received by the International Bureau on 29 July 2013 (29.07.13)

1. A method for reforming hydrocarbon gas, the method comprising:

stripping from the hydrocarbon gas at least most of gaseous impurities selected from the group consisting of hydrogen sulfide, siloxanes, volatile organic compounds other than hydrocarbons, and halogenated volatile organic compounds, in order to provide stripped hydrocarbon gas including carbon dioxide;

reacting the stripped biogas in a solar radiation receiving reactor that includes a solar radiation transparent window and having a catalyst that is heated by concentrated solar radiation impinging thereon via said window, thereby providing an output gas mixture comprising hydrogen gas and carbon monoxide;

cooling said solar radiation transparent window to help prevent deposition of carbon thereon; and

causing at least one of steam and carbon dioxide to flow alongside an inner surface of said solar radiation transparent window to help prevent deposition of carbon thereon.

2. A method for reforming hydrocarbon gas according to claim 1, further comprising:

compressing the stripped biogas, to provide compressed stripped biogas, prior to said reacting.

3. A method for reforming hydrocarbon gas according to claim 1 and also comprising:

adding at least one of steam and carbon dioxide to said stripped hydrocarbon gas when the molar ratio of carbon dioxide to hydrocarbon gas in said stripped hydrocarbon gas is below a preferred molar ratio, thereby providing oxygen- enhanced stripped hydrocarbon gas for supply to said solar radiation receiving reactor.

4. A method for reforming hydrocarbon gas according to claim 1 and wherein said stripping includes adsorption on at least one material selected from the group consisting of activated carbon, alumina, clay, ZnO nanoparticles, molecular sieves, and polymer beds.

5. A method for reforming hydrocarbon gas according to claim 1 and wherein said stripping includes the use of water or a liquid catalyst containing ferric ions.

6. A method for reforming hydrocarbon gas according to claim 1 and wherein said stripping includes the use of a cold trap.

7. A method for reforming hydrocarbon gas according to claim 1 and further comprising stripping excess water from said output gas mixture.

8. A method for reforming hydrocarbon gas according to claim 1 and further comprising stripping excess carbon dioxide from said output gas mixture.

9. A method for reforming hydrocarbon gas according to claim 1 and further comprising ascertaining a composition of said output gas mixture and controlling a flow rate of said output gas mixture.

10. A system for reforming hydrocarbon gas comprising:

a first stripping unit for stripping from the hydrocarbon gas at least most of gaseous impurities selected from the group consisting of hydrogen sulfide, siloxanes, volatile organic compounds other than hydrocarbons, and halogenated volatile organic compounds, in order to provide stripped hydrocarbon gas including C0₂;

a solar radiation receiving reactor, for reacting the stripped hydrocarbon gas, including a solar radiation transparent window having a catalyst that is heated by concentrated solar radiation impinging thereon via said solar radiation transparent window, thereby providing an output gas mixture comprising hydrogen gas and carbon monoxide;

a mechanism for cooling said solar radiation transparent window to help prevent deposition of carbon thereon; and

a mechanism for causing at least one of steam and carbon dioxide to flow alongside an inner surface of said solar radiation transparent window to help prevent deposition of carbon thereon.

11. A system for reforming hydrocarbon gas according to claim 10 and also comprising:

a compressor for compressing the stripped hydrocarbon gas to provide compressed stripped hydrocarbon gas.

12. A system for reforming hydrocarbon gas according to claim 10 and also comprising:

a conduit and a valve for adding at least one of steam and carbon dioxide to said stripped hydrocarbon gas when the molar ratio of carbon dioxide to hydrocarbon gas in said stripped hydrocarbon gas is below a preferred molar ratio, thereby providing oxygen-enhanced stripped hydrocarbon gas for supply to said solar radiation receiving reactor.

13. A system for reforming hydrocarbon gas according to claim 10 and wherein said first stripping unit employs adsorption on at least one material selected from the group consisting of activated carbon, alumina, clay, ZnO nanoparticles, molecular sieves, or polymer beds.

14. A system for reforming hydrocarbon gas according to claim 10 and wherein said first stripping unit employs water or a liquid catalyst containing ferric ions.

15. A system for reforming hydrocarbon gas according to claim 10 and wherein said first stripping unit includes a cold trap.

16. A system for reforming hydrocarbon gas according to claim 10 and also comprising:

a second stripping unit for stripping excess water from said output gas mixture.

17. A system for reforming hydrocarbon gas according to claim 10 and also comprising:

a second stripping unit for stripping excess carbon dioxide from said output gas mixture.

18. A system for reforming hydrocarbon gas according to claim 10 and also comprising:

a mechanism for ascertaining a chemical composition of said output gas mixture; and

a flow controller for controlling a flow rate of said output gas mixture.

19. A method for reforming hydrocarbon gas, the method comprising:

reacting the hydrocarbon gas with at least one of steam and carbon dioxide in a solar radiation receiving reactor which includes a catalyst and a solar radiation transparent window for allowing concentrated solar radiation to impinge directly on said catalyst, thereby providing an output gas mixture comprising hydrogen gas and carbon monoxide; and

maintaining transparency of said window to said concentrated solar radiation by causing at least one of steam and carbon dioxide to flow alongside said window, generally to exclude the presence of the hydrocarbon gas thereat.

20. A method for reforming hydrocarbon gas according to claim 19 and further comprising ascertaining a composition of said output gas mixture and controlling a flow rate of said output gas mixture.

21. A system for reforming hydrocarbon gas comprising:

a solar radiation receiving reactor which includes a catalyst and a solar radiation transparent window for allowing concentrated solar radiation to impinge directly on said catalyst, said reactor receiving the hydrocarbon gas and at least one of steam and carbon dioxide and providing an output gas mixture comprising hydrogen gas and carbon monoxide; and

a mechanism for maintaining transparency of said window to said concentrated solar radiation by causing said at least one of steam and carbon dioxide to flow alongside said window, generally to exclude the presence of the hydrocarbon gas thereat.

22. A system for reforming hydrocarbon gas according to claim 21 and also comprising: a mechanism for ascertaining a chemical composition of said output gas mixture; and

a flow controller for controlling a flow rate of said output gas mixture.