The image shows India’s first (19.04.1975) experimental indigenous satellite, covered in solar panels. A set of solar panels like this is called an array. Each solar panel has several solar modules and each solar module has many solar cells connected in series. If you connect two voltage sources in series, they behave like a single voltage source whose voltage is the sum of their voltages and whose internal resistance is the sum of their internal resistances.
A single silicon photo-voltaic cell generates about a half volt of electricity. If the conditions are right. So to make a 24 V Solar Panel, you would need (simplistically speaking) 48 solar cells. When solar cells are connected in series, the current through them has to be the same. So if one cell is producing less current because it is in the shade, then the current through both the cells is reduced. To get a general idea, your TV remote needs about 3V. So how many half-volt solar cells connected in series do you think will it need?
Image from: http://www.pveducation.org/pvcdrom/modules/mismatch-for-cells-connected-in-series