I would suggest that the glass tubes might not work well for the home enthusiast. So far, I have seen them used two ways.
Just as carlb23 said there are vertical evacuated (vacuum) tube heat transfer glass cylinders. the priciple is that although water experiences a liquid/gas phase change (boils) at 212F at sea level, if you go to a higher altitude (lower air pressure/partial vacuum), it boils at a lower temp.
If the tube is 1/4 filled with liquid such as freon, the sun boils it into a gas that rises, taking heat with it. The tops of the vertical tubes are set inside a horizontal pipe run of water you want to heat. As the heat goes from the hot gas to the cooler water (through the glass to maintain vacuum), the freon condenses and runs back down to the bottom.
The other way I have seen glass tubes used for heat gathering is with the California desert SEGS steam/electric plant. Rows of trough collectors focus the sun onto horizontal black pipes filled with a flowing salt syrup.
This carries and stores heat to a heat storage tank, but since the temps get up to 900F (salt syrup is used so it wont boil) much heat was initially radiated out into the air and lost along the way. To insulate the hot pipes (as much as is possible), they were covered with glass tubes, and a vacuum maintained between the glass and the black pipe.
"Avoid clichés like the plague, they're old hat" -Steven Wright