Search

Thermocline sensible heat storage (SHS) systems are usually utilized in parabolic trough solar power systems. Liquid lead–bismuth eutectic (LBE) is a potential heat transfer medium for SHS systems, but its influences on the performances of SHS systems are rarely studied. In this study, a simulation model of thermocline SHS tank using liquid LBE as the heat transfer fluid is established, and the influences of initial cold and hot LBE temperatures on the operation and mechanical performances of the tank are estimated. The results reveal that when the liquid LBE is used as the heat transfer fluid, the SHS tank can operate stably. The initial cold LEB temperature has almost no influence on both the total heat storage and heat release durations of the tank, while the initial hot LBE temperature has proportional relationships with the total heat storage and heat release durations. The heat storage performance as well as the heat release behavior of the tank can be improved by increasing the initial cold LBE temperature, or by decreasing the initial hot LBE temperature. The peak maximum mechanical stress of the tank can be decreased by increasing the initial cold LBE temperature, or by decreasing the initial hot LBE temperature.

Parabolic trough collector (PTC) is the most cost-effective and mature concentrated solar power (CSP) technology for solar thermal utilization. However, the highly concentrated solar irradiation on the bottom of the absorber tube causes high local temperature, thermal stress and deformation, further leading to damage and performance degradation of PTC. In order to alleviate the above problem, a novel parabolic trough receiver (PTR) with ribbed absorber tube is proposed to improve the thermo-mechanical performance of PTC Moreover, the multi-objective optimization is employed to determine the optimal parameter combinations (slant angle ( β ), size (e), pitch (p), and number of the ribs (N)) of ribbed absorber tube coupled with 3D numerical simulation and the genetic algorithm (GA). Based on the TOPSIS method and performance evaluation criteria (PEC) value, the ribbed absorber tube with the optimal geometric parameters of β = 15 ° , N = 6 , e = 4 . 5 mm and p = 20 mm is selected in the Pareto Front as the suggested optimal design. Furthermore, the performance of the PTRs at different inlet temperature of the fluid ( T i n = 400 –600K), direct normal irradiance (DNI=300–1000 W/m2) and mass flow rate (M=0.62–3.72kg/s) are evaluated. It is found that the ribbed absorber tube can effectively disturb the fluid near the boundary and induce longitudinal vortexes flow, which results in significant improvement in heat transfer between fluid and absorber tube, thereby enhancing the performance of the PTC. Compared to the plain tube, the heat transfer and flow resistance of the optimal ribbed absorber are enhanced by 57%–225% and 222%–630%, and the heat loss is lessened by up to 79.3%, resulting in 2.3% and 2.2% improvement in the heat collecting efficiency and overall efficiency. The findings in this paper may provide practical guidelines for developing efficient PTC.

Solar energy 259, 257-276 (2023). doi:10.1016/j.solener.2023.05.008, Published by Elsevier Science, Amsterdam [u.a.]

Solar energy is the leading thermal source from the sun, with huge use of technology such as photovoltaic cells, solar power plates, photovoltaic lighting, and solar pumping water. The current effort deals with solar energy analysis and a technique to enhance solar aircraft effectiveness by using solar and nanotechnological energy. The work is based on the investigation of thermal transfer by utilizing hybrid nanofluid past an inside solar wings parabolic trough solar collector (PTSC) to rich the studies of the solar aircraft wings. The thermal source is titled solar radiative flow. For various properties such as porous media, Cattaneo Christov heat flux, viscous dissipation, play heating and thermal energy flow, the heat transfer efficiency of the wings is verified. In the case of the tangent hyperbolic fluid, the entropy generation analysis was applied. The modeled energy and momentum equations were managed using the well-established numerical plan known as the Keller box process. This paper is made up of double-different kinds of nano solid particles, Cu (copper) and ZrO2 (zirconium dioxide) in EG (ethylene glycol) as standard fluid. Various control parameters are discussed and shown in figures and tables for velocity, shear stress, temperature outlines, frictional factor, and Nusselt number. The efficiency in the aircraft wings in the case of thermal radiation amplification and variable thermal conduction parameters is seen to be improved in terms of thermal transfer. In comparison to the traditional nanofluid, hybrid nanofluid is the ideal source of heat transfer. The thermal efficiency of ZrO2–Cu/EG compared to Cu-EG decreases to a low of 2.6% and peaks to 3.6%.

The integration of hybrid renewable energy systems, such as hybrid solar-biomass, to address thermal energy needs in various applications is a promising, efficient and eco-friendly solution that can be successfully applied for traditional baths in Morocco. Indeed, these systems are not widespread in Morocco, since traditional firewood furnaces are still commonly used for heating purposes in many different applications. Accordingly, the main objective of the study is to introduce a new hybrid solar-biomass system designed for space heating and hot water supply in a public bathhouse in Marrakesh, Morocco. This hybrid system includes small-scale pellet boilers and small dimension parabolic trough solar collectors (PTC), which is the first small-size PTC facility proposed for low temperature applications (less than 100 °C) in Morocco. Moreover, the preliminary simulation results of this hybrid solar-biomass system for space heating – case study – using TRNSYS software are presented. The use of such a hybrid system as a new design to retrofit conventional firewood boilers that are widely used for space and water heating in public bathhouses will lead to significant savings in firewood, which will contribute in particular to reducing deforestation in Morocco and will also result in substantial reductions in CO2 emissions.

This work investigates the performance of a conventional steam power plant retrofitted with a solar-assisted regenerative system using Parabolic Trough Solar Collectors (PTC). The solar collectors were used to compensate for the effect of removing Low-Pressure (LP) turbine extractions without changing other elements of a 300 MW power plant unit during peak load operations. The steam power plant, located in Kuwait, receives high levels of solar irradiation. Modeling of the solar-assisted regenerative system using PTC is simulated for Kuwait’s weather conditions. Results of the system analysis show that removing the LP turbine extractions enhanced the performance of the steam power plant by 9.8 MW, with an optimum PTC aperture area equal to 25,850 m2. A techno-economic analysis was used to estimate the Levelized Cost of Energy (LCOE). Compared to an equivalent photovoltaic solar plant, the optimum aperture area and LCOE for the PTC solar plant were found to be less by 45% and 44%, respectively. When compared to an equivalent conventional steam turbine, the solar-assisted steam power plant decreased cost by 56% over the lifecycle of 25-years.

Biomass and fossil fuels are mostly used in rural areas of developing countries for cooking. These energy resources have negative impacts on the environment and human health mainly due to deforestation and greenhouse gas emissions. A cleaner and environmentally-friendly form of cooking is solar cooking using the sun's energy. Parabolic solar cookers perform better than other solar cookers such as box solar cookers since higher temperatures are achieved in a shorter duration. These higher temperatures allow most types of cooking processes such as; boiling, frying, roasting, and baking to be possible. The major problem with most conventional solar cookers is that cooking is not possible during off-sunshine periods. Integrating solar cookers with thermal energy storage (TES) makes cooking during off-sunshine periods possible. This paper presents a comprehensive review of parabolic solar cookers with TES which is a sustainable cooking solution for developing countries. Previous work on both parabolic trough and parabolic dish solar cookers with TES is presented. Solar cookers with storage are classified according to the two main types of TES technologies which are; sensible heat thermal energy storage (SHTES) and latent heat thermal energy storage (LHTES). The main conclusions of the review are that; parabolic dish solar cookers with TES are more common than parabolic trough cookers, more studies have been done using latent heat storage as compared to sensible heat storage, limited modelling work has been presented, most of the parabolic cookers used aluminum sheets as the reflecting material, large scale experimental studies are limited and fewer studies tackled the techno-economic and socio-economic aspects. The review also highlights research gaps on parabolic solar cookers with TES in terms of the modelling, combined TES (sensible and latent heat), different reflector materials, large-scale experimental setups, and techno-economic and socio-economic analyses. Other important aspects to consider for parabolic solar cookers with TES include; the choice of sensible or latent heat storage materials, environmental impact, types of food to be cooked, and social acceptance., Concentrating solar cooker, Latent heat, Sensible heat, Thermal energy storage, Parabolic dish cooker, Parabolic trough cooker.

Solar energy is a harmless form of energy that is plentiful. Due to the extreme usefulness of solar energy, it is used in applications like solar collectors (SCs). The application leads to this research that focuses specifically on the inclined magnetically driven Maxwell nanofluid flow on an endless plate. The Maxwell nanofluid flows past over an exponentially uniform, horizontal porous stretchable plate inside the parabolic trough solar collector (PTSC). The essential exterior resources in PTSC like thermal radiative, viscous dissipative flow and Joule heating parameters are considered. Two common Maxwell nanofluids are always being used in the application are chosen in this research; Copper-methanol (Cu-Ch3OH) and Titanium-methanol (TiO2-Ch3OH) in this research. The governing equation in PDEs involved is converted into higher-order ODEs by utilizing the similarity variables. The converted ODEs are solved numerically by adopting the Keller-box scheme. Based on the findings, Cu-Ch3OH nanofluid has better heat transfer compared to TiO2-Ch3OH. It is also found that the Cu-Ch3OH thermal efficiency can achieve a maximum of 29%.

A new Evacuated Tube Solar Collector (ETSC) incorporating a Nano-PCM with fins is presented and studied. The numerical mathematical 2D model of phase change heat transfer is highlighted. The effect of adding nanoparticles of copper (Cu) to paraffin wax on system performance was investigated. The heat transfer during the energy storage process is simulated using the Ansys-Fluent. Moreover, the solid-liquid phase change characteristics of the paraffin within the system are analyzed. Additionally, an optimization analysis of fin parameters (i.e. fin thickness and fin spacing) is performed. Finally, a series of comparative simulations are carried out to investigate the performance of the ETSC system with and without the Solar Parabolic Trough Reflector (SPTR). The results showed that adding fins has a great effect on the phase change heat transfer of the paraffin in the ETSC. It was noted that the PCM melts faster as the thickness of the fins gets thinner. Also, the addition of 1% of Cu to the PCM was found to be the optimum mass concentration at which the HTF outlet temperature increased by 2 K. Moreover, it was found that the ultimate flow rate that caused the entire mass of the PCM to melt is 0.003 kg/s.

Spain is one of the front runners of the development of Concentrated Solar Power (CSP) projects. In recent years, however, the CSP industry in Spain has faced significant financial challenges due to a dramatic withdrawal of the Feed-in-Tariff (FIT) in 2013. The primary aim of this paper is to assess when, and under what conditions, CSP projects, in particular, Parabolic Trough Collectors can potentially reach grid parity in the absence of any subsidies. This paper also goes further to investigate whether and how Parabolic Trough Collector (PTC) projects can be financially viable in the post-subsidy period, using the System Advisor Model as a simulation tool to conduct techno-economic analyses. The simulation results indicated that a 50MWe PTC project with TES of 4 hrs and a PPA price of €0.20 per kWh is the most viable model for developing CSP projects in Spain under post-subsidy condition. This paper concludes that, under current retail electricity prices and post-subsidy conditions, PTC projects can reach grid parity and become viable without direct incentives. Even though direct incentives will not be required, the CSP industry in Spain is still far from becoming fully self-sustained.

This investigation represents the optimum operation of a co-generation plant producing water and electricity at a specified geographical location in Ras Gharib, Egypt. A model has been set employing Parabolic Trough Collectors (PTC) utilizing molten salt as the working fluid for the solar island which exchanges heat with a simple steam Rankine cycle. Thereby, the steam turbine generates an adequate amount of electricity used to cover all the plants’ requirements including the Reverse Osmosis (RO) water desalination unit demand. Moreover, the Multi-Stage Flash (MSF) plant acts as a condenser for the proposed system, taking full advantage of hot steam exiting the turbine unit to desalinate seawater. The results are displayed considering the optimum operation of the plant along the year anticipating the amount of freshwater and electricity produced all year long using MATLAB/Simulink package. Monthly assessments yield that maximum production of 16000 m3/day and 2000 m3/day of fresh water can be produced from the MSF and RO plants respectively in July together with 12.65 MW can be supplied to the grid after meeting all the plant demands.

[EN] In the present paper, the mid-term performance of two different architectures of a solar-driven jet-ejector refrigeration system is numerically compared: the first one is fitted with a fixed-geometry jet-ejector while the second one is equipped with an adjustable spindle that modifies the jet-ejector area ratio. The jet-ejector behavior has been predicted with a validated computational fluid dynamics approach and the dynamic response of the overall system accounts for transient effects in a small parabolic trough collector and a hot thermal storage tank. The investigation shows that the adjustable jet-ejector allows for continuous and smooth operation in a much wider range of outdoor conditions. Additionally, it enables more efficient management of the thermal level in the hot storage system. As a result, the adjustable refrigeration system improves the performance indicators in all the warm months of the typical meteorological year under evaluation. The maximum improvement potential is found in May; the fixed-geometry system provides an average COPth of 0.34 while the adjustable system reaches an average COPth of 0.48 considering the same boundary conditions in both cases. (c) 2020 Elsevier Ltd and IIR. All rights reserved., Authors want to acknowledge to the institution "Conselleria dEducacio, Investigacio, Cultura i Esport de la Generalitat Valenciana" and its grant program "Subvenciones para la contratacion de personal investigador de caracter predoctoral" for doctoral studies (ACIF/2018/124) funded by The European Union

This chapter gives an overview of the parabolic-trough collector (PTC) technology, which has achieved a high degree of maturity. It includes a brief history of the technology, describing the first large solar thermal power plants with PTC (the SEGS plants), the main parameters and basic equations of a typical PTC, design criteria to achieve a good thermal and optical performance, operation, and maintenance issues, and expected technology improvements in working fluids and solar collectors that could be implemented in the short to medium term. Information about PTCs commercially available is also given in this chapter, with technical characteristics of both large and small size collectors. Moreover, the two-tank molten salt system currently used in PTC solar thermal power plants for storing thermal energy during sunlight hours to produce electricity when there is no direct solar radiation is described.

This chapter provides key highlights of the Concentrating Solar Power Best Practices Study, published in 2020 by the National Renewable Energy Laboratory ( Mehos et al., 2020 ). Focusing on parabolic trough and central receiver concentrating solar power (CSP) plants, the study gathered, categorized, and ranked issues encountered by a group of stakeholders representing key players in nearly 80% of CSP plants worldwide. This chapter provides key best practices to be considered in the areas of parabolic trough plants; central receiver plants; steam generation systems; engineering, procurement, and construction; quality assurance/quality control; commissioning; operation and maintenance; and solar resource measurement and performance modeling. Apart from the challenges of the steam generation system, trough plants have mostly operated with high availability, although the maintenance of certain components continues to challenge plant operators. Central receiver technologies are less mature, and the reliability of these systems is less demonstrated than in trough systems; the primary challenges are associated with salt-related systems. An unanticipated outcome is the extent to which non-technology project issues were challenges faced prior to the actual operation of the plant.

The extremely high temperatures in the Western Sahara region has to lead to difficulties in the supply of water and food. Sabkha-Tah in Morocco is one of the regions in the Western Sahara, which possesses conditions that prevent the farming of certain crops. Nevertheless, the region has the advantage of being in a zone 60 m below sea level. This geographical advantage has the potential to reduce energy consumption in the reverse osmosis unit (RO). An energy, water, and food nexus study that takes advantage of the region’s geographical characteristics are performed. A multi-generation system that produces cooling, power, and freshwater for a greenhouse situated in the Sabkha-Tah is proposed and thermodynamically analyzed. The freshwater is supplied through a RO unit that uses the hydrostatic pressure of falling water from the Atlantic Ocean. Cooling is supplied through an absorption cooling cycle that uses the waste heat of the Rankine cycle condenser, while a solar-powered Rankine cycle is used to feed the system with the required power. The system uses a parabolic trough collector (PTC), which utilises the high solar irradiance in Sabkha-Tah to generate the energy needed by the Rankine cycle. The PTC uses Cu/Therminol VP1 nanofluid as the working fluid to enhance the efficiency of the system. The study results show a reduction in the RO’s power consumption from 5.561 to 2.51 kWh/m3 by using an energy recovery turbine (ERT) and the hydrostatic pressure of the falling water. The system shows that 46.18 kW of pump work can be saved when using the hydrostatic water pressure. The overall energy and exergy efficiencies for the multi-generation system are calculated to be 60.81% and 29.76%, respectively, using TherminolVP1 in PTC, while the energy efficiency increased by 0.014% using nanofluid (Cu/TherminolVP1) with a volume fraction of 0.02.

One of the cleanest and most accessible energy sources is solar energy. However, finding efficient ways to receive this energy source and convert it to electrical power for different applications is still a challenging problem. A parabolic trough solar collector (PTSC) is a type of concentrating solar technology which can be employed for producing electricity and heating simultaneously, which is one of the efficient techniques to produce electrical power from solar energy. After several decades of research, development, and construction of different types of PTSCs, the most recent studies focus on improving the efficiencies of these systems, both from structural/material (solid mechanics) and heat transfer (fluid mechanics) aspects. Improving the PTSC performance has led to enhancement in the electrical energy production. From a heat transfer point of view, there have been many approaches proposed to reach a better efficiency for the PTSC system, such as nanofluids, internal flow inserts, and an external magnetic field acting on the magnetic nanofluid. This chapter discusses PTSCs with detailed explanations on the corresponding heat transfer formulations, and at the end, a numerical example is being analyzed using the ANSYS FLUENT software.

The solar tower and parabolic trough aided coal-fired power generation has been demonstrated as a promising technology and has potential advantages in utilisation of solar energy in a cost-effective manner. Due to introduction of solar energy, from the solar tower or parabolic troughs, increases to a certain extent, the steam temperature would be difficult to maintain and leads to safety concerns. Therefore, the limitation of integrated solar energy, considering the overlapped influence of different solar energy input, needs to be well identified and managed. This work considered a 600 MWe integrated system as an example. Solar energy from parabolic troughs is used in the preheater while energy from the solar tower is used to reheat steam. The novelty of this study is the interaction of different solar energy input in fossil plants and its benefits is revealed for the first time. The maximum absorbed solar energy, considering the mutual effects of introduced solar energy flows, are explored. Then the system performance under three different loads (100%, 75%, 50%) and hourly operational performance in four typical days are analysed. The paper shows that the feed-water extraction results in the enhancement of maximum solar energy absorbed by reheat steam extraction, is improved by 24.2 MWth (28.5%), 11.5 MWth (20.0%), and 5.6 MWth (14.3%) as feed-water extraction percentages increase at the three load conditions. As a result, the minimum standard coal consumption rates are improved by 13.2 g/kWh (5.2%), 10.7 (4.1%) g/kWh and 9.0 g/kWh (3.1%) respectively. In four typical days, the highest coal consumption reduction is reached in the summer solstice, which is 266.6-tonne, 202.8-tonne and 131.4-tonne under three different loads, while the highest coal consumption is obtained in the winter solstice.

Two emissions mitigation systems, as CO2 capture and storage (CCS) and concentrated solar power (CSP) have been investigated to a power plant based on exergetic and exergoenvironmental analyses. A base plant of natural gas combined cycle for power production is taken as case study. The CSP technology used is parabolic trough collector (PTC) with two storage tanks. The environmental impact indicator used is the eco-indicator 99. The outcomes indicate that the natural gas heater exchanger should have its exergy destruction reduced to improve the performance of all system. The CCS plant reduced the net power and the PTC plant increased slightly the net power in relation to the base plant. The specific environmental impact of CCS plant was increased and of PTC plant was slightly decreased. The environmental impact of fuel production is the main environmental burden in the environmental performance. Therefore, the PTC system is the best case of mitigation system. Discussions about further improvements have been proposed.

Summary: Side-by-side installations of flat plate photovoltaics and parabolic trough collectors consume significant space and have high system losses; by using an all-in-one, spectrum-splitting hybrid receiver, electricity and high-temperature heat can be generated with a single efficient system. Here, the performance of a transmissive concentrator photovoltaic/thermal (tCPV/T) system is demonstrated on-sun, with a total energy efficiency of 85.1% ± 3.3%, 138 W electric power at 304 suns (with average cell temperatures

The performance of solar air conditioning system (SACS) using Lithium-Bromide/water (Li–Br/H2O) solution and nanofluid -based parabolic trough collectors (PTC) under hot and humid climate conditions is presented in this study. The main objectives are to investigate the effects of different types of nanofluid (Al2O3/H2O and Cu/H2O) and the concentration of nanoparticle Cu (0.2 and 0.5 wt %) on the coefficient of performance (COP) of SACS system during a winter and summer days in desert regions. Mathematical models of the SACS system including the solar PTC, tank storage and the single-effect Li–Br/H2O absorption chiller are developed. The numerical simulation results show a good agreement with the experiment data accessible in literature. The results show that Cu/H2O nanofluid has the best performance. For the cold day and at noontime, the COP for pure water, 0.5 vol% Al2O3/H2O nanofluid and 0.5 vol% Cu/H2O nanofluid are 0.64, 0.68, and 0.74, respectively. The COP during the cold day increases by 12.5% and 15.5% when the concentration of Cu nanoparticle is 0.2 %vol and 0.5 %vol respectively. For the hot day and between 9:00 a.m. to 3:00 p.m. the maximum COP obtained is 0.77, and the effect of nanofluids is negligible. The single LiBr–H2O air absorption system reaches its maximum operation. A double effect of LiBr–H2O air absorption is needed to improve the performance of the system. Keywords: Solar, Absorption chiller, Li–Br/H2O, Single effect nanofluid

Solar-aided coal-fired power generation systems have been extensively studied and exhibit several advantages in the utilisation of solar energy. The issue with the solar augmentation of coal-fired plants is the limitation of the potential solar contribution that is practical to achieve when considering boiler safety issues. This study proposes the combination of parabolic troughs and solar towers to collect solar energy, that is then introduced into the preheaters and boilers of coal-fired power plants. Under the same investment conditions, this combination of solar technologies can provide more solar exergy and reduce the practical constraints on the solar contribution. The paper shows that the potential for a 660MWe power plant, integrated with a combined solar field allows the highest solar exergy share of 8.51% to be reached. This enables an increased fuel saving of at least 1.58 and 4.24 g/kWh compared to other systems, that gives a minimum coal consumption of 253.17 and 255.83 g/kWh, respectively. The combined solar field provides a maximum available solar exergy of 69.43 MWth, which is 7.83%–11.88% higher than the alternative compared systems. The enhanced solar exergy contribution and cost-effectiveness can be observed in this novel system under different solar loads and cost conditions.

Preprint version available., The aim of this paper is to empirically identify and rank the drivers and barriers to the deployment of concentrated solar power (CSP) in the EU in the past and the future at two different levels of analysis: System/grid or macro level and project/investment or micro level. An expert elicitation and an investors’ survey were carried out for this purpose. The results differ across the two levels (experts and investors), time frames and CSP designs. Specifically, deployment support, policy framework conditions and a proven technology have been major drivers of CSP deployment in the past, according to the expert elicitation. Dispatchability is regarded as the main future driver of the technology, followed by policy framework conditions and complementarity with PV. The survey of investors highlights the relevance of dispatchability, key technology and investors’ features as drivers, and stress the importance of administrative processes, construction permits and grid connection as barriers. The results suggest the need to combine different policies in order to activate the drivers and/or mitigate the barriers., The authors gratefully acknowledge support from the Horizon 2020 MUSTEC project (grant agreement No 764626).

Among all the hybrid solar thermal technologies available up to now, the Integrated Solar Combined Cycle (ISCC) is nowadays the most efficient system for converting solar energy into electricity. This power plant is a combination of a parabolic trough solar field with a conventional combined cycle. In the present article, the performance of an ISCC plant under southern Algerian climate has been investigated. To do so, a thermodynamic model has been developed to evaluate solar radiation intensity as well as the overall performance of the hybrid solar power plant.The analysis has shown that solar to electricity efficiency could reach up to 14.4% during sunny periods. Furthermore, an overall thermal efficiency of about 60% is feasible. It has also been found that the amount of electricity produced increases with several operation parameters such as the time of the day, the mass flow rate of the heat transfer fluid and the angle of incidence on the collector surface. Keywords: ISCC, CSP, Solar thermal power plant, Hybrid solar thermal power plant, Solar radiation

Solar thermal systems produce steam after being energized by solar parabolic trough concentrators, are incorporated with a steam turbine-generator assembly to produce electricity. This study presents a code for prediction of performance, while under-taking preliminary plant-sizing for a variety of parabolic trough solar fields operating under nominal conditions. The code, named as PTPPPP (Parabolic Trough Power Plant Performance Predictor) consists of four blocks. The code allows prediction of variables including: heat loss coefficient, UL, aperture effective direct normal irradiance, I, heat gain, Qgain, and the thermal efficiency of stand-alone parabolic trough solar thermal power plant in commerce, ηp. The conceptual design of the stand-alone parabolic trough solar involves: selection and sizing of system components, power generation cycles, working fluid types, and power block sizing. The input weather parameters and the operational parameters to the code have been acquired from in-situ measurements. The prediction results of the code have been found in good agreement with literature data with mean error of 0.18% in prediction of output power. In addition, this code is able to provide a flexibility in terms of temperature, heat transfer, and pressure range. Keywords: Direct normal radiation, Direct steam generation, Parabolic trough solar thermal power plant

In this paper, attempts have been made on the detailed energy and exergy analysis of solar parabolic trough collectors (SPTCs) driven combined power plant. The combination of supercritical CO2 (SCO2) cycle and organic Rankine cycle (ORC) integrated with SPTCs has been used to produce power, in which SCO2 cycle and ORC are arranged as a topping and bottoming cycle. Five organic working fluids like R134a, R1234yf, R407c, R1234ze, and R245fa were selected for a low temperature bottoming ORC. Five key exergetic parameters such as exergetic efficiency, exergy destruction rate, fuel depletion ratio, irreversibility ratio, and improvement potential were also examined. It was revealed that exergetic and thermal efficiency of all the combined cycles enhances as the direct normal irradiance increases from 0.5 kW/m2 to 0.95 kW/m2. As can be seen, R407c combined cycle has the maximum exergetic as well as thermal efficiency which is around 78.07% at 0.95 kW/m2 and 43.49% at 0.95 kW/m2, respectively. Alternatively, the R134a and R245fa combined cycle yields less promising results with the marginal difference in their performance. As inferred from the study that SCO2 turbine and evaporator has a certain amount of exergy destruction which is around 9.72% and 8.54% of the inlet exergy, and almost 38.10% of the total exergy destruction in case of R407c combined cycle. Moreover, the maximum amount of exergy destructed by the solar collector field which is more than 25% of the solar inlet exergy and around 54% of the total destructed exergy. Finally, this study concludes that R407c combined cycle has a minimum fuel depletion ratio of 0.2583 for a solar collector and possess the highest power output of 3740 kW. Keywords: Supercritical CO2cycle, Organic Rankine cycle, Exergetic performance, SPTCs, Organic fluids

SAHIN, Utkucan/0000-0002-5869-8451 WOS: 000428054800011 In this study, friction factors of heat transfer fluids (HTFs) that flow through the absorber tube in parabolic trough collector (PTC) are compared with using correlations. Syltherm 800 and Therminol VP-1 HTFs are considered for this study. Also, turbulent flow and rough pipe are considered for evaluation of the correlations of friction factor. The aim of this study is to compare a new non-iterative friction factor model, which is established for this study, with several alternative models against the Colebrook equation for friction factor and its effects on the relative error of pressure drop, Nusselt number estimated from the Gnielinski equation and heat transfer coefficient. All correlations are evaluated according to having mean absolute relative error (MARE) and root mean square error (RMSE). It is obtained that Reynolds number of Therminol VP-1 and Syltherm 800 are ranged from 1.1 x 10(4) to 2.97 x 10(6) and from 3.8 x 10(3) to 1.33 x 10(6), respectively. And, it is observed that friction factor of Syltherm 800 is higher than Therminol VP-1 at the same fluid temperatures. The results show that the new model established for this study is the closest correlation to the results of the Colebrook equation with having the lowest value of MARE and RMSE. MARE values of the new model is ranged in 0.01-0.02% for both Therminol VP-1 and Syltherm 800, and RMSE values of the new model are obtained as 3.78 x 10(-6) and 5.57 x 10(-6) for Therminol VP-1 and Syltherm 800, respectively. (C) 2018 Karabuk University. Publishing services by Elsevier B.V.

This research aims to develop a simple mathematical model for performance evaluation of a thermally exposed solar parabolic trough cooker. It was done under open environmental climate conditions for domestic uses. The experimental setup consisted of a solar cooker made of polished parabolic trough stainless steel having concentration ratio 9.867. The efficiency analysis depicts that the resulted parabolic trough optical efficiency range between 53-33%, theoretical efficiency between 50-30% and the experimental efficiency between 38-5%. Additionally, the maximum water temperature achieved was 37.2 °C at the outlet of parabolic trough. However, maximum water temperature achieved by parabolic trough cooker was 53.6 °C under stagnated conditions. Furthermore, the observed cooker energy efficiency range between 6.5-0.11% and exergy efficiency was in range between 7.6 × 10−2 - 2.1 × 10−2% for direct cooking. Results found helpful for making domestic useable cooker. Keywords: Energy and exergy efficiency analysis, Mathematical model, Performance evaluation, Solar parabolic trough cooker

The thermal stress on thick-walled components, such as tubesheets and steam drums, limits both the temperature ramp-up rates and the temperature differences between outer and inner walls. The cyclic operation of concentrating solar power plants may lead to fatigue damage. For these reasons, a stress analysis of the steam generator is required to assure its lifetime. A methodology is presented for the thermo-mechanical analysis of the steam generator for a parabolic trough power plant. This methodology consists of coupling transient thermodynamic and stress models of the heat exchangers in order to calculate the stress. Besides the heat exchanger models, a transient model for a TEMA H heat exchanger is proposed. Finite element simulations are carried out to calculate the deviations of the simplified analytical models. In this way, a powerful tool that allows the analysis and optimization of the steam generator operation is proposed. The results suggest that U-tube tubesheets are exposed to high thermal stresses on the no-tube-lane zone, especially in the reheater. The steam generator start-up can be accomplished in around 45 min using 36.4 MWhth. Furthermore, the TEMA X evaporator presents a thermal stress reduction of 35% compared to the kettle evaporator.

This chapter introduces the concentrating solar power (CSP), defined as power generated in the CSP systems that uses solar concentrators to convert solar energy into heat and then the produced heat is converted into power using heat engine based on Rankine, Brayton, and Stirling cycles. This chapter presents the main solar concentrator technologies and the solar energy resources based on the characteristics of sun and the type of solar radiation. It then explains the fundamentals of the main concentrating power plant technologies to convert solar energy resources into electricity and the technologies used for solar thermal energy storage. By the end of the chapter, a thermodynamic and economic study to evaluate a 3-MW Organic Rankine Cycle coupled to parabolic trough concentrator is presented.

The increasing penetration of PV and wind energy in several markets is forcing the power plants (both fossil and renewable) to operate with a high level of flexibility. In this scenario, the load-following capability of CSP power plants can play a fundamental role. The Thermal Energy Storage (TES) system allows exploiting solar energy after sunset and adjusting the power output according to the power demand variability. The paper aims to investigate different CSP plant configurations operating in island-mode to fulfill the power demand of a mid-size town located in the Upington region (South Africa). The power block is based on a steam Rankine cycle with superheated steam temperature 550°C, coupled with a molten salt direct storage system. Two solar fields are compared: Parabolic Trough Collectors (PTCs) and Central Receiver System (CRS). In order to analyze the load-following capability, two different electric loads (with the same annual energy demand of 360 GWh) are considered: the first one is typical of an industrial city, whilst the second one is the power demand pattern of a residential district. A numerical model of the two selected CSP technologies has been developed with the software Trnsys® and the optimization tool GenOpt. The simulation results show that the CSP plant based on CRS exhibits a higher load-following capability: both industrial and residential power demands are met with a lower aperture area and lower investment costs. The PTCs result to be affected by a strong efficiency variation between summer and winter: the load-following capability is good for the residential load profile, whilst is poor for the flat industrial load.

Parabolic trough collectors for concentrating solar sower plants are large scale optical devices with demanding requirements on optical and mechanical properties. Accurate mirror shape and absorber tube alignment are necessary to harness solar radiation with high efficiency. There are several methods to assess the shape of the mirror surface, yet there exist few approaches to effectively measure the position of the absorber tube. This paper provides a comprehensive overview on causes and effects of absorber tube displacement and on state of the art measurement techniques. A new approach on fully automated airborne absorber tube position measurement for parabolic trough collectors is presented, which outperforms existing methods concerning speed, spatial resolution, and level of automation, thereby achieving an accuracy of about 1.5 mm in vertical and lateral direction.

In this paper, the mathematical modelling of a novel Electrical Energy Storage (EES) Receiver for Solar Parabolic Trough Collector (PTC) is presented. The EES receiver is essentially a Heat Collecting Element (HCE) with built in storage in the form of thermal batteries such as the Sodium Sulphur (NaS) battery. The conceptual design and mathematical models describing the operation of the receiver are presented along with important results of model validation. When held under adiabatic conditions (a primary indicator of model validity), results were highly consistent with established PTC, models and with National Renewable Energy Laboratory (NREL, USA) experimental data for existing SCHOTT PTR-70 and Solel UVAC3 receiver tubes, currently being used in existing PTC power plants.

The energy for the solvent regeneration of post-combustion carbon capture (PCC) process is typically provided by steam bleeding from the power plant (PP) steam cycle. The energy penalty for steam bleeding results in serious reduction in the PP capacity estimated to be in the range of 10–40%. Power plant repowering or hybridization using solar-assisted PCC (SPCC) is a promising approach to satisfy carbon capture targets as well as PP load, concurrently. The drawback of this methodology is that notable amounts of solar energy are wasted during heat transfer from solar radiation to rich solvent. This paper presents a novel approach by eliminating the costly desorber system and using solar collector pipe (i.e. parabolic trough pipe) to directly heat the rich solvent and disassociate the bonds of CO2-solvent. This novel technology lowers the process capital expenditure, and also reduces the solvent regeneration energy bringing it close to its theoretical values. The elimination of the complex desorber column also increases the flexibility of the PP operation in response for market dynamics. A case-study for Sydney-Australia shows that in comparison with SPCC methodology, this state-of-the-art approach could notably improve the economics of the process and reduce the size of solar collector field (SCF).

Heat collector elements or solar receiver tubes are a key element in the development and performance of parabolic trough collector technology. They are responsible to collect solar energy and to transfer the heat collected to the heat thermal fluid. Main challenges to be met in the future are to increase durability and to reduce cost and maintenance. In order to increase durability, vacuum maintenance is the major challenge because thermal losses and selective absorber stability are directly dependent on vacuum level. Selective absorber thermal stability, both in vacuum and air, has to be improved to raise operation temperature in solar thermal plants and in this way, to increase efficiency and to minimize damage if vacuum is lost.

An experimental investigation on the use of nanofluids as working fluids and direct absorbers in a full-scale concentrating collector is presented. The nanofluid consists of a suspension of single wall carbon nanohorns in distilled water with a concentration of 0.02 g L−1. The thermo-physical properties are the same as those of the base fluid, but the presence of carbon nanoparticles greatly enhances the optical characteristics. A direct absorption receiver has been designed and set up to investigate the capability of the nanofluid to absorb the concentrated sunlight. The receiver exhibits a flat geometry and has been designed for installation on an asymmetric parabolic trough, where the concentrated solar flux locally reaches 100 kW m−2 under clear-sky conditions. Results show that the application of a carbon nanohorn-based nanofluid in a concentrating collector displays an efficiency comparable to that obtained with a surface receiver tested in the same system. However, such performance is not maintained for a long time because of lack of stability of the absorbing fluid.

The majority of parabolic trough concentrating solar power plants consist of an indirect system where the heat transfer fluid (typically synthetic oil) exchanges energy with a secondary circuit which is connected to the power cycle. Synthetic oil has a technical limitation by the maximum operating temperature. This results in the search for new fluids. On the other hand, with the aim of having energy when there is no sun shining, it has increased the use of thermal storage. Thermal energy storage systems are composed of molten salts and presents higher operating temperatures than synthetic oil. Thus, direct systems, in which thermal storage and heat transfer fluid are unified and normally molten salts, emerge to improve the power cycle performance. To determine the future potential of direct systems, this paper evaluates the environmental damage of two types of molten salts and synthetic oil in order to decide whether the use of salts is better than synthetic oil, from an environmental point of view by using the Life Cycle Assessment (LCA) techniques. LCA results showed greater impacts in the syntheticoil case than the molten salts Publicado

This chapter describes the state of the art of working fluids for parabolic trough collectors, starting with thermal oil as the option already implemented in most of the commercial parabolic trough plants, and then continuing with alternative working fluids that could lead to significant cost reduction and/or overall increase in plant efficiency. Three alternative working fluids are analyzed in this chapter: (1) water/steam (the so-called direct steam generation technology); (2) molten salts; and (3) pressurized gases. Thermo-hydraulic aspects, cost-related issues, and open questions associated with the use of these three alternative working fluids are dissected in this chapter, together with the current status of associated technologies. Since pressure drop in the solar field piping and heat transfer in the receiver tubes are key issues because of their impact on solar field pumping power and thermal stress in the receivers these two parameters are analyzed for each working fluid. This analysis is completed with a proposal of research and development activities that should be undertaken to fully clarify the technical and operational feasibility of these three innovative working fluids.

A simulation procedure has been developed to predict the performance of a concentrating solar power plant with direct steam generation (DSG) technology. A detailed modelling of the DSG solar field was conceived for both parabolic troughs (PTC) and linear Fresnel collectors within an integrated Octave-TRNSYS® environment. Predictions from this model were compared with published operational data of the first pre-commercial 5 MW DSG solar power plant, designed within the INDITEP project. Attention was paid to the plant performance under two different operation modes, i.e. “fixed” or “sliding” steam turbine inlet pressure.

The Parabolic Trough (PT) is the most used concentrator in CSP (Concentrated Solar Power). However, this concentrator technology is facing a significant challenge to increase its overall efficiency and cost-effectiveness. Meanwhile, other low-cost solutions such as Fresnel concentrators are also being perceived as potentially attractive. In order to achieve the lower cost goal, new optical solutions can be considered, in parallel with improvements coming, for instance, through the use of new materials or manufacturing solutions. But conventional PTs can still be improved to yield, for instance, higher concentration values, a possible starting point for higher conversion efficiency. These new solutions, in turn, can also be useful for other technologies and applications (Fresnel Concentrators, Central Tower Receivers, etc.). However it is easier to develop and test these solutions in conjunction with parabolic primaries (continuum primary). And that is the topic of this paper: to present a new Compound Elliptical-type Concentrator for a parabolic primary with a tubular receiver. A comparison is made between this new concentrator and two other concentrators (a conventional PT concentrator and a XX SMS (Simultaneous Multiple Surface) concentrator), as well as a calculation of the total amount of collected energy (kW h) for a particular location, Faro (Portugal). The paper ends with a discussion of the results obtained, their impact and possible applications in the future.

The employment of parabolic trough solar power plants (PT-CSP) for electrical power and process heat generation is one of the most promising technologies for carbon free energy production. The selection of thermal fluids, both for the heat transfer (heat transfer fluid, HTF) and the storage (heat storage material, HSM), is a crucial point for increasing CSP efficiency and cost effectiveness. In this paper two different PT-CSP configurations, both presenting a double tanks storage system, are compared. In particular, two different medium size (50 MWe) plant schemes, presenting two different working fluids as HTF, are described and analysed. In the first scheme a “binary” molten salt mixture, composed of sodium and potassium nitrate, is considered, while, in the second one, the employment, as HTF, of a “ternary” mixture, consisting of sodium potassium and lithium nitrates, is investigated. In both cases, the binary mixture is used for thermal storage (HSM). The first scheme represents the configuration developed by ENEA and already used for the Archimede plant in Priolo Gargallo (Sicily-Italy). The second one is an innovative proposal, which aims to improve CSP plants performances and to reduce operating costs. In particular, since the ternary mixture has a considerably lower freezing temperature than the binary one, this solution allows to keep the system at a lower temperature overnight, so reducing thermal energy losses. In first instance, it is necessary to characterize the binary and ternary mixtures respect to their thermo-physical features. The two CSP configurations are then sized and, by a techno/economic evaluation, compared with respect to the calculated unit cost of electricity production.

Solar thermal power plants use the Sun as a heat source. In order to generate a high enough temperature for a power plant, solar energy must be concentrated. In a solar thermal power plant this is normally achieved with mirrors. Estimates for global solar thermal potential indicate that it could more than provide for total global electricity needs. There are three primary solar thermal technologies based on three ways of concentrating solar energy: solar parabolic trough plants, solar tower power plants, and solar dish power plants. The mirrors used in these plants are normally constructed from glass, although other techniques are being explored. Power plants of these types use solar heat to heat a thermodynamic fluid such as water in order to drive a thermodynamic engine; for water this will be a steam turbine. Solar thermal power plants can have heat storage systems that allow them to generate electricity beyond daylight hours.

Concentrating solar power plants projects have been rapidly increasing over the last few years driven by the advances in the solar technology. The operational issues associated with the variable nature of solar energy could be overcome by integrating the solar input into fossil-fuelled power plants. In this paper solar energy is added to the bottoming part of a state-of-the-art three pressure level natural gas combined cycle and parabolic trough, linear Fresnel and solar tower technologies are considered in the search for the optimum integration. Detailed models of the combined cycle and solar field are built in the Thermoflex® environment to evaluate the performance of different integrated solar combined cycle system configurations. Results show how the placement of solar heat addition affects the heat absorption in the heat recovery steam generator and, in turn, the overall system performance. Unlike solar-only power plants which call for the highest temperature concentrating solar technologies to maximize thermal efficiency, the best integration is obtained here using moderate temperature concentrating solar technologies which enable a significant reduction of the heat transfer irreversibility in the heat recovery steam generator. Accordingly, high solar radiation-to-electricity conversion efficiencies approaching 30% are achieved using well-established solar technologies.

This paper describes a transient infrared thermography heat loss measurement method for parabolic trough receiversand its development under laboratory conditions. The method is designed for future field measurements and represents a complementary approach to steady-state heat loss measurement methods. The receiver specific heat loss is determined by applying a thermal excitation to the absorber tube and by measuring both the absorber and glass temperature response signals with infrared pyrometers. These transient signals are processed to derive a mean absorber temperature, a mean glass temperature, an amplitude ratio and a phase shift at a mean air temperature. Temperature signals are used to identify receiver thermal properties with the help ofanumerical heat transfer model coupled to a parameter identification algorithm. Parabolic trough receivers with distinct absorber coating and annulus properties have been tested with two different transient excitation profiles, i.e. sinusoidal and ramp-and-hold signals. The identified receiver thermal properties have been compared to steady-state heat loss experiments conducted withDLR THERMOREC test bench.The observed specific heat loss deviations between steady-state and transient laboratory measurements respectively range from 2% to 4% for evacuated receiverswith selective coating and from 1% to 9% for receivers with black painted absorbers.

A great interest has recently arisen for the sustainable supply of energy and fresh water, due to the growing demand from developing countries. Facing this demand by traditional technologies implies evident risks related with the high cost of fossil fuels and their environmental impact. Then, alternative solutions based on the use of renewable sources and innovative technologies must be considered. In this paper a renewable polygeneration system is examined, which includes a solar field based on parabolic trough photovoltaic/thermal collectors, a biomass heater, an absorption chiller and a Multiple Effect Distillation desalination unit. Plant operation under dynamic conditions has been analysed in previous papers; in this paper an exergetic and exergoeconomic analysis is carried out. The exergetic analysis is intended to identify the steps that mostly affect the overall plant exergy efficiency, so as to propose possible improvements. The exergoeconomic cost accounting is aimed at assigning a monetary value to each energy or material flow, thus providing a rational basis for price assignment. Both the exergetic and exergoeconomic analyses are applied to integral values of energy flows, comparing the results obtained in the summer and winter season. Finally, economic viability of the system in different context scenarios is discussed.