Thermal Performance of Solar Heating System with Water Floor

Transcription

1 Plea24 - The 21 st Conference on Passive and Low Architecture. Eindhoven, The Netherlands, September 24 Page 1 of 6 Thermal Performance of Heating System with Water Floor Part 3. Verification of -energy consumption under residential conditions Zhejun Xian 1, Nobuyuki Sunaga 1 and Masanori Akita 1 1 Tokyo Metropolitan Univ., Graduate School of Eng, Dept. of Architecture 1-1 Minami-osawa, Hachioji-shi, Tokyo , Japan Tel.: Fax: kxzhj@ecomp.metro-u.ac.jp ABSTRACT: Thermal performance of a test house, which has an air-type solar heating system with Water Floor for heat storage and PV power generation system, is examined. Using the test house, five experiments were carried out regarding energy consumption. The results of the experiments show that the solar floor heating system with Water Floor is effective both for the creation of a comfortable thermal environment and energy performance. The results of the simulation show that this solar floor heating system with Water Floor reduces energy consumption for space heating by 58.8% and that the power generated by the PV system is enough to provide all energy necessary for space heating. Conference Topic: 7 - built environment Keywords: Water Floor, solar energy, floor heating, energy consumption 1.INTRODUCTION A series of studies have been carried out regarding the solar floor heating system with Water Floor. The floor, consisting of water-filled bags, stores the solar heat and distributes it throughout the house. In the previous papers [1, 2] the effect of the Water Floor on the indoor climate, where no auxiliary heating conditions exist were discussed and the following results obtained. 1). During the winter the living room temperature was kept to within - degrees Celsius through the use of solar energy only. 2). The Water Floor has good performance regarding both heat storage and in decreasing room temperature difference. In this paper experiments and simulation results relating to the thermal performance of this test house, under condition in which the auxiliary heating system operates are discussed. The energy consumption for space heating and PV power generation in particular are discussed from the point of view of -energy consumption. 2. OUTLINE OF THE TEST HOUSE AND SOLAR FLOOR HEATING SYSTEM 2.1 Test House The test house was built in the testing field of the Tokyo Metropolitan University campus, which is located to the west of Tokyo. Figure 1 shows the outside view of the test house, Figure 2 shows the section of the test house and schema of this solar Figure 1. Outside view of the test house Air inlet PV cell collector Air outlet Water floor Floor duct Vertical duct Figure 2. heating system and section of the test house

2 Plea24 - The 21 st Conference on Passive and Low Architecture. Eindhoven, The Netherlands, September 24 Page 2 of 6 heating system and Figure 3 shows the plan of the test house. The test house consists of a wood-frame construction with a floor area of66 m2. The exterior walls and roof of this house are well insulated by the special thermal insulation board (phenol foam:.2w/mk). The insulation thickness of the walls and roof are 1mm, which is equal to about a 2 mm thick glass wool. The raft foundation concrete is insulated by 1mm of foam polystyrene (.38W/mK). The windows are double-glazed with wooden frames. The overall heat loss coefficient of the whole house per total floor area is 1.86 W/m2K, including a ventilation rate of.5 air change per hour. The roof material is an amorphous-type PV panel and its maximum generating power is 4.5kW. The PV system is connected to the main power grid, and the power generated by it is used for space heating, while the excess power is returned to the grid. 2.2 Water Floor The Water Floor is shown in Figure 4. The water bag, that is filled with water is made of vinyl adhered aluminium foil and installed between the joists in the floor, as shown in Figure 5. The cross section of the water bag used in the test house was mm wide by 9mm high and 2,7mm in length, while the quantity of water is about 4.6 tonnes and the total heat capacity about 5.4kW/K (8 W/Km2). The most important feature of the water bag is that the water translates the heat by natural circulation, so that there is little temperature difference in the Water Bag. The bags were installed in all floors except the bathroom, as shown in Figure 6. The vertical supply duct is located in the west side of the house and branches into three floor ducts under the floor space to warm up the water bags. 2.3 System Operation In wintertime, fresh air enters the air layer in the roof from the edge of the eaves and flows upward under the solar cell and solar collector while being heated by solar radiation, as shown in Figure 2. At the upper end of the roof, the heated air passes through the ridge duct and enters the vertical duct, which is located on the west side of the house. The vertical duct branches off into three floor ducts in the under floor space and the warm air passes through the floor ducts, distributing heat to the water bags. The air passes into the under floor space at the end of the floor ducts, and heats the concrete slabs in the under floor space. Finally, the warm air enters the room through the outlets, which are generally located near the windows. 3. PERFORMANCE OF THE SOLAR COLLECTOR AND PV CELL 3.1 Performance of the Collector Figure 7 shows the relationship between the daily solar radiation of the roof surface and the collected solar energy. In this test house, approximately 2% of the daily solar radiation of the roof surface was collected when the solar heating system was operated under conditions in which the air Lavator Wash Bathroom room y Vertical duct Corridor Western style room Kitchen Measurement point Figure 3: Plan of the test house and measurement points Warm air Heated by solar radiation Electric heater Thermal insulation panel Water bag Figure 4: Heating devices in the Water Floor Figure 5: Photograph of the heat storing water bags Vertical duct Water bag Heat generation panel Floor duct Joist Figure 6: Placement of the water bags and the floor ducts in the test house

3 Plea24 - The 21 st Conference on Passive and Low Architecture. Eindhoven, The Netherlands, September 24 Page 3 of 6 temperature of the ridge duct was over 3 degrees Celsius. 3.2 Performances of the PV Cell Figure 8 shows the relationship between the daily solar radiation and generated power by the PV cell. The experiment used winter measurement data from 2 to 24. The number of data is 145 and the correlation coefficient between the two values is RESULTS OF EXPERIMENTS IN CONDITIONS WITHOUT INTERNAL HEAT GENERATION 4.1 Outline of the Experiment In the winter of the year before last (22-23), two experiments were carried out using the test house. Table 1 shows the conditions of each experiment. The heat pump a ir-conditioner was operated under conditions in which the room temperature was lower than 2 degrees Celsius, while in the case of the solar heating system, the air temperature in the ridge duct was over 3 degrees Celsius. Table 1: conditions of the experiment Case 1 Case 2 heating Heat pump Air-conditioner Measurement period Room Temperature, Consumption, and PV Generation Figure 9 shows the living room temperature, hourly energy consumption of the air-conditioner, and daily PV generation in case 1. The living room temperature was generally kept above 2 degrees Celsius, and the swing of the room temperature was little. The temperature of the water bags is generally 2 degrees Celsius lower than the room temperature. The airconditioner was operated throughout the entire period even in the daytime. The occupants of the test house are well insulated. While the daily PV generation is greater than the daily energy consumption of airconditioner. Figure 1 shows the living room temperature, hourly energy consumption, and daily PV generation in case 2. On sunny days, the solar heating system was operated. The room temperature was higher than 2 degrees Celsius, and the air-conditioner was turned off, so that only the fan consumed. The water bag temperature rose about 3 degrees in the daytime, which means that some collected solar energy was stored in the water bags. At night, the Water Floor supplies the heat which was stored during the day, to the rooms, therefore the air-conditioner was also turned off until mid-night. As a result, the energy consumption of Case 2 is lower than that of case RESULTS OF EXPERIMENTS USING INTERNAL HEAT GENERATION 5.1 Outline of Experiment During the last winter season (23-24), three experiments were carried out under conditions in Collected solar energy [MJ/m2day] Figure 7: Relationship between daily solar radiation of the roof and collected solar energy PV Generatio [MJ/day] y = 2.574x R 2 = Daily solar radiation [MJ/m2day] Figure 8: Relationship between daily solar radiation and the power generated by the PV cell Figure 9: Temperature change and hourly energy consumption for space heating (Case 1) Daily solar radiation of the roof [MJ/m2day] Hourly energy consumption of air-conditioner 2/27 2/28 3/1 consumption of heat pump (MJ/day) Hourly energy consumption of air-conditioner consumption of fan 2/6 2/7 2/8 consumption of heat pump (MJ/day) consumption of fan (MJ/day) 2/27 2/ /6 2/ [W/m2] Figure 1: Temperature change and hourly energy consumption for space heating (Case 2) [W/m2]

4 Plea24 - The 21 st Conference on Passive and Low Architecture. Eindhoven, The Netherlands, September 24 Page 4 of Hourly energy consumption of fan /16 1/17 1/18 1/19 1/2 1/21 1/22 1/23 1/24 1/ 1/26 [W/m2] consumption of fan (MJ/day) 1/16 1/ /18 1/ /2 1/ /22 1/ /24 1/ Figure 11: Temperature change and hourly energy consumption for space heating (Case 3) Hourly energy consumption of air-conditioner /29 1/3 1/31 2/1 2/2 2/3 2/4 2/5 2/6 2/7 [W/m2] 1/29 1/3 1/31 2/1 2/2 2/3 2/4 2/5 consumption of heat pump (MJ/day) Figure 12: Temperature change and hourly energy consumption for space heating (Case 4) 2/ /12 2/13 Hourly energy consumption of fan 2/14 2/ 2/16 2/17 2/18 2/19 2/2 2/21 Figure 13: Temperature change and hourly energy consumption for space heating (Case 5) 2/22 2/23 2/24 2/ 2/26 2/27 2/28 2/ [W/m2] 1 3/1 which the test house was assumed to be occupied by a family of two. So the internal heat was generated by household appliances. Table 2 shows the experiment conditions and Table 3 the schedules of the internal heat generation by household appliances. We used electric light bulbs to simulate the internal heat Table 2: conditions of the experiment (23-24) Case 3 Case 4 Case 5 Time[h] (W) -5 1 Time[h] (W) 16 Air-con Internal heat Measurement period heating ditioner generation Table 3: Daily schedule of internal heat generation generated by household appliances. The operating conditions of the air-conditioner and solar heating system are the same as Case 1 and Case Room Temperature, Consumption, and PV Generation Figure 11 shows the living room temperature, hourly energy consumption of the air-conditioner, and daily PV generation in Case 3. The living room temperature was maintained at from 17- degrees Celsius by solar energy alone. Even in the early morning and on cloudy days, the living room temperature was maintained at above 17 degrees Celsius. The energy consumption of the fan was lower than 3MJ/day throughout the experiment. Figure 12 shows the results of Case 4. The living room temperature and the water bags temperature were kept above 2 degrees Celsius. The airconditioner was generally operated throughout the

5 Plea24 - The 21 st Conference on Passive and Low Architecture. Eindhoven, The Netherlands, September 24 Page 5 of Room temperature of Case B Room temperature of Case C Room temperature of Case A 1/1 1/6 1/11 1/16 1/21 1/26 1/31 Figure 14: Simulation results of room temperature in January (Case A, Case B, and Case C) 4 [W/m2] entire day and energy consumption was within - 35MJ/day. However, daily PV generation was larger than the energy consumption of the air-conditioner except on cloudy days. Figure 13 shows the results of Case 5. During the period of this experiment, the outdoor air temperature was higher than that of an average year in Tokyo. Therefore, the highest living room temperature was above 3 degrees Celsius, and there was no energy consumption except for the fan. consumption [MJ] consumption of heat pump air-conditioner consumption of fan PV Generation EXAMINATION OF ENERGY CONSUMPTION BY SIMULATION 6.1 Simulation Model The purpose of the simulation was to examine the energy consumption of this solar heating system throughout the winter season, by comparing two cases without Water Floor. Table 4 shows the simulation conditions. The floor plan and the thermal insulation level of the model house ware identical to the test house in every case. The model house was assumed to be occupied by a family of two. The schedule of internal heat generation is shown in Table 3. A ventilation rate of.5 air change per hour was assumed in all cases. Table 4: Simulation Cases Case A Plywood floor Case B Plywood floor Case C Type of floor Water Floor Air-con Internal heat Calculated heating ditioner generation period From December to February The winter season is designated from December 1 to March 31. The houses were assumed to be in Tokyo and the hour-by-hour standard weather data set for Tokyo was used as the climate data. The energy consumption can be obtained from the load by an easy hand calculation using the constant heating efficiency of the air-conditioner. To estimate the energy consumption of the airconditioner, we first calculated heat load and then converted it into the electric consumption of the airconditioner using its COP. The heat load was calculated based on the condition that the airconditioner maintains room temperature at not lower than 2 degrees Celsius in every case. It is assumed that the COP of the air-conditioner is 3.,and the energy consumption of the fan 12Wh/hour. Power generated by the PV system consumption [MJ] Case A Case B Case C PV Generation Figure : consumption Case A Case B Case C Figure 16: consumption mm 1mm mm was calculated using statistical data obtained from the experiments. The relationship between daily solar radiation and daily PV generation is shown in Figure Room Temperature, Consumption, and PV Generation Figure 14 shows the calculation results of the room air temperature of the three cases. The room temperature of case A was always kept at 2 degrees Celsius, because the air-conditioner alone controlled the room temperature. The room temperature of case B and case C was higher than 2 degrees Celsius in the daytime, because of the solar heating system. In Case C, some solar energy collected on the roof was stored in the Water Floor. As a result, the daytime temperature of case C is lower than that of case B, which had a Plywood floor and the energy consumption of the air-conditioner is lower than in

6 Plea24 - The 21 st Conference on Passive and Low Architecture. Eindhoven, The Netherlands, September 24 Page 6 of 6 case B during the night. consumption of the airconditioner is lower than in case B during the night. Figure shows the simulation results of energy consumption for space heating in three cases. consumption of case C, which has a Water Floor system and solar heating system, is MJ for the entire winter season. This is lower than the other two cases and reduced energy consumption for space heating by 58.8% compared with the base case (case A). The sum of PV generation is MJ during the winter season. This is larger than the energy consumption of case C, and it is also 89.5% of energy consumption of the base case (Case A). Figure 16 shows the results of the simulation, when the model house has three levels of building insulation. The examined thickness of insulation is 1mm, 5mm, and mm of phenol foam (.2W/mK). The result shows that by using the solar heating system with the Water Floor, PV generation is sufficient to provide energy consumption for space heating until the thickness of insulation is 5mm of phenol foam. 7 CONCLUSIONS Using the results of the experiments and simulation study of the test house, the thermal performance, especially the energy consumption of this system is examined. The results are summarized as follows. 1. Based on the condition that the test house had internal heat generation, the living room temperature was kept to within 17- degrees through the use of solar energy in the experiment period. In addition, when the auxiliary air-conditioner was operated, the living room temperature was maintained at above 2 degrees Celsius while the highest temperature was over 3 degrees Celsius. 2. The solar floor heating system with Water Floor might reduce the energy consumption for space heating in the test house, by 58.8% compared to the base case, which had no solar system and Water Floor. 3. In this test house, the PV generation is sufficient to provide energy consumption for space heating in Tokyo, and the simulation results show that the energy consumption for space heating accounts for 46.% of PV generation. REFERENCES [1] N. Sunaga, Y. Hori and Z. Xian, Thermal Perfomance of System with Water Floor. Proceedings of PLEA 22, pp (July 22) [2] Z. Xian, N. Sunaga and Y. Hori, Thermal Performance of Heating System with Water Floor Part2, Study on the effect of Water Floor and energy-saving performance of this system. Proceedings of PLEA 23, (November 23) [3] Z. Xian, N. Sunaga and Y. Hori, An Experimental Study on the Heating System with Water Heat- Storage Floor. Journal of Environmental Engineering (Transactions of AIJ), No.572, pp [4] M. Udagawa, T. Endo, and T. Murata. Studay on optimum use of solar thermal and PV systems in residential houses. Proceedings of JSES-JWEA Joint Conference(1993), pp (in Japanese) [5] N. Sunaga, N. Ito, X. Zhejun, Y. Hori and K. Muro, Study on the Water Heat-Storage Floor for Indoor Climate Control System by Part 1 The Aim of System and Experimental Model. Summaries of Technical Papers of Annual Meeting of Architectural Institute of Japan (21) D-2, [6] Z. Xian, N. Sunaga, N. Ito, Y. Hori and K. Muro, Study on the Water Heat-Storage Floor for Indoor Climate Control System by Part 2 Result of Winter Experiment. Summaries of Technical Papers of Annual Meeting of Architectural Institute of Japan (21) D-2, [6] Z. Xian, N. Sunaga, Y. Hori, K. Muro and J. Ma, Floor Heat Storage System for Indoor Climate Control by Natural. Proceedings of JSES/KSES Joint Conference (21) 247- [7] N.Ito, Y. Hori, S. Komano, M. Muramatsu and S. Maeda, Study on Winter Thermal Characteristics of Integrated House Planned with Air Collector and Power Generation on the Roof and Thermal Storage Aqua Bag under the Floor Part 1 Planning Outline of I-House build in KARUIZAWA. Summaries of Technical Papers of Annual Meeting of Architectural Institute of Japan (1999) D-2, [8] Y. Hori, N.Ito, S. Komano and S. Maeda, Thermal Environment of KARUIZAWA I-House Part 1 Measurement Result of 1999 Winter Season. Summaries of Technical Papers of Annual Meeting of Architectural Institute of Japan (2) D-2, ACKNOWLEDGEMENT This study forms part of the Tokyo Metropolitan University 21st Century Center of Excellence Program: Development of Technologies for Activation and Renewal of Building Stocks in Megalopolis.