•A comparative study of various nanofluids was performed under the same conditions.•Photothermal conversion of Au, Cu and carbon black and their hybrids were compared.•Controversially a blend of ...nanofluids cannot enhance the PTE for a given concentration.•Carbon black nanofluid was the favorite considering both efficiency and cost.•A mathematical model based on the Beer’s law was built to predict the PTE.
Direct absorption nanofluid has been introduced as an effective alternative to increase solar thermal conversion efficiency. Hybrid nanofluids were also recently proposed to broaden the absorption spectrum. However, a comparative assessment of the performance of commonly used nanomaterials for solar energy harness is still lacking. In this study, a well-controlled experiment was performed using three different categorised nanofluids, i.e., gold, copper, carbon black nanofluids and their hybrids, to assess their performance in terms of photothermal conversion efficiency (PTE), specific absorption rate (SAR) and materials cost. A mathematical model was built based on the Beer’s law to predict the PTE enhancement. The results revealed, contrary to previously reported, the PTE was not increased by blending different nanofluids with different absorbance peaks, which is mainly due to the dilution of nanoparticles’ concentration. Furthermore, it is found that although gold nanofluids have high SAR, their expensive cost limits their practical use, whereas carbon black nanofluids are more feasible. In addition it was found that the theoretical PTE can be well predicted mathematically based on the optical properties of the used nanofluids.
•Two loop thermosyphon associated in series and parallel configurations are studied.•In series association, the thermosyphon condenser is coupled to the evaporator of the other.•In parallel ...association, two independent evaporators are connected to a common condenser.•Solar intermittency for hybrid systems operating in a typical day was studied.
The use of thermosyphon technology to improve the efficiency of solar collectors, in thermal energy applications, has received literature increasing attention. The absence or decrease of solar radiation during nights or cloudy days can be compensated by another energy source, in the so-called hybrid solar systems. In the present paper, these systems, composed by two loop two-phase thermosyphons with independent evaporators, arranged in series and in parallel, are studied and compared between themselves for the first time in the literature. In the series configuration, the backup energy source feeds the evaporator of the auxiliary loop, which condenser is thermally connect to the evaporator of the main loop, also fed by the solar energy. In the parallel arrangement, both loops deliver the heat to a common condenser. These systems are tested under steady state conditions, keeping one or both evaporators active, representing the single (solar) or hybrid operation. The thermal resistance for both configurations are compared. Results of experiments simulating the operation throughout a typical day, including solar intermittency, are shown. In the solar intermittence tests, the backup evaporator, in the parallel arrangement, is able to compensate for solar absence 47% quicker, on average, when compared to the serial configuration. For the daily operation tests, the serial configuration is able to maintain the vapor temperature levels stable, when operating under different heat input rates between evaporators, while, in the parallel arrangement, vapor temperatures and thermal resistances varied significantly along the test.
•Pilot study of photothermal conversion of Ag nanoparticle under realistic conditions.•Tests were performed under direct sunlight continuously for ∼10h.•Silver nanoparticle improves remarkably the ...photothermal conversion efficiency.•Bulk temperature rise of Ag nanofluids can be 10 times higher than the base fluid.•The specific absorption rate of silver reaches ∼0.6kW/g initially.
A nanoparticle-based direct absorption system provides a promising alternative to conventional solar collectors. This work investigates experimentally the photothermal conversion characteristics of one of the plasmonic nanoparticles, i.e., silver, under realistic conditions. Stable silver nanofluids are formulated through a high-pressure homogenizer and the experiments are conducted under sunlight on a rooftop with tests running continuously for ∼10h. The results show that silver particles have excellent photothermal conversion capability even under very low concentrations. Up to 144% enhancement in the stored thermal energy can be obtained at the peak temperature for a particle concentration of 6.5ppm. The photothermal conversion performance shows a transient behavior and is best achieved at the initial radiation period due to the low heat loss and strong surface plasmon resonance effect of silver nanofluids. Nearly constant initial specific absorption rate (SAR), ∼0.6kW/g, is obtained for nanoparticle concentrations up to 6.5ppm, but it decreases significantly at higher concentrations, which is associated with increased particle–particle interactions.
The efficiency of municipal solid waste to energy incineration plant is limited due to the higher amount of moisture content in the feedstock and huge heat loss. An innovative configuration is ...proposed in the present study to increase the performance of incineration plant. The new design consists of the integration of a solar thermal system with the incineration plant, so that the steam exiting the superheater of the municipal solid waste (MSW)incineration boiler is further heated by solar thermal system to increase its temperature and quality before entering the steam turbine. In addition, the flue gas is used to drive an iso-butane organic Rankine cycle to produce power that is utilized for hydrogen and freshwater production with the help of a proton exchange membrane electrolyzer and reverse osmosis system, respectively. Through a parametric analysis, the effect of major parameters on the performance of the proposed system is studied. The energy, exergy, and exergo-economic investigations are performed to access the system efficiencies, exergetic cost rates, sustainability index and total exergy destruction rate. The results show that the energy and exergy efficiencies of the integrated system are almost 21.34% and 16.64%, respectively, while thermal and exergy efficiencies of the MSW incineration plat are 37.35% and 35.22%, accordingly. The exergo-economic evaluation concludes that the exergy destruction rate of the system is 42965 kW with the rate of exergetic cost and total cost rate of 542 $/hr and 665 $/hr respectively. The sustainability index of the proposed system is calculated to be nearly 1.64, while fresh water and hydrogen production rates are 26.96 kg/s and 2.87 g/s, accordingly. In the end, the solar integrated waste-to-energy plant can provide multiple outputs simultaneously after adding the waste heat recovery system and the proposed system is theoretically feasible from the results of thermodynamic, economic, and environmental analysis.
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•Innovative solar integrated WtE incineration plant with heat recovery system.•Exhaust flue gasses utilized for hydrogen and freshwater production via ORC.•System was evaluated by exergoeconomic analysis for detailed investigation.•Sustainability index used for evaluating environmental performance.•Single flow chart of exergy destruction rate, exergy cost and total cost rate.
In Europe, about a third of the total final energy demand of the industrial sector is used for the generation of low temperature heat below 100 °C which could be satisfied by commercially available ...solar thermal applications. Although the technological readiness level of solar thermal technologies is currently in high levels, the recent energy mix data of industrial countries with high solar irradiation levels reveal that this potential still remains untapped. The key objective of this work is to quantify this unexploited potential and assess the environmental impact of industrial solar thermal systems (ISTS). Under this context, cradle-to-use Life Cycle Assessment (LCA) was conducted for the definition of the environmental performance of ISTS. A parametric analysis for the application of ISTS at selected European sites with diverse solar potential was also implemented to investigate the impact of solar potential on the life cycle performance of the systems. Taking into consideration the findings on the potential of carbon savings from the application of ISTS and in relevance to the European Union Emissions Trading System (EU ETS), scenarios of ISTS penetration and monetization into the industrial sector have also been developed. The findings of this work can be used by policy-makers as guidelines for the development of national strategic plans and financial incentives for the promotion of large-scale industrial solar thermal applications. The implementation of a parametric assessment on the environmental performance of ISTS for specific European geographical locations of diverse solar potential enabled the development of a ‘Life Cycle Produced to Consumed Energy’ Ratio, which indicated that applications located at lower latitudes (in the northern hemisphere) can achieve greater life cycle energy and carbon savings than ISTS applications found higher in latitude. In particular, large-scale ISTS applications were found to achieve energy and carbon savings ranging from 35 to 75 GJ and 2–5 tonnes of CO2 per kWth, depending on the geographical location.
•Environmental impact assessment of industrial solar thermal systems (ISTS).•LCIA results relate linearly to the nominal thermal power of the ISTSs.•Carbon savings range from 35 to 75 GJ and 2–5 tonnes of CO2 per kWth of ISTS.•Life Cycle Produced to Consumed Energy Ratio: 0.015 (37° lat.) ― 0.006 (60° lat.).•Transportation environmental impact of ISTS within Europe is negligible.
•A modified version of the Deep Operator Network was proposed.•Deep Operator Network accurately predicts state-of-charge and efficiency of the system.•Prediction deviations are below 6.8% for the ...state-of-charge and 2.5% for efficiency.•The forecast accuracy of Deep Operator Network and Long Short Term Memory was compared.
Modeling and prediction of the dynamic behavior of thermal systems operating under intermittent energy input and variable load requirements represent one of the greatest challenges in the development of efficient and reliable renewable-based power generation technologies. In this work, a data-driven machine learning modeling framework was developed based on a modified version of the Deep Operator Network architecture where the time coordinate in the trunk net is replaced with historical data of the predicting quantity. The modeling framework can be used to accurately predict the performance of renewable-based energy conversion technologies including wind- and solar-based power plants. This novel framework was applied on a solar-thermal system that consists of a solar collection loop using a flat plate collector, a power generation loop comprising an Organic Rankine Cycle, and a thermal energy storage tank connecting both loops. Variable solar irradiance, air temperature, and power load profiles were used by the Deep Operator Network to predict the State-of-Charge and the efficiency of the thermal system for several days. The results were compared with the State-of-Charge and efficiency functions calculated using a physics-based model. For a simple operation scenario, characterized by a clear sky solar irradiance profile and constant load, the standard deviation in the State-of-Charge prediction by Deep Operator Network is below 0.9% during a seven-day prediction time horizon. For the most realistic operation scenario that considers real solar irradiance and a rough load profile, the maximum standard deviation in the predictions for the State-of-Charge and efficiency are below 6.8% and 2.5%, respectively. A comparison between Deep Operator Network and Long Short Term Memory network was also performed. In general, both networks predict very well the State-of-Charge for different data density conditions; however, a higher accuracy, with a standard deviation below 2.0%, is obtained by the Deep Operator Network during three and half days using sparser training data of 20-minute points. The same accuracy for the State-of-Charge prediction with the Long Short Term Memory network is achieved only for 14 h. Average standard deviations for the State-of-Charge prediction of 1.1% with the Deep Operator Network and 1.5% with the Long Short Term Memory network are obtained for a four-day prediction time using a denser training data of 5-minute points.
The objective of this study is to optimize a solar driven trigeneration system under various optimization criteria. More specifically, parabolic trough collectors are selected to feed with heat the ...generator of a trigeneration system. The produced vapor is expanded in a turbine where electricity is produced. The system also includes an ejector device, a condenser where the heating is produced and an evaporator where the cooling is produced. The cooling load is produced at 10 °C and the heating load at 50 °C, typical temperature levels for building applications, as hotels. This system is optimized under steady-state conditions with different criteria which are based on the exergetic, energetic and economic performance. The optimization is performed separately with every criterion, as well as with combined goals performing multi-objective optimization procedures. Different criteria lead to different optimum system designs. According to the final results, using all the examined criteria together, the optimum system presents 11.26% exergy efficiency, 87.39% energy efficiency and 7.694 €/h energy savings cash flow. The electricity, cooling and heating productions are 4.6 kW, 7.1 kW and 59.4 kW respectively. These results are obtained for turbine pressure ratio 3.6, turbine inlet temperature 195.5 °C and R141b as working fluid.
•A trigeneration system driven by parabolic trough solar collectors is examined.•The system is optimized under various exergy, energy and financial criteria.•Various single and multi-objective optimizations are conducted.•The optimum system produces 4.6 kWel electricity, 7.1 kW cooling and 59.4 kW heating.•The optimum system has 11.26% exergy efficiency and 87.39% energy efficiency.
•Designed a novel Modified CPC (MCPC), Prototype built and tested in on-field conditions and costed on actuals.•Cost effective (Less than $60/m2 aperture)•Modular Design that can be shipped ...disassembled and assembled on site without heavy equipment.•It provides the significant opportunity to use SIPH (Solar for Industrial Process Heat) systems to address the need for industrial process heating.•Design can seriously address UN SDG-7, SDG-8 and SDG-13.
In the context of achieving Net Zero targets, the adoption of compound parabolic concentrator (CPC) technology can play a vital role. The purpose of this work is to modify the design of a conventional CPC in such a way that for the same concentration ratio, and for same aperture area, the modified CPC (MCPC) will require significantly less material for its support structure, receiver and reflector: and hence will have reduced cost. The MCPC, we designed, has a concentration ratio of 4 and an acceptance angle 10° and requires position modification only once a month when oriented with its long axis along the East-West direction. We report experiments on an experimental prototype: the solar-to-thermal efficiency of which was 35.7% and cost of which was below $60/m2. This MCPC enables inexpensive and convenient generation of heat applications including driving low temperature industrial process heating, generation of hot water, hot air for drying, space-heating and even cooking. This can directly contribute to meeting Net Zero goals and furthermore address the problem of deforestation due to use of wood for domestic cooking. Also, since the MCPC can be manufactured using technologies available even in semi-urban regions of the Sun-belt, use of the MCPC can also boost local manufacturing economies providing dignified employment opportunities in currently underserved parts of the world.
Solar energy is the powerhouse where all potential and classified renewable energies lug their sources. The energy transformation from the Sun to electricity requires an adequate control scheme to ...maximise the generated power and enhance the system efficiency. Besides, more than half of solar irradiation on conventional Photovoltaic (PV) panels is lost. The PV thermal (PV/T) modules have been introduced to convert the lost irradiation to heat. Thus, a systematic review of system components, development, and strategies for grid-connected solar PVs plants is presented. Two solar PVs, traditional PV and PV/T, are evaluated. Each grid-tied PV component is considered a subsystem to analyse the potential improvement of grid-connected PVs. This is from solar resources to grid-tied PV inverter techniques. An intensive assessment of the system improvements is presented to evaluate PV plants’ benefits, challenges, and potential solutions. The improvement trends for the novel generation of grid-connected PV systems consist of applying innovative approaches. It is also found that intelligent strategies optimally ensure the overall efficiency of grid-tied PVs using real-time control and measurement under innovative applications and technologies. These methods effectively assist in enhancing grid-tied diverse solar power approaches. Therefore, this paper would offer a significant foundation for advanced research into the subject of grid-tied PV and PV/T and their innovation and/or technology development.
Solar assisted absorption chiller is one of efficient cooling production systems for large cooling capacities. The main drawback of this system is that in addition to the electricity consumption, it ...demands for a lot of heat in relatively high temperature range of 90–120 °C, though the solar system may provide a significant portion of this heating demand. On the other hand, in gas transmission systems, there are some expansion stations in which gas pressure is reduced considerably and this pressure drop causes temperature collapse in gas stream. Power productive gas expansion station (PPGES) is the most recent design proponed for these stations in which the unit is equipped with power generation systems. In this work, taking advantage of this temperature fall for cooling production is proposed by coupling the station with an absorption chiller. In this case, the chiller could also provide the heating demand of the expansion station. In order to evaluate the effectiveness of the proposed configuration, it is simulated for a case study in Denmark, i.e. Aarhus University (AU) hospital absorption chiller and Viborg gas station. The results show that the expansion station could provide an annual cooling production contribution of 27%. In addition, the paper presents an extensive economic assessment to prove the impact of the proposed system economically. The results show a great enhancement in the levelized cost of energy (LCOE) of the case study in case of employing the hybrid system instead of the conventional chiller.
•A hybrid free cooling-power production system is designed.•The system is a combination of solar assisted chiller and gas expansion system.•The technical problem of the cooling production process of a hospital case study is solved by this system.•The gas expansion can provide 27% of the cooling capacity of the case study.•The annual average rate of power production is well above 470 kW.
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