My question is: are there any penalties from search engine with this kind of situation?
No. Search engines do not penalise two identical sites - contrary to what you might have read elsewhere.
.. any effects on their ranking
Probably. Just because there is no penalty, that doesn't mean it's a sensible thing to do. At the very least, any incoming links will be split between the two sites, diluting any SEO benefits that the links bring with them - not to mention potentially confusing your customers and making more work for whoever maintains the sites.
Unless you've got a particularly good reason for keeping the two sites, I'd suggest you go with TechnoBear's recommendation: promote one of the sites, and redirect to that site from the other.