SEA Solar Thermal Technologies

1, Het Pipe and Vacuum glass tubes.

Vacuum tubes
All glass vacuum tubes are the key component of SEA solar collectors. The vacuum tube is similar to a conventional Dewar flask and consists of two borosilicate glass tubes, a glass with high chemical and thermal shock resistance. The outer side of the inner tube is coated with a sputtered solar selective surface. This coated inner tube is closed at one end and sealed at the other end to the outer tube.  The annular space between the outer tube and inner tube is evacuated to virtually eliminate heat loss by conduction and convection.

Working with several universities and partner companies, SEA’s R&D and manufacturing facility has successfully developed the innovative Advanced Solar Selective Coatings in commercial scale, which achieve high thermal efficiency and good thermal stability.  Solar selective coatings absorb most solar radiation while simultaneously suppressing the thermal emittance loss from coating surfaces. They vary mainly in their optical property and thermal stability.

Excellent results have been obtained by using DC magnetron sputtering technology.  A solar absorption of 0.94 - 0.96 with an emittance of 0.04 - 0.06 at 100 degree C has been achieved.

Vacuum insulation
SEA Groups tubes pull the best vacuum in the industry (meaning the space
within the glass tube contains no air). The better the vacuum within the tube, the
fewer molecules there are providing heat losses. The vacuum also safeguards
the collector against the effects of humidity and condensation. The lower the
heat losses of the tube, the higher the efficiency and the better the collector can
add heat to a hot system. SEA Groups collectors can add heat to a system
already at 60-80 ° C (140-176° F), making them also applicable for space
heating applications.

   

Vacuum tube features

  •  High solar-thermal conversion and low heat loss
  •  Stable advanced specific coating
  •  High stagnation temperature up to 300 °C (540 °F)
  •  Long working lifetime to over 15 years
  •  High level vacuums ensure operation in cold weather

Advanced solar selective coatings employ proprietary technologies:
(1) double cermet film structure with the highest photo-thermal efficiency
(2) metal-Aluminum/Copper nitride cermet (one kind of coating: AlN/AIN-SS/Cu) materials deposited by a novel sputtering technology

Heat Pipe

Heat pipes act like a low-resistance thermal conductor.  Due to their thermal-physical properties, their heat transfer rate is thousands of times greater than that of the best solid heat conductor of the same dimensions.

The Basic Performance of Heat Pipe
  • High Thermal Conductivity - Heat conductivity of heat pipe is much higher than the common metal.  Inside the heat pipe, it transfers heat by gas and liquid phase to change heat.  Heat resistance is very small, so the axial heat conductivity is very high, while the radial heat conductivity is general.
  • Good Isothermal Performance -    When heat pipe is working, the working fluid temperature inside it at saturation.  The saturated working fluid temperature is the same, but it will absorb or release more heat, therefore, the heat pipe can transfer more heat under isothermal circumstances.  Theoretically, whose outside behavior in the isothermal performance of heat pipe is very good.  The axial temperature of heat pipe is almost the same.
  • Reversibility of Heat Flow - A heat pipe with wick, if only the capillary force is enough, it will begin transfer heat, so that it makes the temperature of two ends tends to equal.
  • Thermo-diode - The heat pipe without wick like gravity-assisted heat pipe in solar water heater, in the absence of wick structure, the working fluid inside the pipe can just recycle by gravity, and the heat transferred from the bottom to the top and will not reverse so that get the heat loosed during night and winter.
  • Thermal Switches Property - When the heat pipe temperature is lower than the freezing point of working fluid, the heat pipe will stop working.  When the heat pipe temperature is higher than the critical temperature, the pipe is filled with steam, there is no phase change heat transfer process inside the pipe, heat pipe will stop working, therefore, the heat pipe working temperature is between the freezing point and critical point.
  • Variability of Heat Flow - Heat pipe can change the heat transfer area of the two ends
    independently, that is input heat through smaller heating area but output heat by larger cooling area, or vice versa; by doing this to change the heat flow density, resolve some difficult problem about heat transfer.

 

           

Vacuum tubes with heat pipe

Heat pipes are inserted into the aluminum absorbers forming assemblies, which in turn are inserted into the glass vacuum tube, which forms the normal vacuum tube with heat pipe.  The vacuum tubes are made of borosilicate glass that is strong and has a high transmittance for solar irradiation.  As described in the Vacuum tube section, the glass tubes are evacuated to vacuum pressure of <5x10-3 or 10-5 pa In order to reduce the convection heat loss.  

The heat pipe employs an evaporating-condensing cycle.  The evaporator section is tightly bonded to the absorber plate, where it captures the heat from the absorber and evaporates the liquid to steam, which moves up to the condenser section.  The condenser protrudes out from the evacuated tube and is inserted into the heat exchanger manifold.  There this steam will be condensed by water flowing through the manifold.  Latent heat energy will be released to the process water through this phase change of vapor to liquid.  In vacuum tube with heat pipe solar collectors, the condensation zone is at a higher level than the evaporation zone.  The transport medium condenses and returns to the evaporation zone under the influence of gravity.  This process is repeated continuously thereby heating the water in the solar loop.

The heat pipe vacuum tube provides the advantages from both the vacuum tube and the heat pipe to be a effective solar energy absorbing component.  The heat pipe vacuum tube successfully prevented from the defects of tube block and low power output caused by water fouling and deposits of mud dirt.   The vacuum tube with heat pipe is easy to install, just plug the heat pipe with the vacuum tube into the collector manifold, and it perfectly solves the common issue of the all-glass vacuum tube solar water heater, which cannot run if one of the tubes is broken.

2, Pressurized Storage Tank with Blue-diamond Coating.

Pressurized solar water storage tank

SEA pressurized solar hot water storage tanks are very efficient in terms of energy saving and storage, as well as their long lifetime.  Each tank is made of thick coated galvanized steel exterior and patent porcelain enamel coating liner (Golden Dark-Blue Diamond Coating).  Each tank is insulated with high density polyurethane for maximum heat retention.  Also available are heat exchanger collector loop for potable water.  The pressurized solar water tanks could be placed in series with the existing hot water heater that uses electric, gas, oil, or wood, (which now could be used as a backup heating system providing extra hot water storage capacity).  When the water temperature is up to 140°F, the existing water heater remains off.

Golden Blue-diamond Coating

At the heart of the water heater is a steel tank.   A porcelain enamel coating protects the tank against the corrosive effects of hot water.  The technology breakthrough Golden Dark-Blue Diamond coating formula is enriched with a higher level of zircon, producing a lining that is harder and more water-resistant than others in the industry.

The superior water resistance of Golden Dark-Blue Diamond Coating has been demonstrated in accelerated tests against glass lining samples taken from competitive water heaters. These tests determined water resistance by measuring the rate at which each glass lining sample dissolved over the 30-week test cycle.  The results (expressed in milligrams [mg] of weight loss per square inch of lining surface) are an indicator of how the glass lining will stand up to constant exposure to hot water.  The lowest mg/sq. in loss shows that Golden Dark-Blue Coating outlasts the best.

 

3, System Controller with Multifunction or Multisystem control capabilities.

Basic System Controller

Provide temperature difference control for one normal temperature application: water heating, pool heating, and space heating, etc. It also provides Collector Overheating Protection, Winter Season Frozen Protection-no anti-freezing liquid is needed, etc. functions that are critical for solar thermal applications.

Enhanced System Controller

Besides the basic solar thermal system control functions, the increased system controller will provide up to 7 devices' control or more than 22 different types of system configuration for multiple tanks/pools. It is also able to be controlled remotely through internet connection.

                  

 

4, Custom Developed Platform and Parts.

Heat Exchange Platform for Commercial and Residential Solar Application

Professional designed heat exchange platform providing a well engineering component that ease the installation for solar thermal applications, especially for those large commercial systems.

          

Circulating Pumps with Various Capabilities

Circulating pump is one of the most important parts in solar thermal applications, SEA has been developing efficient stainless and bronze circulating pumps meeting the needs.