How can I create a circuit to poer up pc each 24 hours?
You probably don't need to build a circuit and judging by your question you don't want to be building one for mains circuits. Most modern operating systems support wake up from sleep or hibernation on schedule. This should work for you if saving power is your primary goal.

Windows: use Task Scheduler.
Mac OS: System Preferences | Apple menu | System Preferences | Energy Saver icon in the System Preferences window ...
Linux: rtcwake.

The Windows Task Scheduler help file says:

Power Conditions
You can set a condition that tells the task to run only if the computer is on AC power (not battery power) when the task trigger is activated. If this condition is set, you can also set a condition to stop the task if the computer switches to battery power. If both of these conditions are set for a task, then you have ensured that the task will only run when the computer is on AC power.
You can also set a condition that tells the task to wake the computer from sleep mode to run the task when the trigger is activated. Before you set the condition to wake the computer to run the task, ensure that the task will not cause the computer to wake at inconvenient times.
Note
When the Task Scheduler service wakes, the computer to run a task, the screen may remain off even though the computer is no longer in the sleep or hibernate mode. The screen will turn on when Windows detects that a user has returned to use the computer.

See HowtoGeek for details.