The utilisation of waste in green sustainable technology can provide a clean environment and support energy demand.This work aims to design and analyse the performance of a developed indirect flat-plate Solar Air Heat...The utilisation of waste in green sustainable technology can provide a clean environment and support energy demand.This work aims to design and analyse the performance of a developed indirect flat-plate Solar Air Heater(SAH)integrated with an internal thermal storage unit using Waste Automotive Oil(WAO).The SAH was designed based on the circulation of confined air around the internal thermal storage unit due to the updraft effects of hot air.Two SAHs were tested to compare the performance of WAO and water,with the results being compared to previous work that utilised phase change material.Results showed that WAO responds faster in the early stage,while water has slightly higher daytime efficiency,with a maximum temperature of 60℃,while WAO reached a maximum temperature of 76℃.During the discharge cycle,WAO achieved an efficiency of 65.7%,while the water’s efficiency 73.2% within the same period.The highest outlet air temperatures recorded were 43℃ for WAO and 33.8℃ for water.These findings support that water is suitable for applications requiring rapid thermal charging,while WAO offers extended thermal stability.The study highlights the feasibility of using low-cost materials,such as WAO and water,to enhance the performance of solar energy systems,thereby making them more viable for industrial applications like drying and heating.展开更多
Phase change materials(PCMs)have attracted much attention in the field of solar thermal utilization recently,due to their outstanding thermal energy storage performance.However,PCMs usually release their stored latent...Phase change materials(PCMs)have attracted much attention in the field of solar thermal utilization recently,due to their outstanding thermal energy storage performance.However,PCMs usually release their stored latent heat spontaneously as the temperature below the phase transition temperature,rendering thermal energy storage and release uncontrollable,thus hindering their practical application in time and space.Herein,we developed erythritol/sodium carboxymethylcellulose/tetrasodium ethylenediaminetetraacetate(ERY/CMC/EDTA-4Na)composite PCMs with novel spatiotemporal thermal energy storage properties,defined as spatiotemporal PCMs(STPCMs),which exhibit the capacity of thermal energy long-term storage and controllable release.Our results show that the composite PCMs are unable to lose latent heat due to spontaneous crystallization during cooling,but can controllably release thermal energy through cold crystallization during reheating.The cold-crystallization temperature and enthalpy of composite PCMs can be adjusted by proportional addition of EDTA-4Na to the composite.When the mass fractions of CMC and EDTA-4Na are both 10%,the composite PCMs can exhibit the optical coldcrystallization temperature of 51.7℃ and enthalpy of 178.1 J/g.The supercooled composite PCMs without latent heat release can be maintained at room temperature(10-25℃)for up to more than two months,and subsequently the stored latent heat can be controllably released by means of thermal triggering or heterogeneous nucleation.Our findings provide novel insights into the design and construction of new PCMs with spatiotemporal performance of thermal energy long-term storage and controllable release,and consequently open a new door for the development of advanced solar thermal utilization techniques on the basis of STPCMs.展开更多
A building model with radiant cooling system was established and the cooling load, indoor temperature, surface temperature of the wails and other parameters in non-cooling and radiant cooling room were calculated by T...A building model with radiant cooling system was established and the cooling load, indoor temperature, surface temperature of the wails and other parameters in non-cooling and radiant cooling room were calculated by TRNSYS. The comparative analysis of the characteristics of attenuation and delay proves that the operation of radiant cooling system increases the degree of temperature attenuation of the room and reduces the inner surface temperature of the wall significantly, but has little effect on the attenuation coefficient and delay time of wall heat transfer. The simulation results also show that the inner surface temperature of the walls in the radiant cooling room is much lower than that in non-cooling room in the day with the maximum cooling load, which reduces the indoor operation temperature largely, and improves the thermal comfort. Finally, according to the analysis of indoor temperature of the rooms with different operation schedules of cooling system, it can be derived that the indoor mean temperature changes with the working time of radiant cooling system, and the operation schedule can be adjusted in practice according to the actual indoor temperature to achieve the integration of energy efficiency and thermal comfort.展开更多
The experiment is studied on thermal distribution in the thermal energy storage system with non-phase change materials (NPCM): NaNO3, KNO3 and NaCl in the range of 25°C - 250°C. The cylindrical storage syste...The experiment is studied on thermal distribution in the thermal energy storage system with non-phase change materials (NPCM): NaNO3, KNO3 and NaCl in the range of 25°C - 250°C. The cylindrical storage system was made of stainless steel with 25.6 cm-diameter and 26.8 cm-height that was contained of these NPCM. There was one pipe for heat transfer fluid (HTF) with 1.27 cm-diameter that manipulates in the storage tank and submerges to NPCM. The inner pipe was connected to the 2.27 cm-diameter outer HTF tube. The tube was further connected to the thermal pump, heater and load. The pump circulates the synthetic oil (Thermia oil) within the pipe for heat transferring purposes (charging and discharging). An electric heater is used as the heat source. The limitation of the charging oil temperature is maintained at 250°C with the flow rates in the range of 0.58 to 1.45 kg/s whereas the inlet temperature of the discharge oil is maintained at 25°C. Thermal performances of TES (thermal energy storage) such as charging and discharging times, radial thermal distribution, energy storage capacity and energy efficiency have been evaluated. The experimental results show that the radial thermal distribution of NaCl for TR inside, TR middle and TR outside was optimum of temperature down to NaNO3 and KNO3 respectively. Comparison of NPCMs with oil, flow rates for NaCl were charging and discharging heat transfer than KNO3 and NaNO3. The thermal stored NaCl ranged from 5712 - 5912 J;KNO3 ranged from 7350 - 7939 J and NaNO3 ranged from 6623 - 6930 J respectively. The thermal energy stored for experimental results got with along the KNO3, NaNO3 and NaCl respectively. The thermal energy efficiency of NaCl, KNO3 and NaNO3 was in the range 66% - 70%.展开更多
Mullite and corundum co-bonded SiC-based composite ceramics(SiC-mullite-Al2O3)were prepared by using SiC,calcined bauxite and kaolin via pressureless carbon-buried sintering.The low-cost SiC-based composite ceramics d...Mullite and corundum co-bonded SiC-based composite ceramics(SiC-mullite-Al2O3)were prepared by using SiC,calcined bauxite and kaolin via pressureless carbon-buried sintering.The low-cost SiC-based composite ceramics designed in this study are expected to be used as thermal storage materials in solar thermal power generation based on the high density and excellent thermal shock resistance.The influences of calcined bauxite addition and sintering temperature on the microstructures,phase compositions,and physical properties of the samples were investigated.Results demonstrated that the introduction of calcined bauxite containing two bonding phases greatly reduced the lowest sintering temperature to 1400℃.The SiC-mullite Al2O3 composite with 40 wt%calcined bauxite sintered at 1500℃exhibited optimum performance.The density and bending strength were 2.27 g·cm^-3 and 77.05 MPa.The bending strength increased by 24.58%and no cracks were observed after 30 thermal shock cycles,while general clay would reduce the thermal shock resistance of SiC.The SiC-mullite-Al2O3 composites with satisfied performance are expected to be used as thermal storage materials in solar thermal power generation systems.展开更多
A thermal heat storage system with an energy content of 40 kWh and a temperature of 58°C will be presented. This storage system is suitable for supporting the use of renewable energies in buildings and for absorb...A thermal heat storage system with an energy content of 40 kWh and a temperature of 58°C will be presented. This storage system is suitable for supporting the use of renewable energies in buildings and for absorbing solar heat, heat from co-generation and heat pumps or electric heat from excess wind and solar power. The storage system is equipped with a plate heat exchanger that is so powerful that even with small temperature differences between the flow temperature and the storage temperature a high load dynamic is achieved. The storage system has a performance of 2.8 kW at 4 K and 10.6 kW at a temperature difference of 10 K. Thus, large performance variations in solar thermal systems or CHP plants can be buffered very well. Further a storage charge function Q(T, t) will be presented to characterize the performance of the storage.展开更多
The effect of LaNi and Ti on thermal storage properties of MgH_(2)was investigated.The thermal storage performances of Mg are significantly improved by adding LaNi and Ti.The pressure-composition-temperature(PCT)curve...The effect of LaNi and Ti on thermal storage properties of MgH_(2)was investigated.The thermal storage performances of Mg are significantly improved by adding LaNi and Ti.The pressure-composition-temperature(PCT)curves indicate that the formation enthalpy for Mg-15 wt%Ti-5 wt%LaNi sample is 73.00 kJ·mol^(-1),which approaches to the theoretical values of pure MgH_(2).The isothermal measurement indicates that,for the Mg-15wt%Ti-5 wt%LaNi,the first absorption reaction fraction within 2 min is 93.77%,increasing by 0.32%,0.24%and0.08%compared with those for Mg,Mg-5 wt%LaNi and Mg-15 wt%Ti,respectively.The first desorption reaction fraction within 2 min is 73.18%,increasing by 55.91%,9.79%and 8.12%compared with those for Mg,Mg-5wt%LaNi and Mg-15 wt%Ti,respectively.Moreover,Mg-15 wt%Ti-5 wt%LaNi has the best cyclic stability in all the samples.The thermal storage performances of Mg by adding both LaNi and Ti are improved mainly ascribed to synergistic effect of in situ formed La_(4)H_(12.19),Mg_(2)NiH_(4),H_(0.3)Mg_(2)Ni and TiH_(2)particles during cyclic process.The above analysis demonstrates that Mg-15 wt%Ti-5wt%LaNi is suitable for using as a heat storage material.展开更多
Shell and tube heat storage technology is considered an effective means to address temporal and spatial mismatches in renewable energy utilization.However,its application is limited by poor heat transfer performance.I...Shell and tube heat storage technology is considered an effective means to address temporal and spatial mismatches in renewable energy utilization.However,its application is limited by poor heat transfer performance.In this study,an elliptical tube was introduced in the shell and tube heat storage unit,and the thermal storage performance was investigated and compared with circular tube by numerical simulations.The superiority and reliability of elliptical tube thermal storage units were validated,and the effects of heat transfer fluid(HTF)flow velocity,heating temperature,and the angle between the major axis and HTF flow direction on heat transfer capacity were elucidated.It was demonstrated that the introduction of elliptical tube can reduce the melting time of molten salt-based phase change material(PCM)by 63.11%and decrease pressure drop by 95.19%compared to circular tube under the equal cross-sectional area.In addition,it is found that the increase of the HTF velocity is helpful to promote the heat transfer,but also results in higher pressure drops and energy losses.As the heating temperature increases from 425 K to 445 K,the melting time of the PCM can be reduced by 63.2%.The angle between the major axis of the elliptical tube and the HTF flow direction was also identified as a critical factor,with angles between 30°and 60°providing an optimal balance between phase change time and pressure drop,making it an ideal choice for the improvement of heat exchange efficiency and the reduction of energy consumption.展开更多
Water is essential to life. The origin and continuation of mankind is based on water. The supply of drinking water is an important problem for the developing countries. Among the non-conventional methods to desalinate...Water is essential to life. The origin and continuation of mankind is based on water. The supply of drinking water is an important problem for the developing countries. Among the non-conventional methods to desalinate brackish water or seawater, is solar distillation. The solar still is the most economical way to accomplish this objective. Tamilnadu lies in the high solar radiation band and the vast solar potential can be utilized to convert saline water to potable water. The sun’s energy heats water to the point of evaporation. When water evaporates, water vapour rises leaving the impurities like salts, heavy metals and condensate on the underside of the glass cover. Sunlight has the advantage of zero fuel cost but it requires more space and generally more equipment. Solar distillation has low yield, but safe and pure supplies of water in remote areas. In this context, the design modification of a single basin solar still has been discussed to improve the solar still performance through increasing the production rate of distilled water. The attempts are also made to increase the productivity of water by using different absorbing materials, depths of water, heat storage medium and also by providing low pressure inside the still basin. They greatly improve the rate of evaporation and hence the rate of condensation on the cooler surface. The theoretical results agree well with the experimental ones.展开更多
The energy storage is an effective solution for the current imbalance between energy supply and demand.In particular,the cascaded storage method can enhance the heat exchange temperature difference and heat stor-age e...The energy storage is an effective solution for the current imbalance between energy supply and demand.In particular,the cascaded storage method can enhance the heat exchange temperature difference and heat stor-age efficiency.Previous research mainly focused on the combination of different phase change materials,while there was rare research on efficient cascaded conversion pathways for electrothermal direct conversion cou-pled thermal storage devices.This study investigated the influence of sensible and latent heat storage materials on the thermal performance,and identified the optimal volume ratios and materials types.When the volume share of Mg-Al:PW-EG=1:1,the heat storage performance was the optimal with a quantity/efficiency of heat stored as 7328.7 kJ/97.3%,leading to an increase of 458.5 kJ/6.6%than the sensible heat storage condition(Mg-Al:PW-EG=1:0)and 630.18 kJ/8.5%than the latent heat storage condition(Mg-Al:PW-EG=0:1).When the melting point and latent heat of phase change materials increased from 68.9∼79.1°C and 224.8 kJ/kg to 118.0°C and 344.9 kJ/kg respectively,the heat storage temperature rose by 162.7°C,quantity of heat stored rose by 7535.5 kJ.While materials with large subcooling were not recommended for short-term heat storage,as approximately 25.6%(3309.3 kJ)of stored heat and 22.4%(2505.2 kJ)of exergy were wasted when the subcooling degree was 70°C.The findings provided solutions to support the synergistic enhancement of heat storage/release performance of the composite energy storage heat sink.展开更多
As the total amount and share of new energy installed capacity continue to rise,the demand for flexible regulation capability of the power system is becoming more and more prominent.The current conventional molten sal...As the total amount and share of new energy installed capacity continue to rise,the demand for flexible regulation capability of the power system is becoming more and more prominent.The current conventional molten salt energy storage system has insufficient peaking capacity.A solar-molten salt energy storage system based on multiple heat sources is constructed in this study.The heat generated from the solar field and the steams are used for the peaking process to further enhance the peaking capacity and flexibility.The installation multi-stage steam extraction and the introduction of an external heat source significantly improve the system performance.The simulation models based on EBSILON software are developed and the effects of key parameters on performance are discussed.The feasibility of the proposed system is further evaluated in terms of exergy and economy.The results demonstrate that the proposed SF-TES-CFPP(solar field,thermal energy storage system,coal-fired power plant)system exhibits the enhancement of peaking capability and flexible operation.In comparison with the conventional TES-CFPP,the integration of solar energy into the peaking process has enabled the SF-TES-CFPP system to enhance its peaking capacity by 20.60 MW while concurrently reducing the coal consumption rate by 10.26 g/kWh.The round-trip efficiency of the whole process of the system can be up to 85.43%through the reasonable heat distribution.In addition,the exergy loss of the principal components can be diminished and the exergy efficiency of the system can be augmented by selecting an appropriate main steam extraction mass and split ratio.The economic analysis demonstrates the dynamic payback period is 9.90 years with the net present value(NPV)across the entire life cycle reaching 1.06902×10^(9)USD.展开更多
In this paper,the thermal and mechanical dynamic performances of molten salt packed-bed thermal energy storage(TES)system are investigated by coupling Finite Volume Method(FVM)and Finite Element Method(FEM).Firstly,an...In this paper,the thermal and mechanical dynamic performances of molten salt packed-bed thermal energy storage(TES)system are investigated by coupling Finite Volume Method(FVM)and Finite Element Method(FEM).Firstly,an integration model coupling FVM and FEM in packed-bed tank is developed.Particularly,the pore water static pressure caused by the liquid level of molten salt is applied in the coupled method.Based on this model,the dynamic characteristics of thermal and stress distributions are simulated.Finally,the effects of porosity,inlet temperature and velocity on the thermal and stress performances are analyzed.The results indicate that the temperature and stress of the wall increase during the discharging process,and the peak stress occurs at the tank bottom connecting with the ground foundation.The method of increasing porosity is helpful to improve the discharging power,but the plastic failure on the wall would probably occur due to the higher stress level.Increasing inlet temperature has negative influence on the thermal and safety performances,because lower discharging power and higher stress would be produced adversely.Although the lower stress can be achieved when the higher inlet velocity is adopted,the effective discharge time would be decreased significantly.展开更多
文摘The utilisation of waste in green sustainable technology can provide a clean environment and support energy demand.This work aims to design and analyse the performance of a developed indirect flat-plate Solar Air Heater(SAH)integrated with an internal thermal storage unit using Waste Automotive Oil(WAO).The SAH was designed based on the circulation of confined air around the internal thermal storage unit due to the updraft effects of hot air.Two SAHs were tested to compare the performance of WAO and water,with the results being compared to previous work that utilised phase change material.Results showed that WAO responds faster in the early stage,while water has slightly higher daytime efficiency,with a maximum temperature of 60℃,while WAO reached a maximum temperature of 76℃.During the discharge cycle,WAO achieved an efficiency of 65.7%,while the water’s efficiency 73.2% within the same period.The highest outlet air temperatures recorded were 43℃ for WAO and 33.8℃ for water.These findings support that water is suitable for applications requiring rapid thermal charging,while WAO offers extended thermal stability.The study highlights the feasibility of using low-cost materials,such as WAO and water,to enhance the performance of solar energy systems,thereby making them more viable for industrial applications like drying and heating.
基金the financial support from the Joint Fund of the Yulin University and the Dalian National Laboratory for Clean Energy(YLU-DNL Fund 2021007)the National Nature Science Foundation of China(21903082 and 22273100)+2 种基金the Dalian Institute of Chemical Physics(DICP I202036,and I202218)the DNL Cooperation Fund,CAS(DNL202012)Liaoning Provincial Natural Science Foundation of China under grant 2022-MS-020。
文摘Phase change materials(PCMs)have attracted much attention in the field of solar thermal utilization recently,due to their outstanding thermal energy storage performance.However,PCMs usually release their stored latent heat spontaneously as the temperature below the phase transition temperature,rendering thermal energy storage and release uncontrollable,thus hindering their practical application in time and space.Herein,we developed erythritol/sodium carboxymethylcellulose/tetrasodium ethylenediaminetetraacetate(ERY/CMC/EDTA-4Na)composite PCMs with novel spatiotemporal thermal energy storage properties,defined as spatiotemporal PCMs(STPCMs),which exhibit the capacity of thermal energy long-term storage and controllable release.Our results show that the composite PCMs are unable to lose latent heat due to spontaneous crystallization during cooling,but can controllably release thermal energy through cold crystallization during reheating.The cold-crystallization temperature and enthalpy of composite PCMs can be adjusted by proportional addition of EDTA-4Na to the composite.When the mass fractions of CMC and EDTA-4Na are both 10%,the composite PCMs can exhibit the optical coldcrystallization temperature of 51.7℃ and enthalpy of 178.1 J/g.The supercooled composite PCMs without latent heat release can be maintained at room temperature(10-25℃)for up to more than two months,and subsequently the stored latent heat can be controllably released by means of thermal triggering or heterogeneous nucleation.Our findings provide novel insights into the design and construction of new PCMs with spatiotemporal performance of thermal energy long-term storage and controllable release,and consequently open a new door for the development of advanced solar thermal utilization techniques on the basis of STPCMs.
基金Project(2010DFA72740) supported by the International Science & Technology Cooperation Program of China
文摘A building model with radiant cooling system was established and the cooling load, indoor temperature, surface temperature of the wails and other parameters in non-cooling and radiant cooling room were calculated by TRNSYS. The comparative analysis of the characteristics of attenuation and delay proves that the operation of radiant cooling system increases the degree of temperature attenuation of the room and reduces the inner surface temperature of the wall significantly, but has little effect on the attenuation coefficient and delay time of wall heat transfer. The simulation results also show that the inner surface temperature of the walls in the radiant cooling room is much lower than that in non-cooling room in the day with the maximum cooling load, which reduces the indoor operation temperature largely, and improves the thermal comfort. Finally, according to the analysis of indoor temperature of the rooms with different operation schedules of cooling system, it can be derived that the indoor mean temperature changes with the working time of radiant cooling system, and the operation schedule can be adjusted in practice according to the actual indoor temperature to achieve the integration of energy efficiency and thermal comfort.
文摘The experiment is studied on thermal distribution in the thermal energy storage system with non-phase change materials (NPCM): NaNO3, KNO3 and NaCl in the range of 25°C - 250°C. The cylindrical storage system was made of stainless steel with 25.6 cm-diameter and 26.8 cm-height that was contained of these NPCM. There was one pipe for heat transfer fluid (HTF) with 1.27 cm-diameter that manipulates in the storage tank and submerges to NPCM. The inner pipe was connected to the 2.27 cm-diameter outer HTF tube. The tube was further connected to the thermal pump, heater and load. The pump circulates the synthetic oil (Thermia oil) within the pipe for heat transferring purposes (charging and discharging). An electric heater is used as the heat source. The limitation of the charging oil temperature is maintained at 250°C with the flow rates in the range of 0.58 to 1.45 kg/s whereas the inlet temperature of the discharge oil is maintained at 25°C. Thermal performances of TES (thermal energy storage) such as charging and discharging times, radial thermal distribution, energy storage capacity and energy efficiency have been evaluated. The experimental results show that the radial thermal distribution of NaCl for TR inside, TR middle and TR outside was optimum of temperature down to NaNO3 and KNO3 respectively. Comparison of NPCMs with oil, flow rates for NaCl were charging and discharging heat transfer than KNO3 and NaNO3. The thermal stored NaCl ranged from 5712 - 5912 J;KNO3 ranged from 7350 - 7939 J and NaNO3 ranged from 6623 - 6930 J respectively. The thermal energy stored for experimental results got with along the KNO3, NaNO3 and NaCl respectively. The thermal energy efficiency of NaCl, KNO3 and NaNO3 was in the range 66% - 70%.
基金Funded by the National Key Research and Development Program of Science and Technology of China(No.2018YFB1501002).
文摘Mullite and corundum co-bonded SiC-based composite ceramics(SiC-mullite-Al2O3)were prepared by using SiC,calcined bauxite and kaolin via pressureless carbon-buried sintering.The low-cost SiC-based composite ceramics designed in this study are expected to be used as thermal storage materials in solar thermal power generation based on the high density and excellent thermal shock resistance.The influences of calcined bauxite addition and sintering temperature on the microstructures,phase compositions,and physical properties of the samples were investigated.Results demonstrated that the introduction of calcined bauxite containing two bonding phases greatly reduced the lowest sintering temperature to 1400℃.The SiC-mullite Al2O3 composite with 40 wt%calcined bauxite sintered at 1500℃exhibited optimum performance.The density and bending strength were 2.27 g·cm^-3 and 77.05 MPa.The bending strength increased by 24.58%and no cracks were observed after 30 thermal shock cycles,while general clay would reduce the thermal shock resistance of SiC.The SiC-mullite-Al2O3 composites with satisfied performance are expected to be used as thermal storage materials in solar thermal power generation systems.
文摘A thermal heat storage system with an energy content of 40 kWh and a temperature of 58°C will be presented. This storage system is suitable for supporting the use of renewable energies in buildings and for absorbing solar heat, heat from co-generation and heat pumps or electric heat from excess wind and solar power. The storage system is equipped with a plate heat exchanger that is so powerful that even with small temperature differences between the flow temperature and the storage temperature a high load dynamic is achieved. The storage system has a performance of 2.8 kW at 4 K and 10.6 kW at a temperature difference of 10 K. Thus, large performance variations in solar thermal systems or CHP plants can be buffered very well. Further a storage charge function Q(T, t) will be presented to characterize the performance of the storage.
基金financially supported by the Beijing Municipal Commission of Science and Technology of China(D141100002014001)。
文摘The effect of LaNi and Ti on thermal storage properties of MgH_(2)was investigated.The thermal storage performances of Mg are significantly improved by adding LaNi and Ti.The pressure-composition-temperature(PCT)curves indicate that the formation enthalpy for Mg-15 wt%Ti-5 wt%LaNi sample is 73.00 kJ·mol^(-1),which approaches to the theoretical values of pure MgH_(2).The isothermal measurement indicates that,for the Mg-15wt%Ti-5 wt%LaNi,the first absorption reaction fraction within 2 min is 93.77%,increasing by 0.32%,0.24%and0.08%compared with those for Mg,Mg-5 wt%LaNi and Mg-15 wt%Ti,respectively.The first desorption reaction fraction within 2 min is 73.18%,increasing by 55.91%,9.79%and 8.12%compared with those for Mg,Mg-5wt%LaNi and Mg-15 wt%Ti,respectively.Moreover,Mg-15 wt%Ti-5 wt%LaNi has the best cyclic stability in all the samples.The thermal storage performances of Mg by adding both LaNi and Ti are improved mainly ascribed to synergistic effect of in situ formed La_(4)H_(12.19),Mg_(2)NiH_(4),H_(0.3)Mg_(2)Ni and TiH_(2)particles during cyclic process.The above analysis demonstrates that Mg-15 wt%Ti-5wt%LaNi is suitable for using as a heat storage material.
基金supported by National Natural Science Foundation of China (No.52306118)Key Science Research Project of the University in Henan (241111320900).
文摘Shell and tube heat storage technology is considered an effective means to address temporal and spatial mismatches in renewable energy utilization.However,its application is limited by poor heat transfer performance.In this study,an elliptical tube was introduced in the shell and tube heat storage unit,and the thermal storage performance was investigated and compared with circular tube by numerical simulations.The superiority and reliability of elliptical tube thermal storage units were validated,and the effects of heat transfer fluid(HTF)flow velocity,heating temperature,and the angle between the major axis and HTF flow direction on heat transfer capacity were elucidated.It was demonstrated that the introduction of elliptical tube can reduce the melting time of molten salt-based phase change material(PCM)by 63.11%and decrease pressure drop by 95.19%compared to circular tube under the equal cross-sectional area.In addition,it is found that the increase of the HTF velocity is helpful to promote the heat transfer,but also results in higher pressure drops and energy losses.As the heating temperature increases from 425 K to 445 K,the melting time of the PCM can be reduced by 63.2%.The angle between the major axis of the elliptical tube and the HTF flow direction was also identified as a critical factor,with angles between 30°and 60°providing an optimal balance between phase change time and pressure drop,making it an ideal choice for the improvement of heat exchange efficiency and the reduction of energy consumption.
文摘Water is essential to life. The origin and continuation of mankind is based on water. The supply of drinking water is an important problem for the developing countries. Among the non-conventional methods to desalinate brackish water or seawater, is solar distillation. The solar still is the most economical way to accomplish this objective. Tamilnadu lies in the high solar radiation band and the vast solar potential can be utilized to convert saline water to potable water. The sun’s energy heats water to the point of evaporation. When water evaporates, water vapour rises leaving the impurities like salts, heavy metals and condensate on the underside of the glass cover. Sunlight has the advantage of zero fuel cost but it requires more space and generally more equipment. Solar distillation has low yield, but safe and pure supplies of water in remote areas. In this context, the design modification of a single basin solar still has been discussed to improve the solar still performance through increasing the production rate of distilled water. The attempts are also made to increase the productivity of water by using different absorbing materials, depths of water, heat storage medium and also by providing low pressure inside the still basin. They greatly improve the rate of evaporation and hence the rate of condensation on the cooler surface. The theoretical results agree well with the experimental ones.
基金supported by the Hebei Provincial Postdoctoral Sci-ence Foundation(Project No.B2022005004)the Science and Tech-nology Nova Plan of Hebei University of Technology(Project No.JBKYXX2207)+1 种基金the National Natural Science Foundation of China(Project No.51978231)the Hebei Province Funding Project for Returned Scholars,China(Project No.:C20190507).
文摘The energy storage is an effective solution for the current imbalance between energy supply and demand.In particular,the cascaded storage method can enhance the heat exchange temperature difference and heat stor-age efficiency.Previous research mainly focused on the combination of different phase change materials,while there was rare research on efficient cascaded conversion pathways for electrothermal direct conversion cou-pled thermal storage devices.This study investigated the influence of sensible and latent heat storage materials on the thermal performance,and identified the optimal volume ratios and materials types.When the volume share of Mg-Al:PW-EG=1:1,the heat storage performance was the optimal with a quantity/efficiency of heat stored as 7328.7 kJ/97.3%,leading to an increase of 458.5 kJ/6.6%than the sensible heat storage condition(Mg-Al:PW-EG=1:0)and 630.18 kJ/8.5%than the latent heat storage condition(Mg-Al:PW-EG=0:1).When the melting point and latent heat of phase change materials increased from 68.9∼79.1°C and 224.8 kJ/kg to 118.0°C and 344.9 kJ/kg respectively,the heat storage temperature rose by 162.7°C,quantity of heat stored rose by 7535.5 kJ.While materials with large subcooling were not recommended for short-term heat storage,as approximately 25.6%(3309.3 kJ)of stored heat and 22.4%(2505.2 kJ)of exergy were wasted when the subcooling degree was 70°C.The findings provided solutions to support the synergistic enhancement of heat storage/release performance of the composite energy storage heat sink.
基金supported by the National Key R&D Program(No.2022YFB4202404)。
文摘As the total amount and share of new energy installed capacity continue to rise,the demand for flexible regulation capability of the power system is becoming more and more prominent.The current conventional molten salt energy storage system has insufficient peaking capacity.A solar-molten salt energy storage system based on multiple heat sources is constructed in this study.The heat generated from the solar field and the steams are used for the peaking process to further enhance the peaking capacity and flexibility.The installation multi-stage steam extraction and the introduction of an external heat source significantly improve the system performance.The simulation models based on EBSILON software are developed and the effects of key parameters on performance are discussed.The feasibility of the proposed system is further evaluated in terms of exergy and economy.The results demonstrate that the proposed SF-TES-CFPP(solar field,thermal energy storage system,coal-fired power plant)system exhibits the enhancement of peaking capability and flexible operation.In comparison with the conventional TES-CFPP,the integration of solar energy into the peaking process has enabled the SF-TES-CFPP system to enhance its peaking capacity by 20.60 MW while concurrently reducing the coal consumption rate by 10.26 g/kWh.The round-trip efficiency of the whole process of the system can be up to 85.43%through the reasonable heat distribution.In addition,the exergy loss of the principal components can be diminished and the exergy efficiency of the system can be augmented by selecting an appropriate main steam extraction mass and split ratio.The economic analysis demonstrates the dynamic payback period is 9.90 years with the net present value(NPV)across the entire life cycle reaching 1.06902×10^(9)USD.
基金supported by the National Natural Science Foundation of China(No.51906172)the Applied Basic Research Programs of Shanxi Province(Grant No.201901D111058)。
文摘In this paper,the thermal and mechanical dynamic performances of molten salt packed-bed thermal energy storage(TES)system are investigated by coupling Finite Volume Method(FVM)and Finite Element Method(FEM).Firstly,an integration model coupling FVM and FEM in packed-bed tank is developed.Particularly,the pore water static pressure caused by the liquid level of molten salt is applied in the coupled method.Based on this model,the dynamic characteristics of thermal and stress distributions are simulated.Finally,the effects of porosity,inlet temperature and velocity on the thermal and stress performances are analyzed.The results indicate that the temperature and stress of the wall increase during the discharging process,and the peak stress occurs at the tank bottom connecting with the ground foundation.The method of increasing porosity is helpful to improve the discharging power,but the plastic failure on the wall would probably occur due to the higher stress level.Increasing inlet temperature has negative influence on the thermal and safety performances,because lower discharging power and higher stress would be produced adversely.Although the lower stress can be achieved when the higher inlet velocity is adopted,the effective discharge time would be decreased significantly.
