Changes In Outdoor Air Temperature Research Articles

Dynamic energy optimization strategy to provide appropriate thermal comfort and fresh air under occupants’ different activity types

An effective strategy for optimizing indoor air distribution in stratum ventilation heating systems under different types of human activity has been proposed, in order to provide appropriate thermal comfort while exploiting the potential for energy savings. The stratum ventilation was optimized using strategy 1 (the optimization strategy of three ventilation performance indicators based on VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR)), the strategy 2 (the optimization strategy with constraint based on VIKOR) and the strategy 3 (the optimization strategy aimed at energy conservation), respectively. These strategies provide optimal indoor air distribution within a stratum ventilation system that is influenced by various factors (i.e. supply air temperature, supply air vane angle, supply air velocity, metabolic rate, clothing insulation and outdoor air temperature). Firstly, the parameters of the stratum ventilation system are obtained using Computational Fluid Dynamics (CFD) software. In addition, using the simulation results as input variables, predictive models of ventilation performance (i.e., PMV, local mean air age (LMAA) and energy consumption) was developed using Artificial Neural Network (ANN). Finally, by optimizing the proposed ANN based strategy 1, strategy 2 and strategy 3, the ventilation performance is output. The proposed strategy 1 provides a comfortable indoor environment and saves energy, and compared to the strategy 1, the strategy 3 saves more energy while ensuring that thermal comfort meets the requirements. In addition, considering the optimization of clothing insulation while providing appropriate thermal comfort also indirectly saves energy. Moreover, these strategies also work well as the outdoor air temperature changes.

Heat load-carrying capacity of surface water source and its heating load matching characteristics

Meteorological parameter changes not only affect the heat load-carrying capacity of the surface water, but also affect the heat load demand of the building, thus changing the heat load matching between the water source heat pump system and the users. In order to study the climatic adaptation of the heat load-carrying capacity, this paper establishes an analytical model of the water body's heat load-carrying capacity and the building's heat load with the solar radiation intensity, the change of the water body and the heat extraction time as variables. Experimental and simulation studies on the heat load-carrying capacity of lake water were carried out under the winter climate conditions in hot summer and cold winter areas. The results show that increasing the depth or area of the lake can improve the heat load-carrying capacity. Solar radiation is an important factor affecting the temperature of surface water body, the stronger the solar radiation the greater the temperature rise of the water body. Changes in outdoor air temperature have a significant impact on water temperature, and a sudden drop in outdoor air temperature will result in a sharp drop in water temperature. When the water body area was 3000 m2 and 50000 m2, the maximum integrated temperature drop of the water body was 15.0℃ and 9.7℃, which was 2.02 and 4.85 times of the temperature drop of heat extraction, respectively. Reduced heat load-carrying capacity of the surface water body or decreased COP of the heat pump is an important reason why the surface water source heat pump heat supply fails to meet the user's heat demand in winter.

Optimization for the Model Predictive Control of Building HVAC System and Experimental Verification

This article presents an optimized prediction model of building dynamic HVAC system load, which simplifies the input parameters of the model while meeting the accuracy requirements of the prediction results. The model was established using the open-source Modelica-based building library, and the linear aggregation method was used to establish the model. A reduced-order model was developed, and the accuracy of the simplified and reduced-order models was verified. A control strategy was constructed using the indoor mean radiant temperature (MRT) aggregated from a simplified prediction model of HVAC system load as the target feedback parameter, and its feasibility was verified experimentally. It was found that the MRT adopted by the new control strategy can reflect the changes in outdoor air temperature and load in a timely manner; moreover, using this as a control parameter can significantly reduce the influence of load changes to maintain a stable indoor temperature. The control system is further simplified by the predictive model, which improves the engineering practicability by maintaining the control accuracy.

Chilled water temperature set-point reset based on outdoor air temperature and its cooling energy performance in an office building

In this study, the cooling energy performance of two strategies for controlling ChWT (chilled water temperature) are compared: the conventional control strategy of constantly fixing ChWT and the OAT (outdoor air temperature) compensation control strategy that adjusts ChWT according to the changes in OAT. OAT compensation control strategy was modeled and realized based on Appendix G of ASHRAE Standard 90.1. It was confirmed that applying OAT compensation control strategy can significantly reduce chiller energy consumption, which accounts for the largest portion of total cooling energy consumption. It was found that the difference in total cooling energy consumption between applying the conventional control of constantly fixing ChWT to 6 °C and applying the OAT compensation control was approximately 8 % and 3 % during spring (March to May) and summer (June to August), respectively. Additionally, during the fall (September–November) period, about 7 % of total cooling energy consumption could be saved.

Bin Weather Data for HVAC Systems Energy Calculations

The increase in global air temperature is well documented, as during the last several years each decade has been consecutively warmer than the preceding. As climatic conditions affect the energy performance of buildings, the changes in outdoor air temperature and humidity will inevitably lead to significant alterations in energy consumption and costs for the heating, ventilating and air conditioning (HVAC) of buildings. The availability and quality of climatic data play an important role in the accuracy of energy analysis results. In this study, the hourly temperature and relative humidity of outdoor air measurements, for a period of three decades (1983–2012), recorded at the climatic station of the National Observatory of Athens were processed, and an up-to-date set of specific data for the application of bin methods was produced and presented. The data were then used to calculate changes in the energy demands in a typical office building throughout the specified period. Results showed a progressive reduction in the low and increase in the high temperature intervals, leading to an increase in the building’s annual energy requirements for air conditioning of up to 14.5% from the first to the third decade, with decrease in the energy demands for heating and increase in the energy demands for cooling.

Experimental Investigation of Air-Source Heat Pump Heating System With a Novel Thermal Storage Refrigerant-Heated Panel

Abstract In response to the triple crisis of energy–environment–economy (3Es), the air-source heat pump (ASHP) system is considered to be one of the most feasible candidates to upgrade the traditional high emission heating solutions. In this paper, a novel thermal storage refrigerant-heated panel (RHP) is proposed for the ASHP heating system. Experiments were conducted in a climate chamber to test the heating and defrosting performance of the system, the thermal performance of the RHP, the system energy efficiency, and the system economic feasibility. The results show that the heat flux of the RHP is as high as 625.5 W/m2 at a condensation temperature of 40 °C and an outdoor air temperature of −7 °C. Meanwhile, the system is demonstrated to be reliable and competitive with efficient thermal stability in heating conditions and comfortable indoor thermal in defrosting conditions. The coefficient of performance (COP) ranges from 2.2 to 4.0 when the outdoor air temperature changes from −12 °C to 7 °C in the tests. Meanwhile, the initial capital cost and the total annual cost of the proposed system are 430 USD and 203.1 USD, respectively, which is competitive in the distracted heating systems.

Impact of short-term thermal experience on thermal sensation: A case study of Chongqing, China

Sudden changes in outdoor air temperature within the time scale of several days can affect human thermal comfort demand. Although the influence of short-term thermal experience on the thermal sensation (STEI) in one season (e.g., in summer) has been focused on, the differences of this effect in different seasons have rarely been studied. In this study, to investigate the regularity of the difference, a follow-up field survey was conducted from July 2019 to January 2020 in Chongqing, China. The results show that when outdoor air temperature suddenly rises, the STEI is higher in summer than that in autumn (approximately 0.14 scales) when the indoor air temperature is 28–30 °C. When the indoor air temperature is 24–27 °C, no significant difference was observed. In addition, the STEI is higher in autumn than that in summer (approximately 0.09 scales) when the outdoor air temperature suddenly decreases, and when the STD is −1 °C, the impact of short-term thermal experience on the body in autumn is less than that in winter, by approximately 0.04 scales. The effect can cause a variation of approximately 0.28–0.84 °C in the body's neutral temperature, with a maximum of 1.3 °C based on Griffiths method (G = 0.356/K).

Mathematical modeling of the forecast and standby heating modes

The aim of the work is the development and study of methods for reducing the cost of heat energy for heating buildings and constructions by means of usage of automated control systems based on a programmable logic controller. Methods : In contrast to the known methods, the proposed mathematical model of non-stationary processes in heat-intensive enclosures makes it possible, according to the adaptive control algorithm, to perform forecast and standby heating taking into account the time dependence of the outdoor air temperature. Results: The algorithm ensures the equality of the heating system power and the heat losses power, allows one to maintain the desired indoor air temperature in the room when the outdoor air temperature changes. The heat loss compensation mode is achieved without using the temperature chart parameters of the network water and the parameters of proportional-integral-differential control laws that are necessary to set up at common automatic heating control systems. When calculating the forecast and standby heating modes, the mathematical model allows, at given initial and final temperatures of the internal air, determining the heating system power, which provide the desired temperature at the end of a specified period of time. The adaptive control algorithm allows setting the calculated outdoor temperature and the desired internal air temperature at any time. Under the forecast control, the mathematical model allows determining the system power at which the internal air temperature will remain almost constant when the outdoor air temperature changes. Conclusions: The developed algorithm of adaptive control allows one to create an energy-efficient heating system that provides the desired room temperature with minimum consumption of thermal energy taking into account all parameters affecting the heat loss power and the heating system power

HEATER-TRANSFER AGENT OBJECTIVE PARAMETERS IN HEAT SUPPLY SYSTEM WITH ACCOUNT OF EQUIPMENT ACTUAL CHARACTERISTICS

The economy heating energy at sources and objects of its final consumption is one of the energy saving ways. The actual task is selecting the most effective method for regulating heat tempering. The developed methods and means of rational parameters choosing of the heater-transfer agent when heat tempering from the source take into account the equipment objective parameters of elements of the heat supply system and their interference. The task to minimize the consumption of means for natural gas and electrical energy in order to provide the required air parameters in the consumers premises in the entire range of outdoor air temperature changes in the heating season are assigned and solved. The temperature rational law regulation of the heater-transfer agent at its rational consumption is building.

Location and optimization analysis of capillary tube network embedded in active tuning building wall

In this study, a building wall with a thermal tuning function is further investigated. This design turns the building wall from a passive thermal system to an active system. A capillary tube network is installed inside the wall to manipulate the thermodynamics and realize more flexibility and potentials of the wall. This novel building wall structure performs efficiently in terms of building load reduction and supplementary heating and cooling, and the structure is convenient for applying low grade or natural energy with a wider temperature range. The capillary tube network's location inside the wall greatly impacts the thermal and energy performance of the building wall. The effects of three locations including external, middle and internal side are analyzed. The results indicate that the internal wall surface temperature can be neutralized from the ambient environment when the embedded tubes are fed with thermal water. The wall can work with a wide range of water temperature and the optimal location of the tube network is relatively constant in different modes. Power benefit with the wall changes from 2 W to 39 W when the outdoor air temperature changes, higher in summer than in winter.

Hourly test reference weather data in the changing climate of Finland for building energy simulations.

Dynamic building energy simulations need hourly weather data as input. The same high temporal resolution is required for assessments of future heating and cooling energy demand. The data presented in this article concern current typical values and estimated future changes in outdoor air temperature, wind speed, relative humidity and global, diffuse and normal solar radiation components. Simulated annual and seasonal delivered energy consumptions for heating of spaces, heating of ventilation supply air and cooling of spaces in the current and future climatic conditions are also presented for an example house, with district heating and a mechanical space cooling system. We provide details on how the synthetic future weather files were created and utilised as input data for dynamic building energy simulations by the IDA Indoor Climate and Energy program and also for calculations of heating and cooling degree-day sums. The information supplied here is related to the research article titled “Energy demand for the heating and cooling of residential houses in Finland in a changing climate” [1].

Urban heat island characteristics in London during winter

This paper presents results characterising the urban heat island intensity (UHI) in London during the peak winter season. Most UHI studies focus on the phenomenon during the summer as this is the period when temperature peaks are observed. However, for urban planning mitigation strategies and building energy demand design, the heating season should be also considered, since proposed measures to alleviate the summer UHI might have a negative effect during the winter or intermediate seasons. The study carries out trend and regression analysis by controlling climatic and geographical variations in the data set following a methodology developed for studying summer UHI [Kolokotroni, M., Giridharan, R., 2008. Urban heat island intensity in London: an investigation of the impact of physical characteristics on changes in outdoor air temperature during summer. Solar Energy 82, 986–998]. It was found that average nocturnal UHI of winter periods are of similar magnitude to the summer periods but the peak winter UHI trends are not as regular as summer giving a first indication that the effect of climate and urban parameters is different. The regression analysis in this research uses six on-site variables namely aspect ratio, surface albedo, plan density ratio, green density ratio, fabric density ratio and thermal mass to carry out impact investigation in six data sets, categorised by three geographical location within London and three sky conditions and regional wind velocity. The above variables do not explain the changes in outdoor temperature as much as they did during summer period models. However, unlike summer, the winter climate control models have the same R 2 indicating that most of changes in outdoor temperature are caused by climate factors and not the on-site variables.

Urban heat island intensity in London: An investigation of the impact of physical characteristics on changes in outdoor air temperature during summer

The study looks at the potential of physical characteristics in mitigating the urban heat island intensity (UHI) in London during summer. This research uses six on-site variables namely aspect ratio, surface albedo, plan density ratio, green density ratio, fabric density ratio and thermal mass for the investigation in six data sets. The climatic variations in summer are controlled by classifying the data into clear sky, partially cloudy and cloudy periods. Geographical variation is controlled by classifying the data into core, urban and semi urban areas. Maximum daytime UHI of 8.9 °C is found in semi-urban area during partially cloudy period while maximum nocturnal UHI of 8.6 °C is found in urban area during clear sky period when the wind velocity is below 5 m/s. The most critical climate and geographical location in determining the changes in outdoor air temperature in London are partially cloudy periods and urban areas respectively. Among the variables studied, most critical variable that determines the daytime and nocturnal changes in outdoor air temperature is surface albedo.

Photosynthetic capacity of red spruce during winter.

We measured the photosynthetic capacity (P(max)) of plantation-grown red spruce (Picea rubens Sarg.) during two winter seasons (1993-94 and 1994-95) and monitored field photosynthesis of these trees during one winter (1993-94). We also measured P(max) for mature montane trees from January through May 1995. Changes in P(max) and field photosynthesis closely paralleled seasonal changes in outdoor air temperature. However, during thaw periods, field photosynthesis was closely correlated with multiple-day temperature regimes, whereas P(max) was closely correlated with single-day fluctuations in temperature. There was a strong association between short-term changes in ambient temperature and P(max) during the extended thaw of January 1995. Significant increases in P(max) occurred within two days of the start of this thaw. Repeated measurements of cut shoots kept indoors indicated that temperature-induced increases in P(max) can occur within 3 h. Although significant correlations between P(max) and stomatal conductance (g(s)) or intracellular CO(2) concentration (C(i)) raised the possibility that increases in P(max) resulted from increases in stomatal aperture, fluctuations in g(s) or C(i) explained little of the overall variation in P(max). Following both natural and simulated thaws, P(max) increased considerably but plateaued at only 37% of the mean photosynthetic rate reported for red spruce during the growing season. Thus, even though shoots were provided with near-optimal environmental conditions, and despite thaw-induced changes in physiology, significant limitations to winter photosynthesis remained.