Increasing consumption of energy derived from fossil fuels while has caused rapid economic growth in different communities, due to pollutant emission and its consequences, has faced the world with risky changes as well. Limitation of this non-renewable sources cased that energy consumption optimization policy become the governments work programs outline. On the other hand, growth of science and technology in the world has led to transformation of the commonly used methods of energy consumption, and discovering new energy sources has caused a major evolution in development of human societies. In this regard, the relatively simple technology, not  polluting the environment etc. are the reasons that make the necessity of using solar energy more and more evident. Since most of the energy is consumed in buildings, functional identification of optimization systems in buildings is essential. The present study aimed to introduce, evaluate, and set priorities for use of energy systems in buildings. To this aim, first, all systems were identified and their fields of application were specified. Then, in a comparative study, the priorities for use of the systems and their application were examined in building sector.Key words: energy, solar system, active systems, passive systems

Mohammadi, MA Khan

Sobhan, LN

English

AJOL - African Journals Online

PRIORITIES FOR USE OF PASSIVE AND ACTIVE SOLAR SYSTEMS IN COLDCLIMATE BUILDINGSL. N. Sobhan*1 and M. A. Khan Mohammadi21MSc Student of Architecture, Iran University of Science and Technology, Tehran, Iran2Assistant Professor, Faculty of Architecture and Urbanism, Iran University of Science andTechnology, Tehran, IranPublished online: 23 July 2016AbstractIncreasing consumption of energy derived from fossil fuels while has caused rapid economicgrowth in different communities, due to pollutant emission and its consequences, has faced theworld with risky changes as well. Limitation of this non-renewable sources cased that energyconsumption optimization policy become the governments work programs outline. On the otherhand, growth of science and technology in the world has led to transformation of the commonlyused methods of energy consumption, and discovering new energy sources has caused a majorevolution in development of human societies. In this regard, the relatively simple technology, notpolluting the environment etc. are the reasons that make the necessity of using solar energy moreand more evident. Since most of the energy is consumed in buildings, functional identification ofoptimization systems in buildings is essential.Author Correspondence, e-mail: Arch14.ma@gmail.comdoi: http://dx.doi.org/10.4314/jfas.v8i2s.163Journal of Fundamental and Applied SciencesISSN 1112-9867Available online at http://www.jfas.infoResearch ArticleSpecial IssueJournal of Fundamental and Applied Sciences is licensed under a Creative Commons Attribution-NonCommercial 4.0International License. Libraries Resource Directory. We are listed under Research Associations category.L. N. Sobhan et al. J Fundam Appl Sci. 2016, 8(2S), 1985-1997 1986The present study aimed to introduce, evaluate, and set priorities for use of energy systems inbuildings. To this aim, first, all systems were identified and their fields of application werespecified. Then, in a comparative study, the priorities for use of the systems and their applicationwere examined in building sector.Key words: energy, solar system, active systems, passive systems.INTRODUCTIONEnergy is one of the most important factors essential for developing countries. Energy sources inthe world can be classified into three major groups of fossil energy (oil, gas, coal, etc.), nuclearenergy and renewable energy (solar, wind, geothermal, biomass, etc.). Today, with everincreasing energy consumption, use of renewable energy sources, especially solar energy, hasbecome especially important. Sun is the best source of energy for any natural and syntheticactivity as well as different human technologies. The present environmental crisis such as globalwarming, air and water pollution, etc. are caused by excessive use of fossil fuels. So the bestsolution is to use natural energy sources such as solar energy. The term “solar thermal energy”includes all states of use of solar heat. This can be done using different technologies. In recentyears, several researches have been conducted in the field of using new energies, especially solarenergy. Many of these researches have been conducted on conversion of radiant energy into heat.Therefore, the present study aimed to analyze methods of using solar energy as one of the mostimportant renewable energy sources in the building sector.Solar energy as an energy supplierSimple technology, not polluting air and environment, and most importantly, saving fossil fuelsfor posterity are the main reasons for necessity and importance of using solar energy in ourcountry."Faber Bayram" emphasizing the importance of using solar energy, stated that: If human life isnot compromised by lack of oxygen, nuclear radiation, air and water pollution and destruction ofgreen spaces, certainly he will be endangered by the lack of understanding benefits of thesunlight and refusing to use it in living spaces [2]. In fact, converting it into heat energy throughsolar thermal collectors is the easiest way to use solar energy. So, it is understandable that theinitial development of solar energy systems focused on the supply of hot water. However, directL. N. Sobhan et al. J Fundam Appl Sci. 2016, 8(2S), 1985-1997 1987conversion of sunlight into electricity drew the attention of a many scientists, not only becausethis technology could effectively reduce the concentration of power generation systems, but alsogenerating electricity from solar energy with low cost and high efficiency has always been one ofthe human desires [4]. Such a system enables buildings to work without the need for externalfossil or synthetic energy with very low maximum energy consumption.Different types of solar systemsBuildings can supply their need for heat from the sun in two ways: passive and active. Passivesolar systems are the systems that collect, store and distribute solar energy without using energyconsumer systems such as fans, pumps or complex controls [1]. In fact, in a passive heatingsystem, heating the building is done naturally using natural factors like the sun. This means thatsuch a system enables buildings to work without the need for external fossil or synthetic energywith very low maximum energy consumption [3].Methods for passively use of solar energy includes:Direct receiving systemIndirect receiving systemActive solar systems are the systems that collect and store solar energy using mechanicalequipment and other energies (usually electricity) to be transferred inside buildings at the righttime [1]. In the next section, detailed properties and design principles of each system arediscussed.A comparison between active and passive solar systemsThe goal of active and passive solar systems is to maximum efficient use of solar energy, butthey are different in nature and function. Each of these systems are used according to needs andclimatic conditions considering demands and objectives of the project (heating, cooling,electricity). Despite the differences and common points, these systems have also structuraldifferences shown in Table 1.L. N. Sobhan et al. J Fundam Appl Sci. 2016, 8(2S), 1985-1997 1988Table 1. Comparison between active and passive solar systemsActive solar systems Passive solar systemsActive use of solar energy requires use ofequipment such as solar collectors, plumbingand water circulating pump.Passive use of solar energy does not requireproduction, collection and mechanicaldistribution systemsThis system requires relatively highinvestment and maintenance costs.Indirect passive systems require lower designand implementation costs compared to othermethodsNo need for basic and complex infrastructure,also provides the possibility of takingadvantage from the system in pre-builtbuildings.Indirect solar systems have specific designprinciples, so their special structures such asform, location and heat storages, like walls,ceilings and glass walls must be carefullydesigned before construction.These systems are used to supply electricity,heating and cooling energies in buildings.Depending on the type and mode ofoperation, these systems are used for heatingand cooling (natural ventilation) of buildings.Efficiency of solar systemsSeveral factors affect efficiency and performance of solar systems in buildings that can influenceamount and the way of receiving solar energy directly or indirectly.L. N. Sobhan et al. J Fundam Appl Sci. 2016, 8(2S), 1985-1997 1989Table 2. Factors affecting solar systems performancesFactors affecting efficiency and performance of solar systemsMethod for use of solar energyUse of active or passive systemsUse of direct or indirect passive systemsClimatic conditions of the desired regionLatitude and longitudeAverage monthly temperatureRadiation intensityRadiation durationRadiation energy levelPosition and orientation of the building andsolar systems deploymentStatus and characteristics of the surroundingenvironmentInstallation location and angles of passive solarsystemsLocation of absorbent walls and glass walls inpassive solar systemsGeometry of the buildingImpact of structure and form of the building onamount and method of receiving solar energyDimensions and installation of transparent wallsin facadesWalls materialsSurface ability of absorption and heat storagecapacity of materialsPassive solar systems1- Direct receiving systemThe most common solar system is called direct receiving system. Direct receiving is related tothe sunlight that enters inside the building through windows, skylights, etc. and heats the home.Use of natural light is one of the most efficient methods for use of solar energy in buildings [7].Climate design approaches in architecture of cold climate buildings by receiving sunlight directlyinclude the following items:- Use of glass walls on the south side for maximum thermal energy absorption during thewinterL. N. Sobhan et al. J Fundam Appl Sci. 2016, 8(2S), 1985-1997 1990- Use of tall windows for maximum use of sunlight (using canopies or smart glass on southwalls to avoid direct sunlight during the summer)- Use of materials with high thermal capacity for walls (heat absorption by the thermalmass from the sun during the day, and transferring the heat stored in the thermal massinside the building after sunset)- Use of dark colors for the outer walls and ceilings to absorb maximum solar energy2- Indirect receiving systemMost passive solar systems use thermal mass or materials with high absorption capacity and heatstorage. In an indirect receiving system, thermal mass is located between the interior of thebuilding and the sun, it absorbs the sunlight that reaches its surface and transfers it inside thebuilding by conduction. Different types of passive indirect receiving systems are as follows:- Trombe wall- Blue wall- Greenhouse method- Solar chimney- Blue roof (pool or pond on the roof)In this paper three of these methods are discussed briefly.1-1 Trombe wallTrombe wall is a passive and indirect method based on its function. The main idea of solar wallwas first proposed by Edward Morse, but it was fully developed as an element of buildings byFrench engineers Felix Trombe and Jacques Michael in 1960. Heating by Trombe wall is basedon solar radiation absorbed by a wall with high thermal capacity and radiation absorptioncoefficient. This wall is placed behind a transparent glass wall on the south side of the building(towards sun during the winter in the northern hemisphere). The heat absorbed by Trombe wall istrapped within the space between the wall and the glass and is transmitted inside the buildingthrough heat transfer, thermal conductivity, displacement, and radiation. Two valves on thebottom and top of the elevation profile of the wall causes airflow between the two profiles [6].L. N. Sobhan et al. J Fundam Appl Sci. 2016, 8(2S), 1985-1997 1991Table 3. Trombe wall performance in cold seasons- Trombe wall usually consists of a 20-40 cm wall and glass located at adistance of 1.5-2 cm- Heat energy is absorbed by darkthermal mass and is stored in it andwarms the building slowlyReference: [10]During the day, cool air enters into the spacebetween the wall and the glass through thebottom valve embedded in the wall and isheated by the sun. Heated air moves upwarddue to the density difference and comes insidethe building through the top valve.During the night, the valves on the wall areclosed and airflow between inside and the spacebetween the walls is interrupted and onlythermal energy stored in the wall during the dayis transmitted inside the building.1-2 Solar greenhouseSolar greenhouse is one of the passive solar systems. Performance of the greenhouse is verysimilar to the Trombe wall and it warms the space through radiation and convection. However, insolar greenhouse, the space between the glass and the thermal mass (the wall) is a habitablespace.InsideOutsideAirflowAbsorbent wallAirflow2-layered transparentmaterials are separatedwith a 1.5 cm spaceBlack wallAirflowCap for one-way airflowL. N. Sobhan et al. J Fundam Appl Sci. 2016, 8(2S), 1985-1997 1992A greenhouse facing the sun in connection with interior of the building, in addition to helpreceiving solar heat energy like a solar collector, also stores the received heat during the day forthe night and it can be used to warm up other parts of the building [3].Table 4. Performance of the greenhouseHeat energy is absorbed by the walls and floorof the greenhouse and it is stored in it andslowly warms up the interior space.Reference: [13]During the day, cool air enters into thegreenhouse and is heated by the sun. Heated aircomes inside the building through the top valve.Greenhouse space is not good for cold nights.Because the energy is dissipated through theglass wall during the night as much as energyreceived during the day. However, absorbentwall valves are closed during the night and theheat energy stored in wall is transmitted insidethe building.1-3 Solar chimneyThe first study on solar chimney was conducted by Bansal et al. (1993). They approved increasein ventilation using solar chimney and correct system design by developing a mathematicalmodel. Afonso and Oliveira compared solar chimney with typical chimney and confirmed effectof solar energy on increased ventilation and showed that solar chimney effectively improvesventilation [5]. The combination of radiation and convection in solar chimney leads toWarm airflowInsideOutsideCold airflowGreenhousespaceL. N. Sobhan et al. J Fundam Appl Sci. 2016, 8(2S), 1985-1997 1993considerable air upward movement and thus increase in ventilation. This upward movementgenerates a thrust force which can increase natural ventilation in adjacent spaces [6]. In fact,solar chimney is a passive solar system for ventilation using the chimney effect.Table 5. Solar chimney performanceSolar chimney consists of a glass wall, cavityand insulation wall. Air is heated by solarenergy in the chimney and warm air movesupward because of lightweight.Reference: [14]During the day in the summer, cold air entersinto the chimney through the valve embeddedat the end of the wall and is heated by the sun.Heated air moves upward and goes out of thechimney and causes natural ventilation andcooling spaces around the solar chimney.During the day in the winter when there is noneed for natural ventilation, the end valve isclosed and the valve embedded at the top of thewall is opened and warm air enters inside thebuilding.Warm airInsulatorValveCold airflowL. N. Sobhan et al. J Fundam Appl Sci. 2016, 8(2S), 1985-1997 1994Active solar systemsActive solar systems in the near future will probably have more influence than passive systemsbecause these systems can be quickly deployed in millions of homes and commercial buildings.Solar collector, that sun is its heat source, is the main element of an active solar system. Themain components of a collector include storage system and a proper heat distribution system. Inaddition to these three main parts, an auxiliary heat source is usually used to provide energy forheating system when solar energy cannot meet thermal requirements. There are also pumps,thermostats, valves, motorized dampers and electrical devices for operation and control of thesystem [3]. Photovoltaic systems and solar water heaters are the most common active solarsystem in the building sector.1- Photovoltaic systemsPhotovoltaic system is one of the new technologies in energy production. In design ofphotovoltaic systems, factors such as determining slope and slope direction, ghosting,coordination with passive solar systems, ventilation of the system, impact of the plan form, tilt ofthe building facade walls, etc. should be considered [8]. With the increasing intensity of solarradiation, the amount of electrical power output is increased. Thus, power efficiency of the solarphotovoltaic system is directly correlated with the received solar energy.Fig.1. Schematic diagram of a photovoltaic system. Reference [12]Solar panels StorageL. N. Sobhan et al. J Fundam Appl Sci. 2016, 8(2S), 1985-1997 19952- Solar water heaterProduction of domestic hot water is the most economical way of using solar energy. The simplestsolar water heater system consists of a flat collector and a storage tank, in which water orworking fluid flows naturally due to differences in temperature using thermosiphon system. Inthis water heater, the upper part of the collector must be lower than the bottom of the tank, andthe minimum degree of deviation with respect to the horizon should be about 20 degrees towardsthe south for realization of thermosiphon flow. This system is filled with cold water and water isgradually heated inside the collector pipes when the sun shines on the surface of collector andslowly flows into the storage tank. Cold water in the tank also flows toward the bottom of thecollector through another pipe. This procedure continues as long as the solar radiation issufficient to heat the water [3].Fig.2. Schematic diagram of a solar water heater. Reference [11]CONCLUSIONSUse of renewable energies along with climate design is one of the effective methods to optimizeenergy consumption in the building sector. This means that buildings should be designed tomaximum use of natural energy sources and reduce energy consumption based on climate of thedesired region. Proper design of buildings plays a significant role in reducing the harmful effectsof construction industry and optimization of energy consumption. Solar energy is one of theavailable natural renewable energies that, due to its special benefits, plays a significant role inHot waterCold waterControllerSolar pipesPumpL. N. Sobhan et al. J Fundam Appl Sci. 2016, 8(2S), 1985-1997 1996design of sustainable buildings with minimum energy consumption, especially in cold climate.Thus, given the importance of this issue, the present study tried to analyze and examineperformance of each system.References1- Ahmadi Nodooshan, A. (2014). Strategies to reduce energy consumption in buildings,Journal of Daneshnama, vol. 227-229, pp. 122-130.2- Emami, J. (2007). Natural light in the interior design, Journal of Abadi, vol. 57, pp. 38-41.3- Beytollahi, F., and Abedi, A. (2014). Application of solar energy in buildings, Journal ofDaneshnama, vol. 227-229, pp. 38-43.4- Rezamanesh, M., and Nazari Azar, M. (2014). Renewable energies and their applicationin buildings (photovoltaic system), Journal of Daneshnama, vol. 227-229, pp. 44-52.5- Fakhari, M., and Heidari, S. (2013). Optimization of solar chimney and its effect on thebuilding's ventilation, Journal of Fine Arts, Architecture and Urbanization, vol. 18, no. 2,pp. 83-88.6- Ghiabakloo, Z. (2012). Building physics – basics 2: setting environmental conditions,Amirkabir Jahad Daneshgahi Publications.7- Kameli, H. (2014). Examination of effective parameters on the performance of Trombewall using dynamics simulation of computational fluids, Journal of Iran's Energy, vol. 17,no. 4, pp.101-118.8- Kasmaee, M. (1990). Climate design guide, Building and Housing Research Center, FirstEdition.9- National Building Regulations, Section 19.10- Vafaei, R. (2009). Investigating design methods of photovoltaic systems integrated withbuilding, Journal of Sofeh, no. 49, pp. 71-80.11- Miyazaki, T., Akisawa, A. & Kashiwagi, T. (2006) "The effects of solar chimneys onthermal load mitigation of office buildings under the Japanese climate." RenewableEnergy, 31, 987–1010.12- http://www.my-waterjet-cutting-service.com/13- www.energyhouseco.com14- www.afshidco.com/portals/0/Afshid.dc.jpgL. N. Sobhan et al. J Fundam Appl Sci. 2016, 8(2S), 1985-1997 199715- http://www.homepower.com16- http://www.yourhome.gov.au/How to cite this article:Sobhan L.N, Khan Mohammadi M.A. Priorities for use of passive and active solar systems incold climate buildings. J. Fundam. Appl. Sci., 2016, 8(2S), 1985-1997.

Priorities for use of passive and active solar systems in cold climate buildings.

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Priorities for use of passive and active solar systems in cold climate buildings.

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