The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Hsiang Lun Chen - One of the best experts on this subject based on the ideXlab platform.
-
Analysis of energy saving potential of air-side free cooling for data centers in worldwide climate zones
Energy and Buildings, 2013Co-Authors: Hsiang Lun ChenAbstract:Abstract Based on the climate classification of ASHRAE 90.1 and the required operating environment conditions for data centers suggested by the ASHRAE Technical Committee TC 9.9, a dynamic building energy simulation program was used to examine the potential energy savings of the air-side free cooling technology with differential enthalpy control used in data centers in 17 climate zones. The results showed that significant free cooling potential was achieved in data centers located in mixed-humid, warm-marine, and mixed-marine climate zones. Because significant humidification is required to adjust outdoor air in climate zones with a lower dew point temperature, such as very-cold, subarctic, cool-dry, and cold-dry climate zones, the power consumed is even higher. Although the cooling Degree Day (CDD) and Heating Degree Day (HDD) are key factors of climate classification and air conditioning energy consumption, they are not entirely correlated to the specific operating environment conditions of data centers. The results of this study showed that for every 2 °C decline in the indoor temperature of a data center, the energy saving of free cooling technology may decrease by 2.8–8.5%. The rate of decline varies in different climate zones.
-
Analysis of energy saving potential of air-side free cooling for data centers in worldwide climate zones
Energy and Buildings, 2013Co-Authors: Kuei Peng Lee, Hsiang Lun ChenAbstract:Based on the climate classification of ASHRAE 90.1 and the required operating environment conditions for data centers suggested by the ASHRAE Technical Committee TC 9.9, a dynamic building energy simulation program was used to examine the potential energy savings of the air-side free cooling technology with differential enthalpy control used in data centers in 17 climate zones. The results showed that significant free cooling potential was achieved in data centers located in mixed-humid, warm-marine, and mixed-marine climate zones. Because significant humidification is required to adjust outdoor air in climate zones with a lower dew point temperature, such as very-cold, subarctic, cool-dry, and cold-dry climate zones, the power consumed is even higher. Although the cooling Degree Day (CDD) and Heating Degree Day (HDD) are key factors of climate classification and air conditioning energy consumption, they are not entirely correlated to the specific operating environment conditions of data centers. The results of this study showed that for every 2 C decline in the indoor temperature of a data center, the energy saving of free cooling technology may decrease by 2.8-8.5%. The rate of decline varies in different climate zones. © 2013 Elsevier B.V. All rights reserved.
James A. Voogt - One of the best experts on this subject based on the ideXlab platform.
-
Impacts of urban albedo increase on local air temperature at daily-annual time scales: Model results and synthesis of previous work
Journal of Applied Meteorology and Climatology, 2010Co-Authors: E. Scott Krayenhoff, James A. VoogtAbstract:Abstract The authors combine urban and soil?vegetation surface parameterization schemes with one-dimensional (1D) boundary layer mixing and radiation parameterizations to estimate the maximum impact of increased surface albedo on urban air temperatures. The combined model is evaluated with measurements from an urban neighborhood in Basel, Switzerland, and the importance of surface?atmosphere model coupling is demonstrated. Impacts of extensive albedo increases in two Chicago, Illinois, neighborhoods are modeled. Clear-sky summertime reductions of diurnal maximum air temperature for the residential neighborhood (?p = 0.33) are ?1.1°, ?1.5°, and ?3.6°C for uniform roof albedo increases of 0.19, 0.26, and 0.59, respectively; reductions are about 40% larger for the downtown core (?p = 0.53). Realistic impacts will be smaller because the 1D modeling approach ignores advection; a lake-breeze scenario is modeled and temperature reductions decline by 80%. Assuming no advection, the analysis is extended to seasonal and annual time scales in the residential neighborhood. Yearly average temperature decreases for a 0.59 roof albedo increase are about ?1°C, with summer (winter) reductions about 60% larger (smaller). Annual cooling Degree-Day decreases are approximately offset by Heating Degree-Day increases and the frequency of very hot Days is reduced. Despite the variability of modeling approaches and scenarios in the literature, a consistent range of air temperature sensitivity to albedo is emerging; a 0.10 average increase in neighborhood albedo (a 0.40 roof albedo increase for ?p = 0.25) generates a diurnal maximum air temperature reduction of approximately 0.5°C for ?ideal? conditions, that is, a typical clear-sky midlatitude summer Day.
-
Impacts of Urban Albedo Increase on Local Air Temperature at Daily – Annual Time Scales : Model Results and Synthesis of Previous Work
Journal of Applied Meteorology and Climatology, 2010Co-Authors: Scott Krayenhoff, E, James A. VoogtAbstract:The authors combine urban and soil–vegetation surface parameterization schemes with one-dimensional (1D) boundary layer mixing and radiation parameterizations to estimate the maximum impact of increased surface albedo on urban air temperatures. The combined model is evaluated with measurements from an urban neighborhood in Basel, Switzerland, and the importance of surface–atmosphere model coupling is demonstrated. Impacts of extensive albedo increases in two Chicago, Illinois, neighborhoods are modeled. Clear-sky summertime reductions of diurnal maximum air temperature for the residential neighborhood (lp 5 0.33) are 21.18, 21.58, and 23.68C for uniform roof albedo increases of 0.19, 0.26, and 0.59, respectively; reductions are about 40% larger for the downtown core (lp 5 0.53). Realistic impacts will be smaller because the 1D modeling approach ignores advection; a lake-breeze scenario is modeled and temperature reductions decline by 80%. Assuming no advection, the analysis is extended to seasonal and annual time scales in the residential neighborhood. Yearly average temperature decreases for a 0.59 roof albedo increase are about 218C, with summer (winter) reductions about 60% larger (smaller). Annual cooling Degree-Day decreases are approximately offset by Heating Degree-Day increases and the frequency of very hot Days is reduced. Despite the variability of modeling approaches and scenarios in the literature, a consistent range of air temperature sensitivity to albedo is emerging; a 0.10 average increase in neighborhood albedo (a 0.40 roof albedo increase for lp 5 0.25) generates a diurnal maximum air temperature reduction of approximately 0.58C for ‘‘ideal’’ conditions, that is, a typical clear-sky midlatitude summer Day.
Kuei Peng Lee - One of the best experts on this subject based on the ideXlab platform.
-
Analysis of energy saving potential of air-side free cooling for data centers in worldwide climate zones
Energy and Buildings, 2013Co-Authors: Kuei Peng Lee, Hsiang Lun ChenAbstract:Based on the climate classification of ASHRAE 90.1 and the required operating environment conditions for data centers suggested by the ASHRAE Technical Committee TC 9.9, a dynamic building energy simulation program was used to examine the potential energy savings of the air-side free cooling technology with differential enthalpy control used in data centers in 17 climate zones. The results showed that significant free cooling potential was achieved in data centers located in mixed-humid, warm-marine, and mixed-marine climate zones. Because significant humidification is required to adjust outdoor air in climate zones with a lower dew point temperature, such as very-cold, subarctic, cool-dry, and cold-dry climate zones, the power consumed is even higher. Although the cooling Degree Day (CDD) and Heating Degree Day (HDD) are key factors of climate classification and air conditioning energy consumption, they are not entirely correlated to the specific operating environment conditions of data centers. The results of this study showed that for every 2 C decline in the indoor temperature of a data center, the energy saving of free cooling technology may decrease by 2.8-8.5%. The rate of decline varies in different climate zones. © 2013 Elsevier B.V. All rights reserved.
Zekai Sen - One of the best experts on this subject based on the ideXlab platform.
-
Variations and trends in turkish seasonal Heating and cooling Degree-Days
Climatic Change, 2001Co-Authors: Mikdat Kadiolu, Zekai Sen, Latif GültekinAbstract:The potential effect of climate change on energy demand is important especially for the developing and non-oil-producing countries. Cooling and Heating Degree-Day (CDD and HDD) concepts are among the most significant meteorological variables related to residential energy consumption. This paper presents the spatial and temporal characteristics of Turkish seasonal CDD and HDD in the context of climate change. CDD and HDD are defined objectively by truncation of the temperature series at any constant base temperature level. This leads to surpluses and deficits as deviations. The surpluses are instances for cooling and the deficits for Heating. Depending on temperature fluctuations, the Degree-Day statistics at any location show local and seasonal variations. In this study, regional variations of seasonal HDD and CDD are mapped for Turkey and their relations to local topography and climatic features are examined with conclusive interpretations. The sequential version of Mann-Kendall rank statistic is applied to demonstrate any existence of possible non-linear trends in accumulated HDD and CDD over the seasons. Spatially coherent and statistically significant trends of HDD and CDD appear in some regions of Turkey. In general, the sign of the trends is inconsistent with General Circulation Models (GCM) predictions
-
Theoretical risk formulation for Degree-Day calculations
Theoretical and Applied Climatology, 1998Co-Authors: Zekai Sen, Mikdat KadioǧluAbstract:Energy consumption, agricultural activities and comfort in building design are all related to temporal temperature variations. Truncation of the temperature series at a constant base temperature level leads to surpluses and deficits as deviations. Surpluses are instances for cooling and deficits for Heating. In meteorology and heat engineering these are referred to as cooling and Heating Degree-Days, respectively. Since the temperature records are random in character their future predictions are necessary through statistical and probabilistic methods. In this paper, the Degree-Days are assumed to have a normal probability distribution function and therefore, their averages and standard deviations are considered sufficient for modeling cooling and Heating Degree-Day amounts. Theoretical derivations are presented for Degree-Day risk calculations in their general forms and a simple implementation is given for two cities in Turkey.
Gh R. Roshan - One of the best experts on this subject based on the ideXlab platform.
-
Determining new threshold temperatures for cooling and Heating Degree Day index of different climatic zones of Iran
Renewable Energy, 2017Co-Authors: Gh R. Roshan, A. A. Ghanghermeh, Sonia AttiaAbstract:Iran is a country with a variety of different climates. Determining the threshold temperatures suitable for providing thermal and climatic comfort is necessary and vital to its population well-being. This research presents new threshold temperatures in order to calculate the Degree Day index required for Heating and cooling by taking advantage of the 12 stations that are representative of the diversity of Iran's climate. Using Olgyay diagram, different bioclimatic ranges of 12 weather stations and their frequencies were compiled, processes and analysed. Mean daily data of temperature and relative humidity were used for the period of 1950–2010. Based on the frequencies of temperature readings falling in Olgyay's diagram comfort zone, representive temperature thresholds were selected based on 40 to 60 percentiles or (P20), 25–75% percentile (P50) and the threshold of 10–90% percentile. The findings of this study shows that Mashhad with 29.6% and Anzali with 2.33% of frequencies, have experienced the maximum and minimum Days of comfort. After analyzing various percentiles to determine the threshold temperatures, it was observed that there is a little difference among the stations for determining the minimum threshold for the comfort. Differences are more obvious in the maximum thresholds. In total, minimum base temperatures (HDD) belonged to Ardabil stations that were 20.50, 20.90 and 20 deg C for P20, P50 and P80 respectively. The maximum temperature for calculating CDD with values of (P20 = 25 °C; P50 = 26.25 °C; P80 = 27.50 °C) is dedicated to Zabol station. The findings present more reasonable thermal comfort thresholds that can be used by architects, engineers and policy makers to achieve, in turn, more energy efficient homes and high quality indoor and outdoor living environments.
-
The impacts of drying of Lake Urmia on changes of Degree Day index of the surrounding cities by meteorological modelling
Environmental Earth Sciences, 2016Co-Authors: Gh R. Roshan, Jafar Masoompour Samakosh, José A. OrosaAbstract:The Lake Urmia, the largest lake in Iran and the second largest saline lake in the world, is currently faced with the threat of drying up. In the last two years, it experienced an increase in its water level, leading researchers to compare different situations. In this study, using The Air Pollution Modelling software, two scenarios, one of the lake being full of water and another of the dry lake, were projected in order to simulate changes in energy demand for four cities located in the neighbourhood of the lake. The main results, based on a dry lake scenario, showed a decrease in weather temperature during the cold season and an increase during the hot season, particularly in the Day time, in respect of a full level of water in the lake. Because of this, there was an increase in energy demand for cooling Degree Day (CDD) for daily hours of the hot months and for Heating Degree Day (HDD) demand in the night hours of the cold months. In particular, the overall average annual increase for HDD and CDD in the entire studied area will increase to 140.56° and 105.90° by Day, respectively. At the same time, a significant variation of relative humidity in contraposition to temperature will occur; therefore, the thermal comfort conditions of the studied cities are expected to be worse. Finally, future research works must be done to predict the expected energy consumption in the next decades in accordance with the procedure developed.
-
The impacts of drying of Lake Urmia on changes of Degree Day index of the surrounding cities by meteorological modelling
Environmental Earth Sciences, 2016Co-Authors: Gh R. Roshan, Jafar Masoompour Samakosh, José A. OrosaAbstract:© 2016, Springer-Verlag Berlin Heidelberg. The Lake Urmia, the largest lake in Iran and the second largest saline lake in the world, is currently faced with the threat of drying up. In the last two years, it experienced an increase in its water level, leading researchers to compare different situations. In this study, using The Air Pollution Modelling software, two scenarios, one of the lake being full of water and another of the dry lake, were projected in order to simulate changes in energy demand for four cities located in the neighbourhood of the lake. The main results, based on a dry lake scenario, showed a decrease in weather temperature during the cold season and an increase during the hot season, particularly in the Day time, in respect of a full level of water in the lake. Because of this, there was an increase in energy demand for cooling Degree Day (CDD) for daily hours of the hot months and for Heating Degree Day (HDD) demand in the night hours of the cold months. In particular, the overall average annual increase for HDD and CDD in the entire studied area will increase to 140.56° and 105.90° by Day, respectively. At the same time, a significant variation of relative humidity in contraposition to temperature will occur; therefore, the thermal comfort conditions of the studied cities are expected to be worse. Finally, future research works must be done to predict the expected energy consumption in the next decades in accordance with the procedure developed.
-
Climate change and its role in forecasting energy demand in buildings: A case study of Douala City, Cameroon
Journal of Earth System Science, 2015Co-Authors: Modeste Kameni Nematchoua, Gh R. Roshan, Touraj Nasrabadi, Rene Tchinda, Paola RicciardiAbstract:The foremost role of a building is to assure the comfort of its occupants. The thermal comfort of a building depends on the outdoor climate and requires a demand in energy for Heating and cooling. In this paper, demand of energy (Heating/cooling) in the buildings is discussed in Douala, Cameroon. Daily data of the last 40 years coming from five weather stations of Cameroon have been studied. Some forecasts have been carried out with 14 GCM models, associated to three future climate scenarios B1, A2, and A1B. However, only INCM3 of General Circulation Model (GCM) and A2 scenario was used. Energy demand in buildings is valued by HDD (Heating Degree Day) and CDD (cooling Degree Day) indices. Obtained results show that the temperature evolves more quickly in dry season than in rainy season in Douala. Climate rise indicates an increasing demand of energy in the buildings for cooling. Global Douala Heating shows a definite effect on outdoor comfort. From 2045 to 2075, the demand of energy for cooling will be superior to 50%. The total demand in energy for Heating in the buildings is estimated to be 67.882 kcal from 1970 to 2000 and will be around 67.774 kcal from 2013 to 2043.