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A global transition towards more sustainable production and consumption systems is underway. This transition process is particularly visible in energy systems, where modern renewables, majorly solar PV and wind power, accounted for around 10 % of global power production in 2020. It is widely believed that the transition to a low carbon economy would inevitably increase energy storage requirement to a significant extent in the near future. In this context, concentrated solar power (CSP) technologies are seen to be one of the most promising ways to generate electric power in coming decades. To reduce the cost of power generation from CSP technologies, over 1000 articles have been published in the last five years, and it is necessary to observe the overall research and technological advancements in this sector which is missing in the current literature. To bridge this gap, this work presents a comprehensive review on the actual state of all major components of cutting-edge CSP technologies and condenses all the available information and categorizes them considering the main functional parts and remarking the current research progress in each part as well as the future challenging issues. It intends to understand and explain the foundations of the innovative concepts, future research directions and strategies developed over the past 10 years to tune the engineering and thermal sciences of concentrated solar power. It is evident that the cost has come down, however to make the cost of CSP technology at par with other renewable power sources, there are multiple challenges especially in water consumption, materials design, and receiver subsystems. Each of these challenges is discussed in detail and suggestions are presented for addressing the challenges. The information and insights presented in this detailed review study is expected to serve as a good resource for practicing engineers and researchers intending to undertake their research on this subject. [ABSTRACT FROM AUTHOR]

In recent years, rigorous research has been carried out on the use of membrane contactors to design compact absorbers for absorption cooling systems and to extend their use in small scale applications. Moreover, the use of new working fluid mixtures has been suggested for the absorption cooling systems to cope with the limitations and problems associated with the conventional working fluid mixtures. In this study, water/(LiBr + LiI + LiNO 3 + LiCl) with mass compositions in salts of 60.16%, 9.55%, 18.54% and 11.75%, respectively, and water/(LiNO 3 + KNO 3 + NaNO 3 ) with mass compositions in salts of 53%, 28% and 19%, respectively, were investigated for air-cooled and multi-stage high temperature absorption cooling systems, respectively. Results show that a 25% increase in the absorption rate can be achieved by using water/(LiBr + Li + LiNO 3 + LiCl) when compared to water/LiBr at air-cooling thermal conditions. Furthermore, an absorption rate as high as 0.00523 kg/m 2 s is achieved when the water/(LiNO 3 + KNO 3 + NaNO 3 ) working fluid mixture is used in the membrane-based absorber of the third stage of a triple effect absorption cooling cycle. In addition, the pressure drop percentage in the case of water/(LiNO 3 + KNO 3 + NaNO 3 ) working fluid mixture is significantly lower than the water/LiBr and water/(LiBr + LiI + LiNO 3 + LiCl) working fluid mixtures because of the higher operating pressure. [ABSTRACT FROM AUTHOR]

The differential heat of dilution data are estimated theoretically using Duhring's diagrams for water/LiBr, water/(LiBr + LiI + LiNO 3  + LiCl) with mass compositions in salts of 60.16%, 9.55%, 18.54% and 11.75%, respectively, and water/(LiNO 3  + KNO 3  + NaNO 3 ) with mass compositions in salts of 53%, 28% and 19%, respectively, as these can be potentially utilized as working fluids in absorption cooling systems. The differential heat of dilution data obtained were correlated with simple polynomial equations for the three working fluids as a function of the solution concentration and temperature. The results showed that the differential heat of dilution of the non-conventional working fluid mixtures is lower than that of water/LiBr at typical operating temperature and concentration of interest in absorption cooling cycles employing these working fluid mixtures. The correlations developed could be useful in predicting the differential heat of dilution value while performing heat and mass transfer analyses of these potential non-conventional working fluid mixtures in absorption cooling systems. [ABSTRACT FROM AUTHOR]

Absorption cooling systems employing membrane based components provide an interesting opportunity to use the technology for small scale applications. Steady-state heat and mass transfer analyses of a water-lithium bromide membrane based absorber are performed. CFD (computational fluid dynamics) tool ANSYS/FLUENT 14.0 is used to perform the simulation and investigate the behaviour of the heat and mass transfer mechanisms at local levels in the channels. Results show that the solution film thickness is an important parameter which significantly affects the mass transfer mechanism. It was observed that the absorption rate increased by a factor of 3 when the solution channel thickness was reduced from 2 mm to 0.5 mm. In addition, the absorption rate was increased by a factor of 2.5 when the solution inlet flow velocity was increased from 0.00118 m/s to 0.00472 m/s. The solution film thickness and velocity can be independently controlled in plate-and-frame membrane based absorbers. Therefore to design a compact and efficient plate-and-frame membrane absorber with water as a refrigerant, an optimum value of 0.5 mm for the solution channel thickness is suggested and a solution inlet velocity of about 0.005 m/s is recommended to achieve high absorption rates with acceptable pressure drop along the solution channel. [ABSTRACT FROM AUTHOR]

The use of membrane contactor technology is well-known in the process industry and can be employed in many important fields; such as separation and absorption processes, membrane distillation, pervaporation, biotechnology, food industries etc. In recent years, research has been carried out regarding the use of membrane contactors in the components of absorption refrigeration systems. The use of membrane contactors makes it realizable to design compact components with improved heat and mass transfer. Heat and mass transfer performance of the components is significantly enhanced due to the higher area to volume ratio available. Membrane based absorber and desorber allow the reduction in size of the absorption refrigeration systems to a great extent and thus absorption refrigeration technology can be used in transport and small scale applications. In this paper, the applications of membrane contactors in absorption refrigeration systems are reviewed. The application of membrane contactors in the components of absorption refrigeration systems, the configurations of refrigeration cycles that employ membrane contactors and the characteristics of the membrane contactors used in absorption refrigeration systems are all reviewed in detail. Information is collected on the choice of working fluid mixture to be used in absorption refrigeration systems that use membrane based components and the compatibility of working fluid mixtures with the membrane contactor material is discussed. The significance and limitations of using membrane contactors in absorption refrigeration systems is included in this paper. [ABSTRACT FROM AUTHOR]

• Integration of four novel sCO 2 cycles with coal-fired power plant. • Efficiency of sCO 2 cycle is higher than steam Rankine cycle by 3–4%pts. • sCO 2 cycles can reduce the cost of electricity by 6–8% than steam Rankine cycle. • Increasing turbine inlet temperature by 140 °C increases efficiency by 3–4%pts. • Increasing turbine inlet temperature doesn't show reduction in cost of electricity. Supercritical carbon dioxide (sCO 2) cycles can achieve higher efficiencies than an equivalent steam Rankine cycle at higher turbine inlet temperatures (>550 °C) with a compact footprint (tenfold). sCO 2 cycles are low-pressure ratio cycles (~4–7), therefore recuperation is necessary, which reduces the heat-addition temperature range. Integration of sCO 2 cycles with the boiler requires careful management of low-temperature heat to achieve higher plant efficiency. This study analyses four novel sCO 2 cycle configurations which capture the low-temperature heat in an efficient way and the performance is benchmarked against the state-of-the-art steam Rankine cycle. The process parameters (13–16 variables) of all the cycle configurations are optimised using a genetic algorithm for two different turbine inlet temperatures (620 °C and 760 °C) and their techno-economic performance are compared against the advanced ultra-supercritical steam Rankine cycle. A sCO 2 power cycle can achieve a higher efficiency than a steam Rankine cycle by about 3–4% points, which is correspond to a plant level efficiency of 2–3% points, leading to cost of electricity (COE) reduction. Although the cycle efficiency has increased when increasing turbine inlet temperature from 620 °C to 760 °C, the COE does not notably reduce owing to the increased capital cost. A detailed sensitivity study is performed for variations in compressor and turbine isentropic efficiency, pressure drop, recuperator approach temperature and capacity factor. The Monte-Carlo analysis shows that the COE can be reduced up to 6–8% compared to steam Rankine cycle, however, the uncertainty of the sCO 2 cycle cost functions can diminish this to 0–3% at 95% percentile cumulative probability. [ABSTRACT FROM AUTHOR]

A global transition to sustainable energy systems is underway, evident in the increasing proportion of renewables like solar and wind, which accounted for 12 % of global power generation in 2022. The shift to a low-carbon economy will likely require a substantial increase in energy storage in the near future. In this context, concentrating solar power (CSP) is viewed as a promising renewable energy source in the coming decades. However, high generation costs compared to other renewable technologies remain a key barrier inhibiting wider deployment of CSP. Compared to solar PV and onshore wind alternatives, CSP cannot currently compete on the levelized cost of electricity (LCoE). This review provides a comprehensive overview of the vital economic factors and considerations for large-scale CSP expansion. The current state of the market reveals about 8 GW of installed global CSP capacity in 2023, with rapid growth occurring in China, Chile, South Africa and the Middle East. Key economic parameters discussed in this study include capital costs, capacity factors, operating expenses and LCoE. Installation costs for CSP declined by 50 % over the past decade, falling to the current range of $3000–11000 per kW. Adding 6–15 h of thermal energy storage at $20–60 per kW is now considered economical. Capacity factors increased from 30 % to more than 50 % (depending on location) through larger storage capacities and higher operating temperatures. Operations and maintenance costs now range from $12–15 per kW-year. The resulting global weighted average LCoE for CSP plunged 68 % from $0.31 per kWh in 2010 to $0.10 per kWh in 2022. Ongoing innovations in materials, components integrated systems and optimization can further reduce capital expenditures, enhance performance and decrease LCoE. However, appropriate incentives and financing mechanisms remain vital to support continued CSP technology maturation and cost reductions. With its inherent dispatchability and storage capabilities, CSP can become a cost-competitive renewable energy source, but design optimizations and accurate economic appraisals are imperative for CSP to achieve its vast sustainability potential. • Global weighted average electricity capacity factors for CSP plants rose 66 % from 2011 to 2021. • Global weighted average LCoE for CSP fell 68 % from $0.31/kWh in 2010 to $0.10/kWh in 2022. • Capital costs for CSP fell 50 % in the last decade to $3000–11000/kW. • Adding 6–15 h of thermal storage at $20–60/kW is now considered economical. [ABSTRACT FROM AUTHOR]

• Identified the optimal GT pressure ratio requirements for four sCO 2 cascaded cycles. • Pressure ratio of a sCO 2 cycle at maximum efficiency is higher than a steam cycle. • Multi-objective optimisation is done to compare sCO 2 cycles on equivalent basis. • Performance prediction maps were produced to help selecting an optimal GT. • A new sCO 2 cycle is proposed that improves efficiency by 1.4 percentage points. A closed-loop, indirect, supercritical Carbon Dioxide (sCO 2) power cycle is attractive for fossil-fuel, solar thermal and nuclear applications owing to its ability to achieve higher efficiency, and compactness. Commercial Gas Turbines (GT's) are optimised to yield maximum performance with a conventional steam Rankine cycle. In order to explore the full potential of a sCO 2 cycle the whole plant performance needs to be considered. This study analyses the maximum performance and cost of electricity for five sCO 2 cascaded cycles. The plant performance is improved when the GT pressure ratio is considered as a design variable to a GT to optimise the whole plant performance. Results also indicate that each sCO 2 Brayton cycle considered, attained maximum plant efficiency at a different GT pressure ratio. The optimum GT pressure ratio to realise the maximum cost reduction in sCO 2 cycle was higher than the equivalent steam Rankine cycle. Performance maps were developed for four high efficient cascaded sCO 2 cycles to estimate the specific power and net efficiency as a function of GT turbine inlet temperature and pressure ratio. The result of multi-objective optimisation in the thermal and cost (c$/kWh) domains and the Pareto fronts of the different sCO 2 cycles are presented and compared. A novel sCO 2 cycle configuration is proposed that provides ideal-temperature glide at the bottoming cycle heat exchangers and the efficiency of this cycle, integrated with a commercial SGT5-4000F machine in lieu of a triple-pressure steam Rankine cycle, is higher by 1.4 percentage point. [ABSTRACT FROM AUTHOR]

The new challenge of the European Commission is to limit water consumption in Concentrating Solar Power (CSP) plants, especially significant in the cooling process. Hybrid cooling systems are presented as a potential solution to achieve water consumption reduction since they also avoid a high penalty of efficiency loss in the power block. In this work, a hybrid cooling pilot plant installed at Plataforma Solar de Almería is evaluated experimentally. The system has been tested under different ambient and operating conditions to analyze their influence on the water and electricity consumption. The results reveal that significant water savings were achieved in comparison with the conventional only-wet configuration. Concretely, a maximum water consumption saving of 67% was found at high ambient temperatures (between 25 and 30 °C) and for a thermal load of 80% when a hybrid configuration was used. The optimal operating strategies that achieve a tradeoff between low water and electricity consumption have been identified by two efficiency indexes: the specific electricity and water consumption. The parallel configuration was the optimal one in most of the cases. At high ambient temperatures and 80% thermal load, the electricity and water consumptions of this configuration were 0.033 kW e /kW th and 0.071 L/kW th , respectively. • Test campaign to investigate the optimal configurations of a hybrid cooler. • Trade-off between water and electric energy consumption under several conditions. • Specific electricity consumption and specific water consumption for the evaluation. • Maximum water consumption saving of 67% for parallel configuration split ratio 25%. • Maximum electricity reduction of 59% for parallel configuration split ratio 50%. [ABSTRACT FROM AUTHOR]

Integration of thermal energy storage with concentrated solar power (CSP) plant aids in smoothing of the variable energy generation from renewable sources. Supercritical carbon dioxide (sCO 2) cycles can reduce the levelised cost of electricity of a CSP plant through its higher efficiency and compact footprint compared to steam-Rankine cycles. This study systematically integrates nine sCO 2 cycles including two novel configurations for CSP applications with a two-tank sensible heat storage system using a multi-objective optimisation. The performance of the sCO 2 cycles is benchmarked against the thermal performance requirement of an ideal power cycle to reduce the plant overnight capital cost. The impacts of the compressor inlet temperature (CIT) and maximum turbine inlet temperature (TIT) on the cycle selection criteria are discussed. The influence of the cost function uncertainty on the selection of the optimal cycle is analysed using Monte-Carlo simulation. One of the novel cycle configurations (C8) proposed can reduce the overnight capital cost by 10.8% in comparison to a recompression Brayton cycle (C3) for a CIT of 55 °C and TIT of 700 °C. This work describes design guidelines facilitating the development/selection of an optimal cycle for a CSP application integrated with two-tank thermal storage. • Optimisation of 9 sCO 2 cycles (2 novel) integrated with CSP and sensible heat TES. • Techno-economic evaluation of impact of heat addition temperature difference (ΔT). • Maximum cycle efficiency away from the optimal heat addition ΔT increases TES cost. • Increasing turbine inlet temperature from 600 to 700 °C increases overnight cost. • Novel cycle reduces the overnight capital cost by 10.8% over recompression cycle. [ABSTRACT FROM AUTHOR]

• Off-design Pareto fronts of sCO 2 cycle using multi-objective optimisation approach. • Storage capacity reduces by 25% at 55 °C compressor inlet temperature (design = 42 °C). • Off-design compressor inlet pressure estimation method to maximise efficiency. • Capacity factor increases by 10.8% when operating the plant in maximum power mode. • Number of start-ups reduce by about 50% when operating in maximum efficiency mode. Supercritical Carbon Dioxide (sCO 2) cycles can achieve higher efficiency compared to steam-Rankine or Air-Brayton cycles, therefore they are promising for concentrated solar power applications. Although sCO 2 cycles show higher design efficiency, the off-design efficiency is highly sensitive to the ambient conditions, impacting the power block net-power and heat input. In the present work a recompression sCO 2 cycle is connected to a central-tower solar field with two-tank thermal storage delivering molten chloride salt at 670 °C. The temperature of the molten-salt exiting from the power block and returning to the cold storage tank increases by 46 °C with respect to the design value when the compressor inlet temperature is raised by 13 °C relative to the design condition of 42 °C, which implies that the capacity of the thermal storage reduces by 25%. The main focus of this work is to investigate the off-design performance of a sCO 2 recompression cycle under variable ambient temperature, molten-salt inlet temperature and molten-salt flow rate. Multi-objective optimisation is carried-out in off-design conditions using an in-house code to explore the optimal operational strategies and the Pareto fronts were compared. Since the power cycle can either be operated in maximum power mode or maximum efficiency mode, this study compares these two operational strategies based on their annual performance. Results indicate that the capacity factor of the concentrated solar power can be increased by 10.8% when operating in maximum power mode whilst the number of start-ups is reduced by about 50% when operating in maximum efficiency mode. [ABSTRACT FROM AUTHOR]