固体氧化物燃料电池冷热电三联供系统及其性能分析

Solid Oxide Fuel Cell Trigeneration System and Performance Analysis

冷热电三联供系统可以提高一次能源利用效率,固体氧化物燃料电池(solid oxide fuel cell,SOFC)由于工作温度高、清洁等特点可以很好地作为冷热电三联供系统的顶层循环,针对SOFC尾气具有大量高温余热的特点,提出了一种以温差发电器(thermoelectric generator,TEG)为中间循环回收SOFC尾气余热的冷热电三联供系统,该系统包括内部重整SOFC、后燃室、温差发电器和溴化锂吸收式冷热水机组,实现了废热的梯次利用,极大地提高了混合系统能源利用效率.基于建立的各部件数学模型,研究了循环水利用形式对系统性能的影响,为系统节能节水提供了新的方向;分析了温差发电器面积、燃料流量、空气流量的变化对系统输出功率的影响,为系统最优工况的确定提供了相关参考.结果表明:采用系统C的水循环利用形式时SOFC冷热电三联供系统总效率相对最大,在设计工况下,混合系统C在制热工况下总效率可达到94%,在制冷工况下总效率约为65%;温差发电器面积的增加会导致温差发电器输出功率的增加,系统整体效率减小;随着燃料流量的增加,温差发电器输出功率逐渐增加,SOFC发电功率呈现先增加后减小的趋势,系统的整体效率逐渐增大;随着空气流量的增加,温差发电器输出功率逐渐减小,SOFC发电功率先增加后减小,而系统的整体效率先减小后逐渐增加.

Trigeneration systems can improve the efficiency of primary energies.Solid oxide fuel cells(SOFC)can be incorporated in the top cycle of trigeneration systems due to their high working temperature and cleanliness.Considering the large amount of waste heat in SOFC exhaust gas,a trigeneration system with a thermoelectric generator in the intermediate cycle to recover the waste heat of SOFC exhaust was proposed.The trigeneration system in this study included an internal reforming SOFC,an afterburner,a thermoelectric generator,and a lithium bromide absorption chiller and hot water unit,which realized the reuse of waste heat and greatly improved the energy efficiency of the system.Based on the established mathematical models of all units,the influence of the circulating water utilization forms on the system performance was further studied,providing a new perspective on energy saving and water sav-ing.The influence of the area of the thermoelectric generator,the fuel flow,and the air flow on the system output power was analyzed,providing a reference for determining the optimal operating conditions of the system.Results indicated that the highest total efficiency of the SOFC trigeneration system was achieved by adopting the water recycling form C with the total efficiency reaching 94%and 65%at heating and cooling conditions,respectively.With the increasing area of the thermoelectric generators,the increase of the thermoelectric generator output power reduced the overall efficiency of the system.Meanwhile,with increasing fuel flow rate,the thermoelectric generator output power gradually increased and the SOFC power generation exhibited a trend of initially increasing and then decreas-ing.The overall efficiency of the system gradually increased.With increasing airflow rate,the thermoelectric genera-tor output power gradually decreased.The SOFC power generation first increased and then decreased,while the overall efficiency of the system first decreased and then gradually increased.