You don't feel in your day life, because sun rays are not focused in a point. Yet, it takes only 2 square meters of sun to melt every single known material that exists on earth...
vryazanov shows the first steps of his solar hexapod robot. The design is simple and it is still going only forward and for avoiding obstacles going backwards but thats coding issues. Vryazanov promises to continue, so check here for updates.
Uniflow builds a simple strirling engine driven by solar power provided by hdd platters. Dont judge low efficiency, have in mind we talk about Britain's sun. :)