Mobile Off-Grid Solar Electrical & Water
Solar CPV Electrical Power and Water
Second Phoenix Astro-Solar Workshop

 - November 12, 2011
 - December 5, 2011 
 - October  13, 2012                  

Second Phoenix Astro-Solar Workshop
of the Mobile Solar Initiative 
Saturday October 13, 2012, 9:00 AM – 5:00 PM

Southwest Solar Technologies,
3545 S. 28th Street, Phoenix, Arizona 85040

 
Workshop Description

Mobile Off-Grid Solar CPV
Electrical Power and Water Purification Systems

Saturday, November 12, 2011 -- 10am-5pm
Sunday, November 13, 2011 – 10am-3pm

Presidio Graduate School
36 Lincoln Blvd at Graham Street
The Presidio, San Francisco, CA 94129

Click here for a pdf version of this wrap-up

Co-chairs: Dwight Collins (Presidio Graduate School) 
Russ Genet (California Polytechnic State University)
Kiran Shah (Chroma Energy Pvt.,Ltd., India)
Workshop Coordinator: Cheryl Genet (Collins Educational Foundation)
 

Workshop Agenda

 Saturday, November 12^th  Talks and Discussions

10:00 - 11:00     Welcome and Overviews

                            Presidio Graduate School Welcome                Dwight Collins
                            Attendee Introductions                                   All
                            Overview & Workshop Objectives                    Russ Genet/Dwight Collins
                            Solar Power                                                  Kiran Shah
                            Structural Analysis                                        Abe Lynn
                            Lightbucket Telescopes                                 Laura Rice

11:30 - 1:00       Background Tutorials

                            CPV Basics (20 min)                                      Kiran Shah
                            CPV Optical considerations (10 min)                Herb Hayden
                            Water Purification Basics (20 min)                   Tom Joseph
                            Flat Panel Mobile Systems (10 min)                 Travis Semmes
                            Small Business Considerations (15 min)           Dave Genet
                            Development & Commercialization (15 min)       Dariush Rafinejad

  1:00 - 2:00       Lunch (Compliments the Collins Educational Foundation)

  2:00 - 3:00       Working session:  Rapid Prototype Design          Kiran lead
  3:00 - 3:30       Working session:  Project Planning                    Russ lead
  4:00 - 4:30       Working session:  Sustainability/Business          Dwight Collins lead
  4:30 - 5:00       Wrap-up

 Sunday, November 13^th  Strawman Design Session

10:00 - 11:00     Discuss Requirements
11:00 - 12:00     Rough Out Major Parameters
  1:00 - 2:00       Develop Quantitative Spreadsheet
  2:00 - 3:00       Discuss and Record Economic and Production Considerations
 

The workshop was co-chaired, left to right by Kiran Shah, Russ Genet, and Dwight Collins.  Kiran, a mechanical engineer, came  from India where his company, Chroma Energy, is developing a tracking megawatt low cost concentrated solar power system that uses Fresnel lenses to concentrate the solar power. Kiran is also keenly interested in mobile solar power systems that use mirrors as the sunlight concentrator and triple junction solar cells to produce electricity.  The waste heat can potentially be used to purify water in a membrane distillation system.  Russ, an astronomer, has a special interest in “light bucket” telescopes.  These are non-imaging, light-concentrating telescopes with very low quality optics used for high speed photometry, spectroscopy, and other applications. The  similarity  of  these  low  cost, large portable telescopes to mobile solar power systems led to an interest in the latter.  Dwight, a consultant in supply chain optimization and sustainable business, is also an instructor at the Presidio Graduate School and President of the Collins Educational Foundation, which sponsored the workshop.  The mission of the Collins Educational Foundation is to provide leadership in humanity's efforts to live sustainably on Earth.

The workshop was well attended with about two dozen conferees from the Presidio Graduate School, California Polytechnic State University, Stanford University, the University of California, Berkeley, and industry. Students were well represented, coming from the Presidio, Stanford, and Cal Poly.
 

We were very pleased to hear two talks from Kiran  Shah, one an overview of solar power, and the other on the basics of con-centrated photovoltaic systems.  The efficiency of triple junction solar cells is currently approaching 50% and may go much higher. Only a few cells are required, as they can run at very high power levels.  Thus while they are more expensive per cell, if the mirror concentrator can be very low in cost, then the overall system cost can be reduced as compared to flat panel systems. For both mobile CPV power systems and light bucket telescopes, the key is low cost, lightweight, and environmentally rugged mirrors.

Cal Poly student Laura Rice (left) and Abe Lynn (one of Laura's instructors), described the structural design of the world’s largest portable telescope.  The design and prototyping of this telescope was coordinated by the Alt-Az Telescope Initiative working group. Laura and her team at Cal Poly (Mounir El Koussa and Mike Vickers), used the engineering techniques they had learned to design skyscrapers to design this very stiff yet low cost structure.

The bulk of the structure of the Alt-Az Initiative working group telescope was automatically CNC milled from sheets of high quality plywood, although in production aluminum sheet would be used.  Mike (left) and Mounir are shown standing beside the structure at the engineering “high bay” at Cal Poly, with Russ Genet, he project mentor on the right.

The mirror for this lightweight, low cost telescope has been made by Display and Optical Technologies Inc. (DOTI). Mike Itz, DOTI President gave a call-in talk that described the process they use to slump ordinary soda-lime plate glass into telescope mirrors. For telescopes, the plate glass is ground and polished on the top side, and then coated with aluminum in a vacuum chamber and overcoated with a clear layer of silicon oxide. For solar power mirrors, the same slumping process would be used, but the back side of the mirror would be silvered and sealed and no grinding or polishing would be required. Shown below is a “squarish” 2.4 meter mirror prior to having its back side silvered and overcoated.
 

Another approach to low cost mirrors has been pioneered by Lisa Brodhacker, an organic chemist at Lander University, and her students. One way to avoid expensive grinding, figuring, and polishing is to spin a liquid material in a container at a constant speed. The material will naturally assume a parabolic shape. If the material is an epoxy, it will harden while spinning and a mirror of the correct optical shape will have been formed without the expense of optical figuring.  Of course the devil is in the details. Lisa and her students and associates are able to produce very lightweight, low cost, large-aperture mirrors at a very small fraction of the cost of ground and polished glass parabolic mirrors
.

  

Lisa Brodhacker and one of her undergraduate student researchers hold a 25 inch spin-cast epoxy mirror (above).
The oven for spinning 2-meter mirrors is in the background.  A platter is supported by a very stiff air bearing. 
Oven panels with heating elements keep the epoxy at an elevated temperature while it sets to reduce shrinkage.
 

A very low cost alternative to the mirrors described above is the use of prime focus (on axis) satellite dishes.  Epiphany Solar Water Systems uses 2.4-meter dishes for their solar water distillation systems.  The segmented dishes are easy to ship and can be assembled on site. Optically reflective plastic inserts are added to the front surface of the dishes.  Although these systems do not also generate electricity, Epiphany envisions this as a future evolution of their systems.
 

Three of Epiphany Solar Water Systems 2.4-meter satellite dishes that have been converted for use as solar water purification systems.  Tom Joseph, President of Epiphany (below) explained how their low cost solar systems could provide clean water to many of he planets needy areas.    

During the afternoon talks, the Presidio Graduate School’s Academic Dean, Ed Quevedo, joined the conferees. Ed is trained as an attorney and has and extensive background in  sustainability law.

      

After the talks on Saturday, many of the conferees went to dinner at Capurro’s in Ghirardelli Square. Left to right: Cheryl Genet, David Genet, Tom Joseph, Kiran Shaw, Russ Genet, and Dwight Collins.

        

On Sunday, Kiran, Dwight, Dave, and Russ met to rough out a “strawman” design, including a discussion of production issues and a rough stab at production costs. Dwight and Dave work on some of the economic issues, using the whiteboard to sketch out ideas. 

      

Kiran modified his spreadsheet analysis system and took notes. After a few hours of discussion, the working group finally came up with a rough production costs of $5,000 for a 2.4 meter diameter mirror system that would produce 1 KW of electricity with hot water (or clean water) as a byproduct. 

Dwight wraps up the cost estimate.

A Promising Future 

As the price of fuel increases and the cost of triple-junction solar cells decrease, portable CPV solar power units could become increasingly attractive—especially as developments reduce the costs of mirrors and the support/tracking structures.  It might be noted that portable CPV units get a developmental “free ride” on the coattails of firms producing CPV triple-junction solar cells in the millions for huge megawatt power plants.  For instance, IBM is developing a solar cell that can handle a very high concentration factors.  It has the liquid heat exchanger built into the solar cell itself (Muller). 

One of the features being pursued in the development of portable light bucket telescopes is the ability to assemble the telescope from a compact package, much as mass produced furniture that requires “some assembly.”  We have purposely designed the structure of the Alt-Az working group telescope as a series of planar trusses that lay flat when disassembled for ease of shipment or storage.

If costs are driven low enough, portable CPV solar power units could become very widespread, even seeing use as off grid, fixed-location power units.  Ownership of these portable units could be decoupled from property ownership.  Units could be rented or leased out by small business entrepreneurs.  Governments or NGOs could loan units to off-grid villages for electric power and clean water.  Families could purchase units for their own use and take with them when they moved.

It is conceivable that portable CPV solar power units could  become a major source of power for the planet.  Not only would their adoption avoid the costs of power distribution systems, but it would also avoid centralized control.  Thus two of humanity’s most pressing needs—electrical power and clean water—could, in a way, become democratic. 

Solar CPV
Electrical Power & Water Purification Systems

Saturday December 3, 2011, 10:00 AM – 5:00 PM
Southwest Solar Technologies,
3545 S. 28th Street, Phoenix, Arizona 85040

 Co-chairs
Russ Genet, California Polytechnic State University
Herb Hayden, Southwest Solar Technologies

Click here for a pdf version of this wrap-up
 

Workshop Agenda

 10:00 - 11:00     Introductions and overviews

Welcome                                                          Herb Hayden, Southwest Solar Technologies
Attendee self introductions                                 All
Workshop Introduction                                       Russ Genet, California Polytechnic State University
Large CPV/clean water systems                         Herb Hayden, Southwest Solar Technologies 

11:00 - 11:30        Break and Tour of Southwest Solar Technologies

11:30 - 12:30    CPV solar power

Strawman mobile 2.4 meter system                   Dwight Collins, Collins Educational Foundation
A medium concentration CPV solar system        Alan Kost, University of Arizona
Evaluation of HCPV systems                             V. Lonij/A. Brooks, University of Arizona                                                                                                   

12:30 - 1:30          Group photograph in front of the 22 meter dish
                                On-site lunch provided by the workshop sponsors: Southwest Solar Technologies,
                                Mobile Solar Initiative, Collins Educational Foundation, and Blue Bottle Vending 

1:30- 3:30         Water purification

Solar driven water purification                             Wendell Ela, University of Arizona
Solar energy/water treatment scenarios for AZ     Ardeth Barnhart, University of Arizona
Evaluation of membrane distillation technology*   Kamalesh Sirkar, NJ Institute of Technology
Epiphany solar clean water systems                  Tom Joseph/Henry Wandrie


4:00 - 5:30        Astro-solar commonalities and low cost mirror technologies

Cherenkov radiation telescopes                          Dave Kieda, University of Utah
Stellar Intensity Interferometers                          Dave Kieda, University of Utah
SCOTS test for solar & telescope mirrors            Peng Su, University of Arizona
 

Workshop attendees (left to right): Dwight Collins, Paul Thomas, Dave Kieda, Russ Genet, Herb Hayden,
Alan Kost, Ardeth Barnhart, Dave Genet, Wendell Ela, Tim Wiese, Peng Su, and Colby Parker. 
The photo was taken by Russ Genet (Jr.), who also attended the workshop.
 

The Mobile Solar Initiative’s second workshop took place in Phoenix, just south of Sky Harbor Airport at the headquarters of Southwest Solar Technologies. A dozen folks attended the workshop. This workshop gave more emphasis to the “stellar-solar connection” than the San Francisco workshop, although the majority of the talks and discussion were about concentrated photovoltaic solar power systems and solar water purification.
 

Conference attendees stand at the base of Southwest Solar Technologies’ 22 meter, multiple mirror panel parabolic reflector. The reflector is pointed toward the ground and the square white screen on the boom just above the group was installed at the focal point for astronomical observations that night. Sadly, it remained cloudy so we were unable to make the observations, although we enjoyed our extended dinner J.

Seated far side of table from the left: Alan Kost, Herb Hayden, Dave Genet, Tim Wiese, and Colby Parker. 

Seated far side of table from the left: Peng Su, Dwight Collins, Russ Genet (Jr.), Ardeth Barnhart, and Dave Kieda. Russ (Sr.) took the pictures.
 

During a break period, we toured the shop facilities at Southwest Solar Technologies. Paul Thomas points to control
electronics, while Alan Kost, Peng Su, and Dwight Collins listen in. 

Ardeth and Dwight Collins (Presidio Graduate School) discuss the solar/membrane water distillation system at the Navajo Nation in northern Arizona.  While the orange juice membranes work okay, much higher efficiency membranes are being tested at the New Jersey Institute of Technology by Kamalesh Sikar, who gave a call-in briefing on these units manufactured by Advanced Membrane Technologies.
 

            Wendell Ela, University of Arizona (on the right), gave an overview of a number of water purification processes, with emphasis on distillation approaches, including membrane distillation. During the discussions, Dave Genet and Russ Genet (Jr.) described their firm, Blue Bottle Vending, which makes reverse osmosis water purification units.
            Dave Kieda, University of Utah, Chair of the Physics Department (on the left above), gave two astronomy talks, one on Cherenkov radiation telescopes and the other on stellar intensity interferometers. These two specialty areas within astronomy use large, low cost light collectors that are similar in many respects to the large (22 meter) concentrated solar power dish made by Herb Hayden et al at Southwest Solar Technologies. Dave wanted to know if Herb could make similar 22 meter dishes with tighter optical specifications. Herb thought this could be done.  Herb also suggested that a “small” dish with just a single row of panels might be useful as an 8 meter light bucket telescope.
            Solar intensity interferometry, an area originally pioneered by Hanbury Brown in Australia, is being revived by Dave and his colleagues at the University of Utah and is an area of keen interest to Russ (Sr.) and Bruce Holenstein (unable to attend). Back in the 1960’s and early 1970’s Hanbury Brown placed two 6.5 meter multiple mirror telescopes on a circular track 180 meters in diameter. These mobile telescopes, which were controlled by analog electronics, used photomultipliers as the detectors and analog electronics for signal correlation. They measured the quantum de-correlation of light versus telescope spacing. They provided the first direct measurements of the diameters of 32 nearby stars. Modern telescopes, very high speed solid-state detectors, and fast parallel digital correlators should allow multiple “light bucket” telescopes to provide images of the surfaces of nearby stars, as well as images of close and contact binary and multiple star systems.
 

Hanbury-Brown’s two famous “portable” light bucket telescopes in Narrabri, Australia, (above) exemplify the on-axis photon hunger of some dedicated science telescopes. Another area that requires an abundance of low cost photons is Cherenkov radiation telescopes. When gamma rays, emitted by highly energetic events in the cosmos, hit the top of the earth’s atmosphere, they create a shower of particles that, as they descend through the atmosphere, emit faint, blue, Cherenkov radiation. This radiation can be detected by an array of light bucket telescopes, such as the VERITAS pictured below at the base camp at Mt. Hopkins in southern Arizona where Dave Kieda and colleagues gather scientific data.