The majority of people know little about evacuated tubes.
Evacuated tubes, or ETs, are extremely efficient heat absorbers surrounded by or contained within a vacuum of glass. The absorbed heat is transferred to a copper heat pipe, which in turn heats the water in your solar loop. Here are some cool facts about ETs that help explain why they are so efficient at harnessing the sun’s energy:
- The best insulator on the planet is a vacuum. While the heat pipe inside of an evacuated tube can easily reach temperatures above 250 F, the glass on the outside will always be cool to the touch. A thermal imaging camera captures this phenomenon perfectly, and can be seen below.
- The selective coating on heat absorbers within evacuated tubes absorb up to 95% of the available energy, while only releasing less than 6 percent.
- Only 0.1 percent of some tubes’ energy produced over its lifetime goes into making them. In other words, some evacuated tubes will produce 1000x the amount of energy required to manufacture them.
- Evacuated tubes go through rigorous durability testing. While they may look fragile, most ETs on the market can easily withstand golf ball size hail storms.