Based on what medical professionals are saying, regular shields aren’t going to protect you from normal aerosols. Social distancing is probably better for people coughing near you. And buying shields is only going to increase mortality for hospital workers.
Also, mild discomfort is a small price to pay compared to not infecting and killing people around you.
Shields have fairly promising results without fans. I cited some research to that effect above. The problem with the shield is that air flows around it, and that might be mitigated by fans blowing filtered air.
Social distancing is, axiomatically, not better for people coughing near me. If someone is coughing near me then social distancing has already failed. If I need to go to a grocery store, why shouldn't I consider wearing a shield?
Shields are made out of a sheet of plastic, which is not in short supply. If I needed to buy any it would not "increase the mortality for hospital workers".
Regarding mild discomfort being a small price to pay, you've misunderstood. The choice is not between mild discomfort and infecting people, but between mild discomfort and comfort. Obviously the latter is preferable, hence my curiosity about the shield and fans.
People wear PPE to protect them from specific things.
The specific thing you are protecting yourself from with Covid-19 is droplets that have been coughed from infected people into the air, and the droplets that then fall onto other surfaces.
So far we think these droplets are fairly large. There's a lot of talk in this thread about aerosolised, and that's tricky because there's no real definition of what that means. It's unlikely the drops caused by normal covid-19 coughing meet that definition though. So, these large drops don't travel far (maybe three metres), and they don't hang in the air for long before falling.
The most important thing you can do to protect yourself is stay at home. If you must travel outside you need to carefully and frequently wash your hands and maintain 2 metres distance from other people. Do not touch your face.
If you're doing that you'll get at best marginal protection from wearing PPE. But you only get that protection if you're wearing PPE correctly, and more importantly if you're taking it off correctly.
If you're not wearing PPE correctly you lose those marginal benefits. If you take it off incorrectly you not only lose the benefits but you increase your risk.
If PPE is causing you to take risky action, such as leaving your home when you'd otherwise stay in, then again you're increasing your risk.