There are two main types of solar panels on the market, those based on electrical generation using photovoltaics and those that utilize thermal energy from sunlight to heat water that is piped to various locations. Since manufacturing silicon-based semiconductor material for photovoltaics takes sophisticated clean room technologies beyond home craftsmen, the best DIY solar panels are those of thermal heat design. Thermal solar panels can be designed to large scale and built from a variety of inexpensive materials, with many free plans for these types of DIY solar panels available on the Internet.
Thermal DIY solar panels or solar collectors don't produce electricity, so their uses are limited. They are most often employed on roofs of houses and buildings to heat water, which can be connected directly to the home water system, eliminating the need to heat water using natural gas or electricity. They are also often used as independent water systems to heat outdoor pools, and the heated water can be used in radiators inside a home to reduce typical home heating costs.
Solar collector-type DIY solar panels typically have a square or rectangular frame that is covered with a dark layer of plastic or glass that allows light to penetrate in short wavelengths, such as blue and yellow, and trap the less energetic red wavelengths that bounce off the interior, similar to how a greenhouse functions. Inside the housing, a piping system is mounted atop reflective material and uses standard polyvinyl chloride (PVC) pipe used in plumbing or steel or copper tubing, filled with water. The thermal heat from sunlight heats the water in the pipe, which can then be pumped to a pool to keep it warm during the day, or a home water system. The piping can also run past a fan or series of fans that can blow air against it, effectively heating a home. These systems can be custom made to suit desire and needs, with the amount of DIY solar energy captured and used directly proportional to how much square footage of sunlight is being collected and how quickly the water is circulated through the pipe.
Alternatively, photovoltaic panels can be assembled from smaller collections of pre-manufactured solar cells available for sale online. This first requires an investment in functional solar cells and electronic tools to interconnect them into larger power generating units. Small science experiment photovoltaic DIY solar panels can be made from common materials, such as oxidized copper sheeting and table salt, and instructions exist for doing this on the Internet. These handheld units usually produce very little electricity, in the quarter of a volt range or so, which is not even enough to power a small flashlight-size light bulb.