| Combined cooling and heat power system(CCHP) can apply to energy supply for a region, including power/heat/cooling supply. In this way energy can be effectively used. However, in order to meet load requirement, CCHP system often needs a big installed capacity while the heat/cooling load often fluctuates, which leads that the generator often works under partial load. Efficiency of the generator can be thus reduced. On the other hand, cooling/heating/power load of the regional building varies with the time. In other words, the demand for heat and power changes all the time while CCHP system has a relatively stable heat/power supply ratio. In result, CCHP system cannot match the heat/power requirement ration of the regional building. Exergy efficiency and Economy could be affected, which minimize advantage of graded energy using through CCHP. Considering problems described above, integration of CCHP and water source heat pump has been researched. In order to optimize the combined system based on annual dynamic condition, following aspects have been discussed:At first, thermal performance of system components have been analyzed. Thermal models for generator/ absorption component/ water source heat-pump and other major components under dynamic working conditions have been built which provide theoretical basis for energy analysis and optimization for the combined system.Secondly, using meteorological data of two hydrological stations for upper Yangzi river, correlation between water temperature and other meteorological factor as well as model optimization have been analyzed. It has achieved with a simplified model to modify water temperature for the combined system, and offered energy analysis and configuration optimization with reliable theory.Then, based on mathematical theory and physical model for the combined system model for system optimization has been built based on annual dynamic condition. Considering balanced relation between energy and water flow, an engineering application oriented calculation method has been acquired. A Matlab program has also been written for the calculation method.At last, verification with several engineering cases has been conducted for the combined system. In addition, configuration of combined system for pool purchase two types of combined system configuration, namely grid-connected and pool purchase system has been compared and analyzed.It comes to following conclusions:1. Under standard condition, performance of heat pump unit can characterized with a function with two variables, load rate of and inlet cooling water temperature. However power efficiency and heat recovery efficiency of natural gas generator can be characterized with a function of one variable. Under non-standard condition, correction factors based on standard condition can be introduced to realize the simulation.2. The research shows every one degree reduction in outlet temperature of chilled water will reduce cooling performance parameter by 3.5% and 2.9% for two different water heat pump under low temperature and full load operation mode. For absorption heat pump every one degree reduction in outlet temperature of chilled water will reduce cooling performance by about 4% to 5%. So compared with water heat pump, absorption heat pump has a higher attenuation with changing supply water temperature3. It comes up with a correlation between daily average water temperature and daily outdoor dry-bulb temperature. Daily average water temperature can be thus obtained to represent hourly inlet temperature. It meets both requirement for engineering calculation and engineering accuracy.4. Based on annual dynamic load and dynamic water temperature, model for combined system optimization has been built. It comes up with a widely adaptable solution method based on annual dynamic time-interval based optimized resolution method.5. Case study shows combined system has a better heat/power output ratio. In result, it matches heat/power requirement ration of a building better. The advantage of graded energy using can be thus better used. Compared to grid-connected system, combined system in forms of pool purchase increase generating capacity to 50%. It saves operational cost to about 30%. |
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