Concentrated Solar Power: Actual Performance and Foreseeable Future in High Penetration Scenarios of Renewable Energies

Producción CientíficaAnalyses proposing a high share of concentrated solar power (CSP) in future 100% renewable energy scenarios rely on the ability of this technology, through storage and/or hybridization, to partially avoid the problems associated with the hourly/daily (short-term) variability of other variable renewable sources such as wind or solar photovoltaic. However, data used in the scientific literature are mainly theoretical values. In this work, the actual performance of CSP plants in operation from publicly available data from four countries (Spain, the USA, India, and United Arab Emirates) has been estimated for three dimensions: capacity factor (CF), seasonal variability, and energy return on energy invested (EROI). In fact, the results obtained show that the actual performance of CSP plants is significantly worse than that projected by constructors and considered by the scientific literature in the theoretical studies: a CF in the range of 0.15–0.3, low standard EROI (1.3:1–2.4:1), intensive use of materials—some scarce, and significant seasonal intermittence. In the light of the obtained results, the potential contribution of current CSP technologies in a future 100% renewable energy system seems very limited.Ministerio de Economía, Industria y Competitividad (Project FJCI-2016-28833)European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement No. 69128

Potential of heat pipe technology in nuclear seawater desalination

The official published version of this article can be found at the link below.Heat pipe technology may play a decisive role in improving the overall economics, and public perception on nuclear desalination, specifically on seawater desalination. When coupled to the Low-Temperature Multi-Effect Distillation process, heat pipes could effectively harness most of the waste heat generated in various types of nuclear power reactors. Indeed, the potential application of heat pipes could be seen as a viable option to nuclear seawater desalination where the efficiency to harness waste heat might not only be enhanced to produce larger quantities of potable water, but also to reduce the environmental impact of nuclear desalination process. Furthermore, the use of heat pipe-based heat recovery systems in desalination plant may improve the overall thermodynamics of the desalination process, as well as help to ensure that the product water is free from any contamination which occur under normal process, thus preventing operational failure occurrences as this would add an extra loop preventing direct contact between radiation and the produced water. In this paper, a new concept for nuclear desalination system based on heat pipe technology is introduced and the anticipated reduction in the tritium level resulting from the use of heat pipe systems is discussed

Techno-Economics of Hybrid NF/FO with Thermal Desalination Plants

Hybrid desalination technology is defined as any combination of thermal and membrane processes in seawater desalination systems. So far, the two technologies have evolved rather independently with some degree of competition. Traditionally, in co-generation market applications, thermal desalination has succeeded in establishing a stronghold where large capacities are needed, energy costs are low, and seawater quality is challenging. However, in recent years, membrane systems have also succeeded in grabbing a larger share of the world seawater desalination market, mainly as a result of progress made in membrane and energy recovery technologies. Realizing the potential benefits and challenges faced by both technologies on their own, designers have been looking for ways to synergize and combine the two technologies in optimum configurations, which promise to further reduce the total cost of seawater desalination

Site-Specific Research Conducted in Support of the Salton Sea Solar Pond Project - FY 1982 Report

The design and operation of a salt-gradient solar pond power plant at the Salton Sea presents problems not encountered at small research ponds that were built in the United States. The specific characteristics of the Salton Sea site and the desire to construct the pond using the local clay as a sealant represent major deviations from previous solar pond experience. The site-specific research in support of the plant design is described. The research activity included validation of the spectrophotometric light transmission measurement technique, a search for options for clarifying the turbid and colored water of the Salton Sea, development of water clarification specifications in terms common to industry practice, quantification of gas production from microbiological reactions in the ground, a determination of the combined effects of temperature and salinity on the permeation of the local clays, and a preliminary evaluation of material corrosion

New and renewable energy and environmental engineering

There is an acute scarcity of potable water in many parts of the world, and especially in most of the Middle East region. Important advances have been made in desalination technology but its wide application is restricted by relatively high capital and input energy costs, even when solar energy is used. Until recently, flat-plate solar collectors have usually been employed to distill water in compact desalination systems. Currently, it is possible to replace these collectors by the more advanced evacuated tube collectors, which are now available on the market at a similar price. The research which is concerned with the development of a novel small scale solar water desalination technology, consists of experimental and theoretical investigations of the operation of a multi stage solar still desalination system coupled with a heat pipe evacuated tube solar collector with an aperture area of about 1.7 m(^2). The multi stage still was tested to recover latent heat from the evaporation and condensation processes in each of its four stages. A number of experimental tests were carried out using a laboratory rig to investigate its water production capacity. Solar radiation (insolation) during a mid-summer day in the Middle East region was simulated by an array of 110 halogen flood lights. Computational Fluid Dynamics (CFD) modeling of the evaporation and condensation processes in one of the still's stages was conducted using FLUENT 6.2 software. The simulation results demonstrate the importance of the various parameters affecting the total production rate of the solar still and provide detailed information on the temperature distribution and condensate formation inside the solar still. However, it was found that the CFD technique at this stage does not provide accurate quantitative predictions and results obtained can be used only for qualitative analysis. Hence, the use of a lumped parameter mathematical model was preferred for analysis and design purpose. A lumped parameter model has been developed to describe the system's operation. It consists of a system of ordinary differential equations of energy and mass conservation written for each stage of the still. A MATLAB computer program was written to solve the system of governing equations to simulate the evaporation and condensation processes and the experimental results were used to validate numerical predictions. The experimental and theoretical values for the total daily distillate output were found to be closely correlated. The test results demonstrate that the system produces about 9 kg of clean water per day and has a distillation efficiency of 90%. The overall efficiency is 33% due to the presence of heat losses in the system. However, this level of efficiency is greater of that for conventional solar stills. Following the experimental calibration of the lumped parameter model, this was used for determination of rational design parameters of the still and it was demonstrated that the performance of the system could be considerably improved to produce 11 kg/m(^2) of water per day if the number of stages and evaporation area were 4 and 1 m(^2), respectively. A water quality analysis was performed for the distilled water and the levels of total dissolved solids, electrical conductivity and pH were well within the range defined by the World Health Organization guidelines for drinking water. An economic study was also conducted for the system and it was shown that the distilled water costs of 0.016 US$/litre with a payback period of 6 months in the Middle East region conditions. This research demonstrates, empirically and theoretically, the potential role in the field of solar desalination of the multistage solar still coupled to the evacuated tube solar collector. Not only is this system a promising new technology but it could prove to be particularly appropriate in remote and rural areas. Simultaneously this system also uses a completely clean energy source and contributes to tackling environmental pollution, global carbon emissions and climate change problems

Economical desalination processes in Qatar

The limited underground water resources and the dramatic increase of fresh water consumption in Qatar forced the government to seek alternative ways to compensate for the lack of fresh water resources. Unfortunately, most of the currently available alternatives are costly in terms of excessive fuel consumption; also they require large capital investment and high maintenance cost. Such plants currently produce over 98% of the total fresh water in Qatar. This ratio may increase to 100% in the next few years. The main aim of this work is to investigate the most viable water desalination processes, which can produce sufficient, and a continuous supply of fresh water with low operation and construction costs. Climatic conditions and solar radiation in Qatar have been studied and analysed to determine the performance of any potential solar system applicable to this country. A technical and economical investigation into the current and common desalination methods with particular emphasis on the three main desalination systems including multistage flash, multiple effect distillation and reverse osmosis were conducted and included. A comprehensive literature survey on various water desalination methods was undertaken. The current experimental program was confined mainly to one novel type of tilted tray solar still system, namely pyramid tilted tray solar still, which was developed to increase productivity by increasing the receiving surface area of the still (the absorber) in order to collect the optimum amount of solar radiation. Two types of cover have also been selected and tested in this work, namely pyramid and dome shapes. These tilted tray solar stills were designed and constructed on a small scale and have been tested under controlled laboratory conditions at the University of Hertfordshire. Various parameters, which are likely to effect the still performance have been investigated. These include water flow rate, spacing between cover and tray surface, glass thickness, insulation layer, and inlet water temperature. Finally, a comparison of the stills performance characteristics of the two shapes has been carried out. The laboratory experimental results of hourly production revealed that pyramid type solar still yield higher distilled water output results than the dome type. However, the use of the pyramid shape with tilted tray solar can lead to further increase in the still productivity by optimising the orientation and surface area of the still absorber. The field experimental results of pyramid solar still, which were conducted under local climate conditions of Qatar, indicated clearly that solar desalination can be a suitable economical option, particularly for remote areas, where the fresh water demand is low and water transport is expensive. Moreover, a theoretical model was employed to predict the effects on solar still performance under three various parameters under typical climatic conditions of Qatar; These include the thermal insulation layer, the water depth and wind speed. Due to the economical reasons the dual-purpose multistage flash process will remain for the foreseeable future the preferred process, when fresh water and electricity demands are growing concurrently and rapidly

Assessment of the Use of Solar Desalination Distillers to Produce Fresh Water in Arid Areas

Water is an important resource for human beings, yet there are inhabited places tormented by the scarcity of it. The present study is concerned with places where, seemingly, the best way to get water is through solar distillers. These places should have, typically, high values of solar irradiation and a lack of human and economic resources to build and operate complex equipment. A set of sites scattered around the world was chosen, and then the presumed productivity and thermal efficiency that solar distillers would have if they were installed at these places was calculated. The mathematical model used with this purpose assumes steady-state operation; the values of mass of water distilled and distiller efficiency were calculated for every hour, but the results presented are annual averages. Then, an economic study was made based on local costs of construction materials for the distillers, the workforce, and the prices of water to predict the payback time of solar distillers. Finally, a study on environmental impact, particularly in terms of greenhouse gas (GHG) emissions, was made to compare reverse osmosis (RO) with solar distillation. For the sites studied, typical values of annual water output are in the range of 414 dm3/m2, for Évora, up to 696 dm3/m2, for Faya Largeau; the minimum efficiency was found for Évora, as 11.5%, and the maximum efficiency was found for Tessalit, as 15.2%. Payback times are very high, regardless of the areas of the globe where solar distillers are implanted. Regarding GHG emissions, solar distillation is preferable to RO.info:eu-repo/semantics/publishedVersio

Renewable energy powered desalination in Baja California Sur, Mexico

Baja California Sur (BCS) is an arid sparsely populated coastal state in northwest Mexico. Population growth, agriculture and booming tourism have lead to severe overexploitation of underground aquifers and saline intrusion. This paper reviews the current water and energy situation in BCS. The state enjoys very high levels of solar radiation, typically above 5 kWh/m2/d, and the suitability of renewable energy powered desalination for BCS is discussed, including past efforts in BCS and present challenges for this technology

A review of acid recovery from acidic mining waste solutions using solvent extraction

This is the peer reviewed version of the following article: Uchenna Kesieme, Andreas Chrysanthou, Maurizio Catulli, and Chu Yong Cheng, ‘A review of acid recovery from acidic mining waste solutions using solvent extraction’, Journal of Chemical Technology and Biotechnology, (2018), which has been published in final form at https://doi.org/10.1002/jctb.5728. Under embargo until 1 July 2019. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.The minerals industry is increasingly being forced by regulatory and cost pressures to reduce the amount of liquid acidic waste they produce. This requires a strong focus on waste reduction by recycling, regeneration and reuse. Four mineral acids were examined for recovery from waste acidic solutions including H 2SO 4, HNO 3, HCl, and H 3PO 4. The selection of the optimal extractant for acid recovery was based on extraction, stripping and scrubbing efficiencies. The extractants suitable for the recovery of H 2SO 4 and HCl are in the order of TEHA > Cyanex 923 > TBP > Alamine 336. TEHA has the highest degree of acid extraction and stripping compared with Cyanex 923 and almost 99% of the acid can be stripped. Alamine 336 can extract higher acid (for H 2SO 4 and HCl systems) than Cyanex 923 and TBP. However loaded acid for Alamine 336 system cannot be stripped using water at 60°C. For the recovery of nitric and phosphoric acids from acidic waste effluents, TBP was the best option. This work clearly demonstrates that extractant suitable for acid extraction may not be suitable for its recovery. However such extractant may be applied for the removal of acid from any waste acidic solution sacrificing the back extraction of the loaded acid. The effective implementation of options for acid recovery was examined to improve sustainability in the mineral industry.Peer reviewe

Recent progress on flat plate solar collectors equipped with nanofluid and turbulator: state of the art.

This paper reviews the impacts of employing inserts, nanofluids, and their combinations on the thermal performance of flat plate solar collectors. The present work outlines the new studies on this specific kind of solar collector. In particular, the influential factors upon operation of flat plate solar collectors with nanofluids are investigated. These include the type of nanoparticle, kind of base fluid, volume fraction of nanoparticles, and thermal efficiency. According to the reports, most of the employed nanofluids in the flat plate solar collectors include Al2O3, CuO, and TiO2. Moreover, 62.34%, 16.88%, and 11.26% of the utilized nanofluids have volume fractions between 0 and 0.5%, 0.5 and 1%, and 1 and 2%, respectively. The twisted tape is the most widely employed of various inserts, with a share of about one-third. Furthermore, the highest achieved flat plate solar collectors' thermal efficiency with turbulator is about 86.5%. The review is closed with a discussion about the recent analyses on the simultaneous use of nanofluids and various inserts in flat plate solar collectors. According to the review of works containing nanofluid and turbulator, it has been determined that the maximum efficiency of about 84.85% can be obtained from a flat plate solar collector. It has also been observed that very few works have been done on the combination of two methods of employing nanofluid and turbulator in the flat plate solar collector, and more detailed work can still be done, using more diverse nanofluids (both single and hybrid types) and turbulators with more efficient geometries