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Abstract To lower the cost of electricity produced, advanced high-efficiency power cycles operating at temperatures above 600 °C (such as the supercritical CO 2 Brayton cycle) are presently being developed for use in both nuclear and concentrating solar power (CSP) plants. Incorporating thermal energy storage into CSP plants allows renewable energy to be generated while simultaneously providing reliability and stability to the grid. Sensible energy storage using molten nitrate salts is used in the majority of CSP plants. However, nitrate salts decompose at around 600 °C, hence an alternative storage medium is required to support the development of next generation high-efficiency CSP plants. Because of practical experience with molten salt storage in the two-tank configuration in industry, continuing to use fluid media is an attractive option, although thermal storage is also possible with other types of storage media (e.g. solids and phase change materials). This paper critically reviews options for energy storage in fluids that are stable over 600 °C. The focus is on three alternative molten salts — fluorides, chlorides and carbonates — which are assessed based on their thermophysical properties and cost. A brief review of liquid metal and molten glass storage options is included for completeness. Corrosion of containment materials is an important consideration in the choice of storage media, because if exotic materials are required, the cost of the storage tanks can dominate the overall storage cost. Therefore, this paper includes a summary of the main corrosion issues relating to containment of the more promising storage fluids considered herein, identifying possible tank materials and corrosion mitigation options. Graphical abstract fx1 Highlights • Storage media stable at > 600 °C are needed for advanced concentrating solar plants. • Carbonate, chloride and fluoride molten salt mixtures are the main candidates. • Carbonate and fluoride salts have attractive specific heat capacity but high cost. • Corrosion is a major challenge for all three salts, particularly for fluoride salts. • Research trends favour chlorides due to low cost and suitable thermal properties. [ABSTRACT FROM AUTHOR]

Concentrating solar power (CSP) seems to be a promising solution for rural electrification in Sub-Saharan Africa. Small scale CSP plant appears to be most appropriate because it is suitable to the needs of rural communities: most of components can be found to be of low cost in the African market and there are available qualified local human resource to build the systems. A state of art of small scale CSP plants in the range of 1–500 kW e are reviewed in this paper to showcase previous and current works undertaken throughout the world. 35 small scale CSP plants are identified and reviewed in the paper. Technical analysis is conducted on the identified plants to understand their operating principles. The technical analysis highlighted reasons behind the choices made for every component from the solar field to the power block. [ABSTRACT FROM AUTHOR]

Abstract: Middle East and North Africa (MENA) countries present abundant solar potential, which to some extent has been exploited for electricity production. However, the largest part of this potential remains still unexploited. The scope of this paper is to present the best practices in exploiting solar energy in selected MENA countries. First the general structure of energy market related to Renewable Energy Sources (RES) for each analyzed country is presented. Then the exploitation of solar energy via PVs with special focus to the achievements in rural electrification, which could be used as a paradigm for other countries with similar problems, is displayed. MENA countries are promising for the wide application of concentrating solar plants (CSP), as recent research has shown, and some interesting applications in this area, also presented in this paper, have started being implemented. [Copyright &y& Elsevier]

Grid electricity generation in Nigeria has been unstable for a long time now. With respect to her continued dependence on oil and gas and seasonal variations on water level for hydropower, immediate reliable and steady electricity generation in the country is not guaranteed. Incorporating alternative source of energy like solar is a solution. Solar Chimney technology is not yet technically and economically mature, as investment on it is still low, thereby posing more financial risks at least at the megawatt capacity. Photovoltaic and Solar Thermal technologies are technically and economically more established, but they can only ensure 24-h power supply with the aid of energy storage systems. Solar thermal value addition is on its propensity for thermal energy storage and hybridization with liquid fuels at commercial capacity. Hence, due to technology advancement and the country's high direct normal irradiation potential, concentrating solar power is the more suitable solar power technology for commercial electricity generation in Nigeria. In this paper, concentrating solar power technologies are analysed under operational, environmental and social conditions in Nigeria using data from desktop survey to determine the most suitable technology for solar thermal electric power plant. It is observed that the technical maturity of parabolic trough concentrator distinguishes it for preference to all other technologies and would exert moderate pressure on land requirement even though, it is the most expensive and water demanding technology. In terms of unit cost of electricity and water usage capabilities, parabolic dish concentrator is least expensive and uses least water but lacks proven commercial application. Solar tower is technically simpler and possesses better thermodynamic properties than the rest but its low installed capacity increases its financing risk. Hence, the trough system is the most suitable for immediate and medium term projects given its proven technology maturity and flexible financing mechanism. [ABSTRACT FROM AUTHOR]

Concentrating solar power (CSP) plants make use of the renewable and inexhaustible solar energy to produce electricity. Limited by the scarce water resources, CSP plants built in arid areas choose Natural Draft Dry Cooling Tower (NDDCT) to remove waste heat. However, NDDCT suffers from low efficiency in hot summer days. To resolve this problem, inlet air spray-cooling is introduced to improve the performance of NDDCT. In the first part of this paper, the research progress focused on both the theoretical and experimental studies on NDDCT are summarized. Then, in the second part, the spray cooling system consisting of various kinds of spray nozzles are described. Various nozzles produce different spray patterns such as flat-fan, hollow cone, full cone and solid jet. These spray patterns are characterized by flow rate, pressure, mean droplet size and droplet size distribution. Furthermore, the mathematical models correlating the cooling tower performance with the droplet evaporation process are used to predict the spray cooling performance and are summarized here. Finally, predictive results are presented to evaluate the performance of the pre-cooling system. The results illustrate that the inlet air pre-cooling would improve the efficiency of NDDCT and thus reduce power generation loss under high-ambient air temperature conditions. More research should be conducted to develop a practical NDDCT-based spray cooling system for industrial applications. [ABSTRACT FROM AUTHOR]

The targeted transition towards an electricity system with low or even negative greenhouse gas emissions affords a chance to address other environmental concerns as well, but may potentially have to adjust to the limited availability of assorted non-fossil resources. Life cycle assessment (LCA) is widely recognized as a method appropriate to assess and compare product systems taking into account a wide range of environmental impacts. Yet, LCA could not inform the latest assessment of co-benefits and trade-offs of climate change mitigation by the Intergovernmental Panel on Climate Change due to the lack of comparative assessments of different electricity generation technologies addressing a wide range of environmental impacts and using a consistent set of methods. This paper contributes to filling this gap. A consistent set of life cycle inventories of a wide range of electricity generation technologies is assessed using the Recipe midpoint methods. The life-cycle inventory modeling addresses the production and deployment of the technologies in nine different regions. The analysis shows that even though low-carbon power requires a larger amount of metals than conventional fossil power, renewable and nuclear power leads to a reduction of a wide range of environmental impacts, while CO 2 capture and storage leads to increased non-GHG impacts. Biomass has relatively modest co-benefits, if at all. The manufacturing of low-carbon technologies is important compared to their operation, indicating that it is important to choose the most desirable technologies from the outset. [ABSTRACT FROM AUTHOR]

Thermal energy storage systems provide a means to store energy for use in heating and cooling applications at a later time. The storage of thermal energy allows renewable sources of energy to be stored if the time of demand does not coincide with the time of production. It also enables access to off-peak electricity tariffs offered during times of low electricity demand. Storage systems can be charged during the low-cost tariff period and provide heating or cooling later when required. This benefits consumers with lower electricity costs and power generators with demand levelling. Thermal energy storage systems predominantly store heat as sensible heat in a substance. However, during a phase change heat energy can be stored as latent heat. Phase change material (PCM) thermal storage systems can store a greater amount of thermal energy per unit volume than sensible heat storage systems. Historically a drawback of using PCMs as a storage medium has been the low rates of heat transfer. Heat transfer enhancement techniques studied have included the use of additional metallic material and increasing heat transfer surface area such as fins to improve heat transfer rates of the PCM. Although these techniques are effective, they add significant cost and reduce the compactness factor of the thermal energy storage system. Recent research has been conducted on heat transfer enhancement that makes use of moving or transporting the PCM. This method is not only effective for increasing the heat transfer; it is less expensive and maintains a high compactness factor for the thermal energy storage system. This review paper presents the different heat transfer enhancement techniques reported in the literature. It also summarises the research conducted on phase change storage systems where the PCM is moved in the storage system. [ABSTRACT FROM AUTHOR]

Direct steam generation in parabolic-trough collectors is considered a promising option for reducing the cost of electricity produced in solar thermal power plants. Indeed, the use of water instead of thermal oil allows reaching high temperature levels and reducing plant complexity. Furthermore, the integration of thermal energy storage system and the hybridization of the plant with a biomass boiler permit further cost reduction. This paper focuses on the historical and technological development of the direct steam generation concept and the thermoeconomic analysis of a hybrid direct steam generation-biomass power plant equipped with a thermal energy storage system. The exergy balance and cost balance equations have been applied to each component of the plant in four different operating modes that take into account the intermittency of the solar source. Exergy results show that the solar field requires further development in order to reduce associated irreversibilities. Finally, it was found that the integration of a thermal energy storage system and hybridization with a biomass boiler reduce the final cost of electricity to 17.36c€/kW h e . [ABSTRACT FROM AUTHOR]

The purpose of this review survey is to provide a literature compilation, updating materials reported in several review papers on solar-device soiling and mitigation approaches published over the past 5 years. The focus is on the period 2013–2015, but an updated listing is also provided for the year 2012 for completeness. This literature review also provides the first update for a periodic, single collation report on such publications proposed in this journal two years ago. This review presents a listing of the publications, their publication source, and some brief tabulated information to help guide the reader into the focus of each of the works. [ABSTRACT FROM AUTHOR]

Concentrating Solar Power (CSP) plants generate renewable electricity using the conversion of solar direct normal irradiation into thermal energy, then into mechanical work and electricity through the use of a thermodynamic cycle. Among the several available technologies, Direct Steam Generation (DSG), in which steam is generated directly in the absorber tubes of the solar field, and then directly fed to the turbine or thermal storage, holds interesting advantages. However, the steam generation system shows a difficult dynamic behavior which constitutes a challenge for the control system design. It is mainly due to the conjunction of the natural transient condition of solar irradiation and the presence of two-phase flow in the absorber tubes. This paper reviews the control methods of the DSG systems used in linefocus CSP. The control systems are either proposed in literature, or actually applied in currently running plants or prototypes, although an extensive description is difficult to obtain in the case of the latter. The control systems are classified according to which DSG operation mode they refer to. [ABSTRACT FROM AUTHOR]

There are two ways by which solar energy can be harnessed viz. solar Photo-Voltaic (PV) and Concentrating Solar Power (CSP). This paper focuses on the parameters required for the commissioning of solar power plants in India using these technologies. The key parameters have been identified through the literature review and discussion with the experts. The parameters thus obtained, are classified under PV and CSP technologies and then categorized into technical and economical parameters. A survey is conducted to understand the perceptions of Indian key players in the area of solar energy and to rank forty one identified parameters. Analysis of survey shows that location of the site and direct investment cost are the highest preferred technical and economical parameters respectively. The results of this study will help decision makers and policy makers of solar technologies in India. [ABSTRACT FROM AUTHOR]

Concentrating solar power plants represent a competitive option to produce electric power only if equipped with suitable thermal energy storage. Metal hydride material-based thermochemical hydrogen storage is a very attractive solution to store high temperature solar thermal energy. A literature review of some of the past and more recent investigations on using metal hydrides for thermal energy storage has been carried out. Based on findings from this review and new material property data, a preliminary material techno-economic analysis was performed to select the most promising candidate metal hydrides as well as to examine their behavior under different operating conditions. The performance was evaluated adopting simplified system models and the results were compared against the US Department of Energy targets including installed cost, exergetic efficiency, operating temperature and volumetric energy density. Selected sensitivity analyses for the most promising materials have also been carried out in order to evaluate the influence of solar plant and material properties on the overall system installed cost. Results demonstrated that the selected storage systems, based on currently available metal hydride high temperature materials (i.e. NaMgH3, TiH2 and CaH2), are able to achieve and exceed many of the targets such as volumetric energy density (25kWhth/m3) and operating temperature (600°C). Material modifications as well as heat exchange system improvements are also discussed in the paper, with the aim of reducing the overall thermal energy storage specific cost and helping to meet and exceed all of the targets. [ABSTRACT FROM AUTHOR]

Abstract: The use of central receiver system (CRS) for electricity production promises to be one of the most viable options to replace fossil fuel power plants. Indeed, research and development activities on its basic subsystems have been booming rapidly since 1980s. This paper reviews the most important studies on the major components of central receiver solar thermal power plants including the heliostat field, the solar receiver and the power conversion system. After an overview of Concentrating Solar Power (CSP) technology, current status and applications of the CRSs are highlighted. Next, a detailed literature survey of existing design comprising optical, thermal and thermodynamic analysis, and techniques used to assess components have been arranged. This is followed by experimental investigations in which design concepts are established. The last section contains recent subsequent improvement of such key components as heliostat, receiver and hybrid solar gas turbine that are boosting in many R&D activities merging international collaboration during the past 30 years. [Copyright &y& Elsevier]

Abstract: In this paper we first make a review of the past annual production of electricity and the cumulative installed capacity for photovoltaic (PV) and concentrating solar power (CSP) technologies. This together with the annual costs of PV modules and CSP systems allows us the determination of the experience curves and the corresponding learning rates. Then, we go over a rigorous exposition of the methodology employed for the calculation of the value of the levelized cost of electricity (LCOE) for PV and CSP. Based on this knowledge, we proceed to establish a mathematical model which yields closed-form analytical expressions for the present value of the LCOE, as well as its future evolution (2010–2050) based on the International Energy Agency roadmaps for the cumulative installed capacity. Next, we explain in detail how specific values are assigned to the twelve independent variables which enter the LCOE formula: solar resource, discount and learning rates, initial cost and lifetime of the system, operational and maintenance costs, etc. With all this background, and making use of a simple computer simulation program, we can generate the following: sensitivity analysis curves, graphs on the evolution of the LCOE in the period 2010–2050, and calculations of the years at which grid parities will be reached. These representations prove to be very useful in energy planning policies, like tariff-in schemes, tax exemptions, etc., and in making investment decisions, since they allow, for a given location, to directly compare the costs of PV vs CSP power generation technologies for the period 2010–2050. Among solar technologies, PV seems always more appropriate for areas located in middle to high latitudes of the Earth, while CSP systems, preferably with thermal storage incorporated, yield their best performance in arid areas located at relatively low latitudes. [Copyright &y& Elsevier]

Abstract: Limited fossil resources and severe environmental problems require new sustainable electricity generation options, which utilize renewable energies and are economical in the meantime. Concentrating solar power (CSP) generation is a proven renewable energy technology and has the potential to become cost-effective in the future, for it produces electricity from the solar radiation. In Turkey, the electricity demand is rapidly increasing, while the solar resources and large wasteland areas are widely available in the western and southeastern part of Turkey. To change the energy-intensive and environment-burdensome economical development way, Turkish government supports the development of this technology strongly. These factors altogether make Turkey a suitable country for utilizing CSP technology. In this paper, the potential of CSP in Turkey was studied and strategies to promote development of this technology were given. [Copyright &y& Elsevier]

Abstract: Limited fossil resources and severe environmental problems require new sustainable electricity generation options, which utilize renewable energies and are economical in the meantime. Concentrating solar power (CSP) generation is a proven renewable energy technology and has the potential to become cost-effective in the future, for it produces electricity from the solar radiation. In China, the electricity demand is rapidly increasing, while the solar resources and large wasteland areas are widely available in the western and northern part of China. To change the energy-intensive and environment-burdensome economical development way, Chinese government supports the development of this technology strongly. These factors altogether make China a suitable country for utilizing CSP technology. In this paper, the potential of CSP in China was studied and strategies to promote development of this technology were given. [Copyright &y& Elsevier]

The organic Rankine cycle (ORC) is an effective technology for power generation from temperatures of up to 400 °C and for capacities of up to 10 MW el. The use of solar irradiation for driving an ORC is a promising renewable energy-based technology due to the high compatibility between the operating temperatures of solar thermal collector technologies and the temperature needs of the cycle. The objective of this review paper is to present and discuss the operation principles of solar-ORC technology and the wide range of solar-ORC systems that have been studied in the literature. Various solar thermal technologies that can drive the ORC are investigated, such as the flat plate collector, evacuated tube collector, compound parabolic collector, parabolic trough collector, linear Fresnel reflectors, dish concentrators and solar towers. Both simulation studies and experimental investigations are included in the study. Hybrid systems and different thermal storage techniques are also examined in detail. Moreover, systems with ORC which produce many useful outputs such as cooling, heating and fresh water are studied because they present high sustainability indexes. The limitations of the technology are also highlighted, along with critical suggestions aimed at steering future research in this field. The final conclusions indicate that the development of trigeneration and polygeneration systems with ORC sub-systems is a promising avenue, not only for the future development of solar-ORC technology but also for the development of renewable and sustainable energy systems in a broader context. • Solar driven organic Rankine cycles are summarized and discussed in detail. • Concentrating and non-concentrating solar thermal systems are included. • Parabolic trough collector is the best solar technology for power production. • The use of solar organic Rankine cycles in polygeneration is a promising idea. • There is a need for conducting future experimental studies in a great scale. [ABSTRACT FROM AUTHOR]

Concentrating Solar Power (CSP) plants can make a significant contribution to renewable energy supply in many regions of the world. Several bottom-up engineering performance models for CSP plants have been developed. However, they require the capacity of the plant to be known. In whole-of-grid optimization models, the capacity of the plants is an optimization variable and therefore not known in advance. In this case, researchers have taken a simplified modelling approach that overestimated CSP performance, especially for low-DNI conditions. In this paper, we offer a novel density-based engineering modelling approach in which CSP performance is determined independently of the capacity of the power plant, and which can be used in whole-of-grid optimization models. We investigate a case study of the site of the new Aurora CSP project in Port Augusta, South Australia, to be one of the world's largest solar thermal power plants by 2020. Using a Geographical Information System (GIS)-grid representation of Australia, we compare CSP performance resulting from a simplified model with our new approach. • A novel density-based engineering modelling approach for Concentrating Solar Power (CSP) plants. • CSP performance is determined independently of the capacity of the power plant. • The approach can be used in whole-of-grid optimisation models. • We investigate the site of the new Aurora CSP project in Port Augusta, South Australia to be constructed by 2020. • The new approach is compared to the simplified description of CSP performance, using a GIS-grid representation of Australia. [ABSTRACT FROM AUTHOR]