Sensory pollution loads in six office buildings and a department store

Sensory pollution loads were measured in six non-smoking office buildings with mechanical ventilation without recirculation, and in a non-smoking department store with an air-conditioning system and recirculation. Untrained panels assessed the air quality on normal weekdays with occupants in the buildings, and in the case of office buildings, also on weekends without occupants present. On both occasions the ventilation system was in operation as on a normal working day. Outdoor airflow rate, air temperature, relative humidity and concentration of carbon dioxide were measured. The sensory pollution load from the building (without occupants) was found in offices to be 0.11 ± 0.09 olf/m² floor, which agrees well with the load recommended for low-polluting buildings in CEN CR 1752. This load is only half of the sensory pollution load found in previous investigations in offices and assembly halls where smoking was allowed. The load from building and merchandise in the department store was 0.15 olf/m² floor. A table is provided listing the mean sensory pollution load of the buildings measured in the present and in previous studies carried out in the period from 1988 to 2001 in different types of buildings in Europe. The table covers 120 buildings including offices and assembly halls (with and without previous smoking), schools, kindergartens and a department store.     

Night ventilation and active cooling coupled operation for large supermarkets in cold climates

Night ventilation and active cooling coupled operation strategy is studied for the large supermarkets in cold climates in China. The model on the thermal storage of the indoor goods is set up. Furthermore, based on the thermal balance of the whole room, the temperature change model is founded. The coupled operation process is simulated for the typical supermarket buildings. The overall energy consumption of the system is analyzed. The result shows that the opening time, duration and air flow rate of night ventilation all affect the performance of active cooling. Active cooling will influence night ventilation too. It also turns out that the coupled operation leads to shorter operation time of active cooling. The various operation modes are given at different climatic conditions. Compared with the normal active cooling system, the coupled operation system can save energy at 2.99 kWh/(m² a) in cold climates in China while 3.24 kWh/(m² a) in Harbin.     

Case study of data centers’ energy performance

This paper addresses the issue of energy performance of data centers by closely examining energy use of two data centers in commercial office buildings. The primary objective of the study is to examine an empirical energy use pattern of data centers under tropical climatic conditions, and give guidance for data centers’ design, operation and maintenance and retrofitting to achieve better energy performance. Actual energy use characteristics, design criteria, and energy and cost saving potentials were analyzed and compared between two data centers. Methodology of energy performance evaluation of data centers was discussed. The study concludes that data centers were high energy consuming areas in commercial office buildings—energy consumptions of approximately 3000 kWh/(m² year) and 2000 kWh/(m² year), respectively, were observed in the case studies. Power demands were often grossly over-provided in these facilities. This leaded to substantial increase in capital and running cost, which can be wasteful. Disparity in energy performance between case studies demonstrated the need for design guidelines and practical benchmarking. In one case study, approximately 56% (1.2 GWh/year) of energy consumption could be conserved through efficient designs of base infrastructure and energy consuming systems, as compared to better practice. The predicted cost saving is more than US$ 80,000 per year.     

Small power equipment loads in UK office environments

This paper presents figures for the small power equipment loads encountered by the Welsh School of Architecture in UK offices while undertaking a programme of research and monitoring into the energy efficiency of air-conditioning systems in use. The findings are based on surveys undertaken in 30 air-conditioned offices between April 2000 and October 2002. Peak small power equipment loads were calculated using the CIBSE nameplate-ratio method. The results show that the small power loads averaged 17.5 W/m² with a range between 6 and 34 W/m² of treated floor area. When normalised for occupancy the calculated peak small power equipment loads averaged 158 W per person, with a range between 124 and 229 W per person. Current industry guidance could lead to the overestimation of small power equipment loads by as much as 650%, ultimately resulting in increased capital and running costs of air-conditioning plant and reduced thermal comfort. A more accurate method of estimating peak small power equipment loads in UK office buildings is suggested based on occupant density.     

Influence of ventilation systems and related energy consumption on inhalable and respirable dust concentrations in fattening pigs confinement buildings

In this paper are presented the results of experimental analysis of the influence of ventilation systems and related energy consumption on inhalable and respirable dust concentrations in fattening pigs confinement buildings. The application of different under pressure ventilation systems in reducing and controlling dust concentrations was analyzed. Optimal ventilation systems designs and the ranges of airflow velocities were defined and discussed.Airflow velocities in the finishing room, under floor, roof and both ventilations, ranged from: 0.01 to 0.10, 0.01 to 0.10 and 0.02 to 0.10 m/s, respectively.The average inhalable dust concentrations during the reference regime (no ventilation), as well as second (floor-), third (roof-) and fourth (both ventilations) regime were: 20, 20, 25 and 17 particles/cm³, respectively. The average respirable dust concentrations during the reference regime, as well as second, third and fourth regime were: 18, 19, 23 and 16 particles/cm³, respectively.Significant decrements of inhalable (F = 44.35, P ≪ 0.01) and respirable (F = 43.82, P ≪ 0.01) dust concentration, in the finishing fattening pig house, were achieved only with the fourth regime (both ventilations).     

Study of a floor supply air conditioning system using granular phase change material to augment building mass thermal storage—Heat response in small scale experiments

We have proposed a new floor supply air conditioning system, using phase change material to augment building mass thermal storage. A scale model was constructed for such a system. Granules containing phase change material (PCM), with a phase change temperature of about 20 °C, were made from foamed glass beads and paraffin waxes. Results from measurements simulating an air conditioning schedule in office buildings indicate that 89% of daily cooling load could be stored each night in a system that used a 30 mm thick packed bed of the granular PCM.     

Prototype development of the rooftop turbine ventilator powered by hybrid wind and photovoltaic energy

In order to respond the suggestions made in the previous works, such as (1) improving the design of the rooftop ventilator commonly used in Taiwan, (2) making the “push–pull” airflow model in the ventilation duct effective for the bathroom ventilation and (3) combining the energy demands of the ventilator with renewable energy to reduce energy consumption, this study develops a prototype of the rooftop turbine ventilator powered by hybrid wind and photovoltaic energy. A low-speed wind tunnel experiment is performed to investigate the prototype's ventilation performance. The experimental results indicate installing an inner fan at low outdoor wind speed (0 and 5 m/s) increases the ventilation rate. The ventilation rate was not improved by installing an inner fan at a high outdoor wind speed. A rated rotation speed close to 1500 rpm is highly recommended when installing the inner fan. This study also introduces the general application modes of the proposed ventilator, and their electricity specifications.     

Numerical comparison of performance between traditional and alternative jet fans in tiled tunnel in emergency ventilation

In this paper a computational study was carried out to evaluate the performance of longitudinal ventilation system equipped with an alternative jet fan with respect to traditional one in case of fire in tiled tunnel. The alternative jet fan is equipped with inclined silencers (pitch angle α = 6°) in order to reduce the Coanda effect and consequently shear stress on the tunnel ceiling. The fire was simulated setting heat flux on HGV surface. Computational fluid dynamic analysis was applied to simulate the ventilation in the unidirectional tunnel through κ–ɛ model. The comparison conducted in terms of total thrust required to prevent back-layering phenomena and numerical results were provided in terms of thrust of jet fan values, average velocity values and temperature profiles, for different tunnel slope values. Furthermore the authors have compared the critical velocity provided by CFD analysis with critical velocity provided in the literature.     

Influence of traffic force on pollutant dispersion of CO,NO and particle matter (PM2.5) measured in an urban tunnel in Changsha,China

Environmental safety issues and ventilation problems caused by the construction of urban tunnel have increasingly been attracting people’s attention. Previous studies in China have mainly focused on vehicle emissions and ventilation control technologies in road tunnels, resulting in a research gap on urban tunnel ventilation engineering design. Therefore, a detailed monitoring investigation was conducted from May 22 to June 2, 2013 in Changsha Yingpan Road Tunnel, China. The study aim was to measure the traffic characteristics, air velocity and the carbon monoxide (CO), nitrogen oxides (NO_x) and fine particulate matter (PM_2.5) concentrations in this tunnel, which has two lanes per bore and multiple ramps. Measurement results show that during the workday morning peak, the maximum traffic flow was 1560 passenger-car-unit/h per lane with vehicle speed around 33.6 km/h in the eastbound tunnel, the average air velocity was 3.07 m/s, and the proportion of the light-duty vehicles (LDV) was 97.3%. Under the traffic force (not open fan), the CO and NO average concentrations at the main tunnel outlet were 20.3 ppm and 1.65 ppm, respectively. The gas pollutant concentrations are effectively controlled within the multiple-ramps tunnel and the design air volume flow is noticeably reduced. The traffic air flow was found to provide 32.5% of the required air volume to dilute NO_x in blocked traffic condition (vehicle speed of 10 km/h). In addition, the PM_2.5 concentration is mainly affected by the value of background outside the tunnel. The result can provide a quantitative assessment method to support pollutant concentration control and contribution of requested air volume by traffic flow in urban complex structure tunnel.     

Virtual in-situ calibration method in building systems

Sensors play an important role in guiding building systems to achieve desired operation and efficiency. However, sensors are subject to continuous degradation and failures over time. Although a periodical calibration is needed, it is exceptionally difficult and/or impractical to many sensors with a conventional manual approach. Uncalibrated problematic sensors could significantly compromise the systems' performance and lead to unintended loss of energy efficiency in buildings. We propose a methodology, termed virtual in-situ calibration, to solve this critical issue. It is developed by mathematically extracting the characteristics of essential aspects involved in a calibration, including the environment assessment, benchmark establishment, and uncertainty quantification. A case study of a supply air temperature sensor in rooftop units illustrates the implementation process; the erratic uncertainty is reduced from ± 19.2 °C to ± 0.7 °C after the virtual in-situ calibration. The calibration method can be implemented online to significantly improve the reliability of sensor networks in buildings.     

Space temperature difference,cooling coil and fan—energy and indoor air quality issues revisited

In designing an energy-efficient air-conditioning system that also simultaneously addresses the needs of adequate ventilation and acceptable indoor air quality, several factors begin to play an important role. Among several others, the cooling coil, the fan and the temperature difference between the space and the supply air (commonly known as the Space ΔT) can be considered to be crucial. For a given space cooling load, the choice of a particular Space ΔT has an implication on the amount of supply air required, which further has an impact on the performance of the cooling and dehumidifying coil as well as the fan. Inherent in these implications are issues related to energy, ventilation and indoor air quality. This paper investigates these implications and quantifies them by considering a hypothetical building in a tropical climate and subjecting the design to several parametric variations involving different Space ΔTs for a given space temperature and humidity condition. The total power requirements, comprising additional cooling, reheating and higher fan power, for a design involving a Space ΔT of 5 °C can be as high as a factor of 2.2 of the total power for a design with a Space ΔT of 8 °C. The implication of higher supply air flow rates on duct design is qualitatively discussed. For a given space cooling load and a given Space ΔT, the implication of increased design ventilation rates to address part-load ventilation requirements can lead to an additional installed cooling capacity of 17.5%. Finally, emerging technologies that are aimed at addressing both energy efficiency and IAQ are discussed.     

Life cycle assessment of residential ventilation units in a cold climate

The life cycle assessment (LCA) methodology is used in this paper to assess the environmental impacts of residential ventilation units over a 50 year life cycle in Finland. Quantifying the consumption of the energy and material resources during the life cycle permits the estimation of the harmful emissions into the environment (air, water and soil) and the potential changes in the environment (climate change, acidification and ozone production). Two different ventilation units are evaluated, both of which include air-to-air energy exchangers. The research demonstrates that a residential ventilation unit, with a function of providing 50 l/s of outdoor ventilation air, but not heating the air, has a net positive impact on the environment when it is equipped with a air-to-air energy exchanger with an effectiveness greater than 15%. The greater the effectiveness, the greater the positive impact on the environment.     

Modelling sheltering effects of trees on reducing space heating in office buildings in a windy city

Using statistical weather analysis, computational fluid dynamics and thermal dynamic simulation, a systematic method was developed to assess quantitatively the effects of a shelterbelt on space heating, particularly with regard to the energy consumption and CO₂ emission. It was then applied to estimate the heating loads of two typical office buildings in a windy city located at 57.2North, with and without a shelterbelt. Firstly, the statistical analysis of weather data was carried out to identify the prevailing wind direction during a typical winter heating season in the location. It was to ensure the windbreak planted rightly to maximise its sheltering benefits for the buildings in its leeward. This analysis, which revealed the main weather features in the location, would help to better comprehend the results of the thermal modelling and gain insight of how the load responses to the climate. In the second part, CFD modelling predicted wind reduction due to the shelterbelt under various wind directions. The predicted data were then used to prepare two sets of weather data, the original weather file and the revised one, in which the wind data had taken into account the reduction effect of the windbreak. The third part was a dynamic thermal modelling study where two types of office buildings were selected as the representative offices in Edinburgh for the assessment of sheltering effect on energy saving and CO₂ reduction. The predicted savings over a heating season due to the shelterbelt were in a range of 16–42% and the actual values in space heating were about 2.2 kWh m⁻² for new office buildings and 14.5 kWh m⁻² for offices converted from conventional houses without insulation improvement. These significant savings were due to the local weather that is typically known as long windy winter with many cloudy days.     

Influence of thermal insulation position in building envelope on the space cooling of high-rise residential buildings in Hong Kong

At the present time, thermal insulation is almost not used in fabric of tall residential buildings in Hong Kong, as their fabric slabs usually comprise concrete layer covered on each side by plaster layers. This study investigates into the influence of an existence of the thermal insulation layer in the outside walls on the yearly cooling load and yearly maximum cooling demand in two typical residential flats in a high-rise residential building by employing HTB2, detailed building heat transfer simulation software. During the investigations, the thermal insulation layer up to 15 cm thick was placed either at the inside, or at the outside, or at the middle part of the outside wall structure. Then, the concrete layer was up to 40 cm thick. The simulation predictions indicate that the highest decrease in the yearly cooling load of up to 6.8% is obtained when a 5 cm thick thermal insulation layer faces the inside of the residential flat. The highest decrease in the yearly maximum cooling demand of 7.3% is recorded when a 5 cm thermal insulation layer faces either the outside or the inside of the flat; this depends on the flat orientation. However, much weaker reductions in the yearly cooling load and yearly maximum cooling demand are found when the thickness of thermal insulation is increased above 5 cm and the thickness of concrete is increased above 10 cm.     

Electricity savings from implementation of minimum energy efficiency standard for TVs in Malaysia

The popularization of 24 h pay-TV, interactive video games, web-TV, VCD and DVD in Malaysia are poised to have a large impact on overall TV electricity consumption in the country. With the increasing of overall TV energy consumption, energy efficiency standards are one of highly effective policies for decreasing electricity consumption in the residential sector. Energy efficiency standards are also capable of reducing consumer's electricity bill and contribute towards positive environmental impacts. This paper attempts to predict the amount of energy that can be saved in the residential sector by implementing minimum energy efficiency standard for television sets in Malaysia. Over the past 30 years, television ownership in Malaysian residents has increased from 186,036 units in 1970 to 2,741,640 units in 1991. This figure is expected to reach 6,201,316 units in the year 2010. Hence, efficiency improvement for this appliance will have a significant impact on the future of electricity consumption in this country.     

Full-scale experiment and CFD simulation on smoke movement and smoke control in a metro tunnel with one opening portal

Three full-scale model experiments were conducted in a unidirectional tube, which is a part of a metro tunnel with one end connected to an underground metro station and the other end opened to outside in Chongqing, PR China. Three fire HRRs, 1.35 MW, 3 MW and 3.8 MW were produced by pool fires with different oil pan sizes in the experiments. Temperature distributions under the tunnel ceiling along the longitudinal direction were measured. At the same time, CFD simulations were conducted under the same boundary conditions with the experiments by FDS 5.5. In addition, more FDS simulation cases were conducted after the FDS simulation results agreed with the experimental results. The simulation results show that the smoke temperature and the decay rate of the temperature distribution under the tunnel ceiling along the longitudinal direction increase as HRR increases. The smoke exhausts effectively from the tunnel under mechanical ventilation system, whether the emergency vent is activated as a smoke exhaust or an air supply vent. The operation mode of the mechanical ventilation system depends on the evacuation route.     

Climate change impacts on building heating and cooling energy demand in Switzerland

The potential impacts of climate change on heating and cooling energy demand were investigated by means of transient building energy simulations and hourly weather data scenarios for the Zurich–Kloten location, which is representative for the climatic situation in the Swiss Central Plateau. A multistory building with varying thermal insulation levels and internal heat gains, and a fixed window area fraction of 30% was considered. For the time horizon 2050–2100, a climatic warm reference year scenario was used that foresees a 4.4 °C rise in mean annual air temperature relative to the 1961–1990 climatological normals and is thereby roughly in line with the climate change predictions made by the Intergovernmental Panel on Climate Change (IPCC). The calculation results show a 33–44% decrease in the annual heating energy demand for Swiss residential buildings for the period 2050–2100. The annual cooling energy demand for office buildings with internal heat gains of 20–30 W/m² will increase by 223–1050% while the heating energy demand will fall by 36–58%. A shortening of the heating season by up to 53 days can be observed. The study shows that efficient solar protection and night ventilation strategies capable of keeping indoor air temperatures within an acceptable comfort range and obviating the need for cooling plant are set to become a crucial building design issue.     

An empirical radon emanation model for residential premises

Based on an averaging technique, a methodology has been established to estimate an effective radon emanation factor M for residential premises. The model shows that the new term M and the ventilation rate are the essential parameters in estimating the level of indoor radon. M includes two components: the radon emanation rates of internal surface materials and the ratio of surface areas of applicable materials to premises volume. The value of M can be determined from on-site measurements. Different ventilation modes of a sampled residential unit during daytime and nighttime, with air conditioner on, window-open, and window-closed were included in site measurements. Each ventilation mode was measured twice during daytime and twice at night. During the investigation, air exchange rate, and indoor and outdoor radon levels were monitored simultaneously. The results of measurements were then used to verify the model. The value of M was found to be 31.7 Bq m⁻³ h⁻¹. The model is valid if the air exchange rate is larger than 0.2 h⁻¹.     

Thermodynamic analysis of a building using exergy analysis method

This study deals with exergetic assessment of an educational building heated by a conventional boiler in a heating center. The heating system is examined from the generation stage to the envelope of the building. In general the heat loss calculations are made using both energy and exergy analysis methods. The energy and exergy flows between the stages are obtained using a pre-design tool for an optimized building design. Energy and exergy losses are obtained to evaluate the performance of the system. A conventional boiler in the heating center and a fan coil unit in a room are considered in the analysis. Total exergy input rate is calculated to be 694.5 kW, while the largest exergy loss rate is obtained to be 333 kW. Exergetic efficiencies of the conventional boiler and the fan coil unit are also found to be 13.4% and 37.6%, respectively.     

Evaluation of indoor environmental quality conditions in elementary schools׳ classrooms in the United Arab Emirates

This study presents findings of indoor environmental quality (IEQ) investigations conducted in elementary schools׳ classrooms in the United Arab Emirates (UAE). Average TVOC, CO₂, O₃, CO, and particle concentrations measured in the classrooms were 815 µg/m³, 1605 ppm, 0.05 ppm, 1.16 ppm, and 1730 µg/m³, respectively. Whereas, local authority known as Dubai Municipality recommended 300 µg/m³, 800 ppm, 0.06 ppm, 9 ppm, and 150–300 µg/m³ for TVOC, CO₂, O₃, CO, and particle, respectively. Dubai Municipality recommended temperature and relative humidity (RH) levels of 22.5 °C to 25.5 °C and 30%–60%, respectively. Average temperature and RH levels measured in the classrooms were 24.5 °C and 40.4%, respectively. Average sound level in the classrooms was 24 dB greater than recommended sound level limit of 35 dB. Six (6) classrooms had average lux levels in the range of 400–800 lux. Two (2) classrooms had average lux levels in the range of 100–200 lux. The remaining classrooms had lux levels around the recommended 300 lux. High occupancy density was observed in majority of the studied classrooms. Observations during walkthrough investigations could be used to explain measured IEQ data. Poor IEQ conditions in the studied classrooms highlight the need for further research investigation to understand how poor classrooms׳ IEQ condition could influence students׳ health, comfort, attendance rate, and academic performance.