the power plant is a hybrid type device. it takes on the nature of aeroponics during its first weeks, as the nutrient mists are feeding the seed while it propagates. after the roots start finding their way into the reservoir the unit changes into a hydroponics system. the roots drink from the aerated nutrient.
wikipedia does a good job of explaining the details
one of the new lessons we learned is that the nutrient should be refreshed after 2 weeks or so, either dispose of the old or freshen up with some water / new nutrient mix...as the liquid level drops in the reservoir the concentrations of pH and chances of the nutrient strength increase, so we found that changing out with fresh nutrient / water helps keep the device running at an even keel.
when we were designing the device we learned a lot from actually trial and error. we built some crude jigs and contraptions and we read relevant texts and consulted experts in the field.
a favorite resource of ours is worms way. they have fun stores and a great catalog. i'm plugging them from a professional level, as i respect the enthusiasm they have for the growing system.
(most of the 'kit' they sell is crude and amateurish, but a huge amount of fun to put together...oh and home depot / Lendys our local hardware store, provided a lot more bits 'n pieces too.)