PUBLICATIONS

@article{Grigoriev2021a,

title = {Optimal Sizing of Cylindrical Receivers for Surround Heliostat Fields Using fluxtracer},

author = {Victor Grigoriev and Kypros Milidonis and Marios Constantinou and Clotilde Corsi and John Pye and Manuel J. Blanco},

doi = {10.1115/1.4051315},

issn = {0199-6231},

year  = {2021},

date = {2021-12-01},

journal = {Journal of Solar Energy Engineering},

volume = {143},

number = {6},

publisher = {American Society of Mechanical Engineers Digital Collection},

abstract = {This article presents an innovative approach for optimizing the dimensions of cylindrical receivers for solar tower systems. In this approach, a single set of rays, representative of a complete annual ray-tracing simulation of the solar tower system, is used and processed to evaluate numerous receiver designs simultaneously and to select the optimum. The simultaneous evaluation of receiver designs is achieved by exploiting the geometrical properties of the intersection between a ray and a cylinder, which allows estimating the annual energy intercepted by receivers of different heights without the need for processing the annual set of rays more than one time. Once the annual intercepted energy is known for each receiver, the application of a costing function estimating the receiver cost as a function of its surface area allows to estimate their cost and, therefore, to select the receiver dimensions that will yield a minimum surface area for a given annual energy interception factor. The overall workflow to carry out the mentioned receiver optimization approach has been implemented by adapting several open-source tools that The Cyprus Institute (CyI) is developing in collaboration with the Australian National University (ANU) to assist in the modeling, analysis, design, and optimization of concentrated solar thermal (CST) systems. This article also presents a detailed overview of the overall simulation workflow as well as a case study demonstrating the capabilities of the approach.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Montenon2021,

title = {Economic assessment of a pv hybridized linear fresnel collector supplying air conditioning and electricity for buildings},

author = {Alaric C. Montenon and Costas N. Papanicolas},

url = {https://www.mdpi.com/1996-1073/14/1/131},

doi = {10.3390/en14010131},

issn = {19961073},

year  = {2021},

date = {2021-12-01},

journal = {Energies},

volume = {14},

number = {1},

pages = {131--1 -- 131--25},

publisher = {MDPI AG},

abstract = {The present study evaluates the potential upgrade of a Linear Fresnel Reflector (LFR) collector at the Cyprus Institute (CyI) with photovoltaics via the calculation of the Levelized Cost Of Heat (LCOH). For over 4 years the collector has been supplying heating and cooling to the Novel Technologies Laboratory (NTL) of the Cyprus Institute (CyI). Extensive measurements have been carried out both on the LFR and NTL to render real numbers in the computations. This hybridization would be undertaken with the installation of PV arrays under mirrors, so that the collector is able to either reflect direct radiation to the receiver to process heat or to produce electricity directly in the built environment. The main objective is the decrease of the LCOH of Linear Fresnel collectors, which hinders their wider deployment, while air conditioning demand is globally booming. The results show that the LCOH for a small LFR to supply air conditioning is high, ce25.2–30.1 per kWh, while the innovative PV hybridization proposed here decreases it. The value of the study resides in the real data collected in terms of thermal efficiency, operation, and maintenance.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Milidonis2021,

title = {Review of application of AI techniques to Solar Tower Systems},

author = {Kypros Milidonis and Manuel J. Blanco and Victor Grigoriev and Constantinos F. Panagiotou and Aristides M. Bonanos and Marios Constantinou and John Pye and Charles Alexis Asselineau},

doi = {10.1016/J.SOLENER.2021.06.009},

issn = {0038-092X},

year  = {2021},

date = {2021-08-01},

journal = {Solar Energy},

volume = {224},

pages = {500--515},

publisher = {Pergamon},

abstract = {Artificial Intelligence (AI) is increasingly playing a significant role in the design and optimization of renewable energy systems. Many AI approaches and technologies are already widely deployed in the energy sector in applications such as generation forecasting, energy efficiency monitoring, energy storage, and overall design of energy systems. This paper provides a review of the applications of key AI techniques on the analysis, design, optimization, control, operation, and maintenance of Solar Tower systems, one of the most important types of Concentrating Solar Thermal (CST) systems. First, key AI techniques are briefly described and relevant examples of their application to CST systems in general are provided. Subsequently, a detailed review of how these AI techniques are being used to advance the state of the art of solar tower systems is presented. The review is structured around the different subsystems of a solar tower system.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Blanco2021,

title = {Minimizing the computational effort to optimize solar concentrators with the open-source tools sunpath and tonatiuh++},

author = {Manuel J. Blanco and Victor Grigoriev and Kypros Milidonis and George Tsouloupas and Miguel Larrañeta and Manuel Silva},

url = {https://www.mdpi.com/1197782},

doi = {10.3390/en14154412},

issn = {19961073},

year  = {2021},

date = {2021-07-01},

journal = {Energies},

volume = {14},

number = {15},

abstract = {Integrals that are of interest in the analysis, design, and optimization of concentrating solar thermal systems (CST), such as the annual optical efficiency of the light collection and concentration (LCC) subsystem, can be accurately computed or estimated in two distinct ways: on the time domain and on the spatial domain. This article explores these two ways, using a case study that is highly representative of the commercial CST systems being deployed worldwide. In the time domain, the computation of these integrals are explored using 1-min, 10-min, and 1-h solar DNI input data and using The Cyprus Institute (CyI)'s High-Performance Computing (HPC) system and an open-source ray tracer, Tonatiuh++, being actively developed at CyI. In the spatial domain, the computation of these integrals is explored using SunPATH, another open-source software tool being actively developed at CyI, in tandem with Tonatiuh++. The comparison between the time and spatial domain approach clearly indicate that the spatial domain approach using SunPATH is dramatically more computationally efficient than the time domain approach. According to the results obtained, at least for the case study analyzed in this article, to compute the annual energy delivered by the LCC subsystem with a relative error less than 0.1%, it is enough to provide SunPATH with 1-h DNI data as input, request from SunPATH the sun position and weights of just 30 points in the celestial sphere, and run Tonatiuh++ to simulate these 30 points using 15 million rays per run. As the test case is highly representative, it is expected that this approach will yield similar results for most CST systems of interest.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Grigoriev2021,

title = {Method to determine the tracking angles of heliostats},

author = {Victor Grigoriev and Kypros Milidonis and Manuel J. Blanco and Marios Constantinou},

url = {https://linkinghub.elsevier.com/retrieve/pii/S2215016121000376},

doi = {10.1016/j.mex.2021.101244},

issn = {22150161},

year  = {2021},

date = {2021-01-01},

journal = {MethodsX},

volume = {8},

number = {MEX 101244},

pages = {101244},

publisher = {Elsevier},

abstract = {The heliostats with two tracking axes are considered, and the method is presented to find the tracking angles for reflection of sun light to a given target. An important advantage of the method is that the tracking axes are not required to be orthogonal like in azimuth-elevation, tilt-roll or target-aligned heliostats. All of these configurations are covered in a unified way, and the presented solution is valid even for arbitrary orientation of tracking axes. The ability to have such a general solution is very valuable, because the orthogonality condition may not hold precisely for manufacturing reasons or due to degradation of heliostats. These deviations need to be corrected properly to achieve a high concentration of sun light. The offsets between tracking axes are also taken into account. However, the targeting problem for heliostats in this case becomes considerably different from the inverse kinematic problems for robotic arm manipulators. It is shown that the tracking angles can be found iteratively, and the convergence of results is very fast for a typical set of parameters used in solar thermal plants. To simplify the use of the method, a Python-library HelioK was developed, and it is demonstrated how to work with it in a Jupyter-notebook. To explain the kinematics of heliostats better, a 3D model of heliostat is provided, which was made and animated in an open-source 3D editor Blender. The main highlights of the method: • The tracking axes and the facet of heliostat can have an arbitrary orientation, and there can be offsets between them. • The tracking problem is solved both for targets attached to heliostat (local aiming) and for separated targets (global aiming). • The single-axis trackers are included as a limiting case.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Bonanos2021,

title = {Analysis of thermocline thermal energy storage systems with generic initial condition algebraic model},

author = {Aristides M. Bonanos and Evgeny Votyakov},

doi = {10.1016/J.SOLENER.2020.11.011},

issn = {0038-092X},

year  = {2021},

date = {2021-01-01},

journal = {Solar Energy},

volume = {213},

pages = {154--162},

publisher = {Pergamon},

abstract = {Thermal energy storage is key in making solar-thermal power plants more economically competitive compared to conventional plants. In this work, a new algebraic solution for thermocline thermal energy storage tanks, allowing for any initial temperature profile, is developed and presented. The model, called the Algebraic IC model, is successfully validated by comparing with experimental data and numerical solution of the governing partial differential equations. Additionally, the algebraic solution is extended to incorporate heat losses from the thermocline tank walls to the environment. The algebraic solution is significantly less computationally expensive than other one-dimensional models, since algebraic, rather than differential, equations are solved. An explicit formula for optimal fluid velocity is developed and validated through a parametric study of a thermocline tank. The effect of the dimensionless heat transfer coefficient is also investigated. Finally, the operation of thermocline tanks under multiple consecutive charging and discharging cycles is studied. The tank efficiency depends on the amount of thermocline allowed to exit during each cycle, and was found to decrease initially and subsequently reach steady state in less than 10 cycles.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Blanco2020,

title = {Updating the PSA sun position algorithm},

author = {Manuel J. Blanco and Kypros Milidonis and Aristides M. Bonanos},

doi = {10.1016/j.solener.2020.10.084},

issn = {0038092X},

year  = {2020},

date = {2020-12-01},

journal = {Solar Energy},

volume = {212},

pages = {339--341},

publisher = {Elsevier Ltd},

abstract = {The algorithm for computing the solar vector of (Blanco et al., 2001) is revisited to improve its accuracy in the period 2020–2050, a period for which the algorithm was not initially designed. The resulting improved algorithm achieves a 25% decrease in the average error of the angular deviation with respect to the true solar vector (from a mean error of 11.81–8.78 arcsec), while simultaneously decreasing the range of variation of the error.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Bonanos2020,

title = {Estimation of mean field reflectance in CST applications},

author = {Aristides M. Bonanos and Alaric C. Montenon and Manuel J. Blanco},

doi = {10.1016/j.solener.2020.08.073},

issn = {0038092X},

year  = {2020},

date = {2020-09-01},

journal = {Solar Energy},

volume = {208},

pages = {1031--1038},

publisher = {Elsevier Ltd},

abstract = {The efficient and productive operation of a Concentrating Solar Thermal (CST) plant depends upon knowledge of the mean reflectance of the solar collector field, as the levelized cost of electricity has a one-to-one ratio with reflector optical performance. Considering the size of such collector fields, a continuous detailed survey of the whole field is not a practical proposition. This paper presents a statistical approach to measuring mean field reflectance by sampling only a subset of the field reflectors. We find that three samples are sufficient for evaluating the mean reflectance of a single facet, and that the locations sampled within the facet do not impact the estimate of the mean. Further, for any collection of facets behaving as a cluster, again sampling three facets is sufficient to yield an estimate of the mean reflectance of the cluster. These sample numbers hold for an error of 2.5% at 95% confidence; different error or confidence intervals will affect the sample numbers required. The results are obtained from studying the behavior of both a heliostat and a linear Fresnel collector field. A blueprint for large CST collector fields is derived.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Grigoriev2020,

title = {Sun tracking by heliostats with arbitrary orientation of primary and secondary axes},

author = {Victor Grigoriev and Kypros Milidonis and Manuel J. Blanco},

doi = {10.1016/j.solener.2020.07.086},

issn = {0038092X},

year  = {2020},

date = {2020-09-01},

journal = {Solar Energy},

volume = {207},

pages = {1384--1389},

publisher = {Elsevier Ltd},

abstract = {The tracking of heliostats with arbitrary orientation of the primary and secondary axes is considered, and the explicit formulas are derived to find the tracking angles for a given position of the sun. It is shown that the inverse kinematics problem leads to a quadratic equation and has two solutions in general case. The solutions can be obtained in vector, matrix or quaternionic form. The advantages of the particular forms and possible applications are discussed. The corrections due to offset between tracking axes and mirror facets are also considered. The paper is accompanied with a Python library, which shows how to implement the tracking algorithms, and an interactive Jupyter notebook.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Tovbin2020,

title = {Effect of Inert Gas Vibrations in Bound States on the Equilibrium of a Vapor-Liquid System},

author = {Yu K. Tovbin and Evgeny Votyakov},

url = {https://link.springer.com/article/10.1134/S0036024420090290},

doi = {10.1134/S0036024420090290},

issn = {1531-863X},

year  = {2020},

date = {2020-09-01},

journal = {Russian Journal of Physical Chemistry A 2020 94:9},

volume = {94},

number = {9},

pages = {1952--1956},

publisher = {Springer},

abstract = {The effect the vibrational motion of inert gas atoms in the bound states at an arbitrary density of a vapor–liquid system has on the equilibrium concentration dependence of the chemical potential on density is considered for the first time. Both the potential energy of interaction between atoms and their vibrations in the bound states, starting from an isolated dimer to a dense phase, are considered. Calculations are made using the lattice gas model (LGM) for a one-dimensional fluid. Spatial atomic distributions are described in a quasi-chemical approximation. Local frequencies of atoms are calculated in a quasi-dimer model of vibrational motion. At the same time, the translational motion of atoms when they move to neighboring vacant cells are considered. The calculations are made in two versions of the theory: discrete and continuum. The latter reflects the motion of the center of mass inside the cells into which the entire volume is partitioned in the LGM. It is found that allowing for the vibrations of atoms in the bound states at a fixed density of the system shifts the chemical potential to lower values.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Votyakov2020,

title = {The Continuum Quasichemical Approximation in Vapor–Liquid Systems},

author = {Evgeny Votyakov and Yu K. Tovbin},

url = {https://link.springer.com/article/10.1134/S0036024420080324},

doi = {10.1134/S0036024420080324},

issn = {1531-863X},

year  = {2020},

date = {2020-08-01},

journal = {Russian Journal of Physical Chemistry A 2020 94:8},

volume = {94},

number = {8},

pages = {1732--1737},

publisher = {Springer},

abstract = {The continuum quasichemical approximation is used to improve the accuracy of describing molecular distributions in a vapor–liquid system. It considers displacements of the molecular center of mass from the center of a cell within the lattice gas model. It also allows for (as in its discrete variant) direct correlations of interacting molecules. The probability density of a molecule being inside the cell is used as a continuous function of its coordinate. An algorithm for solving a system of integral equations is developed with respect to the pair distribution function. The effect the continuum description of the particle distribution has on the concentration dependences of the main thermodynamic functions is investigated. The approach is shown to explain the concentration dependence of the parameter of effective lateral interaction.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Delise2020,

title = {Modeling the Total Ternary Phase Diagram of NaNO3–KNO3–NaNO2 Using the Binary Subsystems Data},

author = {T. Delise and A. C. Tizzoni and Evgeny Votyakov and Luca Turchetti and N. Corsaro and S. Sau and S. Licoccia},

url = {https://doi.org/10.1007/s10765-019-2577-2},

doi = {10.1007/s10765-019-2577-2},

issn = {15729567},

year  = {2020},

date = {2020-01-01},

journal = {International Journal of Thermophysics},

volume = {41},

number = {1},

pages = {1 -- 20},

publisher = {Springer},

abstract = {When designing a concentrating solar power (CSP) system, selection of a proper heat transfer fluid (HTF) material is a key, especially when employed in parabolic trough CSP plants. In particular, the use of low melting mixtures as an alternative to the widely commonly used “solar salt” can increase the CSP manageably and, as a result, several innovative nitrite/nitrate mixtures have been proposed. However, very few thermodynamics data are available for these compounds, especially regarding ternary compositions. One of the most interesting low freezing mixture is prepared with sodium and potassium nitrate together with sodium nitrite. The aim of this work is to investigate the thermodynamics properties of this ternary system, starting from its binary subunits, studying the phase diagram of this compound both experimentally and by a regular solution model. At this purpose, the literature phase diagrams of the binary subsystem were simulated in order to obtain the fitting parameters necessary for the employed semi-predictive tool. Then, the ternary system was modeled and the results showed very good agreement with the experimental points. It is quite interesting to note that both the theoretical and experimental results showed a low melting zone presenting greater sodium nitrate molar fractions with respect to sodium nitrite than previously reported in literature. This would lead to a decrease in the HTF price and an improvement regarding the fluid toxicity.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Wang2020,

title = {Verification of optical modelling of sunshape and surface slope error for concentrating solar power systems},

author = {Ye Wang and Daniel Potter and Charles Alexis Asselineau and Clotilde Corsi and Michael Wagner and Cyril Caliot and Benjamin Piaud and Manuel J. Blanco and Jin Soo Kim and John Pye},

doi = {10.1016/j.solener.2019.11.035},

issn = {0038092X},

year  = {2020},

date = {2020-01-01},

journal = {Solar Energy},

volume = {195},

pages = {461--474},

publisher = {Elsevier Ltd},

abstract = {Sunshape and reflector surface slope error distributions are significant elements in modelling the optical behaviour of a concentrating solar power system. Different optical modelling tools implement these elements with various approaches. Discrepancies can easily accumulate in simulations of a large optical system as a result of incorrect implementations. This study reviews and verifies the implementations of these two factors in six tools that are widely used for optical modelling in solar energy research: Tonatiuh, SolTrace, Tracer, Solstice, Heliosim and SolarPILOT. The review incorporates three rounds of tests. Firstly, basic tests examine each factor carefully in simplified on-axis reflector–target configurations (round ‘A'). Secondly, off-axis effects are introduced (round ‘B'). Thirdly, full heliostat field simulations are verified (round ‘C'). All of the test cases are simulated with each modelling tool, and results are compared. Discrepancies were observed due to approximations inherent in the cone optics (convolution) methods, incorrect implementation the of pillbox slope errors, different approaches to setting the circumsolar ratio for the Buie sunshape, and different approaches to the calculation of blocking and shading losses in some tools. All issues are discussed fully, and solutions to most issues were implemented within the scope of the present study. Some remaining issues are noted. The study highlights the importance of careful implementation of these aspects of optical modelling and contributes to an improvement in the quality of several widely-used tools.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Bonanos2019a,

title = {Heliostat surface shape characterization for accurate flux prediction},

author = {Aristides M. Bonanos and Marina Faka and Dante Abate and S. Hermon and Manuel J. Blanco},

doi = {10.1016/j.renene.2019.04.051},

issn = {18790682},

year  = {2019},

date = {2019-11-01},

journal = {Renewable Energy},

volume = {142},

pages = {30--40},

publisher = {Elsevier Ltd},

abstract = {The performance of a heliostat field is directly related to the optical quality of the mirror surfaces used to reflect solar radiation onto the receiver. In this paper, two methods are used to characterize the actual shape of the surface of a heliostat, using laser scanning and photogrammetry. The accuracy of each technique for the intended purpose is reported, while the methodology for analyzing the resulting point clouds is presented. The shape of the reflecting surface is reconstructed from the point clouds generated by each one of the methods used to characterize the actual shape of the heliostat surface. The Tonatiuh ray tracing program is used to compare the flux distributions of the heliostat obtained in this way, with the intended ideal parabolic shape of the heliostat. The flux distributions are also compared to optical images of the heliostat reflection on a plane target. Surface reconstruction from the photogrammetry point cloud results in a better agreement between the optical and simulated flux distributions on the target. Comparing results from the reconstructed surfaces and the ideal parabolic surface to optical images, a 20% improvement in prediction is achieved by using the photogrammetry point cloud as opposed to the ideal parabolic shape.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Bonanos2019,

title = {Engineering aspects and thermal performance of molten salt transfer lines in solar power applications},

author = {Aristides M. Bonanos and Marios C. Georgiou and Konstantinos G. Stokos and Costas N. Papanicolas},

doi = {10.1016/j.applthermaleng.2019.03.091},

issn = {13594311},

year  = {2019},

date = {2019-05-01},

journal = {Applied Thermal Engineering},

volume = {154},

pages = {294--301},

publisher = {Elsevier Ltd},

abstract = {Concentrating solar thermal power coupled with thermal energy storage is considered as one of the leading technologies to address the decarbonization of the energy sector. The use of molten solar salt (60–40% b.w. NaNO3-KNO3) as heat transfer fluid and thermal storage medium is the current commercial practice, with alternative salt mixtures being under evaluation for the next-generation higher-temperature systems. The main drawback of the molten salts is their high freezing temperature; active means are required for preheating of- and to prevent salt from freezing in- the transfer lines. In this article we present experiences from the PROTEAS facility, where heating tapes as opposed to heating cables are used. The thermal energy losses from the transfer lines are evaluated and compared to those predicted by a one-dimensional heat transfer analysis. Thermal losses between 43 and 100 W/m are found at operating temperatures from 300 to 500 °C. A joint optimization of the capital and operational expenditure for heating tapes and insulation is performed, leading to the optimal insulation thickness and installed heat tracing capacity. Increasing the installed heat tracing capacity with respect to the minimum required to overcome thermal losses, leads to a reduction of the preheating time and, therefore, a reduction in the overall operational expenses of the system. In some situations, this was found to also lead to a reduction in the necessary insulation thickness. Simulations indicate that if the optimal insulation was used, a decrease of 10 and 15% in thermal losses and O&M expenditures, respectively, could be achieved.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Blanco2019a,

title = {FluxTracer: A Ray Tracer Postprocessor to Assist in the Design and Optimization of Solar Concentrators and Receivers},

author = {Manuel J. Blanco and Marios Constantinou and Clotilde Corsi and Victor Grigoriev and Kypros Milidonis and Constantinos F. Panagiotou and Costas N. Papanicolas and John Pye and Evgeny Votyakov},

url = {https://github.com/solartherm},

doi = {10.1115/1.4042127},

issn = {15288986},

year  = {2019},

date = {2019-04-01},

journal = {Journal of Solar Energy Engineering, Transactions of the ASME},

volume = {141},

number = {2},

pages = {21015--1 -- 21015--9},

publisher = {American Society of Mechanical Engineers (ASME)},

abstract = {This paper presents FluxTracer, an advanced open source computer tool to assist in the analysis, design, and optimization of solar concentrators and receivers. FluxTracer is a postprocessor for Monte Carlo ray tracers used to simulate the optical behavior of solar concentrating systems. By postprocessing the rays generated by the ray tracer, FluxTracer can partition into volumetric pixels (voxels) a region of interest in three-dimensional (3D) space defined by the user and compute for each voxel the radiant power density of the concentrated solar radiation. Depending upon the set of rays provided by the ray tracer, it may be able to integrate the radiant power density in every voxel over time. The radiant energy density analysis described is just one of the analyses that FluxTracer can carry out on the set of rays generated by the ray tracer. This paper presents the main analyses that FluxTracer can provide. It also presents examples of how the information provided by FluxTracer can be used to assist in the analysis, design, and optimization of solar concentrators and receivers. FluxTracer is the first of a series of components of an open-source computational framework for the analysis, design, and optimization of solar concentrators and receiver, being developed by The Cyprus Institute (CyI) and the Australian National University (ANU).},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Blanco2018,

title = {FluxTracer: A 3D-Partitioning and Radiant Flux Computer Tool to Analyse the Optical Behaviour of Light Collection and Concentration Subsystems Using High Performance Computers},

author = {Manuel J. Blanco and Evgeny Votyakov and Chariton Christou and Costas N. Papanicolas and Clotilde Corsi and John Pye},

doi = {10.1115/ES2018-7415},

isbn = {9780791851418},

year  = {2018},

date = {2018-10-01},

journal = {ASME 2018 12th International Conference on Energy Sustainability, ES 2018, collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum},

publisher = {American Society of Mechanical Engineers Digital Collection},

abstract = {The light collection and concentration subsystem (LCCS) of any concentrating solar thermal (CST) system is composed of the surfaces that collect and concentrate the sunlight and of the input surfaces of the receivers, or receivers' envelopes, where the light is concentrated. For all commercial CST technologies the LCCS is, together with the power block, the subsystem that has more influence in the overall performance and cost. Thus, its optimization is critical to increase the costcompetitiveness of these systems. This optimization requires, in many cases, the optimization of the position, geometry and size of a very large number of solar collecting and concentrating surfaces as well as the optimization of the shape and size of the input surfaces of the receivers where the sunlight is concentrated. Because a full optimization requires the exploration of a configuration space with a very large number of dimensions, the traditional approach consist in making many initial assumptions to drastically reduce the number of dimensions of the configuration space to a handful, so that the optimization can be carried out using conventional high-end workstations in a matter of hours. However, to achieve relevant breakthroughs and to substantially increase the cost-competitiveness of CST systems a bolder approach is needed, where sophisticated design and analysis tools, engineered from the start to be used in High Performance Computers (HPC), will be combined with sophisticated optimization strategies targeted to explore and find optimal solutions in very high dimensional configuration spaces. This paper presents the first of a series of such design and analysis tools. The tool, call FluxTracer, partitions the threedimensional space in which the LCC subsystem under analysis is immersed into volumetric pixels (voxels) and computes the radiant energy flux that traverses each voxel as a function of time. It integrates the energy density in every voxel overtime, providing detailed information regarding how the radiant energy flows in space in a given LCC subsystem and in a given period of time. This information is the cornerstone of the highly sophisticated computational LCC subsystem optimization framework The Cyprus Institute (CYI) is developing, in collaboration with the Australian National University (ANU), targeted to be used in HPC's.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Milidonis2018,

title = {Effect of clocking on compressor noise generation},

author = {Kypros Milidonis and Bernhard Semlitsch and Tom Hynes},

url = {https://arc.aiaa.org/doi/abs/10.2514/1.J057256},

doi = {10.2514/1.J057256/ASSET/IMAGES/LARGE/FIGURE8.JPEG},

issn = {00011452},

year  = {2018},

date = {2018-09-01},

journal = {AIAA Journal},

volume = {56},

number = {11},

pages = {4225--4231},

publisher = {American Institute of Aeronautics and Astronautics Inc.},

abstract = {The effect of stator clocking on the acoustic noise-generation characteristics in an axial high-pressure compressor is analyzed. A realistic geometry with 1.5 stages is assessed using high-fidelity and low-order numerical methods for different clocking positions at approach operating conditions. The compressor efficiency and the acoustic noise emission are found to vary insignificantly between the simulated clocking configurations. Nonetheless, the pressure distribution is altered significantly, right upstream of the inlet guide vanes. Although the cut-on modes exhibit at least 10-dB-higher amplitudes, the cutoff modes contribute decisively to the wave pattern in the near field. An optimal acoustic liner design can expand on the differently evolving interference pattern of acoustic waves at discrete frequencies. The low-order model is found to predict the directionality of the acoustic waves, and the cut-on criteria for the individual modes is in excellent agreement with the high-fidelity simulations. However, the phase cannot be estimated due to the simplicity of the low-order formulation.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Igreja2018,

title = {Finite dimensional models of the hydraulic hammer effect and solar tower control},

author = {José M. Igreja and Costas Marakkos and João M. Lemos},

doi = {10.1016/j.jprocont.2017.10.002},

issn = {09591524},

year  = {2018},

date = {2018-05-01},

journal = {Journal of Process Control},

volume = {65},

pages = {78--83},

publisher = {Elsevier Ltd},

abstract = {The occurrence of traveling shock waves associated to the sudden opening or closing of a valve, known as the hammer effect, is important from the perspective of control design because it imposes an upper bound constraint on the maximum bandwidth achievable for the controlled system. This article addresses the problem of characterizing hydraulic hammer effect of the heating fluid in a solar power tower. The transfer function that relates the increments of the pressure inside the pipe and the fluid velocity is computed, as well as its poles and zeros. In this way, it is possible to obtain finite dimensional linear approximations for this transfer function with a prescribed complexity. As an application, the traveling waves of pressure and velocity of a fluid used for temperature control in a typical solar tower circuit are simulated.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Milidonis2018a,

title = {Film cooling effectiveness predictions in the region of the blade-endwall junction corner with injection assisted by the recirculating vortex flow},

author = {Kypros Milidonis and Demos P. Georgiou},

doi = {10.1504/PCFD.2018.096624},

issn = {17415233},

year  = {2018},

date = {2018-01-01},

journal = {Progress in Computational Fluid Dynamics},

volume = {18},

number = {6},

pages = {362--375},

publisher = {Inderscience Publishers},

abstract = {The region around the blade leading edge-endwall junction in inlet guide vanes (IGV) of gas turbines presents one of the most difficult hot spots to be cooled within the blade passage, largely due to the presence of strong three dimensional flows which displace the coolant away from the region before it can provide adequate cooling. The present study investigates via RANS-based simulation the film cooling effectiveness of a novel slot injection in which the coolant is ejected in such a way that its cooling effectiveness is assisted by the presence of the local three dimensional flows (especially the horseshoe vortex) that dominate the junction area. The computational predictions indicate that the proposed injection geometry provides a very effective cooling method for addressing the high heat transfer rate around the problematic region. The predicted three-dimensional flow topology and the associated endwall heat transfer are presented and discussed in order to elucidate the physical mechanisms that lead to the successful film cooling effectiveness of the proposed injection slot.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Milidonis2018b,

title = {The effect of steady intake distortion on fan MPT noise under sideline flight conditions},

author = {Kypros Milidonis and Tom Hynes and Martin Doherty and Howoong Namgoong},

url = {https://arc.aiaa.org/doi/abs/10.2514/6.2018-4188},

doi = {10.2514/6.2018-4188},

isbn = {9781624105609},

year  = {2018},

date = {2018-01-01},

journal = {2018 AIAA/CEAS Aeroacoustics Conference},

publisher = {American Institute of Aeronautics and Astronautics Inc, AIAA},

abstract = {One of the major challenges faced in the design of modern turbofan engines is the reduction of noise generation at operating conditions where the relative flow past the fan blades is supersonic. Under these conditions, the resulting noise signature is known as “Multiple Pure Tone” or “Buzz-saw” noise and it's an effect of both: (1)The small passage-to-passage aerodynamic deviations occurring due to blade manufacturing tolerances and fan rotor assembly mistuning, and (2), the inlet mean flow steady distortion imposed by the use of non-axisymmetric drooped intakes. Due to the complexity of the problem, modeling the buzz-saw noise generation and propagation in the intake is often performed by employing analytical and numerical prediction schemes, frequently resorting to assumptions that significantly deviate from the real underlying physics. To ease the modeling of the noise source and its spatial propagation characteristics, advanced computational fluid dynamics (CFD) is utilized in the current study in order to investigate the impact of the steady inlet flow distortion imposed by sideline flight conditions on buzz-saw noise generation and propagation. The test configuration adopted for the calculations is comprised of a full-annulus 22-bladed fan with individual blade stagger angle variation coupled with a realistic non-axisymmetric drooped intake. The results are compared to a second calculation employing the same configuration under static engine conditions and at the same speed. The calculations reveal that due to the different operating conditions, local variations do exist in the steady distortion which causes modifications on the modal propagation and radiation directivity. The major differences observed between the two cases are mainly confined to the top half of the intake.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Peruchena2018,

title = {High frequency generation of coupled GHI and DNI based on clustered Dynamic Paths},

author = {Carlos F. Peruchena and Miguel Larrañeta and Manuel J. Blanco and Ana Bernardos},

doi = {10.1016/j.solener.2017.11.024},

issn = {0038092X},

year  = {2018},

date = {2018-01-01},

journal = {Solar Energy},

volume = {159},

pages = {453--457},

publisher = {Elsevier Ltd},

abstract = {This Brief Note presents a general and efficient clustered-based methodology for the generation of high-frequency coupled global horizontal irradiance (GHI) and direct normal irradiance (DNI) series, based on the envelope clear sky and Dynamic Paths concepts. The procedure for generating 1-min synthetic irradiance data assumes that the effect of passing clouds on the fluctuations of both GHI and DNI can be dynamically reproduced using local variability patterns characterized by a 1-year ground measurements. This work presents for the first time synthetically generated 1-min GHI and DNI coupled datasets (156 months, from 1999 to 2011) generated from their corresponding low frequency series and local solar irradiance dynamics. The statistical parameters used for compare the measured and generated series perform well: mean absolute deviation is negligible, with averaged values of ∼0.3% and ∼0.2% for GHI and DNI, respectively. The KSI(%) values for DNI and GHI are lower than 100% in average. KSI(%) values of GHI series (in the range of 51.5–70.1% for averaged daily KSI(%) values at each month) are lower than the respective KSI(%) values of the DNI series (in the range of 75.0–110.8%). Finally, the generated 1-min solar irradiance series has the same autocorrelative structure as the observed, according to the similitude of their Ramp Rates.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Kampelis2017,

title = {Evaluation of the performance gap in industrial, residential & tertiary near-Zero energy buildings},

author = {N. Kampelis and K. Gobakis and V. Vagias and D. Kolokotsa and L. Standardi and D. Isidori and C. Cristalli and F. M. Montagnino and Filippo Paredes and P. Muratore and L. Venezia and Kyprianou Dracou and Alaric C. Montenon and A. Pyrgou and Theoni Karlessi and Mat Santamouris},

doi = {10.1016/j.enbuild.2017.03.057},

issn = {03787788},

year  = {2017},

date = {2017-08-01},

journal = {Energy and Buildings},

volume = {148},

pages = {58--73},

publisher = {Elsevier Ltd},

abstract = {Energy efficiency, advanced controls and renewable energy systems for operating industrial, residential and tertiary sector buildings designed to be Near-Zero Energy are investigated to explore the performance gap. The analysis involves a comparison of energy dynamic and quasi-dynamic models with data from smart monitoring systems, indoor and outdoor environment measurements, power consumption and production data. Specific issues and conclusions have been drawn as the basis for addressing the performance gap between energy efficiency prediction in the design phase and measurements' evaluation in operational phase.},

keywords = {Advanced Renewable Energy Systems, Sustainable Built Environment},

pubstate = {published},

tppubtype = {article}

}

@article{Igreja2017,

title = {The hydraulic hammer effect in solar tower fluid circuit temperature controller},

author = {José M. Igreja and Costas Marakkos and João M. Lemos},

doi = {10.1016/j.ifacol.2017.08.022},

issn = {24058963},

year  = {2017},

date = {2017-07-01},

journal = {IFAC-PapersOnLine},

volume = {50},

number = {1},

pages = {129--134},

publisher = {Elsevier B.V.},

abstract = {This article addresses the possible occurrence of hydraulic hammer effects in solar power towers and the limitations they impose on the response bandwidth of the control loop that governs the valve actuating on heating fluid flow. The partial differential equations that model the traveling waves associated to the hammer effect are solved with different methods. A finite dimensional approximation of the exact solution, by a transfer function with a finite number of poles is obtained. It is concluded that, for the speed of response of the temperature controller associated to the valve, there is no danger of inducing hydraulic hammer effects that can damage the equipment.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Bonanos2017,

title = {Physical modeling of thermo-compressor for desalination applications},

author = {Aristides M. Bonanos},

doi = {10.1016/j.desal.2017.03.004},

issn = {00119164},

year  = {2017},

date = {2017-06-01},

journal = {Desalination},

volume = {412},

pages = {13--19},

publisher = {Elsevier B.V.},

abstract = {Steam ejectors, or thermocompressors, are widely used in thermal desalination applications such as Multiple Effect Distillation to reclaim some of the energy discarded in the condensation of vapor from the last effect. Although several empirical models for the entrainment ratio as a metric of performance of the ejectors are available in the literature, large discrepancies are present in their predictions. In the present paper, a physical model for the performance of an ejector is developed, along with an investigation of its off-design performance.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Georgiou2017a,

title = {Experimental investigation of transitional natural convection in a cube using particle image Velocimetry Part II: Turbulence quantities and proper orthogonal decomposition},

author = {Marios D. Georgiou and Aristides M. Bonanos and John G. Georgiadis},

url = {http://asmedigitalcollection.asme.org/heattransfer/article-pdf/139/1/012503/6214289/ht_139_01_012503.pdf},

doi = {10.1115/1.4034167},

issn = {15288943},

year  = {2017},

date = {2017-01-01},

journal = {Journal of Heat Transfer},

volume = {139},

number = {1},

publisher = {American Society of Mechanical Engineers (ASME)},

abstract = {An experimental investigation of transitional natural convection in an air filled cube was conducted in this research. The characteristic dimension of the enclosure was H=0.35 m, and data were collected in the middle plane of the cavity. The Rayleigh number range examined was 5:0 × 107 ≤ Ra ≤ 3:4 × 108. In Part I, the authors presented the mean velocity profiles in the enclosure and conducted heat transfer measurements on the hot wall. An expression between Nu and Ra numbers was concluded and compared against other correlations available in literature. In the present work, the authors present a complete description of the flow in the enclosure by quantifying the low turbulence regime developed in the cavity. This was accomplished by estimating Reynolds stresses, turbulent kinetic energy, vorticity, and swirling strength. Proper orthogonal decomposition (POD) was employed to analyze the flow fields obtained from the experimental data and retain the most salient features of the flow field. This study attempts to close the gap of available experimental data in the literature and provide experimental benchmark data that can be used to validate CFD codes since the estimated error from particle image velocimetry (PIV) measurements is within 1-2%.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Blanco2017a,

title = {Introduction to concentrating solar thermal (CST) technologies},

author = {Manuel J. Blanco and S. Miller},

doi = {10.1016/B978-0-08-100516-3.00001-0},

isbn = {9780081005170},

year  = {2017},

date = {2017-01-01},

journal = {Advances in Concentrating Solar Thermal Research and Technology},

pages = {3--25},

publisher = {Woodhead Publishing},

abstract = {Concentrating solar thermal (CST) technologies provide promising and diverse opportunities to power the present and future needs of humankind. All solar energy systems are designed to maximise the advantages provided by the sun as an energy source and to minimise the disadvantages. CST technologies collect and concentrate radiation from the sun to transform it into high-temperature thermal energy. This thermal energy can later be used for a plethora of high-temperature thermal applications, such as heating and cooling, process heat, material treatments, electricity production, or chemical processes. This chapter provides a background to the sun as our most valuable energy source, the defining characteristics of CST technologies, and the need and limits associated with the concentration of sunlight. It presents the competing tendencies for the efficient conversion of direct solar radiation into useful thermal energy and the subsequent transformation into work by a heat engine and explains how this leads to the existence of an optimum in the overall light-to-work conversion efficiencies of a CST system in terms either of the operating temperature or the solar radiation concentration capabilities of the system. It also provides an overview of the four main commercially available solar concentrating technologies, along with the current state-of-the art of CST technologies for electricity and process heat generation, solar chemistry, and thermal energy storage, and an overview of the major research efforts around the world to increase the cost-competitiveness of CST technologies and ensure that they will play a major role in the necessary and urgent transition to a much more environmentally friendly world energy system. Finally, the chapter presents the overall concept of this book on advances in concentrating solar power research and technology, which aims to provide an overview beyond the state-of-the-art of CST technologies, with a focus on advanced CST concepts that are emerging as incremental or step-changes in CST technology.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Blanco2017,

title = {EU-SOLARIS: The European Infrastructure for Concentrated Solar Thermal and Solar Chemistry Technologies},

author = {Manuel J. Blanco and Th. I. Oikonomou and V. Drosou},

doi = {10.1016/j.proenv.2017.03.111},

issn = {18780296},

year  = {2017},

date = {2017-01-01},

journal = {Procedia Environmental Sciences},

volume = {38},

pages = {485--491},

publisher = {Elsevier BV},

abstract = {EU-SOLARIS project is a European project, co-funded by the 7th framework programme of the European Union. It is a Research Infrastructure (RI) initiative aimed to foster and promote the scientific and technological development of Concentrating Solar Thermal (CST) and Solar Chemistry technologies. EU-SOLARIS aims to create a new legal entity to explore and implement new and improved rules and procedures for the overall coordination and join exploitation of the main European RI for CST and Solar Chemistry technologies, in order to optimize RI development and Research and technology Development (R&D) coordination. It is expected to be the first of its kind, where industrial needs and private funding will play a significant role. The success of the EU-SOLARIS initiative will be the establishment of a new governance body, aided by sustainable financial models for this unique European large and distributed research infrastructure in the CST and Solar Chemistry fields. EU-SOLARIS is expected to be an important tool in consolidating Europe's leadership in these areas. This will be accomplished by linking the research community and the industry involved in the CST sector and providing them the research infrastructures needed to innovate and advance the state of the art of CST and Solar Chemistry technologies. EU-SOLARIS is also expected to increase the efficient use of the economic and human resources required throughout the European research context and to provide efficient resource management to complement research and to avoid unnecessary technological duplication and repetition. This article presents the vision, objectives, activities and current status of the EU-SOLARIS project and discusses the most important - expected to be achieved - outcomes of the project, which is currently at its last year of its preparatory phase.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Bonanos2016,

title = {Sensitivity analysis for thermocline thermal storage tank design},

author = {Aristides M. Bonanos and Evgeny Votyakov},

doi = {10.1016/j.renene.2016.07.052},

issn = {18790682},

year  = {2016},

date = {2016-12-01},

journal = {Renewable Energy},

volume = {99},

pages = {764--771},

publisher = {Elsevier Ltd},

abstract = {Concentrated solar power coupled with thermal energy storage is a promising approach for providing the world with clean, renewable, sustainable and cost-competitive power on a large scale. Thermocline thermal energy storage has been proposed as an efficient and cost-competitive alternative to the traditional two-tank design. The thermocline thickness is directly linked to the efficiency of the storage tank. Sensitivity analysis is thus applied to a model of the thermocline thickness to identify the parameters that influence it the most. Results indicate that the tank height along with the thermophysical properties of the solid filler material influence the tank efficiency the most, with fluid properties and having a secondary effect.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Georgiou2016,

title = {A transient model for forward and parallel feed MED},

author = {Marios C. Georgiou and Aristides M. Bonanos},

url = {https://www-tandfonline-com.proxy2.library.illinois.edu/doi/abs/10.1080/19443994.2016.1180480},

doi = {10.1080/19443994.2016.1180480},

issn = {19443986},

year  = {2016},

date = {2016-10-01},

journal = {Desalination and Water Treatment},

volume = {57},

number = {48-49},

pages = {23119--23131},

publisher = {Taylor and Francis Inc.},

abstract = {The aim of this paper is to investigate the performance of a multiple effect distillation (MED) unit potentially coupled to a concentrated solar power plant and validate the results with the predictions of a dynamic model that was developed for this purpose. A small-scale (10 kWthermal) four effect distillation system was designed and built to demonstrate proof of principle of the concentrating solar power–desalinating sea water system integration. In order to fully characterize this small-scale MED unit, an understanding of the performance for steady state and transient conditions is required. Initially experiments were performed in a steady state situation, various parameters were examined and the experimental findings have already been published. After the initial experimental findings of the steady state operation, the performance of this unit was also investigated for transient conditions. The experimental procedure followed was identical as in the steady state conditions, with the main difference being the variation in the heat input supply to the system as a function of time. For the present study, the heat input supplied to the unit varied between 5 and 10 kWthermal. At the same time, a dynamic model was also developed in order to predict the performance of this unit in consecutive time steps of operation. The performance was calculated in terms of performance ratio (the ratio of the distillate product flow rate to the feeding steam flow rate) and the model results were validated against the experimental findings. The results showed that there is a really good match between the experimental data and the predicted ones from the model.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Navarro2016,

title = {Review and validation of Solar Thermal Electricity potential methodologies},

author = {Ana A. Navarro and Lourdes Ramírez and Pablo Domínguez and Manuel J. Blanco and Jesus Polo and Eduardo Zarza},

doi = {10.1016/j.enconman.2016.07.070},

issn = {01968904},

year  = {2016},

date = {2016-10-01},

journal = {Energy Conversion and Management},

volume = {126},

pages = {42--50},

publisher = {Elsevier Ltd},

abstract = {With the strong dependence of national economies on energy, interest in solar energy potential assessments is increasing in countries with high solar radiation levels. This article reviews four methodologies proposed in the literature by four different organizations (IDAE, Greenpeace, NREL, and DLR) and proposes a new one (LRS) for assessing the potential of Solar Thermal Electricity (STE) generation in a given country. Derived from these five methodologies, nine cases are studied (IDAE, GP2, NREL1, NREL3, DLR2, DLR2′, LRS1, LRS2, and LRS3). In this study, we followed a two-step STE potential assessment procedure. In the first step, suitable areas for locating STE plants in the country are identified. In the second step, STE plants are assumed to be built and operated in the suitable areas selected in the first step, and the annual electricity generated by these hypothetical plants is estimated. To compare the assessed methodologies, all cases have been applied to the same test country: Spain. Because a relatively large number of commercial STE plants are in operation in Spain, the location of these commercial plants was used to define a simple but effective validation test. A validation process is proposed for the IN-OUT decision based on the buffers containing each existing STE plant. Inside each buffer, a mix of suitable and unsuitable pixels is often included. Thus, the process starts with the decision whether a plant could be considered “IN” the suitable area or not. After the evaluation of the percentage of pixels considered as suitable inside the buffer, and comparing with only the power block pixel location, the second option was selected since it provides good results and simplifies any further treatment. The validation process also considers a minimum of near 90% of the STE plants “IN” suitable areas in order to consider a specific case valid. This means that if a case leaves out more than 10% of the real STE plants, it was considered far from reality and rejected. Cases IDAE, NREL3, DLR2, and the new LRS3 have been validated using the described validation procedure and the last three have very close results with similar levels; this is an important outcome that aims to compare potential assessments performed in different countries by different institutions.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Grigoriev2016,

title = {Fourier sampling of sun path for applications in solar energy},

author = {Victor Grigoriev and Clotilde Corsi and Manuel J. Blanco},

url = {https://aip.scitation.org/doi/abs/10.1063/1.4949032},

doi = {10.1063/1.4949032},

issn = {0094-243X},

year  = {2016},

date = {2016-05-01},

journal = {AIP Conference Proceedings},

volume = {1734},

number = {1},

pages = {020008},

publisher = {AIP Publishing LLCAIP Publishing},

abstract = {A systematic approach is presented for the sampling and interpolation over sun path. The annual sun path is described in terms of the ecliptic longitude and hour angle so that all possible position...},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Georgiou2016a,

title = {Evaluation of a solar powered distillation unit as a mitigation to water scarcity and climate change in Cyprus},

author = {Marios C. Georgiou and Aristides M. Bonanos and John G. Georgiadis},

url = {https://www-tandfonline-com.proxy2.library.illinois.edu/doi/abs/10.1080/19443994.2014.989637},

doi = {10.1080/19443994.2014.989637},

issn = {19443986},

year  = {2016},

date = {2016-01-01},

journal = {Desalination and Water Treatment},

volume = {57},

number = {5},

pages = {2325--2335},

publisher = {Taylor and Francis Inc.},

abstract = {Cyprus, an island facing water scarcity periods throughout its history, has to cope with even more intense periods due to climate change as it is predicted by several climate models. The aim of the present study is to evaluate the performance of a single-effect distillation unit and the potential of its integration with a concentrated solar power system as a mitigation technique to the water scarcity. Specifically, a single-effect distillation unit for seawater desalination was developed and its performance in terms of performance ratio (PR) (ratio of distillate product and steam fed to the unit) was experimentally investigated. The main parameters examined were the thermal input power, and the temperature and flow rate of the inlet seawater. For several seawater flow rates, three different initial heat loads were used (Tst,1, Tst,2, Tst,3). Experiments were repeated for two seawater inlet temperatures, Tsw1, Tsw2. A one-dimensional model based on conservation of mass and energy was developed to predict the performance of the device. The results showed that lower heat input load results to a higher value of the PR of the unit and also under constant heat load, a higher temperature of the seawater lead to higher distillate product. The developed model adequately captured the behavior of the device. Thus, it is concluded that such a unit should be expanded into a multiple-effect unit and also implemented with a concentrated solar power system as a mitigation technique to the water scarcity of the island.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Votyakov2015,

title = {Algebraic model for thermocline thermal storage tank with filler material},

author = {Evgeny Votyakov and Aristides M. Bonanos},

doi = {10.1016/j.solener.2015.10.047},

issn = {0038092X},

year  = {2015},

date = {2015-12-01},

journal = {Solar Energy},

volume = {122},

pages = {1154--1157},

publisher = {Elsevier Ltd},

abstract = {A recent perturbation model (Votyakov and Bonanos, 2014) is solved with an algebraic approximation. Results are in agreement with independent numerical results of Yang and Garimella (2010). The algebraic model reveals several scaling ratios as well as a non-monotonic behavior of the thermocline thickness as a function of fluid Reynolds number.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Kakoniti2015,

title = {The role of materials selection in the urban heat island effect in dry mid-latitude climates},

author = {Androula Kakoniti and Gregoria Georgiou and Costas Marakkos and Prashant Kumar and Marina Neophytou},

url = {https://link.springer.com/article/10.1007/s10652-015-9426-z},

doi = {10.1007/S10652-015-9426-Z},

issn = {1573-1510},

year  = {2015},

date = {2015-09-01},

journal = {Environmental Fluid Mechanics 2015 16:2},

volume = {16},

number = {2},

pages = {347--371},

publisher = {Springer},

abstract = {This work investigates the role of materials selected for different urban surfaces (e.g. on building walls, roofs and pavements) in the intensity of the urban heat island (UHI) phenomenon. Three archetypal street-canyon geometries are considered, reflecting two-dimensional canyon arrays with frontal packing densities ($łambda$f) of 0.5, 0.25 and 0.125 under direct solar radiation and ground heating. The impact of radiative heat transfer in the urban environment is examined for each of the different built packing densities. A number of extreme heat scenarios were modelled in order to mimic conditions often found at low- to mid-latitudes dry climates. The investigation involved a suite of different computational fluid dynamics (CFD) simulations using the Reynolds-Averaged Navier–Stokes equations for mass and momentum coupled with the energy equation as well as using the standard k-$epsilon$ turbulence model. Results indicate that a higher rate of ventilation within the street canyon is observed in areas with sparser built packing density. However, such higher ventilation rates were not necessarily found to be linked with lower temperatures within the canyon; this is because such sparser geometries are associated with higher heat transfer from the wider surfaces of road material under the condition of direct solar radiation and ground heating. Sparser canyon arrays corresponding to wider asphalt street roads in particular, have been found to yield substantially higher air temperatures. Additional simulations indicated that replacing asphalt road surfaces in streets with concrete roads (of different albedo or emissivity characteristics) can lead up to a $sim$5 °C reduction in the canyon air temperature in dry climates. It is finally concluded that an optimized selection of materials in the urban infrastructure design can lead to a more effective mitigation of the UHI phenomenon than the optimisation of the built packing density.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Georgiou2015,

title = {Experimental evaluation of a multiple-effect distillation unit in low seawater flow conditions},

author = {Marios C. Georgiou and Aristides M. Bonanos and John G. Georgiadis},

url = {https://www-tandfonline-com.proxy2.library.illinois.edu/doi/abs/10.1080/19443994.2014.940638},

doi = {10.1080/19443994.2014.940638},

issn = {19443986},

year  = {2015},

date = {2015-09-01},

journal = {Desalination and Water Treatment},

volume = {55},

number = {12},

pages = {3267--3276},

publisher = {Taylor and Francis Inc.},

abstract = {Abstract: In this work, we evaluate experimentally the performance of a multiple-effect distillation (MED) unit in low seawater flow conditions and the potential of its integration with a concentrated solar power system. The innovation of this MED unit is the introduction of a flow distributor within the parallel plates of the falling film heat exchanger, designed to improve the system performance and efficiency under low seawater flow conditions. The main parameters examined were the thermal input power and the flow rate of the inlet seawater to each effect and the inlet seawater temperature of the single unit. Furthermore, the experimental results were compared with a control volume energy conservation model. The results showed that lower heat input load results to a higher value of the performance ratio (PR) of the unit and also under constant heat load, a higher temperature of the seawater lead to higher distillate product for the single effect unit. As the number of effects is increased the PR of the unit also increases approximately by 0.7 per effect. This maximum value for each effect is always observed in a constant ratio of seawater to steam flow rate.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Kakoniti2015a,

title = {The effect of urban design parameters on the local microclimate},

author = {Androula Kakoniti and Gregoria Georgiou and Costas Marakkos and Marina Neophytou},

url = {https://aip.scitation.org/doi/abs/10.1063/1.4906712},

doi = {10.1063/1.4906712},

issn = {0094-243X},

year  = {2015},

date = {2015-02-01},

journal = {AIP Conference Proceedings},

volume = {1642},

number = {1},

pages = {429},

publisher = {American Institute of PhysicsAIP},

abstract = {Two-dimensional steady-state simulations have been performed using the standard k-e turbulence model coupled with the heat transfer models available in the CFD software FLUENT 6.1, in order to exam...},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Papanicolas2015,

title = {Design, construction and monitoring of a near-zero energy laboratory building in Cyprus},

author = {Costas N. Papanicolas and M. A. Lange and Nestor Fylaktos and Alaric C. Montenon and G. Kalouris and N. Fintikakis and M. Fintikaki and D. Kolokotsa and K. Tsirbas and C. Pavlou and K. Vasilakopoulou and Mat Santamouris},

url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926517338&doi=10.1080%2F17512549.2015.1014837&partnerID=40&md5=0d7c6d715dde1148265ad696d74e5ac6},

doi = {10.1080/17512549.2015.1014837},

issn = {17562201},

year  = {2015},

date = {2015-01-01},

urldate = {2015-01-01},

journal = {Advances in Building Energy Research},

volume = {9},

number = {1},

pages = {140--150},

publisher = {Taylor and Francis Ltd.},

address = {The Cyprus Institute, 20 Constantinou Kavafi Street, Nicosia, 2121, Cyprus},

abstract = {The paper presents the architectural, engineering and energy design of a laboratory building located in Cyprus. The building is designed to meet near-zero energy consumption criteria using advanced energy conservation measures, smart energy management and solar thermal and photovoltaic systems to cover the remaining energy load. The energy conservation techniques used result in reduced energy consumption of the building by almost 70% compared with a conventional building, while almost 27% of the remaining heating-, cooling- and lighting load is covered by photovoltaics. A concentrating solar thermal system for cooling and heating is being installed to cover the remainder of the load.},

keywords = {Advanced Renewable Energy Systems, Sustainable Built Environment},

pubstate = {published},

tppubtype = {article}

}

@article{Votyakov2014,

title = {A perturbation model for stratified thermal energy storage tanks},

author = {Evgeny Votyakov and Aristides M. Bonanos},

doi = {10.1016/j.ijheatmasstransfer.2014.03.071},

issn = {00179310},

year  = {2014},

date = {2014-08-01},

journal = {International Journal of Heat and Mass Transfer},

volume = {75},

pages = {218--223},

publisher = {Elsevier Ltd},

abstract = {A single phase perturbation model has been developed for the characterization of the behavior of packed-bed thermocline thermal energy storage tanks, derived from the one-dimensional two-phase energy equations. The non-dimensional parameters governing the problem have been identified and separated into two groups, those related to the fluid and solid-filler material thermo-physical properties ($beta$,$gamma$), and those relating to the process flow (Péclet and Biot numbers). A series expansion solution for the perturbation model is derived. The new perturbation model is an improvement over the current one-phase models as it more accurately captures the effect of the diffusion term, and allows for a direct comparison with the two-phase model. textcopyright 2014 Elsevier B.V. All rights reserved.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Georgiou2013,

title = {Optical evaluation of heliostat mirrors using caustics},

author = {Marios D. Georgiou and Aristides M. Bonanos and John G. Georgiadis},

url = {http://aip.scitation.org/doi/10.1063/1.4826195},

doi = {10.1063/1.4826195},

issn = {19417012},

year  = {2013},

date = {2013-09-01},

journal = {Journal of Renewable and Sustainable Energy},

volume = {5},

number = {5},

pages = {053139--1 053139--12},

publisher = {American Institute of PhysicsAIP},

abstract = {Solar thermal power generation is based on the concept of concentrating solar radiation to provide high temperature heat for electricity generation via conventional power cycles. The high relative cost of optical subsystems necessitates a careful study of their components. Solar collector fields are typically modeled by ray-tracing or convolution methods; however, no general method is available for engineering analysis. We propose the use of caustics to predict the image of the sun reflected by an arbitrary mirror of focal length F and aperture a on a target. The mirror surface is described parametrically by a quadric and placed at a distance L from the target on a heliostat. The method of caustics was validated against SolTRACE, a ray-tracing code developed by U.S. National Renewable Energy Laboratories. We show that there is a value of a F which depends on a L, for which the incident average energy flux to the target reaches a maximum. The method of caustics allows the efficient computation of the image on an arbitrary target surface and obviates many of the difficulties with ray-tracing methods. textcopyright 2013 AIP Publishing LLC.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Georgiou2013a,

title = {Evaluation of a multiple-effect distillation unit under partial load operating conditions},

author = {Marios C. Georgiou and Aristides M. Bonanos and John G. Georgiadis and Y Al-Assaf and P Demokritou and A Poullikkas and C Sourkounis},

url = {https://downloads.hindawi.com/archive/2013/482743.pdf},

doi = {10.1155/2013/482743},

year  = {2013},

date = {2013-01-01},

journal = {downloads.hindawi.com},

volume = {2013},

publisher = {Hindawi Publishing Corporation},

abstract = {The design of a multiple-effect distillation (MED) system is presented, and the results for partial load operation of a single-effect distillation unit are presented. The MED is designed to be driven by solar energy, and thus the dynamic performance and partial load operation production are of interest. Two operating modes are considered in the analysis, with and without the use of a flow distributor. Various tests were performed varying the heating steam flow rate and the intake seawater flow rate. Results are presented as a function of the performance ratio, representing the amount of distillate produced per unit mass of steam input. Results indicate that a higher performance is obtained with the use of the flow distributor.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Bonanos2012,

title = {Error analysis for concentrated solar collectors},

author = {Aristides M. Bonanos},

url = {http://aip.scitation.org/doi/10.1063/1.4768546},

doi = {10.1063/1.4768546},

issn = {19417012},

year  = {2012},

date = {2012-11-01},

journal = {Journal of Renewable and Sustainable Energy},

volume = {4},

number = {6},

pages = {063125},

publisher = {American Institute of PhysicsAIP},

abstract = {Error sources introduced into mirror tracking systems, arising from component limitations, construction and placement of the reflectors, and the discrete motion of the tracking system itself, are examined. The main mechanisms contributing to these sources are identified and modeled. The effect of these optical and geometrical errors is numerically simulated using a ray-tracing code and their relative significance is assessed. textcopyright 2012 American Institute of Physics.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Ghobeity2011,

title = {Optimal time-invariant operation of a power and water cogeneration solar-thermal plant},

author = {Amin Ghobeity and Corey J. Noone and Costas N. Papanicolas and Alexander Mitsos},

doi = {10.1016/j.solener.2011.06.023},

issn = {0038092X},

year  = {2011},

date = {2011-09-01},

journal = {Solar Energy},

volume = {85},

number = {9},

pages = {2295--2320},

publisher = {Pergamon},

abstract = {Conceptual design, system-level models, and optimization of operation are presented for a cogeneration solar-thermal plant. The solar-thermal energy collected and concentrated in a salt pond is used in a regenerative Rankine steam cycle with an extraction turbine to produce electricity and process steam. The desalination system is based on reverse osmosis (RO) and multi-effect distillation (MED). An equation-oriented modeling environment is used for the development of time-dependent system-level models required for optimization of the plant. A meteorological radiation model is used to estimate the hourly distribution of beam radiation as a function of time (day and hour), location, and local weather (mainly visibility and humidity). A recently developed model is used to estimate the field efficiency, including projection losses and shading/blocking for a given heliostat layout. Time-invariant optimal operating conditions are presented for a summer day, considering Cyprus as a case study. Seawater desalination processes, RO and MED, are modeled by adapting and extending models from the literature. A control-volume model is developed for the steam cycle based on the first and second law, with given isentropic efficiencies, turbine leaks, and a detailed model for thermodynamic properties of steam/water. This model is validated and allows for optimization over a wide range of operating conditions, e.g., various extraction pressures. The optimization problem is formulated as a nonlinear program (NLP) with dynamics embedded and a heuristic global optimization approach is used. The sequential method of optimization is used, decoupling the simulation from the optimization. The results show that for the plant size considered (4MWe equivalent nominal capacity) and the MED design chosen based on the literature and industry practice, RO is preferred over MED from an energy point of view. In addition, under the current feed-in tariff (FiT) and water prices in Cyprus, extracting steam for MED is not recommended. In contrast, if current market prices for electricity and water in Cyprus are used, i.e., FiT is neglected, with a typical steam cycle design, extracting steam for MED at low pressures yields maximum income. A new process configuration is presented based on the findings from the case studies, resulting in significantly higher income and exergetic efficiencies. textcopyright 2011 Elsevier Ltd.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{McKnight2011,

title = {Analysis and design of a multi-effect desalination system with thermal vapor compression and harvested heat addition},

author = {Andrea Vozar McKnight and Marios C. Georgiou and Myunghoon Seong and John G. Georgiadis},

url = {https://doi.org/10.5004/dwt.2011.2382},

doi = {10.5004/dwt.2011.2382},

issn = {19443986},

year  = {2011},

date = {2011-07-01},

journal = {Desalination and Water Treatment},

volume = {31},

number = {1-3},

pages = {339--346},

publisher = {Taylor & Francis},

abstract = {The design and optimization of a concentrated solar power-desalination of seawater (CSP-DSW) plant is based on the accurate characterization and better integration of sub-components, such as the multiple effect distillation (MED). We set out to design and fabricate two pilot MED systems that consist of high performing components and involve a high degree of thermal integration with the rest of the system. An MED system with a series of thermal vapor compressors (TVCs) driven by heat harvested from the thermal storage subsystem of the CSP-DSW is proposed. An algorithm is presented which optimizes the gain output ratio (GOR) by varying of the number and entrainment ratio of TVCs. The use of modular parallel plate falling film heat exchangers and overall process thermal management increase the flexibility and overall efficiency of MED. Experience with the design and fabrication of a transparent single-effect experimental MED aimed to quantify the performance of the parallel plate falling film heat exchanger and to allow visualization of permeate vapor is discussed. A 10 kWt four-effect MED design is also described for use in a proof-of-principle CSP-DSW study to be performed at the Cyprus Institute. textcopyright 2011 Desalination Publications. All rights reserved.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Slocum2011,

title = {Concentrated solar power on demand},

author = {Alexander H. Slocum and Daniel S. Codd and Jacopo Buongiorno and Charles Forsberg and Thomas McKrell and Jean Christophe Nave and Costas N. Papanicolas and Amin Ghobeity and Corey J. Noone and Stefano Passerini and Folkers Rojas and Alexander Mitsos},

doi = {10.1016/j.solener.2011.04.010},

issn = {0038092X},

year  = {2011},

date = {2011-07-01},

journal = {Solar Energy},

volume = {85},

number = {7},

pages = {1519--1529},

publisher = {Pergamon},

abstract = {A concentrating solar power system is presented which uses hillside mounted heliostats to direct sunlight into a volumetric absorption molten salt receiver with integral storage. The concentrated sunlight penetrates and is absorbed by molten salt in the receiver through a depth of 4-5. m, making the system insensitive to the passage of clouds. The receiver volume also acts as the thermal storage volume eliminating the need for secondary hot and cold salt storage tanks. A small aperture and refractory-lined domed roof reduce losses to the environment and reflect thermal radiation back into the pond. Hot salt is pumped from the top of the tank through a steam generator and then returned to the bottom of the tank. An insulated barrier plate is positioned within the tank to provide a physical and thermal barrier between the thermally stratified layers, maintaining hot and cold salt volumes required for continuous operation. As a result, high temperature thermal energy can be provided 24/7 or at any desired time.The amount of storage required depends on local needs and economic conditions. About 2500m3 of nitrate salt is needed to operate a 4MWe steam turbine 24/7 (7h sunshine, 17h storage), and with modest heliostat field oversizing to accumulate energy, the system could operate for an additional 24h (1 cloudy day). Alternatively, this same storage volume can supply a 50MWe turbine for 3.25h without additional solar input. Cosine effect losses associated with hillside heliostats beaming light downwards to the receiver are offset by the elimination of a tower and separate hot and cold storage tanks and their associated pumping systems. Reduced system complexity also reduces variable costs. Using the NREL Solar Advisor program, the system is estimated to realize cost-competitive levelized production costs of electricity. textcopyright 2011 Elsevier Ltd.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}

@article{Noone2011,

title = {Site selection for hillside central receiver solar thermal plants},

author = {Corey J. Noone and Amin Ghobeity and Alexander H. Slocum and George Tzamtzis and Alexander Mitsos},

doi = {10.1016/j.solener.2011.01.017},

issn = {0038092X},

year  = {2011},

date = {2011-05-01},

journal = {Solar Energy},

volume = {85},

number = {5},

pages = {839--848},

publisher = {Pergamon},

abstract = {In this article, a new tool is introduced for the purpose of locating sites in hillside terrain for central receiver solar thermal plants. Provided elevation data at a sufficient resolution, the tool is capable of evaluating the efficiency of a heliostat field at any site location. The tool also locates suitable sites based on efficiency and average annual normal insolation. The field efficiency, or ratio of radiation incident to the receiver to direct normal solar radiation, is maximized as a result of factors including projection losses and interference between heliostats, known respectively as cosine efficiency, shading, and blocking. By iteratively defining the receiver location and evaluating the corresponding site efficiency by sampling elevation data points from within the defined heliostat field boundary, efficiency can be mapped as a function of the receiver location. The case studies presented illustrate the use of the tool for two field configurations, both with ground-level receivers and hillside heliostat layouts. While both configurations provide acceptable efficiencies, results from case studies show that optimal sites for ground-level receivers are ones in which the receiver is at a higher elevation than the heliostat field. This result is intuitive from the perspective of minimizing cosine losses but is nevertheless a novel configuration. textcopyright 2011 Elsevier Ltd.},

keywords = {Advanced Renewable Energy Systems},

pubstate = {published},

tppubtype = {article}

}