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http://pesn.com/2008/07/14/9501487_SHEC_labs_solar_thermal_record/
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SHEC Labs Claims to Have World's Most Efficient Solar Thermal Tech
By focusing the concentrated rays into the aperture of a highly-reflective, elongated
tube, by the time the light bounces back out, it has gradually dumped 95% of its heat
into the tube, which can then be put to work.
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Adapted by Sterling
D. Allan
Pure Energy Systems News
SASKATOON, SK, CANADA -- Solar Hydrogen Energy Corporation (SHEC) Labs claims to have developed the world's most efficient solar thermal
technology, developing a concentrator and complementary receiver technology that is able to concentrate sunlight to a very high level.
In their prototype, they concentrated sunlight up to 5,000 times the intensity
that normally would fall on a surface on earth.
This immense solar concentration can create heat at the focal point that approach the surface temperature of the sun at 6,000 ฐC (11,000 ฐF).
Metal placed at the focus is instantly melted. In commercial scale systems,
SHEC expects that the concentrations could be as high as 11,000 to 16,000 times the intensity of the sun.
In practice, the objective is to not let the receiver get that hot. This
is accomplished by continuously pulling off the heat into whatever the system is
designed to do.
Applications
One of the applications of technology will be power generation, such as via a
stirling engine or by steam and turbine. SHEC has singed an agreement for the pursuit and capitalization
for the
generation of a total of 3 gigawatts divided among six solar farms of 500 MW output
each, beginning overseas this year.
Other applications include process heating, district heating, water
distillation, synthesis gas (syn gas) production which can be used for the production of alternative fuels including hydrogen and other applications.
Thermal chemical reactions are one of SHEC Lab's specialties: using thermal heat to convert methane, such
as is collected off landfills, into hydrogen and syngas. The combined H
and syngas, also called "Hythaneฎ alternative fuel" (Ref.)
can be used in vehicles that run on
natural gas. SHEC is planing on implementing this technology on a landfill in Texas that will be able to fuel 5,000 fleet vehicles per
year from the 5 million kilograms of hydrogen per year, the equivalent of
5,000,000 gallons of gasoline. When fuel cell vehicles come out, it will
be able to refuel 10,000 fuel cell vehicle per year. Another plant further along in Regina, SK, Canada, will produce enough gas to
fuel 800 vehicles per year.
World Record
Tom Beck, President and CEO of SHEC Labs said: "In filing for patent protection, a review of the current state of the art must be
undertaken. It appears from our prior art review and from comments of others, that our solar thermal efficiency is the most efficient in the world."
SHEC says their technology has been very challenging to develop, taking the span of a decade to work out the details of the process and materials.
How it Works
In the solar concentrator world, there are typically three different methods of
focusing the sun's rays. One is a troth that focuses the sun's rays on a
tube passing through the length of the focal point. Another is a heliostat
in which mirrors on the ground focus the sun's rays up to a tower. The
third entails point focus, in which reflective surfaces focus the sun's light to
a point.
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It is this latter method that SHEC uses. They employ one-foot-square,
glass parabolic mirrors that they manufacture with their proprietary, highly
efficient "rapid drooping process", increasing throughput thirty-fold
with a low rejection rate. Several of these squares are then fastened to a
frame. The commercial array surface will be a 40 foot by 40 foot square
with a parabolic surface.
To harness this intense sunlight, SHEC has developed a solar receiver to absorb this energy without destruction.
The light enters the aperture of a long, cylindrical tube lined with a
highly-reflective coating. That might seem counter-intuitive, but what
happens is that as the light bounces back and forth down and then back up that
tube, 95% of the heat energy is gradually -- rather than suddenly -- absorbed by
the tube before the light bounces back out the aperture.
The materials and method for making this receiver tube are proprietary, but the
materials consist of natural, not exotic, elements.
There are also mirror losses. A typical back coated mirror, which is
what SHEC is presently using, looses 10%, but they may be implementing front
coat in the future. This would significantly improve mirror
efficiency, reducing the losses to between 3% and 5% only.
In the commercial unit, the receiver apparatus will be about the size of a
45-gallon drum, and the aperture and tube will be around four inches in
diameter.
This array will result in a 11,000-fold concentration of the sun's energy.
SHEC pulls the heat off of that tube to perform work.
Safety Considerations
If the heat was not pulled off, the system would rapidly self-destruct, so SHEC
has engineered a number of back-up and safety systems to ensure that if the
energy from the concentrated light is not being pulled off, then a shut-down
sequence commences to shut down the aperture and direct the mirrors away from
the receivers into empty air.
Also, during such emergencies, inert helium gas will be used to run through the
receiver to cool it. A glycol fluid will be run through the window of the
aperture to cool it.
The system will also be equipped with a 48-hour battery back-up.
Low Emissivity Loss
In the industry, the energy radiated back into the environment by the
concentrated solar receiver is called emissivity loss. The amount of energy radiated from an object increases by the power of four in relation to its temperature. For example, an object twice as hot has sixteen times the amount of emissivity loss. For applications operating at 850 ฐC (1,562 ฐF) for example, the emissivity loss becomes very high. This temperature is very useful for applications such as alternative fuel production and power generation.
Many solar concentrating systems lose a great deal of energy due to emissivity loss. SHEC's technology only has a 5% emissivity loss at this temperature. This low energy loss means more of the collected energy is available for an application for a given size of solar collector and thus improving the economics.
Cost
While the capitalization costs of a SHEC array will be greater than for a
fossil-fuel-based plant of comparable output, the operational costs are much
lower, not requiring fuel, for example. So the payback time is in the
region of five to fifteen years. Compare that to the 50 year amortization
schedule common for a hydroelectric plant, for example.
The primary bottleneck to bringing SHEC lab's technology forward has been
getting adequate funding, but that has begun to come into place for them, though
they are not where they would like to be.
About SHEC LABS
SHEC LABS is a research and development company now embarking on
commercialization. They are considered a world leader in providing solutions for the production of clean, renewable energy for the emerging alternative energy markets. SHEC LABS, founded in 1996, has developed technologies to more economically harness the power of the sun for applications in power generation, alternative fuel production including hydrogen, process heating and other applications.
They are listed in the New Energy Congress' Top
100 Energy Technologies listing.
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Page composed by Sterling
D. Allan July 13, 2008
Last updated August 09, 2008
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