July 14, 2008
SHEC Labs Claims to Have World's Most Efficient Solar Thermal
Tech
Pure Energy Systems
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 °C (11,000 °F).
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 signed 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 Labs' specialties: using
thermal heat to convert methane, such as is collected off landfills,
into hydrogen and syngas. The combined H and syngas, also called
"Hythane® alternative fuel" 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.
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, loses 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 °C (1,562 °F) 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.
