Power generation system, and maintenance method for power generation system

A maintenance method for a power generation system comprising:

• a medium circuit comprising:
• a circulation pump configured to circulate a medium with a boiling point lower than a boiling of water through the medium circuit;
• an evaporator configured to heat the medium using heat of an external source and thereby evaporate the medium;
• a plurality of expanders configured to be driven using the medium evaporated by the evaporator;
• and
• a condenser configured to condense the medium discharged from the expanders;
• a generator configured to be driven by one of the expanders to generate power;
• a control unit connected with the expanders;
• and
• a plurality of ports capable of communicating with the medium circuit;
• wherein:
• the medium circuit branches at a downstream side of the evaporator,
• each of the expanders corresponds to one of a plurality of branched pipes;
• the branched pipes join at a downstream side of the expanders and at an upstream side of the condenser;
• each of the branched pipes has a first on-off valve on the medium circuit at an upstream side of the corresponding expander, the first on-off valve being capable of shutting off flow of the medium through the medium circuit;
• each of the branched pipes has a second on-off valve on the medium circuit at a downstream side of the corresponding expander, the second on-off valve being capable of shutting off flow of the medium through the medium circuit;
• each of the ports has a third on-off valve, an end of each of the ports being connected to the corresponding branched pipe between the corresponding first on-off valve and the corresponding second on-off valve sandwiching the corresponding expander, and
• the control unit is configured to determine one maintenance target device to be maintained in accordance with an operation state of each of the expanders,
• the maintenance method comprising:
• closing the corresponding first on-off valve on the upstream side of the one maintenance target device and the corresponding second on-off valve on the downstream side of the one maintenance target device;
• opening the corresponding third on-off valve and recovering the medium between the corresponding first on-off valve and the corresponding second on-off valve after a medium recovery device that recovers the medium is connected to the corresponding port;
• closing the corresponding third on-off valve after a section between the corresponding first on-off valve and the corresponding second on-off valve is vacuumed after maintenance of the one maintenance target device is completed;
• and
• connecting a medium supply device that supplies the medium to the corresponding port, opening the corresponding third on-off valve, and filling the section between the corresponding first on-off valve and the corresponding second on-off valve with the medium from the medium supply device.