Air-conditioning Electricity Consumption Research Articles

Evaluation of the Effects of Window Films on the Indoor Environment and Air-Conditioning Electricity Consumption of Buildings

The objective of this study was to evaluate the effects of window films on indoor environmental conditions and electricity consumption of air conditioning. The research focused on the performance of different window films (HAG, RG), taking into account variations from different building orientations. The findings of this research indicated that building orientation could significantly influence the duration of direct sunlight entering the interior, with the areas closer to the glass being more susceptible to the effects of outdoor temperature and solar radiation. The clear glass with heat-absorbing film (HAG) and reflective film (RG) both reduced the indoor temperature and indoor illuminance while increasing indoor comfort. The RG could accumulate less heat on the glass surface compared with the HAG. The glass temperature of the RG will be lower than the HAG. The electricity-saving ratios of the HAG were 1.4%, 1.9%, 1.4%, and 1.2%, respectively, when facing the east, south, west, and northwest orientations compared with the clear glass (OG). The electricity-saving ratios of the RG were 3%, 4.2%, 4.2%, and 10.3%, respectively.

Occupancy-based one-year-ahead heating, ventilation, and air-conditioning electricity consumption optimization using machine learning

The world is increasingly urbanized. While, more than a half of its population lives in big cities, buildings are responsible for nearly the 40 % of the global annual energy consumption. Recent advances in smart grids and the high penetration of renewable energy sources have increased the need for long-term buildings' electricity consumption prediction to support operational decision making, demand response, and the installation of distributed generation systems. In addition, to meet international environmental goals, electric utilities usually offer financial incentives to reduce consumption levels. Heating, ventilation, and air-conditioning (HVAC) systems use the half of the buildings' energy to maintain users' comfort. In this scenario, predicting and optimizing their long-term electricity consumption without neglecting comfort conditions become vital to negotiate beneficious service-level agreements (SLAs) within the framework of demand-side management strategies. In this paper, we predict and optimize the one-year-ahead HVAC electricity consumption profile of a reference office building based on a machine learning approach. Although the occupants' number influences the HVAC electricity consumption, there has long been a lack of high-resolution, non-Boolean, long-term occupancy estimators. In this context, we first forecast the one-year-ahead occupants' number schedule and then use it, together with traditionally used historical weather data, to predict the one-year-ahead HVAC electricity consumption. The consumption profile is then optimized based on the estimated one-year-ahead occupants’ count schedule. The best results, obtained with a feedforward neural network, achieve 33 % annual electricity saving without neglecting summer cooling conditions in a hot zone like Miami, being efficient even in energetic-demanding scenarios such as extended working hours.

Activation of absorption chillers by the transit heat flow of the energy cycle in cogeneration solar systems

The problem of peak electricity consumption for air conditioning needs in countries with a hot climate is analyzed. It is determined that one of the ways to solve it is to create and use solar cogeneration coolers. The generation of electricity and cold in comparable proportions by such installations will reduce the load on generating electric capacities and create a reserve for connecting electric coolers. The combined use of power (turbine) cycles and industrial absorption chillers (one- and two-stage) has been explored. Evaluation of consumer qualities of a wide range of designs of cogeneration coolers is carried out using the developed thermal schemes based on Rankine cycles. The idea of the proposed method for constructing a cogeneration cooler is to use the turbine cycle waste heat to activate absorption chillers that operate in the normal mode. The study results showed that steam-to-water cogeneration coolers can be effectively used with a two-stage absorption chiller. It is shown that in the inverse mode such a cooler is able to provide efficient air heating in winter (up to +35 °C). It has been determined that the use of a butane cycle in the supercritical steam parameters region allows, with a little decrease of cogeneration cooler COP during in hot hours, to increase the cooling capacity by ∼2 times by reducing the intensity of regenerative heat flow transfer in the power unit. It has been established that the intensification of regenerative heat transfer in the power unit significantly affects on the system cooling capacity.

Domestic Electricity Consumption in Mexican Metropolitan Areas under Climate Change Scenarios

The following estimates analyse human bioclimatic conditions due to climate change in three time horizons, as suggested by Article 2 of the Paris Agreement. Each scenario corresponds to an increase in the global average temperature (∆T) of 1 ºC, 1.5 ºC and 2 ºC, respectively. The measurements of residential electricity consumption for air conditioning were made in 30 metropolitan areas of Mexico with at least half a million inhabitants in 2010. Bioclimatic conditions also included estimates of the effects of urban heat islands (UHI). Use of heating will decrease and, in some cases, disappear, while the need for cooling will increase. Electricity consumption due to cooling is expected to increase in Mexicali, Reynosa-Río Bravo (on the border with the United States), Cancún, Villahermosa, and Veracruz (on the shores of the Caribbean Sea and the Gulf of Mexico). Urban areas like Toluca, Pachuca, Xalapa, San Luis Potosí, and Puebla-Tlaxcala used little or no energy for cooling in the second decade of the 21st century but will need to do so halfway through the century.

Statistical analysis of air-conditioning and total load diversity in typical residential buildings

Electricity consumption by air-conditioners in residential buildings significantly affects the electrical grid. The stability of the grid can be improved by a precise prediction of air-conditioning (AC) variations. Therefore, more information about the electricity usage patterns specifically on AC load is important. This paper aims to determine the consumption patterns of AC and total load through a field measurement of 20 dwellings located in Kuala Lumpur and Selangor. Next, correlation and clustering are employed to identify the relationship between outdoor temperature and AC electricity consumption. The results revealed 75% of the occupants use the AC almost every day for about five to six hours per day at the rates of 0.93 kWh/day during day time and 3.43 kWh/day during night time. The correlation coefficient between the total daily AC consumption and the mean daily outdoor temperature ranged from -0.1 to 0.48. The variation of electricity consumption with time shows that AC electricity consumption increases with the increase of usage time. Lastly, the clustering process of AC usage pattern based on outdoor temperature displayed the uncommon behaviour from dwellings whereby high AC electricity consumption was recorded at low outdoor temperature.

Impacts of a warmer world on space cooling demand in Brazilian households

Air Conditioning (AC) appliances are a highly effective adaptation strategy to rising temperatures, thus making future climate conditions an important driver of space cooling energy demand. The main goal of this study is to assess the impacts of climate change on Cooling Degree Days computed with wet-bulb temperature (CDDwb) and household space cooling demand in Brazil. We compare the needs under three specific warming levels (SWLs) scenarios (1.5 °C, 2 °C and 4 °C) to a baseline with historically observed meteorological parameters by combining CDDwb projections with an end-use model to evaluate the energy requirements of air conditioning. The effects of the climate change were isolated, and no future expansion in AC ownership considered. Carbon dioxide (CO2) emissions associated with AC energy demand are also calculated. Results show an increase in both average CDDwb and AC electricity consumption for the global warming scenarios in all Brazilian regions. The Northern region shows the highest increase in CDDwb (187% in CDDwb for SWL 4 °C), while the Southeast presents the highest AC energy consumption response (326% in the AC energy consumption for SWL 4 °C) compared to the baseline. At the national level, CDDwb and the AC energy consumption in all SWLs scenarios grow by 70%, 99% and 190%, respectively.

District-Level Summertime Air-Conditioning Electricity Consumption and the Sensitivity of Peak Cooling Loads to Urban Weather Conditions in Beijing

AbstractUnderstanding how energy use responds to meteorological conditions is essential for anticipation of energy demands, which is of significance to maintain sufficient power supply and to prevent brownouts or blackouts during peak hours. Using the quarter-hourly and district-level electricity data for Beijing, this study calculates the district-varying cooling electric loads due to air-conditioning (AC) systems in five consecutive summers. Results show the occurrence of two major features that are common for summertime cooling loads in most districts, namely, double-peaked diurnal profiles and weekday–weekend fluctuations. With the increasing distance from the city core, the evening peak cooling load around 21:00 local time (LT) becomes more pronounced and comparable with its afternoon counterpart around 15:00 LT. Conversely, the weekday–weekend fluctuation is greatly weakened in suburban and rural districts due to the stable cooling demands on weekdays and weekends. The district-level sensitivity of peak cooling loads to surface meteorological factors is further investigated by linear regression analysis, and results show significant decreases from urban to rural districts. The correlation coefficients between peak cooling loads and heat index that combines air temperature and relative humidity reach up to 0.8–0.9 in most districts. If using air temperature or specific humidity solely, the coefficients of determination with peak cooling loads are roughly 0.1–0.3 smaller, possibly indicating the greater potential of heat index for effectively predicting peak cooling demands in Beijing.

An investigation of the cooling performance of air-conditioning systems in seven Chinese hub airport terminals

Airport terminals are key infrastructures with rapid development currently, where the air-conditioning (AC) systems aim to guarantee the normal operation. This research investigated the AC systems in seven Chinese hub airport terminals by a large-scale on-site measurement. The average annual electricity consumption was 177 kWh/(m2 · year), in which 30–60% was consumed by AC systems. The terminal device of AC systems is one of the key components restricting the cooling performance. The commonly used terminal devices (i.e. air handling units) accounted for 40–74% of the AC electricity consumption. As an alternative, the AC system combining radiant floor and displacement ventilation could save 34% of the AC electricity consumption in one investigated airport terminal. Furthermore, the designed cooling capacities were 132–176 W/m2, while the measured values were only 43–90 W/m2. Thus, the AC systems, especially the terminal devices, should have the ability to adjust cooling capacity over a wide range to cope with this prevailing situation of low load rates. This study is beneficial for the design and operation of AC systems in airport terminals.

Field Survey of Thermal Comfort and Sleep Quality in the Bedrooms with Different Cooling Strategies in Malaysia

This study aims to determine the indoor comfort temperature before sleep and after wake up in air-conditioning (AC) mode with different adaptive cooling strategies. Two units of guest rooms on the university campus were used with a total of 20 participants. The arbitrary-controlled AC setting (case 1) and control of thermostat setting by 3∘C higher than case 1 with installing of cool bed padding (case 2) were employed as cooling strategies in this study. The measurement parameters were indoor and outdoor air temperatures, globe temperature, relative humidity, air velocity, and AC electricity consumption. The questionnaire survey has also been distributed twice a day for “before going to bed” and “after waking up” during measurement simultaneously. It was observed that thermal sensation vote (TSV) indicated for both cases were within -1 ≤ TSV ≤ 1 and respondents might accept the present condition for both cases. Mean thermal preference (TP) in both cases either “before going to bed” and “after waking up” was found mostly close to “0 no change” (0.1 ≤ TP ≤ 0.3) for all cases. Overall comfort (OC) ranged between 4.7 and 4.9 for both cases, indicating for “comfortable.” However, air movement sensation (AMS) shows respondent felt weak airflow inside the room for all ventilation strategies. The skin moisture sensation (SMS) shows value pointed to neutral feeling for all cases. The comfort temperature obtained by Griffiths’ method was approximately 24∘C and 25∘C that for case 1 and case 2, respectively. Meanwhile, most of the respondents experienced calmness during sleeping and satisfied with their sleep in both cases. Sleep efficiency index (SEI) shows case 2 was higher rather than case 1. It seems the second adaptive cooling strategy might effective for reducing AC energy consumption by about 32% and increase 2% of SEI without affecting respondents’ thermal comfort.

Load and Household Profiles Analysis for Air-Conditioning and Total Electricity in Malaysia

Load profile of household air-conditioning (AC) and total electricity consumption is essential to increase the stability of the energy demand on the grid. Therefore, field measurements on time series data of total and AC electricity consumption from 20 households were conducted from March 2016 to August 2017. The questionnaire survey was carried out simultaneously to grasp the profile of each family. The average total daily and AC consumption were 14.5 kWh/day and 3.9 kWh/day, respectively. The average hourly electricity consumption for total was 0.6 kWh/hour, meanwhile for AC was 0.2 kWh/hour. About 20% of the total peak demand was contributed by the consumption of AC. The indoor air temperature was measured in the bedroom (BR) when AC was switched ON and OFF with an average of 27 ∘C and 29 ∘C, respectively. However, the indoor air temperature in the living room (LR) was 2∘C and 1∘C higher if compared to BR for both conditions. Based on the questionnaire survey, 92% of the occupants preferred a temperature setting below than the level recommended by the Malaysian standard i.e., 24 ∘C. These results might be beneficial to understand the occupant behavior of electricity demand in Malaysia for designing smart grid energy systems in the future.

Experimental investigation for solar thermal hybrid installs to inverter air conditioning vapour-compression cycle system

This study is designed a new development and integration for the solar hybrid system connected to an inverter air conditioning system. This experimental system will provide an essential addition to the renewable energy future. The device is supplying the same cooling load with significantly less electricity demand. Apparatus system has the solar unit and solar collector with DC compressor that was used to compress the refrigerant in an air conditioning system, and that will effectively reduce the air conditioning electricity consumption. The solar collector unit is installed between the compressor and condenser, which provide part of compression pressure and heating by further superheating the refrigerant. The higher pressure and more substantial temperature difference enhance the condensation process in the condenser, resulting in the high-pressure liquid refrigerant. This configuration realty reduces energy consumption by reducing the load on the electric compressor.

Numerical study and design of a dew point evaporative cooler for buildings

Refreshing air remains a crucial problem in warm climates where electricity consumption for air conditioning has become excessive and irrational for several years, notably in Algeria. Research in this field is increasingly oriented towards new techniques that can reduce costs and environmental impacts. Among these techniques, the evaporative dew point cooling technology is the most promising as it can cool outdoor air to temperatures below its wet bulb temperature. The aim of this work is to model and design a dew point cooler for french and algerian climates. This model is used to study the effect of the cooler parameters such as its length, water temperature and working air ratio on its cooling effectiveness and supply temperature.

Design of a dew point evaporative cooler for buildings in Mediterranean climate

Refreshing air remains a crucial problem in warm climates where electricity consumption for air conditioning has become excessive and irrational for several years, notably in Algeria. Research in this field is increasingly oriented towards new techniques that can reduce costs and environmental impacts. Among these techniques, the evaporative dew point cooling technology is the most promising as it can cool outdoor air to temperatures below its wet bulb temperature. The aim of this work is to model and design a dew point cooler for french and algerian climates. This model is used to study the effect of the cooler parameters such as its length, water temperature and working air ratio on its cooling effectiveness and supply temperature.

Energy and Economic Performance of Solar Cooling Systems in the Hot-Summer and Cold-Winter Zone

Building energy consumption has distinctly increased in the hot-summer and cold-winter zone in China. Solar cooling technology has been developed to reduce the increasing electricity consumption for air conditioning and to shift the peak load during hot summer days. This paper presents a performance simulation and economic analysis for both photovoltaic (PV) and thermal solar cooling systems compared to a reference system, which is composed of two electric heat pumps. The results show that 30.7% and 30.2% of primary energy can be saved by using the PV and the thermal system, respectively. The payback time is 6–7 years for the PV system, but more than 20 years for the thermal system based on current conditions in China. Therefore, the PV system is more suitable for practical application in the hot-summer and cold-winter zone. The thermal system could be an alternative when middle- and high-temperature solar thermal collector technology has been further developed, as well as following mass production of small- and middle-sized chillers.

Impacts of shading effect from nearby buildings on heating and cooling energy consumption in hot summer and cold winter zone of China

The authors studied five major municipalities (Shanghai, Wuhan, Changsha, Chengdu and Chongqing) in China's hot summer and cold winter zone, using eQUEST to perform numerical simulations of the effects of shading by nearby residences on electricity consumption for space cooling and heating. Space cooling demand reductions were as much as 10% to 20%, while space heating demand increases up to 20%. The shading effect from nearby buildings in the targeted region causes reductions in space cooling demand in summer, otherwise this effect outweigh increases in space heating demand in winter. In Shanghai and Wuhan, these two effects counteracted each other, but in Changsha, Chengdu and Chongqing, the effect of increased space heating demand in winter was barely discernible. The negative effect of shading in winter may be disregarded in the three inland municipalities (Changsha, Chengdu and Chongqing), designs may be proposed such that the shading effect from nearby buildings is maximized in summer. In contrast, for Shanghai and Wuhan it is probably more effective to design greater distances between buildings while applying a measure such as planting deciduous trees near the buildings to produce a shading effect from the leaves. Except in Shanghai, the highest reductions can be expected in residential building clusters designed with the suggested minimum distances between buildings. In Wuhan and Changsha, the current recommended minimum distances between buildings are favorable with regard to reducing electricity consumption for air conditioning. The authors extended the target region north and south (Ha’erbin, Beijing, Shanghai, Fuzhou and Haikou), examined the effects of differences in weather values on the calculation results.

DESIGN a solar hybrid air conditioning compressor system

This thesis presents the investigation into the feasibility of solar assisted vapour compression air conditioning system in providing thermal comfort in Malaysia. Conventional vapour compression air conditioning system consumes large amount of energy which is a clear disadvantage considering the high fuel price and electric tariff. Therefore, this research was intended to develop and integrate solar hybrid system into conventional air conditioning system which provides the same cooling load with considerably less electricity demand. In addition, Microsoft Excel spreadsheet is also prepared to facilitate the calculation of refrigerant temperature and energy saving of the system. DC compressor and evacuated tube solar compressor is introduced to assist the electric compressor in compressing the refrigerant, effectively reducing the air conditioning electricity consumption by up to 45%. Meanwhile, during night time, energy saving is only contributed by the DC compressor which reduces electricity consumption by up to 25%. The development and utilization of solar energy reduces the dependency on energy generation from fossil fuel which emits greenhouse gases and worsen the global warming while also pushing Malaysia one step closer to their aim in reducing CO₂ emissions and harnessing renewable energy. Malaysia as a tropical country with average solar radiation of 4500Wh/m² per day, has endless potential in solar energy (Borhanazad, 2013). This project provides technical overview which involves the study of solar energy conversion system and viability of solar hybrid vapour compression air conditioning system under Malaysia climate.

Air-conditioning energy consumption due to green roofs with different building thermal insulation

On hot days, green roofs could reduce heat flux into indoor space and air-conditioning energy use. Most thermal-benefit studies estimate energy saving based on temperature measurements. A field experiment on the roofs of two residential buildings in subtropical Hong Kong was designed to measure air-conditioning electricity consumption in relation to three factors: (1) building thermal insulation (BTI): omitted at Block 1 and installed at Block 2; (2) green-roof type: each block had a bare (Control) and two extensive green-roof plots, namely simple Sedum and more complex herbaceous Peanut vegetation; and (3) three summer weather scenarios: sunny, cloudy, and rainy. Air-conditioning electricity consumption of six vacant apartments below the experimental plots was monitored by precision energy loggers. Under all weather conditions, the unshielded Control imposes high cooling load at Block 1, but BTI at Block 2 cuts heat ingress. Sedum reduces more energy consumption than Control at both blocks, with Block 2 better than Block 1. The best effect occurs on sunny day, followed by cloudy and rainy. Sedum roof with BTI enhances thermal benefit. Without BTI, Sedum roof consumes more energy, hence the simple green roof cannot substitute BTI function. Under three weather scenarios, Peanut uses more electricity at Block 2 than Block 1, indicating the joint operation of green-roof heat-sink effect (GHE) and building heat-sink effect (BHE) at Block 2. Thicker substrate with higher moisture-holding capacity generates GHE. Added BTI material layers create BHE, with thermal resistance reduced by moisture penetration and elevated temperature. Their joint effect has raised thermal mass and thermal capacity. A rather steep thermal gradient is formed to induce thermal-insulation breaching to push heat into indoor space. At Block 1, Peanut roof can partly compensate for omission of BTI. At Block 2, however, Peanut coupled with BTI can synergistically increase cooling load. The findings can inform policies and design of green roof and associated BTI in cities with hot summer.

Assessing summertime urban air conditioning consumption in a semiarid environment

Evaluation of built environment energy demand is necessary in light of global projections of urban expansion. Of particular concern are rapidly expanding urban areas in environments where consumption requirements for cooling are excessive. Here, we simulate urban air conditioning (AC) electric consumption for several extreme heat events during summertime over a semiarid metropolitan area with the Weather Research and Forecasting (WRF) model coupled to a multilayer building energy scheme. Observed total load values obtained from an electric utility company were split into two parts, one linked to meteorology (i.e., AC consumption) which was compared to WRF simulations, and another to human behavior. WRF-simulated non-dimensional AC consumption profiles compared favorably to diurnal observations in terms of both amplitude and timing. The hourly ratio of AC to total electricity consumption accounted for ∼53% of diurnally averaged total electric demand, ranging from ∼35% during early morning to ∼65% during evening hours. Our work highlights the importance of modeling AC electricity consumption and its role for the sustainable planning of future urban energy needs. Finally, the methodology presented in this article establishes a new energy consumption-modeling framework that can be applied to any urban environment where the use of AC systems is prevalent.

Research of Artificial Sites Green Roof for Energy-Saving Efficiency in Taiwan Taichung

In this study, set the empirical plane pilot area planting the groove (long 425cm × width 300cm × Height 20cm ) in the Taichung City residential area on the second floor roof, planting the groove bottom-up sequence laying frame high-rise, water proof layer, drainage layer,filter layer (non-woven, water-pottery-stone), the medium layer and planting of layer, planting the groove around the hollow brick interval income side to lighten the load. Noon hours exposed roof temperature of 25.49-37.56°C, green roofs surface only at 16.45-24.69°C, 17.74-24.79°C indoor temperature on the second floor, effectively prevent the roof surface temperature rise, and thus reduce the interior roof of the second temperature7.75-12.77°C. Building green roofs to cooling, mainly to reduce the building temperature, reducing air conditioning electricity consumption , accomplish cooling and energy-saving benefits.Compare different annual electricity consumption in the same period, extensive green roof to total electricity consumption of 860 K.Watts/hours , exposed roof to total electricity consumption in 1767 K.Watts/hours, 48.67% of the electricity consumption savings, to achieve energy efficiency.

The function of solar absorbing window as water-heating device

While window glazing will be more and more extensively used in modern architecture, the increase in space thermal load as a result will deteriorate the global environment, incurring problems of air pollution and climate change. By connecting the cavity of a double pane window to a water-flow circuit, absorbed solar heat at the window glasses can be readily removed by the water stream. The water passage in this way can effectively lower the glass pane temperature, reduce room heat gain and therefore, the air-conditioning electricity consumption. Thermal comfort can be enhanced. Furthermore, the water-flow window can function as a hot-water preheating device. This article reports the integrative thermal performance of a water-flow absorbing window as compared to the conventional single and double pane absorptive glazing. The results based on the operation in health club environment are very encouraging. This demonstrates its good application potential in domestic–commercial buildings with stable hot-water demands.