Solar heating system is widely used recently. Heat storage equipment is the guarantee for steady performance of solar heating system. A design of latent heat storage exchanger with submerged coil was introduced with t...Solar heating system is widely used recently. Heat storage equipment is the guarantee for steady performance of solar heating system. A design of latent heat storage exchanger with submerged coil was introduced with the structure, working principle, and the main advantages. This heat exchanger was integrated into solar heating system as the heat storage equipment. Advantage comparison of the designed heat exchanger in solar heating system with hot water tank was carried out. The analysis results show that the latent heat storage exchanger is superior to hot water tank obviously. The heat exchanger performance parameters and variations of these parameters are got： （1） with the increase of phase change material （PCM） volume ratio, heat storage equipment volume ratio decreases; （2） heat storage efficiency has the same varying tendency with outdoor and air temperature; while the bigger PCM volume ratio is, the weaker the effect of outdoor air temperature on heat storage efficiency is; （3） heat storage capacity and heat storage efficiency increase together; when PCM volume ratio is big, heat storage efficiency is high and the system can begin operating effcienfly and quickly; （4） with the increase of heat storage capacity, life cyde operation cost （LCOC） of system increases gradually in high speed; but with the increase of PCM volume ratio, the difference between the two systems LCOCs becomes smaller and smaller; （5） the reasonable range of PCM volume ratio is 0.5 - 0.7. Temperature characteristic analysis shows that, with the filled PCM, heat storage medium temperature presents several segments at different time, under conditions of different heat storage capacity and different PCM state.展开更多
The theoretical analysis discussed in this work is a suitable mathematical tool by which the performance of the proposed collector can be predicted. The obtained experimental results coincide with the obtained theoret...The theoretical analysis discussed in this work is a suitable mathematical tool by which the performance of the proposed collector can be predicted. The obtained experimental results coincide with the obtained theoretical data obtained from the devised computer program. Controlled output temperature can be obtained from the proposed system. The performance of the tested collector under the proposed intermittent flow conditions overcomes that of the conventional thermosyphone flow collector.展开更多
The performance of solar heating systems is significantly influenced by outdoor weather fluctuations and building heating loads,leading to dynamic variations that undermine the efficacy of rule-based control(RBC)strat...The performance of solar heating systems is significantly influenced by outdoor weather fluctuations and building heating loads,leading to dynamic variations that undermine the efficacy of rule-based control(RBC)strategies.Additionally,the hydraulic and thermal time-delay characteristics frequently lead to delays in control points for real-time optimization(RTO)control strategies.While Model Predictive Control(MPC)effectively addresses these dynamic and time-delay issues in solar heating systems,its substantial computational demands limit its real-world applications.To overcome these challenges,this study proposes a Model-Free Predictive Control(MFPC)approach utilizing Deep reinforcement learning(DRL).Through TRNSYS simulations,the study conducts a comparison of the performance and energy consumption of RBC and MFPC systems,focusing on a residential solar heating system in Lhasa,Xizang as a case study.The results demonstrate that the MFPC method reduces unmet heating demand by 31%compared to traditional RBC strategies,improves solar collection efficiency by nearly 12%,and decreases tank heat loss by 2.2%.When accounting for thermal storage effects,the optimized MFPC strategy achieves a reduction in net energy consumption of 25.6%.展开更多
The goal of this study is to investigate the effect of key design parameters on the thermal performance of the packed bed heat storage device by numerical calculation.A one-dimensional,non-equilibrium packed bed laten...The goal of this study is to investigate the effect of key design parameters on the thermal performance of the packed bed heat storage device by numerical calculation.A one-dimensional,non-equilibrium packed bed latent heat storage mathematical model was established and the applicability of the model was verified.The results demonstrate that the inlet temperature of the heat transfer fluid(HTF)had the greatest influence on each index.When the inlet temperature increased from 333 K to 363 K,exergy destruction increased threefold,effective heat storage time decreased by 67%,effective heat storage increased by 38%,and exergy efficiency decreased by 11%.The decrease of the capsule diameter had a positive effect on each evaluation index.According to the sensitivity analysis,the order of importance of each parameter within their variation range was HTF inlet temperature,HTF flow rate,PCM capsule size and PCM initial temperature.展开更多
Temperature-swing adsorption(TSA)is an effective technique for CO_(2) capture,but the temperature swing procedure is energy-intensive.Herein,we report a low-energy-consumption system by combining passive radiative coo...Temperature-swing adsorption(TSA)is an effective technique for CO_(2) capture,but the temperature swing procedure is energy-intensive.Herein,we report a low-energy-consumption system by combining passive radiative cooling and solar heating for the uptake of CO_(2) on commercial activated carbons(CACs).During adsorption,the adsorbents are coated with a layer of hierarchically porous poly(vinylidene fluoride-co-hexafluoropropene)[P(VdF-HFP)HP],which cools the adsorbents to a low temperature under sunlight through radiative cooling.For desorption,CACs with broad absorption of the solar spectrum are exposed to light irradiation for heating.The heating and cooling processes are completely driven by solar energy.Adsorption tests under mimicked sunlight using the CACs show that the performance of this system is comparable to that of the traditional ones.Furthermore,under real sunlight irradiation,the adsorption capacity of the CACs can be well maintained after multiple cycles.The present work may inspire the development of new temperature swing procedures with little energy consumption.展开更多
Ground source heat pump systems demonstrate significant potential for northern rural heating applications;however,the effectiveness of these systems is often limited by challenging geological conditions.For instance,i...Ground source heat pump systems demonstrate significant potential for northern rural heating applications;however,the effectiveness of these systems is often limited by challenging geological conditions.For instance,in certain regions,the installation of buried pipes for heat exchangers may be complicated,and these pipes may not always serve as efficient low-temperature heat sources for the heat pumps of the system.To address this issue,the current study explored the use of solar-energy-collecting equipment to supplement buried pipes.In this design,both solar energy and geothermal energy provide low-temperature heat to the heat pump.First,a simulation model of a solar‒ground source heat pump coupling system was established using TRNSYS.The accuracy of this model was validated through experiments and simulations on various system configurations,including varying numbers of buried pipes,different areas of solar collectors,and varying volumes of water tanks.The simulations examined the coupling characteristics of these components and their influence on system performance.The results revealed that the operating parameters of the system remained consistent across the following configurations:three buried pipes,burial depth of 20 m,collector area of 6 m^(2),and water tank volume of 0.5 m^(3);four buried pipes,burial depth of 20 m,collector area of 3 m^(2),and water tank volume of 0.5 m^(3);and five buried pipes with a burial depth of 20 m.Furthermore,the heat collection capacity of the solar collectors spanning an area of 3 m^(2)was found to be equivalent to that of one buried pipe.Moreover,the findings revealed that the solar‒ground source heat pump coupling system demonstrated a lower annual cumulative energy consumption compared to the ground source heat pump system,presenting a reduction of 5.31%compared to the energy consumption of the latter.展开更多
This paper aims at presenting an application developed in Java for optimizing the design of centralized solar water heating systems with forced circulation, based on the f-chart method. The program uses data from the ...This paper aims at presenting an application developed in Java for optimizing the design of centralized solar water heating systems with forced circulation, based on the f-chart method. The program uses data from the Brazilian Solar Atlas, performance data of flat plate collectors and thermal reservoirs from the standardized tests run within the Brazilian Labeling Program, and values of water consumption of appliances defined by the ABNT. The program finds the inclination of the collector that maximizes the annual solar fraction, or for the winter, and enables the use of arrays in series and parallel collectors. From the investment costs and O ＆ M （operations and maintenance） of solar heating systems, the program carries out economical analysis using classical parameters as net present value, discounted payback and internal rate of return. The program was validated through examples from the book of Duffle ＆ Beckman and also by comparison with the results from a project developed at UFRGS, having obtained good agreement.展开更多
Catalytic converting CO2 into fuels with the help of solar energy is regarded as‘dream reaction’,as both energy crisis and environmental issue can be mitigated simultaneously.However,it is still suffering from low e...Catalytic converting CO2 into fuels with the help of solar energy is regarded as‘dream reaction’,as both energy crisis and environmental issue can be mitigated simultaneously.However,it is still suffering from low efficiency due to narrow solar-spectrum utilization and sluggish heterogeneous reaction kinetics.In this work,we demonstrate that catalytic reduction of CO2 can be achieved over Au nanoparticles(NPs)deposited rutile under full solar-spectrum irradiation,boosted by solar-heating effect.We found that UV and visible light can initiate the reaction,and the heat from IR light and local surface-plasmon resonance relaxation of Au NPs can boost the reaction kinetically.The apparent activation energy is determined experimentally and is used to explain the superior catalytic activity of Au/rutile to rutile in a kinetic way.We also find the photo-thermal synergy in the Au/rutile system.We envision that this work may facilitate understanding the kinetics of CO2 reduction and developing feasible catalytic systems with full solar spectrum utilization for practical artificial photosynthesis.展开更多
It is introduced the current situation and development for solar heating technology including passive solar heating and solar heating combisystems in China in this paper. Combined with the engineering application proj...It is introduced the current situation and development for solar heating technology including passive solar heating and solar heating combisystems in China in this paper. Combined with the engineering application projects, the author gave the technical and economic analysis of the passive solar and solar heating combisystems in China and summarized the developing obstacle and the spreading tactics for raising marketing of the solar heating in China.展开更多
Realizing all-day and all-weather energy-saving heating is crucial for mitigating the global energy and ecology crisis.Electric/solar heating are two promising heating approaches,yet materials with high elec-trical co...Realizing all-day and all-weather energy-saving heating is crucial for mitigating the global energy and ecology crisis.Electric/solar heating are two promising heating approaches,yet materials with high elec-trical conductivity,high solar absorptivity,and low infrared emissivity at the same time are rare in na-ture,which are highly anticipated and of great significance for highly efficient electric/solar heating.In this work,we demonstrate that Ti_(3)C_(2)T_(x) MXene with low IR emissivity(14.5%)fills the gap in the absence of the above materials,exhibiting a remarkable electric/solar heating performance.The saturated heating temperature of Ti_(3)C_(2)T_(x) film reaches a record-high value of 201°C at a low driving voltage of 1.5 V,and reaches 84.3°C under practical solar irradiation(750 W/m^(2))with a high solar to the thermal conversion efficiency of 75.3%,which is far superior to other reported materials.Meanwhile,the low IR emissivity endows Ti_(3)C_(2)T_(x) with a remarkable passive radiative heating capability of 7.0°C,ensuring zero-energy heating without electric/solar energy supply.The intrinsic characteristic of high electrical conductivity,high solar absorptivity,and low IR emissivity makes Ti_(3)C_(2)T_(x) unique existence in nature,which is highly promising for all-day and all-weather energy-saving heating.展开更多
Parabolic trough collectors （PTCs） are employed for a variety of applications including steam generation and hot water generation. This paper deals with the experimental results and an economic analysis of a new fib...Parabolic trough collectors （PTCs） are employed for a variety of applications including steam generation and hot water generation. This paper deals with the experimental results and an economic analysis of a new fibre reinforced plastic （FRP） based solar PTC with an embedded electronic controlled tracking system designed and developed for hot water generation in a restaurant in Madurai, India. The new collector performance has been tested according to ASHRAE Standard 93 （1986）. The performance of a new PTC hot water generation system with a well mixed hot water storage tank is investigated by a series of extensive tests over ten months period. The average maximum storage tank water temperature observed was 74.91℃, when no energy is withdrawn from the tank to the load during the collection period. The total cost of the new economic FRP based solar PTC for hot water generation with an embedded electronic controlled tracking system is Rs. 25000 （US$ 573） only. In the present work, life cycle savings （LCS） method is employed for a detailed economic analysis of the PTC system. A computer program is used as a tool for the economic analysis. The present worth of life cycle solar savings is evaluated for the new solar PTC hot water generation system that replaces an existing electric water heating system in the restaurant and attains a value of Rs. 23171.66 after 15 years, which is a significant saving. The LCS method and the MATLAB computer simulation program presented in this paper can be used to estimate the LCS of other renewable energy systems.展开更多
Indoor thermal comfort and passive solar heating technologies have been extensively studied.However,few studies have explored the suitability of passive solar heating technologies based on differentiated thermal comfo...Indoor thermal comfort and passive solar heating technologies have been extensively studied.However,few studies have explored the suitability of passive solar heating technologies based on differentiated thermal comfort demands.This work took the rural dwellings in Northwest China as the research object.First,the current indoor and outdoor thermal environment in winter and the mechanism of residents’differentiated demand for indoor thermal comfort were obtained through tests,questionnaires,and statistical analysis.Second,a comprehensive passive optimized design of existing buildings was conducted,and the validity of the optimized combination scheme was explored using DesignBuilder software.Finally,the suitability of passive solar heating technology for each region in Northwest China was analyzed based on residents’differentiated demand for indoor thermal comfort.The regions were then classified according to the suitability of the technology for these.The results showed that the indoor heating energy consumption was high and the indoor thermal environment was not ideal,yet the solar energy resources were abundant.Indoor comfort temperature indexes that match the functional rooms and usage periods were proposed.For the buildings with the optimized combination scheme,the average indoor temperature was increased significantly and the temperature fluctuation was decreased dramatically.Most regions in Northwest China were suitable for the development of passive solar heating technology.Based on the obtained suitability of the technology for the regions of Northwest China,these were classified into most suitable,more suitable,less suitable,and unsuitable regions.展开更多
In this project, different combinations of solar energy and heat pump systems for preparation of DHW （domestic hot water） and space heating of buildings are analyzed through dynamic system simulations in TRNSYS （Tr...In this project, different combinations of solar energy and heat pump systems for preparation of DHW （domestic hot water） and space heating of buildings are analyzed through dynamic system simulations in TRNSYS （Transient System Simulation Program）. In such systems, solar thermal energy can be used, on one hand, directly to charge the buffer storage and, on the other hand, as heat source for the evaporator oftbe HP （heat pump）. In this work systems, in which solar heat is only used directly （parallel operation of solar and HP）, systems using the collectors also as a heat source for the HP are analyzed and compared to conventional air HP systems. With a combined parallel solar thermal HP system, the system performance compared to a conventional HP system can be significantly increased. Unglazed selectively coated collectors as source for the HP have the advantage that the collector can be used as an air heat exchanger. If solar radiation is available and the collector is used as source for the HP, higher temperatures at the evaporator of the HP can be achieved than with a conventional air HP system.展开更多
A computer analysis of solar heating has been performed for Palestine. Results are presented for a prototype building using either fuel oil or gas under different heating loads in three climatic regions （Jordan valle...A computer analysis of solar heating has been performed for Palestine. Results are presented for a prototype building using either fuel oil or gas under different heating loads in three climatic regions （Jordan valley, coastal, and hilly）. Cumulative cost flows are compared for the life-cycle present value technique. Optimum design magnitudes are determined for maximum life-cycle savings. The payback period for capital invested in a solar system, and total savings are found for the optimum conditions. Variations of system performance are estimated. The effects of collector slope, proportionate storage tank volume, heat-exchanger parameters, and the design load on system performance are studied. Finally the economics of solar heating in Palestine are discussed and recommendations are made for increased utilization of solar energy.展开更多
Energy supply is one of the major challenges facing China. The rate at which demand is outstripping supply led the Standing Committee of the National People's Congress to pass the Renewable Energy Law of the PRC a...Energy supply is one of the major challenges facing China. The rate at which demand is outstripping supply led the Standing Committee of the National People's Congress to pass the Renewable Energy Law of the PRC at its fourteenth session in February, 2005. The document points out that 'The law is legislated to promote exploitation and utilization of renewable energy, increase the supply of energy sources, improve the structure of energy sources, ensure the security of energy sources, protect the environment, and achieve the sustainable development of economy and society.' 'Renewable energy under the law is non-fossil energy, including wind, solar, water, biomass, geothermal, and ocean energies, etc.' 'The nation determines that the exploitation and utilization of renewable energy takes precedence in the development of energy sources, and propels the establishment and development of the renewable energy market.' 'The Standardization Administrative Department of the State Council should constitute and promulgate the national grid-connection standards for renew- able electricity, and other national technical standards that are related to renewable energy technology and products.'展开更多
In this article,the effect of using water/zinc oxide nanofluid as a working fluid on the performance of solar collector is investigated experimentally.The volumetric concentration of nanoparticles is 0.4%,and the part...In this article,the effect of using water/zinc oxide nanofluid as a working fluid on the performance of solar collector is investigated experimentally.The volumetric concentration of nanoparticles is 0.4%,and the particle size is 40 nm,and the mass flow rate of the fluid varies from 1 to 3 kg/min.For this experiment,a device has been prepared with appropriate measuring instruments whose energy source is solar radiation.The solar energy absorbed by the flat plate collector is absorbed by the nanofluid of water/zinc oxide.The nanofluid is pumped to the consumer,a heat exchanger,where it heats the water.The temperature,radiation level,flow rate,and pressure in different parts of the device were measured.The pressure drop and the heat transferred are the most important results of this experimental work.The ASHRAE standard is used to calculate efficiency.The results showed that the use of water/zinc oxide nanofluid increases the collector performance compared to water.For 1 kg/min of mass flow rate,the nanofluids have a 16% increase in efficiency compared to water.From the results,it can be concluded that the choice of optimum mass flow rate in both water and nanofluid cases increases efficiency.展开更多
In this paper,we studied theoretically and numerically heated losses of a flat solar collector to model the solar water heating system for the Kazakhstan climate condition.For different climatic zones with a growing c...In this paper,we studied theoretically and numerically heated losses of a flat solar collector to model the solar water heating system for the Kazakhstan climate condition.For different climatic zones with a growing cost for energy or lack of central heating systems,promising is to find ways to improve the energy efficiency of the solar system.The mathematical model(based on ordinary differential equation)simulated the solar system work process under different conditions.To bridge the modeling and real values results,we studied the important physical parameters such as loss coefficient,Nu,Ra,and Pr values.They impacted the efficiency of flat solar collectors and heat losses of the system.The developed mathematical models,the design and composition of the software and hardware complex,and automated control and monitoring systems allow solar hot water heating systems to increase the energy efficiency of life support systems and heat supply of buildings by reducing energy consumption for heat supply.The simulation result showed that during the daytime,the temperature of water in the collector is 70°C;the storage of heated water since heated water is cooled at night.We defined that a work period of the system can be extended with high efficiency(April-October)for Almaty region.展开更多
Al_(2)O_(3)/SiC composite ceramics were prepared fromα-Al_(2)O_(3) and SiC by a pressureless sinter method in this study.The effect of SiC contents on the mechanic properties,phase compositions and microstructure is ...Al_(2)O_(3)/SiC composite ceramics were prepared fromα-Al_(2)O_(3) and SiC by a pressureless sinter method in this study.The effect of SiC contents on the mechanic properties,phase compositions and microstructure is studied.Experimental results show that the vickers hardness,wear resistance and thermal conductivity of the samples increase with the increase in the SiC content,and the hardness of the sample reaches 16.22 GPa,and thermal conductivity of the sample reaches 25.41 W/(m.K)at room temperature when the SiC content is 20 wt%(B5)and the sintering temperature is at 1640℃.Higher hardness means higher scour resistance,and it indicates that the B5 material is expected to be used for the solar heat absorber of third generation solar thermal generation.The results indicate the mechanism of improving mechanical properties of Al_(2)O_(3)/SiC composite ceramics:SiC plays a role in grain refinement that the grain of SiC inhibits the grain growth of Al_(2)O_(3),while the addition of SiC changes the fracture mode from the intergranular to the intergranular-transgranular.展开更多
China is the largest solar water heater producer and market in the world.Despite the fast growth and an installed capacity that accounts for the majority of the global gross,China's per capita solar hot water capa...China is the largest solar water heater producer and market in the world.Despite the fast growth and an installed capacity that accounts for the majority of the global gross,China's per capita solar hot water capacity is still very low,implying a huge margin of market potential;and the recognition of the industry in the global market is handicapped by the scattered scale of production and inconsistent product quality.To ensure continued growth of China's solar water heating(SWH) industry,Chinese Government has established a series of national SWH standards,three national testing centers,and a certification program to lay the foundation for the development of the Golden Sun product labeling system.China General Certification Center(CGC) developed the Golden Sun product certification and labeling system on a pass/fail basis evaluating with established criteria.The system was designed to help manufacturers acclimate to explicit consistent requirements and to identify and fix the deficiencies in the design and execution of the program itself.Timely revision and integration of the national standards are recommended to accommodate the test procedures and requirements to new technologies and the evolving SWH market.Strict implementation of the Golden Sun certification and labeling system are suggested to avail improving the quality control and forging internationally reputable brands of Chinese solar water heating products.展开更多
At the limited roof north-south （N-S） width of a building, for the array with multirow collectors based on no shading at winter solstice noon and sloped at latitude, this paper studied the shading and the radiant en...At the limited roof north-south （N-S） width of a building, for the array with multirow collectors based on no shading at winter solstice noon and sloped at latitude, this paper studied the shading and the radiant energy striking on solar collector array. Based on Kunming solar radiation data, the annual and monthly solar radiant energy striking on multi-array collectors was analyzed and estimated, from no shading to partial shading by adding 1-3 collector row, at the slopes of 10°, 15°, 20°, 25°, 30°, 35° and 40°, respectively. The results showed that properly increasing the row number by reducing the slope of collectors was reasonable in order to get more annual radiant energy. Adding 1 row at 10° of slope was economical for Kunming, based on the 5-row array at 25°. And adding collector row by 20% at 10° of slope could increase the radiant energy striking on the array by 19%.展开更多
基金National Natural Science Foundation of China(No.21106149)
文摘Solar heating system is widely used recently. Heat storage equipment is the guarantee for steady performance of solar heating system. A design of latent heat storage exchanger with submerged coil was introduced with the structure, working principle, and the main advantages. This heat exchanger was integrated into solar heating system as the heat storage equipment. Advantage comparison of the designed heat exchanger in solar heating system with hot water tank was carried out. The analysis results show that the latent heat storage exchanger is superior to hot water tank obviously. The heat exchanger performance parameters and variations of these parameters are got： （1） with the increase of phase change material （PCM） volume ratio, heat storage equipment volume ratio decreases; （2） heat storage efficiency has the same varying tendency with outdoor and air temperature; while the bigger PCM volume ratio is, the weaker the effect of outdoor air temperature on heat storage efficiency is; （3） heat storage capacity and heat storage efficiency increase together; when PCM volume ratio is big, heat storage efficiency is high and the system can begin operating effcienfly and quickly; （4） with the increase of heat storage capacity, life cyde operation cost （LCOC） of system increases gradually in high speed; but with the increase of PCM volume ratio, the difference between the two systems LCOCs becomes smaller and smaller; （5） the reasonable range of PCM volume ratio is 0.5 - 0.7. Temperature characteristic analysis shows that, with the filled PCM, heat storage medium temperature presents several segments at different time, under conditions of different heat storage capacity and different PCM state.
文摘The theoretical analysis discussed in this work is a suitable mathematical tool by which the performance of the proposed collector can be predicted. The obtained experimental results coincide with the obtained theoretical data obtained from the devised computer program. Controlled output temperature can be obtained from the proposed system. The performance of the tested collector under the proposed intermittent flow conditions overcomes that of the conventional thermosyphone flow collector.
基金supported by the National Natural Science Foundation of China(Project Nos.U23A20657,U20A20311).
文摘The performance of solar heating systems is significantly influenced by outdoor weather fluctuations and building heating loads,leading to dynamic variations that undermine the efficacy of rule-based control(RBC)strategies.Additionally,the hydraulic and thermal time-delay characteristics frequently lead to delays in control points for real-time optimization(RTO)control strategies.While Model Predictive Control(MPC)effectively addresses these dynamic and time-delay issues in solar heating systems,its substantial computational demands limit its real-world applications.To overcome these challenges,this study proposes a Model-Free Predictive Control(MFPC)approach utilizing Deep reinforcement learning(DRL).Through TRNSYS simulations,the study conducts a comparison of the performance and energy consumption of RBC and MFPC systems,focusing on a residential solar heating system in Lhasa,Xizang as a case study.The results demonstrate that the MFPC method reduces unmet heating demand by 31%compared to traditional RBC strategies,improves solar collection efficiency by nearly 12%,and decreases tank heat loss by 2.2%.When accounting for thermal storage effects,the optimized MFPC strategy achieves a reduction in net energy consumption of 25.6%.
基金supported by the National Key R8cD Program of China(No.2018YFB0905104)the Science and Technology Planning Project of Jilin Province(No.20180201006SF).
文摘The goal of this study is to investigate the effect of key design parameters on the thermal performance of the packed bed heat storage device by numerical calculation.A one-dimensional,non-equilibrium packed bed latent heat storage mathematical model was established and the applicability of the model was verified.The results demonstrate that the inlet temperature of the heat transfer fluid(HTF)had the greatest influence on each index.When the inlet temperature increased from 333 K to 363 K,exergy destruction increased threefold,effective heat storage time decreased by 67%,effective heat storage increased by 38%,and exergy efficiency decreased by 11%.The decrease of the capsule diameter had a positive effect on each evaluation index.According to the sensitivity analysis,the order of importance of each parameter within their variation range was HTF inlet temperature,HTF flow rate,PCM capsule size and PCM initial temperature.
基金supported by the National Science Fund for Distinguished Young Scholars(22125804)the National Natural Science Foundation of China(21808110,22078155,and 21878149).
文摘Temperature-swing adsorption(TSA)is an effective technique for CO_(2) capture,but the temperature swing procedure is energy-intensive.Herein,we report a low-energy-consumption system by combining passive radiative cooling and solar heating for the uptake of CO_(2) on commercial activated carbons(CACs).During adsorption,the adsorbents are coated with a layer of hierarchically porous poly(vinylidene fluoride-co-hexafluoropropene)[P(VdF-HFP)HP],which cools the adsorbents to a low temperature under sunlight through radiative cooling.For desorption,CACs with broad absorption of the solar spectrum are exposed to light irradiation for heating.The heating and cooling processes are completely driven by solar energy.Adsorption tests under mimicked sunlight using the CACs show that the performance of this system is comparable to that of the traditional ones.Furthermore,under real sunlight irradiation,the adsorption capacity of the CACs can be well maintained after multiple cycles.The present work may inspire the development of new temperature swing procedures with little energy consumption.
基金supported by 2024 Central Guidance Local Science and Technology Development Fund Project"Study on the mechanism and evaluation method of thermal pollution in water bodies,as well as research on thermal carrying capacity".(Grant 246Z4506G)Key Research and Development Project in Hebei Province:"Key Technologies and Equipment Research and Demonstration of Multiple Energy Complementary(Electricity,Heat,Cold System)for Solar Energy,Geothermal Energy,Phase Change Energy"(Grant 236Z4310G)the Hebei Academy of Sciences Key Research and Development Program"Research on Heat Transfer Mechanisms and Efficient Applications of Intermediate and Deep Geothermal Energy"(22702)。
文摘Ground source heat pump systems demonstrate significant potential for northern rural heating applications;however,the effectiveness of these systems is often limited by challenging geological conditions.For instance,in certain regions,the installation of buried pipes for heat exchangers may be complicated,and these pipes may not always serve as efficient low-temperature heat sources for the heat pumps of the system.To address this issue,the current study explored the use of solar-energy-collecting equipment to supplement buried pipes.In this design,both solar energy and geothermal energy provide low-temperature heat to the heat pump.First,a simulation model of a solar‒ground source heat pump coupling system was established using TRNSYS.The accuracy of this model was validated through experiments and simulations on various system configurations,including varying numbers of buried pipes,different areas of solar collectors,and varying volumes of water tanks.The simulations examined the coupling characteristics of these components and their influence on system performance.The results revealed that the operating parameters of the system remained consistent across the following configurations:three buried pipes,burial depth of 20 m,collector area of 6 m^(2),and water tank volume of 0.5 m^(3);four buried pipes,burial depth of 20 m,collector area of 3 m^(2),and water tank volume of 0.5 m^(3);and five buried pipes with a burial depth of 20 m.Furthermore,the heat collection capacity of the solar collectors spanning an area of 3 m^(2)was found to be equivalent to that of one buried pipe.Moreover,the findings revealed that the solar‒ground source heat pump coupling system demonstrated a lower annual cumulative energy consumption compared to the ground source heat pump system,presenting a reduction of 5.31%compared to the energy consumption of the latter.
文摘This paper aims at presenting an application developed in Java for optimizing the design of centralized solar water heating systems with forced circulation, based on the f-chart method. The program uses data from the Brazilian Solar Atlas, performance data of flat plate collectors and thermal reservoirs from the standardized tests run within the Brazilian Labeling Program, and values of water consumption of appliances defined by the ABNT. The program finds the inclination of the collector that maximizes the annual solar fraction, or for the winter, and enables the use of arrays in series and parallel collectors. From the investment costs and O ＆ M （operations and maintenance） of solar heating systems, the program carries out economical analysis using classical parameters as net present value, discounted payback and internal rate of return. The program was validated through examples from the book of Duffle ＆ Beckman and also by comparison with the results from a project developed at UFRGS, having obtained good agreement.
基金supported by the Belt and Road Initiative by Chinese Academy of Sciencesthe National Natural Science Foundation of China(21673052,11404074)
文摘Catalytic converting CO2 into fuels with the help of solar energy is regarded as‘dream reaction’,as both energy crisis and environmental issue can be mitigated simultaneously.However,it is still suffering from low efficiency due to narrow solar-spectrum utilization and sluggish heterogeneous reaction kinetics.In this work,we demonstrate that catalytic reduction of CO2 can be achieved over Au nanoparticles(NPs)deposited rutile under full solar-spectrum irradiation,boosted by solar-heating effect.We found that UV and visible light can initiate the reaction,and the heat from IR light and local surface-plasmon resonance relaxation of Au NPs can boost the reaction kinetically.The apparent activation energy is determined experimentally and is used to explain the superior catalytic activity of Au/rutile to rutile in a kinetic way.We also find the photo-thermal synergy in the Au/rutile system.We envision that this work may facilitate understanding the kinetics of CO2 reduction and developing feasible catalytic systems with full solar spectrum utilization for practical artificial photosynthesis.
文摘It is introduced the current situation and development for solar heating technology including passive solar heating and solar heating combisystems in China in this paper. Combined with the engineering application projects, the author gave the technical and economic analysis of the passive solar and solar heating combisystems in China and summarized the developing obstacle and the spreading tactics for raising marketing of the solar heating in China.
基金support of the National Natural Science Foundation of China(Nos.52003248 and 82004001)the China Postdoctoral Science Foundation(Nos.2018M642780 and 2021T140613)+1 种基金the Open-ing Project of State Key Laboratory of Polymer Materials Engineer-ing(Sichuan University)(No.sklpme2019-4-31)the Key Research and Development and Promotion projects of Henan Province(No.202102210032)are gratefully acknowledged.
文摘Realizing all-day and all-weather energy-saving heating is crucial for mitigating the global energy and ecology crisis.Electric/solar heating are two promising heating approaches,yet materials with high elec-trical conductivity,high solar absorptivity,and low infrared emissivity at the same time are rare in na-ture,which are highly anticipated and of great significance for highly efficient electric/solar heating.In this work,we demonstrate that Ti_(3)C_(2)T_(x) MXene with low IR emissivity(14.5%)fills the gap in the absence of the above materials,exhibiting a remarkable electric/solar heating performance.The saturated heating temperature of Ti_(3)C_(2)T_(x) film reaches a record-high value of 201°C at a low driving voltage of 1.5 V,and reaches 84.3°C under practical solar irradiation(750 W/m^(2))with a high solar to the thermal conversion efficiency of 75.3%,which is far superior to other reported materials.Meanwhile,the low IR emissivity endows Ti_(3)C_(2)T_(x) with a remarkable passive radiative heating capability of 7.0°C,ensuring zero-energy heating without electric/solar energy supply.The intrinsic characteristic of high electrical conductivity,high solar absorptivity,and low IR emissivity makes Ti_(3)C_(2)T_(x) unique existence in nature,which is highly promising for all-day and all-weather energy-saving heating.
文摘Parabolic trough collectors （PTCs） are employed for a variety of applications including steam generation and hot water generation. This paper deals with the experimental results and an economic analysis of a new fibre reinforced plastic （FRP） based solar PTC with an embedded electronic controlled tracking system designed and developed for hot water generation in a restaurant in Madurai, India. The new collector performance has been tested according to ASHRAE Standard 93 （1986）. The performance of a new PTC hot water generation system with a well mixed hot water storage tank is investigated by a series of extensive tests over ten months period. The average maximum storage tank water temperature observed was 74.91℃, when no energy is withdrawn from the tank to the load during the collection period. The total cost of the new economic FRP based solar PTC for hot water generation with an embedded electronic controlled tracking system is Rs. 25000 （US$ 573） only. In the present work, life cycle savings （LCS） method is employed for a detailed economic analysis of the PTC system. A computer program is used as a tool for the economic analysis. The present worth of life cycle solar savings is evaluated for the new solar PTC hot water generation system that replaces an existing electric water heating system in the restaurant and attains a value of Rs. 23171.66 after 15 years, which is a significant saving. The LCS method and the MATLAB computer simulation program presented in this paper can be used to estimate the LCS of other renewable energy systems.
基金supported by the National Natural Science Foundation of China(Grant Nos.52078419 and 51678483)supported by the Doctoral Dissertation Innovation Fund of Xi’an University of Technology(310–252072116).
文摘Indoor thermal comfort and passive solar heating technologies have been extensively studied.However,few studies have explored the suitability of passive solar heating technologies based on differentiated thermal comfort demands.This work took the rural dwellings in Northwest China as the research object.First,the current indoor and outdoor thermal environment in winter and the mechanism of residents’differentiated demand for indoor thermal comfort were obtained through tests,questionnaires,and statistical analysis.Second,a comprehensive passive optimized design of existing buildings was conducted,and the validity of the optimized combination scheme was explored using DesignBuilder software.Finally,the suitability of passive solar heating technology for each region in Northwest China was analyzed based on residents’differentiated demand for indoor thermal comfort.The regions were then classified according to the suitability of the technology for these.The results showed that the indoor heating energy consumption was high and the indoor thermal environment was not ideal,yet the solar energy resources were abundant.Indoor comfort temperature indexes that match the functional rooms and usage periods were proposed.For the buildings with the optimized combination scheme,the average indoor temperature was increased significantly and the temperature fluctuation was decreased dramatically.Most regions in Northwest China were suitable for the development of passive solar heating technology.Based on the obtained suitability of the technology for the regions of Northwest China,these were classified into most suitable,more suitable,less suitable,and unsuitable regions.
文摘In this project, different combinations of solar energy and heat pump systems for preparation of DHW （domestic hot water） and space heating of buildings are analyzed through dynamic system simulations in TRNSYS （Transient System Simulation Program）. In such systems, solar thermal energy can be used, on one hand, directly to charge the buffer storage and, on the other hand, as heat source for the evaporator oftbe HP （heat pump）. In this work systems, in which solar heat is only used directly （parallel operation of solar and HP）, systems using the collectors also as a heat source for the HP are analyzed and compared to conventional air HP systems. With a combined parallel solar thermal HP system, the system performance compared to a conventional HP system can be significantly increased. Unglazed selectively coated collectors as source for the HP have the advantage that the collector can be used as an air heat exchanger. If solar radiation is available and the collector is used as source for the HP, higher temperatures at the evaporator of the HP can be achieved than with a conventional air HP system.
文摘A computer analysis of solar heating has been performed for Palestine. Results are presented for a prototype building using either fuel oil or gas under different heating loads in three climatic regions （Jordan valley, coastal, and hilly）. Cumulative cost flows are compared for the life-cycle present value technique. Optimum design magnitudes are determined for maximum life-cycle savings. The payback period for capital invested in a solar system, and total savings are found for the optimum conditions. Variations of system performance are estimated. The effects of collector slope, proportionate storage tank volume, heat-exchanger parameters, and the design load on system performance are studied. Finally the economics of solar heating in Palestine are discussed and recommendations are made for increased utilization of solar energy.
文摘Energy supply is one of the major challenges facing China. The rate at which demand is outstripping supply led the Standing Committee of the National People's Congress to pass the Renewable Energy Law of the PRC at its fourteenth session in February, 2005. The document points out that 'The law is legislated to promote exploitation and utilization of renewable energy, increase the supply of energy sources, improve the structure of energy sources, ensure the security of energy sources, protect the environment, and achieve the sustainable development of economy and society.' 'Renewable energy under the law is non-fossil energy, including wind, solar, water, biomass, geothermal, and ocean energies, etc.' 'The nation determines that the exploitation and utilization of renewable energy takes precedence in the development of energy sources, and propels the establishment and development of the renewable energy market.' 'The Standardization Administrative Department of the State Council should constitute and promulgate the national grid-connection standards for renew- able electricity, and other national technical standards that are related to renewable energy technology and products.'
文摘In this article,the effect of using water/zinc oxide nanofluid as a working fluid on the performance of solar collector is investigated experimentally.The volumetric concentration of nanoparticles is 0.4%,and the particle size is 40 nm,and the mass flow rate of the fluid varies from 1 to 3 kg/min.For this experiment,a device has been prepared with appropriate measuring instruments whose energy source is solar radiation.The solar energy absorbed by the flat plate collector is absorbed by the nanofluid of water/zinc oxide.The nanofluid is pumped to the consumer,a heat exchanger,where it heats the water.The temperature,radiation level,flow rate,and pressure in different parts of the device were measured.The pressure drop and the heat transferred are the most important results of this experimental work.The ASHRAE standard is used to calculate efficiency.The results showed that the use of water/zinc oxide nanofluid increases the collector performance compared to water.For 1 kg/min of mass flow rate,the nanofluids have a 16% increase in efficiency compared to water.From the results,it can be concluded that the choice of optimum mass flow rate in both water and nanofluid cases increases efficiency.
基金Thisworkwas supported by the Ministry of Education and Science of theRepublic of Kazakhstan BR10965172。
文摘In this paper,we studied theoretically and numerically heated losses of a flat solar collector to model the solar water heating system for the Kazakhstan climate condition.For different climatic zones with a growing cost for energy or lack of central heating systems,promising is to find ways to improve the energy efficiency of the solar system.The mathematical model(based on ordinary differential equation)simulated the solar system work process under different conditions.To bridge the modeling and real values results,we studied the important physical parameters such as loss coefficient,Nu,Ra,and Pr values.They impacted the efficiency of flat solar collectors and heat losses of the system.The developed mathematical models,the design and composition of the software and hardware complex,and automated control and monitoring systems allow solar hot water heating systems to increase the energy efficiency of life support systems and heat supply of buildings by reducing energy consumption for heat supply.The simulation result showed that during the daytime,the temperature of water in the collector is 70°C;the storage of heated water since heated water is cooled at night.We defined that a work period of the system can be extended with high efficiency(April-October)for Almaty region.
基金Funded by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China(No.2018YFB1501002)。
文摘Al_(2)O_(3)/SiC composite ceramics were prepared fromα-Al_(2)O_(3) and SiC by a pressureless sinter method in this study.The effect of SiC contents on the mechanic properties,phase compositions and microstructure is studied.Experimental results show that the vickers hardness,wear resistance and thermal conductivity of the samples increase with the increase in the SiC content,and the hardness of the sample reaches 16.22 GPa,and thermal conductivity of the sample reaches 25.41 W/(m.K)at room temperature when the SiC content is 20 wt%(B5)and the sintering temperature is at 1640℃.Higher hardness means higher scour resistance,and it indicates that the B5 material is expected to be used for the solar heat absorber of third generation solar thermal generation.The results indicate the mechanism of improving mechanical properties of Al_(2)O_(3)/SiC composite ceramics:SiC plays a role in grain refinement that the grain of SiC inhibits the grain growth of Al_(2)O_(3),while the addition of SiC changes the fracture mode from the intergranular to the intergranular-transgranular.
文摘China is the largest solar water heater producer and market in the world.Despite the fast growth and an installed capacity that accounts for the majority of the global gross,China's per capita solar hot water capacity is still very low,implying a huge margin of market potential;and the recognition of the industry in the global market is handicapped by the scattered scale of production and inconsistent product quality.To ensure continued growth of China's solar water heating(SWH) industry,Chinese Government has established a series of national SWH standards,three national testing centers,and a certification program to lay the foundation for the development of the Golden Sun product labeling system.China General Certification Center(CGC) developed the Golden Sun product certification and labeling system on a pass/fail basis evaluating with established criteria.The system was designed to help manufacturers acclimate to explicit consistent requirements and to identify and fix the deficiencies in the design and execution of the program itself.Timely revision and integration of the national standards are recommended to accommodate the test procedures and requirements to new technologies and the evolving SWH market.Strict implementation of the Golden Sun certification and labeling system are suggested to avail improving the quality control and forging internationally reputable brands of Chinese solar water heating products.
文摘At the limited roof north-south （N-S） width of a building, for the array with multirow collectors based on no shading at winter solstice noon and sloped at latitude, this paper studied the shading and the radiant energy striking on solar collector array. Based on Kunming solar radiation data, the annual and monthly solar radiant energy striking on multi-array collectors was analyzed and estimated, from no shading to partial shading by adding 1-3 collector row, at the slopes of 10°, 15°, 20°, 25°, 30°, 35° and 40°, respectively. The results showed that properly increasing the row number by reducing the slope of collectors was reasonable in order to get more annual radiant energy. Adding 1 row at 10° of slope was economical for Kunming, based on the 5-row array at 25°. And adding collector row by 20% at 10° of slope could increase the radiant energy striking on the array by 19%.
