Paper on ACC design presented by University of Seville at the 5th European Conference on Supercritical Carbon Dioxide Energy Systems, Prague (Czech Republic)

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Schematic of ACC used as reference for SCARABEUS

 

The researchers at University of Seville have presented their work on the design and operation of air-cooled condensers for integration into Concentrated Solar Power plants using the SCARABEUS technology. This work has been carried out in the context of Work Package 5 (Techno-economic, Social and Environmental Assessments) but also in close collaboration with Work Package 4 (Air Cooled Condenser and Heat Exchanger Development).

Condensation of the working fluid at high ambient temperature is a differential feature of the SCARABEUS CONCEPT, setting it apart from standard supercritical Carbon Dioxide cycles where the working fluid cannot be condensed due to the unfeasibility of cooling CO2 down below the critical temperature. The design of condensers for operation at high pressure (~80 bar) and low temperature is therefore a innovation of the project. Also, the definition of operating strategies in order to reduce the negative impact of auxiliary (fan) power consumption on net cycle efficiency is critical in order to effectively attain the thermodynamic superiority of the SCARABEUS concept.

 

Flow chart of the Air Cooled Condenser design code

The paper can be downloaded free of charge from the conference website (link). Check the abstract below:

The SCARABEUS project investigates the use of CO2–based mixtures as working fluid in power cycles for nextgeneration Concentrated Solar Power plants. These fluids exhibit a critical temperature higher than pure CO2, enabling dry condensation of the working fluid even at the high ambient temperatures typical of sites with a high solar radiation. As a consequence, the SCARABEUS power cycle achieves higher thermal efficiency than standard sCO2 cycles, whose performance deteriorates significantly with ambient temperature. In any case, the actual feasibility of this concept is still to be confirmed by a complete techno-economic assessment. To that purpose, it is critical to accurately estimate the power consumption of the Heat Rejection Unit (HRU), which is one of the most important parasitic loads of the system.

Bearing all this in mind, this manuscript presents the design of a horizontal, direct air-cooled condenser (ACC). The bundle geometry proposed is comprised of seven tubes in three passes, with a staggered arrangement. The complete thermal model, developed in MatLab, has been already disclosed by the SCARABEUS consortium in a previous paper, and validated both experimentally in a dedicated test rig and against results obtained by the commercial software Xace®. The novelty in the present manuscript lies in the integration of this thermal model of the tubes with a complete design and integration tool of the whole heat rejection sub-system, including the design of a rotoronly axial fan and supporting frame. The impact of several design parameters (i.e., air temperature rise, acceptable hot pressure drops, tube length) is studied, taking into account auxiliary power consumption, footprint and cycle efficiency as main figures of merit. Two candidate mixtures are taken into account, identified in previous works by the same authors (85%CO2-15%C6F6 and 80%CO2-20%SO2), and a pure sCO2 case is also considered for the sake of comparison. The results show that, for a given gross cycle output, using pure sCO2 yields the smallest ACC with the lowest fan power consumption. Moreover, tube length and air face velocity are found to be the key-parameters driving the design process of an ACC, for which increasing tube length is always beneficial as far as the ACC design is concerned. Finally, various considerations regarding the role played by the optimum design of the ACC within the global optimisation of the power plant are made. It is found that the rationale employed for the design of the ACC may be in conflict with that used from an overall plant optimisation standpoint. It is hence concluded that the definition of the optimal design space of an Air-cooled Heat Exchanger (ACHE) must be included in the global optimisation of the power plant.

Paper on SARABEUS rig design and operation presented by Technical University of Vienna and Kelvion Thermal solution at the 5th European Conference on Supercritical Carbon Dioxide Energy Systems, Prague (Czech Republic)

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Front view of the SCARABEUS test rig at TU Wien

 

 

The researchers at the Technical University of Vienna (Austria) and Kelvion Thermal Solutions (France) have presented their work on the design of and operation of the SCARABEUS test rig at the Austrian academic institution. This work has been carried out in the context of Work Package 4 (Air Cooled Condenser and Heat Exchanger Development) and Work Package 6 (Test Rig and Experimental Validation) of SCARABEUS and is a cornerstone of the project, given the uniqueness of the rig constructed to validate the operation of heat exchangers on Carbon Dioxide mixtures.

Schematic of the SCARABEUS test rig at TU Wien

 

The paper can be downloaded free of charge from the conference website (link). Check the abstract below:

At TU Wien, a test facility working with supercritical carbon dioxide (sCO2) was commissioned in 2018. Since then, it has been used for various research tasks. This paper gives an overview about the three configurations of the facility with a focus on design, operation, and results. The authors present the design of components in the three configurations of the test facility: proof of concept of the simple cycle in supercritical and transcritical operation mode, heat transfer measurements, and future work. Special emphasis is given to challenges during engineering and operation. Our most relevant lessons learned are: that a commercial CO2 pump is not sufficient for cycle experiments, how to design a measurement section for heat transfer measurements, and that during experimental research, measurement-concepts and data reduction must be prioritized at all times.

 

Very nice representation of the SCARABEUS project team at the 5th European Conference on Supercritical Carbon Dioxide Energy Systems

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The 5th European Conference on Supercritical Carbon Dioxide Energy Systems was held in Prague (Czech Republic) on the 15th and 16th of March, 2023. The conference was very well organised by Prof. Dostal (Czech Technical University in Prague, Czech Republic) and Prof. Brillert (Technical University of Duisburg-Essen, Germany).

The excellent scientific programme was comprised of scientific and industrial presentations, combined with interesting keynotes and panel sessions. This unfolded in an excellent setup which enabled continuous networking and provided the younger researchers with an excellent opportunity to mix and exchange ideas with senior scientists and industrials leading the development of supercritical CO2 power systems. Amongst these Early Stage Researchers, we would like to congratulate Viktoria (TU Wien), Ettore (Politecnico di Milano) and Pablo (University of Seville) for their very good presentations, which attracted the interest of the audience.

The technical papers presented at the conference will be made available in Open-Access in the coming months. More information will be shared on the SCARABEUS website when available.

 

New paper by University of Seville presents the exergy analysis of different transcritical Carbon Dioxide cycles for CSP applications

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The SCARABEUS team at University of Seville has recently published an assessment of transcritical cycles running on different Carbon Dioxide mixtures in Concentrated Solar Power applications. This assessment makes use of the 2nd Law of Thermodynamics, rather than the 1st Law that is commonly used, with the aim to identify the room for further performance enhancement. Three different dopants are considered: Hexafluorobenzene (for cycles operating at temperatures lower than 600ºC), Titanium Tetrachloride and Sulphur Dioxide.

The paper has been published in Renewable Energy (Elsevier) and it is available in Open Access on the publisher’s website (link). Check the abstract below:

This paper focuses on the thermodynamic comparison between pure supercritical Carbon Dioxide and blended transcritical Carbon Dioxide power cycles by means of a thorough exergy analysis, considering exergy efficiency, exergy destruction and efficiency losses from Carnot cycle as main figures of merit. A reference power plant based on a steam Rankine cycle and representative of the state-of-the-art (SoA) of Concentrated Solar Power (CSP) plants is selected as base-case. Two different temperatures of the energy (heat) source are considered: 575 °C (SoA) and 725 °C (next generation CSP).

Compared to SoA Rankine cycles, CO2 blends enable cycle exergy efficiency gains up to 2.7 percentage points at 575 °C. At 725 °C, they outperform both SoA and pure CO2 cycles with exergy efficiencies up to 75.3%. This performance is brought by a significant reduction in the exergy destruction across the compression and heat rejection process rounding 50%. Additionally, it has been found that the internal condensation occurring inside the heat recuperator for those mixtures with a large temperature glide improves recuperator exergy efficiency, supporting the use of simpler layouts without split-compression. Finally, CO2 blends exhibit lower cycle exergy efficiency degradation than pure sCO2 in the event of an increase in the design ambient temperature.

The third episode of the webinar series on R& Activities on sCO2 in Europe organized by ETN will take place on March 6th

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As already published on this website, the CO2OLHEAT Project coordinated by ETN Global aims to demonstrate (at TRL7) the operation of a 2 MW Waste-Heat-to-power (WH2P) skid based on a 2MW-sCO2 cycle, able to efficiently valorize local waste heat at a significant temperature of 400°C in the CEMEX cement manufacturing plant in Prachovice (CZ).

 

ETN Global initiated, in September 2022, a series of webinars aimed at providing a forum where the R&D activities in the area of supercritical Carbon Dioxide technologies can be disseminated and made known to a wider audience. This initative has been joined by seven international and national projects, funded by the Horizon 2020 programme of the European Commission (CO2OLHEAT, COMPASsCO2, SCARABEUS, DESOLINATION, SOLARSCO2OL, sCO2-4-NPP) and by national R&D programmes in Germany (CARBOSOLA) and the Czech Republic (sCO2-Efekt).

 

The first webinar, held on September 22nd, aimed to introduce these projects in a single session, providing the main features of the project from technical and administrative standpoints. Opportunities for collaboration between projects and with stakeholders were also highlighted. Presentations can be downloaded from the SCARABEUS website: Link.

 

The second webinar took place on December 5th and presented a focus session discussing the fundamental and technical challenges posed for the design and operation of compressors in Supercritical Carbon Dioxide power systems. Three outstanding speakers covered these aspects; the session turned out very well and the feedback was very positive. Presentations can be downloaded from the SCARABEUS website: Link.

 

The next event will take place on March 6th, 16.00 – 17.00 CET. It will focus on heat exchanger technology, since heat exchangers are core equipment of sCO2 systems with an expectedly strong impact on Capital Costs and performance. Follow this link to registration: Link

 

 

New Supercritical Carbon Dioxide funded by Horizon Europe, and with several partners from within SCARABEUS

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A new project aimed at advancing supercritical Carbon dioxide technologies has just been kick-started in Europe. The project is titled Innovation in Supercritical Carbon Dioxide Power Generation Systems and is funded by the Marie Sklodowska-Curie subprogramme (MSCA) of Horizon Europe, under Grant Agreement No. 101073266.

 

The consortium is comprised of nine industrial beneficiaries, six academic beneficiaries, one associated partner whose action is funded by United Kingdom Research and Innovation (UKRI) and five additional associated partners supporting secondments of the doctoral candidates (see map below for details).

 

 

The project is coordinated by Prof. David T. Sánchez Martínez, University of Seville (Spain), and has a total duration of forty eight months, from January 2023 to December 2026. The total budget is M4.45 €, of which M3.84 € are funded by the European Commission and M0.61 € are funded by UKRI.

 

The aim of this four-year work programme is to undertake cutting edge multidisciplinary research and development to make a step change in understanding and advancing Supercritical CO2 based power generation systems’ technology. This will enable a step change in the role played by power and heat cycles to become major contributors to achieving the 2050 zero emissions targets. ISOP will achieve this goal while providing specialised training for 17 doctoral researchers to help establish the backbone of an important industry.

 

You can download the Press Release (download) for further information, or follow this link to navigate the project website: http://isopco2.eu/

 

ISOP PRESS