可再生氢能应用前景 -- 氢的制取

泥等含固体的
体系有较强适应性, 缺点是生物质物料不易混合均匀, 不易均匀地达到超临界水下所需
的压力和温度, 也不能实现连续生产,. 连续式反应器则可以实现连续生产, 但反应时间
短, 不易得到中间产物, 难以分析反应进行的情况, 因此今后需要进行大量的研究, 研
制出更加有效的反应器以及寻求不同生物质在不同参数下的最佳气化效果, 实现高效,
经济的气化过程.
4. 其他制氢技术
除热化学方法外, 生物质还可以通过发酵的方式转化为氢气和其他产物. 此外,
微藻等水生生物质能够利用氢酶(Hydrogenase)和氮酶(Nitrogenase)将太阳能转化为
化学能-氢. 这些生物制氢技术具有良好的环境性和安全性, 但还处于早期的研究阶段,
制氢基理还未透彻理解, 尚需大量的研究工作.
太阳能半导体光催化反应制氢也是目前广泛研究的制氢技术. TiO2 及过渡金属氧化
物, 层状金属化合物如K4Nb6O17, K2La2Ti3O10, Sr2Ta2O7 等, 以及能利用可见光的催化
材料如CdS, Cu-ZnS 等都经研究发现能够在一定光照条件下催化分解水从而产生氢气.
但由于很多半导体在光催化制氢的同时也会发生光溶作用, 并且目前的光催化制氢效
率太低, 距离大规模制氢还有很长的路要走. 尽管如此, 光催化制氢研究仍然为我们
展开了一片良好的前景.
5. 制氢技术总结以及在香港的应用前景
前面讨论了利用可再生资源制取清洁燃料-氢的各项主要技术. 这些技术的特点,
经济性, 环境

和安全方面的特点总结于表4.
表4. 利用可再生资源制氢技术比较
Table 4. Characteristics of candidate hydrogen production technologies
PV-Electrolysis Wind-Electrolysis Solar Thermochemical Cycle Biomass Conversion
Development
status
PV technology almost mature,
electrolysis mature,
Some demonstrations of
PV-electrolysis system been done
Wind system mature, electrolysis mature,
wind-electrolysis demonstration needed
R&D Pyrolysis and gasification R&D, biological
processes at early R&D
Efficiency PV efficiency:
First generation, 11-15%,
Second generation, 6-8%
Solar to hydrogen around 7%
36% from wind to hydrogen, assuming wind
to electricity efficiency of 40% and
electrolyzer 90%
29% for Zn/ZnO cycles Conversion ratio up to 100% can be
achieved for gasification, efficiency of
10% for biological processes
Economic
consideration
Hydrogen cost about US$40-53.73/GJ
depends on the PV type, the size
Hydrogen cost about US$20.2/GJ,
corresponding to 7.3cents/kWh
US$0.13-0.15/kWh, equivalent to
US$36.1-41.67/GJ
US$6.67-17.1/GJ for thermochemical
conversion depends on biomass types,
capacity size, for biological processes,
remain to be demonstrated
Environmental
consideration
Almost no pollution emission during
operation, energy consumption
intensive during construction, disposal
of hazardous materials
No pollution during operation, construction
energy consumption intensive, some noise
during operation
Emission of hydrogen sulfide, use and
disposal of metal oxide, reactors
Whole cycle CO2 neutral, some pollution
emission during the stage of constructing
reactors
Safety
consideration
Handling hazardou

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