Correction to an Assumption in Engineering Challenges for Developing the SunCell’s Concentrator Photovoltaic Cells and Geodesic Dome Array (Michael Lammert)

The following post has been submitted by Michael Lammert. It is a follow-up to this article that was published here yesterday.

Correction to an Assumption in Engineering Challenges for Developing the
SunCell’s Concentrator Photovoltaic Cells and Geodesic Dome Array

Michael Lammert (AKA Dr. Mike)

2/1/2017

     One of the assumptions that was made for the development of the Masimo CPV cells for the geodesic array Brilliant Light Power’s SunCell was pointed out to be incorrect by e-catworld reader “tip” in that large area CPV cells will not be used to form the geodesic dome array.  Masimo plans on building triangular array modules of series connected small cells, then connecting the triangular modules to form the geodesic dome, instead of developing large area, triangular CPV cells.  Masimo’s development plan can be found at: http://disq.us/url?url=http%3A%2F%2Fwww.brilliantlightpower.com%2Fwp-content%2Fuploads%2Fpresentations%2FMasimo-BrLPIndustryDay-102616.pdf%3ADVcN4biGAI-vuJwSlyEYgys0GHc&cuid=2168707

Masimo’s plan consists of:

  • Demonstrate the array module called TRU (Triangle Receiver Unit) using 209 single junction cells with dimensions of 0.267cm by 0.366cm.
  • Increase the CPV cell size to 0.389cm by 0.564cm (0.219cm2) and build single junction InAlGaAs on InP substrate cells to form modules that will output 15.5KW when configured in the geodesic dome array.
  • At this same cell size build double junction InAlGaAs on InP substrate cells to form modules that will output 28.5KW when configured in the geodesic dome array.
  • No plans are presented for the bifacial growth triple junction cells.

Without increasing the size of the CPV cells there should be no issues with fabricating the individual CPV cells, including no need to increase the metal thickness.   By series connecting a lot of small devices in a module, the output voltage of the module will be high and the current will be low (the output current of a single cell).  The only issues with building the geodesic dome array are acquiring the technology to build the “TRU” modules then developing the method to connect the modules to form the geodesic dome.  There may be some technology issues with the initial fabrication of the “TRU” modules, but these issues should be easy to resolve before moving to triple junction devices.  It should be noted that there is considerable loss of cell area fitting small cells into triangular modules.  The triangular modules have an area of 23.1cm2, whereas eighty 0.219cm2 cells have a total area of only 17.6cm2, or a ratio of 0.76 (and this doesn’t include the bus bar area loss).  I would conclude that BLP will have a CPV cell array available to integrate with the SunCell system within the first half of 2017 even if it is only a single junction based array that outputs 15.5KW.  There shouldn’t be much difficulty having the double junction array that will produce an output of 28.5KW available by the second half of 2017.

While the triple junction cell was not part of the presented development plan, I did some calculations to determine the expected output from triple junction CPV cells with these assumptions:

  1. The cell size is the same as for the prototype- 0.389cm by 0.564cm (0.219cm2)
  2. Although Masimo did not list the number of this size cell that would fit into their 23.1cm2 “TRU” module, I calculated 78-88 cells would fit, depending on the spacing between cells.  It will be assumed that 80 cells fit into the module.
  3. The maximum current density for the triple layer cell is the same as the BFG3-2BB-1010-A10 cell, about 16.1A/cm2.
  4. Based on the data from the Masimo presentation I’m not sure if the geodesic dome will be 40 modules (a hemisphere) or 60 modules (3/4 of a sphere).  I will still assume 60 modules.

The total output power can be calculated as:

Pout = 60 modules x 80 cells/module x 3V/cell x 16.1A/cm2 x 0.219 cm2 = 50,865KW

Note that he BFG3-2BB-1010-A10 cell has a spec of maximum solar concentration of 1200X or about 120W/cm2.  The triple junction CPV cells will be located at a position in the SunCell where the light intensity is about 125W/cm2.  Therefore, the array output may be 52-53KW, but the CPV cells may be running at a few percent above spec.  Bus bar areas were not included in this calculation so the actual output power may be a little less than 50KW and the true current density may be 10-15% higher than the spec for the BFG3-2BB-1010-A10 cell.  The only issue with the triple junction cell is that it requires a backside contact which means the modules will have to be modified to accommodate this contact.  There shouldn’t be any major difficulties demonstrating an output power of about 50KW with triple junction CPV cells.

To increase the blackbody radiation to 3500ºK modifications will need to be done to the triple junction cells, including doubling the metal thickness and modifying the semiconductor layers to raise the maximum current density to about 30A/cm2.  Assuming that the triple junction cell can be modified to handle higher current densities, the key issue will be verifying that the modified CPV cells are still reliable.

Conclusions

Masimo appears to have a good solution to avoid having to operate CPV cells at high currents and make high current connections in the geodesic dome array by building the geodesic domes of modules of small cells.  The only drawback to modules of small area cells is loss of 20-25% of the potential CPV cell area.  There should not be any major issues with the development plans for the CPV cells and arrays up to the point of increasing the operating temperature to 3500ºK and thereby about doubling the current density in the triple junction cells.  It may not be possible to improve the existing triple junction CPV cell sufficiently to operate it reliably at a factor of 2X higher current density.  The CPV cell geodesic dome array should not be a limiting factor in demonstrating a SunCell prototype.

 

 

 

 

 

 

 

 

 

 

 

  • fusionrudy

    Why not use rectangular PV modules and then fill the remaining (triangular) spots with shaped mirrors that reflect the light to the rectangular PV modules? This seems a lot easier from an engineering point of view than acrobatics with triangles.

    • Dr. Mike

      fusionrudy,
      If you look at the “TRU” triangular module being build by Masimo the module already has clips on the sides for building the geodesic dome. You would not be able to fasten together rectangular shaped PV modules. Also, I think it would be hard to fill the remaining triangles with mirrors that would reflect light uniformly over the rectangular cells. The loss of potential cell area with triangular modules is more than made up for with the ease of forming a geodesic dome out of the modules.
      Dr. Mike

  • fusionrudy

    Why not use rectangular PV modules and then fill the remaining (triangular) spots with shaped mirrors that reflect the light to the rectangular PV modules? This seems a lot easier from an engineering point of view than acrobatics with triangles.

    • Dr. Mike

      fusionrudy,
      If you look at the “TRU” triangular module being build by Masimo the module already has clips on the sides for building the geodesic dome. You would not be able to fasten together rectangular shaped PV modules. Also, I think it would be hard to fill the remaining triangles with mirrors that would reflect light uniformly over the rectangular cells. The loss of potential cell area with triangular modules is more than made up for with the ease of forming a geodesic dome out of the modules.
      Dr. Mike

  • That’s weird.
    You came up with some (well thought out but flawed) analysis and then, when the flaw was pointed out, you accepted this and changed your analysis accordingly rather than trying to fit a square peg into a round hole.
    But seriously, thanks for both articles. I believe Mills has something amazing but it is good to think things through critically.
    By the way, I believe the commenter is “tlp” not “tip” (with an “l” not an “i”).

    • Dr. Mike

      Tristan,
      I always try to state my assumptions so that when any assumption is found to be wrong, the analysis can be modified to correct things that are were found to be wrong. My apologies to “tlp” for not getting his/her name correct- I think I could use some new reading glasses for my computer work. I would also like to thank tlp for the link to the Masimo presentation as I would have never seen it without it being referenced in tlp’s comment.

      I also think that Mills has something that is potentially amazing- looking forward to the new developments this year.
      Dr. Mike

  • That’s weird.
    You came up with some (well thought out but flawed) analysis and then, when the flaw was pointed out, you accepted this and changed your analysis accordingly rather than trying to fit a square peg into a round hole.
    But seriously, thanks for both articles. I believe Mills has something amazing but it is good to think things through critically.
    By the way, I believe the commenter is “tlp” not “tip” (with an “l” not an “i”).

    • Dr. Mike

      Tristan,
      I always try to state my assumptions so that when any assumption is found to be wrong, the analysis can be modified to correct things that are were found to be wrong. My apologies to “tlp” for not getting his/her name correct- I think I could use some new reading glasses for my computer work. I would also like to thank tlp for the link to the Masimo presentation as I would have never seen it without it being referenced in tlp’s comment.

      I also think that Mills has something that is potentially amazing- looking forward to the new developments this year.
      Dr. Mike

      • tlp

        You should also watch this presentation, there is much additional information to those slides:
        https://www.youtube.com/watch?v=hQgZMC1VIwY&index=6&list=PLw1e-SwMe6eJf4Rr32w2UybIWOJ2cODEQ

        • Dr. Mike

          tlp,
          Thanks for the link to this video. I didn’t see much new in the video, but that was probably because I formed a good idea of Masimo’s plan from the slides. If I had been at the presentation, I would have asked Brad the following questions:
          1. What will it take besides better heat sinks to get a cell that will operate at 2X the light intensity of the 3000K blackbody emitter?
          2. What is the effect of the flange on the uniformity of the light intensity?
          3. Why would reflecting IR photons back to the source help the efficiency of the system when the light production at any output level is essentially free?
          4.What fraction of the area of the TRU module is covered by active cell area (with bus bar areas being considered inactive area)?
          5. How long would it take to get the triple junction CPV cell developed and what extra development work would be needed to incorporate this cell into the TRU module?
          6. How does the cost of the triple junction cells compare to the double junction cell?
          7. What reliability data do you have on the triple junction cell?
          8. Have triple junction cells ever been operated at >125W/cm2 for an extended period of time?
          Dr. Mike

          • tlp

            I can take number 3:
            Reflecting back those photons that cannot be converted to electricity reduces waste heat.

  • doug marker

    Dr Mike,
    An excellent and thoughtful analysis.

    Thanks

    Doug Marker

  • TOUSSAINT francois
  • TOUSSAINT francois
  • Val K

    I am not an LENR or hydrino energy adept. I am not even a physicist. I just recently bumped into the topic of hydrino energy and became curious. I watched the SunCell presentation on Youtube and get very excited about Mills’ GUT-CP and hydrino energy. However, something about SunCell does not make sense to me, so I would appreciate if somebody, who has more knowledge in physics and engineering and better understanding of how it all works, answer these questions.

    1. If temperature of the SunCell light-emitting sphere is 3000K, so the temperature inside the reaction chamber must be at least the same ore higher. However, from what I have seen on Youtube, the the entire Device including the reaction chamber was not designed to withstand such temperature. Can somebody explain me how the device can maintain its structural integrity and for how long, when such tremendous amount of heat is produced in the small volume?

    2. At first look, the liquid stream silver electrodes seem like a very elegant solution to cope with the problem of melting of the electrodes. However, how the liquid streams remain unbroken, with constant distance between streams and with the constant stream diameter (especially, when electric arc is formed between them)? How the molten silver remains liquid (which is crucial for recycling of silver) and does not evaporate? (According to Wikipedia, the boiling point of is 2435 K. At 3000 K it will never return back to the liquid state.)

    3. Using CPV cells sounds also as a smart idea. However, with the overall efficiency of ~21% (Massimo’s estimate for Geodesic Dense Receiver Array) or even less efficiency for Triangle Receiver Unit, the rest of the produced energy will end up as a heat. Thus, there should be a huge excess of heat , which should melt the CPV enclosure and the whole SunCell as well. There is no hints of how they are going to deal with this excess of heat. It is obvious, that introduction of any heat-exchange system inside the CPV enclosure would inevitably shadow the CPV cells resulting in further reduction of its overall efficiency. To me, the whole idea of using the CPV cells is just a sort of bells and whistles, which should attract the investors. Regular steam machine with the SunCell in its core would do the job, being much more efficient, more reliable, and cheaper (provided that SunCell works).

    I admit that my knowledge is very limited, so I would appreciate any clarifications on these issues.