Dwarf beans?! What kind? I read that dwarf varieties of plants are very preferable. It's true, they still require lots of sunlight which is why I have them on a south facing window.
If you're going to extract the calcium from eggshells just make sure to dilute the resulting mixture in some water. It was my first time so I don't know how much is too much or if it might burn the plant. Use with caution!