Research on Operation Optimization of Heating System Based on Electric Storage Coupled Solar Energy and Air Source Heat Pump

For heating systems based on electricity storage coupled with solar energy and an air source heat pump(ECSA),choosing the appropriate combination of heat sources according to local conditions is the key to improving economic efficiency.In this paper,four cities in three climatic regions in China were selected,namely Nanjing in the hot summer and cold winter region,Tianjin in the cold region,Shenyang and Harbin in the severe cold winter region.The levelized cost of heat(LCOH)was used as the economic evaluation index,and the energy consumption and emissions of different pollutants were analyzed.TRNSYS software was used to simulate and analyze the system performance.The Hooke-Jeeves optimization algorithm and GenOpt software were used to optimize the system parameters.The results showed that ECSA systemhad an excellent operation effect in cold region and hot summer and cold winter region.Compared with ECS system,the systemenergy consumption,and the emission of different pollutants of ECSA system can be reduced by a maximum of 1.37 times.In cold region,the initial investment in an air source heat pump is higher due to the lower ambient temperature,resulting in an increase in the LOCH value of ECSA system.After the LOCH value of ECSA system in each region was optimized,the heating cost of the system was reduced,but also resulted in an increase in energy consumption and the emission of different pollutant gases.

Experimental evaluation of factors affecting performance of concentrating photovoltaic/thermal system integrated with phase‐change materials(PV/T‐CPCM)

The photovoltaic/thermal(PV/T)system is a promising option for countering energy shortages.To improve the performance of PV/T systems,compound parabolic concentrators(CPCs)and phase-change materials(PCMs)were jointly applied to construct a concentrating photovoltaic/thermal system integrated with phase-change materials(PV/T-CPCM).An open-air environment is used to analyze the effects of different parameters and the intermittent operation strategy on the system performance.The results indicate that the short-circuit current and open-circuit voltage are positively correlated with the solar irradiance,but the open-circuit voltage is negatively correlated with the temperature of the PV modules.When the solar irradiance is 500 W⋅m^(−2) and the temperature of the PV modules is 27.5℃,the short-circuit current and open-circuit voltage are 1.0 A and 44.5 V,respectively.Higher solar irradiance results in higher thermal power,whereas the thermal efficiency is under lower solar irradiance(136.2-167.1 W⋅m^(−2) is twice under higher solar irradiance(272.3-455.7 W⋅m^(−2))).In addition,a higher mass flow rate corresponds to a better cooling effect and greater pump energy consumption.When the mass flow rate increases from 0.01 to 0.02 kg⋅s^(-1),the temperature difference between the inlet and outlet decreases by 1.8℃,and the primary energy-saving efficiency decreases by 0.53%.The intermittent operation of a water pump can reduce the energy consumption of the system,and the combination of liquid cooling with PCMs provides better thermal regulation and energy-saving effects under various conditions.

Thermal environment investigation of asymmetric radiation coupled with convection heating

The couple of radiation with convection heating owned advantages of less energy utilization,healthier and more comfortable indoor environment.However,local thermal discomfort was often induced by large vertical temperature difference and radiation asymmetry temperature.This work studied indoor thermal environment characteristics under different coupling ways of radiation and convection heating terminals through experiments and CFD simulation.The studied five scenarios were denoted as:(Ⅰ)lateral air supply+adjacent side wall radiation,(Ⅱ)lateral air supply+opposite side wall radiation,(Ⅲ)lateral air supply+floor radiation,(Ⅳ)lateral air supply+adjacent side wall radiation+floor radiation,and(Ⅴ)lateral air supply+opposite side wall radiation+floor radiation.The overall thermal comfort indices(including air diffusion performance index(ADPI),predicted mean vote(PMV),and predicted percent of dissatisfaction(PPD))and local thermal comfort indices under different scenarios were investigated.For Scenarios Ⅰ-Ⅲ,the local dissatisfaction rates caused by vertical air temperature difference were 0.4%,0.1%,and 0.2%,respectively,which belonged to"A”class according to the ISO-7730 Standard.While the vertical asymmetric radiation temperature of Scenario Ⅰ-Ⅱ was about 6.5℃ lower than that of Scenario Ⅲ-Ⅳ-Ⅴ.The ADPI for Scenarios Ⅲ-Ⅴ were about respectively 5.7%,16.7%,and 21.0%higher than that of Scenarios Ⅰ-Ⅱ,indicating that a large radiation area and radiation angle coefficient could reduce the discomfort caused by radiant temperature asymmetry.The coupling mode improved local discomfort by decreasing vertical temperature difference and radiation asymmetry temperature wherefore improving the PMV from-1.6 to-1.The lateral air supply coupled with asymmetric radiation heating could potentially improve the thermal comfort of occupied area,while the comprehensive effect of thermal environmental improvement,energy-saving,and cost-effectiveness needes to be further investigated.

Comparison study of thermal comfort and energy saving under eight different ventilation modes for space heating

The relative location of inlets and outlets plays an important role in thermal comfort and energy conservation under ventilation modes for the building non-uniform indoor environment.Hence,a comparison study of thermal comfort and energy efficiency of eight widely-used ventilation modes for space heating was conducted in this study.Both subjective experiments and verified computational fluid dynamics(CFD)models were carried out.In the subjective experiments,the vote of local thermal sensation(LTS),overall thermal sensation(OTS)and draft sensation were collected.In the CFD simulations,RNG κ-ε model was applied to compare and analyze the air temperature field,turbulence intensity,ventilation effectiveness and air diffusion performance index(ADPI).The thermal comfort results showed that the air inlets are better located at the mid-height level of a wall,and the outlets are located at the same or higher height.While the results of the energy efficiency suggested that the inlets are better installed at the lower level of a wall,and the outlets should be placed far from the inlets.Since the results were conflict,the economic-comfort ratio was introduced to calculate and compare the thermal comfort and energy efficiency simultaneously.The final results concluded that it can achieve excellent thermal comfort performance without sacrificing energy efficiency when the inlets are at the height of 1.2 m of the front wall,and the outlets are at 1.2 m height of the back wall.Hence it is the best choice for the winter air distribution in northern China.This study can offer a guideline for the air terminal arrangements in non-uniform ventilation under heating mode.

Investigation of thermal environment and the associated energy consumption of transportation buildings along the expressways in the cold region of China:A case study

The transportation buildings alongside the expressways(TBE)have comprehensive characteristics,providing shopping and accommodations for drivers and passengers.However,the indoor thermal environment and energy consumption of such service buildings was not covered in most studies.To this end,based on some typical TBEs,this study investigated the thermal environment and energy consumption characteristics for TBEs.And the men-tioned TBEs are located in Xiong’an New Area,a national special zone with requirements of low carbon and low energy consumption in China’s cold region.The thermal environment study included questionnaire survey and on-site investigation by adopting dynamic thermal comfort evaluation index(i.e.,Relative Warmth Index(RWI)and Heat Deficit Rate(HDR)).Then,the TBE energy consumption was investigated with the main influencing factor analyses.Finally,numerical simulations were conducted to analyze the energy efficiency approaches in TBE.The results showed that RWI and HDR were able to evaluate the thermal comfort of personnel in transi-tional environment of TBE in winter.Meanwhile,when the room temperature was set as 16℃,it was still able to maintain the thermal environment for the indoor staff.The main energy influencing factors of TBEs are building scale,system equipment and usage characteristics.Besides,it was practicable to adopt the heat pump system to replace conventional space heating and cooling system,of which the total energy consumption of geothermal heat pump reduced by 38.1%.

Robustness of ventilation systems in the control of walking-induced indoor fluctuations: Method development and case study

Walking-induced fluctuations have a significant influence on indoor airflow and pollutant dispersion.This study developed a method to quantify the robustness of ventilation systems in the control of walking-induced fluctuation control.Experiments were conducted in a full-scale chamber with four different kinds of ventilation systems:ceiling supply and side return(CS),ceiling supply and ceiling return(CC),side supply and ceiling return(SC),and side supply and side return(SS).The measured temperature,flow and pollutant field data was(1)denoised by FFT filtering or wavelet transform;(2)fitted by a Gaussian function;(3)feature-extracted for the range and time scale disturbance;and then(4)used to calculate the range scale and time scale robustness for different ventilation systems with dimensionless equations developed in this study.The selection processes for FFT filtering and wavelet transform,FFT filter cut-off frequency,wavelet function,and decomposition layers are also discussed,as well as the threshold for wavelet denoising,which can be adjusted accordingly if the walking frequency or sampling frequency differs from that in other studies.The results show that for the flow and pollutant fields,the use of a ventilation system can increase the range scale robustness by 19.7%-39.4% and 10.0%-38.8%,respectively;and the SS system was 7.0%-25.7% more robust than the other three ventilation systems.However,all four kinds of ventilation systems had a very limited effect in controlling the time scale disturbance.

Numerical study of thermal characteristics of double skin facade system with middle shade

Architectural shade is an effective method for improving building energy efficiency.A new shade combined with the double skin façade(DSF)system,called middle shade(MS),was introduced and developed for buildings.In this paper,a 3D dynamic simulation was conducted to analyze the influence of MS combined with DSF on the indoor thermal characteristics.The research on MS for DSF involves the temperature,the ventilation rate,the velocity distribution of the air flow duct,and the indoor temperature.The results show that the angle and position of the shade in the three seasons are different,and different conditions effectively enhance the indoor thermal characteristics.In summer,the appearance of MS in DSF makes the indoor temperature significantly lower.The indoor temperature is obviously lower than that of the air flow duct,and the temperature of the air flow duct is less affected by MS.The influence of the position of blinds on indoor temperature and ventilation rate is greater than the influence of the angle of blinds.According to the climate characteristics of winter and transition season,in winter,early spring,and late autumn,the indoor temperature decreases with the increase of the position of blinds at daytime,but the opposite is true at night.The results found in this paper can provide reference for the design and use of MS combined with DSF in hot summer and cold winter zone.

Differences in root stress and strain distribution in buccal and lingual orthodontics: A finite element analysis study

Orthodontic forces can cause stress and strain concentration and microcracks on tooth root surfaces.This study aimed to analyze whether a lingual orthodontic appliance was more likely to cause root stress concentration and root resorption than the traditional buccal appliance.A finite element model of the root of the maxillary central incisor with straight,buccal,and lingual curvatures was established.A load perpendicular to the tooth surface on the buccal and lingual surfaces of the central incisor was applied,and the stress and strain concentration at the root apex was compared.The stress and strain at the root apex of the lingual cingulum group were lesser than those of the buccal group;little difference was observed between the lingual and buccal clinical crown central augmentation groups.The stress and strain at the root apex of the lingual direction movement group were greater than those of the buccal direction movement group.The direction of the root curvature also influenced the amount of stress and strain at the root apex.The difference in the risk of root resorption between lingual and buccal orthodontics is dependent on the height of the bracket placement.The loading direction of the orthodontic force and direction of the root curvature also affect the stress and strain at the root apex.