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Topic 1. Building energy demand and energy performance of buildings, systems, and componentsBaseline Models for Commercial Building Energy Consumption and Case Studies in TianjinBo Peng1,*, Borong Lin1, Juan Xiao11 School of Architecture, Tsinghua University, Beijing, China*Corresponding email: ebu003@Keywords: Baseline Model, Energy Consumption, Commercial Building, DeSTSUMMARYIn this study, the baseline models for three different types of commercial building were discussed and established according to the building function and the laws and regulations related to building energy efficiency in China. And based on the settings of each baseline model, the related case studies in Yujiapu project in Tianjin were made to calculate the room load and annual energy consumption with the energy simulation software DeST. The results show that the total annual energy consumption of the office, hotel and emporium is respectively 177kWh/m2, 157kWh/m2 and 221kWh/m2. And the proportion of energy consumption of each part is different for the three types of commercial buildings due to the different function and the differences in baseline model settings.INTRODUCTIONTo address global climate change and achieve sustainable development, energy saving and CO2 emissions reduction is a very important way both in China and all over the world. To achieve efficiency targets in construction industry is a very important development strategy, as about 40% of the total energy consumption is used directly or indirectly in construction sector. And the research on baseline model for buildings is very helpful to predict building energy consumption and guide the design of new buildings. The baseline model is also the premise of the evaluation of building energy consumption and CO2 emissions in building evaluation standards, such as CDM. In this study, the baseline model for different types of commercial building will be discussed and related case studies of the commercial buildings in Yujiapu program in Tianjin will be made to study the rationality of the baseline models. METHODSAccording to the laws and regulations related to building energy efficiency in China, the baseline models for different types of commercial building were established based on the characteristics of building type and weather data in Tianjin. In this study, there are three types of commercial buildings: office, hotel and emporium located at Yujiapu project in Tianjin. And the baseline energy model settings for each building are including building envelope thermal parameters, indoor environmental design parameters, HVAC systems, and lighting and equipment settings. Comparative study of different model settings has been done.And based on the baseline models, the heating load and cooling load was calculated by DeST (Yan Da et al. 2008), which is developed by Department of Building Science in Tsinghua University. And its core for load calculation is State Space Method. According to the HVAC system settings, the annual energy consumption of HVAC was also calculated by DeST. The electricity consumption of lighting and device was calculated based on the lighting and device power density and each schedule throughout the year. The total annual energy consumption of different types of commercial buildings was calculated and compared to the energy consumption statistics of the local actual buildings to discuss the rationality of the baseline models.BUILDING BASELINE MODELIn this study, the building baseline models are including envelope thermal parameters, indoor environmental design parameters, the schedules of lighting, devices and occupants and HVAC system settings. First of all, the building envelope thermal parameters were determined according to the Design Standard for Energy Efficiency of Public Buildings (GB50189-2005) for each type of commercial building. The specific parameter settings are shown in table 1.Table 1. Envelope thermal parameters of the baseline modelsBuilding type K-wall K-roof K-window SC-windowW/(m・K) W/(m2・K) W/(m2・K)Office 0.6 0.513 2.0 0.5Hotel 0.6 0.513 2.7 0.7Emporium 0.6 0.513 2.0 0.5Three commercial building cases of Yujiapu project in Tianjin were chosen to evaluate the baseline models by simulating the energy consumption. The basic information of the three cases is shown in table 2.Table 2. Basic information of the case study buildingsBuilding TypeTotalFloor AreaHeightStoryNumberConstructionStoreyheightWindow-wallratio m2 m mOffice 100,000 160 37 SRC 4.3 0.7Hotel 49,500 180 45 RC 4 0.4/0.21Emporium20,000 30 5 RC 6 0.1/0.42 1The window-wall ratio is 0.4 for the guest room and 0.2 for the other rooms.2 The window-wall ratio is 0.1 for the first 4 stories and 0.4 for the 5th story.The schedules of lighting, device and occupants are different due to various functions of the building and the different living modes. These schedules were decided according to the actual operation condition of each building. The final schedules are shown in figure1 to figure 3. From these schedules we can see that there are very large differences between different building types, which will have a considerable impact on the energy consumption of the building.Figure 1. Lighting schedules of different types of commercial buildingsFigure 2. Occupants schedules of different types of commercial buildingsFigure 3. Device schedules of different types of commercial buildingsIndoor design parameters of air-conditioning system include temperature, relative humidity, occupant density, fresh air volume and power density of lighting and device. The settings of these parameters of a building will affect not only its HVAC system design but also the actual energy consumption in operation phase directly. For the commercial buildings, the indoor environment design parameters of each baseline model in this study were chosen according to the Design Standard for Energy Efficiency of Public Buildings (GB50189-2005) of China. The detailed parameter settings for different seasons are shown in table 3. And the schedules of HVAC system for each case are shown in table 4. In the simulation, the heat dissipating capacity of indoor people is set as 120W/m2, including both sensible heat and latent heat. All-year hourly meteorological parameters used in the simulation are shown in figure 4.Table 3. Indoor air conditioning design parameters of the baseline modelsBuilding type Room function Summer Winter People/m 2 Lighting Device Fresh air m 3/h t in °C Rh % t in °C Rh %W/m 2 W/m 2 Office Office 25 50 20 40 0.15 15 40 30Lobby 28 50 16 － 0.05 105 30Corridor 26 50 18 40 0 10 - -Hotel Guest 24 50 21 40 0.06 15 20 50Dining 24 50 22 40 0.4 13 5 30Banquet 24 50 22 40 0.7 18 5 30 Lobby 25 50 18 40 0.1 15 5 10Corridor 25 50 18 40 0 5 0 0Office 25 50 20 40 0.15 15 40 30Emporium Market 25 50 18 40 0.33 19 13 20Dining 25 50 18 － 0.50 13 5 20 Corridor 26 50 18 40 0 5 - -Office 25 50 20 40 0.15 15 40 30Table 4. Annual HVAC schedule for each caseOffice Hotel Emporium Mouth Time Mouth Time Mouth TimeOperation 9～20 8～22 8～22Cooling 6.01~9.30 8～20 5.01~10.0724h5.01~10.07 7～22 Heating 11.15~3.15 24h 11.01~3.3124h 11.01~3.31 24hFigure 4. All-year hourly meteorological parameters of TianjinRESULTSBuilding LoadThe indoor heat gains from people, lighting and device is set as 100% in cooling season, 50% in heating season and 80% in transition season in the simulation. The infiltration (unintentional ventilation) rate of the construction is set as 0.15 times per hour. The baseline models of hotel and emporium have fresh air heat recovery system, and the efficiency of the heat recovery is set as 40% in both heating and cooling season. The all-year hourly dynamic load calculated by DeST for each case are show in figure 5~7.Figure 5. All-year hourly dynamic load of the office caseFigure 6. All-year hourly dynamic load of the hotel caseFigure 7. All-year hourly dynamic load of the emporium caseThe calculated cumulative cooling load and heating load of the office case is respectively 127kWh/m2 and 35kWh/m2, while the statistical valve of office building in 2009 Annual Report on China Building Energy Efficiency (THUBERC 2009) is respectively 78kWh/m2 and 50kWh/m2. And the calculated cumulative cooling and heating load of the hotel case is respectively 99kWh/m2 and 28kWh/m2, while the statistical valve is respectively 89kWh/m2 and 83kWh/m2. The calculated cumulative cooling and heating load of the emporium case is respectively 111kWh/m2 and 31kWh/m2, while the statistical valve is respectively 133kWh/m2 and 33kWh/m2. The typical daily load in heating and cooling season are shown in figure 8~10.Figure 8. Typical daily load of the office case in summer and winterFigure 9. Typical daily load of the hotel case in summer and winterFigure 10. Typical daily load of the emporium case in summer and winterEnergy ConsumptionAccording to the baseline model settings and the heating and cooling load calculated by DeST, the annual energy consumption of different parts for each case has been calculated based on various way and data sources. The energy consumption of lighting and equipment were calculated according to the power density and the schedules throughout the year. Based on the dynamic load, the energy consumption of HVAC system, such as cold machine, cooling tower and water pump, were calculated by the water simulation module in DeST, in which the COP of the cold machine is 5.1, the efficiency of the water pump and fan is 0.572. The energy consumption of the gas was also calculated by DeST, and the input and output water temperature of the gas-fired boiler is set as 55/95°C in municipal heating system. The mechanical ventilation rate of the toilet and kitchen is respectively 15ACH and 10ACH for the ventilation energy consumption calculation. The energy consumption of water supply and drainage, elevator and domestic hot water for each case are the statistics in 2009 Annual Report on China Building Energy Efficiency (THUBERC 2009). The compositions of the annual primary energy consumption of each case in proportion form are shown in figure 11, and the energy consumption of each part in the form of electricity use is shown in table 5,based on the primary energy conversion method with the electricity conversion coefficient 9.367MJ/kWh in China. The energy consumption of the electricity transformation and distribution system in the hotel case is 2.4kWh/ (m2.a), and the energy consumption of the freezing and cold storage system in the emporium case is 10.8kWh/ (m2.a), which in the table are both expressed as other legend.Figure 11. The composition of the annual primary energy consumption of each case Table 5. Annual energy consumption of each case（kWh/(m2.a)）EmporiumHotelOfficeLighting 27.1 36.2 53.3Equipment 66.8 19.5 37.3Cold machine 20.5 17.6 19.1Cooling tower 1.4 1.7 2.8Water pump 6.4 6.9 13.749.812Fan 31.76.120.7Gas 14.7Elevator 3 3 15Water supply 1 5.8 0.2Ventilation 2.2 16.7 6.56.819.1DHW 2.210.82.4Other 0221.2 Total 177.0157.3 DISCUSSIONThe results of the calculated room load show that the cooling load of the office building is much higher than the statistics while the calculated heating load is much lower. From the results of composition of the energy consumption it can be found that the energy consumption of equipment has accounted for about 40% of the total energy consumption of the office building, which indicates the power density of equipment in office baseline model may be a little higher. The calculated room load of the emporium case is roughly equal to the statistics compared to the other two cases. The energy consumption results show that the total annual energy consumption of the office, hotel and emporium is respectively 177kWh/m2,157kWh/m2 and 221kWh/m2. And the proportion of energy consumption of each part is different for the three types of commercial buildings. For example, the energy consumption of lighting and equipment accounted for 57% of the total annual energy consumption for the office building, 38% for the market and only 41% for the hotel. And the energy consumption proportion of HVAC system for office, hotel and emporium is respectively 35%, 22% and 39%. The energy consumption of both ventilation and DHW of hotel is much higher than that of office and emporium. These differences are mainly caused by the function of the building and the energy use condition in operation phase, which reflected on the differences of the settings in the baseline model. For example, the power density of the equipment in the main room in office building is set as 40 W/m2 and that of the hotel and emporium is respectively 20W/m2 and 13W/m2, which causes that the final annual energy consumption of equipment for the three cases is respectively 66.8kWh/m2, 19.5kWh/m2 and 37.3kWh/m2.CONCLUSIONSBased on the function of the building and the energy efficiency standard, the baseline model for office, hotel and emporium have been established. The results of the energy consumption of the cases in Yujiapu project show that the settings in the baseline model such as HVAC system, lighting and equipment have great influence on the final total energy consumption and also the energy distribution of each part for a certain commercial building. And the baseline models vary with climates, the models in this study are just baseline models for Tianjin. So the settings of the baseline model need to comply with relative building standard as well as the actual use conditions for different building function. ACKNOWLEDGEMENTThis research is supported by National 12th-Five S&T Projects 2012BAJ09B03 and 2011BAJ04B06.REFERENCESTHUBERC 2009. 2009 Annual Report on China Building Energy Efficiency. pp. 30-67.Yan Da et al.2008. “DeST-An Integrated building simulation toolkit part 1: fundamentals,”Building Simulation, 1(2) ,95-110。