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To expand the functions of building window and enhance its thermal performance, a novel CdTe multi-layer PV ventilated window system integrated with phase change material (PCM) was proposed. The novel window system was fabricated, constructed and installed on the south façade of a building room and several groups of seasonal experiments were conducted under different operating modes. Electrical, thermal and daylighting performance of the system were investigated. Main conclusions are: (1) For the heating season mode experiment, daily total electricity generation (E P V ) and average electrical efficiency (η e) were 0.383 kWh and 7.39 %. Room air temperature difference ( Δ T r o o m ) between the experimental room and reference room was in the range of 0.88 °C–7.04 °C. Effective functions of space heating and heat preservations were achieved; (2) For the cooling season mode, daily E P V and average η e were 0.159 kWh and 6.33 %. Δ T r o o m was in the range of −4.26 °C to −1.26 °C. Effective functions of passive ventilation cooling was realized; (3) The novel window system can provide useful daylight illuminance (UDI) for most time during the working time; (4) Based on the experiment results on transition season, other alternative operating strategies were recommended for specific different ambient condition days. • A novel CdTe based PV ventilated window system integrated with PCM was proposed and constructed. • Several groups of full-day experiments were conducted under different operating modes. • Electrical, thermal and indoor lighting performance were analyzed. • Other alternative operating strategies in transition season were recommended and discussed. [ABSTRACT FROM AUTHOR]

The current research is motivated to arrange an innovative hybrid solar-geothermal system, where the geothermal-driven subsystem is used to give out a sustainable framework for the upstream subsystems. Thus, an integrated geothermal flash cycle combined with organic Rankine cycle 1 (ORC1) is utilized to supply the input electricity of the compressed air energy storage system (CAES) at charging periods. The stored stream is exposed to electricity generation by the use of parabolic trough solar collectors (PTSCs). In addition, ORC2 recovers the waste heat of air turbines. A multi-aspect study is considered from the thermodynamical and economical standpoints. In addition, the sensitivity analysis is carried out to evaluate the effect of different parameters on the performance of the system. Moreover, four optimization scenarios are defined and scrutinized using a multi-objective particle swarm optimization (MOPSO) algorithm. The present study exhibits that the most appropriate optimum solution from the thermodynamic facet is a consequence of a framework in which the energy efficiency of flash-ORC1 and its output electricity is the objective functions. In this situation, the optimum energetic and exergetic efficiencies of the flash-ORC1 unit are equal to 20.43% and 67.63%. Furthermore, the lower optimum payback period equals 3.07 years corresponding to the scenario in which objective functions are the exergy efficiency of flash-ORC1 and the payback period. • Design of a novel hybrid solar-geothermal combined power plant utilizing CAES. • Conduct a coherent parametric study at charging and discharging periods. • Investigation of the proposed system from thermodynamic and economic viewpoints. • Considering four different optimization methods using MOPSO/TOPSIS/LINMAP. • Obtaining The best optimum exergy efficiency and payback period of 67.63% and 3.07 years. [ABSTRACT FROM AUTHOR]

In spite of the fact that the solar power tower system is considered as one of the most valuable power generation facilities, it still faces challenges such as insufficient utilization of the solar salt temperature range and the dependence on high solar radiation intensity. To address this issue, an integrated recompression Brayton cycle and trans -critical regenerative organic Rankine cycle in parallel layout is proposed. The comparison with other literature shows that the specific work of the integrated system (147.8 kW/kg) outperforms the partial cooling Brayton cycle (130.1 kW/kg) under the same solar salt temperature range. In order to forecast future electricity generation and serve as a reference for plant operation, a power prediction strategy using neural networks is developed. Findings indicate that the integrated system can increase power production and maximize solar salt temperature utilization by adjusting the physical constraint strategy based on the changing temperature interval. Its equivalent work and thermal efficiency reach 12.7 MW and 38.36%, respectively, and it can recover the cost in 8 years. These results suggest that the proposed integrated system is a promising solution to enhance the performance of solar power tower systems with significant economic benefits. [Display omitted] • A two-stage power cycle to fully utilize SPT solar salt temperature range is offered. • Proposed system increases power production by adopting physical constraints. • The power cycle adopts low GWP and zero ODP working fluid. • The total specific work of the combined system surpasses the partial cooling cycle. • A BI-LSTM-based power generation prediction strategy of the system is developed. [ABSTRACT FROM AUTHOR]

Abstract In this research paper, a novel solar-based integrated energy system with a thermoelectric generator (TEG) is proposed to provide cooling and hydrogen production. The energy integration is performed by establishing a TEG unit instead of the condenser of the double effect LiBr-H 2 O absorption cooling system. The proposed system is comprehensively investigated and compared with the conventional cogeneration system from energy, exergy, and exergoeconomic point of view. To enhance the understanding of the effect of major design parameters on system exergy efficiency, net output work, total cost rate and hydrogen production, a comprehensive parametric study is carried out. In addition, using a developed MATLAB code, multi-objective optimization method based on genetic algorithm is applied to optimize the proposed model and determine the optimal design parameters. The results of exergy and exergoeconomic analysis show that PVT has the highest exergy destruction rate and the cooling set has the lowest exergoeconomic factor. Results of the parametric study indicate that the proposed system with TEG has higher exergy efficiency, higher hydrogen production rate, lower total cost rate, and lower pay back period. Multi-objective optimization results show that, at the optimum point, exergy efficiency and total cost rate of the proposed system are 12.01% and 0.1762 $/h, respectively. Examining scatter distribution, further shows that the high-pressure generator temperature and PV module area are the most sensitive parameters and should be kept at their lowest value. Higher performance indicators and lower economic indicants reveal that the proposed integration method is more suitable from the exergy/exergoeconomic standpoints. Highlights • Developing a new solar based integrated system with thermoelectric generator. • A newly proposed system to provide electricity, cooling and hydrogen. • Comparing performance of the newly proposed model to the condenser based model. • Applying a Multi-objective optimization to determine the optimal parameters. [ABSTRACT FROM AUTHOR]

Abstract Compared with wind and solar power, biomass power has grown relatively slowly in China. With abundant biomass resources, the development of biomass electric power in China has potential advantages. This paper analyzed the environmental impact of biomass power in the construction and operation stages in comparison with wind and solar power. The results showed that biomass power produced relatively less emissions in the system construction stage at around 1700 ton CO 2 -e/MW. In the operation stage, biomass power projects achieved an average of 131462 ton CO 2 -e per year, which is greater than wind and solar power of equal installed capacity. Biomass power plants could achieve net emission reductions in a shorter time (0.39 year) after operation. The life cycle GHG emissions of biomass power projects are between 42 and 85 g CO 2 -e/kWh. The evidence pointed out that biomass power is worth supporting in China, from the perspective of environmental performance. Local governments should promote the sustainable supply of biomass materials and the development of renewable energy industry should depend on local conditions. Highlights • The unit emissions of biomass power from construction is around 1700 ton CO2-e/MW. • Biomass power projects achieved net emission reductions less than half year. • The life cycle GHG emission of biomass power projects are between 42 and 85 g CO2-e/kWh. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate the effect of simultaneous using of nanofluid and selective absorber on the improvement of work extraction by a solar flat-plate collector (FPC). Applying a precise model for the exergy factor of solar incident, it is found that the maximum power generation is higher and lower than that by the Petela-Landesberg-Press (PLP) and Carnot model, respectively. Results showed that the influence of temperature ratio ( a ) and geometry factor ( f ) on the exergy efficiency is not such significant when a FPC is working on the Earth's surface. It is also revealed that the key role of the ratio of the absorber plate's emittance to its absorptance must be given attention since only the values lower than 0.174 are allowed by the second law requirements. Furthermore, the exergy efficiency and energy efficiency would experience 10.5% and near 8% enhancement for a 7.5% increase in collector's optical efficiency. Boosting the exergy efficiency by almost 4.1% at 4% volume concentration, demonstrated that nanofluid exploitation instead of plain water would be capable of improving the power generation by the collector. [ABSTRACT FROM AUTHOR]

Despite growing concerns over China's Belt & Road Initiative (BRI)'s electricity generation projects, studies analyzing the suitability of such projects to importing countries are rare. Filling this gap, this article assesses the opportunities and challenges of the BRI coal, hydro, wind, and solar power projects. To exploit the full benefits of both qualitative and quantitative approaches, this study uses Analytic Hierarchy Process (AHP), which enables quantitative analysis of the qualitative methods of the interviews and of the Strengths, Weaknesses, Opportunities, and Threats (SWOT) analysis elaborated via consultation of experts. While the BRI power cooperation is a real chance to offer cleaner and more efficient electricity generation especially in developing countries, more emphasis on sustainable development can better guide the BRI power projects. • Despite growing needs, researches concerning the BRI energy cooperation remain rare. • China is leading the global export market of coal, hydro, wind, and solar power. • This article assesses the BRI power projects and offers experts insights. • Large coal and hydro power plants are hampered by socio-environmental concerns. • Challenges can be attenuated via sustainable and competitive wind and solar energies. [ABSTRACT FROM AUTHOR]

Organic Rankine Cycle (ORC) is promising in utilizing low-medium thermal energy, and solar energy is widely considered as the most attractive renewable energy for the future. Consequently, electricity production by coupling ORC and solar energy can reduce the fossil fuel consumption and lower the CO 2 emissions over the world. However, the intensity of solar radiation keeps changing throughout the daytime, so it is important to study the daytime performance of solar-ORC system to guarantee a proper operation. Based on the discretized parameter model built in Dymola, dynamic performances of a small-scale power plant driven by parabolic trough collector (PTC) under clear sky and cloudy sky conditions are analyzed in this paper, respectively. The results show that degree of super heat, evaporation pressure and output power are relevant to direct normal irradiance (DNI) and follow the variation of DNI from morning to afternoon. Particularly, this paper pays attention to analyze the system's responses to the cloud blockage using the dynamic model. It shows that short period (5 min) of cloud blockage of the sun poses no severe influence, while the cloud occurring at morning can cause the system to break down easily. In addition, a conventional PID control strategy is considered for the PTC-ORC system under the weather condition of cloudy sky. The optimized system can generate 105.54 kWh and the system without control can generate 84.95 kWh. The generation can improve 24% compared to the system without control. [ABSTRACT FROM AUTHOR]

Solar-aided coal-fired power generation system (SCPGS) is a promising medium-term solution to reduce CO 2 and PM2.5 emissions from numerous coal-fired power plants in China, yet lacking of unified theoretical guidance. In the present work, firstly, various specific integration schemes are reasonably generalized and unified by theoretical modelling. Secondly, the “superposition effect” has been revealed that the overall coal-savability of SCPGS is determined by not only the direct benefit due to local integration of solar energy but also the global effect of the integration on the system components in a superposition way. Meanwhile, the “promotion effect” has been revealed that the promotability of SCPGS on solar thermal exergy is primarily dependent on the higher-temperature Rankine cycle but sensitive to the energy level coupling between the solar thermal energy and the working fluid. Thirdly, the comprehensive evaluation factor ( f ), which serves as the common evaluation index between different SCPGSs considering both the coal-savability and efficiency-promotability, is proposed. Finally, with the help of the comprehensive evaluation factor, examples of application are given as demonstration for the comprehensive evaluations between 12 individual cases of SCPGS within a common framework. The present work is expected to fundamentally guide the future research and application of SCPGS. [ABSTRACT FROM AUTHOR]

Integrated solar combined cycles (ISCCs) need to be able to handle some of the most dynamic operating conditions of any power generation system in order to provide the flexibility of a natural gas combustion turbine while simultaneously utilizing variable incident solar irradiation. Yet to date, most work on ISCC design has focused on high-level treatments of system viability and potential impact, without thorough consideration of system operations. In this work, a computationally efficient ISCC model is constructed that includes detailed modeling of the heat recovery steam generator that links the natural gas and solar thermal systems. The model is validated against a model in the literature, and then used to perform computational optimization of the facility operations. Critically, a wide variety of practical system constraints are considered at each time step evaluated in order to ensure system feasibility under realistic conditions. It is shown that under different operating modes the ISCC design examined displays similar emission rates, yet significantly different profit ranges. A marked increase in the operating flexibility of the ISCC is observed when the outlet temperature of the solar heat transfer fluid is allowed to vary over the course of the day. [ABSTRACT FROM AUTHOR]

This work proposed and analyzed an integrated solar hybrid system for upgrading and utilization of low-rank coals using coal pre-drying, low-temperature pyrolysis and power generation, efficiently converting the low-rank coal into exportable value-added coal while generating electric power locally. The collected solar energy could be utilized in a cascade way to feed coal pre-drying and low-temperature pyrolysis. The low-energy density raw syngas discharged from the pyrolyzer is efficiently utilized by co-combusting with upgraded coal in the conjunct boiler and a large amount sensible heat of the upgraded coal is effectively recovered through pre-heating the condensate/feed water in the steam turbine unit. A case study for Zhundong lignite upgrading and utilization using the proposed system integrated with a typical 600 MW supercritical power plant was performed. The thermodynamic analysis results showed that, the overall energy and exergy efficiencies could reach 90.0% and 89.8%, respectively, with the product energy distribution ratio at 47.8 MJ/(kW h). The equivalent conversion efficiency of the coal upgrading process soars to 98.8% and the net solar-to-UGC efficiency reaches 49.4%. This proposed concept may provide a science and technology foundation for efficient utilization of the low-rank coal resources and a promising way to advance the solar energy utilization. [ABSTRACT FROM AUTHOR]

A bi-generation system combining direct absorption flat plate solar collector for medium temperatures air-heating applications integrated with a thermoelectric generator was modeled under optically concentrated solar radiation conditions. In order to improve the performance of the bi-generation system, the proposed system was simulated under the effect of evaporative cooling at the cold side of the thermoelectric modules in order to create a cooling effect that decreases the temperature of the cold junction, thus enhancing the electrical conversion efficiency of the thermoelectric modules. Rung-Kutta 4th order method is used to solve the ordinary differential, equation, while Newton-Raphson iterative technique is used to solve the nonlinear algebraic system of the model governing equations. The results have reflected a significant effect for the evaporative cooling on the system performance particularly at high values of optical concentration ratio. Furthermore, an augmentation of 19.13% in the total electrical power output was predicted at a concentration ratio of 20 suns. Simulation results had also shown that more stable electrical performance of the system when adopting evaporative cooling method compared to forced convection. It was found that there was an optimum value of water mass flow rate, at which the maximum power output was generated. Finally, relative humidity was shown to have a less significant impact on the performance at high temperature operation, since the effect of high water vapor partial pressure at the heat sink (cold junction), when the system is operating at elevated temperature, dominated over the effect of ambient relative humidity according to the evaporation rate governing model. [ABSTRACT FROM AUTHOR]

The use of concentrating solar technologies for supplying heat and power in industrial processes is investigated in this paper. The thermal energy produced by a solar field is stored in a TES system and subsequently used in a Heat and Power Generation (HPG) section. In particular, three different HPG configurations are analyzed. The electricity is generated in an Organic Rankine Cycle (ORC) unit while the heat is supplied by a heat generator placed in parallel or downstream of the ORC unit or by recovering the ORC waste heat. An exergy analysis is carried out and the plant exergy efficiency is chosen as marker to evaluate the best configuration. Several power-to-heat ratios and the production of saturated steam or hot water are considered. The results show an optimum utilization field for each configuration. The use of a heat generator operating in parallel with the ORC unit is the only suitable solution for supplying high-pressure steam while its placement downstream of the ORC unit is appropriate for low-pressure steam and high power-to-heat ratios. The use of the ORC waste heat is an interesting option for the hot water production but it requires the full use of available heat to avoid significant exergy degradations. [ABSTRACT FROM AUTHOR]

The purpose of this study is investigating the grid parity (GP) time and the levelized cost of energy (LCOE) of grid-connected photovoltaic (PV) systems installed in densely urbanized contexts. The analysis, which was elaborated for three Italian cities, considered the effects of the promoting policies enacted by the Italian government from June 2010 to May 2016. An appropriate methodology was applied with the aim of realistically defining the energy produced by PV systems installed on buildings with different roof types and number of floors. The calculus of the disbursements considered the operating, maintenance and insurance costs and the wear of PV panels and inverters. The results showed that, depending on the type of the initial investment (with or without a bank loan), the site latitude and the solar shading caused by possible obstacles, the calculated values of LCOE vary from 0.219 €/kWh to 0.485 €/kWh. The time to reach the grid parity resulted shorter than 20 years for the cities in Southern and Central Italy, even considering a reduction of 10% of the solar radiation caused by the surrounding obstacles; less favourable values were obtained in the north of Italy. [ABSTRACT FROM AUTHOR]

Deployment planning of distributed rooftop photovoltaic (PV) systems remains a critical challenge for high-density cities, due to complex shading effects and diversified rooftop availabilities. Furthermore, such planning for large-scale systems could be extremely complex due to high dimensionality caused by the enormous number of buildings. To tackle the challenge, this study proposed an optimal planning strategy for municipal-scale distributed rooftop PV systems in high-density cities. The optimization problem was solved by integer learning programming, based on high-accuracy solar energy potentials characterization. By selecting proper rooftops for PV, the electricity generation was maximized, considering the conflicting budget and peak-export-power constraints. A Hong Kong-based case study (including 582 real building rooftops) was conducted. The effectiveness of the proposed strategy was verified by comparing with 5,000,000 Monte-Carlo-generated alternatives. The strategy more effectively identified the proper rooftops for PV installations, achieving up to 17.7% improvements in performance-cost ratio. Furthermore, the optimal planning strategy was systematically compared with two heuristic planning methods, i.e., total-energy-prioritized and energy-intensity-prioritized methods. The strategy outperformed the heuristic methods by up to 23.3% through well considering trade-off between rooftop total energy and energy intensity. The developed strategy can be used to facilitate rooftop PV deployments, and thus contribute to urban decarbonization. • An optimal planning strategy is proposed for large-scale distributed rooftop PVs. • High-dimensional optimal planning is solved by integer linear programming. • Complex building shading effects and rooftop availabilities are considered. • Improved performance of the planning strategy has been verified. [ABSTRACT FROM AUTHOR]

Compressed air energy storage (CAES) is a method of energy storage which can convert the surplus power to the internal energy of compressed air, and regenerates electricity whenever power is needed. A clean CAES system coupled with wind and solar energy was developed to solve the dependence of traditional CAES system on fossil fuels in China. The operating variables of the hybrid system include heat exchanger effectiveness, ambient temperature, mass flow rate, total pressure ratio and compressor/turbine stages. The effect of these variables on the system performance was evaluated, including output power, overall efficiency, energy ratio ( ER ) and heat ratio ( HR ). The parameters, delineating criteria of the potential development localities for the hybrid CAES system sites, such as solar and wind energy resources, abandoned cavities of mines resources used as compressed air containers and the distribution of cross-transmission lines in China were investigated. By this research, it was found that more than 13 major zones were of the capability to support the hybrid system in China. Finally, the environmental and economic benefits of this CAES system were calculated, comparing to the conventional thermal power plants; restrictions and policy supports of the CAES systems in China were discussed as well. [ABSTRACT FROM AUTHOR]

In the present context, energy access to remote rural households through local energy generating systems has been recognized as a cost effective and extent efficient option. With increased emphasis on eco-friendly technologies and high fuel cost associated with conventional energy generation, the use of renewable energy resources (small hydro, biomass, solar, wind energy etc.) are being explored. The present paper is focused on the optimal sizing of a stand-alone Integrated Renewable Energy System (IRES) which comprises the resources of micro hydro power (MHP), biogas, biomass, solar and wind energy. Initially, a demand response (DR) strategy based on energy consumption scheduling of appliances has been suggested and modelled in the paper. This strategy aims to minimize the peak hourly energy consumption of the study area. Further, different combinations of system components without and with DR strategy were considered and optimized for power reliability criteria of 0% and 5% unmet load. It has been found that significant amount of savings in system sizes and costs are obtained with DR strategy compared to system without DR. [ABSTRACT FROM AUTHOR]

Renewable energy plays significant role in achieving energy savings and emissions reduction. As a sustainable and environmental friendly renewable energy source, concentrated solar power (CSP) is of interest for research and development. This is because CSP plants can be equipped with thermal storage systems, thereby producing electricity when sunlight is not available. The installation of CSP plants also leads to substantial ‘peak shaving effects’. However, the cost of CSP generation is an obstacle hampering the commercialization of this emerging industry. This paper constructs a mathematical model of the levelized cost of energy (LCOE) to calculate the power generation cost of CSP projects on the basis of lifetime cost structure analysis. A sensitivity analysis is conducted to examine the impact of different variables on the LCOE of CSP projects. The variables considered in this study are investment cost over the construction period, annual operation and maintenance cost, annual electricity production and the discount rate. Finally, the influence of incentive policies such as preferential loans, tax support and zero land cost for power stations is analyzed. This research offers a new method for power generation cost calculation of CSP projects and provides support for governments to formulate incentive policies for the industry. [ABSTRACT FROM AUTHOR]

In recent years, solar energy has been considered as one of the principle renewable energy source for electric power generation. In this paper, single diode photovoltaic (PV) system and double/bypass diode based PV system are designed in MATLAB/Simulink environment based on their mathematical modeling and are validated with a commercially available solar panel. The novelty of the paper is to include the effect of climatic conditions i.e. variable irradiation level, wind speed, temperature, humidity level and dust accumulation in the modeling of both the PV systems to represent a realistic PV system. The comprehensive investigations are made on both the modeled PV systems. The obtained results show the satisfactory performance for realistic models of the PV system. Furthermore, an in depth comparative analysis is carried out for both PV systems. [ABSTRACT FROM AUTHOR]

In this study, a thermodynamic analysis is conducted on a multigeneration energy system based on renewable energy sources. The proposed system is developed for residential applications, including individual- and multi-building complexes, utilizing solar energy to produce useful outputs, namely electricity, heat, fresh water and hydrogen. Hydrogen is used for the purpose of storing energy to offset the mismatch between demand and supply when dealt with renewables, such as solar energy. The system is modeled thermodynamically to obtain the optimal energy and exergy efficiencies, heat and work outputs for the overall system. Moreover, greenhouse gas emissions caused by conventional energy systems utilized for the same outputs are calculated and compared with the studied systems. A solar collector area of 24 m 2 is considered for the present system and its analysis. The maximum energy efficiency is 36% and the maximum exergy efficiency is 44%. The total work output for electricity is 116 kW, and hence the CO 2 reduction achieved by this system is 476 tons per year. It can produce 0.04 kg/s desalinated water. The optimum number of suites, as an application for a building complex, which can be sustained with the proposed system is determined as 106 suites. [ABSTRACT FROM AUTHOR]

With an increasing share of wind and solar energy in power generation, properly accounting for their temporal and spatial variability becomes ever more important in power system modeling. To this end, a high temporal resolution is desirable but due to computational restrictions rarely feasible in long-term models that span several decades. Therefore many of these models only include a small number of representative ‘time slices’ that aggregate periods with similar load and renewable electricity generation levels. The deliberate selection of the time slices to consider in a model is vital, as an inadequate choice may significantly distort the model outcome. However, established selection methods are only based on demand variations and are not applicable to input data with a large number of fluctuating time series, which is a drawback for models with high shares of renewable energy. In this paper, we present and validate a novel and computational efficient time slice approach that is readily applicable to input data for all kinds of power system models. We illustratively determine representative days for the long-term model LIMES-EU and show that a small number of model days developed in this way is sufficient to reflect the characteristic fluctuations of the input data. [ABSTRACT FROM AUTHOR]

Although the diffusion of solar electricity has been swift worldwide, there is little certainty regarding the adoption of this technology on rooftops, in locations where there is no specific policy on renewables in place. In such cases, there is much uncertainty regarding the effect of solar penetration on electricity prices to consumers and on the reduction of electricity demand from the grid. The penetration of solar in the residential sector – which in some cases accounts for about 40% of the country's total electricity demand – may have a tremendous impact on incumbent utilities and the industry as a whole. Much research has been devoted to assessing the effect of policy on the diffusion of renewables but not much work about the developing world is known, particularly in those nations where institutional arrangements do not favour these technologies. Using system dynamics, this paper examines these issues, considering the diffusion of rooftop solar both with a battery support system, and also without any type of storage system. An important conclusion is that policy is essential for system sustainability when PV diffusion is taking place. [ABSTRACT FROM AUTHOR]

It is the first time that flat PV (photovoltaic) cells were integrated with SODIS (solar water disinfection) to be an access to the clean drinkable water and the renewable electricity. The disinfection and photovoltaic performance of the system was evaluated by the disinfection of Escherichia coli ( E. coli ) and Salmonella . In order to enhance the SODIS process, a V-trough concentrator and low concentration H 2 O 2 were adopted. The treatment time required for 8 L water that reached completely disinfection was 1.25 h and 2.5 h for the inactivation of E. coli and Salmonella respectively, when using the V-trough concentrator and 5 mg L −1 H 2 O 2 simultaneously. Therefore, E. coli seems not to be a suitable bacteria indicator for SODIS. The temperature of the PV module decreases significantly because of the additional water layer, so that the power generation efficiency is improved. Although the water layer on the PV module can both reflect and absorb light, the output power of the PV module with a V-trough concentrator is about 43 W (the reference is 26.1 W), which is much higher than the whole system power consumption. Therefore, the excess power can be used for other applications. [ABSTRACT FROM AUTHOR]

A combination of PV-TE (photovoltaic and thermoelectric) technologies can effectively broaden the use of solar spectrum as well as increase the total power output. One of the keys is to build a large temperature difference across the thermoelectric module with controlled heat flow. In this paper, a thermal concentrated PV-TE hybrid system is fabricated with optimized thermal management. The heat flow and temperature distribution have been theoretically and numerically calculated, providing guidance for the design of PV-TE hybrid system. The introduction of copper plate serving as thermal concentrator and conductor guarantees a large temperature difference in both sides of TE module. Due to the additional electrical generation attributed to thermoelectric generator, the developed PV-TE hybrid system achieves a high peak efficiency of 23% in the outdoor test which is 25% more than that of PV (photovoltaic) cells. Moreover, the thermoelectric generator contributes extra electrical energy of 648 J even during the absence of sun light. Furthermore, a cost and power lumped model has been developed to estimate the economic feasibility for this hybrid technology. [ABSTRACT FROM AUTHOR]

This study calculates the LCOE (Levelized Cost of Energy) on the PSDA (Atacama Solar Platform) for a solar–solar energy mix with the objective of evaluate new options for continuous energy delivery. LCOE was calculated for three 50 MW (megawatt) power plants: A PV (photovoltaic), a CSP (concentrated solar power) plant with 15 h TES (thermal energy storage) and a hybrid PV-CSP plant constituted with 20 MWp of PV and 30 MW of CSP with 15 h TES. Calculations present two scenario projections (Blue Map and Roadmap) until 2050 for each type of plant. Due to the huge solar resource available in northern Chile, the PV-CSP hybrid plant results to be a feasible option for electricity generation, as well as being effectively able to meet electricity demand profile of the mining industry present in the area. This type of energy could mitigate long-term energy costs for the heavy mining activity, as well as the country CO 2 emissions. Findings point out that PV-CSP plants are a feasible option able to contribute to the continuous delivery of sustainable electricity in northern Chile. Moreover, this option can also contribute towards electricity price stabilization, thus benefiting the mining industry, as well as reducing Chile's carbon footprint. [ABSTRACT FROM AUTHOR]

This study proposes a new renewable energy based multigeneration system, which integrates a solar PV/T system and a geothermal energy system to produce electricity and heat for power, heating, cooling, hot water and drying air, and investigates the design, analysis and assessment of this integrated system. The psychometric processes are utilized for obtaining required dry agent from the ambient air, and an air circulation system is used to benefit from the heat transferred from the PV modules to the air, which ultimately increases the PV/T efficiency and hence the overall efficiency. We also assess the performance of the system, through energy and exergy analysis methods, for a selected common case and obtain overall energy and exergy efficiencies of 11% and 28%, respectively. The selected parametric studies investigate the effects of various environmental and operating conditions on the energy and exergy efficiencies of the overall system and subsystems. [ABSTRACT FROM AUTHOR]

Electricity systems with high penetrations of renewable energy require a mix of resources to balance supply with demand, and to maintain safe levels of system reliability. A load balancing methodology is developed to determine the optimal lowest-cost mix of renewable energy resources, demand response, and energy storage to replace conventional fuels in the Province of Ontario, Canada. Three successive cumulative scenarios are considered: the displacement of fossil fuel generation, the planned retirement of an existing nuclear reactor, and the electrification of the passenger vehicle fleet. The results show that each of these scenarios is achievable with energy generation costs that are not out of line with current and projected electricity generation costs. These transitions, especially that which proposes the electrification of the vehicle fleet, require significant investment in new generation, with installed capacities much higher than that of the current system. Transitions to mainly renewable energy systems require changes in our conceptualization of, and approach to, energy system planning. [ABSTRACT FROM AUTHOR]

SUPP (Solar Updraft Tower power plant) is a technology in the power generation sector. The power productivity and efficiency represent important performance characteristics of SUPP. In the present work a mathematical model was developed to estimate the performance of SUPP based on tracking solar collector consideration in Malaysia. The objective is to verify the suggested model and to optimize the slope angle of tilted tracking solar collector. Basically, the hourly solar data were analysed considering solar azimuth angle for tracking case calculation to determine the solar energy incident on the collector. Then, the useful energy gain was calculated based on heat transfer relations. The model was validated with experimental work and well agreement was achieved. Results revealed that the SUPP of slope collector angle of 10° can produce higher power generation over the whole the year. Also, the tracking solar consideration enhanced the performance characteristics especially the power productivity by around 3.5 kW over that of fixed collector. The maximum collector and SUPP efficiencies of 51% and 0.165% respectively were obtained. [ABSTRACT FROM AUTHOR]

A hybrid system consisting of a CPC (compound parabolic collector) system, a SOE (solid oxide electrolyzer) system and a PEMFC (proton exchange membrane fuel cell) system was proposed to harvest solar energy. And a sensitivity analysis was conducted to evaluate the system performance. The impacts of operating temperatures of the SOE and PEMFC system, and the direct irradiation intensity of the sun on the performance characteristics were systematically analyzed. Results revealed that there exists an optimal SOE operating temperature leading to the maximum power output and maximum electrical efficiency simultaneously. Larger operating temperature of the PEMFC resulted in larger power output and higher efficiency. There also existed optimal direct irradiation intensities leading to the maximum power output and maximum electrical efficiency. Furthermore, the performance of the proposed solar energy harvesting system for practical use in real-life was also simulated. This may serve a clean technology for electricity generation. [ABSTRACT FROM AUTHOR]

Recently, thermoelectric modules have been considered as possible replacement to solar photovoltaic system due to its potential for combined heat and power. In the designs of solar thermoelectric cogeneration systems, a careful compromise has to be made between thermal energy and electrical power. For practical purposes, electrical power is preferred over heat energy. However, due to the current low conversion efficiencies of thermoelectric materials, increasing electrical power generation causes the overall combined efficiency to suffer. This study proposes an exergetic analysis of combined heat and power solar thermoelectric systems to maximize exergetic efficiency. The modeling is based on the previously investigated design of a solar thermoelectric generator for residential combined heat and power generation. The working conditions (cold side reservoir temperature and solar concentration) are varied to maximize exergetic efficiency without sacrificing too much electricity generation. The module geometry for thermal load matching is also suggested. [ABSTRACT FROM AUTHOR]

CSP and PV technologies represent energy sources with large potentials. We present cost-supply curves for both technologies using a consistent methodology for 26 regions, based on geoexplicit information on solar radiation, land cover type and slope, exploring individual potential and interdependencies. For present day, both CSP and PV supply curves start at $0.18/kWh, in North Africa, South America, and Australia. Applying accepted learning rates to official capacity targets, we project prices to drop to $0.11/kWh for both technologies by 2050. In an alternative “fast-learning” scenario, generation costs drop to $0.06–0.07/kWh for CSP, and $0.09/kWh for PV. Competition between them for best areas is explored along with sensitivities of their techno-economic potentials to land use restrictions and land cover type. CSP was found to be more competitive in desert sites with highest direct solar radiation. PV was a clear winner in humid tropical regions, and temperate northern hemisphere. Elsewhere, no clear winner emerged, highlighting the importance of competition in assessments of potentials. Our results show there is ample potential globally for both technologies even accounting for land use restrictions, but stronger support for RD&D and higher investments are needed to make CSP and PV cost-competitive with established power technologies by 2050. [ABSTRACT FROM AUTHOR]

The statistics of low level scattered cloud cover (cumulus or strato-cumulus types), is evolved to formulate analytical expressions for short duration mean output power and its variability , as well as power change distribution, at the output of photovoltaic generating stations. The proposed expressions are used to obtain statistical estimates of the three, which are substantiated by comparison to empirical ensemble estimates reported in available literature. The strength of concepts and formulations presented in the paper is their dependence on a single aggregated meteorological parameter, namely the optical air mass . Their applicability therefore spans over a range of PV generation plants regardless of geographical and weather conditions. [ABSTRACT FROM AUTHOR]

It has been shown that a long term sustainable energy system based on a high penetration of solar photovoltaics requires massive deployment of day charging electric vehicles to make use of the excess solar electricity generation at sun peak hours. In this paper the synergy between these technologies is further explored, determining the minimum penetration levels that allow fulfilling the climate and energy targets. Simulations for a case study of Portugal in 2050 using an electric vehicles smart charging approach show that a 100% renewable energy based electricity supply is possible with certain photovoltaics and electric vehicles combinations and that the environmental targets to reduce carbon dioxide emissions are just reachable with significant electric vehicles market share. The notion that vehicle charging will have to take place during working hours to maximize petroleum displacement is reinforced. [ABSTRACT FROM AUTHOR]

We have recently developed a simple yet powerful method to identify key properties of electricity systems with a high share of renewables. Here, our weather-driven methodology is described and applied to model the Danish power system with combined wind and solar energy gross shares of up to 100% of the total demand. We show that in a wind only scenario, surplus energy grows rapidly beyond gross shares of about 50%, while the potential for arbitrage of surplus renewable energy, i.e. demand-side management or high-efficiency storage, is very limited in this case. A scenario with a wind-solar energy mix of 80/20, on the other hand, both decreases the total amount of surplus and has a significantly higher potential for arbitrage of the remaining surplus. However, beyond gross shares of about 75%, only large-scale seasonal storage of, e.g. hydrogen, enables the use of Danish surplus wind and solar energy to cover the residual Danish electricity demand in both scenarios. [ABSTRACT FROM AUTHOR]

Abstract: The paper investigates the integration of renewable energy sources and water systems, presenting a novel solar system producing simultaneously: electrical energy, thermal energy, cooling energy and domestic water. Such system is designed for small communities in European Mediterranean countries, rich in renewable sources and poor in fossil fuels and water resources. The polygeneration system under analysis includes PVT (photovoltaic/thermal solar collectors), a MED (multi-effect distillation) system for SW (seawater) desalination, a single-stage LiBr–H2O ACH (absorption chiller) and additional components, such as storage tanks, AHs (auxiliary heaters) and BOP (balance of plant) devices. The PVT produces simultaneously electrical energy and thermal energy. The electrical energy is delivered to the grid, whereas the thermal energy may be used for space heating and/or domestic HW (hot water) production. As an alternative, the solar thermal energy can be used to drive an ACH, producing CHW (chilled water) for space cooling. Finally, the solar energy, in combination with the thermal energy produced by an auxiliary biomass-fired heater, may be used by the MED system to convert SW into potable water. The system is dynamically simulated by means of a zero-dimensional transient simulation model. A thermo-economic analysis is also presented, aiming at determining the optimal values of the most important design variables. [Copyright &y& Elsevier]

Abstract: One of the major challenges today is assessing the suitability of PV (photovoltaic) systems' installations on buildings' roofs regarding the received solar irradiance. The availability of aerial laser-scanning, namely LiDAR (Light Detection And Ranging), means that assessment can be performed automatically over large-scale urban areas in high accuracy by considering surfaces' topographies, long-term direct and diffuse irradiance measurements, and influences of shadowing. The solar potential metric was introduced for this purpose, however it fails to provide any insights into the production of electrical energy by a specific PV system. Hence, the PV potential metric can be used that integrates received instantaneous irradiance which is then multiplied by the PV system's efficiency characteristics. Many existing PV potential metrics over LiDAR data consider the PV modules' efficiencies to be constant, when in reality they are nonlinear. This paper presents a novel PV potential estimation over LiDAR data, where the PV modules' and solar inverter's nonlinear efficiency characteristics are approximated by modelled functions. The estimated electrical energy production from buildings' roofs within an urban area was extensively analysed by comparing the constant and nonlinear efficiency characteristics of different PV module types and solar inverters. The obtained results were confirmed through measurements performed on an existing PV system. [Copyright &y& Elsevier]

A combined heat transfer and exergy analysis is developed and used to quantify the performance of a latent heat thermal energy storage system (LHTES) for solar power generation taking into account two practical constraints. First, for long-term operation the thermal energy stored must equal the thermal energy recovered. The second constraint is imposed by the 24 h day. To maximize the second-law performance of a particular latent heat storage system associated with a specific charging temperature, it is shown that a specific phase change temperature must be used in conjunction with a specific heat transfer fluid (HTF) inlet temperature during the discharge process, and a specific charging time. The second-law performance of the storage system can be improved, and potentially impractical operating conditions needed to maximize the second-law performance of the LHTES system can be avoided by modifying the heat transfer design of the energy storage system. Quantitatively, increasing the surface area of the phase change material (PCM) side by a factor of 10 results in a six-fold increase in the exergy extracted from the LHTES system. For a typical salt phase change material, the optimal phase change temperatures corresponding to charging HTF inlet temperatures of 560 °C and 800 °C are 475 °C and 715 °C, respectively. [ABSTRACT FROM AUTHOR]

Abstract: A linear piezoelectric actuator based solar panel cleaning system is proposed in order to make a solar panel operate at the best power generation state while the solar panel is used in dusty environment. A piezoelectric actuator linearly moving on a guide is employed to drive a wiper fixed on the actuator. At a proper pressure force between the wiper and solar panel, the actuator can drive the wiper to effectively wipe a dust layer away from the solar panel's surface. The cleaning system's energy gain, which is defined as the ratio of a solar panel's output electric energy increase caused by cleaning to the energy consumption by the piezoelectric actuator, is much higher than 1. The merits of using the piezoelectric actuator in a solar panel cleaning system is that the cleaning system has light weight and compact structure, which is a common feature of piezoelectric systems. [Copyright &y& Elsevier]

Abstract: Renewable energy generation is expected to continue to increase globally due to renewable energy targets and obligations to reduce greenhouse gas emissions. Some renewable energy sources are variable power sources, for example wind, wave and solar. Energy storage technologies can manage the issues associated with variable renewable generation and align non-dispatchable renewable energy generation with load demands. Energy storage technologies can play different roles in each of the step of the electric power supply chain. Moreover, large scale energy storage systems can act as renewable energy integrators by smoothing the variability. Compressed air energy storage is one such technology. This paper examines the impacts of a compressed air energy storage facility in a pool based wholesale electricity market in a power system with a large renewable energy portfolio. [Copyright &y& Elsevier]

Abstract: South Africa has a highly centralized network, in which almost all electricity is produced in Mpumalanga and transmitted throughout South Africa. In the case of the Western Cape, electricity has to be transmitted over 800–1370 km. This generates losses and entails high transmission costs. Investments in additional production and transmission capacity are needed to cope with the growing demand. Although there is a large potential for solar energy in South Africa, investments are lacking while large investments in new coal-fired power plants are being executed. These coal power plants do not only increase the need for heavier transmission infrastructure, but also have a higher CO2 emission level and a higher pressure on water reserves. This paper performs a more comprehensive cost-analysis between solar energy production and coal production facilities, to make a more elaborate picture of which technologies are more plausible to foresee in the growing demand of electricity. The current centralized electricity infrastructure makes the investment in large production facilities more likely. However, it should be questioned if the investment in large centralized solar parks will be more beneficial than the investments by consumers in smaller solar PV facilities on site. [Copyright &y& Elsevier]

Abstract: Future electricity generation will involve low or moderate temperature technologies. In such a scenario, optimisation of thermodynamic cycles will be a key task. This work presents a systematic analysis to find the operating regime where Brayton cycles reach the highest efficiency, using real substances and given heat source and sink temperatures. Several configurations using fluids close to its critical point at the compressor inlet are considered. Irreversibility sources are carefully analysed, as well as the type of working fluid. The analysis is performed by means of a theoretical approach to obtain some trends, which are afterwards validated with real gases. Results show that the efficiency and the specific work improve if the compressor inlet is close to the critical point. Furthermore, these cycles are less sensitive to pressure drops and politropic efficiencies than those working with ideal gases. The above features are more evident when the ratio of heat source and heat sink temperatures is low. The selection of the gas becomes a fundamental issue in this quest. Critical temperature should be close to ambient temperature, low critical pressure is advisable and the R/c p factor measured at the ideal gas condition should be low to further enhance the efficiency. [Copyright &y& Elsevier]

Abstract: A hybrid power control system is proposed in the paper, consisting of solar power, wind power, and a diesel-engine. To achieve a fast and stable response for the real power control, an intelligent controller was proposed, which consists of the Wilcoxon (radial basis function network) RBFN and the improved (Elman neural network) ENN for (maximum power point tracking) MPPT. The pitch angle control of wind power uses improved ENN controller, and the output is fed to the wind turbine to achieve the MPPT. The solar array is integrated with an RBFN control algorithm to track the maximum power. MATLAB (MATrix LABoratory)/Simulink was used to build the dynamic model and simulate the solar and diesel-wind hybrid power system. [Copyright &y& Elsevier]

Abstract: Offshore applications allow to exploit different renewable energy sources (wave, wind, solar) that are complementary each other, due to their statistical yearly distributions. In this paper, we discuss an offshore platform for energy production from renewable energy sources coupled with three energy storage systems. The proposed offshore platforms uses a Compressed Air Energy Storage (CAES) to timely shift the electricity production from the demand. The performance of the system related to a north Tyrrhenian Sea location was evaluated by a simulation model developed integrating three different software packages (Matlab, EES, TRNSYS). The system was designed to produce 564 kWh on the 2 h a day where peak electricity demand takes place. The results showed that the system is able to produce 177,000 kWh per year. This offshore power plant is conceived for local users (tourist resorts, villages), especially if placed in small or medium islands, wishing to qualify for extensive use of renewable energy. [Copyright &y& Elsevier]

Abstract: The increasing use of fluctuating generation plants like wind turbines and solar power systems, makes new demands on the existing power grid. These are considered to be essential for low-voltage grids. Based on the latest request from the German Federal Government for a progressive improvement of the heat insulation of the residential building stock the impact of a comprehensive passive house standard is analysed. Seeing that, a prediction for the future perspective of natural gas grids and district heating grids throughout Germany in 2050 has been done. Regarding this context the role of decentralised combined heat and power (CHP) as well as heat pumps increases [1]. In connection with enlarged thermal storages, their specific application can add a substantial contribution in combination with an aimed electricity supply of 100% renewable energy. The rational use of these and other supply systems is investigated within a basic virtual power plant model. [Copyright &y& Elsevier]

Abstract: A scalable and modular solar thermal dish-Brayton system is proposed in response to growing demand for renewable energy and distributed power generation. The operating temperature of materials limits the conversion efficiency of existing Concentrated Solar Power (CSP) systems, rendering small-scale systems for residential use too expensive to be marketed. This work proposes a low cost, high efficiency solar receiver as the core of a dish-Brayton CSP system with the capability to achieve much higher operating temperatures than existing receivers. The proposed receiver is fabricated from silicon carbide for its high absorptivity and thermal conductivity. The manufacturing process consists of a simple casting and sintering procedure called co-firing. A heat exchanger is integrated into the walls of the receiver, taking advantage of the high thermal conductivity of silicon carbide. The entire solar energy receiver is designed to heat air up to 1500 K, which is found to be the optimal operating temperature for the proposed output and practical component selection. This operating temperature improves energy conversion efficiency over concentrated solar power generation based on 1270 K by 20%. The optimization of the operating temperature for residential scale, along with experimental test results on a scaled device, is presented. [Copyright &y& Elsevier]

Abstract: A model of correlating atmospheric cross flow and the fluid flow inside a solar updraft tower (SUT) was presented by assuming SUT inflow as a compressible flow. The influence of atmospheric cross flow on SUT inflow was studied using the model. Results showed that atmospheric cross flow had a large influence on SUT inflow, and the SUT inlet air velocity approximately equaled to 26% of cross flow velocity for collector air temperature rise ΔT =0°C. With an increase in atmospheric cross flow velocity, the fluid flow velocity inside SUT was found to increase. The enlargement effect of pressure potential and SUT inlet air velocity induced by atmospheric cross flow increased with higher SUT height, but decreased with higher temperature rise, which is proportional to collector area. The percentage enlargement for cross flow to the pressure potential was between 67% and 102% and that to the SUT inlet air velocity was between 33% and 48%, for H varying from 100m to 3000m and ΔT =20°C. The enlargement drastically decreased for ΔT varying from 0°C to 80°C for H =900m. The work would lay a good foundation for accurate predication of potential power production from SUT power plants by considering the effect of atmospheric cross flow. [Copyright &y& Elsevier]

Abstract: Ammonia is an important input into agriculture and is used widely as base chemical for the chemical industry. It has recently been proposed as a sustainable transportation fuel and convenient one-way hydrogen carrier. Employing typical meteorological data for Palmdale, CA, solar energy is considered here as an inexpensive and renewable energy alternative in the synthesis of NH3 at ambient pressure and without natural gas. Thermodynamic process analysis shows that a molybdenum-based solar thermochemical NH3 production cycle, conducted at or below 1500 K, combined with solar thermochemical H2 production from water may operate at a net-efficiency ranging from 23 to 30% (lower heating value of NH3 relative to the total energy input). Net present value optimization indicates ecologically and economically sustainable NH3 synthesis at above about 160 tons NH3 per day, dependent primarily on heliostat costs (varied between 90 and 164 dollars/m2), NH3 yields (ranging from 13.9 mol% to stoichiometric conversion of fixed and reduced nitrogen to NH3), and the NH3 sales price. Economically feasible production at an optimum plant capacity near 900 tons NH3 per day is shown at relative conservative technical assumptions and at a reasonable NH3 sales price of about 534 ± 28 dollars per ton NH3. [Copyright &y& Elsevier]

Abstract: In this paper, energetic performance comparison of three trigeneration systems is presented. The systems considered are SOFC-trigeneration, biomass-trigeneration, and solar-trigeneration systems. This study compares the performance of the systems considered when there is only electrical power and the efficiency improvement of these systems when there is trigeneration. Different key output parameters are examined: energy efficiency, net electrical power, electrical to heating and cooling ratios, and (GHG) GHG (greenhouse gas) emissions. This study shows that the SOFC-trigeneration system has the highest electrical efficiency among the three systems. Alternatively, when trigeneration is used, the efficiencies of all three systems considered increase considerably. The maximum trigeneration efficiency of the SOFC-trigeneration system is around 76% while it is around 90% for the biomass-trigeneration system. On the other hand, the maximum trigeneration efficiencies of the solar-trigeneration system is around 90% for the solar mode, 45% for storage and storage mode, and 41% for the storage mode. In addition, this study shows that the emissions of CO2 in kg per MWh of electrical power are high for the biomass-trigeneration and SOFC-trigeneration systems. However, by considering the emissions per MWh of trigeneration, their values drop to less than one fourth. [Copyright &y& Elsevier]

Abstract: Knowledge regarding the solar radiation reaching the earth’s surface and its geographical distribution is very important for the use of solar energy as a resource to produce electricity. Therefore, a proper assessment of available solar resource is particularly important to determine the placement and operation of solar thermal power plants. To perform this analysis correctly, it is necessary to determine the main factors influencing the radiation reaching the earth’s surface, such as the earth’s geometry, terrain, and atmospheric attenuation by gases, particles and clouds. Among these factors, it is important to emphasise the role of clouds as the main attenuating factor of radiation. Information about the amount and type of clouds present in the sky is therefore necessary to analyse both their attenuation levels and the prevalence of different sky conditions. Cloud cover is characterised according to attenuation levels, using the beam transmittance (kb , ratio of direct radiation incident on the surface to the extraterrestrial solar radiation) and hemispherical sky images. An analysis of the frequency and duration of each type of cloud cover blocking the sun’s disk is also performed. Results show prevailing sky situations that make the studied area very suitable for the use of solar energy systems. [Copyright &y& Elsevier]

Abstract: Microgrids usually operate in disparate locations and may not be connected to the national grid. The potential sources of electricity in microgrids are wind farms, solar energy, biomass, tidal energy, among others. However, microgrids that are connected to the national grid are gaining importance, because they can supply electricity to the national grid when they have an excess and buy from it when they are in shortage. Such a symbiotic relationship with the national grid helps reduce investment in storage capacity and minimizes other operational costs. In this work, we develop a mathematical model MILP – (mixed integer linear programming) for scheduling operations in microgrids connected to the national grid. We allow several realistic features such as time constraints for the purchase/sale of power from/to the national grid; round trip efficiency of batteries; hydrogen generation, and limits on storage and retrieval rates from batteries/hydrogen tanks/natural gas tanks. Furthermore, to maintain diversity in the generation of electricity from multiple resources, we develop and impose a novel linear diversity constraint on the production schedule without sacrificing the ease of schedule implementation. [Copyright &y& Elsevier]