Solar energy, or energy derived from sunlight, can be converted to electricity and used for a wide variety of different purposes. The most common solar energy applications include powering and optimizing the heating and cooling of houses, providing good conditions for plant growth, and providing cost-effective indoor sunlight. In some cases, solar energy can be useful for heating and lighting without the need for conversion to electricity. Solar energy applications of this type are useful because they cut down the need for using electricity and are, therefore, often quite cost effective. While converting solar energy to electricity provides a source of clean, renewable energy that can be used for just about any purpose, the cost of setting up the equipment necessary for gathering, converting, and storing the electricity is quite high.
Many of the most common, useful, and cost-effective solar energy applications are passive in nature and involve no conversion to electricity. Many houses, for instance, are built with the position of the sun at various times throughout the day in mind, ensuring that the house has plenty of natural lighting. Various architectural considerations can also ensure that buildings remain at reasonable temperatures. Another of the common applications of this form can be seen in greenhouses. The sun passes through the transparent enclosure of the greenhouse and heats the plants and soil, creating warm air that cannot escape from the enclosure and therefore providing a good environment for plant growth.
Some solar energy applications do require the conversion of sunlight to electricity. Some houses in isolated but well-lit areas, for instance, use solar energy to provide enough electricity for basic tasks. Though setting up a solar electricity system can be expensive, it may, over time, be more cost effective than connecting a building in an isolated area to a power system. The electricity from such solar energy systems can be used just like any other electricity, but it is often necessary to conserve it and use it only for the bare essentials. Such a system may not be able to power a full range of electrical appliances over a long period of time.
Some solar energy applications involve individual devices that have their own built-in solar panels. Many forms of outdoor lighting, for instance, collect solar energy during the day and use the collected energy to provide light during the night. Similar solar energy applications include solar refrigerators and small-scale solar electrical generators.