1,720,982 research outputs found
Techno-economic assessment of small-scale solar tower plants with modular billboard receivers and innovative power cycles
Full text linkThis work investigates performances and costs of various configurations of 5 MWel solar tower CSP plants, located in Sicily. The design of the plants aims at comparing two solar towers concepts (i.e., a single tower and modular towers), both adopting billboard receivers. A sensitivity on various heat transfer fluids (i.e., solar salt and sodium), storage fluids (solar salt and NaCl-MgCl2) and power block technologies (i.e., steam Rankine and sCO2 cycles) is also proposed. For each investigated plant configuration, tailored numerical models are presented to assess the performances of each plant subsystem (e.g., solar field, receiver, piping system, power cycle). The results show very competitive LCOE (between 160 and 180 $/MWhel), achievable with satisfactory capacity factors (around 55%), while suggesting good profitability levels for such investments in small scale CSP plants
Thermally integrated innovative Carnot batteries to upgrade and dispatch low temperature sensible waste heat
Full text linkThis work focuses on innovative thermally integrated Carnot batteries exploiting low temperature sensible waste heat, available at temperatures between 70°C and 100°C, while adopting a sensible solid-based thermal energy storage system. The charging cycle is based on transcritical heat pumps operating with CO2-based mixtures, representing the most innovative aspect of the work, whereas the discharging cycle runs with conventional pure fluid ORC. The heat pumps adopting CO2 doped with a low fraction of hydrocarbons can achieve very high second law efficiencies (around 70%), even in a simplified cycle layout with a sensible heat source, storing heat in the low-cost storage operating between 50°C and 150°C. Similarly, an ORC with cyclopropane as working fluid is identified as the most promising solution for the discharging phase of the Carnot battery. Results show RTE of around 62% and 84% for the thermally integrated systems with waste heat sources at 70°C and 100°C, respectively, and an air-cooled ORC. Finally, calculations show that RTE close to 100% is possible with a water-cooled ORC. Both the computed values of RTEs and the high compactness and effectiveness of the innovative heat pumps highlight the necessity for additional research into thermally integrated Carnot batteries as a way to exploit and dispatch sensible waste heat
Thermal desalination from rejected heat of power cycles working with CO2-based working fluids in CSP application: A focus on the MED technology
Full text linkThis work analyses the integration of concentrated solar power plants based on innovative sCO2 cycles and transcritical CO2-based mixtures cycles with thermal desalination plants adopting the conventional MED technology. In these cogeneration plants, all heat rejected from the cycle is exploited by the desalination system, avoiding any parasitic electric consumption of the fans of the air-cooled heat rejection unit. The MED layout proposed exploits both latent effects, from 3 to 8, and sensible effects, to match at best the temperature level at which the heat is available from the power cycles, delivered to the desalination plant through an intermediate loop of demineralized water. The cogenerative solution is designed in all its components and proposed in this work as a 100 MWel solar tower CSP plant located in Sevilla, resulting in a yearly production of around 400 GWhel/year and between 3.5 and 4.2 Mm3 of freshwater produced, depending on the configuration analysed. Various power cycle layouts are investigated, working with both sCO2 and the innovative CO2 + C6F6 mixture as working fluids. Regarding the solar plant, detailed models for the solar field optical analysis and the receiver thermal analysis are adopted. The seawater desalination plant, when coupled with this category of CSP plants, presents a thermal consumption between 180 and 140 kWh/m3. Finally, the cogenerative plants performances are compared in terms of levelized cost of electricity, with a slight edge for the innovative mixture cycles, and levelized cost of water, in a range between 1 and 2 $/m3
Adoption of CO2 mixtures as working fluid for CSP cycles with linear collectors and molten salts as HTF
Full text linkThis work deals with the adoption of CO2-based mixtures as working fluid in transcritical cycles for CSP applications. A direct comparison with the small-scale CSP plant based on a Rankine cycle operating in Partanna (Italy) is developed to verify the potential advantages of the proposed novel cycles both in design conditions and on yearly basis. The solar plant consists of linear Fresnel reflectors using solar salts as HTF and a large direct thermal energy storage. The solar to thermal performances of the power plant are evaluated with the software SAM, while the design of the cycle with the innovative working fluids (CO2+C6F6 and CO2+C6F12O) is developed in ASPEN Plus. An annual analysis based on hourly DNI data is then performed to assess the yearly electricity yield together with a preliminary economic analysis. The results of the most advanced cycle layout exploiting the innovative working fluid evidence a minor reduction of the computed LCOE when compared to the traditional technology (around 10%), a result highly sensitive to the power block costs, and a 2GWh increment in the yearly energy produced (13% of the Rankine production)
Preliminary Characterization of the Desolination Project Demo Plant: Design and Off-Design Operability
Full text linkThis work presents the preliminary performance of the simple recuperative transcritical power cycle of the DESOLINATION project demo plant. The cycle operates with the CO2+SO2 mixture and it is air-cooled, built in a CSP-like environment with high radiation and high ambient temperature. The axial turbine, with a flowrate of 0.2 m3/s at its inlet, imposes the size of the cycle at 1.8 MWel. Innovative recuperators and primary heat exchangers with internal gyroid structures are adopted, modelled with a simplified approach in MATLAB by fitting results of CFD simulations. By modelling the cycle off-design in sliding pressure, cycle efficiencies above 30% can be obtained, even at part load. Fixing a high ambient temperature at design conditions, the cycle cannot operate with ambient temperatures below 30°C if the condenser fans work at fixed speed, whereas ambient temperatures of 10°C are possible modifying the air velocity. By preliminary sizing the system piping, it is determined that the overall cycle inventory depends only on the conditions in the condenser, determined by the ambient temperature. Accordingly, an inventory variation of around 300 kg must be handled to correctly operate in off-design
Thermal Desalination Through Forward Osmosis Coupled With CO2-Mixture Power Cycles for CSP Applications
Full text linkThis work, performed in the framework of the H2020 EU project “DESOLINATION”, analyses the coupling between CSP plants using transcritical power cycles with CO2-mixtures and an innovative thermal desalination technique based on Forward Osmosis. Calculations are presented for a large scale CSP plant with central tower receiver and direct storage with solar salts in Dubai, adopting the mixtures CO2+SO2 and CO2+C6F6 in the power cycles. The heat rejected from the cycle condenser is recovered directly by the FO plant, where the draw solute is heated up from 40 °C to 76 °C, to allow for the regeneration of the draw solution used in the forward osmosis membrane. The thermo-responsive polymer adopted is PAGB2000, already considered in literature as a promising option. Results show a very effective synergy between the electricity and the freshwater production: high yearly solar to electric efficiencies are possible (around 19%), with a low freshwater specific thermal consumption (around 100 kWhth/m3). The proposed desalination method is more effective than a conventional MED system (with +50% of yearly freshwater produced), while a larger solar field (+28% in surface area) is necessary for a PV+RO plant to produce annually both the energy and freshwater produced by the CSP+FO plants
Transcritical Cycles With CO2-based Mixtures for CSP Applications: An Overview of the SCARABEUS Findings
Full text linkThis work summarizes the methodology developed within the H2020 EU project SCARABEUS for the analysis of innovative CO2-based mixtures used as working fluid in transcritical cycles for CSP applications. By adding a specific quantity of carefully selected dopant to CO2 it is possible to reach a high mixture critical temperature, suitable for air cooled cycles at very high minimum temperature in hot environments with high efficiencies. Along the methodology, some results related to the design of the turbine and the heat exchangers for the innovative mixtures are presented, including a focus on the system integration between the power block and the solar plant: as such, these results can be considered as interesting research outcomes to widen the knowledge on innovative solutions for efficient power cycles. The new power cycles are foreseen to drastically increase the profitability and cut the specific cost of CSP systems with respect to the state-of-the-art
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Design of an Air-Cooled Condenser for CO2-Based Mixtures: Model Development, Validation and Heat Exchange Gain with Internal Microfins
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