Concentrated Solar Power

Desalination plays critical role in filling the gap between fresh water demand and availability in water scarce Sultanate of Oman since 1976. Installed desalination capacity in the country has almost increased by 60 times that in 1976 with increasing fresh water demand. Even though desalination share in meeting the fresh water demand is increasing, 80-85% of fresh water demand today is still satisfied with ground water. This is leading to increased soil salinity in recent years affecting the crop production. All the planned and installed desalination plants in the country use conventional fuels for their operation. None of the plant is based on any form of renewable energy source. Consumption of fossil fuels for the operation of plants is increasing at an average rate of 3-5% affecting the net export for the country. Sultanate of Oman is considered to be one of the most suitable destinations for solar energy applications and can play a vital and sustainable role in meeting the gap b...

(english below) Η αντλησιοταμίευση, μια μέθοδος αποθήκευσης ηλεκτρικής ενέργειας σε δυναμική ενέργεια του νερού για υδροηλεκτρική χρήση, έχει αρχίσει να συζητείται πολύ τον τελευταίο καιρό. Πρόκειται για αποθήκευση ηλεκτρικής ενέργειας σε βαρυτική δυναμική ενέργεια του νερού μέσω άντλησής του από ταμιευτήρα χαμηλής στάθμης σε ταμιευτήρα υψηλότερης στάθμης. Η αντλησιοταμίευση μπορεί να συντελέσει στην αυξημένη διείσδυση ενέργειας παραγόμενης από μεταβλητές ΑΠΕ (κυρίως αιολικά, φωτοβολταικά) στο δίκτυο καθώς έτσι αποθηκεύεται τυχόν περίσσεια της ηλεκτρικής ενέργειας που αυτά παράγουν και μπορεί να παραχθεί ηλεκτρική ενέργεια όποτε η ζήτηση είναι υψηλή. Όμως εν όψει των-αναπόφευκτων ως ένα βαθμό-επιπτώσεων της κλιματικής αλλαγής που ειδικά στην Ελλάδα αναμένεται να είναι πολύ έντονες ποιές εκδοχές αντλησιοταμίευσης είναι καταλληλότερες; Ποιές εναλλακτικές υπάρχουν τόσο όσον αφορά νέες μορφές και παραλλαγές αντλησιοταμίευσης και γενικά αποθήκευσης ηλεκτρικής ενέργειας όσο και γενικότερα νέες μεθόδους για την ευελιξία του δικτύου; Ποιός ο πιθανός ρόλος για τις σταθερές ΑΠΕ; Ποιές οι γενικότερες εξελίξεις της ενεργειακής μετάβασης αλλά και του τομέα ορυκτών καυσίμων κι ειδικότερα του φυσικού αερίου; Πως επηρρεάζονται τα κριτήρια επιλογών από την ανάγκη αντιμετώπισης της επίσημα πλέον πολλαπλής παγκόσμιας περιβαλλοντικής κρίσης (κλιματική κρίση, απώλεια βιοποικιλότητας, μόλυνση από πλαστικά και μικροπλαστικά); Αυτά είναι τα ερωτήματα που απασχολούν το παρόν μέσα από μια ανασκόπηση πολλών τεχνολογικών εφαρμογών και περιβαλλοντικών θεμάτων. Το τελικό συμπέρασμα: ο σχεδιασμός συστημάτων με πολύ ακριβές υποδομές με αναμενόμενη διάρκεια ζωής πολλών δεκαετιών πρέπει να έχει μελετηθεί για τη βιωσιμότητά τους από το πρώτο βήμα ως το τελευταίο, πολλές δεκαετίες αργότερα, και να έχουν ληφθεί υπόψιν οι προβλέψεις για την εξέλιξη της κλιματικής αλλαγής καθώς και πολλές αβεβαιότητες. Η επίτευξη της μείωσης των εκπομπών άνθρακα μόνο δεν αρκεί, απαιτούνται πλέον και κλιματικά προσαρμοσμένα πλάνα για να γίνουν εφικτά κλιματικά ανθεκτικά συστήματα. Επιπλέον αυτών το πρόβλημα της ταχύτατης εξαφάνισης βιοποικιλότητας υποχρεώνει σε αντίστοιχα αυξημένη πρόνοια βάσει και των νέων πολιτικών, κανονισμών κι οδηγιών.

Pumped hydro storage, modern alternatives, energy transition, climate adaptation and the global environmental crisis

Abstract: 
Pumped hydro storage, a method of storing electricity in dynamic energy of water for hydroelectric use, has started to be discussed a lot lately. Pumped storage functions by storing electricity in gravitational dynamic energy of water through pumping it from a low level reservoir to a higher level one. Pumped storage can contribute to the increased penetration of energy produced by variable RES (mainly wind, photovoltaic) in the electrical grid as it stores the excess electricity that they produce and can generate electricity back whenever the demand is high. But in view of the inevitable  - to some extent - consequences of climate change that especially in Greece are expected to be very intense, which versions of pumped storage are more appropriate? Which are the alternatives either as new forms and variants of pumped storage and electricity storage in general, either as new methods for grid flexibility? Which is a possible role for steady RES? How is the evolution regarding the energy transition generally advancing, especially the evolution in the fossil fuel sector, and in particular natural gas? How are the selection criteria affected by the need to tackle the multiple global environmental crisis (climate crisis, biodiversity loss, plastic and microplastic pollution) that is officially declared? These are the questions that are discussed in this work through a review of many technological applications and environmental issues.
The conclusion: designing of systems that consist of very expensive infrastructure with a life expectancy of many decades must have been studied for their viability from the first step to the last, many decades later, and the predictions for climate change consequences must have been taken into account as well as many uncertainties. Achieving a reduction in carbon emissions only is not enough; climate-adapted plans are now needed to make climate-resistant systems feasible. Furthermore the problem of rapid extinction of species and the subsequent decline of biodiversity obliges to correspondingly increased provisions under the new policies, regulations and directives.

Solar tower aided coal-fired power generation system (STCG) is able to provide high solar utilization efficiency with low coal consumption rate. This paper compares performances of a solar tower aided coal-fired power plant, a solar tower power plant and a coal-fired power plant under different operative conditions. The comparison includes various solar multiple and thermal energy storage size. According to solar radiation resource and grid power dispatching demand, STCG, solar tower power generation system (STG) and coal-fired power generation system (CPG) work under off-design conditions all the year around. Results show that STCG has higher solar utilization efficiency than STG and lower coal consumption rate and CO 2 emission rate than CPG. In addition, solar-to-electricity exergy efficiency of STCG is at least 1.83% higher than that of STG. Compared to CPG, the 1000 MWe STCG can reduce coal consumption by 2.0 Â 10 5 t/y, with the saving ratio being 10.4%. The annual average coal consumption rate of STCG is 27.3 g/kWh lower than that of CPG. In addition, the annual average CO 2 emission rate of STCG is reduced by 10.1% compared with that of CPG. Solar tower aided coal-fired power generation can facilitate energy conservation and emission reduction of STG and CPG.

A latent heat storage system for concentrated solar plants (CSP) is numerically examined by means of CFD simulations. This study aims at identifying the convective flows produced within the melted phase by temperature gradients and gravity. Simulations were carried out on experimental devices for applications to high temperature concentrated solar power plants. A shell-and-tube geometry composed by a vertical cylindrical tank, filled by a Phase Change Material (PCM) and an inner steel tube, in which the heat transfer fluid (HTF) flows, from the top to the bottom, is considered. The conjugate heat transfer process is examined by solving the unsteady Navier–Stokes equations for HTF and PCM and conduction for the tube. In order to take into account the buoyancy effects in the PCM tank the Boussinesq approximation is adopted. The results show that the enhanced heat flux, due to natural convective flow, reduce of about 30% the time needed to charge the heat storage. A detailed description of the convective motion in the melted phase and the heat flux distribution between the HTF and PCM are reported. The effect of the mushy zone constant is also investigated.

Prinsloo, G.J. "Hardware Sun Tracking Systems and Digital Sun Position Hardware Solar Tracker Controllers". In Solar Tracking. GJ Prinsloo. 1st ed. Stellenbosch: SolarBooks, 2016. ISBN 978-0-620-61576-1. doi: 10.13140/2.1.2748.3201
Chapter in free eBook on Solar Tracking Systems, Sun Tracking Systems, Sun Tracker, Solar Tracker, Follow Sun, Sun Position. A number of commercial and proprietary solar tracking controller solutions for a variety of automation platforms are available in the market. These sun tracker solutions include algorithms for computing the sun vector, mostly for PLC (Programmable Logic Controller) and PAC (Programmable Automation Controller) processors as well as FPGA (Field Programmable Gate Arrays). Most of these solar tracking controllers are universal controllers suitable for a variety of solar systems and mode switchable to control point focus, linear (parabolic trough) or central receiver Heliostat solar receiver systems. This chapter aims at giving the reader a wide angle view of available sun tracker solutions and presents some of the solar tracking automation solutions presently available.
Free to download eBook on Practical Solar Tracking Design, following the sun solar tracking system, sun tracking system, sun tracker system, solar tracker system, sun positioning system, and sun path tracking with follow the sun position calculation (azimuth, elevation, zenith), sun trajectory, sun following system, sunrise tracking, sunset tracking, sunlight-phases, dawn, dusk, moon-phase, twilight, moonrise, moonset calculator. Solar Tracking is a key Technology to unlock the full potential of RE in RES.
https://www.researchgate.net/profile/Gerro_Prinsloo
Solar Tracking, Sun Tracking, Sun Tracker, Solar Tracker, Follow Sun, Sun Position
https://www.researchgate.net/publication/263128579_Solar_Tracking_Sun_Tracking_Sun_Tracker_Solar_Tracker_Follow_Sun_Sun_Position

solar power is the conversion of sunlight into electricity, either directly using photovoltaics (PV) or indirectly using concentrated solar power (CSP). The concentrated solar power system uses lens or mirrors and tracking systems to focus a large area of sunlight into a small beam. The process of conversion of light into electric current by the photovoltaics is known as the photovoltaic effect. Solar photovoltaic arrays are subjected to partial shading and rapid fluctuations of shading, in most of the portable applications. By partially shaded cells, the residual energy generated, either cannot be collected if the diode is bypassed, or impedes collection of power from the remaining fully illuminated cells, if the diode is not bypassed. The PV system is capable of maximizing the power generated by every PV cells in the PV panel. This system comprises of an array of parallel connected PV cells, a low-input voltage step up power converter and a simple bandwidth MPPT (Maximum Power Point Tracking) tracker. The MPPT operation is to adjust photovoltaic interfaces, so that the operating characteristics of the load and the photovoltaic array match at the maximum power point, no matter what the stand-alone or grid connected photovoltaic applications are.

Electricity has an essential role in our daily life. However, with the ever increasing cost of fossil fuels and natural gas, power generation with higher efficiency and lower capital cost is in high demand. Nowadays, global warming and climate change have become vital issues prompting investigations into increasing the share of renewable sources of energy implementation in power generation. Solar energy is arguably the most favorable solution for a greener power generation technology. With solar technology’s current level of maturity, solar energy cannot provide a significant contribution to the world’s energy demand due to intermittency and storage issues. A possible solution to the aforementioned difficulties is power plant hybridization. In particular, concentrated solar power technologies are displaying significant potential for electricity production. The United Arab Emirates’ hot, sunny climate is an indication of the great potential it possesses for hybrid and solar only power plant implementation. In this research work, the feasibility of a 50 MWe hybrid (solar and natural gas) combined cycle power plant with a topping gas turbine cycle and four different bottoming cycles are assessed. Power plant hybridization is accomplished by employing a solar tower collector (Heliostat field collector). Three rather unconventional bottoming cycle configurations have been chosen including gas turbine (air bottoming cycle), water injected gas turbine (humid air bottoming cycle), and the Maisotsenko cycle (Maisotsenko bottoming cycle). These three configurations along with the conventional combined cycle power plant (steam bottoming cycle) are optimized by conducting thermo-economic and transient analyses in MATLAB to identify the most economically justified plant configuration for the United Arab Emirates. Additionally, two different heliostat field layouts are taken into consideration including the radial-staggered and spiral layouts. Moreover, thermo-economic evaluation is accomplished by utilizing five different economic approaches, i.e. net present value, payback period, life cycle saving, Knopf objective function, and levelized cost of electricity.

Desalination plays a critical role in filling the gap between freshwater demand and availability in water-scarce Sultanate of Oman since 1976. Installed desalination capacity in the country has almost increased by 60 times that in 1976 with increasing fresh water demand. Even though desalination share is increasing, 80-85% of freshwater demand today is still satisfied with groundwater and natural sources. This is leading to increased soil salinity in recent years affecting the crop production. All the planned and installed desalination plants in the country use conventional fuels for their operation. None of the plants are based on any form of renewable energy source. Consumption of fossil fuels for the operation of these plants is increasing at an average rate of 3-5% affecting the net export for the country. Sultanate of Oman is considered to be one of the most suitable destinations for solar energy applications and solar energy can play a vital and sustainable role in meeting the gap between the demand and supply of fresh water using solar thermal desalination. This paper emphasizes on addressing this aspect for the country. An overview of present desalination status and fresh water demand, fuel requirements, solar energy availability, thermal desalination technologies and solar thermal technologies has been presented in the paper. Conventional thermal desalination technologies and solar thermal technologies have been compared for same capacity on the scale of 1 to 5 for various factors in the context of Sultanate of Oman. Few of the challenges and barriers in the implementation of solar thermal desalination in the country are also discussed in the paper. Fixed focus type Scheffler dish reflectors (SDR) are suggested as one of the best suitable option to be coupled with multi-effect desalination technology for small to medium capacity decentralized type plants. Parabolic trough collectors (PTC) coupled with Combined Cycle Gas Turbine (CCGT) or Open Cycle Gas Turbine (OCGT) plants would be a feasible solution for higher capacity desalination plants.

Improving access to energy in developing countries without exacerbating climate change requires novel technical strategies. MicroCSP power plants using organic Rankine cycles (ORCs) are one example of a promising approach for meeting this challenge. Specifically, expander development has been identified as a critical component for enhancing the performances of small ORC units. The goal of this project is to develop an optimized two-stage scroll expander to be integrated in a MicroCSP power plant designed to supply remote, off-grid areas.

The expansion requirements are firstly defined so as to meet production specifications. Then, employing a deterministic model and a selection process, optimal scroll geometries are chosen for both expansion stages. The deterministic model is executed with Matlab and accounts for the relevant physical phenomena i.e. radial and flank leakages, throttling losses at the intake and exhaust processes, friction between the two scrolls and mechanical losses in the different bearings. A performance enhancement of about 6\% of the isentropic efficiency is predicted in comparison with baseline practice.

A CAD model of a single-stage prototype is developed in Solidworks following the main architectural features of a compliant HVAC scroll compressor. This CAD is updated and improved with the optimal scroll geometries and some parts are 3D printed to verify their mechanical assembly. Toolpaths to control CNC machines are generated using the CAM program HSMXpress and the parts constituting the expander prototype are manufactured in a machine shop.

In conclusion, the properties of the enhanced scroll expander are evaluated in the context of a typical Micro-CSP plant. A simple steady state model in EES is developed to quantify how three parameters (T_ev, T_cond and eta_exp) influence the power plant overall sunlight to electricity conversion efficiency (a gain of 0.73% is predicted). This project underscores the importance of optimizing the expansion process and identifies further research pathways to progress towards this goal.

Specific heat is a key thermal property in energy systems and is directly linked with heat storage and transfer. Concentrated solar thermal (CST) power plants which incorporate thermal storage show promise to deliver affordable, renewable and reliable electricity without harmful emissions. As compared to wind and photovoltaic installations, which are intermittent, CST systems (with thermal storage) represent a technology which can be dispatched to provide a good match with energy demand e or at least to maximize revenue. At present, molten salts represent the dominant thermal storage medium. However, the low specific heat value of molten salts severely limits their applicability. Increasing the specific heat of molten salts could allow for a sizable reduction in storage volume, or for more energy to be stored in the same volume. Recently, researchers have shown that the specific heat of fluids can be altered through the addition of nanoparticles, although the fundamental governing mechanisms for the observed changes in this property have not yet been agreed upon. This paper provides a comprehensive review of recent, albeit sometimes contrary, nanofluid specific heat studies. Since a critical review of the ongoing work in this field has not yet been compiled, this paper provides insights into the range and magnitude of specific heat changes. This review also discusses possible underlying enhancement mechanisms, the impacts of colloidal stability, and uses these to rationalize the diverse range of results seen in the literature. Through reviewing the salient literature, it is hoped that this paper will help to guide future efforts in controlling the specific heat of nanosalts.

Shifting to a low-carbon electricity future requires up-to-date information on the energetic, environmental and socioeconomic performance of technologies. Here, we present a novel comprehensive bottom-up process chain framework that is applied to 19 electricity generation technologies, consistently incorporating 12 life-cycle phases from extraction to decommissioning. For each life-cycle phase of each technology the following 4 key metrics were assessed: material consumption, energy return ratios, job requirements and greenhouse gas emissions. We also calculate a novel global electricity to grid average for these metrics and present a metric variability analysis by altering transport distance, load factors, efficiency, and fuel density per technology. This work quantitatively supports model-to-policy frameworks that drive technology selection and investment based on energetic-economic viability, job creation and carbon emission reduction of technologies. The results suggest energetic-economic infeasibility of electricity generation networks with substantial shares of: i) liquefied natural gas transport, ii) long distance transport based hard and brown coal and pipeline natural gas, and iii) low-load factor solar-photovoltaic, Page 2 of 37 concentrated solar power, onshore and offshore wind. Direct sector jobs can be expected to double in renewable-majority scenarios. All combustion-powered technologies without natural (biomass) or artificial carbon capture (fossil fuels) are not compatible with a low carbon electricity generation future.

To go hand in hand with the development of the country and face the rapidly increasing energy demand, Morocco began developing a green plan in order to produce 2000 MW of renewable energy on the horizon of 2020. Solar conversion is believed to play a pivotal role in the Moroccan energy transition. The principle objective of this work is to comprehensively overview the Moroccan parabolic trough solar thermal power plant Noor 1 as one of the leading solar plants in Africa and Middle-East. The main motivations behind the site selection as well as a detailed technical description of the plant are provided. For the first time, existing similar parabolic trough solar thermal power plants worldwide are reviewed and compared. It was concluded that the specific energy generation of Noor 1 is well ranked among the compared plants (superior to 61.5% of other plants).

New energy sources have been researched with the objective of achieving a reduction in the emissions of greenhouse gases as well as other polluting gases. Solar energy is one of the options as when properly concentrated offers a great potential in high temperature applications. This paper offers a review on all fields connected with materials where concentrated solar energy has been applied. These applications include metallurgy , materials processing (welding and cladding; surface treatments; coatings and surface hardening; and, powder metallurgy), and non-metallic materials (ceramics, fullerenes, carbon nanotubes, and production of lime).

We report the first ever robocast (additive manufacturing/3D printing) sintered ceria scaffolds, and explore their use for the production of renewable fuels via solar thermochemical fuel production (STFP, water and carbon dioxide splitting using concentrated solar energy). CeO2 catalyst scaffolds were fabricated as 50 mm diameter discs (struts and voids ∼500 μm), sintered at 1450 °C, with specific surface area of 1.58 m2 g−1. These scaffolds have hierarchical porosity, consisting of the macroporous scaffold structure combined with nanoscale porosity within the ceria struts, with mesopores <75 Å and an average pore size of ∼4 nm, and microporosity <2 nm with a microporous surface area of 0.29 m2 g−1. The ceria grains were ≤500 nm in diameter after sintering. STFP testing was carried out via thermogravimetric analysis (TGA) with reduction between 1050–1400 °C under argon, and oxidation at 1050 °C with 50% CO2, gave rapid CO production during oxidation, with high peak CO production rates (0.436 μmol g−1 s−1, 0.586 ml g−1 min−1), for total CO yield of 78 μmol g−1 (1.747 ml g−1). 90% CO was obtained after just 10 min of oxidation, comparing well to reticulated ceria foams, this CO production rate being an order of magnitude greater than that for ceria powders when tested at similar temperatures.

Many countries all over the world have started to massively introduce renewable energy sources as clean alternatives to conventional energy sources. These technologies are expected to reduce pollution and dependence on fossil fuels. Indeed, the objective of introducing these alternative energy sources is to switch to more sustainable ones that would not compromise the capability of future generations to meet their own energy requirements. However, not many studies have been conducted to illustrate the impact of those renewable energy sources on the environment. Therefore, it is necessary to study their impact taking into consideration all stages of the life cycle of the power plant: the extraction of raw materials, construction of components, installation, operation and maintenance of the plant; and the end of life including waste management. This study focuses on one renewable energy source, which is Concentrated Solar Power (CSP). The approach used is a life cycle analysis of a CSP power plant located in Morocco using a software (OpenLCA) and supported by studies performed from the literature review. The results show that the phase that has the most impact on the environmental performance is the extraction and manufacturing phase followed by operation and maintenance phase. In addition, the environmental category that is most impacted by the technology is the land transformation. The land and soils are significantly impacted and become prone to erosion, temperature change and biodiversity change. Still, the impact is less significant that the adverse environmental impact that arises from conventional energy sources. Moreover, the calculated energy payback time for this case is 15 months, which is considerably less than the energy payback time required from other power plants. Areas of future research have been identified to be able to mitigate the impact of CSP power plants on the soils and to decrease the impact of the material extraction and manufacturing phase on the environment.

In today’s world, electricity is mostly generated from
coal based thermal power plants that used coal as its primary
fuel. In spite of an increase of the renewable power into the
grid, Coal based Thermal power plants are going to rule the
power generation sector in the future to meet the fast growing
power needs of the country. Solar energy is one of the easily
available sources of renewable energy and could be used to
increase the effectiveness of steam power plants. This paper
establishes that the fuel saving in coal-fired Power plant by
integrating solar energy to increase the temperature of the
feed water entering the boiler. As a result, the amount of fuel
required to heat the feed water within the boiler to produce
steam is reduced. This plant model incorporates a field with
solar Fresnel collectors that directly heats boiler feed water.
The proposed plant model modification saves substantial
fossil fuel input reduction. The best results can be acquired
when the group of high pressure heaters (HPH) is replaced by
solar field and feed water temperature exceeds its original
design value. So it required less amount of heat input from
the boiler. A pulverized coal power plant is one of the main
CO2 release resources. The integration of the solar field into a
pulverized coal power plant assists it to reduce the coal
consumption and CO2 emissions.

The distributed cogeneration of energy is one of the leading arguments for the improvement of renewable energy share in the energy consumption at European level. The actual work describe the realization of a modular 1-3 kWe, 3-9 kWth micro Combined Heat and Power (m-CHP) system based on innovative Concentrated Solar Power (CSP) and Stirling engine technology.
This CSP m-CHP will provide electrical power, heating and cooling for single and multiple domestic dwellings and other small buildings.
It integrates small scale concentrator optics with moving and tracking components, solar absorbers in the form of evacuated tube collectors, a heat transfer fluid properly investigated, a Stirling engine with generator after the development and testing of two main solutions, and heating and/or cooling systems; it incorporates them into buildings in an architecturally acceptable manner, with low visual impact.
The work is part of a European Funded project (DiGeSPo) in the CALL ENERGY-2009-1.

The paper presents the preliminary operational performance results of the of two 3.5 kWp Concentration PhotoVoltaic (CPV) devices. Each system consists of eight modules installed on a chassis for a total number of 1152 triple junction PV cells whose active area is 5.5 × 5.5 mm. The optics has a total geometrical concentration ratio of 476×. Two solutions for the primary PMMA Fresnel lens were tested, one with constant Fresnel pitch and one with variable pitch. The secondary optics is the same for both systems and consists of a truncated pyramid made of high reflective material. The two-axis tracking system is an azimuth-elevation device driven by two electrical motors and controlled by a sun sensor. Results allow to evaluate the efficiency of the plant as well as significant operational parameters under real outdoor operating conditions. The overall AC electrical efficiency is up to 31% and the power production peak is 2.54 kW. Electric power output has a linear dependency with the available Direct Normal Irradiation (DNI) while the Air Mass (AM) spectrum has a negligible effect on the performance. The system equipped with a variable pitch Fresnel lens performs slightly better (about 3.5% more power) with respect to the one with a constant pitch. The effect of lens fouling has a much higher impact: with a dirty lens the system generates over 12% less power and efficiency decreases by 3–5%, at equal solar irradiation. The performance ratio of the CPV system peaked at 82% and it has a monthly value over 70% in spring and summer months. The tracking mechanism has showed, in the worst scenario, an inaccuracy of 0.26° which is lower than the acceptance angle of the optics (0.4°).

Solar chimney or solar updraft tower power plant is an alternative renewable technology for fossil fuels in power generation, which also needs improvement to become more efficient, economical, and practical for electricity production. The combination of solar chimney power plant (SCPP) with the Concentrated Solar Power (CSP) system is investigated in this study. The work includes experimental and computational fluid dynamic (CFD) investigations performed on a constructed solar chimney pilot setup with 12 m chimney’s height to evaluate the system’s performance in conventional design and the presence of an additional heat source. The maximum velocity inside the chimney in normal operating conditions in the daytime was 2.2 m/s, which improved to a maximum of 2.72 m/s by using a secondary heat source. Also, in the nighttime, the velocity inside the chimney improved from 0.2 to 1.93 m/s with the same additional heat source. Moreover, the intended hybrid design provided much longer system operation during the night, which is essential to meet the continuous power demands.

The concentrated solar thermal industry is moving towards higher temperature receivers. Gas-phase receivers represent a near-term solution that can achieve such temperatures, but most designs for pressurised receivers require a window. The window represents the weak link in the designs, limiting a receiver's operational life, temperature, and pressure. Indirectly-irradiated receivers, which do not require a window resolve these issues, but introduce a detrimental performance trade-off because solar energy must be effectively conveyed through a solid receiver wall. This can result in a lower thermodynamic efficiency (first and second law) since there is a large difference in temperature between the inside and outside of the receiver wall. To deal with these issues, this paper investigates novel, indirectly-irradiated receiver designs with the potential to reduce the temperature drop across the receiver wall. The proposed new type of cavity absorber was designed by first considering its optical performance via a detailed ray-tracing analysis. These results indicated that a cylindrical cavity with an inverted conical base provides the highest optical efficiency, around 92%, compared to other cylindrical cavities with different base shapes. Next, to reduce the temperature drop in the design, heat transfer enhancements for the cavity wall were explored using the ray tracing-calculated radiative flux. It was found that a compound technique of impinging jets on an extended surface enables more design freedom while also providing higher convective heat transfer coefficients compared to either technique alone. To explore the range of heat transfer enhancements that are possible with these methods, this paper also presents parametric performance maps of heat transfer coefficients and pressure drop as a function of nozzle-to-cavity distances, nozzle diameters, and the number of nozzles. According to this analysis, a design with around 48 nozzles per square metre, each of 9 mm diameter, around a metal foam-covered cavity, achieved the optimum design point with respect to the overall heat transfer efficiency. Overall, it was found that an optimally designed indirectly-irradiated gas-phase receiver can indeed provide high performance and can potentially enable solar systems to reliably operate at well above 600 °C for driving advanced thermodynamic cycles.

The present work describes the realization of a modular 1-3 kWe, 3-9 kWth micro Combined Heat and Power (m-CHP) system based on innovative Concentrated Solar Power (CSP) and Stirling engine technology. The cogeneration of energy at distributed level is one of leading argument in large part of energy policies related to renewable energy resources and systems. This CSP m-CHP will provide electrical power, heating and cooling for single and multiple domestic dwellings and other small buildings.

This study aims to investigate the influence of various parameters on the freshwater yield and efficiency of a novel concentration-based solar desalination system. The system performance under the summer and winter climatic conditions of Rabat city, Morocco is evaluated. The design parameters are glass cover thickness, absorber basin thickness, brackish water mass, and absorber basin material. The climatic parameters are wind velocity, ambient temperature, and solar radiation. Numerical studies on different system parameters are done by examining the effect of system component parameters on the system performance. Through the MATLAB code, the equations for the freshwater yield and efficiency of the new system are constructed and solved. The results show that the system gives the best performance with 6 mm glass cover thickness, 2 mm absorber basin thickness, and 40 kg brackish water mass.

The study proposed methods of determining the relative suitability of three major component/requirements of a hypothetical 100MW concentrated solar power plant in Malam-Fatori, a location in Borno State, northern Nigeria. The component/requirements to be selected are solar concentrators, heat transfer fluid (HTF) and thermal energy storage (TES) medium. The most suitable concentrator amongst three different variants; Sky Fuel Sky Trough 80-mm OD receiver (SF), Siemens SunField 6 (SSF) and EuroTrough ET150 (ET), was selected by subjecting them to simulation at varying solar multiples using the System Advisor Model (SAM). A comparative analysis of the simulated energy output, levelized cost of electricity (LCOE) and total solar aperture area was used to determine the most suitable concentrator. For HTF, the study compared the characteristics of Therminol VP-1 to that of Therminol 59, while for TES medium; HITEC Solar Salt, HITEC XL (Eutectic), HITEC XL (low calcium) and ordinary HITEC Salt were subjected to comparative analysis based on the climatic conditions of the location under review and the chemical composition of the various media. The study revealed that SF has highest annual energy output and the lowest LCOE, while also competing favourably in terms of land requirement (< 3% more land requirement than SSF and ET). It further revealed that Therminol VP-1 is preferable to Therminol 66 as HTF due to higher maximum operating temperature and maximum field flow velocity. Additionally, HITEC Solar Salt is the most preferred TES medium due to greater tolerance to high ambient temperatures and absence of corrosive calcium nitrates.

Özet: Yoğunlaştırılmış güneş enerjisinde yaygın kullanılan bir yapı bütünleşik parabolik toplayıcılardır (BPT). Bu toplayıcılar temel olarak yansıtıcı ve yutucu yüzeylerden oluşmaktadır. Parabolik oluk tip toplayıcıların aksine bu sistemler güneşi takip mekanizması içermeyen basit yapılı sistemlerdir. BPT'ler ile ~200°C sıcaklıklarda akışkan veya buhar elde edilmesi mümkündür. Bu çalışmada, vakum tüplü bir toplayıcı içeren BPT'nin geometrik tasarımı ve ışın analizi yapılmıştır. Farklı geliş açısı ve yansıtıcı kesimleri için, ışınım değerinin ve optik verimin gün boyu değişimi incelenerek, günlük toplam ışınım kapasitesi hesaplanmıştır. Çıkan sonuçlar tasarlanan BPT'nin optik etkenliğinin geleneksel vakumlu tüplü toplayıcıların iki katı civarında olduğunu göstermektedir. Anahtar Kelimeler: güneş enerjisi, bütünleşik parabolik toplayıcı, optik verim, vakum tüplü yutucu DESIGN AND OPTICAL PERFORMANCE EVALUATION OF A COMPOUND PARABOLIC COLLECTOR Abstract: Compound parabolic collectors (CPC) are a common structure in concentrated solar energy applications. This type of collectors are basicly consisted of a reflector and an absorber. In contrast to the parabolic trough collectors, CPC's are simple structured systems which do not involve a sun tracking mechanism. It is possible to obtain fluid or vapor at temperature of ~200°C with CPC's. In this study, geometrical design and optical analysis of a CPC was performed. Daily total thermal capacities of CPC's which have different incidence angles and truncation lengths were calculated by

Because of the depletion of fossil fuels and global warming issues, the world energy sector is undergoing various changes towards increased sustainability. Among the different technologies being developed, solar energy, and more specifically CSP (Concentrated Solar Power) systems are expected to play a key role to supply centralized loads and off-grid areas in the medium-term. Major performance improvements can be achieved by implementing advanced control strategies accounting for the transient and random nature of the solar heat source. In this context, a lab-scale solar power plant has been designed and is under construction for experimental purposes and dynamic analysis. The test rig includes an Organic Rankine Cycle (ORC) unit, a field of parabolic trough collectors and a thermal energy storage system.
This paper presents the results of an experimental campaign conducted on the ORC module alone. This power unit, designed for a 2.8 kW net electrical output, consists of two scroll expanders in series, an air-cooled condenser, a recuperator, a volumetric pump and an oil-heated evaporator. The ORC engine is constructed using standard mass manufactured components from the HVAC industry, this practice reducing considerably the system cost. The overall unit performance and components effectiveness are presented in different operating conditions and relevant empirical correlations are derived to be implemented in a steady state model of the ORC unit.

Concentrated solar power presents immense scope for the deployment of small-scale units focusing on diverse applications, including process heat and rural on/off-grid applications. This paper presents the analysis of solar irradiance variation on heat flux and temperature distribution at the dish concentrator receiver. A solar dish concentrator with a 2.8-m aperture diameter and a 0.4-m depth was used for this analysis. The solar ray intersection between a dish concentrator and its receiver, along with the heat flux distribution prediction, was carried out using SolTrace. The effect of flux intensity variation on temperature distribution at the receiver was investigated using COMSOL MULTIPHYSICS. The optical analysis considered 10,000 rays, and 91.65% of them were observed to reach the surface of the receiver. For 1000 W/m 2 of beam solar radiation, a peak heat flux and maximum temperature at the concentrator's focal plane are found to be 32.4 MW/m 2 and 923 K, respectively. The validation had been done using previously reported results in the literature to verify the correctness of the present simulation results. The effect of beam solar radiation variation on heat flux intensity and the temperature distribution revealed that both heat flux and temperature increase with increasing solar radiation, which points out the influence of design and operating conditions. Apart from PillBox and Gaussian distributions, the effect of slope and specularity errors was characterized, suggesting a greater sensitivity to the former than the latter.

In this paper, a detailed thermodynamic model for a heat exchanger (HX) working with a dense particle
suspension (DPS) as heat transfer fluid (HTF) in the solar loop and water-steam as working fluid is presented. HX modelling is based on fluidized bed (FB) technology and its design has been conceived to couple solar plant using DPS as HTF and storage media with Rankine cycle for power generation. Using DPS as heat transfer fluid allows extending operating temperature range what will help to reduce thermal energy storage costs favoring higher energy densities but will also allow running power cycle at higher temperature what will increase its efficiency. Besides HX modelling description, this model will be used to reproduce solar plant performance under steady state and transient conditions.