Solar Thermal Energy Capture Tubes
evacuated tube consists of two glass tubes made from extremely
strong borosilicate glass. The outer tube is transparent allowing
light rays to pass through with minimal reflection. The inner
tube is coated with a special selective coating, which features
excellent solar radiation absorption when compared to conventional
flat plate collector systems. The top of the two tubes are
fused together and the air contained in the space between
the two layers of glass is pumped out while exposing the tube
to high temperatures. This "evacuation" of the gasses
forms a vacuum, which is an important factor in the performance
of the evacuated tubes.
pipe is inserted into the length of the tube. The heat pipes
contain a special fluid that allows solar radiation to be
absorbed and transferred to the stored hot water very efficiently.
Solar heat energy gets trapped inside, and cannot escape except
via the fluid…. air if you prefer. The solar heating
fluid is separate from the water to be heated and is connected
to the solar cylinder via a heat exchanger. The maximum temperature
reaches 250F-300 F+ in bright sunlight and each tube can boil
more than a pound of water per hour, but you would not want
to let steam actually form, so about 180 F maximum water delivery
temperature (determined by flow rate).
must be angled at a specific degree above horizontal so that
the process of vaporizing and condensing functions. There
are two types of collector connection to the solar circulation
system. Either the heat exchanger extends directly into the
manifold ("wet connection") or it is connected to
the manifold by a heat-conducting material ("dry connection").
A "dry connection" allows to exchange individual
tubes without emptying the entire system of its fluid.
tubes offer the advantage that they work efficiently with
high absorber temperatures and with low radiation. Higher
temperatures also may be obtained for applications such as
hot water heating, steam production, refrigeration, and air
conditioning. Evacuated tubes can still work efficiently even
on cloudy days, because it is able to absorb the energy from
infrared rays passed through clouds.
However, evacuated-tube collectors are more expensive than
flat-plate collectors, with unit area costs about twice that
of flat-plate collectors.
The collectors are usually made of parallel rows of transparent
glass tubes. The tubes are like a 4-foot long thermos bottle
with vacuum between two outer tubes. There is a purple looking
solar energy adsorption selective coating on the middle tube,
so solar heat energy gets trapped inside, and cannot escape
except VIA the water (or other working fluid…. air if
you prefer) flow in and around the center tube.
tubes mount on 4-inch centers and are 2 inches OD.
They are often combined with multiple tubes to form a solar
array. Combined with manifolds, this is an inexpensive way
to capture a lot of solar energy to make domestic hot water
or heat for the home.
Evacuated tube collectors work
even in the coldest climates!
solar capture tubes offered by Fossil Freedom were made by
Owings-Illinois Glass Company, for Sunpac.
are made of extremely strong borosilicate glass.
These cost Uncle Sam $250.00 per tube new.
These solar capture tubes were working well, when removed
from a large hot water system in order to add on to an existing
building. Each tube is re-tested before sale.
are not included, but we will provide plans for do-it yourself
manifolds, using standard plumbing fittings that can be found
at any good home improvement store, or we can provide tube-ready
manifolds at a very reasonable cost.
Now available at
the Fossil Freedom Store
Algae growth CO2 Aqualung