The inside of the tube is coated with a material, typically copper, that absorbs the sun's rays and converts them into heat.
Solar vacuum tubes come in several types, each with its own unique design and performance characteristics. The most common types include:
- Heat pipe solar vacuum tubes - These are the most popular type of solar vacuum tube. They work by transferring heat through a liquid or gas-filled heat pipe that runs through the center of the vacuum tube. Heat pipe solar vacuum tubes are highly efficient and can generate high temperatures even in low-light conditions.
- U-tube solar vacuum tubes - These vacuum tubes have a U-shaped heat pipe, with one end exposed to sunlight and the other connected to a heat exchanger. They are more flexible and can be used in a variety of configurations.
- Direct-flow solar vacuum tubes - These vacuum tubes directly heat the water or fluid that flows through them. They are simple in design and are often used in smaller-scale applications.
- Passive solar vacuum tubes - These vacuum tubes use natural convection to circulate heated water or fluid through the system, eliminating the need for a pump. They are less efficient than other types but are easy to install and maintain.
When selecting a solar vacuum tube type, factors such as climate, available sunlight, and the desired output temperature should be considered. The choice of vacuum tube type will depend on the specific needs and requirements of the solar thermal system.
In general solar vacuum tubes are highly efficient at capturing and converting solar energy into heat, making them an ideal choice for solar thermal systems used in both residential and commercial settings. They perform exceptionally well in colder climates, where their vacuum insulation helps to maintain high levels of efficiency even in low-light conditions.