low consumption

So I recently bought a UGREEN 3.5 enclosure with its own 12V 2A Power Adapter which supports up to 16TB capacity and a WD Blue 6TB 3.5 HDD to go along with it. Here is where the problem starts when I connect the enclosure to my laptop with it plugged into a power outlet and USB port my HDD...

I will soon start my bachelor degree in IT. Problem: I need a laptop that I can work with for many hours (6-8 hours during+after classes) that can be hooked to 2 Dell U2412M (when at home) and that can withstand a lot of work for at least 4 years: Uses: a) Moderate web-browsing with a bunch...