Low-energy-consumption temperature swing system for CO_(2) capture by combining passive radiative cooling and solar heating

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.

Parametric analysis of a packed bed thermal storage device with phase change material capsules in a solar heating system application

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.

Numerical Analysis of Phase Change and Container Materials for Thermal Energy Storage in the Storage Tank of Solar Water Heating System

This study evaluates the effectiveness of phase change materials(PCMs) inside a storage tank of warm water for solar water heating(SWH) system through the theoretical simulation based on the experimental model of S.Canbazoglu et al.The model is explained by five fundamental equations for the calculation of various parameters like the effectiveness of PCMs,the mass of hot water,total heat content,and duration of charging.This study simulated eleven PCMs to analyze their effectiveness like Sodium hydrogen phosphate dodecahydrate(SHPD),OM 37,N-Eicosane(NE),Lauric acid(LA),Paraffin wax(PW),OM 48,Paraffin wax C_(20-33)(PW-C20-33),Sodium acetate trihydrate(SAT),Palmitic acid(PA),Myristic acid(MA),and Stearic acid(SA).Among all PCMs,the SHPD has found the highest value of effectiveness factor of 3.27.So,it is the most recommended PCM for the storage tank of the SWH system.The study also includes the melt fraction analysis of all enumerated PCMs corresponding to container materials of stainless steel,glass,aluminum mixed,tin,aluminum,and copper.This melt fraction analysis is performed by making a coding program in the FORTRAN programming language.Through the analysis,copper container material is found to have high melting rate for all PCMs so it is superior to other container materials.

Numerical Study on the Suitability of Passive Solar Heating Technology Based on Differentiated Thermal Comfort Demand

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.

Exergo-Environmental Study of a Recent Organic Solar Hybrid Heat Pump

A hybrid heat pump(compression/absorption)with an integrated thermal photovoltaic unit is studied.The considered working fluids are organic mixtures:R245fa/DMAC and R236fa/DMAC,chosen for their low Global Warming Potential.The main objective is the optimization of energy efficiency in order to minimize the environmental impact through the implementation of a sustainable strategy.It is shown that Exergy Analysis itself is a valuable tool in energy integration.Within the imposed framework of minimizing total annual costs,entropy analysis can be instrumental in determining the optimal plant concept,optimizing energy conversion and use,and improving profitability.The present results are discussed under the optimistic hope that they may help to define new energy and environmental policies.

Overview of China's National Standards for Solar Water Heating

Introduction 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.……

Impact of Numerous Beds Operating Conditions for Enhancing the Performance of a Solar Heat-Supported Adsorption Chiller

Thermal adsorption cooling systems have gained significant attention due to their potential for energy savings and eco-environmental impact. An analytic investigation of the heat transfer inside an adsorption chiller with various bed silica gel-water pairs is presented. A comprehensive model has been designed to accurately predict the correlation between the overall performance of the proposed chiller system and the functional and structural condition of the building. This model takes into account various factors such as temperature, humidity, and air quality to provide a detailed analysis of the system’s efficiency. At least 20 collectors consisting of a 34.4 m area (each) with a full-cycle time of 480 seconds are essential to improper run conditions. It is necessary to adjust the optimum cycle time for optimal performance. During the investigation, the base condition shows that the cooling capacity is 14 kw, 0.6 COPcycle, and 0.35 COPsolar at noon. Also, conduct a thorough investigation into the chiller’s performance under varying cooling water supply temperatures and various chilled water flow rates.

Thermal Loss Analysis of a Flat Plate Solar Collector Using Numerical Simulation

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.

Potential application of a novel building-integrated solar facade water heating system in a subtropical climate:A case study for school canteen

The design and potential application analysis of the novel solar-absorbing integrated facade module and its corresponding building-integrated solar facade water heating system are presented in this study.Compared with the conventional building envelope,the main novities of the proposed facade module lie in its contributions towards the supplied water preheating to loads and the internal heat gain reduction.Besides,the proposed building-integrated solar facade water heating system broadens the combination modes of the solar thermal system and the building envelope.A dynamic model is introduced first for system design and performance prediction.To evaluate the energy-saving potential and feasibility of the implementation of the proposed facade module,this paper carried out a suitable case study by replacing the conventional facade module in the ongoing retrofitting project of a kitchen,part of the canteen of a graduate school.The detailed thermal performances of three system design options are compared in the typical winter and summer weeks and throughout the year,and then,with the preferred system design,the economic,energy,and environmental effects of the proposed system are evaluated.It was found that the system with a high flow rate of the circulating water is suggested.The annual electricity saved reaches 4175.3 kWh with yearly average thermal efficiency at 46.9%,and its corresponding cost payback time,energy payback time,and greenhouse gas payback time are 3.8,1.7,1.7 years,respectively.This study confirms the feasibility and long-term benefits of the proposed building-integrated solar facade water heating system in buildings.

A new artificial photosynthetic system coupling photovoltaic electrocatalysis with solar heating catalysis

In this work,we present a novel artificial photosynthetic paradigm with square meter(m^(2))level scalable production by integrating photovoltaic electrolytic water splitting device and solar heating CO_(2)hydrogenation device,successfully achieving the synergy of 1 sun driven 19.4%solar to chemical energy efficiency(STC)for CO production(2.7 times higher than that of large-sized artificial photosynthetic systems)with a low cost(equivalent to 1/7 of reported artificial photosynthetic systems).Furthermore,the outdoor artificial photosynthetic demonstration with 1.268 m^(2)of scale exhibits the CO generation amount of 258.4 L per day,the STC of~15.5%for CO production in winter,which could recover the cost within 833 sunny days of operation by selling CO.

Operation strategy and energy-saving of the solar lighting/heating system through spectral splitting

The performance of a solar lighting and heating system(SLHS)based on the spectral splitting effect of nanofluids is presented in this paper.SLHS through nanofluids would split the sunlight spectrum into different wavelength,and then introduce the visible light into the offices for lighting and absorb infrared energy to generate hot water.The Energy Plus software was used to analyze the energy consumption of typical office building located in the city of Harbin in China coupled with SLHS.Based on the simulation results two lighting zones were identified in the offices and the optimal lighting control strategy was developed for a full year.The performance models of SLHS with different light-receiving areas of 10 m^(2)and 40 m^(2)were simulated and validated using the existing experimental data.The overall energy-saving of the offices over a full year were analyzed using the validated model.Results demonstrated that for SLHS with the area of 40 m^(2),the rate of the energy saving in the offices due to lighting and hot water systems were 58.9%,and 19.3%,respectively.The system also had the additional benefit of reducing the cooling load of the air conditioning system during summer period together with improving the quality of the indoor environment resulting in better health and productivity of the occupants.

Mechanical Properties and Microstructure of Al_(2)O_(3)/SiC Composite Ceramics for Solar Heat Absorber

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.

CFD Simulations of Wind Effect on Net Solar Heat Gain of South Walls with Internal Insulation

Computational fluid dynamics( CFD) techniques are used to investigate effects of both wind direction and wind speed on net solar heat gain of south wall with internal insulation in winter.Results show that wind effect has a significant influence on the net solar heat gain,where the impact of wind direction is stronger than that of wind speed. For regions in lower reaches of the Yangtze River,difference of their average net solar heat gains( NSHGS) is about 20% due to various wind speeds and wind directions.Buildings in districts with a dominant wind direction of north achieve the highest solar energy utilization.

Arrangement of Multirow Solar Collector Array on Limited Roof Width

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%.

Analysis of Variation Characters and Prediction Model of Soil Temperature in Solar Greenhouse

[Objective] The aim was to study the soil temperature changes and its forecast model in greenhouse by solar heat. [Method] Annual and daily variation characters of soil temperature were analyzed in this paper by using the observation data of air temperature out of solar greenhouse and different layers soil temperature in it. The soil temperature (daily maximum, daily minimum and daily mean) forecasting models were also studied. Simulation and test were conducted to the forecast model of soil temperature in the greenhouse. [Result] The annual changes and daily changes of soil temperature of each layer in the greenhouse were in single peak curve. The lower layer temperature changes were smaller than the upper layer. The soil temperature of each layer within the greenhouse was closely related to the relevance of same type temperature outside the greenhouse of the day. Taking the average daily temperature, daily maximum temperature and daily lowest temperature of the day and the day before as forecast factors, soil temperature forecast model of different layer of same type within greenhouse was constructed. The simulation outcome of average daily temperature of each layer within the greenhouse was better than the simulation outcome of highest temperature of corresponding layer, worse than the simulation of lowest temperature of corresponding layer. The highest temperature of lower soil and daily temperature of soil were better than the upper layer. The simulated soil temperature was much more close to the observation when the observation was during 15-30 ℃. In other interval, it was lower than the observation. [Conclusion] The study offered theoretical reference for the growth environment of sunlight greenhouse plantation.

Low infrared emitter from Ti3C2Tx MXene towards highly-efficient electric/solar and passive radiative heating

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.

Visible transparent,infrared stealthy polymeric films with nanocoating of ITO@MXene enable efficient passive radiative heating and solar/electric thermal conversion

Visible transparent yet low infrared-emissivity(ε)polymeric materials are highly anticipated in many applications,whereas the fabrication of which remains a formidable challenge.Herein,visible transparent,flexible,and low-εpolymeric films were fabricated by nanocoating decoration of indium tin oxide(ITO)and MXene on polyethylene terephthalate(PET)film surface through magnetron sputtering and spray coating,respectively.The obtained PET-ITO@MXene(PET-IM)film exhibits lowεof 24.7%and high visible transmittance exceeding 50%,endowing it with excellent visible transparent infrared stealthy by reducing human skin radiation temperature from 32 to 20.8°C,and remarkable zero-energy passive radiative heating capability(5.7°C).Meanwhile,the transparent low-εPET-IM film has high solar absorptivity and electrical conductivity,enabling superior solar/electric to thermal conversion performance.Notably,the three heating modes of passive radiative and active solar/electric can be integrated together to cope with complex heating scenarios.These visible transparent low-εpolymeric films are highly promising in infrared stealth,building daylighting and thermal management,and personal precision heating.

Bacterial Cellulose-Based Janus Films with Radiative Cooling and Solar Heating Properties for All-Season Thermal Management

Advanced radiative cooling materials with both heating and cooling mode is of pivotal importance for all-season energy-saving in buildings.In this work,we report the design and fabrication of bacterial cellulose-based Janus films(J-BC)with radiative cooling and solar heating properties,which were developed by two-step vacuum-assisted filtration of modified MXene-doped bacterial cellulose and modified silicon nitride(Si_(3)N_(4))-doped bacterial cellulose,followed by hot-pressing and drying treatments.The as-prepared J-BC films show a unique Janus structure where modified MXene nanosheets and cellulose nanofibers are on the bottom surface,and modified silicon nitride(Si_(3)N_(4))nanoparticles and cellulose nanofibers are on the top surface.The radiative cooling effect of J-BC films is enabled by the Si_(3)N_(4)-doped bacterial cellulose due to the high mid-infrared emissivity of Si_(3)N_(4) nanoparticles,which shows a high solar reflection of~98.1%and high emissivity of~93.6%in the atmospheric transparency window(8-13μm).Thanks to the enhanced photothermal conversion of the modified MXene nanosheets,a reduced solar reflection(6.6%)and relatively low thermal emissivity in the atmospheric window(71.4%)are achieved,making sure the solar heating effect of J-BC films.In the outdoor tests,J-BC films achieve a sub-ambient temperature drop of~3.8°C and an above-ambient temperature rise of~14.2°C.Numerical prediction demonstrated that the J-BC films with dual modes have great potential of all-season energy saving for buildings and a corresponding energy-saving map in China is also created.The work disclosed herein can provide an avenue for the shaping of advanced radiative cooling materials for emerging applications of personal thermal management,sustainable energy-efficient buildings,and beyond.

Design and optimization of thermally responsive autonomous dynamic glazed attachment systems for building solar heat gain control

Windows,as transparent intermediaries between the indoors and outdoors,have a significant impact on building energy consumption and indoor visual and thermal comfort.With the recent development of dynamic window structures,especially various attachment technologies,the thermal,visual,and energy performances of windows have been significantly improved.In this research,a new dynamic transparent louver structure sandwiched within conventional double-pane windows is proposed,designed,optimized,and examined in terms of energy savings in different climates.The uniqueness of the proposed design is that it autonomously responds to the seasonal needs prompted by solar heat gain through the use of thermally deflected bimetallic elements.Moreover,by integrating spectral selective louvers into the system design,the dynamic structure enables strong solar infrared modulation with a little visible variation.The optical and thermal properties of the dynamic glazing structure support about 30%and 16%seasonal variations in solar heat gains and visible transmittance,respectively.Furthermore,the potential energy savings were explored via parametric energy simulations,which showed significant potential for heating and cooling energy savings.This proposed design demonstrates a simple smart dynamic glazing structure driven by seasonal temperature differences,with significant solar heat control capabilities and minor effects on the visible or visual quality of the glazing system.

Design and preliminary experimental research on a new biogas fermentation system by solar heat pipe heating

Biogas fermentation requires appropriate temperature,while the biogas fermentation can be affected by the low ambient temperature in winter.In order to overcome the negative effects of low temperature fermentation,a new type of solar heat pipe biogas fermentation heating system was designed and a preliminary experiment research on this system was conducted using cow manure as the raw material at 6%concentration and total fermentation volume of 175 L.The experimental results showed that when the system was in normal operation,the fermentation temperature rose every day by gradient.This gradient will gradually become smaller with the increase of fermentation liquid temperature,and the temperature can reach 38°C after stability.Using this solar heat pipe heating system,the fermentation liquid temperature can be increased by 5°C every sunny day.This solar heat pipe heating system plays a significant role in biogas fermentation.The results of economic analysis show that the system can realize the fermentation at constant temperatures of 25°C and 35°C respectively,and it can also save standard coal equivalent of 40 kg and 80 kg in winter and spring,respectively.