Energy Conservation of Raft Foundation Water Thermal Energy Applied to Outside Air Conditioning Systems
Date Issued
2016
Date
2016
Author(s)
Chang, Chi-Tun
Abstract
The weather in summer Taiwan is not only hot but also very wet. Hence the requirement for air conditioning is also very high. This not only lead to high electricity cost but also a huge burden to environment. This research is based on the utilization of the raft foundation water of the buildings as shallow geothermal energy applied to outside air conditioning systems. Also we derive adequate mathematic models and compare it with experimental data to prove the validity of the mathematic model in the research. In order to popularize the design of raft foundation water used as shallow geothermal energy, this research calculated the economic benefit and the payback period of raft foundation water thermal energy systems and tried to derive optimize condition to maximize the efficiency, too. There are three different types of energy usage to pre-cool the air, including a new type of ground heat exchanger: air/raft foundation water heat exchanger, drawing water directly from the raft foundation to cooling coil for pre-cooling, and a combination of pre-cooling heat pump systems. Then we integrate the system into five different modes. Take the occupied dwelling in Eland as example, the system can reduce the air temperature efficiently to about 27℃. Besides, according to the calculation of the experimental data, it can save as high as 2150 TWD per month and reach the payback period only in 23 months, which is relatively short compared with the life of the building. As we compare the data calculated by the mathematic models with the experimental data, it is clearly seen that both dry bulb temperature and the humidity ratio have an average error at about 5%, with the maximum error not exceeding 9%. To utilize raft foundation water thermal energy even more efficiently, this research also calculate the effectiveness of air/raft foundation water heat exchanger and cooling coil and discover that when using raft foundation water for heat exchange, air/raft foundation water heat exchanger has better effectiveness and that we need to keep the temperature of inlet cooling water of the coil at above 15℃ to maintain the effectiveness of the cooling coil higher than 0.7 as combined with the pre-cooling heat pump systems. By substituting the outside air condition of Eland in 2015 from April to October into the mathematical model, we discover that the most energy saving mode of the systems is by simply using air/raft foundation water heat exchanger. By the study of the case, it is clear that the raft foundation water thermal energy can reduce the cooling capacity. But the water temperature may still get influenced by the outside air condition hardly if the raft foundation is built only a floor underground. To improve the cooling capacity of the raft foundation water thermal energy, the research provides another system to draw the deeper 22℃ underground water by a solar energy pump into the raft foundation. This system is still constructing now. We only complete the testing of pumping the underground water into tank 6. The result shows that it can truly reduce the temperature by about 2℃.
Subjects
shallow geothermal energy
air/raft foundation water heat exchanger
air handling units
pre-cooling
SDGs
Type
thesis
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