More condensation may be due to low temperature surface by water cooling. Boiling of water can increase the productivity of a still, this can be done by using an auxiliary heat source.
In conventional solar distillers, the distillation is done on the inner face of the glass. To group all the water vapor in a copper spiral condenser for example, it is an impossible because you need the glass. So a party of the steam will be condensed by the glass and the other party will be condensed by the spiral condenser.
In multi-effect distillation it is possible. All the steam condenses via spiral condenser.