How to turn off display without closing the lid?

Here is the situation: I have MacBook Pro running on battery connected to the TV via HDMI. I'm using only the TV screen and I want to turn MacBook's display off, because it drains off a battery very much. I need to do that without closing the lid, because I'm using MacBook's trackpad and keyboard.

And there are two problems:

1. Using active corner function to send a monitor to sleep actually turns off HDMI output too.

2. Lowering brightness to the minimum level actually don't turn off rendering of display, so GPU unit still works on two screens – and battery is drained faster.