Courtyard

[maru]

is it possible to have strong shadows using this method?

You can prepare an empty scene with Corona sun+sky, do a panoramic render and save it as .hdr. Then use the saved image as hdr background. There should be no visual difference between using this hdr enviro and a sun+sky setup. :)

[Freakaz]

change the gamma of HDRI to 0.75-0.85 to get sharper stronger shadows, and use the "sunny" hdri not the "overcast" one ;)