Power generation system

1. A power generation system comprising:

a power generation unit including a combustor;

a casing that accommodates said power generation unit;

a ventilator that ventilates an interior of said casing;

a first gas flow passage, arranged inside said casing, for a flow therethrough of gas which flows as said ventilator operates;

a second gas flow passage, arranged inside said casing, for a flow therethrough of combustion exhaust gas from said power generation unit;

wherein within said casing, said second gas flow passage merges into said first gas flow passage, and wherein said ventilator is disposed more upstream than a merging point of said first and second gas flow passages in said first gas flow passage.

2. The power generation system as set forth in claim 1 , further comprising a condenser on said second gas flow passage, wherein said second gas flow passage merges into said first gas flow passage at a point more downstream than said condenser.

3. The power generation system as set forth in claim 1 , further comprising a controller that controls an operation of said ventilator so that its discharge pressure becomes higher than a pressure of gas at said merging point.

4. The power generation system as set forth in claim 1 , wherein said ventilator operates in such a manner that its discharge pressure becomes higher than a pressure of gas at the merging point.

5. The power generation system as set forth in claim 1 , wherein said the combustor combusts combustible gas and wherein said second gas flow passage is a gas flow passage through which combustion exhaust gas from said combustor flows.

6. The power generation system as set forth in claim 5 , further comprising a controller that controls, at the time of shutting down said power generation system, said ventilator to continue to operate at least until said combustor stops its combustion operation.

7. The power generation system as set forth in claim 5 , further comprising:

a combustion air supply device that supplies combustion air to said combustor, and

a controller that controls, at the time of shutting down said power generation system, said ventilator to operate at least after said combustion air supply device stops operating.

8. The power generation system as set forth in claim 5 , further comprising:

a combustion air supply device that supplies combustion air to said combustor, and

a controller that controls, at the time of shutting down said power generation system, said combustion air supply device to operate even after said combustor stops its combustion operation.

9. The power generation system as set forth in claim 1 , wherein said power generation unit further includes a fuel cell, and a cathode off-gas flow passage through which cathode off-gas from said fuel cell flows, wherein said second gas flow passage comprises a combustion exhaust gas flow passage through which combustion exhaust gas from said combustor flows, and wherein the combustion exhaust gas flow passage and the cathode-off gas flow passage merge with the first gas flow passage.

10. The power generation system as set forth in claim 9 , further comprising:

an oxidizing gas supply device that supplies oxidizing gas to said fuel cell, and

a controller that controls, at the time of shutting down said power generation system, said power generation system to stop generating electric power while controlling said oxidizing gas supply device to operate even after said combustor stops its combustion operation.

11. The power generation system as set forth in claim 1 , further comprising a controller that controls said ventilator to operate at least during a time in which said power generation system operates to generate electric power.

12. The power generation system as set forth in claim 1 , further comprising a controller that controls, at the time of shutting down said power generation system, said ventilator to continue to operate at least until discharge of combustion exhaust gas from said power generation unit stops.

13. The power generation system as set forth in claim 1 , further comprising a controller that controls, at the time of shutting down said power generation system, said ventilator to continue to operate at least after the discharge of combustion exhaust gas from said power generation unit stops.

14. The power generation system as set forth in claim 1 , wherein said first gas flow passage is arranged such that it extends to outside said casing so to merge into a combustion exhaust gas flow passage of an external combustion device.

15. The power generation system as set forth in claim 1 , wherein said power generation unit further comprises a fuel cell, and the combustor combusts anode off-gas from said fuel cell.

16. The power generation system as set forth in claim 1 , wherein the first gas flow passage couples a ventilation gas output by the ventilator directly to the merging point.

17. A power generation system comprising:

a power generation unit;

a casing that accommodates said power generation unit;

a ventilator that ventilates an interior of said casing;

a first gas flow passage arranged inside said casing, the first gas flow passage receiving a ventilation gas output by the ventilator; and

a second gas flow passage arranged inside said casing, the second gas flow receiving a combustion exhaust gas output by power generation unit;

wherein within said casing, the first gas flow passage is merged with the second gas flow passage at a merging point downstream of the power generation unit such that the ventilation gas is merged with the combustion exhaust gas downstream of the power generation unit.

18. The power generation system as set forth in claim 17 , wherein the ventilation gas is an atmospheric gas.

19. The power generation system as set forth in claim 17 , wherein the first gas flow passage couples the ventilation gas directly to the merging point.