CLIMAMED VII. Mediterranean Congress of Climatization, Istanbul, 3-4 October, 2013 TURKISH SOCIETY OF HVAC & SANITARY ENGINEERS ___________________________________________________________________________________________________
TESTING A SIMPLIFIED BUILDING ENERGY SIMULATION PROGRAM VIA BUILDING ENERGY SIMULATION TEST (BESTEST) Gülden Gökçen Akkurt1, Cem Doan ahin1, Sava Takan1, Zeynep Durmu Arsan1 1
zmir Institute of Technology, zmir
Corresponding email:
[email protected]
SUMMARY In Europe, residential and service buildings are responsible for more than 40% of primary energy consumption and this ratio is expected to rise. European authorities have undertaken the challange to control domestic energy consumption of buildings to reduce greenhouse gas emissions and the studies on efficient energy use have been accelerated since 1992. Most important outcome of these studies is the European Union Directive on the Energy Performance of Buildings. The Directive underlines the structure of methods which determine the energy performance of buildings for member states. Turkey is revising its legislations on building energy performance as foreseen in Directive on the Energy Performance of buildings through the European Union accession process. “Directive on Energy Performance of Buildings” were introduced in July 2008, urges to develop national building energy simulation methodologies on evaluation of building energy performance. KEP-SDM is one of the simplified methodologies developed based on the regulation. The methodologies are reliable as long as they are validated. The aim of this study is to assess the accuracy of “KEP-SDM” by “BESTEST”. Climatic zone approach and software-based weather data were implemented into KEP-SDM and the results were compared with eachother. It was concluded that sensitivity of the weather data affects the accuracy of building energy simulation methodologies quite significantly.
INTRODUCTION The building industry and the built environment are some of the largest contributors to energy and material use worldwide. In the northern part of the European Union, 41% of total final energy consumption comes from buildings, with 30% being used in residential buildings [1]. Due to importance of a good quality of the indoor environment and problems caused by high energy consumption, governments have enacted a series of policies and regulations aimed at increasing the energy efficiency of residential buildings and ensuring a good indoor environment. An example of such initiatives is the European Union Directive on the Energy Performance of Buildings (EPBD). EPBD obliges all European member states to implement
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CLIMAMED VII. Mediterranean Congress of Climatization, Istanbul, 3-4 October, 2013 TURKISH SOCIETY OF HVAC & SANITARY ENGINEERS ___________________________________________________________________________________________________
performance-based energy regulations aimed at decreasing energy consumption in buildings in relation to heating, cooling, ventilation, lighting and domestic hot water [1]. Turkey is revising its legislations on building energy performance as foreseen in EPBD, through the European union accession process. TS 825 which is “Thermal insulation requirements for buildings” standard, came into force at 2000, was revised in 2008 [2]. Energy Efficiency Law is released in February 2007; urging industry, transportation and residential sectors to take measures on improvement of energy efficiency [3]. The target of the law is to reduce energy intensity (kJ/$) of Turkey by 10% till 2020. Furthermore in December 2008, the Ministry of Public Works and Settlement introduced a regulation titled as “Directive on Energy Performance of Buildings” [4]. According to this regulation, new buildings and buildings under major renovation are urged to obtain an “Energy Certificate” which includes heating, cooling, domestic hot water and lighting energy consumptions as well as “Greenhouse Gas Emission Sertificate” as a result of energy consumption. In July 2008, Turkey signed Kyoto Protocol and commited to reduce greenhouse gas emmisions by 10% compared to 1998 [5]. Based on the “Directive on Energy Performance of Buildings”, national building energy simulation (BES) methodologies have been developed such as Standard Assessment Method for Energy Performance of Residential Buildings (KEP-SDM) [6] and National Building Energy Performance Calculation Methodology (BEP-TR). The methodologies are reliable providing that they are validated.The purpose of this study is to presenta methodology based on the application of a well-known validation and diagnostics procedure, Building Energy Simulation Test (BESTEST) [7],to assess the accuracy of the simplified calculation method KEP-SDM.This paper also presents comparison ofthe test results of KEP-SDM with state of the art building energy simulation program (DB) [8]. Standard Assessment Method for Energy Performance of Residential Buildings (KEPSDM) The KEP-SDM is a methodology composed for calculating the energy performance and carbondioxide emissions of residential buildings per unit floor area. The methodology is compliant with(TS 825) [2]and the Standard Assessment Procedure (SAP) [9]. The calculation is based on energy balance taking into account of a range of factors below that contribute to energy efficiency:
Materials used for construction of the residential building Thermal insulation of the building fabric Ventilation characteristics of the residential building and ventilation equipment Efficiency and control of the heating systems Solar gains through openings of the residential building The fuel used to provide space and water heating, ventilation and lighting Renewable energy technologies
The calculation does not take into account of the factors stated below:
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CLIMAMED VII. Mediterranean Congress of Climatization, Istanbul, 3-4 October, 2013 TURKISH SOCIETY OF HVAC & SANITARY ENGINEERS ___________________________________________________________________________________________________
• • • •
Household size and composition Ownership Efficiency of particular domestic electrical appliances Individual heating patterns and temperatures
KEP-SDM is used to calculate the energy performace of residential buildings that have floor area less than 450 m2. The methodology estimates the annual energy consumption of the buildings depending on heating, domestic hot water and lighting demand where cooling is not considered [6].
Fig. 1 Heating degree-day climatic zones in Turkey [5]. KEP-SDM uses degree-day phenomenon in calculations. Degree-day approach is still prefered way for building energy performance calculations although there are other ways. According to American Gas Association, keeping an indoor evironment at 21°C is related to difference between 18°C and daily mean outdoor air temperature. Measuring the amount of fuel to heat up any space on whenever day is calculated using the difference between 18°C and daily mean outdoor air temperature. This difference is called heating degree-day (HDD) for any particular day [10]. Since HDD changes with climatal conditions and regions the degree-day phenomenon creates HDD climatic zones apart from geographical regions. There are four different HDD climatic zones according to TS 825, which are shown on Fig.1. Building Energy Simulation Test (BESTEST) BESTEST is a procedure, which was developed by International Energy Agency (IEA) in 1995, to test and diagnose the building energy simulation programs [11]. The procedure contains several tests assessing the effect of physical properties on the results of building energy simulations. The purpose of this procedure is to create obvious, well-defined test series for software-to-software comparisons and program diagnostics. Not every simulation program requires the same input to do calculations. Hence, test series defined in BESTEST are designed to test different building simulation programs[7].
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CLIMAMED VII. Mediterranean Congress of Climatization, Istanbul, 3-4 October, 2013 TURKISH SOCIETY OF HVAC & SANITARY ENGINEERS ___________________________________________________________________________________________________
Table 1.Description of BESTEST Cases (Summary). Caseno. Description 8m x 6m x 2.7m ; South facing 12 m2 window, no shading; Case 600 internal gains 200W;infiltration rate 0.5 ACH; low thermal mass; Same as Case 600 with 1 m full-width overhang on south Case 610 facade Same as Case 600 but with a 6 m2 east window and a 6 m2 Case 620 west window, no shading. Same as Case 620 with 1 m overehang over windows only, Case 630 plus 1 m fins on both sides of each window. There are 36 BESTEST cases in all, plus 4 free-floating cases (no heating or cooling) [7]. These cases are classified as either qualification or diagnostic cases. A recommended way to apply the procedure is to run the qualification tests first. The remaining cases are designed for diagnostic purpose. In this study, some BESTEST cases were used to assess the accuracy of the KEP-SDM. The reason of the case selection is based on applicability of the cases to KEPSDM. The cases applied are given in Table 1.
Figure 2. Isometric view of test case 600 [8]. The Case 600 is the base case which takes into consideration of the test construction illustrated on Fig. 2. Other test cases are variations of the base construction. The Case 610 includes 1 m overhang on south facade different from Case 600. The Case 620 consider 6m2 window in the west and east facade. Lastly, the Case 630 includes 1 m overhang extended across the 3 m width of each window and side fins different from Case 620. The BESTEST was designed to assess energy simulation programs which are able to run simulation for any climatic region and location [11]. Nevertheless, the KEP-SDM runs simulations taking into account the climatic zones of Turkey. Therefore, it is required to develop a way to apply BESTEST in different climates than the original Denver, USA data [11]. In this study, the KEP-SDM was tested using the weather data of zmir-Turkey. The following approach [11] was used to convert the BESTEST results into the weather data of zmir. State of the art building energy simulation program [8], was selected to apply the approach. The simulation program [8] is based on the calculation methodology, Energy Plus [12], improved with weather database and 3D interface [13].
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CLIMAMED VII. Mediterranean Congress of Climatization, Istanbul, 3-4 October, 2013 TURKISH SOCIETY OF HVAC & SANITARY ENGINEERS ___________________________________________________________________________________________________
First, all the BESTEST cases (600, 610, 620, 630) were run using the meteorological data of Denver-USA to confirm whether the energy simulation results of DB (QDB.Denver) are between the minimum and maximum values stated by the BESTEST (Qmin.Denver and Qmax.Denver). Based on the DB results for Denver and on BESTEST acceptable results, confidence intervals for each BESTEST case were calculated using (1) and (2). CImax= (Qmax.Denver – QDB.Denver) / QDB.Denver
(1)
CImin= (Qmin.Denver – QDB.Denver) / QDB.Denver
(2)
After that, the same BESTEST cases were simulated using DB for the weather data of zmir (QDB.zmir).Using the confidence intervals determined before and DB results for zmir, the new acceptable range (maximum and minimum) for zmir was determined using (3) and (4). Qmax.zmir= (1 + CImax) * QDB.zmir
(3)
Qmin.zmir= (1 + CImin) * QDB.zmir
(4)
This straightforward approach is developed using several assumptions. In reality, the new maximum and minimum results for zmir should be determined based on reference programs in the BESTEST procedure. Nevertheless, using of all BES programs in the BESTEST takes loads of time and requires expertise. Thus, the methodology previously suggested in this study providemeans to construct ranges of acceptable results for the BESTEST cases for any location and weather, requiring miminum sources and knowledge[11]. The new minimum and maximum acceptable values of BESTEST (Qmin.zmir and Qmax.zmir) calculated using (1), (2), (3) and (4) are given on Table 2.
Case 600 610 620 630
Table 2. BESTEST acceptance ranges for zmir. Qmin.zmir (kWh/year) Qmax.zmir (kWh/year) 1889,87 2511,46 1916,58 2546,34 2062,04 2657,00 2263,03 2898,91
RESULTS The comparison between KEP-SDM and BESTEST results are presented in Fig.s 3-6. The first and the last columns are the minimum and maximum energy demand values obtained by BESTEST, respectively. The second column represents result for zmirweather data calculated using DB. The third column indicates result for zmir determined using the KEPSDM (QKEP-SDM.zmir). According to the results for Case 600 illustrated in Fig. 3, it can be said that DB is close to minimum acceptable value. In other words, DB result for Case 600 is in the acceptance range. For this case, heating energy demand calculated using the KEP-SDM exceeds the maximum acceptable value by 20%.
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CLIMAMED VII. Mediterranean Congress of Climatization, Istanbul, 3-4 October, 2013 TURKISH SOCIETY OF HVAC & SANITARY ENGINEERS ___________________________________________________________________________________________________
Fig 3. Annual heating energy consumptions for Case 600. Analysing the results for Case 610, it can be noticed that Case 610 requires more energy demand than that of Case 600. The result for the KEP-SDM is outside of the acceptable range, when comparing to DB results. For this case, the result determined using DB is 1935 kWh per annum, which is just above the minimum acceptable value. The Case 610 has the same specifications as the Case 600 except that Case 610 has 1m full-witdh overhang on south facade. The overhang importantly increases the heating energy demand in the KEP-SDM. Similarly, the DB result shows increment for this case, but this increment is fairly lower than that of KEP-SDM. Fig. 4 illustrates the results for the Case 610.
Fig 4. Annual heating energy consumptions for Case 610. For Case 620, it can be observed that the change in window orientation increases the heating energy demand for zmir. As can be seen from the Fig. 5, heating energy consumption calculated using the DB is less than minimum acceptable value (2062 kWh per annum). Moreover, the KEP-SDM result for this case exceeds maximum acceptable value in 24%.
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CLIMAMED VII. Mediterranean Congress of Climatization, Istanbul, 3-4 October, 2013 TURKISH SOCIETY OF HVAC & SANITARY ENGINEERS ___________________________________________________________________________________________________
Fig 5. Annual heating consumptions for Case 620. The Case 630 includes 1 m overhang extended across the 3 m width of each window and side fins different from Case 620. The overhang and side fins increase the heating energy demand for both DB and KEP-SDM.It can be seen from the Fig. 6 that KEP-SDM presents result over the maximum acceptable value while the result determined using DB is below the minimum acceptance value.
Fig 6. Annual heating consumptions for Case 630. It can be noticed that the results calculated using KEP-SDM exceededmaximum acceptance value for all cases. The reason why all cases for KEP-SDM are above the acceptance range is thought to be weather data of zmir based on climatic zone approach. Thus, weather data of zmir based on TS 825 was changed with that of based on DB. Later, all cases were reperformed using weather data of zmir based on DB, instead. The simulation results obtained using the KEP-SDM with new weather data (KEP-SDM(DB)) were compared with KEPSDM that has weather data of zmir based on TS 825 (KEP-SDM(TS825)). Fig. 7 shows the results obtained for the new situation.
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CLIMAMED VII. Mediterranean Congress of Climatization, Istanbul, 3-4 October, 2013 TURKISH SOCIETY OF HVAC & SANITARY ENGINEERS ___________________________________________________________________________________________________
Fig. 7 Comparison of simulation results with changed weather data. As can be seen obviously that the results obtained using the KEP-SDM(DB) are in of acceptable range for all cases. It can be noticed that accuracy of weather data used in building energy simulations affects the results significantly. CONCLUSION In this study, a simplified BES methodology (KEP-SDM) was tested using a well-known validation and diagnostic procedure, Building Energy Simulation Test (BESTEST). Furthermore, test results obtained using KEP-SDM were compared with DB. It was oserved that for all BESTEST cases the KEP-SDM results calculated using weather data of TS 825 are out of the acceptance range. For cases 600 and 610 DB results are in of the acceptable value while DB results for cases 620 and 630 are lower than the minimum acceptable value. Moreover, all KEP-SDM results obtained using weather data of zmir of DB were in the acceptable values. As a consequence, it can be concluded that climatic zone approach of TS 825 causes errors on building energy simulations. Therefore, in BES programs it is significant to use weather data obtained from the meteorological station close to the building simulated. In the literature, Dombaycı focused on HDD and cooling degree day (CDD) numbers for 79 city centers in Turkey, covering a period of 21 years (1985-2005) [14]. Aim of this study is to determine HDD and CDD numbers for the accuracy of building energy simulations. Yılmaz inticated that the walls having the same heat transfer coefficient caused different energy consumptions in the cities having similar degree-day values at TS 825[15]. ACKNOWLEDGEMENT The authors would like to thank to Chamber of Mechanical Engineers,zmir for their support throughout this research.
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CLIMAMED VII. Mediterranean Congress of Climatization, Istanbul, 3-4 October, 2013 TURKISH SOCIETY OF HVAC & SANITARY ENGINEERS ___________________________________________________________________________________________________
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