Energy Efficiency Analyses through Ground Thermal Capacitor System- Case Studies: Two Sustainable Buildings in Vienna and Tehran

¹MOHAMMAD TAGHI REZAEI HARIRI, ²MOHAMMAD RAJABPOUR, ³AHADOLLAH AZAMI,

4FATEMEH AKBARISANI Department of Architecture

1Tehran University, 2Islamic Azad University-Azarshahr, 3Eastern Mediterranean University, 4Islamic Azad University-Jolfa International Branch Famagusta T.R. North Cyprus via Mersin 10, Turkey

¹,2,4Turkey, 3Iran ¹ irsesta@yahoo.com, 2rajabpoor_m@yahoo.com, ³ahadollah.azami@emu.edu.tr,

4Tamanna.Matrix@yahoo.com

Abstract: - One of the strategies in sustainable architecture regarding energy concerns using natural heat stored in the ground in the form of thermal capacitor, which can be applied for; a) passive systems equipped with sustainable architectural provisions and b) active systems equipped with thermal machines. Since the temperature of the earth – as the thermal capacitor – is much higher than the external temperature in winter (suitable for modifying heating in internal spaces), and also much lower than the external temperature in summer (suitable for cooling, modifying and ventilating internal spaces), two different types of buildings as case studies: firstly, Central Saving Bank of Vienna in Tabour district; Austria and secondly convalescence building in Lahijan, Iran that used ground thermal storage capacitor analyses for energy efficiency. In Iranian case, a capacitor with an approximate height of 1.5 meters is designed and operated on the under-ground fifth floor as well as the floor under the installations level; therefore considering issue mentioned above and intelligent combination of cooling system design with passive dehydrating systems of Iran’s traditional wind catchers this project can conserve energy consumption up to 76%. Key-Words: - Sustainable Architecture, Ground Thermal Capacitor, Solar Energy, Energy Efficiency 1 Introduction Iranian former architects in every region of cold and dry, hot and dry, mild and humid, hot and humid were best profited of the passive solar systems with their experience. They have learned over the long period of years in action how to and adapt materials, from and region and how to use them extremely in arranging of environmental condition, human settlements [1]. One of those cases is using of the ground thermal in the form of thermal storage which has been used in our traditional architecture with combining of a wind catcher which cools and moistens the air of living spaces in hot and dry regions, and in summers, on the other hand, it takes the moisture of the air and in hot and moist regions and causes to run the cool and dry air inside the spaces. This style was built for the first time in 1980 in Austriain the bank of Tabour District in Vienna. The following is one of the other examples that model which we try to explain it. 2 General Principles When we talk about the economizing in energy consumption at first people think about the consumption of fossilized and endless energy. In fact, the most

effective result of energy economizing in building is possible through the thermal insulation of buildings for example in energy consumption in a residential building if it has a suitable thermal insulation, it will economize about 20 to 50 percent in energy consumption. The other effective factor in energy efficiency is using the existent heating around the buildings that need more energy in winters, but they use less energy in summers. Until now, human could not have obtained the artificial thermal storage which can save necessary and extra energy to use in summer. The earth naturally is a big thermal storage to (keep extra energy of summer to use in winter) which is under the buildings, yards, streets, and city squares and they are easily accessible for people. The temperature under the floor of building’s basement is usually 3˚C to 4˚C above the average number of annual heating in every regions (about 14˚C) and in open spaces beyond the under buildings of the floor of the basement, it is about 1˚C more than average of annual heating (about 11˚C) [2]. The temperature on the underground waters is extremely equal with the average temperature and it is about 9˚C. Therefore, it is clear that the earth temperature (like thermal storage in winter is extremely above the air temperature in the same season and in fact in order to

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improve and use the temperature of inside of buildings and economizing energy consumption. Meanwhile in the same way in summers, the temperature of the earth also is so below from the temperature in this season and in cool and balance that the air of the inside of a building . We can use the saved energy in the ground (thermal storage) according the followings: a) In the form of the passive systems by architectural anticipation and adapting it with the environment, b) In the form of active systems by thermal machines [3]. 3 Location of Ground Thermal Storage In general, the possible using of thermal storage in relation to the buildings, and in places such: a) Under the building and b) in the basements around the buildings are more important in talking thermal energy in winter and cooling in summer. Other cases and the points that should be considered in thermal storage patterns are as follows: In normal buildings, in case the thermal storage for using in winter, because under the buildings the temperature is more than the one around the buildings and it is better to use from the ground of the under floor for this purpose. Only if the building is high and the volume of the spaces is increasing and if the amount of area which involving the building under the ground for taking the energy is not enough we should consider the thermal storage more than the spaces of building situation and in fact in this case, the thermal storage expands around the building. If the thermal storage is used for building cooling, it will be better to continue of the restricted area of thermal storage from the building space towards the green spaces (which has more moisture due to the great watering) if not so, it remains under the basement floor [4]. Figure 1 show how thermal storage under the building connected to fresh air channel. Figure 2 shows the relation of a thermal storage to a ventilation which use the consumed heating in a building, conveys the temperature of the fresh air as soon as possible till the temperature of the necessary air into the building. In this case, first the temperature of the fresh air through the thermal transformed increases in storage till it reaches itself about the necessary temperature inside the spaces besides the obtained heating of using the air of the building. 4 Specification of a Thermal Storage in Central Saving Bank of Vienna The first thermal storage was used according to the above, in 1980 in one of the central saving bank of Vienna branches located in Tabour Street (figure 3).

Because of considerable demension, using mechanical installations in this building is inevitable. Mechanical installation channel system is used for

ventilation, aeration, heating and cooling of bank counter saloon. For hygiene reasons, the ratio of fresh air and working space- 40m3 /hour for each person- is considerable figure and heating and cooling of this location require to considerable energy in the summer and winter. According to figure 4, the required energy for cooling of the internal specs in the summer has been saved.

Fig.1: Fresh and consumed air mechanical system with air preheating by thermal exchanger, Bank of Vienna, Austria. In the parking under ground, thermal capacitor –thermal exchange surface- equals to building occupation surface and it responds to required air thermal adjustment for cooling and heating of the building. Suctioned air from roof is filtered and it enters to thermal capacitor divider channel under parking floor by downstream channel. This air is suctioned slowly and uniformly by air divider Chanel in all thermal capacitor space and contacted by thermal surface (ground).The fresh air is exchanged by ground surface by this mechanism and it transferred to internal spaces by air collector channels toward air transferring channels [5]. Advantages of this system are: a) Ground heat is transferred to fresh air and it increases the temperature in the winter, b) Contact between the fresh air and ground reduces air heat and coordinates its temperature in the summer, c) Since the temperature of the ground thermal capacitor surface is less than entered fresh air in humid days, the entered air reduces its

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relative humidity because of cooling and this moisture is removed from fresh air as evaporation and remains in cold surface –thermal capacitor.

Fig.2: Fresh and consumed air mechanical system with air preheating by ground thermal capacitor and using consumed air temperature for providing hot water, Central Saving Bank of Vienna, Austria. Because of wet thermal capacitor surface and dryness of entered fresh air in dry days, this air receives proportionate humidity from thermal capacitor surface and enters in building inner space and provides optimal condition (Figure1). Effect of thermal exchange of ground capacitor in the winter depends on air temperature in the different times of the season: a) fresh air temperature and b) fresh air temperature after thermal capacitor and d) building inside air temperature. Figure4 shows performance of ground thermal capacitor from heating to cooling in April and May. In late of hot season in April the temperature indicates it sudden changes and in this time the thermal capacitor shows the optimal performance. In this case, in the bank salon the inside channel inlet temperature (from 29˚C) reaches to 17˚C to 19˚C after passing thermal capacitor. Beside entered fresh air cooling, the thermal capacitor shows other performance. So, the humidity percentage is increased and the air becomes wet by increase of fresh air temperature. The entered air is evaporated in 1 to 5gr/m3 inside thermal capacitor and approximately dry air enters the bank saloon. Figure 4 indicates this phenomenon.

Fig.3: Indicates daily and fresh air after passing thermal capacitor and inner temperature in January and February in 1981, Bank of Vienna, Austria.

Fig.4: Shows daily and fresh temperature after passing thermal capacitor and changes of humidity percentage in April and May in 1981, Central Saving Bank of Vienna, Austria. Space heating cost effective temperatures in the winter and cooling of early warm days of the summer are compared in figure 5.This diagram shows that the thermal capacitor preheats external fresh air to 15˚C and the thermal capacitor cooling is effective when the external temperature reaches to 18˚C. In this building the adjustment of the salon air temperature is 2˚C to 10˚C relative to entered fresh air temperature. It should be pointed that by increasing external temperature, the thermal capacitor becomes effective. The calculation of manufacturing of thermal capacitor cost (by cost of 150 Euro) for establishment of each square meter compared with required cost for production of the same building cooling and heating energy is considered. We find that the effect of the thermal capacitor during 6 to 7 years as reduction of fuel consumption and consumed energy compensates the establishment cost and in the next years savings of the fuel and energy will be considerable.

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According to increase of fuel materials and energy cost in today, the thermal capacitor cost depreciation will be done in short time.

Fig.5: Measurement Results of Air Heating & Cooling in Ground Thermal Capacitor, Central Saving Bank of Vienna, Austria.

Fig.6: Section view of internal space of the bank branches counters predicted by ample fresh air.

Fig.7: Thermal capacitor plan, Central Saving Bank of Vienna, Austria. 5 Introduction of Other Case in Iran Convalescence building with 25 beds in Lahijan Shahid Ansari hospital has a thermal capacitor for providing following facilities and meeting needs: a) Providing optimal air and control of air in different spaces of the buildings by important public and special aspects related to health spaces performance b) Need to more than ordinary exchange of health space air that increases energy consumption of the ventilation installations c) Establishment of underground proper direction relative to sun exposure ,ceiled terrace that limits sun radiation in the summer and allow entering of sun rays in inner spaces ,using louver in desert regions that were common in old Iranian buildings that natural energies were used effectively. d) Winter cold and sun irradiation energy in the summer penetrate in different layers of the ground .So, underground space is cool in the summer and it is warm in the winter relative to outside [6] .Thus this phenomenon can be used for moderation of inner spaces to reach energy efficiency by 76% both in summer and winter. Meanwhile the capacity of the ventilation systems as main energy consumer is reduced.

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5.2 Primary Ideas for the Design Expensiveness and fuel shortage, environment pollution because of using fossil fuels, proper project site and building type are the main deterministic factors in using thermal capacitor in the country calculation organization building. In this case, it was tried to consider the best place for thermal capacitor in order to reduce fuel consumption and energy saving inanition to using the best and complete cooling and heating installations. In other words by using thermal capacitor: a) Cooling and heating systems work are reduced and these systems depreciation is minimized. b) Fuel consumption (gasoline, gas and electricity) is reduced. c) Gases resulted from burning fissile are reduced and as a result pollution is reduced. d) According to calculations, using ventilation system is unnecessary in some days of a year and number of these days in this building is more other buildings e) There is a natural relation between human an environment. 5.3 Thermal Capacitor Place In designing of the building, the place of thermal capacitor was considered in length of +78.25 to +76.50 meters (capacitor height is 1.5 meters) relative to site natural soil. Indeed thermal capacitor was placed underground under installation floor. It is in 4 to 5 meters of lateral section Inner Street inside the soil. In this case the best condition for adjacent of the capacitor and soil is obtained and required thermal exchangers are used optimally. Thermal capacitor is connected to ground floor by special installation channels (from behind of shear cylinders) and central hall is feed accordingly. Fresh air entering channel (summer) was built in north corner of the site in order to reduce air temperature by shadow [7]. While Fresh air entering channel (winter) was built in North West corner of the site in order to increase temperature in the winter. 5.4 Other Secondary (Auxiliary) Factors Two glass partitions in distance of 75 centimetres cover official tower and external parts of building façade act as spear part for thermal capacitor and provides following advantages: They act as thermal greenhouse in the winter and increase sun heat utilization. In the summer air vertical draught discharges facade heat and prevent sun exposure by opening one row of extreme windows(in its extreme height) [8].

Fig.8: Interior Spaces of Shahid Ansari hospital, Lahijan, Iran

Fig.8: Air Movement and Thermal Capacitor in Shahid Ansari hospital, Lahijan, Iran

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Fig.10: Air Supplying System from Heat Exchange Space in Shahid Ansari hospital, Lahijan, Iran

Fig.11: Vents and Air Flow in Shahid Ansari hospital, Lahijan, Iran 6 Conclusion 1- The saved energy in the ground (thermal storage) can be used as following: 1-1) in the form of the passive systems by architectural anticipations and adaptation them with the environment 1-2) in the form of active systems by the thermal machines 2) In using the passive system it is not necessary to have installations and special machinery and only we can rely on these special anticipations of architecture to use of this clean and fresh, and free energy which causes energy consumption to be reduced and consequently give us excellent economic advantages.

3) if the thermal storage is used to cooling production and to building refreshment, it will be better, in the conditions which environmental necessities expand the area thermal storage to be expanded from the area of building condition towards the green spaces (which have more moisture due to the great watering) if not so, remains under the basement floor. 4) Using of thermal storage in relation to the building, in places such as: a)under the buildings and b) basements around the buildings which is more important to take thermal energy with great in winter and cooling in summer. 5) The expensing of the construction of Vienna bank’s thermal storage in Austria during 6 to 7 years of fuel and energy rate of building consumption, and this proves considerably a suitable economizing in fuel and energy expensing, in later years, too. 6) With great effective using of thermal storage of the earth, the condition of comfort and resting will be possible inside the building, so we will have the economizing of about 50 percent (no more) in energy consumption. References: [1] Ghobadiyan, V., Climatic Analyses of Iranian

Traditional Architecture, Tehran University Publications, 1998.

[2] Memarian, G., Iranian Architecture, Sorush-e-Danesh Publications, 2008. [3] Kasmaei, M., Climatic Classification of Iran

Housing and Residential Environments, Building and Housing Research Center Publications, 1992.

[4] Mohammadnia, S., Using Climatic Elements for Residential Construction in Cold & Dry Climates with energy efficiency, Azadeh Publications, 2005.

[5] Saberi, O., Low Energy Architecture, Negah-e-Sahrghi Publications, 2001. [6] Tabatabaei, M., Building Services Calculations,

Karoun Publications, 1998. [7] Mahdavi, M., Climatic Design, Tehran University Publications, 2004 [8] Researchers, patterns and the performed

examinations by the authors

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