874:
17:
358:
436:
86:
869:{\displaystyle {\begin{cases}{\ce {M^{II}Fe2^{III}O4 + 3Al2O3 -> M^{II}Al2^{III}O4 + 2Fe^{II}Al2^{III}O4 + 1/2O2}}&{\ce {(Reduction)}}\\{\ce {M^{II}Al2^{III}O4 + 2Fe^{II}Al2^{III}O4 + H2O -> M^{II}Fe2^{III}O4 + 3Al2O3 + H2}}&{\ce {(Oxidation)}}\end{cases}}}
902:
The disadvantages of the ferrite cycles are: similar reduction and melting temperature of the spinels (except for the hercynite cycle as aluminates have very high melting temperatures), and slow rates of the oxidation, or
353:{\displaystyle {\begin{cases}{\ce {M^{II}Fe2^{III}O4 -> M^{II}O + 2Fe^{II}O + 1/2O2}}&{\ce {(Reduction)}}\\{\ce {M^{II}O + 2Fe^{II}O + H2O -> M^{II}Fe2^{III}O4 + H2}}&{\ce {(Oxidation)}}\end{cases}}}
426:
Like the traditional iron oxide cycle, the hercynite is based on the oxidation and reduction of iron atoms. However unlike the traditional cycle, the ferrite material reacts with a second metal oxide,
895:
The advantages of the ferrite cycles are: they have lower reduction temperatures than other 2-step systems, no metallic gasses are produced, high specific H
402:
temperature which produces the original ferrite material in addition to hydrogen gas. The temperature level is realized by using geothermal heat from
916:
991:
961:
1033:
1053:
1048:
1003:
Sheffe, Jonathan; Jianhua Li; Alan W. Weimer (2010). "A spinel ferrite/hercynite water-splitting redox cycle".
941:
921:
415:
41:
445:
95:
936:
926:
45:
899:
production capacity, non-toxicity of the elements used and abundance of the constituent elements.
53:
968:
931:
407:
25:
1012:
430:, rather than simply decomposing. The reactions take place via the following two reactions:
904:
73:
60:
and depending on the reaction conditions, dopant metals and support material forms either
887:). This leads to lower radiation losses, which scale as temperature to the fourth power.
427:
1042:
386:
The endothermic reduction step (1) is carried out at high temperatures greater than
1016:
992:
Sentech 2008-Analysis of geothermally produced hydrogen on the big island of Hawaii
57:
80:
steps. The steps of solar hydrogen production by iron based two-step cycle are:
16:
61:
411:
391:
372:
879:
The reduction step of the hercynite reaction takes place at temperature ~
52:
ions, particularly the reduction and oxidation between Fe and Fe. The
368:
364:
403:
380:
77:
15:
376:
49:
398:. The oxidative water splitting step (2) occurs at a lower ~
862:
346:
48:. It is based on the reduction and subsequent oxidation of
1034:
Solar hydrogen from iron oxide based thermochemical cycles
840:
824:
811:
791:
747:
731:
686:
627:
603:
558:
517:
504:
484:
324:
308:
264:
194:
134:
363:
Where M can by any number of metals, often Fe itself,
439:
89:
883:lower than the traditional water splitting cycle (
868:
352:
8:
394:cycle" is capable of temperatures as low as
20:Simplified diagram of the iron oxide cycle
847:
846:
839:
834:
823:
818:
810:
805:
800:
790:
785:
775:
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760:
746:
741:
730:
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715:
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650:
634:
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621:
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582:
572:
567:
557:
552:
542:
537:
527:
516:
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503:
498:
493:
483:
478:
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463:
453:
448:
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331:
330:
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263:
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193:
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164:
159:
144:
133:
128:
118:
113:
103:
98:
90:
88:
56:, or iron oxide, begins in the form of a
1005:International Journal of Hydrogen Energy
917:Cerium(IV) oxide-cerium(III) oxide cycle
953:
7:
14:
40:/FeO) is the original two-step
1017:10.1016/j.ijhydene.2010.01.140
854:
848:
753:
641:
635:
520:
338:
332:
270:
208:
202:
137:
1:
891:Advantages and disadvantages
72:The thermochemical two-step
1070:
870:
354:
64:or different spinels.
21:
942:Zinc zinc-oxide cycle
922:Copper-chlorine cycle
871:
355:
44:proposed for use for
19:
437:
416:solar thermal energy
87:
42:thermochemical cycle
1054:Hydrogen production
937:Sulfur-iodine cycle
927:Hybrid sulfur cycle
842:
826:
813:
793:
780:
749:
733:
720:
688:
675:
629:
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592:
560:
547:
519:
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326:
310:
297:
266:
196:
136:
123:
68:Process description
46:hydrogen production
1049:Chemical reactions
866:
861:
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781:
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26:chemical reactions
22:
853:
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510:
497:
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408:solar power tower
337:
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76:process uses two
1061:
1021:
1020:
1011:(8): 3333–3340.
1000:
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989:
983:
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980:
979:
973:
967:. Archived from
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864:
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857:
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843:
841:
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594:
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579:
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573:
569:
559:
556:
549:
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543:
541:
534:
532:
531:
528:
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518:
515:
508:
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502:
495:
485:
482:
475:
472:
469:
467:
460:
458:
457:
454:
450:
401:
397:
389:
359:
357:
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335:
327:
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315:
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255:
248:
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228:
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212:
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205:
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185:
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150:
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145:
141:
135:
132:
125:
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100:
30:iron oxide cycle
1069:
1068:
1064:
1063:
1062:
1060:
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1058:
1039:
1038:
1030:
1025:
1024:
1002:
1001:
997:
990:
986:
977:
975:
971:
964:
960:
959:
955:
950:
913:
905:water splitting
898:
893:
884:
880:
860:
859:
844:
756:
696:
651:
647:
646:
631:
568:
523:
449:
441:
435:
434:
424:
422:Hercynite cycle
414:to collect the
399:
395:
387:
344:
343:
328:
273:
238:
218:
214:
213:
198:
160:
140:
99:
91:
85:
84:
74:water splitting
70:
39:
35:
12:
11:
5:
1067:
1065:
1057:
1056:
1051:
1041:
1040:
1037:
1036:
1029:
1028:External links
1026:
1023:
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995:
984:
962:"Project PD10"
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929:
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845:
837:
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799:
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788:
773:
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713:
694:
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683:
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624:
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566:
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540:
522:
514:
501:
492:
489:
481:
466:
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428:aluminum oxide
423:
420:
390:, though the "
361:
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334:
329:
321:
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305:
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1018:
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985:
974:on 2009-02-05
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963:
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943:
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938:
935:
933:
930:
928:
925:
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918:
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914:
910:
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888:
835:
827:
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771:
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681:
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622:
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598:
583:
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561:
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538:
512:
499:
490:
487:
479:
464:
442:
433:
432:
431:
429:
421:
419:
417:
413:
410:and a set of
409:
405:
393:
384:
382:
378:
374:
370:
366:
319:
311:
303:
288:
259:
251:
234:
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156:
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114:
92:
83:
82:
81:
79:
75:
67:
65:
63:
59:
55:
51:
47:
43:
31:
27:
18:
1008:
1004:
998:
987:
976:. Retrieved
969:the original
956:
907:, reaction.
901:
894:
885:1200 °C
878:
425:
400:1000 °C
396:1200 °C
388:1400 °C
385:
362:
71:
29:
23:
881:200 °C
1043:Categories
978:2008-12-19
948:References
932:Hydrosol-2
412:heliostats
383:thereof.
852:Oxidation
754:⟶
639:Reduction
521:⟶
392:Hercynite
336:Oxidation
271:⟶
206:Reduction
138:⟶
911:See also
381:mixtures
62:Wüstites
54:ferrites
58:spinel
28:, the
972:(PDF)
965:(PDF)
406:or a
404:magma
78:redox
50:iron
24:For
1013:doi
777:III
717:III
672:III
589:III
544:III
470:III
379:or
294:III
120:III
32:(Fe
1045::
1009:35
1007:.
803:Al
768:Fe
762:II
708:Al
702:II
698:Fe
663:Al
657:II
580:Al
574:II
570:Fe
535:Al
529:II
496:Al
461:Fe
455:II
418:.
377:Zn
375:,
373:Mn
371:,
369:Ni
367:,
365:Co
285:Fe
279:II
244:II
240:Fe
224:II
166:II
162:Fe
146:II
111:Fe
105:II
1019:.
1015::
981:.
897:2
855:)
849:(
836:2
832:H
828:+
820:3
816:O
807:2
798:3
795:+
787:4
783:O
772:2
758:M
751:O
743:2
739:H
735:+
727:4
723:O
712:2
693:2
690:+
682:4
678:O
667:2
653:M
642:)
636:(
623:2
619:O
614:2
611:1
607:+
599:4
595:O
584:2
565:2
562:+
554:4
550:O
539:2
525:M
513:3
509:O
500:2
491:3
488:+
480:4
476:O
465:2
451:M
443:{
339:)
333:(
320:2
316:H
312:+
304:4
300:O
289:2
275:M
268:O
260:2
256:H
252:+
249:O
235:2
232:+
229:O
220:M
209:)
203:(
190:2
186:O
181:2
178:1
174:+
171:O
157:2
154:+
151:O
142:M
130:4
126:O
115:2
101:M
93:{
38:4
36:O
34:3
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