热电冷联产系统的能耗特性

Energy Consumption Performance of Combined Heat Cooling and Power System

从系统基础能源消耗角度建立联产系统相对于分产系统节能判断关系式,并以实际热电机组为例进行计算验证,探讨了热电比、热效率、性能系数等参数对联产系统能耗特性的影响,研究发现:热电联产及在此基础上的热电冷联产的节能需满足一定的条件,相对来讲,冷电联供节能条件较热电联产更为苛刻。热电比、热效率和性能系数对联产系统节能影响程度明显不同;在联产系统中多效吸收机的应用并不总能使联产系统节能率增加,即使满足节能条件,对系统节能率的提升数量级也很小;热电冷联产系统相对于分产系统不一定节能,但从能的梯级利用原理讲,联产与分产系统相比火用损的减少是绝对的,而这一部分火用损的差值是联产的收益,也是热电联产的本质所在,据此建立了新的热电分摊理论模型。

A mathematical model characterizing a tri-generation system through the condition of primary energy conservation compared to the separate production of heat, cooling and power was developed. The model was validated with actual plant performance data. The impacts of the changes in various factors（ratio of heat to power, energy utilization factor and absorption chiller COP） on the energy conservation of tri-generation were investigated in detail. The results indicate that it is not correct to state that rational use of energy is intrinsic for cogeneration and tri-generation. The necessary condition under which a substantial reduction of primary energy demand for combining cooling and power generation is stricter than that for cogeneration（CHP）. The amount of energy conserved strongly depends on the unit performance parameters namely ratio of heat to power and energy utilization factor, while the COP has little influence on the energy conservation. A multi-effect absorption refrigeration integrated into CHP system does not always lead to energy conservation. It is found that even the multi-effect absorption chiller can meet the demands of energy conservation for tri-generation system, the promotion for energy conservation is little. It is due to the facts that primary energy conservation of cogeneration as compared to the separate heat and power production is not unconditional, but exergy losses for cogeneration is absolutely decreased as compared to the separate production system on the basis of energy cascade utilization principle, which is also the physical essence of cogeneration. This leads to a rational allocation of primary energy to the coupled energy forms for cogeneration.