Search

Copyright of Acta Agriculturae Zhejiangensis is the property of Acta Agriculturae Zhejiangensis Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Thermal performance modeling and performance prediction of a solar still which is single basin single slope (SBSS) for the typical climatic condition of India at Jalandhar (31.3260° N, 75.5762° E) is analyzed in the present work. A numerical investigation of an SBSS solar still is conducted during the month of June 2022 using the ANSYS Fluent 2021 computational fluid dynamics (CFD) package and artificial neural network (ANN) prediction model. A user define function is written and used in fluent to formulate the problem with 9‐h solar radiation flux, on solar still glass surface. The simulation outcomes for surface temperature at three different water depths were compared with the existing experimental study. Water temperature and productivity of freshwater were well aligned with experimental results. Three‐dimensional domain is used with a two‐phase volume of fluid model for the condensation and evaporation processes in a solar still. The performance evaluation parameters, that is, coefficients of convective, evaporative, and radiative heat transfer, different temperature values, distillation output, and system efficiency were calculated numerically. The parametric analysis is expanded, and an ANN model in MATLAB R2020a is utilized to estimate yearly performance and reduce the high computational cost of numerical analysis. The data for solar radiation, design, and operational parameters are fed into the ANN model, and as a result, the water temperature at various depths is computed. The ANN model was trained using numerical results computed for the month of June and tested, showing 99.7% accuracy with CFD results. The annual performance of the solar still was evaluated using ANN models for 9 h of the day and with different boundary conditions. To decrease computational and experimental costs, the recommended technique of combined CFD and ANN models for computing the annual performance of (SBSS) solar still is the most effective option. [ABSTRACT FROM AUTHOR]

Reserve sites for coastal nuclear power plants are gradually being depleted, prompting a shift towards the development of inland nuclear power stations. A new cooling system based on the integration of multiple cooling sources using a hybrid dry–wet cycle is proposed to achieve a balance between energy and water consumption for inland nuclear power stations. Comparative studies among all the available cooling systems were further conducted to analyze the cooling performance and economic viability. The case study results indicate that, in comparison to relative humidity, the cooling performance and circulating water consumption of cooling systems are more susceptible to changes in dry-bulb temperature. In arid and water-scarce regions, a Combined Natural Draft Hybrid Cooling System generally exhibits a monthly average circulating water consumption rate that is more than 270 kg/s lower than that of the natural draft wet cooling system, with an average monthly back pressure reduction of 0.11 kPa. When the dry-bulb temperature exceeds 13 °C, the net profit of wet cooling surpasses that of hybrid cooling. However, this scenario undergoes a reversal as the dry-bulb temperature decreases and local water prices rise. It is emphasized that hybrid cooling demonstrates minimal impact when subjected to changes in environmental conditions, offering extensive regional applicability. [ABSTRACT FROM AUTHOR]

Solar stills provide better and economical options for getting clean water, especially in remote locations. In present work authors proposed an active solar still coupled to an integrated collection/ storage type of solar water heater. Mathematical model of the proposed system has been developed to evaluate the thermal performance of the proposed system. Numerical computations have been performed considering the climate of Raipur, Chhattisgarh, India (21.2514°N, 81.6296°E). The effect of depth of water in solar still and the mass flow rate (MFR) of water flowing from heater into the solar still has been investigated. It is seen that the lower depth of water in basin gives more output in comparison to higher depth. At higher mass flow rate of water from solar water heater into the still, the output produced is more in comparison to low MFR. When the mass flow rate of water increased from 0.0020 to 0.012 kg/s the increased in the hourly output of still is about 51.4%. However, at higher MFR the pumping power required will be more. At 0.03 m water depth in basin the annual distillate output produced for Raipur is 2,288 kg/m2 and when the depth of water is increased to 0.12 m the annual output produced is 705 kg/m2 (MFR of water from pond is considered as 0.011 kg/s). when the depth of water is increased from 0.3 to 0.12 m the decrease in annual output is about 69.2%. The cost/liter of water produced from the proposed design is Rs. 1.08/L (US$ 0.013/L) for Raipur, Chhattisgarh, India (at 0.03 m water depth). [ABSTRACT FROM AUTHOR]

Reserve sites for coastal nuclear power plants are gradually being depleted, prompting a shift towards the development of inland nuclear power stations. A new cooling system based on the integration of multiple cooling sources using a hybrid dry–wet cycle is proposed to achieve a balance between energy and water consumption for inland nuclear power stations. Comparative studies among all the available cooling systems were further conducted to analyze the cooling performance and economic viability. The case study results indicate that, in comparison to relative humidity, the cooling performance and circulating water consumption of cooling systems are more susceptible to changes in dry-bulb temperature. In arid and water-scarce regions, a Combined Natural Draft Hybrid Cooling System generally exhibits a monthly average circulating water consumption rate that is more than 270 kg/s lower than that of the natural draft wet cooling system, with an average monthly back pressure reduction of 0.11 kPa. When the dry-bulb temperature exceeds 13 °C, the net profit of wet cooling surpasses that of hybrid cooling. However, this scenario undergoes a reversal as the dry-bulb temperature decreases and local water prices rise. It is emphasized that hybrid cooling demonstrates minimal impact when subjected to changes in environmental conditions, offering extensive regional applicability.

Daylighting has a great impact on student's health, learning performance, and productivity. The goal of this paper is to enhance daylighting performance by examining the year-round daylighting performance of Southern facades in the case of one central window in a classroom located in Cairo, Egypt by using static external horizontal shading devices during the Fall, Spring, and Summer semesters The scope of the study is to evaluate and assess the effect of the window-to-wall ratio (WWR) in addition to the louvers' configurations of depth and count parameters of the classroom on annual daylighting performance metrics for classrooms' southern facades by using Rhinoceros, Grasshopper interface and Honeybee Plus plugin which uses the Radiance engine for annual daylighting Simulations. Annual Sunlight Exposure, Spatial Daylight Autonomy, and upper and lower limits of useful daylight illuminance are incorporated for an efficient annual daylighting performance. Based on geographical location and sun altitude angles that are gathered from ladybug tools, three alternative configurations of fixed horizontal louvers were investigated to evaluate the difference between them. Results show a low difference with the proposed louver configurations cases and a high reduction in annual sunlight exposure by 78% which complies with LEED v4 and IES-LM-83-12 criteria. [ABSTRACT FROM AUTHOR]

Performance evaluation of the solar collector is paramount for the design and optimization of the concentrating solar power system. To evaluate the real-time and annual performance of an ultra-high-temperature collector, a comprehensive model combining an optical-thermal model and an artificial neural network was developed. Initially, the optical performance of the collector was derived by an optical model developed by Monte Carlo ray tracing. Subsequently, by integrating the optical model with a computational fluid dynamics model, the optical-thermal performance of the collector was obtained under various operational conditions. Next, a high-precision artificial neural network model was developed using the data obtained from the optical-thermal model, with a predictive accuracy exceeding an R 2 value of 0.9999. Finally, the comprehensive model was employed to analyze the real-time and annual collector performance. The results reveal significant fluctuations in the real-time optical-thermal performance throughout the year, while the monthly field efficiency, receiver efficiency, and collector efficiency demonstrate relatively moderate variations throughout the year, remaining within the ranges of 64.3%–74.9%, 76.4%–82.8%, and 52.8%–61.5%, respectively. Furthermore, the annual field efficiency, receiver efficiency, and collector efficiency can reach 69.7%, 81.6%, and 56.8%, respectively. This study offers reliable models and meaningful insights for the performance predictions and improvements of solar collectors. •An artificial neural network based model is developed for solar tower collector. •Real-time and annual optical-thermal performance of the collector is revealed. •Peak real-time collector efficiency can reach 69.0 % during a typical year. •Monthly collector efficiency ranges from 52.8 % to 61.5 % throughout the year. •Annual collector efficiency can reach 56.8 % at the outlet temperature of 1623 K. [ABSTRACT FROM AUTHOR]

Natural draft hybrid cooling (NDHC) for thermal power generating units is proposed to achieve a balance of energy and water consumption for arid areas. This study examines the two main design forms of hybrid cooling with airside in serial and parallel heat exchange based on the same tower shell and heat transfer areas. Taking full consideration of the thermal cycle of the power generating unit, simplified simulation models for different cooling systems are established to show the influences of ambient conditions and marketing factors. Results show that both the hybrid cooling designs have a better cooling efficiency than either dry cooling or wet cooling. Expanded inlet areas of hybrid cooling in the parallel heat exchange design bring high heat transfer performance. As for the serial design, the higher temperature of the air at the outlet of the dry section maintains a larger airside mass flow rate, obtaining a high-efficient cooling system. The hybrid cooling in the serial design type relies more on the heat transfer performance of the wet section and is more sensible to ambient humidity, while the performance of hybrid cooling in the parallel design mainly depends on the dry section and is more easily affected by ambient temperature. Considering the unit cost variations of coal and water treatment, hybrid cooling in the parallel design has a wider range of applications compared with the serial design. With the growth in coal cost, there exist more benefits with the serial design. [ABSTRACT FROM AUTHOR]

Summary: This article studies a new architecture of a thermosyphon loop and its capacity to cool data center considering the climate of several cities in France. A parametric experimental study is carried out to show the effect of the refrigerant fill ratio, the input heat load, and the outside temperature. The optimal fill ratio is 16% and the maximum cooling capacity is 1900 W when the data center outside temperature is 20°C. A hydraulic and thermal analytical model is developed to simulate the thermosyphon loop, and it is validated with the experimental results. The cooling load of a typical data center with ten racks, each one dissipates 4.5 kW, is simulated by TRNSYS software for the eight chosen cities in France. The annual performance shows that the percentage of undissipated heat is 13.4% in Marseille that has the highest annual average outside temperature and 2.7% in Caen that has the lowest summer average outside temperature of the data center. The particularity of this work is that it gives the annual performance of a new architecture of a thermosyphon loop in several cities of France with different climates and without electricity consumption. [ABSTRACT FROM AUTHOR]

• Experimental performance of 45 m2 non-tracking solar thermal array described. • Performance evaluated at 80 °C, 135 °C, and 170 °C in dirty and clean conditions. • Annual thermal generation estimated 1000 kWh/m2 at 100 °C and 700 kWh/m2 at 160 °C. • $300/m2 installed, $6.5/m2 annual O&M, levelized cost of heat 2–4 cents per kWh. • Applications in desalination, evaporation, steam generation, process heating. In this paper, the experimental performance of a 45 m2 solar field of non-tracking external compound parabolic (XCPC) collectors installed at the University of California, Merced is described. The solar field was operated during July-August 2020 in both clean and dirty conditions and at varying operating temperatures (70, 135, 170 °C) while operating an air heater, thermal evaporator, and double effect absorption chiller. Performance data was used to develop an instantaneous solar field performance model which was then incorporated into an annual performance model using TMY3 data to estimate yearly production from the solar field. The model predicts an annual generation of ∼1100 kWh/m2-year at 80 °C, ∼1000 kWh/m2-year at 100 °C, ∼900 kWh/m2-year at 120 °C, ∼800 kWh/m2-year at 140 °C, and ∼700 kWh/m2-year at 160 °C in California. The XCPC technology is currently expected to have an installed cost of $300/m2 and an annual operations and maintenance cost of $6.5/m2-year. Over a 25 year lifetime it provides a levelized cost of heat at 2–4 cents per kWh th delivered. This is below the cost of commercial natural gas in California and at temperatures ≤ 120 °C below the cost of industrial natural gas, which highlights the potential of the XCPC technology for decarbonizing thermal applications such as water and space heating, drying, sterilization, desalination, evaporation, low pressure steam, double effect absorption chilling, process heating, and more. The lifetime cost of emissions reductions is ∼$169 per metric ton of avoided CO 2 when replacing natural gas, ∼$137/MT CO 2 when replacing propane, and ∼$83/MT CO 2 when replacing electric heating. [ABSTRACT FROM AUTHOR]

A case study of designing of a reverse osmosis (RO) desalination plant using a Solar Photovoltaic (PV) system is investigated in this work. The RO system is a desalination plant providing pure water to the Shoiaba power generation plant. The system consists of a PV array connected to an inverter for day time or batteries for night time. The PV is designed to meet the high-pressure pumps' load that is about 13649 kWh a day. Because the plant is operated 24 hours a day the PV panels are divided into two parts, one to cover the day time load and the second to cover night load that is stored in batteries. Based on weather conditions of solar radiation of the shortest day and maximum ambient temperature the PV is sizing and a storage system is determined. The system is modeled by the TNSYS software to simulate the performance of the system during the year. The annual performance of system proves that the system is able to meet the required load during the year. It can be concluded that it is a great opportunity to install photovoltaic panels and increase the efficiency of Reverse Osmosis Desalination Plant. [ABSTRACT FROM AUTHOR]

As cooling of Photovoltaic panel by water improves the electrical conversion efficiency and produces warm water as a by-product, photovoltaic thermal system is being used for cogeneration of electrical energy and hot water. In this study, the annual performance of a glazed photovoltaic thermal system (combination of PV module and solar flat plate collector) with storage tank was investigated by the dynamic computational model. The model was developed using MATLAB under actual hot water demand condition for co-generation electrical energy at Dire Dawa in Ethiopia. The computational model determines the electrical energy production and temperature of water at different points and other components of the PV-T system within a given time interval. In addition summaries of monthly and annual incident solar irradiance, electrical energy generation, thermal energy transported to storage and thermal energy supplied as hot water to end users are computed, considering the hourly hot water consumption pattern and storage size effect. The simulation, which is conducted for 20 m2 PV-T system, consists of 12 panels with each 1.64 m2 module areas resulted in generation 803 kWh/year thermal energy and 310 kWh/year electrical energy. The annual average electrical efficiency, thermal efficiency, hot water end use overall efficiency and co-generation (PV-T) efficiency of the system were 15.4%, 50.4%, 38%, and 65.8% respectively. The fraction of solar energy in meeting the heating load for hot water generation was 44.5% for 60℃ hot water supply temperature. Hence, that PV-T system can only be used for water preheating meeting at maximum half of the heating load in tropical area.

Abstract This paper presents an annual performance evaluation of three maximum power point tracking (MPPT) methods. The used MPPT techniques (Perturb and Observe, Incremental Inductance and Sliding mode) are evaluated under an annual data of atmospheric conditions of the target site. The main contribution of this work is to consider real fluctuation conditions of solar irradiations, ambient temperatures and wind velocities. It was found that the Sliding mode provides higher energy yields independently of the period. Compared to the basic P&O and the IC techniques, sliding mode has the potential of generating up to 8.18% more electrical energy than other techniques.

Natural draft hybrid cooling (NDHC) for thermal power generating units is proposed to achieve a balance of energy and water consumption for arid areas. This study examines the two main design forms of hybrid cooling with airside in serial and parallel heat exchange based on the same tower shell and heat transfer areas. Taking full consideration of the thermal cycle of the power generating unit, simplified simulation models for different cooling systems are established to show the influences of ambient conditions and marketing factors. Results show that both the hybrid cooling designs have a better cooling efficiency than either dry cooling or wet cooling. Expanded inlet areas of hybrid cooling in the parallel heat exchange design bring high heat transfer performance. As for the serial design, the higher temperature of the air at the outlet of the dry section maintains a larger airside mass flow rate, obtaining a high-efficient cooling system. The hybrid cooling in the serial design type relies more on the heat transfer performance of the wet section and is more sensible to ambient humidity, while the performance of hybrid cooling in the parallel design mainly depends on the dry section and is more easily affected by ambient temperature. Considering the unit cost variations of coal and water treatment, hybrid cooling in the parallel design has a wider range of applications compared with the serial design. With the growth in coal cost, there exist more benefits with the serial design.

This paper proposes a combination of a nuclear and a concentrated solar power (CSP) plant. Most of today’s operating nuclear reactor systems are producing saturated steam at relatively low pressure. This, in turn, limits their thermodynamic efficiency. Superheating of nuclear steam with solar thermal energy has the potential to overcome this drawback. An innovative configuration of a hybrid nuclear-CSP plant is assembled and simulated. It brings together a small pressurised water reactor and a parabolic trough solar field. The solar heat is transferred to nuclear steam to raise its temperature. Continuous superheating is provided through molten salts-based thermal energy storage (TES). The results from design point calculations show that solar superheating has the potential to increase nuclear plant electric efficiency significantly. Solar heat to electricity conversion efficiency defined as the ratio of extra generated power to collected solar energy reaches unprecedented rates of 52%. An off-design model was used to simulate 24-h operation for one year by simulating 8760 cases. Due to TES non-stop operation is manageable.

This paper proposes a comprehensive thermodynamic and economic model to predict and compare the performance of concentrated solar power plants with traditional and novel receivers with different configurations involving operating temperatures and locations. The simulation results reveal that power plants with novel receivers exhibit a superior thermodynamic and economic performance compared with traditional receivers. The annual electricity productions of power plants with novel receivers in Phoenix, Sevilla, and Tuotuohe are 8.5%, 10.5%, and 14.4% higher than those with traditional receivers at the outlet temperature of 550°C. The levelized cost of electricity of power plants with double-selective-coated receivers can be decreased by 6.9%, 8.5%, and 11.6%. In Phoenix, the optimal operating temperature of the power plants is improved from 500°C to 560°C by employing a novel receiver. Furthermore, the sensitivity analysis of the receiver heat loss, solar absorption, and freeze protection temperature is also conducted to analyze the general rule of influence of the receiver performance on power plants performance. Solar absorption has a positive contribution to annual electricity productions, whereas heat loss and freeze protection temperature have a negative effect on electricity outputs. The results indicate that the novel receiver coupled with low melting temperature molten salt is the best configuration for improving the overall performance of the power plants. [ABSTRACT FROM AUTHOR]

• Novel CSP plant with sodium receiver, PCM storage and sCO 2 Brayton cycle. • Improvement of annual solar-to-electricity efficiency. • Minimum LCOE of 11.42 ¢AUD/kWh achieved in Alice Springs, Australia. • Benchmark analysis agains.t SAM with error < 2%. • Optimization of solar multiple, receiver size and storage capacity. To achieve further substantial reductions in the cost of concentrating solar-thermal power systems, recent efforts have been directed towards changing the working fluid in the receiver, adopting new approaches to thermal energy storage, and incorporating higher-efficiency power cycles. In this study, we present a novel CSP system configuration under development in ASTRI research program in Australia, incorporating a tubular sodium receiver, a high-temperature phase-change material storage unit, and a supercritical CO 2 power block. The model is implemented using the SolarTherm framework in the Modelica language, and simulated using Dymola software. The novel system was compared to a 'reference' system with a molten salt receiver, two-tank storage, and subcritical steam Rankine cycle. For verification, the reference system was also modelled using the System Advisor Model software, and differences of < 1% in annual receiver output and < 2% in net electrical output were achieved when comparing Modelica and SAM simulations, despite difference operating strategies and time resolution. The results of the analysis of the novel system showed an improvement of annual solar-to-electricity efficiency to 19.6%, up from 15.6% for the reference system. This was achieved as a result of higher power cycle efficiency, despite the reduction in optical and receiver efficiencies resulting from the higher working fluid temperature. The ASTRI system was economically optimised for financial performance using 2012 as the basis year, and reached a minimum levelised cost of electricity of 11.42 ¢AUD/kWh for a solar multiple of 2.2 and storage capacity of 8–9 h at the location of Alice Springs, Australia. [ABSTRACT FROM AUTHOR]

The air source heat pump water heater (ASHPWH) is an efficient and environmentally friendly system that is widely used in China. In this study, a refrigerant mixture R290/R600a/R13I1 with low global warming potential (GWP) and no ozone depletion potential (ODP) is proposed as drop-in replacement for R134a in ASHPWH. A theoretical model for an ASHPWH is developed based on MABLAB linking with REFPROP. The cycle performances of the proposed mixture, a contrast mixture, and R134a are analyzed under different working conditions, to investigate the feasibility of substitution. The annual performances of the ASHPWH that uses different refrigerants are also studied for comparison. The results show that compared with R134a, the proposed mixture has better performance with lower condensing pressure and compression ratio, and higher specific heating capacity and coefficient of performance (COP). The discharge temperature is also reasonable. Therefore, it is feasible to replace R134a with the proposed mixture. The ASHPWH using the proposed mixture has obvious advantages when the ambient temperature is very low. The annual average COP with the proposed mixture is 4.65, which is about 6.2% higher than with R134a, and the total equivalent warming impact (TEWI) can be reduced by 18.99%. • An eco-friendly refrigerant mixture R290/R600a/R13I1 is theoretically investigated. • The feasibility of replacing R134a with this refrigerant mixture in ASHPWH is studied. • The annual performance of an ASHPWH operated in Central China is analyzed. • The annual average COP can be improved by 6.2% with the refrigerant mixture than R134a. [ABSTRACT FROM AUTHOR]

The multi-condition operating characteristics of an organic Rankine cycle (ORC) are crucial to the development of the practical unit. This work developed a steady-state model of a small-scale ORC prototype built and tested in the lab. The influence of heat source/sink parameters, component design, and operation strategies are analyzed. It is found that the optimal output power and thermal efficiency correspond to the similar expander rotating speed but diverse working fluid mass flow rate. The higher mass flow rate is beneficial to the output power whereas deteriorates the thermal efficiency. Heat source temperature and flow rates mainly affect the unit output power while the ambient temperature and humidity influence both the output power and thermal efficiency. The condenser fouling resistance leads to a significant reduction of expander output power and system thermal efficiency. However, the effect of the evaporator fouling resistance could be neglected due to its sufficient redundant area. The long-term climate conditions and operating strategies profoundly impact the unit's off-design performance. The annual constant output power operation can be achieved by adjusting the working fluid mass flow rate. The thermal efficiency of the unit is damaged while pursuing the output power stability in winter and spring. • A small-scale ORC prototype using R245fa is built and tested. • A steady-state model of the ORC prototype is developed and validated. • The influence of heat source/sink parameters, component design is analyzed. • Multi-condition operating characteristics under two control strategies are compared. • Annual performance of the system applied for different scenarios is predicted. [ABSTRACT FROM AUTHOR]

Power to substitute natural gas (PtSNG) is a promising technology to store intermittent renewable electricity as synthetic fuel. Power surplus on the electric grid is converted to hydrogen via water electrolysis and then to SNG via CO2 methanation. The SNG produced can be directly injected into the natural gas infrastructure for long-term and large-scale energy storage. Because of the fluctuating behaviour of the input energy source, the overall annual plant efficiency and SNG production are affected by the plant operation time and the standby strategy chosen. The re-use of internal (waste) heat for satisfying the energy requirements during critical moments can be crucial to achieving high annual efficiencies. In this study, the heat recovery from a PtSNG plant coupled with wind energy, based on proton exchange membrane electrolysis, adiabatic fixed bed methanation and membrane technology for SNG upgrading, is investigated. The proposed thermal recovery strategy involves the waste heat available from the methanation unit during the operation hours being accumulated by means of a two-tanks diathermic oil circuit. The stored heat is used to compensate for the heat losses of methanation reactors, during the hot-standby state. Two options to maintain the reactors at operating temperature have been assessed. The first requires that the diathermic oil transfers heat to a hydrogen stream, which is used to flush the reactors in order to guarantee the hot-standby conditions. The second option entails that the stored heat being recovered for electricity production through an Organic Rankine Cycle. The electricity produced is used to compensate the reactors heat losses by using electrical trace heating during the hot-standby hours, as well as to supply energy to ancillary equipment. The aim of the paper is to evaluate the technical feasibility of the proposed heat recovery strategies and how they impact on the annual plant performances. The results showed that the annual efficiencies on an LHV basis were found to be 44.0% and 44.3% for the thermal storage and electrical storage configurations, respectively.

A Photovoltaic Thermal (PVT) collector produces heat and electricity simultaneously. Air-type PVT collector uses air as a transfer medium to take heat from PV back side surface. The performance of the air-type PVT collector is affected by design elements such as PV types, inside structures in heat collecting space (baffle or fins), the shape of the air pathway, etc. In this study, an advanced air-type PVT collector was designed with curved baffles (absorber) to improve thermal performance. Within the air-type PVT collector, PV cells were arranged in an interspaced design, and the curved baffles were located in the collecting space to increase heat efficiently. The absorber received solar radiation directly and was utilized as baffles for improving thermal performance. The air-type PVT collector was fabricated and tested in an outdoor environment considering the climatic conditions of Daejeon, Republic of Korea. In addition, based on experiment parameters and data, the annual thermal and electrical performances of the system were analyzed by simulation modeling using the TRNSYS program. Thermal and electrical efficiencies were 37.1% and 6.4% (according to module area) for outdoor test conditions, respectively. Numerical and experimental results were in good agreement with an error of 4% and 0.24% for thermal and electrical efficiencies, respectively. Annual heat gain was 644 kWh th/year, and generated power was 118 kWh el/year.

As cooling of Photovoltaic panel by water improves the electrical conversion efficiency and produces warm water as a by-product, photovoltaic thermal system is being used for cogeneration of electrical energy and hot water. In this study, the annual performance of a glazed photovoltaic thermal system (combination of PV module and solar flat plate collector) with storage tank was investigated by the dynamic computational model. The model was developed using MATLAB under actual hot water demand condition for co-generation electrical energy at Dire Dawa in Ethiopia. The computational model determines the electrical energy production and temperature of water at different points and other components of the PV-T system within a given time interval. In addition summaries of monthly and annual incident solar irradiance, electrical energy generation, thermal energy transported to storage and thermal energy supplied as hot water to end users are computed, considering the hourly hot water consumption pattern and storage size effect. The simulation, which is conducted for 20 m2 PV-T system, consists of 12 panels with each 1.64 m2 module areas resulted in generation 803 kWh/year thermal energy and 310 kWh/year electrical energy. The annual average electrical efficiency, thermal efficiency, hot water end use overall efficiency and co-generation (PV-T) efficiency of the system were 15.4%, 50.4%, 38%, and 65.8% respectively. The fraction of solar energy in meeting the heating load for hot water generation was 44.5% for 60℃ hot water supply temperature. Hence, that PV-T system can only be used for water preheating meeting at maximum half of the heating load in tropical area. [ABSTRACT FROM AUTHOR]

Abstract Solar aided (coal-fired) power generation (SAPG) technology has been approved to be an efficient way to use solar energy for power generation. However, most solar-rich areas are often short of cooling water supply, especially in China. The air-cooled condenser could alleviate this issue effectively for power plants in these areas. In this paper, a solar aided power generation with direct air-cool condenser (SAPG + ACC) plant is studied and optimized to maximize its performance. Due to the addition of solar heat in an SAPG plant, the exhaust steam flow rate leaving the turbine changes, especially in power-boost mode, which affects the turbine exit pressure and deviates the condenser from its designed operating condition. To achieve maximum net power output, the correlation among the optimum (turbine) exit pressure (OEP), the solar heat input and the ambient temperature, is obtained in this study. The annual plant's performances with four proposed operating strategies of the air-cooled condenser are compared and analyzed. The results show that for an SAPG + ACC plant, the operating Strategy.3, i.e. operated with the hourly OEP is the optimal one, resulting the plant has annual solar-to-electricity efficiency (SEE) of 17.82% and its levelized cost of electricity (LCOE) is of 0.09 $/kWh. Highlights • The impacts of the solar input on turbine exit pressure are revealed. • The optimal (turbine) exit pressure value under a certain condition is obtained. • Four proposed operating strategies of the air-cooled condenser are analyzed. • A sample daily operation procedure to demonstrate the operation is shown. [ABSTRACT FROM AUTHOR]

Highlights • Solar aided coal-fired power system is simulated for typical meteorological year. • Annual efficiency and levelized cost of electricity are characterized. • Annual coal consumption reduced over 14,000 tons for a 600 MW e power system. • Thermal storage capacity is optimized to achieve lowest cost of electricity. Abstract The integration of solar energy into coal-fired power plants has been proven as a potential approach in the utilization of solar energy to reduce coal consumption. Moreover, solar augmentation offers low cost and low risk alternatives to stand-alone solar thermal power plants. In this study, the annual performance of a solar tower aided coal-fired power (STACP) system is investigated, and the influence of thermal storage system capacity on the annual solar generating power and annual solar-to-electricity efficiency is explored. The thermal storage system capacity is optimized to obtain the lowest levelized cost of electricity (LCOE). At the same time, the influence and sensitivity of several important economic factors are explored and assessed. Results demonstrate that compared to a coal-fired power system, the reduction in the annual average coal consumption rate of the STACP system with high direct normal irradiance (DNI), medium DNI, and low DNI are 5.79, 4.52, and 3.22 g/kWh, respectively. At a minimum, the annual coal consumption can be reduced by 14,000 t in a 600 MW e power generation unit. Because the same solar field is considered under different DNI conditions, the LCOE in the high DNI, medium DNI, and low DNI scenarios are all fairly similar (6.37, 6.40, and 6.41 ¢/kWh, respectively). When the solar multiple is 3.0, the optimal thermal storage capacity of the STACP system, with high, medium, and low DNIs are 6.73, 4.42, and 2.21 h, respectively. The sensitivity analysis shows that the change in economic parameters exerts more influence on the STACP system with the high DNI compared with the other two scenarios. [ABSTRACT FROM AUTHOR]

The sensitivity analysis of key operating parameters on the average annual sub-profit in a group of three combine harvesters operating in companies providing agricultural services were analysed. Based on the results of the cost analysis, the following key operating parameters with the greatest influence on the costs were identified: the purchase price of the machine, the price of fuel, maintenance costs, personnel costs and annual performance. These parameters were used in the sensitivity analysis to investigate their effect on unit costs. Changing the above-mentioned parameters is calculated within ± 30% from their mean value. To perform a sensitivity analysis of the average annual sub-profit of combine harvesters, the unit price of mechanized work was additionally used. The results showed that greatest impact on both the average annual earnings of combines operation and on the changes in unit cost was those of the annual performance of the combine harvester, combine harvester purchase price and the cost of fuel. On the other hand, maintenance and personnel costs had a smaller influence concerning these changes of parameters.

The objective of this study is to optimize the performance of a two-phase injection (TPI) heat pump considering annual performance factor (APF) and life cycle climate performance (LCCP). The performances of non-injection (NI), vapor injection (VI), and TPI heat pumps are measured under various outdoor temperatures. Based on the measured data, artificial neural network models for the NI, VI, and TPI heat pumps are developed to predict the performance indexes during cooling and heating seasons. As a result, the TPI heat pump shows higher heating capacity than the NI and VI heat pumps with a lower compressor discharge temperature in cold weather conditions. Therefore, the application of the TPI has a merit on reducing the size of the heat pump due to its lower back-up heater loss and over-capacity penalty. When the objective function maximizes the APF for system optimization in three climate regions, the TPI heat pump shows a 1.4–2.7% higher APF than the NI heat pump, and a 11.1%–18.1% smaller optimum rated heating capacity. [ABSTRACT FROM AUTHOR]

This paper proposes a combination of a nuclear and a concentrated solar power (CSP) plant. Most of today’s operating nuclear reactor systems are producing saturated steam at relatively low pressure. This, in turn, limits their thermodynamic efficiency. Superheating of nuclear steam with solar thermal energy has the potential to overcome this drawback. An innovative configuration of a hybrid nuclear-CSP plant is assembled and simulated. It brings together a small pressurised water reactor and a parabolic trough solar field. The solar heat is transferred to nuclear steam to raise its temperature. Continuous superheating is provided through molten salts-based thermal energy storage (TES). The results from design point calculations show that solar superheating has the potential to increase nuclear plant electric efficiency significantly. Solar heat to electricity conversion efficiency defined as the ratio of extra generated power to collected solar energy reaches unprecedented rates of 52%. An off-design model was used to simulate 24-h operation for one year by simulating 8760 cases. Due to TES non-stop operation is manageable. [ABSTRACT FROM AUTHOR]

This paper describes a generic and systematic method to calculate the efficiency and the annual performance for Power-to-Gas (PtG) systems. This approach gives the basis to analytically compare different PtG systems using different technologies under different boundary conditions. To have a comparable basis for efficiency calculations, a structured break down of the PtG system is done. Until now, there has not been a universal approach for efficiency calculations. This has resulted in a wide variety of efficiency calculations used in feasibility studies and for business-case calculations. For this, the PtG system is divided in two sub-systems: the electrolysis and the methanation. Each of the two sub-systems consists of several subsystem boundary levels. Staring from the main unit, i.e. the electrolysis stack and/or methanation reactor, further units that are required to operate complete PtG system are considered with their respective subsystem boundary conditions. The paper provides formulas how the efficiency of each level can be calculated and how efficiency deviations can be integrated which are caused by the extended energy flow calculations to and from energy users and thermal losses. By this, a sensitivity analysis of the sub-systems can be gained and comprehensive goal functions for optimizations can be defined. In a second step the annual performance of the system is calculated as the ratio of useable output and energetic input over one year. The input is the integral of the annual need of electrical and thermal energy of a PtG system, depending on the different operation states of the plant. The output is the higher heating value of the produced gas and – if applicable – heat flows that are used externally. The annual performance not only evaluates the steady-state operating efficiency under full load, but also other states of the system such as cold standby or service intervals. It is shown that for a full system operation assessment and further system concept development, the annual performance is of much higher importance than the steady-state system efficiency which is usually referred to. In a final step load profiles are defined and the annual performance is calculated for a specific system configuration. Using this example, different operation strategies are compared. [ABSTRACT FROM AUTHOR]

This paper presents an innovative technology that can be used to deliver more renewable electricity production than the total electrical consumption of a building while covering the heat demand on a yearly basis. The technology concept uses a heat pump (HP), slightly modified to revert its cycle and generate electricity, coupled to a solar thermal collector roof. This reversible HP/organic Rankine cycle unit presents three operating modes: direct heating, HP and organic Rankine cycle. This work focuses on describing the dynamic model of the multi-component system followed by a techno-economic analysis of the system under different operational conditions. Sensitivity studies include: building envelope, climate, appliances, lighting and heat demand profiles. It is concluded that the HP/ORC unit can turn a single-family house into a PEB under certain weather conditions (electrical production of 3012 kWh/year and total electrical consumption of 2318 kWh/year) with a 138.8 m2solar roof in Denmark. [ABSTRACT FROM PUBLISHER]

• Satisfactory cooling met ratios are achieved with transient supply–demand matching. • A met ratio of 0.95 is obtained with a solar-to-cooling efficiency of 0.24. • The highest energy storage efficiency of the absorption thermal battery is 0.71. • The maximum energy storage density of 157.1 kWh/m3 is achieved. Efficient use of renewable energy, e.g., solar energy, is an important pathway towards net-zero energy buildings and carbon neutrality. However, renewable energy is difficult to be fully utilized due to its instability and intermittency. Thermal energy storage technologies applied in buildings can bridge the gap between renewable energy sources and heating/cooling demands. This study employs a solar absorption thermal battery (SATB) in a building for space cooling. The annual dynamic performance of the SATB is investigated and compared in four representative cities by simulation using an experimentally validated model, considering transient supply–demand matching. Besides, parametric studies are conducted for the SATB designed with different solar collector sizes and solution charges. Results indicate that the SATB achieves satisfactory cooling met ratios (MRs) in different climates when 0.49 m2 solar collector is equipped for each square meter of the serviced room. The highest cooling MR of 0.95 is obtained in Singapore, with an energy storage efficiency (ESE) of 0.66 for the ATB unit, a system ESE (solar-to-cooling) of 0.24, and an energy storage density (ESD) of 125.8 kWh/m3. The maximum ESEs of the ATB unit and the SATB system are 0.71 and 0.30, respectively. The highest ESD of 157.1 kWh/m3 is achieved by the SATB system, which is much higher than the sensible and latent thermal batteries for space cooling. This paper demonstrates a transient supply–demand matching operation scheme of the SATB system in different climates with excellent annual performance, which can facilitate the promotion and development of ATB technology. [ABSTRACT FROM AUTHOR]

Based on the typical meteorological year data of Shanghai city, annual performances of solar water heating (SWH) system and photovoltaic/thermal (PV/T) system are comparatively analyzed under three different cases. The results show that when only solar energy is used, the effective day number of SWH system is more than PV/T system under the same case every month; for the PV/T system, heat loss at the nighttime dissipates most of the absorbed solar energy under the continuous heating mode considering the nighttime heat loss case; initial water temperature determines system electric efficiency. On the whole, PV/T system offers competitive performance only under the auxiliary heating mode, no matter from the points of primary efficiency and static payback period. [ABSTRACT FROM AUTHOR]

Of all the renewable power generation technologies, solar tower power system is expected to be the most promising technology that is capable of large-scale electricity production. However, the optimization of heliostat field layout is a complicated process, in which thousands of heliostats have to be considered for any heliostat field optimization process. Therefore, in this paper, in order to optimize the heliostat field to obtain the highest energy collected per unit cost (ECUC), a mathematical model of a heliostat field and a hybrid algorithm combining particle swarm optimization algorithm and genetic algorithm (PSO-GA) are coded in Matlab and the heliostat field in Lhasa is investigated as an example. The results show that, after optimization, the annual efficiency of the heliostat field increases by approximately six percentage points, and the ECUC increases from 12.50 MJ/USD to 12.97 MJ/USD, increased about 3.8%. Studies on the key parameters indicate that: for un-optimized filed, ECUC first peaks and then decline with the increase of the number of heliostats in the first row of the field (Nhel1). By contrast, for optimized field, ECUC increases with Nhel1. What is more, for both the un-optimized and optimized field, ECUC increases with tower height and decreases with the cost of heliostat mirror collector. [ABSTRACT FROM AUTHOR]

In this paper, a tower solar collector-aided coal-fired power generation ( TSCACPG) system is proposed and studied in order to save the fossil energy and protect the environment. The integration scheme of tower solar collector and conventional coal-fired power plant is proposed. Based on the simulation platform TRNSYS, the TSCACPG system model is established and the dynamic performance of the TSCACPG system with the operating mode of coal saving is studied. The TSCACPG system performances of 1 day and 1 year are all discussed by using the DNI data of typical year in Chinese typical city of Dunhuang. Then, the sensitivity analysis of the TSCACPG system is carried out by changing the heliostat field scale (the size of the molten salt tower also changes accordingly). The annual performance of the TSCACPG system is also acquired. In consideration of the economic costs, the heliostat field area with the maximum annual solar-to-electric efficiency is selected as the optimal value. The results show that, for the case studied, the optimal heliostat field area is 101,400 m2, and the maximum annual solar-to-electric efficiency is 16.74%. And under the optimal situation, the standard coal consumption rate of the original coal-fired power plant is reduced from 301.5 g/ kWh to 294.5 g/ kWh. [ABSTRACT FROM AUTHOR]

The conversion of solar energy into chemical fuels is becoming more attractive and can be used for flexibly generating power; however, the poor annual solar-to-fuel efficiency severely hinders the application of the solar fuel process in the power system. Here, we study a mid-temperature solar fuel process having synergetic dual thermochemical reactions, in which solar heat at around 300 °C provides heat to drive methanol steam reforming and decomposition successively with a variation in the solar irradiance. At solar irradiance below 400 W/m 2 , the low-grade solar heat is used to drive methanol steam reforming, at solar irradiance above 400 W/m 2 , the solar heat is combined with methanol decomposition. The solar thermochemical performances of the proposed solar fuel process were analyzed for typical days and a full year. In contrast to the individual solar-driven methanol decomposition process which mainly utilize solar irradiance above 400 W/m 2 , the annual average solar-to-fuel efficiency in the synergetic process, which can utilize wider solar irradiance from 100 to 1000 W/m 2 , is improved to 60%, and the annual average solar-to-electricity efficiency is improved to 21%. The promising results can offer a possibility of greatly improving the annual average performance of the solar fuel process, especially for enlarging the effective utilization of lower solar irradiance. [ABSTRACT FROM AUTHOR]

Integrating solar energy into a conventional fossil-fuel fired power plant through solar-aided coal-fired power generation (SACPG) mechanism has been proven to be an efficient way to use solar energy for power generation purposes. However, due to the rather intermittency of solar radiation, SACPG systems always work under off-design conditions. In this paper, hourly based annual performances of a SACPG system was simulated and analyzed with various solar field sizes and thermal energy storage (TES) capacity under different (plant) load conditions in a 330 MW power plant case study. The results indicate that, TES system could stabilize the solar thermal output and improve the stability of the SACPG system at different loads. And it could also improve solar contribution in the power generation and annual peak solar-to-electricity efficiency. Through case study, the minimum levelized energy of costs and corresponding aperture area in this case are $0.0629/kW h, 1.413 × 10 5 m 2 for 100% load, $0.0654/kW h, 9.42 × 10 4 m 2 for 75% load, and $0.0730/kW h and 5.89 × 10 4 m 2 for 50% load, respectively. And the corresponding optimized TES hour with different loads is found to be 0.5 h. The values are relatively lower than the reference trough plant. [ABSTRACT FROM AUTHOR]

The compression-assisted air source absorption heat pump (CASAHP) is a promising alternative heating system in severe operating conditions. In this research, parameter studies on the annual performance under various compression ratios (CRs) and source temperatures are performed to achieve the maximum energy saving rates (ESRs). Economic analyses of the CASAHP under different CRs and partial-design ratios are conducted to obtain an optimal design that considers both energy savings and economy improvements. The results show that the optimal CR becomes higher in colder regions and with lower heat source temperatures. For a source temperature of 130 °C, the optimal CR values in all of the cities are within 2.0. For source temperatures from 100 to 130 °C, the maximum ESR is in the range of 17.7–29.2% in the studied cities. The efficiency improvement rate (EIR) caused by compression in a severe source condition can reach 10.0–20.0%. From the viewpoint of economy, the relative investment of CASAHP is reduced to 30–60% with a CR of 2.0–3.0. With a 2–6% sacrifice in ESR, the payback period can be reduced from 12–32 to 5–9 years using compression. Partial-design of the CASAHP can further reduce the payback period to 3–6 years with a partial-design ratio of 50% and a CR of 2.8. Additionally, CRs and partial-design ratios are designed comprehensively by seeking the maximum ESR for a given acceptable payback period. [ABSTRACT FROM AUTHOR]

Energy efficiency for room air conditioners has received increasing attention in recent years with the intense emphasis on environmental concern and energy consumption. As the main energy consumption component of air conditioner, compressor awaits further work to accomplish the transition of performance evaluation from one operation condition to its actual usage. In the present study, an evaluation index called annual efficiency is proposed to rate the annual performance of air conditioner compressor. Experimental study is conducted on four variable-speed compressors, and the results show that the best fit determined from annual efficiency is different from that of ASHRAE standard. The compressor efficiency and dynamic pressure are quite different at rated and half-capacity test conditions. Compressor running under half-capacity conditions is more energy efficient and peak phenomenon of dynamic pressure is less obvious when compared with rated conditions. Moreover, more attention should be paid to half-capacity conditions to improve the annual efficiency of compressor and energy-saving capabilities of air conditioners. [ABSTRACT FROM AUTHOR]

This paper presents an approach to quantify the effect of evaporator maldistribution on operating costs of air–water heat pumps. In the proposed simulation model maldistribution is induced by two parameters describing refrigerant phase and air flow distribution. Annual operating costs are calculated based on heat pump performance at distinct operating conditions. Results show that percentage increase of operating costs is similar for the three considered climate zones, even though the effect of maldistribution on heat pump performance varies with operating conditions. Differences in terms of absolute cost increase for the climate zones arise mainly due to a varying number of operating hours. Absolute cost increase is considerable in the average and especially colder climate zone and can only partly be reduced by enlarging the evaporator. [ABSTRACT FROM AUTHOR]

In this study a methodology is applied to quantify the effect of evaporator maldistribution on operating costs of air–water heat pumps. The approach is used to investigate the cost-effectiveness of two technologies enabling to counteract maldistribution: a flash gas bypass setup and the individual superheat control in parallel evaporator channels. In the total cost of ownership analysis, different scenarios for climatic conditions, severity of maldistribution, and economic framework are considered. Results show that the flash gas bypass system is cost-effective only in a few conditions, namely severe maldistribution, high electricity prices, and colder climate. Investment in the individual superheat control technology, however, can be quickly amortized in many scenarios. For the warmer climate zone with a small number of operating hours counteracting of maldistribution does not pay off under the used economic assumptions. [ABSTRACT FROM AUTHOR]

A hybrid air-cooled condenser (ACC) concept has demonstrated to provide performance benefits over a conventional ACC. Additional to the thermal performance, the cost effectiveness should also be considered to determine the commercial viability, and therefore this study interrogates the techno-economic feasibility of a hybrid ACC at six locations with a ∼238 MW steam turbine representative of a typical CSP or NGCC plant. In this paper the hybrid ACC, is compared to a conventional ACC in terms of annual performance and annualized cost. The annualized cost of the hybrid ACC relative to the conventional ACC is expressed as a cost ratio φₐ, and consideration is given to a range of water and hybrid unit capital costs. The hybrid ACC is 12% more capital intensive per street, but the hybrid ACC requires about ⅓ fewer units and consume 30% less auxiliary power. This results in a higher annual net power generation while the annual specific water consumption ranged between 0.31 kL/MWh and 0.69 kL/MWh across the six sites. At drier sites the hybrid ACC can be oversized to reduce the water consumption with 50%. The cost evaluation demonstrates that the hybrid ACC is best suited to locations with low to moderate humidity. • A hybrid air-cooled condenser (ACC) provides improved performance. • The hybrid ACC is more capital intensive, but require fewer units. • Compared to a conventional ACC the hybrid ACC is economically viable. • The hybrid ACC is best suited for low to moderate humidity locations. • At drier sites the system can be oversized to reduce the water consumption. [ABSTRACT FROM AUTHOR]

Abstract: A technical and economical comparison of two parabolic trough CSP plants is made using full thermodynamic models. One plant is a hybrid plant with a natural gas fired booster in order to reach 540°C live steam temperature. The design of this plant is similar to that of the Shams One plant and a meteorological dataset for the site in Abu Dhabi was used for the annual performance calculations. The second plant is a parabolic trough plant using molten salt as heat transfer fluid in the solar field as well as storage material. Both plants are equipped with almost the same power block and show similar annual performance. The molten salt plant shows a cost reduction potential and the same or even higher flexibility and dispatch ability as the hybrid plant. [Copyright &y& Elsevier]

Highlights: [•] The performance of a SAFHCPG system at design point is analyzed. [•] The solar radiation intensity and the electrical load demand on the grid side are considered in the annual performance analysis. [•] The optimum aperture area of the solar field has been discussed based on the annual performance. [ABSTRACT FROM AUTHOR]

Abstract: Combined solar and heat pump systems have a large potential to reduce CO2 and other emissions from the sector of domestic hot water preparation and space heating. Subtask C of the IEA SHC Task 44/HPP Annex 38 deals with modeling and simulation of these systems. A review of component models for the simulation of combined solar and heat pump heating systems has been carried out with a special focus on the particularities of the combination of solar thermal collectors with heat pumps. Some of these particularities are effects of water vapor condensation on the surface of collector absorbers operated below the dew point, refrigeration cycles using more than one heat exchanger for the evaporator in order to use solar heat in addition to a conventional heat source, the effect of higher source temperature for the heat pump when solar heat is used, or the regeneration of ground heat sources with heat from solar collectors. [Copyright &y& Elsevier]

Abstract: Solar thermal plants are among the most promising technologies to replace fossil fuel stationary applications, and within solar thermal technologies, parabolic troughs are considered the most mature application in the market. This paper compares different solar field technologies, in terms of both performance at design conditions and annual energy production; an in-house code, PATTO, was used to perform energy balances. We considered a reference case reflecting state-of-the-art Nevada Solar One, which showed a design efficiency and annual average efficiency of 22.4% and 15.3%, respectively, in agreement with actual performance. If solar salts are used as heat-transfer fluid instead of synthetic oil (e.g. ARCHIMEDE plant), the efficiency improved within the range of 6% due to the higher maximum temperature. Further thermodynamic advantages can be achieved with a direct steam generation plant; the main drawback is the more complex transient control and no commercially available storage systems. We propose the innovative Milan configuration, which combines advantages of direct steam evaporation and the use of a heat-transfer fluid, to investigate both synthetic oil and solar salts for steam superheating and reheating. Results for this configuration are very promising, with a sun-to-electric annual average efficiency of 17.8%, which is 16% higher than the reference case. Detailed daily simulations showed that advantages are more significant at low radiation. However, the plant should be optimized on an economic basis and we will discuss this in a future paper. [Copyright &y& Elsevier]