available covering different temperature ranges and systems’ sizes, to collect and convert heat to power. The use of low temperature solar heat to power generation is however a challenging and hot research issue, since it incorporates low heat to power conversion efficiency and a questionable cost-effectiveness.

The current state of the art indicates that the Organic Rankine Cycle (ORC) technology is almost exclusively used to convert low grade solar heat to electricity, due to its higher conversion efficiency and maturity, compared to all alternative technical solutions. However, several promising ideas towards improving further the thermal efficiency are under investigation such as expander liquid-flooding, supercritical operation, new organic fluids or TFC. Thermal efficiency improvement is a key challenge to enhance technical and economic attractiveness of low-grade solar heat-to-power conversion.

This Special Issue aims to further contribute in the efficient conversion of low temperature solar heat to electricity through the well-known technology of ORC. In this context, advances of all relevant technologies, design and control techniques and solutions are in the spotlight of this issue.

Dr. Dimitris S. Manolakos
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 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. 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 2600 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

  • system modelling: simulation/optimisation and design tools
  • innovative system architectures
  • low temperature solar collectors technologies
  • new/novel working fluids: properties, characterization, applications
  • expander technologies: turbines, volumetric expanders
  • solar ORC variants: trilateral flash cycle (TFC), supercritical ORC (SCORC), transcritical ORC (TCORC), single / two stages ORC
  • heat exchangers: evaporators, condensers, recuperators
  • interaction with other heat generation/handling sources: biomass, heat pumps, hybrid systems, waste heat recovery
  • testing of prototypes: results, assessment, experience gain
  • thermal storage
  • novel/smart control techniques
  • solar ORC applications
  • cogeneration, desalination and polygeneration systems
  • techno-economic assessment, Life Cycle Assessment (LCA)

Published Papers (2 papers)

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Research

13 pages, 8355 KiB  
Article
Numerical Modelling and Experimental Validation of Twin-Screw Expanders
Energies 2020, 13(18), 4700; https://doi.org/10.3390/en13184700 - 09 Sep 2020
Cited by 4 | Viewed by 2173
Abstract
Positive displacement machines have been identified as appropriate expanders for small-scale power generation systems such as Organic Rankine Cycles (ORCs). Screw expanders can operate with good efficiency in working fluids under both dry and two-phase conditions. Detailed understanding of the fluid expansion process [...] Read more.
Positive displacement machines have been identified as appropriate expanders for small-scale power generation systems such as Organic Rankine Cycles (ORCs). Screw expanders can operate with good efficiency in working fluids under both dry and two-phase conditions. Detailed understanding of the fluid expansion process is required to optimise the machine design and operation for specific applications, and accurate design tools are therefore essential. Using experimental data for air expansion, both CFD and chamber models have been applied to investigate the influence of port flow and leakage on the expansion process. Both models are shown to predict pressure variation and power output with good accuracy. The validated chamber model is then used to identify the optimal volume ratio and rotational speed for experimental conditions. Full article
(This article belongs to the Special Issue Advances in Low-Temperature Solar Organic Rankine Cycle System)
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29 pages, 8253 KiB  
Article
Assessment and Evaluation of the Thermal Performance of Various Working Fluids in Parabolic Trough Collectors of Solar Thermal Power Plants under Non-Uniform Heat Flux Distribution Conditions
Energies 2020, 13(15), 3776; https://doi.org/10.3390/en13153776 - 23 Jul 2020
Cited by 21 | Viewed by 2944
Abstract
Changing the heat transfer fluid (HTF) is a viable approach to study the corresponding effect on the thermal and hydraulic performances of parabolic trough collectors (PTC). Three categorized-types of pure fluids are used in this study; water, Therminol® VP-1 and molten salt. [...] Read more.
Changing the heat transfer fluid (HTF) is a viable approach to study the corresponding effect on the thermal and hydraulic performances of parabolic trough collectors (PTC). Three categorized-types of pure fluids are used in this study; water, Therminol® VP-1 and molten salt. The parametric comparison between pure fluids is also studied considering the effect of various inlet fluid temperatures and different Reynolds ( R e ) numbers on the thermal performance. Two low-Reynolds turbulence models are used; Launder and Sharma (LS) k-epsilon and Shear Stress Transport (SST) k-omega models. In order to assess the performance of each fluid, a number of parameters are analyzed including average Nusselt ( N u ) number, specific pressure drop distributions, thermal losses, thermal stresses and overall thermal efficiency of the PTC system. Results confirmed that changing the working fluid in the PTC enhances the overall heat transfer thereby improving thermal efficiency. For a temperature-range of (320–500) K, the Therminol® VP-1 performed better than water, resulting in higher N u numbers, lower thermal stresses and higher thermal efficiencies. On the other hand, for the common temperature-range, both Therminol® VP-1 and molten salt preformed more or less the same with Therminol® VP-1 case depicting lower thermal stresses. The molten salt is thus the best choice for high operating temperatures (up to 873 K) as it does not depict any significant reduction in the overall thermal efficiency at high temperatures; this leads to a better performance for the Rankine cycle. For the highest tested Reynolds number for an inlet fluid temperature of 320 K, a comparison of heat transfer performance (Nusselt number) and the overall thermal efficiency between Therminol® VP-1 and water showed that Therminol® VP-1 is the best candidate, whereas the molten salt is the best choice for a higher inlet temperature of 600 K. For example, at an inlet temperature of 320 K, the Nusselt number and overall thermal efficiency of therminol VP-1 were 910 and 49% respectively as opposed to 443 and 38% for water. On the other hand, at the higher inlet temperature of 600 K, these two parameters (Nusselt number and overall thermal efficiency) were recorded as 614 and 41 % for molten salt and 500 and 39 % for Therminol® VP-1. Full article
(This article belongs to the Special Issue Advances in Low-Temperature Solar Organic Rankine Cycle System)
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