The sun is the driving force for almost all natural phenomena on Earth, and is the driving force for many other renewable technologies. The sun heats air causing it to rise and flow, creating wind currents. By evaporating water and inducing the water cycle, rivers and surface water can continue to flow. The sun’s energy is the reason why wind turbines, hydroelectric dams, and many other technologies can function. On top of supplying energy for these processes, the energy of the sun can be used for heating and electricity generation.

Passive solar

Passive solar systems rely on the direct use of heat from the sun. Everyone has probably used solar passively without realizing it by hanging clothes out to dry on a line, or keeping blinds open on a sunny winter day to heat the inside of a building. By taking that second idea and design a building around it, a passive solar home may be achieved. These highly energy efficient buildings have large south or southwest facing windows (or north-facing, if the building is located in the southern hemisphere) that allow sunlight to heat up a room. These homes typically feature a thermal mass — a large object that can absorb and retain heat during the day, and release it slowly during the evening as the temperatures drop. A classic example of a thermal mass is a concrete floor. For those considering building a new house, a passive solar home will help keep energy bills down throughout its lifespan.

Active space heating

Active space heating requires solar collectors to be installed on a building’s roof, or a nearby sunny location. These collectors are usually reflective black boxes (comparable in size to solar panels) containing black-painted piping. A fluid is pumped through this piping where it can be heated by the sun, before being brought inside to provide heat. An example of one of these fluids is air, which can be transported throughout a building using fans. Another option is to heat a liquid such as water or refrigerant in the collectors, and store them in a tank. The heat from this tank may be integrated into an existing furnace system.

Solar water heating

The process for solar water heating is quite similar to that for active space heating. Inside the solar collectors, water is heated by the sun before being transported to a water storage tank. Since hot water is less dense than cold water, the heated water will rise to the top of the storage tank where it can be removed for use. The cold water at the bottom of the storage tank can then be pumped through the solar collectors to heat it up. Solar water heating systems are often used in conjunction with other water heaters. This pairing helps to relieve the load on conventional water heating methods, and ensures that there is always warm water when it is needed. Solar water heating for outdoor swimming pools is another common application for this technology.

Solar photovoltaic

Solar photovoltaic (PV) cells are used to generate electricity from the sun’s energy, and are typically what people think about when they hear of solar-powered renewables. Thin sheets of crystalline silicon are layered to create a single solar PV cell, and a collection of cells can be used to create a single solar panel. A solar array is a group of solar PV panels. As sunlight strikes the PV cells, the light energy causes the silicon to release electrons. The release and subsequent flow of electrons creates useable electricity. Variations on the crystalline silicon structures in PV cells can be used to improve efficiency or lower ecological impact during manufacturing. PV systems can generate electricity whenever the light striking them provides significant energy, which allows for electricity generation even on cloudy days.