Study On The Passive Solar Heating Building In Tibet

The important significance of using solar heating building in Tibet is introduced by analyzing the available fossil energy, the character of climate, the thermal insulation of existing building and the status of solar energy utilization. Both considering the demand of designing solar heating system in Tibet and the research status of passive solar building, the numerical simulation and field experiment is used to study the issues of designing passive solar building in Tibet. There are three issues are studied in this thesis, which are how to design the passive solar building dynamically; how to modify the auxiliary heating load effected by the high intensity solar radiation and how to choose the heating terminal in high intensity solar radiation area.After theoretically analyzing the influencing factors of solar building dynamical thermal process, we establish the mathematical-physical model of solar building and introduce the theories of solving Z-transfer coefficient through using state-space method and solving the transient heat transfer by Z-transfer function. In order to select a suitable studied tool, the characteristic and application scope of different building energy analysis programs are compared, the result show that EnergyPlus is suitable to be used to study passive solar building, and the comparative testing andexperiment testing methods are used to verify the reliability of this program.In the study of dynamic optimized design for passive solar house, with begin to, an overview and analysis of domestic and aboard indoor thermal comfort indices in the published literature is conducted. And the indoor thermal comfort criterion on passive solar house is determined in consequence. Whereafter, the model of building, which is representative to some extent, is present on the sensitivity analysis of primary characteristic parameters (encompass building towards, building depth, building width) on the geometry model of the buildings. Based on this building model, the key thermal parameters of solar buildings (parameters such as thermal resistance of the south wall, outer wall thermal quality and so on) are analyzed with dynamic simulation method. The consequence of analysis on the effect of thermal insulation of the south wall demonstrated that, at high solar radiation region, although the increase of south wall thermal insulation lessen its gained heat at the daytime, it can lessen the heat loss at night, even the quantity of latter is larger than that of the former. Thereforth, the increasing thermal insulation of south wall is in favor of improving indoor thermal environment of solar building in daily period. On the other hand, the results of analyzing external wall thermal mass indicates that, the effect of wall thermal mass on indoor temperature fluctuation is remarkable when the the thermal insulation of external wall is very poor; whereas indoor temperature fluctuation is mainly affected by heat storage and discharging performance of direct solar radiation and the dominant weight of influence from the wall thermal mass is reduced when the external wall thermal insulation is improved to some extent. On the basis of the previous analysis, the indoor thermal environment of the model building is calculated at various conditions of diffrent sunshine rate and diffrent solar radiation intensity by using dynamic simulation method. Minimum limited values of outdoor mean temperature related to different solar radiation resource are obtained when the indoor temperature satifiies the thermal comfort criterion of passive solar house. It also presented diagrams of temperature difference between indoor and outdoor and indoor temperature fluctuation, which are available to guide the design of passive solar building. Besides, potential of passive heating supply for mostly cities in Tibet plateau region was analyzed using calculated result and realizable areas for zero auxiliary heating passive heating are present.In the investigation of the correction for design load of auxiliary heat source of passive solar houses come from high solar radiation intensity, this study analyzed the effect of building thermal mass on correction for indoor design load. It could be concluded that, wall thermal mass plays a poor impact on the correction for room heat load when the external wall thermal insulation is fairly good; it was feasible to make a correction simplification to solar buildings which have good thermal insulation, regardless of the effect by external wall thermal mass on corrected coefficient. Furthermore, it put forward that the corrected model of load for auxiliary heat source resulted from solar radiation could be divided into two components, namely, transparent envelope and non-transparent envelope. For the non-transparent envelope, the corrected coefficient of whose heat transfer quantity equals to the ratio of mothly average temperature difference between indoor air tempeature and outdoor average comprehensive temperature and mothly air temperature difference between indoor average air tempeature and outdoor average air temperature; as for transparent maintenance structure, the corresponding corrected coefficient is 0.9 times as much as the mothly average heat gain of solar radiation through o window.When it comes to the study of the effect of solar radiation intensity on the selection of auxiliary heat source terminals, indoor thermal comfort and energy consumption of different heating terminal (floor radiator heating, convective radiator heating) are analyzed. And we could get that, at areas with high solar radiation, when only feedback control of indoor temperature is used in the heating system, serious indoor overheat will appear with floor radiation heating system; at the same time, the energy consumption of which is also larger than the chamber with radiator heating. Hence, when floor radiation heating system is used in severe cold and cold region with high solar radiation intensity, a comprehensive consideration should be taken with the factors such as local solar radiation intensity, building envelope, temperature difference between indoor and outdoor, building room scale and so on. It can't be simply assumed that heating systems with low temperature floor radiation are superior to heating systems with radiator.In order to make up for the shortcoming of lower reliability of simulation analysis with computer, field measurement at four aspects, i.e., outdoor weather data, existing building indoor thermal environment, building thermal processes of various heating system and indoor thermal environment of new passive solar houses in Tibet region, are executed. The four aspects of analysis were as follow. Firstly, from the testing result of outdoor weather data, we can find that although indoor temperatures in various areas of Tibet are quite different, source of solar energy at various areas is extremely abundant, which demonstrates it's very suitable to create solar energy building in Tibet region. Secondly, the analysis of field measurement on indoor thermal environment for existing non-heating building disclose that, indoor temperatures of existing buildings with quite poor thermal insulation are yet adjacent to the thermal comfort criterion on passive solar building, which indicates using passive solar heating has tremendous potential in the region and zero auxiliary heat source can be realized. Thirdly, the testing results of dynamic thermal processes of buidling in various heating system show that, the thermal mass of radiator heating is large, and the computation results of tendency of indoor temperature change are fairly accordance with that from various auxiliary heat source terminal forms, which verified the correctness of corresponding computation results. Finally, the comparison between measurement of passive solar building and simulation results reveals that, range and tendency of indoor temperature variety got by numerical simulation are basically coincide with that got by field measurement, which demonstrates the mathematical-physical model used in the study is reliable and the computation precise is satisfied with demands of engineering applications.