The sun's energy can be used for more than just creating electricity. It is often used as hot water heating and house heating and has been for far longer than it has for electricity generation.
Hot Water Heating:
Usually consists of a holding tank, a solar collector and a means to circulate the water. Systems can be either direct or indirect.
The holding tank merely stores the water that has been / is being heated.
The solar collector is the bit that heats the water. Usually located on the roof of a house, there are a variety of different collector technologies. The standard for many years (and still in widespread use) has been flat plate collectors - a thin, rectangular box with a series of pipes running through it. The pipes heat up in the sun and are painted black for maximum heat absorption. The water runs through the hot pipes and is thus heated. More recently evacuated solar tube systems have been developed. These consist of a glass tube within another glass tube. All the air between the tubes is removed, creating a vacuum. This minimises heat loss to the surrounding environment. Within the inner tube is the fluid to absorb the suns radiated heat, which can cross a vacuum. Flat plate collectors tend to be a bit more efficient in full sun, but less efficient in cloudly or cold conditions.
Water circulation can either be achieved by convection or a pump. Convection is the phenomenon of hot water rising. This setup requires the holding tank to be above the collector. The water heated by the collector rises up to the tank, and the cold water sinks down.
Otherwise a low power pump is used to move the water through the system.
Heating your domestic hot water with the sun makes so much sense.
The sun can be used to heat a building (more than happens naturally in a normal structure) either by special building design (passive solar heating) or the use of solar collectors.
Passive solar heating is where a building is designed to 'capture' the sun's energy and heat. This is achieved by the use of special materials in floors and walls that store the suns heat. Also lots of windows facing the direction of the sun (south facing in the northern hemisphere and north facing in thr southern hemisphere).
A solar collector is used either to heat air passing through it and then into the house, or to heat a fluid which passes through pipes throughout the building (often under the floors) and thus heats.