Heat-power coupled electrolytic hydrogen production system with low-temperature waste heat recovery and its performance evaluation
During hydrogen production by solid oxide electrolysis,water is electrolyzed in the form of steam,but the heat energy released from electrolysate through cooling is not sufficient for feed water evaporation,which results in a heating gap in the electrolytic hydrogen production system.To address this problem,this paper proposes a systematical process method to meet the heat demand of feed water evaporation.In this method,the high-temperature heat pump technology is used,which applies a heat pump to absorb external low-temperature waste heat(<100℃)to produce high-temperature heat energy(>100℃).A systematical procedure is designed.In addition,the influences of key parameters of the heat pump system on the system performance are studied,and the hydrogen production performance of this system is evaluated by means of modeling and simulation.And the following research results are obtained.First,the proposed system applies a heat pump to absorb ambient low-temperature waste heat to produce high-temperature heat energy for the evaporation of electrolysis feed water,which indicates its technological feasibility.This method is also applicable in recovering the waste heat carried by the elecrolysate inside the system.Second,the energy consumption of hydrogen production decreases as ambient waste heat temperature increases.The heat demand to the waste heat source is 138 kW for the electrolytic hydrogen production unit with 1 MW of DC electrolysis power.When the waste heat source is water and its temperature drop is 5℃,the demand rate of water is about 20 t/h.Third,if it is assumed that the ambient waste heat is excluded from the energy consumption of hydrogen production and is integrated by using a heat pump,the theoretical specific energy consumption of hydrogen production is about 3.5 kW·h/m3,all of which is electricity.In conclusion,the system process which applies a heat pump to absorb low-temperature waste heat to supply heat for the high-temperature electrolytic hydrogen production system provides a new idea,means and method for converting low-grade waste heat into high-grade hydrogen energy,presenting a promising application prospect.
High temperature electrolysisSolid oxide electrolysisHydrogen productionLow-grade waste heatWaste heat recoveryHeat integrationHeat pumpModeling simulation
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