气相低温高压储氢密度和能耗的理论分析及比较

The storage of hydrogen based on low-temperature and high-pressure method

如何安全、高效、经济地储存氢气已成为氢能利用进一步发展的瓶颈.传统储氢手段,如室温高压储氢、液化储氢、金属氢化物储氢等存在或储氢密度低、或液化功率高、或需高温加热再生释氢等问题.为此,本文提出一种在氢气临界压力之上的低温高压储氢方式,可在压力不必太高,温度不必太低的情况下实现储氢释氢过程.分析发现,综合储氢密度及储氢能耗, 3种物理储氢方法优劣为:低温高压储氢>室温70 MPa储氢>液化储氢;在储氢压力10 MPa以上存在单位储氢能耗下的储氢密度极大值.本文推荐低温高压储氢参数为:50 MPa,100 K;45 MPa,100 K;40 MPa, 90 K;35 MPa, 80 K;30 MPa, 70 K,其储氢密度在62.3~65.3 kg/m^3之间.

Hydrogen storage method with high security,reliability and economy is the bottleneck of large-scale hydrogen utilization.Conventional techniques such as high-pressure gaseous storage(HPGS),liquid hydrogen storage(LHS),solid hydrogen storage(SHS,mainly dominated by metal hydrides based method)have their own disadvantages.For examples,HPGS needs so much high pressure that the security risk is created,even though the density is still unsatisfactory;LHS consumes so much power though it is the potential great way to achieve both high volume hydrogen storage density and mass hydrogen storage density;SHS needs lots of time and high temperature to storage/release,moreover practical application of metal hydrides is still not available.In this paper,a method by combining low-temperature and high-pressure technologies is proposed,which can achieve high density at not very low temperature and not very high pressure.The SRK equation is chose for describing the thermodynamic properties of hydrogen,since it agrees well with Refprop 9.1.Then the power consumption of compressors and fans in multistage hydrogen compression process is analyzed,showing that five stage compression is the best choice comprehensively considering the power consumption and the complexity of the compression.Meanwhile,the thermal load of hydrogen is analyzed in the cooling process from 300 to 20 K,revealing that the latent heat consumes about 54%of the total power consumption,though it only occupies 12%of the total thermal load.This is the essential reason why the proposed method is superior to LHS on power consumption.From the thermodynamic calculation we can conclude that:(1)Synthetically considering the hydrogen storage density and the total power consumption,the proposed method,that is gaseous low-temperature and high-pressure storage(GLTHPS),is better than HPGS and LHS;(2)there exists a maximumψ(defined by hydrogen density divides total power consumption)at pressure above 10 MPa,and temperature below 120 K,meanwhile,the pressure increases with the temperature at the maximumψ;(3)the recommended temperature and pressure parameters for hydrogen storage are(50 MPa,100 K),(45 MPa,100 K),(40 MPa,90 K),(35 MPa,80 K)and(30 MPa,70 K),at which the density of hydrogen ranges from 62.3 to 65.3 kg/m^3,andψranges from 1.83 to 2.04.The optimized region for hydrogen storage is very practical,since both the mixed-refrigerants Joule Thomson refrigeration cycle(MJTR)and Reverse Brayton cycle(RBC)can achieve high efficiency at the temperature ranging from 150 to 70 K.The proposed method can well meet large-scale and low-cost requirement of hydrogen storage.Inevitably,the vessel used for low-temperature and high-pressure hydrogen storage must be specially designed,which is the biggest weakness of the proposed method.It will raise the initial cost,but decrease the operating cost significantly.