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Technology
Assessment |
Conventional simple
flat-plate solar collectors were developed for use in sunny and
warm climates. Their benefits are greatly reduced when conditions
become unfavorable during cold, cloudy and windy days.
Furthermore, weathering influences such as condensation and
moisture will cause early deterioration of internal materials
resulting in reduced performance and system failure. |
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Thermomax
Technology |
Thermomax Evacuated
Heat Pipe Solar Collectors (tubes) operate differently than the
other collectors available on the market. These solar collectors
consist of a heat pipe inside a vacuum sealed tube, as shown.
Each tube contains a
sealed cooper pipe (heat pipe). The pipe is then attached to a
black copper fin that fills the tube (absorber plate). Protruding
from the top of each tube is a metal tip attached to the sealed
pipe (condenser). These tubes are mounted, the metal tips up, into
a heat exchanger (manifold). As the sun shines on the black
surface of the fin, the alcohol is heated and hot vapor rises to
the top of the pipe. Water, or glycol, flows through the manifold
and picks up the heat from the tubes. The heated liquid circulates
through another heat exchanger and gives off its heat to water
that is stored in a solar storage tank. A Thermomax system is
simple to install and easy to expand. |
| Memotron |
In the newly developed
Memotron tube the maximum working temperature is controlled by
means of a memory metal spring which is positioned inside the
heat-pipe's condenser.
The memory metal is programmed to change its shape at a pre-set
temperature. This allows for the condenser fluid to be retained
inside the condenser. When the programmed temperature has been
achieved, the memory metal spring expands and pushes a plug
against the neck of the heat pipe blocking the return of the
condensed fluid and stopping heat transfer.
At temperatures below the maximum
programmed limit, the spring contracts allowing the condensed
fluid to return to the lower section of the heat pipe. It is than
evaporated due to the heat from from the absorber plate,
transferring thermal energy to the condenser. Thermomax's patented
Memotron tube is the state of the art technology and provides
complete safety through effective temperature control. |
| Shock
Absorber |
Thermomax system is
designed for all weather conditions. While the ambient temperature
is in sub-zero range, the condenser can experience super high
temperatures (300 F).
A patented flexible neck system absorbs both thermal and
mechanical shocks. |
Absorber
Coating |
Thermomax's sputtering
selective-coating surface has higher absorption (> 92 %) and
lower emittance (< 6 %) than traditional selective coating
surface. The sputtering selective-coating absorber is high
resistance to long-term vapor condensation, high corrosive sulfur
dioxide and high operating temperature. The effective resistance
measured in the test is equivalent to a product life span
exceeding 30 years.
The sputtering is a physical manufacturing process that involves
coating a substratum with metal particles. The manufacturing
process takes place in a high vacuum chamber and the coating
process involves three stages, stabilizing layer coating,
semi-conductor layer coating (radiation absorbent layer) and
anti-refection layer coating, as shown in the following diagram.
In the vacuum chamber three target plates are installed above
the copper fin. By creating a high-tension field between the
targets and the copper fin and a magnetic field parallel to the
target plates, positive helium ion release titanium atoms from the
target plate. The atoms strike the copper fin and because of high
kinetic energy of the atoms they attach themselves to the top of
the copper fin. During the process this copper fin passes three
targets plates.
First, a stabilizing layer of pure
titanium is laid on the copper fin. This layer gives the surface
of the copper fin long-term stability. Secondly, the titanium
atoms react with oxygen to form an absorbent layer of titanium
oxide (TINOx) on the first layer. In this semi-conductor layer
titanium atoms are orientated in such a way that 98% of incoming
solar radiation can be absorbed. Finally, an anti-reflection layer
is added on the absorbent layer. The anti-reflection layer has a
very low reflection index and can let 98 to 99 % of incident solar
radiation pass through the layer to be absorbed by the
semi-conductor layer. |
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Today |
Thermomax's advanced
evacuated "heat-pipe" solar collector is a breakthrough
in solar technology. It is an efficient and durable solar energy
system. It is effective throughout the year and saves its user a
considerable amount in expensive fuels. |
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Performance |
Thermomax's collector
performs not only at noon or on clear sunny days, but also when
the sun is low or the weather is cloudy. Wind or low temperatures
have less effect on its performance.
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Quality |
The high quality of
Thermomax products is the result of ongoing refinement and
optimization of the product process guided by Dr. Framarz
Mahdjuri. The quality and durability of Thermomax solar products
have contributed to an unequaled history of achievements in the
development and implementation of solar technology. This continues
a tradition of innovation begun over four decades ago when NASA
invented the Heat Pipe. Thermomax brings this superb space
technology to the market place as an economically competitive
option for Solar Energy. Our ISO
9001 & 9002 Quality Management Certifications
ensure that Thermomax quality systems meet the highest standard. |
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Heat Transfer |
Transfer of heat from
the absorber plate (collector) is via an efficient and very fast
heat conductor, the "heat-pipe." This has a very low
heat capacity but an exceptionally rapid conductivity. The
"heat-pipe" also provides the system with a diode
function. Due to the physical properties of the "heat-pipe,.
the maximum working temperature of the system is controlled. |
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Insulation |
The vacuum in the glass
tube, being the best possible insulation for a solar collector,
suppresses heat losses and also protects the absorber plate and
the "heat-pipe" from external adverse conditions. This
results in exceptional performance far superior to any other type
of solar collector. |
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Photo Thermal
Conversion Technology |
A solar collector
absorbs solar radiation and converts it into heat (photo-thermal
conversion). The high efficiency solar collector implies maximum
absorption of incident solar radiation with a minimum thermal and
optical loss. Selective coating characteristics of the absorber
and the vacuum insulation are the most important parts of an
advanced collector. A selective surface has high absorption (low
reflection) for the solar spectrum and low emissivity for the
infrared heat radiation. The selective coating used in the
collector consists of a very precise thin layer of an amorphous
semiconductor plated on to a metal substratum having a low
emission for long-wave radiation. |
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Vacuum
Technology |
Due to the atmospheric
pressure and the technical problems related to the sealing of the
collector casing, the construction of an evacuated flat-plate
collector is extremely difficult. To overcome the enormous
atmospheric pressure, many internal supports for the transparent
cover pane must be introduced. However, the problems of an
effective high vacuum system with reasonable production costs
remain so far unsolved.
It is more feasible to apply and adapt the mature technology
related to the lamp industries with proven mass production.
Building a tubular evacuated solar collector and the maintenance
of its high vacuum, similar to light bulbs and TV tubes, is
practical. The ideal vacuum insulation of the tubular evacuated
solar collector, obtained by means of a suitable exhausting
process, has to be maintained during the life of the device to
reduce the thermal losses through the internal gaseous atmosphere
(convection losses). |
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Heat Pipe
Technology |
A heat pipe acts like a
high conductance thermal conductor. Due to its thermal-physical
properties, its heat transfer rate is thousand's times greater
than that of the best solid heat conductor of the same dimensions.
The basic heat pipe is a closed container consisting of a
capillary wick structure and a small amount of vaporizable fluid.
The heat pipe employs an evaporating-condensing cycle, which
accepts heat from an external source, uses this heat to evaporate
the liquid (latent heat) and then releases latent heat by reverse
transformation (condensation) at a heat sink region. This process
is repeated continuously by a return feed mechanism of the
condensed fluid back to the heat zone.
In the solar collector, the condensation zone is at a higher level
than the evaporation zone. The transport medium condensed (in the
condensation zone) returns to the evaporation zone under the
influence of the gravity. Then, there is no need of capillary wick
structure.
The maximum operating temperature of a heat pipe is the critical
temperature of the used heat transfer medium. Since no
evaporation/condensation above the critical temperature is
possible, the thermodynamic cycle interrupts when the temperature
of the evaporator exceeds the critical temperature. |
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