while the idea of the solar staker looks good to me, I think that a single solar array powering multiple devices (including PCs) is much more convenient and efficient.
one PC consumes at least 400 W, so you need something like 2x 250w mono-crystalline solar panel, add the solar charger, the converter, and you easily pay at lest $500

There is no need for a full PC for a dedicated staking machine. There are other projects already doing this with a Pi running linux and a web gui for the user. You could add a small battery to a setup like this and the cost for all hardware would still remain very low.
http://www.voltaicsystems.com/blog/powering-a-raspberry-pi-from-solar-power/ The example here uses a 9 watt solar panel.
This seems like more of a fun hobby to do something like this over a product non -geeks may want to use. When the device only uses 5 volts of power in first place most people will not complain about that or look for alternative power solutions.
You are correct, this is not a solar powered PC and will be similar in functionality to the stated device.
We are doing everything we can think of to make this attractive to nontechnical people including those less familiar with crypto. This includes loading the device with an intial EGC deposit (for example, 100 EGC) so nontechnical people can start earning 7% by simply adding sunshine.