Solar power is the conversion of sunlight into electricity. Sunlight can be converted directly into electricity using photovoltaics (PV), or indirectly with concentrated solar power (CSP), which normally focuses the sun’s energy to boil water which is then used to provide power, and other technologies, such as the sterling engine dishes which use a sterling cycle engine to power a generator. Photovoltaicscan be used to power small and medium-sized applications, from a calculator powered by a single solar cell to off-grid homes powered by a photovoltaic array.
The only significant problem with solar power is installation cost. But, the survivalist generally employs solar because grid electricity is not available at all, so paying a bit more up front is often considered to be a reasonable trade off.
Aside from capturing energy from the sun, one must also concoct a solution for storing the captured energy that one doesn’t immediately use. With current technology, energy storage is usually achieved by using an array of deep cycle batteries of some kind. It would also behoove the prepper to consider back-up power supplies such as generators that run on some kind of oil or gas in case emergency power is needed when batteries are drained and no sunlight is available or is blocked somehow.